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HomeMy WebLinkAboutCT 13-03; ROBERTSON RANCH- RANCHO COSTERA; AS GRADED REPORTS OF ROUGH GRADING; 2016-03-24LGC Valley, Inc. Geotechnical Consulting AS-GRADED REPORT OF ROUGH-GRADING, LOTS 82-8 7, 92-99, 105-110, 115-121, 212-215, AND 225-233, PLANNING AREAS PA-3 AND PA-6, ROBERTSON -RANCH, CARLSBAD TRACT NO.13-03, CARLSBAD, CALIFORNIA Project No. 133023-03 Dated: March 24, 2016 Prepared For: Toll Brothers 725 Town and Country Road, Suite 200 Orange, California 92868 2420 Grand Avenue, Suite F2 • Vista • CA 92081 (760) 599-7000 • Fax (760) 599-7007 LGC Valley, Inc. Geotechnical Consulting March 24, 2016 Ms. JoAnn Epstine Toll Brothers 725 Town and Country Road, Suite 500 Orange, California 92868 ProjectNo. 133023-03 Subject: As-Graded Report of Rough Grading, Lots 82 through 87, 92 through 99, 105 through 110, 115 through 121, 212 through 215 and 226 through 233, Planning Areas PA-3 and PA-6, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California In accordance with the request and authorization of Toll Brothers, LGC Valley, Inc. (LGC) has provided geotechnical services during the rough-grading operations for Lots 82 through 87, 92 through 99, 105 through 110, and 115 through 121 within Planning Area PA-3 and Lots 212 through 215 and 226 through 233 within Planning Area PA-6; part of the Robertson Ranch project (Carlsbad Tract No. 13-03) located within the City of Carlsbad, California. The accompanying as-graded report of rough-grading summarizes our observations, field and laboratory test results, and the geotechnical conditions encountered during grading of the subject lots. The rough-grading operations for the subject lots were performed in general accordance with previously published project geotechnical reports (Appendix A), geotechnical recommendations made during the course of grading, and the City of Carlsbad grading requirements. It is our professional opinion that the subject lots are suitable for the intended use provided the recommendations included herein and in the project geotechnical reports are incorporated into the fine-grading, design, and construction of the proposed development and associated improvements. As of the date of this report, the rough-grading operations for the subject lots are essentially complete. If you have any questions regarding our report, please contact this office. We appreciate this opportunity to be of service. Respectfully Submitted, LGC Valley, Inc. Randall Wagner, CEG 1612 Senior Project Geologist MRS/RKW/BIH O4AL No. 1612 .c' - 0. CER1RO * CN(NEpIHG GEOLOGIST E(P r) HA (1f(No. 27 Basil Hattar, GE 2734 SODMO Principal Engineer Distribution: (1) Addressee (via e-mail) (1) Toll Brothers; Attention Mr. Marco Meza-Ruiz (via e-mail) (1) Toll Brothers; Attention Mr. Kevin Brickley (via e-mail) 2420 Grand Avenue, Suite F2 • Vista • CA 92081 • (760) 599-7000 • Fax (760) 599-7007 TABLE OF CONTENTS Section Page 1.0 INTRODUCTION 2.0 SUMMARY OF ROUGH-GRADING OPERATIONS.................................................................................2 2.1 As-Graded Conditions.......................................................................................................................2 2.2 Site Preparation and Removals.........................................................................................................3 2.3 Stability Fills.....................................................................................................................................3 2.4 Subdrain Installation ......................................................................................................................... 4 2.5 Overexcavation of Cut/Fill Transition Conditions ............................................................................4 2.6 Cut Lots and Overexcavation of Proposed Cut Lots..........................................................................4 2.7 Fill Placement and Compaction........................................................................................................4 2.8 Laboratory Testing............................................................................................................................5 2.9 Field Density Testing........................................................................................................................5 2.10 Graded Slopes...................................................................................................................................5 3.0 CONCLUSIONS...........................................................................................................................................6 3.1 General.............................................................................................................................................6 3.2 Summary of Conclusions..................................................................................................................6 4.0 RECOMMENDATIONS..............................................................................................................................8 4.1 Earthwork.........................................................................................................................................8 4.2 Site Preparation ...............................................................................................................................8 4.3 Excavations ......................................................................................................................................8 4.4 Fill Placement and Compaction.......................................................................................................9 4.5 Preliminary Foundation Recommendations ....................................................................................9 4.6 Control of Surface Water and Drainage........................................................................................10 5.0 LIMITATIONS ........................................................................................................................................... 11 Appendices Appendix A - References Appendix B - Laboratory Testing Procedures and Test Results Project No. 133023-03 Page i March 24, 2016 1.0 INTRODUCTION In accordance with the request and authorization of Toll Brothers, LGC Valley, Inc. (LGC) has provided geotechnical services during the rough-grading operations of Planning Areas PA-3 and PA-6; part of the Robertson Ranch project (Carlsbad Tract No. 13-03) located within the City of Carlsbad, California. This as- graded report summarizes our observations, field and laboratory test results, and the geotechnical conditions encountered during grading of the subject lots. The subject rough-grading operations were performed in general accordance with previously published project geotechnical reports (Appendix A), geotechnical recommendations made during the course of grading, and the City of Carlsbad grading requirements. As of this date, the rough-grading operations for the subject lots are essentially complete. The Rough Grading Plans for the Robertson Ranch project, prepared by O'Day Consultants (O'Day, 2014b), were utilized as a base map to present the as-graded geotechnical conditions and approximate locations of the field density tests. The As-graded Geotechnical Map and the Field Density Test Location Map will be provided in the final as-graded report for Robertson Ranch upon completion of all of the rough-grading operations. Lots 82 through 87, 92 through 99, 105 through 110 and 115 through 121 of Planning Area PA-3 are located in the western portion of Robertson Ranch on both sides of Robertson Road and the cul-de-sac of Nelson Court while Lots 212 through 215 and 226 through 233 of Planning Area PA-6 are located in the central portion of the project along both sides of Wadsworth Street. Ultimately, development of Planning Area PA-3 and PA-6-will include the construction of 87 single-family residential lots in each of the planning areas; along with associated retaining walls, slopes, storm water retention basins, and adjacent streets. The rough- grading operations for the subject lots were performed as a part of grading operations for the entire Robertson Ranch Development between September 2014 and January 2016. Project No. 133023-03 Page] March 24, 2016 2.0 SUMMARY OF ROUGH-GRADING OPERATIONS Rough-grading of the subject site began on September 5, 2014 and was essentially completed as of January 15, 2016. The grading operations were performed under the observation and testing services of LGC Valley, Inc. Our field technicians were onsite on a full-time basis during the grading operations while our field geologist was onsite on a periodic basis. The rough-grading operations included: Removal and off-site disposal of vegetation and miscellaneous debris; The removal of potentially compressible soils including colluvium, topsoil, undocumented fill, and weathered soils to competent formational material; Overexcavation of cut/fill transition conditions within the lots; Overexcavation of buried cut/fill transition conditions such that the resulting fill differential beneath the proposed building pads was less than a 3:1 (maximum fill thickness to the minimum fill thickness); Overexcavation of cut lots due to expansive soils and/or due to very dense cemented sandstone; Preparation of areas to receive fill; The placement of a subdrain along the heel of the stability fill key; Excavation of formational material; and The placement of compacted fill soils creating the graded pads and adjacent slopes. The rough-grading operations consisted of the placement of fill up to approximately 45 feet in depth and cuts up to approximately 40 feet within the subject lots. During the rough-grading operations, remedial grading was also performed so that the fill differentials beneath the proposed building pads were less than a 3:1 (maximum fill thickness to the minimum fill thickness). 2.1 As-Graded Conditions The as-graded conditions encountered during grading of the lots were essentially as anticipated. In the vicinity of all of the subject lots, formational material was encountered at the design cut grade below a thin veneer of topsoil, colluvium, and weathered soils. All unsuitable and potentially compressible soils were removed prior to fill placement. This included topsoil, colluvium, undocumented fill (associated with the past agricultural operations), and weathered formational materials. The colluvium and topsoil typically consisted of light brown to brown silty fine sands, sandy clays and clayey sands derived from on-site soils and were found to be very low to highly expansive, porous, and contained scattered organics.. Removals of the topsoil, colluvium, and weathered formational material on the order of 2 to 6 feet were made during the grading operations. The formational material encountered on the subject lots consisted of the Santiago Formation. The material was found to be massively bedded to cross-bedded silty sandstones and minor clayey sandstones, silty claystones and sandy siltstones. The claystones and siltstones generally were olive green and orange brown, damp to moist, stiff to hard, moderately fractured and sheared. The Project No. 133023-03 Page 2 March 24, 2016 sandstone generally consisted of light olive green, light brown and pale orange brown (where iron- oxidized stained), damp to moist, dense to very dense, silty very fine to medium grained sandstone. The majority of the Santiago material encountered within Robertson Ranch consisted of silty fine sands. Bedding within the Santiago Formation was highly variable, but overall, generally dipped 2 to 15 degrees to the west-southwest. A minor inactive fault was mapped along the rear of Lots 212 through 215 located in PA-6. Geologic mapping indicated the fault trended N5°E to Ni 5°E steeply dipping 60 to 80 degrees to the west. The fault was only observed within the Santiago Formation and the fault appeared to die out to the south. Based on our geologic analysis during the current grading operations and review of the applicable geotechnical reports referenced in Appendix A, it is our professional opinion that the fault is not active; and therefore are not a constraint to development. No groundwater was encountered during the grading of the subject lots. However, unanticipated seepage conditions may occur after the completion of grading and establishment of site irrigation and landscaping. If these conditions should occur, steps to mitigate the seepage should be made on a case-by-case basis. 2.2 Site Preparation and Removals Prior to grading, the site was cleared of light vegetation and other miscellaneous debris and the material was disposed of at an offsite facility. Undocumented fill, topsoil, alluvium, colluvium, and weathered formational material were removed down to competent material (i.e. dense unweathered formational material). Remedial removals on site, below the existing ground surface, ranged from approximately 2 to 6 feet in depth. The thickness of compacted fills placed during this recent rough- grading operation, to achieve design rough grades ranged from 0 to approximately 45 feet. Following the remedial removals or overexcavations, areas to receive fill were scarified approximately 6-inches, moisture-conditioned, as needed, to obtain a near-optimum moisture content and compacted to a minimum 90 percent relative compaction (for fills of approximately 40 feet or less from design grades) or 93 percent relative compaction (for engineered fill below approximately 40 feet from design finish grades), as determined by ASTM Test Method D6938 (i.e. the nuclear gauge method). 2.3 Stability Fills A stability fill was constructed to stabilize the exposed blocky claystone/siltstone and/or adverse (i.e. out-of-slope) geologic conditions present within the Santiago Formation. The stability fill key was excavated to a width of approximately 15 feet and a minimum depth of 3 to 5 feet below the toe-of- slope. The keyway bottom was angled at least 2 percent into-the-slope._The stability fill front cut was excavated near vertical while the back-cuts were excavated at an approximate 1:1 (horizontal to vertical) slope inclinations. A stability fill was excavated along the slope on the west side of Lots 212 through 215. Project No. 133023-03 Page 3 March 24, 2016 2.4 Subdrain Installation The stability fill subdrain was installed under the observation of a representative of LGC in general accordance with the planned location of the approved geoteclmical report, and the standard details (LGC, 2014a). The stability fill subdrain consisted of a 4-inch diameter perforated pipe surrounded by a minimum of 3-cubic feet (per linear foot) of clean 3/4-inch gravel wrapped in Mirafi 140N filter fabric. The stability fill subdrain was placed with a minimum 1-percent fall (2-percent or greater where possible) to a suitable outlet location. The location of the subdrain placed during the mass grading operations for the project were surveyed by the project civil engineer. 2.5 Overexcavation of Cut/Fill Transition Conditions Based on the as-graded conditions, cut/fill transition conditions were present within Lots 82 and 226 through 233. These lots were overexcavated a minimum of 5 feet in depth beneath the proposed finish grade surface of the lot. The overexcavation extended to a distance of at least 10 feet outside the planned building limits. During the rough-grading operations, remedial grading was also performed so that the fill differential beneath the proposed building pads was less than a 3:1 (maximum fill thickness to the minimum fill thickness). 2.6 Cut Lots and Overexcavation of Proposed Cut Lots Lots 83 through 87, 92 through 99, 105 through 110, 115 through 121, and 212 through 215 were proposed cut lots composed of competent formational material. However, during the rough-grading operations, the overexcavation of some of the proposed cut lots was performed in order to mitigate potential adverse conditions due to expansive soils or in some cases, cemented sandstone conditions within the formational material exposed at finish grade. Lots consisting of expansive soils or cemented sandstone at or near the finish grade elevation were overexcavated a minimum of 5 feet below finish pad grade and replaced with compacted fill having a very low to medium expansion potential. In order to minimize potential ponded ground water conditions on the overexcavation bottoms, the excavations were sloped toward the street with a minimum fall of one percent. Cut lots that were overexcavated to mitigate expansive soils included Lots 83 through 87, 92 through 99, 105 through 110, and 115 through 121. Lots 212 and 213 were overexcavated due to the afore-mentioned cemented sandstone beds. 2.7 Fill Placement and Compaction After processing the areas to receive fill, native soil was generally spread in approximately 8-inch loose lifts, moisture-conditioned as needed to attain near-optimum moisture content, and compacted to at least 90 or 93 percent of the maximum dry density determined in accordance with ASTM Test Method D1557. Fill soils less than 40 feet below the design fmish grades were compacted to a minimum 90 percent relative compaction while fill soils greater than 40 feet below the design finish grades were compacted to a minimum 93 percent relative compaction. Compaction was achieved by Project No. 133023-03 Page 4 March 24, 2016 use of heavy-duty construction equipment. Areas of fill in which either field density tests indicated less than 90 or 93 percent relative compaction or the soils exhibited nonuniformity and/or showed an inadequate or excessive moisture content, were reworked, recompacted, and retested until a minimum 90 or 93 percent relative compaction and near-optimum moisture content was achieved. 2.8 Laboratory Testin2 Maximum dry density tests of representative on-site soils were performed (by others during the previous investigation and by LGC during the current rough-grading operations) in general accordance with ASTM Test Method D1557. Expansion potential, soluble sulfate content, and corrosion testing of representative finish grade soils within the subject lots were performed. Based on the laboratory testing: 1) Lots 115 through 121 have a medium expansion potential; 2) Lots 82 through 87, 92 through 99, 105 through 110, 214 and 215 have a low expansion potential; and 3) Lots 212, 213 and 226 through 233 have a very low expansion potential. Laboratory testing also indicated that the near surface soils have a negligible soluble sulfate content; are corrosive to severely corrosive to buried metals based on the minimum soil resistivity values; and are corrosive to buried metals and reinforcing steel in concrete based on the chloride concentrations. The laboratory test results are presented in Appendix B. 2.9 Field Density Testing Field density testing was performed using the Nuclear-Gauge Method (ASTM Test Method D6938). The approximate test locations and the results of the field density tests will be provided in the final as-graded report for Robertson Ranch upon completion of the rough grading operations. The field density testing was performed in general accordance with the applicable ASTM standards and the current standard of care in the industry. In-situ soil density testing is intended to verify the effectiveness of the earthmoving operation in general and is performed on a spot-check basis; as such, some variations in relative compaction should be expected from the results documented herein. 2.10 Graded Slopes Manufactured fill slopes within the subject lots were surveyed by the civil engineer and constructed with slope inclinations of 2:1 (horizontal to vertical) or flatter. Permanent graded fill slopes adjacent to or within the subject areas range from approximately 5 to 35 feet in height. There are no permanently graded cut slopes within or adjacent to the subject areas. The on-site fill slopes are considered grossly and surficially stable from a geotechnical standpoint (under normal irrigation/precipitation patterns) provided the project geotechnical recommendations are incorporated into the fine-grading, post-grading, construction, and post-construction phases of site development. Project No. 133023-03 Page 5 March 24, 2016 3.0 CONCLUSIONS 3.1 General The rough-grading for Lots 82 through 87, 92 through 99, 105 through 110, 115 through 121 within Planning Area PA-3 and Lots 212 through 215 and 226 through 233 within Planning Area PA-6 of the Robertson Ranch development located within the City of Carlsbad, California was performed in general accordance with the project geotechnical report (LGC, 2014a), geotechnical recommendations made during the course of grading, and the City of Carlsbad grading requirements. It is our professional opinion that the subject lots are suitable for the intended use provided the recommendations of the referenced geotechnical reports (LGC, 2014a and 2015a through 2016b) are incorporated into the design and construction; and that proper landscaping, irrigation, and maintenance programs are implemented. 3.2 Summary of Conclusions The following is a summary of our conclusions concerning the rough-grading of the subject lots: Rough-grading of the lots is essentially complete. Geotechnical conditions encountered during the rough-grading operation were generally as anticipated. The geologic units encountered during the rough-grading of the site consisted of undocumented fill soils, topsoil, colluvium, and the Santiago Formation. Unsuitable undocumented fill soils, topsoil, colluvium, alluvium, and desiccated and/or weathered formational material were removed to competent formational material within the limits of grading. Landslides or surficial slope failures were not encountered during the grading operations. No evidence of active faulting was encountered during the rough-grading operations; however, a fault was encountered along the rear of Lots 212 through 215 of PA-6, trending in a roughly north-south direction. Based on our geologic analysis, it is our professional opinion that the faults are not active; and therefore are not a constraint to development. Ground water seepage conditions were not encountered during the subject grading operations. Stability fills were constructed to improve the gross stability of the cut slope exposing fractured and blocky formational material and/or adverse geologic conditions on the site and were excavated in accordance with the project geotechnical recommendations. A stability fill was excavated along the proposed slopes on the east side of Lots 212 through 215. A subdrain was placed along the heel of the stability fill key. The subdrain was outletted at 100-foot intervals along the toe-of-slope of the stability fill slope. The cut/fill transition conditions were present within the limits of Lots 82 and 226 through 233. These lots were overexcavated a minimum of 5 feet beneath the finish grade surfaceto a distance of at least 10 feet outside the planned building limits. Project No. 133023-03 Page 6 March 24, 2016 Overexcavation of Lots 83 through 87, 92 through 99, 105 through 110, and 115 through 121 was performed in order to mitigate potential adverse conditions due to expansive soils. The entire portion of the cut lots were overexcavated a minimum of 5 feet below finish pad grade and replaced with compacted fill having a lower expansion potential. Overexcavation of Lots 212 and 213 was performed in order to mitigate the potential difficult excavation of the proposed residential building footings due to cemented beds within the formational material exposed at finish grade of these two lots. During the rough-grading operations, remedial grading was performed so that the fill differential beneath the proposed building pads was less than a 3:1 (maximum fill thickness to the minimum fill thickness). Fill soils were derived from on-site soils. Where tested, the fill soils within the site were compacted at least a 90 or 93 percent relative compaction (based on ASTM Test Method D1557) and near-optimum moisture content in accordance with the recommendations of the project geotechnical report (LGC, 2014a) and the requirements of the City of Carlsbad. Fill soils less than 40 feet below the design finish grades were compacted to a minimum 90 percent relative compaction while fill soils greater than 40 feet below the design finish grades were compacted to a minimum 93 percent relative compaction. Due to the dense nature of the on-site soils, it is our professional opinion that the liquefaction hazard at the site is considered low. Representative testing of the finish grade soils on the building pads of the subject lots indicated that: 1) Lots 115 through 121 have a medium expansion potential; 2) Lots 82 through 87, 92 through 99, 105 through 110, 214 and 215 have a low expansion potential; and 3) Lots 212, 213 and 226 through 233 have a very low expansion potential. The test results are presented in Appendix B. The potential for soluble sulfate attack on concrete in contact with the finish grade soils of the subject lots is considered negligible based on ACT Criteria (ACT 318R-05 Table 4.3.1). The soluble sulfate content test results are included in Appendix B. Laboratory testing of representative soil samples indicated that the near surface soils are corrosive to severely corrosive to buried metals. The laboratory test results are presented in Appendix B. It is our professional opinion that the slopes of the development are considered to be grossly and surficially stable, as constructed, under normal irrigation/precipitation patterns, provided the recommendations in the project geotechnical reports are incorporated into the post-grading, construction and post-construction phases of site development. Project No. 133023-03 Page 7 March 24, 2016 4.0 RECOMMENDATIONS 4.1 Earthwork We anticipate that future earthwork at the site will consist of site preparation, fine-grading, utility trench excavation and backfill, retaining wall backfill, and street/driveway and parking area pavement section preparation and compaction. We recommend that the earthwork on site be performed in accordance with the geotechnical recommendations presented in the project preliminary geotechnical report (LGC, 2014a) and the City of Carlsbad grading requirements. 4.2 Site Preparation During future grading (if any), the areas to receive structural fill or engineered structures should be cleared of surface obstructions, potentially compressible material (such as desiccated fill soils or weathered formational material), and stripped of vegetation. Vegetation and debris should be removed and properly disposed of off-site. Holes resulting from removal of buried obstructions that extend below finish site grades should be replaced with suitable compacted fill material. Areas to receive fill and/or other surface improvements should be scarified to a minimum depth of 12 inches, brought to optimum moisture condition, and recompacted to at least 90 percent relative compaction (based on ASTM Test Method D1557). If the length of time between the completion of grading and the construction of the development is longer than six months, we recommend that the building pads be evaluated by the geotechnical consultant and, if needed, the finish grade soils on the building pads should be scarified a minimum of 12 inches, moisture-conditioned to optimum moisture-content and recompacted to a minimum 90 percent relative compaction (based on ASTM Test Method D1557). 4.3 Excavations Excavations of the on-site materials may generally be accomplished with conventional heavy-duty earthwork equipment. It is not anticipated that blasting will be required or that significant quantities of oversized rock (i.e. rock with maximum dimensions greater than 8 inches) will be generated during future grading. However, localized cemented zones within the cut areas may be encountered on the site that may require heavy ripping and/or removal. If oversized rock is encountered, it should be placed in accordance with the project geotechnical recommendations (LGC, 2014a), hauled offsite, or placed in non-structural or landscape areas. Temporary excavations maybe cut vertically up to five feet. Excavations over five feet should be slot- cut, shored, or cut to a 1:1 (horizontal to vertical) slope gradient. Surface water should be diverted away from the exposed cut, and not be allowed to pond on top of the excavations. Temporary cuts should not be left open for an extended period of time. Planned temporary conditions should be reviewed by the geotechnical consultant in order to reduce the potential for sidewall failure. The geotechnical consultant may provide recommendations for controlling the length of sidewall exposed. Project No. 133023-03 Page 8 March 24, 2016 4.4 Fill Placement and Compaction The on-site soils are generally suitable for use as compacted fill provided they are free or organic material, debris, and rock fragments larger than 8 inches in maximum dimension. We do not recommend that high or very high expansive soils be utilized as fill for the building pads or as retaining wall backfill. All fill soils should be brought to 2-percent over the optimum moisture content and compacted in uniform lifts to at least 90 percent relative compaction based on the laboratory maximum dry density (ASTM Test Method D1557). The optimum lift thickness required to produce a uniformly compacted fill will depend on the type and size of compaction equipment used. In general, fill should be placed in lifts not exceeding 8 inches in compacted thickness. Placement and compaction of fill should be performed in general accordance with current City of Carlsbad grading ordinances, sound construction practices, and the project geotechnical recommendations. If import soils are to be used as fill, they should be: 1) essentially free from organic matter and other deleterious substances; 2) contain no materials over 6 inches in maximum dimension; 3) have a very low to low expansion potential (i.e. an Expansion Index ranging from 0 to 50); and 4) have a negligible sulfate content. Representative samples of the desired import source should be given to the Geotechnical Consultant at least 48 hours (2 working days) before importing grading begins so that its suitability can be determined and appropriate tests performed. 4.5 Foundation Recommendations The preliminary foundation design recommendations applicable to the construction of the residential structures on the subject lots were previously provided in the our letter report entitled "Preliminary Foundation Design for the Single-Family Residential Structures, Planning Areas PA-3, PA-S, PA-6, PA-9, PA-b, and PA-13, Robertson Ranch", dated April 14, 2015 (LGC, 2015a) and our letter entitled "Deepened Footing Recommendation of Building Foundation Adjacent to Proposed Nexus eWater Recycler System, Planning Areas PA-3, PA-S, PA-6, PA-9, PA-b, and PA-13, Robertson Ranch" dated July 23, 2015 (LGC, 2015c). The previous recommendations remain applicable for the design of the proposed structures on the subject lots. Based on the expansion potential and corrosion laboratory testing of representative soils on the subject lots, 212, 213 and 226 through 233 have a very low expansion potential; Lots 82 through 87, Lots 92 through 99, Lots 105 through 110, and Lots 214 and 215 have a low expansion potential; and Lots 115 through 121 have a medium expansion potential. The finish grade soils on these lots are considered to have negligible sulfate content and are corrosive to severely corrosive to buried metals. The results of the expansion potential and corrosion testing are presented in Appendix B. Project No. 133023-03 Page 9 March 24, 2016 4.6 Control of Surface Water and Drainage Surface drainage should be carefully taken into consideration during fine-grading, landscaping, and building construction. Positive drainage of surface water away from structures is very important. No water should be allowed to pond adjacent to buildings or the top of slopes. Positive drainage may be accomplished by providing drainage away from buildings at a gradient of at least 2 percent for a distance of at least 5 feet, and further maintained by a swale of drainage path at a gradient of at least 1 percent. Where limited by 5-foot side yards, drainage should be directed away from foundations for a minimum of 3 feet and into a collective swale or pipe system. Where necessary, drainage paths may be shortened by use of area drains and collector pipes. Eave gutters also help reduce water infiltration into the subgrade soils if the downspouts are properly connected to appropriate outlets. The impact of heavy irrigation or inadequate runoff gradient can create perched water conditions, resulting in seepage or shallow groundwater conditions where previously none existed. Maintaining adequate surface drainage and controlled irrigation will significantly reduce the potential for nuisance-type moisture problems. To reduce differential earth movements (such as heaving and shrinkage due to the change in moisture content of foundation soils, which may cause distress to a structure or improvement), the moisture content of the soils surrounding the structure should be kept as relatively constant as possible. All area drain inlets should be maintained and kept clear of debris in order to function properly. Rerouting of site drainage patterns and/or installation of area drains should be performed, if necessary. A qualified civil engineer or a landscape architect should be consulted prior to rerouting of drainage. Project No. 133023-03 Page 10 March 24, 2016 5.0 LIMITATIONS Our services were performed using the degree of care and skill ordinarily exercised, under similar circumstances, by reputable engineers and geologists practicing in this or similar localities. No other warranty, expressed or implied, is made as to the conclusions and professional advice included in this report. The samples taken and submitted for laboratory testing, the observations made and the in-situ field testing performed are believed representative of the entire project; however, soil and geologic conditions revealed by excavation may be different than our preliminary findings. If this occurs, the changed conditions must be evaluated by the project soils engineer and geologist and design(s) adjusted as required or alternate design(s) recommended. This report is issued with the understanding that it is the responsibility of the owner, or of his/her representative, to ensure that the information and recommendations contained herein are brought to the attention of the architect and/or project engineer and incorporated into the plans, and the necessary steps are taken to see that the contractor and/or subcontractor properly implements the recommendations in the field. The contractor and/or subcontractor should notify the owner if they consider any of the recommendations presented herein to be unsafe. The findings of this report are valid as of the present date. However, changes in the conditions of a property can and do occur with the passage of time, whether they be due to natural processes or the works of man on this or adjacent properties. In addition, changes in applicable or appropriate standards may occur, whether they result from legislation or the broadening of knowledge. Accordingly, the findings of this report may be invalidated wholly or partially by changes outside our control. Project No. 133023-03 Page 11 March 24, 2016 A PFENDIX A References American Society of Civil Engineers (ASCE), 2013, Minimum design loads for buildings and other structures, ASCE/SEI 7-10, Third Printing, 2013. California Building Standards Commission (CBSC), 2013a, California Building Code, California Code of Regulations, Title 24, Part 2, Volume 1 and 2 of 2 (based on the 2012 International Building Code). CBSC, 2013b, California Residential Building Code, California Code of Regulations, Title 24, Part 2.5,(based on the 2012 International Residential Code). CBSC, 2013c, California Green Building Standards Code, California Code of Regulations, Title 24, Part 11. GeoSoils, Inc., 2002, Geotechnical evaluation of the Robertson Ranch Property, City of Carlsbad, San Diego County, California, W.O. 3098-Al-SC, dated January 29, 2002. GeoSoils, Inc., 2004, Updated geotechnical evaluation of the Robertson Ranch property, Carlsbad, San Diego County, California, W.O. 3098-A2-SC, dated September 20, 2004. GeoSoils, Inc., 2010, Updated geotechnical investigation for Robertson Ranch West Village, Carlsbad, San Diego County, California, W.O. 6145-A-SC, dated October 10, 2010. GeoSoils, Inc., 2011, Supplement to the updated geotechnical investigation for Rancho Costera (formerly Robertson Ranch West Village), Carlsbad, San Diego County, California, W.O. 6145-Al-SC, dated June 6. GeoSoils, Inc., 2012, Preliminary geotechnical review of "vesting master tentative map for Rancho Costera," 40-scale plans, sheets 1 through 21, Job No. 101307, Revised May 1, 2012, by O'Day Consultants, W.O. 6145-A9-SC, dated May 24, 2012. GeoSoils, Inc., 2013, Addendum to the updated and supplemental geotechnical investigations for Rancho Costera (formerly Robertson Ranch West Village), Carlsbad, San Diego County, California, W.O. 6145-AIO-SC, dated July 16, 2013. LGC Valley, Inc., 2014a, Geotechnical and environmental recommendations for Robertson Ranch West, Carlsbad Tract No. 13-03, Carlsbad, California, Project Number 133023-03, dated April 29, 2014. LGC Valley, Inc., 2014b, Change of Geotechnical Consultant, Robertson Ranch West Project, Carlsbad Tract No. 13-0, Carlsbad, California, Project No. 133023-03, dated May 6, 2014. LGC Valley, Inc., 2015a, Preliminary Foundation Design for the Single-Family Residential Structures, Planning Areas PA-3, PA-5, PA-6, PA-9, PA-b, and PA-13, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 1.33023-06, dated April 14, 2015. Project No. 133023-03 Page A-i March 24, 2016 References (continued) LGC Valley, Inc., 2015b, Preliminary Review of Building Setbacks for the Proposed Residential Planning Areas 3, 5, 6, 9, 10, and 13, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-03, dated February 27, 2015, revised June 24, 2015. LGC Valley, Inc., 2015c, Deepened Footing Recommendation of Building Foundation Adjacent to Proposed Nexus eWater Recycler System, Planning Areas PA-3, PA-5, PA-6, PA-9, PA-10, and PA-13, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-03, dated July 23, 2015. LGC Valley, Inc., 2015d, Geotechnical Post-Tension Foundation Plan Review for The Vistas Development within Planning Area 6 (PA-6), Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-06, dated August 4, 2015. LGC Valley, Inc., 2015e, Geotechnical Post-Tension Foundation Plan Review for The Ridge Development within Planning Area 3 (PA-3), Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-06, dated August 4, 2015. LGC Valley, Inc., 2015f, Geotechnical Post-Tension Foundation Plan Review for The Vistas Development within Planning Area 6 (PA-6), Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-06, dated October 21, 2015. LGC Valley, Inc., 2015g, Geotechnical Post-Tension Foundation Plan Review for The Ridge Development within Planning Area 3 (PA-3), Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-06, dated November 4, 2015. LGC Valley, Inc., 2015h, Presaturation Recommendations Concerning the Proposed Single-Family Residential Structures, The Ridge, Lots 63 through 149 of Planning Area PA-3, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-06, dated December 2, 2015. Nexus eWater, 2015, Recycler System Standard Drawings, 9 Sheets, dated April 30, 2015. O'Day Consultants, 2014a, Vesting tentative map for Carlsbad Tract No. 13-03-2, 23 Sheets, dated January 16, 2014. O'Day Consultants, 2014b, Grading plans for Rancho Costera, Robertson Ranch West Village, Carlsbad Tract No. 13-03, Drawing No. 480-3A, 44 Sheets, dated August 25, 2014. Post-Tensioning Institute, 2006, Design of post tensioned slabs-on-ground, Third Addition, Addendum 1 dated May 2007, and Addendum 2 dated May 2008, with errata February 4, 2010. Specialty Steel, 2015, Post-Tension Plans, Details, and General Notes for The Bluffs (PA-5) at Robertson Ranch, Carlsbad, California, Reference No. 4302, dated December 17, 2015. Specialty Steel, 2016, Post-Tension Plans, Details, and General Notes for The Terraces at Robertson Ranch, PA-9 and PA-b, Carlsbad, California, Reference No. 4301, dated November 20, 2015 with Delta 1 Dated January 29, 2016. Project No. 133023-03 Page A-2 March 24, 2016 References (continued) Suncoast Post-Tension, 2015a, Post-Tension Plans, Details, and General Notes for The Vistas at Robertson Ranch, PA-6, Carlsbad, California. Project No. 15-6428, dated August 3, 2015 Delta 1 dated October 8, 2015. Suncoast Post-Tension, 2015b, Post-Tension Plans, Details, and General Notes for The Ridge at Robertson Ranch, PA-3, Carlsbad, California. Project No. 15-6429, dated Delta 1 - October 29, 2015. United States Geological Survey (USGS), 2008a, "2008 National Seismic Hazard Maps - Fault Parameters" retrieved from: http://geohazards.usgs.gov/cfusion/hazfaults search/hf_ search _main .cfm USGS, 2008b, "2008 Interactive Deaggregations (Beta)," retrieved from: https://geohazards.usgs.gov/deaggint/2008/ USGS, 2013, U.S. Seismic Design Maps, retrieved from: http://geohazards.usgs.gov/designmaps/us/batch.php#csv Project No. 133023-03 Page A-3 March 24, 2016 APPENDJX B Laboratory Testing Procedures and Test Results Expansion Index Tests: The expansion potential of selected materials was evaluated by the Expansion Index Test, U.B.C. Standard No. 18-I-13. Specimens are molded under a given compactive energy to approximately the optimum moisture content and approximately 50 percent saturation or approximately 90 percent relative compaction. The prepared 1-inch thick by 4-inch diameter specimens are loaded to an equivalent 144 psf surcharge and are inundated with tap water until volumetric equilibrium is reached. The results of these tests are presented in the table below: Test Representative Lots Sample Description Expansion Expansion Location Index Potential Lot 73 Lots 7 1-74 & 82-84 Pale gray brown silty fine 22 Low SAND Lot 76 Lots 75, 76, &85-87 Pale gray brown silty fine 40 Low SAND Lot 95 Lots 92-95 & 105 Pale gray brown silty fine 42 Low SAND Lot 108 Lots 96-99 & 106-110 Light brown silty fine SAND 34 Low Lot 119 Lots 115-121 Light brown silty to clayey fine 52 Medium SAND Lot 229 Lots 212, 213, and Pale gray brown silty fine 19 Very Low 226-233 SAND Lot 221 Lots 214-225 Pale orange brown silty fine 34 Low SAND Project No. 133023-03 Page B-i March 24, 2016 Laboratory Testini? Procedures and Test Results (continued) Soluble Sulfates: The soluble sulfate contents of selected samples were determined by standard geochemical methods (Caltrans 417). The test results are presented in the table below: Test Location Sample Description Sulfate Content (% by Weight) Potential Degree of Sulfate Attack* PA-3 Light brown silty fine SAND 0.011 Negligible PA-3 Light grayish brown silty fine SAND 0.033 Negligible PA-6 Pale yellow brown silty fine SAND 0.071 Negligible PA-6 Medium brown silty clayey SAND 0.025 Negligible * Per ACT 318R-08 Table 4.3.1. Chloride Content: Chloride content was tested in accordance with Caltrans Test Method (CTM) 422. The results are presented below: Test Location Sample Description Chloride Content (ppm) Potential Degree of Chloride Attack* PA-3 Light brown silty fine SAND 270 Negligible PA-3 Light grayish brown silty fine SAND 220 Negligible PA-6 Pale yellow brown silty fine SAND 175 Negligible PA-6 Medium brown silty clayey SAND 205 Negligible * Extrapolation from California Test Method 532, Method for Estimating the Time to Corrosion of Reinforced Concrete Substructures and previous experience Project No. 133023-03 Page B-2 March 24, 2016 Laboratorp Testima Procedures and Test Results (continued) Minimum Resistivity and pH Tests: Minimum resistivity and pH tests were performed in general accordance with CTM 643 and standard geochemical methods. The electrical resistivity of a soil is a measure of its resistance to the flow of electrical current. As results of soil's resistivity decreases corrosivity increases. The results are presented in the table below: Test Sample Description Minimum Resistivity Potential Degree Location (ohms-cm) of Corrosivity* PA-3 Light brown silty fine SAND 1200 Moderately Corrosive PA-3 Light grayish brown silty fine SAND 570 Corrosive PA-6 Pale yellow brown silty fine SAND 800 Corrosive PA-6 Medium brown silty clayey SAND 640 Severely Corrosive * NACE Corrosion Basics Project No. 133023-03 Page B-3 March 24, 2016 LGC Valley, Inc. Geotechnical Consulting AS-GRADED REPORT OF ROUGH-GRADING, LOTS 59, 60, 216-225, 234-244, 299-301, 308-310, AND 320-324, PLANNING AREAS PA-5, PA-6, AND PA-9&10, ROBERTSONRANCH, CARLSBAD TRA CT NO.13-03, CARLSBAD, CALIFORNIA Project No. 133023-03 Dated: February 3, 2016 Prepared For: Toll Brothers 725 Town and Country Road, Suite 200 Orange, California 92868 2420 Grand Avenue, Suite F2 • Vista • CA 92081 • (760) 599-7000 • Fax (760) 599-7007 LGC Valley, Inc. Geotechnical Consulting February 3, 2016 Mr. Greg Deacon Toll Brothers 725 Town and Country Road, Suite 500 Orange, California 92868 Project No. 133023-03 Subject: As-Graded Report of Rough Grading, Lots 59, 60, 216 through 225, 234 through 244, 299 through 301, 308 through 310, and 320 through 324, Planning Areas PA-5, PA-6, and PA- 9&10, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California In accordance with the request and authorization of Toll Brothers, LGC Valley, Inc. (LGC) has provided geotechnical services during the rough-grading operations for Lots 59 and 60 of Planning Area PA-5; Lots 216 through 225 and 234 through 244 of Planning Area PA-6; and Lots 299 through 301, 308 through 310, and 320 through 324 of Planning Areas PA-9 and PA- 10; part of the Robertson Ranch project (Carlsbad Tract No. 13- 03) located within the City of Carlsbad, California. The accompanying as-graded report of rough-grading summarizes our observations, field and laboratory test results, and the geotechnical conditions encountered during grading of the subject lots. The rough-grading operations for the subject lots were performed in general accordance with previously published project geotechnical reports (Appendix A), geotechnical recommendations made during the course of grading, and the City of Carlsbad grading requirements. It is our professional opinion that the subject lots are suitable for the intended use provided the recommendations included herein and in the project geotechnical reports are incorporated into the fine-grading, design, and construction of the proposed development and associated improvements. As of the date of this report, the rough-grading operations for the subject lots are essentially complete. If you have any questions regarding our report, please contact this office. We appreciate this opportunity to be of service. Respectfully Submitted, LGC Valley, Inc. 0 wo~' Randall Wagner, CEG 1612 Senior Project Geologist 1/ 1.qL Basil Hattar, GE 2734 2734 Principal Engineer OFC Distribution: (7) Addressee (1) Toll Brothers; Attention Ms. JoAnn Epstine (via e-mail) (1) Toll Brothers; Attention Mr. Kevin Brickley (via e-mail) (1) Toll Brothers; Attention Mr. Mike Steffen (via e-mail) 2420 Grand Avenue, Suite F2 • Vista • CA 92081 (760) 599-7000 • Fax (760) 599-7007 TABLE OF CONTENTS Section 1.0 INTRODUCTION ......................................................................................................................................... 1 2.0 SUMMARY OF ROUGH-GRADING OPERATIONS.................................................................................2 2.1 As-Graded Conditions.......................................................................................................................2 2.2 Site Preparation and Removals.........................................................................................................3 2.3 Stability Fills.....................................................................................................................................4 2.4 Subdrain Installation.........................................................................................................................4 2.5 Overexcavation of Cut/Fill Transition Conditions ............................................................................4 2.6 Overexcavation of Cut Lots...............................................................................................................5 2.7 Fill Placement and Compaction........................................................................................................5 2.8 Laboratory Testing............................................................................................................................5 2.9 Field Density Testing........................................................................................................................5 2.10 Graded Slopes...................................................................................................................................6 3.0 CONCLUSIONS...........................................................................................................................................7 3.1 General.............................................................................................................................................7 3.2 Summary of Conclusions..................................................................................................................7 4.0 RECOMMENDATIONS..............................................................................................................................9 4.1 Earthwork.........................................................................................................................................9 4.2 Site Preparation ...............................................................................................................................9 4.3 Excavations ......................................................................................................................................9 4.4 Fill Placement and Compaction.....................................................................................................10 4.5 Preliminary Foundation Recommendations ..................................................................................10 4.6 Control of Surface Water and Drainage ........................................................................................ 11 5.0 LIMITATIONS...........................................................................................................................................12 Appendices Appendix A - References Appendix B - Laboratory Testing Procedures and Test Results Project No. 133023-03 Page i February 3, 2016 1.0 INTRODUCTION In accordance with the request and authorization of Toll Brothers, LGC Valley, Inc. (LGC) has provided geotechnical services during the rough-grading operations of Lots 59 and 60 of Planning Area PA-5; Lots 216 through 225 and 234 through 244 of Planning Area PA-6; and Lots 299 through 301, 308 through 310, and 320 through 324 of Planning Areas PA-9 and PA- 10; part of the Robertson Ranch project (Carlsbad Tract No. 13-03) located within the City of Carlsbad, California. This as-graded report summarizes our observations, field and laboratory test results, and the geotechnical conditions encountered during grading of the subject lots. The subject rough-grading operations were performed in general accordance with previously published project geotechnical reports (Appendix A), geotechnical recommendations made during the course of grading, and the City of Carlsbad grading requirements. As of this date, the rough-grading operations for the subject lots are essentially complete. The Rough Grading Plans for the Robertson Ranch project, prepared by O'Day Consultants (O'Day, 2014b), were utilized as a base map to present the as-graded geotechnical conditions and approximate locations of the field density tests. The As-graded Geotechnical Map and the Field Density Test Location Map will be provided in the final as-graded report for Robertson Ranch upon completion of all of the rough-grading operations. Lots 59 and 60 of Planning Area PA-5 are located in the western portion of Robertson Ranch along the south side of Glasgow Drive while Lots 216 through 225 and 234 through 244 of Planning Area PA-6 and Lots 299 through 301, 308 through 310, and 320 through 324 of Planning Areas PA-9 and PA-10 are located in the east-central portion of the project along Wadsworth Street, Chase Court and Kentner Court. Ultimately, development of Planning Area PA-5, PA-6, and PA-9 and 10 will include the construction of 36, 87, and 75 single-family residential lots, respectfully; along with associated retaining walls, slopes, storm water retention basins, and adjacent streets. The rough-grading operations for Lots 59 and 60 of Planning Area PA-5; Lots 216 through 225 and 234 through 244 of Planning Area PA-6; and Lots 299 through 301, 308 through 310, and 320 through 324 of Planning Areas PA-9 and PA- 10 were performed as a part of grading operations for the entire Robertson Ranch Development between September 2014 and October 2015. Project No. 133023-03 Page 1 February 3, 2016 2.0 SUMMARY OF ROUGH-GRADING OPERATIONS Rough-grading of the subject site began on September 5, 2014 and was essentially completed as of October 22, 2015. The grading operations were performed under the observation and testing services of LGC Valley, Inc. Our field technicians were onsite on a full-time basis during the grading operations while our field geologist was onsite on a periodic basis. The rough-grading operations included: Removal and off-site disposal of vegetation and miscellaneous debris; The removal of potentially compressible soils including colluvium, topsoil, undocumented fill, and weathered soils to competent formational material; Overexcavation of cut/fill transition conditions within the lots; Overexcavation of buried cut/fill transition conditions such that the resulting fill differential beneath the proposed building pads was less than a 3:1 (maximum fill thickness to the minimum fill thickness); Overexcavation of cut lots due to expansive soils; Preparation of areas to receive fill; The placement of subdrains in the canyon bottoms and along the heel of the stability fill keys; Excavation of formational material; and The placement of compacted fill soils creating the graded pads and adjacent slopes. The rough-grading operations consisted of the placement of fill up to approximately 45 feet in depth and cuts up to approximately 20 feet within the subject lots. During the rough-grading operations, remedial grading was also performed so that the fill differentials beneath the proposed building pads were less than a 3:1 (maximum fill thickness to the minimum fill thickness). 2.1 As-Graded Conditions The as-graded conditions encountered during grading of the lots were essentially as anticipated. In the vicinity of the Lots 234 through 244, 299, 308, 309, 323, and 324, minor alluvium and colluvium were encountered on the upper hillsides and small tributary ravines of the main canyon running in a northwest-southeast between Planning Areas PA-6 and PA-9/PA-10 and in the small canyon in the vicinity of Lots 323 and 324. Formational material was encountered on the slopes and at design cut grade below a thin veneer of topsoil and weathered soils on the remainder of the lots. All unsuitable and potentially compressible soils were removed prior to fill placement. This included alluvium, colluvium, undocumented fill (associated with the past agricultural operations), and weathered formational materials. The alluvium, colluvium, and topsoil typically consisted of light brown to brown silty fine sands, sandy clays and clayey sands derived from on-site soils and were found to be very low to highly expansive, porous, and contained scattered organics. Removals of alluvium and colluvium up to approximately 5 to 15 feet in depth were made in the vicinity of Lots 234 through 244, 299, 308, 309, 323, and 324. Removals of the topsoil and weathered formational material that was on the order of 2 to 6 feet were made in the other areas of the site. Project No. 133023-03 Page 2 February 3, 2016 The formational material encountered on the subject lots consisted of the Santiago Formation. The material was found to be massively bedded to cross-bedded silty sandstones and minor clayey sandstones, silty claystones and sandy siltstones. The claystones and siltstones generally were olive green and orange brown, damp to moist, stiff to hard, moderately fractured and sheared. The sandstone generally consisted of light olive green, light brown and pale orange brown (where iron- oxidized stained), damp to moist, dense to very dense, silty very fine to medium grained sandstone. The majority of the Santiago material encountered within Robertson Ranch consisted of silty fine sands. Bedding within the Santiago Formation was highly variable, but overall, generally dipped 2 to 15 degrees to the west-southwest. A zone of two to three minor inactive faults was geologically mapped trending in a north-south direction in the middle of Planning Areas PA-9 and PA- 10. Geologic mapping indicated the faults trended NYE to N16°E steeply dipping 60 to 85 degrees to the west. The faults were only observed within the Santiago Formation and the fault zone appeared to die out to the south. Based on our geologic analysis during the current grading operations and review of the applicable geotechnical reports referenced in Appendix A, it is our professional opinion that the faults are not active; and therefore are not a constraint to development. No groundwater was encountered during the grading of the subject lots. However, unanticipated seepage conditions may occur after the completion of grading and establishment of site irrigation and landscaping. If these conditions should occur, steps to mitigate the seepage should be made on a case-by-case basis. 2.2 Site Preparation and Removals Prior to grading, the site was cleared of light vegetation and other miscellaneous debris and the material was disposed of at an offsite facility. Undocumented fill, topsoil, alluvium, colluvium, and weathered formational material were removed down to competent material (i.e. dense unweathered formational material). Remedial removals on site, below the existing ground surface, ranged from approximately 2 to 20 feet in depth. The thickness of compacted fills placed during this recent rough- grading operation, to achieve design rough grades (or sheet-graded pad elevations), ranged from 0 to approximately 45 feet. Following the remedial removals or overexcavations, areas to receive fill were scarified approximately 6-inches, moisture-conditioned, as needed, to obtain a near-optimum moisture content and compacted to a minimum 90 percent relative compaction (for fills of approximately 40 feet or less from design grades) or 93 percent relative compaction (for engineered fill below approximately 40 feet from design finish grades), as determined by ASTM Test Method D6938 (i.e. the nuclear gauge method). Project No. 133023-03 Page 3 February 3, 2016 2.3 Stability Fills Stability fills were constructed to stabilize the exposed blocky claystone/siltstone and/or adverse (i.e. out-of-slope) geologic conditions present within the Santiago Formation. The stability fill keys were excavated to a width of approximately 15 feet and a minimum depth of 3 to 5 feet below the toe-of- slope. The keyway bottom was angled at least 2 percent into-the-slope. The stability fill front cuts were excavated near vertical while the back-cuts were excavated at an approximate 1:1 to 1.5 (horizontal to vertical) slope inclinations. Stability fills were excavated along the proposed slopes on: 1) the southwest side Lot 60; 2) the southeast side of Lots 59 and 60; 3) the west side of Lots 216 through 225; 4) the north side of Lots 299 through 301; and 5) the north side of Lots 320 through 323. 2.4 Subdrain Installation Canyon and stability fill subdrains were installed under the observation of a representative of LGC in general accordance with the planned locations of the approved geotechnical report, and the standard details (LGC, 2014a). After the potentially compressible material in the canyons were removed to competent material or when compacted fill was placed over competent material to obtain flow to a suitable outlet location, a subdrain was installed along the canyon bottom. The canyon subdrains consisted of a 6-inch diameter perforated pipe surrounded by a minimum of 9- cubic feet (per linear foot) of crushed 3/4-inch gravel wrapped in Mirafi 140N filter fabric. In addition to the canyon subdrains, subdrains were also installed along the bottom backside of the stability fill keys. The stability fill subdrains consisted of a 4-inch diameter perforated pipe surrounded by a minimum of 3-cubic feet (per linear foot) of clean 3/4-inch gravel wrapped in Mirafi 140N filter fabric. The canyon and stability fill subdrains were placed with a minimum 1-percent fall (2-percent or greater where possible) to a suitable outlet location. The location of the subdrains placed during the mass grading operations for the project were surveyed by the project civil engineer. 2.5 Overexcavation of Cut/Fill Transition Conditions Based on the as-graded conditions, the cut/fill transition condition present within the lots, as shown on the rough grading plans (O'Day, 2014b), were overexcavated a minimum of 5 feet in depth beneath the proposed finish grade surface of the lot. The overexcavation extended to a distance of at least 10 feet outside the planned building limits. Lots that were overexcavated due to the cut/fill transition condition include Lots 244, 300, 301, 310, 322, and 323. During the rough-grading operations, remedial grading was also performed so that the fill differential beneath the proposed building pads was less than a 3:1 (maximum fill thickness to the minimum fill thickness). Project No. 133023-03 Page 4 1 February 3, 2016 Z6 Overexcavation of Cut Lois During the rough-grading operations, the overexcavation of cut lots was performed in order to mitigate potential adverse conditions due to expansive soils. The entire portion of the cut lots were overexcavated a minimum of 5 feet below finish pad grade and replaced with compacted fill having a lower expansion potential. In order to minimize potential ponded ground water conditions on the overexcavation bottom, the bottom was sloped toward the street with a minimum fall of one percent. Cut lots that were overexcavated included Lots 60, 320, and 321. 2.7 Fill Placement and Compaction After processing the areas to receive fill, native soil was generally spread in approximately 8-inch loose lifts, moisture-conditioned as needed to attain near-optimum moisture content, and compacted to at least 90 or 93 percent of the maximum dry density determined in accordance with ASTM Test Method D1557. Fill soils less than 40 feet below the design finish grades were compacted to a minimum 90 percent relative compaction while fill soils greater than 40 feet below the design fmish grades were compacted to a minimum 93 percent relative compaction. Compaction was achieved by use of heavy-duty construction equipment. Areas of fill in which either field density tests indicated less than 90 or 93 percent relative compaction or the soils exhibited nonuniformity and/or showed an inadequate or excessive moisture content, were reworked, recompacted, and retested until a minimum 90 or 93 percent relative compaction and near-optimum moisture content was achieved. 2.8 Laboratory Testing Maximum dry density tests of representative on-site soils were performed (by others during the previous investigation and by LGC during the current rough-grading operations) in general accordance with ASTM Test Method D1557. Expansion potential, soluble sulfate content, and corrosion testing of representative finish grade soils within the subject lots were performed. Based on the laboratory testing, Lots 59 and 234 through 244 have a very low expansion potential; Lots 216 through 225 have a low expansion potential; and Lots 60, 299 through 301, 308 through 310, and 320 through 324 have a medium expansion potential. Laboratory testing also indicated that the near surface soils have a negligible soluble sulfate content; are corrosive to severely corrosive to buried metals based on the minimum soil resistivity values; and are corrosive to buried metals and reinforcing steel in concrete based on the chloride concentrations. The laboratory test results are presented in Appendix B. 2.9 Field Density Testin' Field density testing was performed using the Nuclear-Gauge Method (ASTM Test Method D6938). The approximate test locations and the results of the field density tests will be provided in the final as-graded report for Robertson Ranch upon completion of the rough grading operations. The field density testing was performed in general accordance with the applicable ASTM standards Project No. 133023-03 Page 5 February 3, 2016 and the current standard of care in the industry. In-situ soil density testing is intended to verify the effectiveness of the earthmoving operation in general and is performed on a spot-check basis; as such, some variations in relative compaction should be expected from the results documented herein. 2.10 Graded Slopes Manufactured fill slopes within the subject lots were surveyed by the civil engineer and constructed with slope inclinations of 2:1 (horizontal to vertical) or flatter. Permanent graded fill slopes adjacent to or within the subject areas range from approximately 5 to 50 feet in height. There are no permanently graded cut slopes within or adjacent to the subject areas. The on-site fill slopes are considered grossly and surficially stable from a geotechnical standpoint (under normal irrigation/precipitation patterns) provided the project geotechnical recommendations are incorporated into the fine-grading, post-grading, construction, and post-construction phases of site development. LI Project No. 133023-03 Page 6 February 3, 2016 3.0 CONCLUSIONS 3.1 General The rough-grading of Lots 59 and 60 of Planning Area PA-5; Lots 216 through 225 and 234 through 244 of Planning Area PA-6; and Lots 299 through 301, 308 through 310, and 320 through 324 of Planning Areas PA-9 and PA-10 of the Robertson Ranch development located within the City of Carlsbad, California was performed in general accordance with the project geotechnical report (LGC, 2014a), geotechnical recommendations made during the course of grading, and the City of Carlsbad grading requirements. It is our professional opinion that the subject lots are suitable for the intended use provided the recommendations of the referenced geotechnical reports (LGC, 2014a and 2015a through 2016b) are incorporated into the design and construction; and that proper landscaping, irrigation, and maintenance programs are implemented. 3.2 Summary of Conclusions The following is a summary of our conclusions concerning the rough-grading of Lots 127 through 149 of Planning Area PA-3: Rough-grading of the lots is essentially complete. Geotechnical conditions encountered during the rough-grading operation were generally as anticipated. The geologic units encountered during the rough-grading of the site consisted of undocumented fill soils, topsoil, colluvium, alluvium, and the Santiago Formation. Unsuitable undocumented fill soils, topsoil, colluvium, alluvium, and desiccated and/or weathered formational material were removed to competent formational material within the limits of grading. Landslides or surficial slope failures were not encountered during the grading operations. No evidence of active faulting was encountered during the rough-grading operations; however, a zone of two to three minor inactive faults was encountered trending in north-south direction in the middle of Planning Areas PA-9 and PA-10 (i.e. in the vicinity of Lots 310 and 320). Based on our geologic analysis, it is our professional opinion that the faults are not active; and therefore are not a constraint to development. Ground water seepage conditions were not encountered during the subject grading operations. Stability fills were constructed to improve the gross stability of the cut slope exposing fractured and blocky formational material and/or adverse geologic conditions on the site and were excavated in accordance with the project geotechnical recommendations. Stability fills were excavated along the proposed slopes on: 1) the southwest side Lot 60; 2) the southeast side of Lots 59 and 60; 3) the west side of Lots 216 through 225; 4) the north side of Lots 299 through 301; and 5) the north side of Lots 320 through 323. Project No. 133023-03 Page 7 February 3, 2016 Subdrains were placed in the canyon bottom and along the heel of the stability fill keys. The subdrains were (or will be) outletted into suitable storm drain facilities or near the toe-of-slope of the stability fill slopes. The cut/fill transition conditions present within the limits of Lots 244, 300, 301, 310, 322, and 323 were overexcavated a minimum of 5 feet beneath the finish grade surface and to a distance of at least 10 feet outside the planned building limits. Overexcavation of Lots 60, 320, and 321 was performed in order to mitigate potential adverse conditions due to expansive soils. The entire portion of the cut lots were overexcavated a minimum of 5 feet below finish pad grade and replaced with compacted fill having a lower expansion potential. During the rough-grading operations, remedial grading was performed so that the fill differential beneath the proposed building pads was less than a 3:1 (maximum fill thickness to the minimum fill thickness). Fill soils were derived from on-site soils. Where tested, the fill soils within the site were compacted at least a 90 or 93 percent relative compaction (based on ASTM Test Method D1557) and near-optimum moisture content in accordance with the recommendations of the project geotechnical report (LGC, 2014a) and the requirements of the City of Carlsbad. Fill soils less than 40 feet below the design finish grades were compacted to a minimum 90 percent relative compaction while fill soils greater than 40 feet below the design finish grades were compacted to a minimum 93 percent relative compaction. Due to the dense nature of the on-site soils, it is our professional opinion that the liquefaction hazard at the site is considered low. Representative testing of the finish grade soils on the building pads of the subject lots indicated that the near-surface soils on Lots 59 and 234 through 244 have a very low expansion potential; Lots 216 through 225 have a low expansion potential; and Lots 60, 299 through 301, 308 through 310, and 320 through 324 have a medium expansion potential. The test results are presented in Appendix B. The potential for soluble sulfate attack on concrete in contact with the finish grade soils of the subject lots is considered negligible based on ACT Criteria (ACT 318R-05 Table 4.3.1). The soluble sulfate content test results are included in Appendix B. Laboratory testing of representative soil samples indicated that the near surface soils are corrosive to severely corrosive to buried metals. The laboratory test results are presented in Appendix B. It is our professional opinion that the slopes of the development are considered to be grossly and surficially stable, as constructed, under normal irrigation/precipitation patterns, provided the recommendations in the project geotechnical reports are incorporated into the post-grading, construction and post-construction phases of site development. Project No. 133023-03 Page 8 February 3, 2016 4.0 RECOMMENDATIONS 4.1 Earthwork We anticipate that future earthwork at the site will consist of site preparation, fine-grading, utility trench excavation and backfill, retaining wall backfill, and street/driveway and parking area pavement section preparation and compaction. We recommend that the earthwork on site be performed in accordance with the geotechnical recommendations presented in the project preliminary geotechnical report (LGC, 2014a) and the City of Carlsbad grading requirements. 4.2 Site Preparation During future grading (if any), the areas to receive structural fill or engineered structures should be cleared of surface obstructions, potentially compressible material (such as desiccated fill soils or weathered formational material), and stripped of vegetation. Vegetation and debris should be removed and properly disposed of off-site. Holes resulting from removal of buried obstructions that extend below finish site grades should be replaced with suitable compacted fill material. Areas to receive fill and/or other surface improvements should be scarified to a minimum depth of 12 inches, brought to optimum moisture condition, and recompacted to at least 90 percent relative compaction (based on ASTM Test Method D1557). If the length of time between the completion of grading and the construction of the development is longer than six months, we recommend that the building pads be evaluated by the geotechnical consultant and, if needed, the fmish grade soils on the building pads should be scarified a minimum of 12 inches, moisture-conditioned to optimum moisture-content and recompacted to a minimum 90 percent relative compaction (based on ASTM Test Method D1557). 4.3 Excavations Excavations of the on-site materials may generally be accomplished with conventional heavy-duty earthwork equipment. It is not anticipated that blasting will be required or that significant quantities of oversized rock (i.e. rock with maximum dimensions greater than 8 inches) will be generated during future grading. However, localized cemented zones within the cut areas may be encountered on the site that may require heavy ripping and/or removal. If oversized rock is encountered, it should be placed in accordance with the project geotechnical recommendations (LGC, 2014a), hauled offsite, or placed in non-structural or landscape areas. Temporary excavations maybe cut vertically, up to five feet. Excavations over five feet should be slot- cut, shored, or cut to a 1:1 (horizontal to vertical) slope gradient. Surface water should be diverted away from the exposed cut, and not be allowed to pond on top of the excavations. Temporary cuts should not be left open for an extended period of time. Planned temporary conditions should be reviewed by the geotechnical consultant in order to reduce the potential for sidewall failure. The geotechnical consultant may provide recommendations for controlling the length of sidewall exposed. Project No. 133023-03 Page 9 February 3, 2016 4.4 Fill Placement and Comyaclion The on-site soils are generally suitable for use as compacted fill provided they are free or organic material, debris, and rock fragments larger than 8 inches in maximum dimension. We do not recommend that high or very high expansive soils be utilized as fill for the building pads or as retaining wall backfill. All fill soils should be brought to 2-percent over the optimum moisture content and compacted in uniform lifts to at least 90 percent relative compaction based on the laboratory maximum dry density (ASTM Test Method D1557). The optimum lift thickness required to produce a uniformly compacted fill will depend on the type and size of compaction equipment used. In general, fill should be placed in lifts not exceeding 8 inches in compacted thickness. Placement and compaction of fill should be performed in general accordance with current City of Carlsbad grading ordinances, sound construction practices, and the project geotechnical recommendations. If import soils are to be used as fill, they should be: 1) essentially free from organic matter and other deleterious substances; 2) contain no materials over 6 inches in maximum dimension; 3) have a very low to low expansion potential (i.e. an Expansion Index ranging from 0 to 50); and 4) have a negligible sulfate content. Representative samples of the desired import source should be given to the Geotechnical Consultant at least 48 hours (2 working days) before importing grading begins so that its suitability can be determined and appropriate tests performed. 4.5 Foundation Recommendations The preliminary foundation design recommendations applicable to the construction of the residential structures on the subject lots were previously provided in the our letter report entitled "Preliminary Foundation Design for the Single-Family Residential Structures, Planning Areas PA-3, PA-5, PA-6, PA-9, PA-10, and PA-13, Robertson Ranch", dated April 14, 2015 (LGC, 2015a) and our letter entitled "Deepened Footing Recommendation of Building Foundation Adjacent to Proposed Nexus eWater Recycler System, Planning Areas PA-3, PA-5, PA-6, PA-9, PA-10, and PA-13, Robertson Ranch" dated July 23, 2015 (LGC, 2015c). The previous recommendations remain applicable for the design of the proposed structures on the subject lots. Based on the expansion potential and corrosion laboratory testing of representative soils on the subject lots, Lots 59 and 234 through 244 have a very low expansion potential; Lots 216 through 225 have a low expansion potential; and Lots 60, 299 through 301, 308 through 310, and 320 through 324 have a medium expansion potential. The finish grade soils on these lots are considered to have negligible sulfate content and are corrosive to severely corrosive to buried metals. The results of the expansion potential and corrosion testing are presented in Appendix B. Project No. 133023-03 Page 10 February 3, 2016 4.6 Control of Surface Water and DrainaL'e Surface drainage should be carefully taken into consideration during fine-grading, landscaping, and building construction. Positive drainage of surface water away from structures is very important. No water should be allowed to pond adjacent to buildings or the top of slopes. Positive drainage may be accomplished by providing drainage away from buildings at a gradient of at least 2 percent for a distance of at least 5 feet, and further maintained by a swale of drainage path at a gradient of at least 1 percent. Where limited by 5-foot side yards, drainage should be directed away from foundations for a minimum of 3 feet and into a collective swale or pipe system. Where necessary, drainage paths may be shortened by use of area drains and collector pipes. Eave gutters also help reduce water infiltration into the subgrade soils if the downspouts are properly connected to appropriate outlets. The impact of heavy irrigation or inadequate runoff gradient can create perched water conditions, resulting in seepage or shallow groundwater conditions where previously none existed. Maintaining adequate surface drainage and controlled irrigation will significantly reduce the potential for nuisance-type moisture problems. To reduce differential earth movements (such as heaving and shrinkage due to the change in moisture content of foundation soils, which may cause distress to a structure or improvement), the moisture content of the soils surrounding the structure should be kept as relatively constant as possible. All area drain inlets should be maintained and kept clear of debris in order to function properly. Rerouting of site drainage patterns and/or installation of area drains should be performed, if necessary. A qualified civil engineer or a landscape architect should be consulted prior to rerouting of drainage. Project No. 133023-03 Page]] February 3, 2016 5.0 LIMITATIONS Our services were performed using the degree of care and skill ordinarily exercised, under similar circumstances, by reputable engineers and geologists practicing in this or similar localities. No other warranty, expressed or implied, is made as to the conclusions and professional advice included in this report. The samples taken and submitted for laboratory testing, the observations made and the in-situ field testing performed are believed representative of the entire project; however, soil and geologic conditions revealed by excavation may be different than our preliminary findings. If this occurs, the changed conditions must be evaluated by the project soils engineer and geologist and design(s) adjusted as required or alternate design(s) recommended. This report is issued with the understanding that it is the responsibility of the owner, or of his/her representative, to ensure that the information and recommendations contained herein are brought to the attention of the architect and/or project engineer and incorporated into the plans, and the necessary steps are taken to see that the contractor and/or subcontractor properly implements the recommendations in the• field. The contractor and/or subcontractor should notify the owner if they consider any of the recommendations presented herein to be unsafe. The findings of this report are valid as of the present date. However, changes in the conditions of a property can and do occur with the passage of time, whether they be due to natural processes or the works of man on this or adjacent properties. In addition, changes in applicable or appropriate standards may occur, whether they result from legislation or the broadening of knowledge. Accordingly, the findings of this report may be invalidated wholly or partially by changes outside our control. Project No. 133023-03 Page 12 February 3, 2016 A FFENDIX A References American Society of Civil Engineers (ASCE), 2013, Minimum design loads for buildings and other structures, ASCE/SEI 7-10, Third Printing, 2013. California Building Standards Commission (CBSC), 2013a, California Building Code, California Code of Regulations, Title 24, Part 2, Volume 1 and 2 of 2 (based on the 2012 International Building Code). CBSC, 2013b, California Residential Building Code, California Code of Regulations, Title 24, Part 2.5,(based on the 2012 International Residential Code). CBSC, 2013c, California Green Building Standards Code, California Code of Regulations, Title 24, Part 11. GeoSoils, Inc., 2002, Geotechnical evaluation of the Robertson Ranch Property, City of Carlsbad, San Diego County, California, W.O. 3098-Al-SC, dated January 29, 2002. GeoSoils, Inc., 2004, Updated geotechnical evaluation of the Robertson Ranch property, Carlsbad, San Diego County, California, W.O. 3098-A2-SC, dated September 20, 2004. GeoSoils, Inc., 2010, Updated geotechnical investigation for Robertson Ranch West Village, Carlsbad, San Diego County, California, W.O. 6145-A-SC, dated October 10, 2010. GeoSoils, Inc., 2011, Supplement to the updated geotechnical investigation for Rancho Costera (formerly Robertson Ranch West Village), Carlsbad, San Diego County, California, W.O. 6145-Al-SC, dated June 6. GeoSoils, Inc., 2012, Preliminary geotechnical review of "vesting master tentative map for Rancho Costera," 40-scale plans, sheets 1 through 21, Job No. 101307, Revised May 1, 2012, by O'Day Consultants, W.O. 6145-A9-SC, dated May 24, 2012. GeoSoils, Inc., 2013, Addendum to the updated and supplemental geotechnical investigations for Rancho Costera (formerly Robertson Ranch West Village), Carlsbad, San Diego County, California, W.O. 6145-A1O-SC, dated July 16, 2013. LGC Valley, Inc., 2014a, Geotechnical and environmental recommendations for Robertson Ranch West, Carlsbad Tract No. 13-03, Carlsbad, California, Project Number 133023-03, dated April 29, 2014. LGC Valley, Inc., 2014b, Change of geotechnical consultant, Robertson Ranch West Project, Carlsbad Tract No. 13-0, Carlsbad, California, Project No. 133023-03, dated May 6, 2014. LGC Valley, Inc., 2015a, Preliminary foundation design for the single-family residential structures, Planning Areas PA-3, PA-5, PA-6, PA-9, PA-b, and PA-13, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 1.33023-06, dated April 14, 2015. Project No. 133023-03 Page A-] February 3, 2016 References (continued) LGC Valley, Inc., 2015b, Preliminary Review of Building Setbacks for the Proposed Residential Planning Areas 3, 5, 6, 9, 10, and 13, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-03, dated February 27, 2015, revised June 24, 2015. LGC Valley, Inc., 2015c, Deepened Footing Recommendation of Building Foundation Adjacent to Proposed Nexus eWater Recycler System, Planning Areas PA-3, PA-5, PA-6, PA-9, PA-10, and PA-13, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-03, dated July 23, 2015. LGC Valley, Inc., 2015d, Geotechnical Post-Tension Foundation Plan Review for The Vistas Development within Planning Area 6 (PA-6), Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023706, dated August 4, 2015. LGC Valley, Inc., 2015e, Geotechnical Post-Tension Foundation Plan Review for The Vistas Development within Planning Area 6 (PA-6), Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-06, dated October 21, 2015. LGC Valley, Inc., 2015f, Geotechnical Post-Tension Foundation Plan Review for The Terraces Development within Planning Areas 9 and 10 (PA-9 and PA- 10), Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-06, dated November 23, 2015. LGC Valley, Inc., 2015g, Presaturation Recommendations Concerning the Proposed Single-Family Residential Structures of The Vistas Development, Lots 1 through 23 of Planning Area PA- 13 and Lots 158 through 244 of Planning Area PA-6, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-06, dated December 2, 2015. LGC Valley, Inc., 2015h, Presaturation Recommendations Concerning the Proposed Single-Family Residential Structures, The Bluffs, Lots 25 through 60 of Planning Area PA-5, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-06, dated December 9, 2015. LGC Valley, Inc., 2015i, Presaturation Recommendations Concerning the Proposed Single-Family Residential Structures, The Terraces, Lots 252 through 326 of Planning Areas PA-9 and PA- 10, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023- 06, dated December 9, 2015. LGC Valley, Inc., 2015j, Geotechnical Post-Tension Foundation Plan Review for The Bluffs Development within Planning Area 5 (PA-5), Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-06, dated December 22, 2015. LGC Valley, Inc., 2016a, Updated Corrosivity Results, Planning Areas PA-5, PA-9, and PA-b, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-09, dated January 27, 2016. LGC Valley, Inc., 2016b, Geotechnical Post-Tension Foundation Plan Review for The Terraces Development within Planning Areas 9 and 10 (PA-9 and PA-b), Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-11, dated February 1, 2016. Project No. 133023-03 Page A-2 February 3, 2016 References (continued) Nexus eWater, 2015, Recycler System Standard Drawings, 9 Sheets, dated April 30, 2015. O'Day Consultants, 2014a, Vesting tentative map for Carlsbad Tract No. 13-03-2, 23 Sheets, dated January 16, 2014. O'Day Consultants, 2014b, Grading plans for Rancho Costera, Robertson Ranch West Village, Carlsbad Tract No. 13-03, Drawing No. 480-3A, 44 Sheets, dated August 25, 2014. Post-Tensioning Institute, 2006, Design of post tensioned slabs-on-ground, Third Addition, Addendum 1 dated May 2007, and Addendum 2 dated May 2008, with errata February 4, 2010. Specialty Steel, 2015, Post-Tension Plans, Details, and General Notes for The Bluffs (PA-5) at Robertson Ranch, Carlsbad, California, Reference No. 4302, dated December 17, 2015. Specialty Steel, 2016, Post-Tension Plans, Details, and General Notes for The Terraces at Robertson Ranch, PA-9 and PA-b, Carlsbad, California, Reference No. 4301, dated November 20, 2015 with Delta 1 Dated January 29, 2016. Suncoast Post-Tension, 2015, Post-Tension Plans, Details, and General Notes for The Vistas at Robertson Ranch, PA-6, Carlsbad, California. Project No. 15-6428, dated August 3, 2015 Delta 1 dated October 8, 2015. United States Geological Survey (USGS), 2008a, "2008 National Seismic Hazard Maps - Fault Parameters" retrieved from: http://geohazards.usgs.gov/cfusion/hazfaults searchlhf search main .cfm USGS, 2008b, "2008 Interactive Deaggregations (Beta)," retrieved from: https://geohazards.usgs.gov/deaggintl2008/ USGS, 2013, U.S. Seismic Design Maps, retrieved from: http://geohazards.usgs.gov/designmaps/us/batch.ph#csv Project No. 133023-03 Page A-3 February 3, 2016 APPENDJX B Laboratory Testing Procedures and Test Results Expansion Index Tests: The expansion potential of selected materials was evaluated by the Expansion Index Test, U.B.C. Standard No. 18-I-B. Specimens are molded under a given compactive energy to approximately the optimum moisture content and approximately 50 percent saturation or approximately 90 percent relative compaction. The prepared 1-inch thick by 4-inch diameter specimens are loaded to an equivalent 144 psf surcharge and are inundated with tap water until volumetric equilibrium is reached. The results of these tests are presented in the table below: Test Representative Lots Sample Description Expansion Expansion Location Index Potential Lot 55 Lots 55-59 Pale brown fine SAND 11 Very Low Lot 60 Lots 60 & 68-70 Medium brown silty to clayey 70 Medium SAND Lot 221 Lots 214-225 Pale orange brown silty fine 34 Low SAND Lot 240 Lots 234-244 Pale gray brown silty fine SAND 10 Very Low Lot 302 Lots 299-307 e Olive green sandy CLAY/clayey 89 Medium SAND Lot 309 Lots 308-3 16 Pale olive green silty to clayey 86 Medium SAND Lot 321 Lots 317-326 Medium olive brown clayey fine 76 Medium SAND Project No. 133023-03 Page B-i February 3, 2016 Laboratory Testing Procedures and Test Results (continued) Soluble Sulfates: The soluble sulfate contents of selected samples were determined by standard geochemical methods (Caltrans 417). The test results are presented in the table below: Test Location Sample Description Sulfate Content (% by Weight) Potential Degree of Sulfate Attack* PA-5 Pale gray silty fine SAND 0.016 Negligible PA-5 Light grayish brown silty fine SAND 0.033 Negligible PA-6 Medium brown silty clayey SAND 0.025 Negligible PA-9 Pale yellow brown clayey SAND 0.071 Negligible PA-10 Olive green silty to sandy CLAY 0.056 Negligible * Per ACT 318R-08 Table 4.3.1. Chloride Content: Chloride content was tested in accordance with Caltrans Test Method (CTM) 422. The results are presented below: Test Location Sample Description Chloride Content (ppm) Potential Degree of Chloride Attack* PA-5 Pale gray silty fine SAND 110 Negligible PA-5 Light grayish brown silty fine SAND 220 Negligible PA-6 Medium brown silty clayey SAND 205 Negligible PA-9 Pale yellow brown clayey SAND 175 Negligible PA-10 Olive green silty to sandy CLAY 230 Negligible * Extrapolation from California Test Method 532, Method for Estimating the Time to Corrosion of Reinforced Concrete Substructures and previous experience I If Project No. 133023-03 Page B-2 February 3, 2016 Laboratory Testing Procedures and Test Results (continued) Minimum Resistivity and pH Tests: Minimum resistivity and pH tests were performed in general accordance with CTM 643 and standard geochemical methods. The electrical resistivity of a soil is a measure of its resistance to the flow of electrical current. As results of soil's resistivity decreases corrosivity increases. The results are presented in the table below: Test Sample Description Minimum Resistivity Potential Degree Location (ohms-cm) of Corrosivity* PA-5 Pale gray silty fine SAND 1500 Corrosive PA-5 Light grayish brown silty fine SAND 570 Severely Corrosive PA-6 Medium brown silty clayey SAND 640 Severely Corrosive PA-9 Pale yellow brown clayey SAND 800 Severely Corrosive PA-10 Olive green silty to sandy CLAY 360 Severely Corrosive * NACE Corrosion Basics Project No. 133023-03 Page B-3 February 3, 2016 I CD TRANSMITTAL LETTER To:____________________ Date: / 9X "10/ No.:________ Project: Re: _ cEi-7/if Attn: ,'4z.- 5224€V T. M.: DWG.: We are enclosing ____________________________ blueline sepias origirial drawings or flFor your files OFor your proposal lFor your review and approval DPer your request flTransmitted vie DMsjl O For information Oparcel Post []Please sign-copies and return to our office ,ick up by Li FAX Remarks: DOelivered by ,L2 i-i2? Lo 35z d..~. ~WIAI_ &CIY 2710 Loker Avenue West Suite 100 Carlsbad, California 92008-6603 Tel: 760.93t7700 Fax: 760.931.8680 E-mail: oday©odayconsultantscom By: Civil gineering Planning PrOcessing Surveying LGC Valley, Inc. Geotechnical Consulting AS-GRADED REPORT OF ROUGH-GRADING, LOTS 59, 60, 216-225, 234-244, 299-301, 308-310, AND 320-324, PLANNING AREAS PA-S, PA-6, AND PA-9&10, ROBERTSON RANCH, CARLSBAD TRA CT NO.13-03, CARLSBAD, CALIFORNIA Project No. 133023-03 Dated: February 3, 2016 Prepared For: Toll Brothers 725 Town and Country Road, Suite 200 Orange, California 92868 2420 Grand Avenue, Suite F2 • Vista • CA 92081 (760) 599-7000 • Fax (760) 599-7007 LGC Valley, Inc. Geotechnical Consulting February 3, 2016 Project No. 133023-03 Mr. Greg Deacon Toll Brothers 725 Town and Country Road, Suite 500 Orange, California 92868 Subject: As-Graded Report of Rough Grading, Lots 59, 60, 216 through 225, 234 through 244, 299 through 301, 308 through 310, and 320 through 324, Planning Areas PA-5, PA-6, and PA- 9&10, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California In accordance with the request and authorization of Toll Brothers, LGC Valley, Inc. (LGC) has provided geotechnical services during the rough-grading operations for Lots 59 and 60 of Planning Area PA-S; Lots 216 through 225 and 234 through 244 of Planning Area PA-6; and Lots 299 through 301, 308 through 310, and 320 through 324 of Planning Areas PA-9 and PA-10; part of the Robertson Ranch project (Carlsbad Tract No. 13- 03) located within the City of Carlsbad, California. The accompanying as-graded report of rough-grading summarizes our observations, field and laboratory test results, and the geotechnical conditions encountered during grading of the subject lots. The rough-grading operations for the subject lots were performed in general accordance with previously published project geotechnical reports (Appendix A), geotechnical recommendations made during the course of grading, and the City of Carlsbad grading requirements. It is our professional opinion that the subject lots are suitable for the intended use provided the recommendations included herein and in the project geotechnical reports are incorporated into the fine-grading, design, and construction of the proposed development and associated improvements. As of the date of this report, the rough-grading operations for the subject lots are essentially complete. If you have any questions regarding our report, please contact this office. We appreciate this opportunity to be of service. Respectfully Submitted, LGC Valley, Inc. Randall Wagner, CEG 1612 Senior Project Geologist itEWi)itI lq~ #Z-*- Basil Hattar, GE 2734 Principal Engineer Distribution: (7) Addressee (1) Toll Brothers; Attention Ms. JoAnn Epstine (via e-mail) (1) Toll Brothers; Attention Mr. Kevin Brickley (via e-mail) (1) Toll Brothers; Attention Mr. Mike Steffen (via e-mail) 2420 Grand Avenue, Suite F2 • Vista • CA 92081 (760) 599-7000 • Fax (760) 599-7007 TABLE OF CONTENTS Section 1.0 INTRODUCTION ......................................................................................................................................... 1 2.0 SUMMARY OF ROUGH-GRADING OPERA TIONS ................................................................................. 2 2.1 As-Graded Conditions.......................................................................................................................2 2.2 Site Preparation and Removals ......................................................................................................... 3 2.3 Stability Fills.....................................................................................................................................4 2.4 Subdrain Installation.........................................................................................................................4 2.5 Overexcavation of Cut/Fill Transition Conditions ............................................................................4 2.6 Overexcavation of Cut Lots...............................................................................................................5 2.7 Fill Placement and Compaction........................................................................................................5 2.8 Laboratory Testing............................................................................................................................5 2.9 Field Density Testing ........................................................................................................................ 5 2.10 Graded Slopes...................................................................................................................................6 3.0 CONCLUSIONS...........................................................................................................................................7 3.1 General.............................................................................................................................................7 3.2 Summary of Conclusions..................................................................................................................7 4.0 RECOMMENDATIONS..............................................................................................................................9 4.1 Earthwork.........................................................................................................................................9 4.2 Site Preparation ...............................................................................................................................9 4.3 Excavations ......................................................................................................................................9 4.4 Fill Placement and Compaction.....................................................................................................10 4.5 Preliminary Foundation Recommendations ..................................................................................10 4.6 Control of Surface Water and Drainage........................................................................................11 5.0 LIMITATIONS...........................................................................................................................................12 Appendices Appendix A - References Appendix B - Laboratory Testing Procedures and Test Results Project No. 133023-03 Page i February 3, 2016 1.0 INTRODUCTION In accordance with the request and authorization of Toll Brothers, LGC Valley, Inc. (LGC) has provided geotechnical services during the rough-grading operations of Lots 59 and 60 of Planning Area PA-5; Lots 216 through 225 and 234 through 244 of Planning Area PA-6; and Lots 299 through 301, 308 through 310, and 320 through 324 of Planning Areas PA-9 and PA-1 0; part of the Robertson Ranch project (Carlsbad Tract No. 13-03) located within the City of Carlsbad, California. This as-graded report summarizes our observations, field and laboratory test results, and the geotechnical conditions encountered during grading of the subject lots. The subject rough-grading operations were performed in general accordance with previously published project geotechnical reports (Appendix A), geotechnical recommendations made during the course of grading, and the City of Carlsbad grading requirements. As of this date, the rough-grading operations for the subject lots are essentially complete. The Rough Grading Plans for the Robertson Ranch project, prepared by O'Day Consultants (O'Day, 2014b), were utilized as a base map to present the as-graded geotechnical conditions and approximate locations of the field density tests. The As-graded Geoteclmical Map and the Field Density Test Location Map will be provided in the final as-graded report for Robertson Ranch upon completion of all of the rough-grading operations. Lots 59 and 60 of Planning Area PA-5 are located in the western portion of Robertson Ranch along the south side of Glasgow Drive while Lots 216 through 225 and 234 through 244 of Planning Area PA-6 and Lots 299 through 301, 308 through 310, and 320 through 324 of Planning Areas PA-9 and PA-10 are located in the east-central portion of the project along Wadsworth Street, Chase Court and Kenther Court. Ultimately, development of Planning Area PA-5, PA-6, and PA-9 and 10 will include the construction of 36, 87, and 75 single-family residential lots, respectfully; along with associated retaining walls, slopes, storm water retention basins, and adjacent streets. The rough-grading operations for Lots 59 and 60 of Planning Area PA-5; Lots 216 through 225 and 234 through 244 of Planning Area PA-6; and Lots 299 through 301, 308 through 310, and 320 through 324 of Planning Areas PA-9 and PA- 10 were performed as a part of grading operations for the entire Robertson Ranch Development between September 2014 and October 2015. Project No. 133023-03 Page 1 February 3, 2016 2.0 SUMMARY OF ROUGH-GRADiNG OPERATIONS Rough-grading of the subject site began on September 5, 2014 and was essentially completed as of October 22, 2015. The grading operations were performed under the observation and testing services of LGC Valley, Inc. Our field technicians were onsite on a full-time basis during the grading operations while our field geologist was onsite on a periodic basis. The rough-grading operations included: Removal and off-site disposal of vegetation and miscellaneous debris; The removal of potentially compressible soils including colluvium, topsoil, undocumented fill, and weathered soils to competent formational material; Overexcavation of cut/fill transition conditions within the lots; Overexcavation of buried cut/fill transition conditions such that the resulting fill differential beneath the proposed building pads was less than a 3:1 (maximum fill thickness to the minimum fill thickness); Overexcavation of cut lots due to expansive soils; Preparation of areas to receive fill; The placement of subdrains in the canyon bottoms and along the heel of the stability fill keys; Excavation of formational material; and The placement of compacted fill soils creating the graded pads and adjacent slopes. The rough-grading operations consisted of the placement of fill up to approximately 45 feet in depth and cuts up to approximately 20 feet within the subject lots. During the rough-grading operations, remedial grading was also performed so that the fill differentials beneath the proposed building pads were less than a 3:1 (maximum fill thickness to the minimum fill thickness). 2.1 As-Graded Conditions The as-graded conditions encountered during grading of the lots were essentially as anticipated. In the vicinity of the Lots 234 through 244, 299, 308, 309, 323, and 324, minor alluvium and colluvium were encountered on the upper hillsides and small tributary ravines of the main canyon running in a northwest-southeast between Planning Areas PA-6 and PA-9/PA-10 and in the small canyon in the vicinity of Lots 323 and 324. Formational material was encountered on the slopes and at design cut grade below a thin veneer of topsoil and weathered soils on the remainder of the lots. All unsuitable and potentially compressible soils were removed prior to fill placement. This included alluvium, colluvium, undocumented fill (associated with the past agricultural operations), and weathered formational materials. The alluvium, colluvium, and topsoil typically consisted of light brown to brown silty fine sands, sandy clays and clayey sands derived from on-site soils and were found to be very low to highly expansive, porous, and contained scattered organics. Removals of alluvium and colluvium up to approximately 5 to 15 feet in depth were made in the vicinity of Lots 234 through 244, 299, 308, 309, 323, and 324. Removals of the topsoil and weathered formational material that was on the order of 2 to 6 feet were made in the other areas of the site. Project No. 133023-03 Page 2 February 3, 2016 The formational material encountered on the subject lots consisted of the Santiago Formation. The material was found to be massively bedded to cross-bedded silty sandstones and minor clayey sandstones, silty claystones and sandy siltstones. The claystones and siltstones generally were olive green and orange brown, damp to moist, stiff to hard, moderately fractured and sheared. The sandstone generally consisted of light olive green, light brown and pale orange brown (where iron- oxidized stained), damp to moist, dense to very dense, silty very fine to medium grained sandstone. The majority of the Santiago material encountered within Robertson Ranch consisted of silty fine sands. Bedding within the Santiago Formation was highly variable, but overall, generally dipped 2 to 15 degrees to the west-southwest. A zone of two to three minor inactive faults was geologically mapped trending in a north-south direction in the middle of Planning Areas PA-9 and PA- 10. Geologic mapping indicated the faults trended N3 °E to N 16°E steeply dipping 60 to 85 degrees to the west. The faults were only observed within the Santiago Formation and the fault zone appeared to die out to the south. Based on our geologic analysis during the current grading operations and review of the applicable geotechnical reports referenced in Appendix A, it is our professional opinion that the faults are not active; and therefore are not a constraint to development. No groundwater was encountered during the grading of the subject lots. However, unanticipated seepage conditions may occur after the completion of grading and establishment of site irrigation and landscaping. If these conditions should occur, steps to mitigate the seepage should be made on a case-by-case basis. 2.2 Site Preparation and Removals Prior to grading, the site was cleared of light vegetation and other miscellaneous debris and the material was disposed of at an offsite facility. Undocumented fill, topsoil, alluvium, colluvium, and weathered formational material were removed down to competent material (i.e. dense unweathered formational material). Remedial removals on site, below the existing ground surface, ranged from approximately 2 to 20 feet in depth. The thickness of compacted fills placed during this recent rough- grading operation, to achieve design rough grades (or sheet-graded pad elevations), ranged from 0 to approximately 45 feet. Following the remedial removals or overexcavations, areas to' receive fill were scarified approximately 6-inches, moisture-conditioned, as needed, to obtain a near-optimum moisture content and compacted to a minimum 90 percent relative compaction (for fills of approximately 40 feet or less from design grades) or 93 percent relative compaction (for engineered fill below approximately 40 feet from design finish grades), as determined by ASTM Test Method D6938 (i.e. the nuclear gauge method). Project No. 133023-03 Page 3 February 3, 2016 2.3 Stability Fills Stability fills were constructed to stabilize the exposed blocky claystone/siltstone and/or adverse (i.e. out-of-slope) geologic conditions present within the Santiago Formation. The stability fill keys were excavated to a width of approximately 15 feet and a minimum depth of 3 to 5 feet below the toe-of- slope. The keyway bottom was angled at least 2 percent into-the-slope. The stability fill front cuts were excavated near vertical while the back-cuts were excavated at an approximate 1:1 to 1.5 (horizontal to vertical) slope inclinations. Stability fills were excavated along the proposed slopes on: 1) the southwest side Lot 60; 2) the southeast side of Lots 59 and 60; 3) the west side of Lots 216 through 225; 4) the north side of Lots 299 through 301; and 5) the north side of Lots 320 through 323. 2.4 Subdrain Installation Canyon and stability fill subdrains were installed under the observation of a representative of LGC in general accordance with the planned locations of the approved geotechnical report, and the standard details (LGC, 2014a). After the potentially compressible material in the canyons were removed to competent material or when compacted fill was placed over competent material to obtain flow to a suitable outlet location, a subdrain was installed along the canyon bottom. The canyon subdrains consisted of a 6-inch diameter perforated pipe surrounded by a minimum of 9- cubic feet (per linear foot) of crushed 3/4-inch gravel wrapped in Mirafi 140N filter fabric. In addition to the canyon subdrains, subdrains were also installed along the bottom backside of the stability fill keys. The stability fill subdrains consisted of a 4-inch diameter perforated pipe surrounded by a minimum of 3-cubic feet (per linear foot) of clean 3/4-inch gravel wrapped in Mirafi 140N filter fabric. The canyon and stability fill subdrains were placed with a minimum 1-percent fall (2-percent or greater where possible) to a suitable outlet location. The location of the subdrains placed during the mass grading operations for the project were surveyed by the project civil engineer. 2.5 Overexcavation of Cut/Fill Transition Conditions Based on the as-graded conditions, the cut/fill transition condition present within the lots, as shown on the rough grading plans (O'Day, 2014b), were overexcavated a minimum of 5 feet in depth beneath the proposed finish grade surface of the lot. The overexcavation extended to a distance of at least 10 feet outside the planned building limits. Lots that were overexcavated due to the cut/fill transition condition include Lots 244, 300, 301, 310, 322, and 323. During the rough-grading operations, remedial grading was also performed so that the fill differential beneath the proposed building pads was less than a 3:1 (maximum fill thickness to the minimum fill thickness). Project No. 133023-03 Page 4 February 3, 2016 2.6 Overe.xcavation of Cut Lots During the rough-grading operations, the overexcavation of cut lots was performed in order to mitigate potential adverse conditions due to expansive soils. The entire portion of the cut lots were overexcavated a minimum of 5 feet below finish pad grade and replaced with compacted fill having a lower expansion potential. In order to minimize potential ponded ground water conditions on the overexcavation bottom, the bottom was sloped toward the street with a minimum fall of one percent. Cut lots that were overexcavated included Lots 60, 320, and 321. 2.7 Fill Placement and Compaction After processing the areas to receive fill, native soil was generally spread in approximately 8-inch loose lifts, moisture-conditioned as needed to attain near-optimum moisture content, and compacted to at least 90 or 93 percent of the maximum dry density determined in accordance with ASTM Test Method D1557. Fill soils less than 40 feet below the design finish grades were compacted to a minimum 90 percent relative compaction while fill soils greater than 40 feet below the design finish grades were compacted to a minimum 93 percent relative compaction. Compaction was achieved by use of heavy-duty construction equipment. Areas of fill in which either field density tests indicated less than 90 or 93 percent relative compaction or the soils exhibited nonuniformity and/or showed an inadequate or excessive moisture content, were reworked, recompacted, and retested until a minimum 90 or 93 percent relative compaction and near-optimum moisture content was achieved. 2.8 Laboratory Testing Maximum dry density tests of representative on-site soils were performed (by others during the previous investigation and by LGC during the current rough-grading operations) in general accordance with ASTM Test Method D1557. Expansion potential, soluble sulfate content, and corrosion testing of representative finish grade soils within the subject lots were performed. Based on the laboratory testing, Lots 59 and 234 through 244 have a very low expansion potential; Lots 216 through 225 have a low expansion potential; and Lots 60, 299 through 301, 308 through 310, and 320 through 324 have a medium expansion potential. Laboratory testing also indicated that the near surface soils have a negligible soluble sulfate content; are corrosive to severely corrosive to buried metals based on the minimum soil resistivity values; and are corrosive to buried metals and reinforcing steel in concrete based on the chloride concentrations. The laboratory test results are presented in Appendix B. 2.9 Field Density Testin' Field density testing was performed using the Nuclear-Gauge Method (ASTM Test Method D6938). The approximate test locations and the results of the field density tests will be provided in the final as-graded report for Robertson Ranch upon completion of the rough grading operations. The field density testing was performed in general accordance with the applicable ASTM standards Project No. 133023-03 Page 5 February 3, 2016 and the cur-rent standard of care in the industry. In-situ soil density testing is intended to verify the effectiveness of the earthmoving operation in general and is performed on a spot-check basis; as such, some variations in relative compaction should be expected from the results documented herein. 2.10 Graded Slopes Manufactured fill slopes within the subject lots were surveyed by the civil engineer and constructed with slope inclinations of 2:1 (horizontal to vertical) or flatter. Permanent graded fill slopes adjacent to or within the subject areas range from approximately 5 to 50 feet in height. There are no permanently graded cut slopes within or adjacent to the subject areas. The on-site fill slopes are considered grossly and surficially stable from a geotechnical standpoint (under normal irrigation/precipitation patterns) provided the project geotechnical recommendations are incorporated into the fine-grading, post-grading, construction, and post-construction phases of site development. Project No. 133023-03 Page 6 February 3, 2016 3.0 CONCLUSIONS 3.1 General The rough-grading of Lots 59 and 60 of Planning Area PA-5; Lots 216 through 225 and 234 through 244 of Planning Area PA-6; and Lots 299 through 301, 308 through 310, and 320 through 324 of Planning Areas PA-9 and PA-10 of the Robertson Ranch development located within the City of Carlsbad, California was performed in general accordance with the project geotechnical report (LGC, 2014a), geotechnical recommendations made during the course of grading, and the City of Carlsbad grading requirements. It is our professional opinion that the subject lots are suitable for the intended use provided the recommendations of the referenced geotechnical reports (LGC, 2014a and 2015a through 2016b) are incorporated into the design and construction; and that proper landscaping, irrigation, and maintenance programs are implemented. 3.2 Summary of Conclusions The following is a summary of our conclusions concerning the rough-grading of Lots 127 through 149 of Planning Area PA-3: Rough-grading of the lots is essentially complete. Geotechnical conditions encountered during the rough-grading operation were generally as anticipated. The geologic units encountered during the rough-grading of the site consisted of undocumented fill soils, topsoil, colluvium, alluvium, and the Santiago Formation. Unsuitable undocumented fill soils, topsoil, colluvium, alluvium, and desiccated and/or weathered formational material were removed to competent formational material within the limits of grading. Landslides or surficial slope failures were not encountered during the grading operations. No evidence of active faulting was encountered during the rough-grading operations; however, a zone of two to three minor inactive faults was encountered trending in north-south direction in the middle of Planning Areas PA-9 and PA- 10 (i.e. in the vicinity of Lots 310 and 320). Based on our geologic analysis, it is our professional opinion that the faults are not active; and therefore are not a constraint to development. Ground water seepage conditions were not encountered during the subject grading operations. Stability fills were constructed to improve the gross stability of the cut slope exposing fractured and blocky formational material and/or adverse geologic conditions on the site and were excavated in accordance with the project geotechnical recommendations. Stability fills were excavated along the proposed slopes on: 1) the southwest side Lot 60; 2) the southeast side of Lots 59 and 60; 3) the west side of Lots 216 through 225; 4) the north side of Lots 299 through 301; and 5) the north side of Lots 320 through 323. Project No. 133023-03 Page 7 February 3, 2016 Subdrains were placed in the canyon bottom and along the heel of the stability fill keys. The subdrains were (or will be) outletted into suitable storm drain facilities or near the toe-of-slope of the stability fill slopes. The cut/fill transition conditions present within the limits of Lots 244, 300, 301, 310, 322, and 323 were overexcavated a minimum of 5 feet beneath the finish grade surface and to a distance of at least 10 feet outside the planned building limits. Overexcavation of Lots 60, 320, and 321 was performed in order to mitigate potential adverse conditions due to expansive soils. The entire portion of the cut lots were overexcavated a minimum of 5 feet below finish pad grade and replaced with compacted fill having a lower expansion potential. During the rough-grading operations, remedial grading was performed so that the fill differential beneath the proposed building pads was less than a 3:1 (maximum fill thickness to the minimum fill thickness). Fill soils were derived from on-site soils. Where tested, the fill soils within the site were compacted at least a 90 or 93 percent relative compaction (based on ASTM Test Method D1557) and near-optimum moisture content in accordance with the recommendations of the project geotechnical report (LGC, 2014a) and the requirements of the City of Carlsbad. Fill soils less than 40 feet below the design finish grades were compacted to a minimum 90 percent relative compaction while fill soils greater than 40 feet below the design finish grades were compacted to a minimum 93 percent relative compaction. Due to the dense nature of the on-site soils, it is our professional opinion that the liquefaction hazard at the site is considered low. Representative testing of the finish grade soils on the building pads of the subject lots indicated that the near-surface soils on Lots 59 and 234 through 244 have a very low expansion potential; Lots 216 through 225 have a low expansion potential; and Lots 60, 299 through 301, 308 through 310, and 320 through 324 have a medium expansion potential. The test results are presented in Appendix B. The potential for soluble sulfate attack on concrete in contact with the finish grade soils of the subject lots is considered negligible based on ACT Criteria (ACT 318R-05 Table 4.3.1). The soluble sulfate content test results are included in Appendix B. Laboratory testing of representative soil samples indicated that the near surface soils are corrosive to severely corrosive to buried metals. The laboratory test results are presented in Appendix B. It is our professional opinion that the slopes of the development are considered to be grossly and surficially stable, as constructed, under normal irrigation/precipitation patterns, provided the recommendations in the project geotechnical reports are incorporated into the post-grading, construction and post-construction phases of site development. Project No. 133023-03 Page 8 February 3, 2016 4.0 RECOMMENDATIONS 4.1 Earthwork We anticipate that future earthwork at the site will consist of site preparation, fine-grading, utility trench excavation and backfill, retaining wall backfill, and street/driveway and parking area pavement section preparation and compaction. We recommend that the earthwork on site be performed in accordance with the geotechnical recommendations presented in the project preliminary geotechnical report (LGC, 2014a) and the City of Carlsbad grading requirements. 4.2 Site Preparation During future grading (if any), the areas to receive structural fill or engineered structures should be cleared of surface obstructions, potentially compressible material (such as desiccated fill soils or weathered formational material), and stripped of vegetation. Vegetation and debris should be removed and properly disposed of off-site. Holes resulting from removal of buried obstructions that extend below finish site grades should be replaced with suitable compacted fill material. Areas to receive fill and/or other surface improvements should be scarified to a minimum depth of 12 inches, brought to optimum moisture condition, and recompacted to at least 90 percent relative compaction (based on ASTM Test Method D1557). If the length of time between the completion of grading and the construction of the development is longer than six months, we recommend that the building pads be evaluated by the geotechnical consultant and, if needed, the finish grade soils on the building pads should be scarified a minimum of 12 inches, moisture-conditioned to optimum moisture-content and recompacted to a minimum 90 percent relative compaction (based on ASTM Test Method D1557). 4.3 Excavations Excavations of the on-site materials may generally be accomplished with conventional heavy-duty earthwork equipment. It is not anticipated that blasting will be required or that significant quantities of oversized rock (i.e. rock with maximum dimensions greater than 8 inches) will be generated during future grading. However, localized cemented zones within the cut areas may be encountered on the site that may require heavy ripping and/or removal. If oversized rock is encountered, it should be placed in accordance with the project geotechnical recommendations (LGC, 2014a), hauled offsite, or placed in non-structural or landscape areas. Temporary excavations maybe cut vertically up to five feet. Excavations over five feet should be slot- cut, shored, or cut to a 1:1 (horizontal to vertical) slope gradient. Surface water should be diverted away from the exposed cut, and not be allowed to pond on top of the excavations. Temporary cuts should not be left open for an extended period of time. Planned temporary conditions should be reviewed by the geotechnical consultant in order to reduce the potential for sidewall failure. The geotechnical consultant may provide recommendations for controlling the length of sidewall exposed. Project No. 133023-03 Page 9 February 3, 2016 4.4 Fill Placement and Compaction The on-site soils are generally suitable for use as compacted fill provided they are free or organic material, debris, and rock fragments larger than 8 inches in maximum dimension. We do not recommend that high or very high expansive soils be utilized as fill for the building pads or as retaining wall backfill. All fill soils should be brought to 2-percent over the optimum moisture content and compacted in uniform lifts to at least 90 percent relative compaction based on the laboratory maximum dry density (ASTM Test Method D1557). The optimum lift thickness required to produce a uniformly compacted fill will depend on the type and size of compaction equipment used. In general, fill should be placed in lifts not exceeding 8 inches in compacted thickness. Placement and compaction of fill should be performed in general accordance with current City of Carlsbad grading ordinances, sound construction practices, and the project geotechnical recommendations. If import soils are to be used as fill, they should be: 1) essentially free from organic matter and other deleterious substances; 2) contain no materials over 6 inches in maximum dimension; 3) have a very low to low expansion potential (i.e. an Expansion Index ranging from 0 to 50); and 4) have a negligible sulfate content. Representative samples of the desired import source should be given to the Geotechnical Consultant at least 48 hours (2 working days) before importing grading begins so that its suitability can be determined and appropriate tests performed. 4.5 Foundation Recommendations The preliminary foundation design recommendations applicable to the construction of the residential structures on the subject lots were previously provided in the our letter report entitled "Preliminary Foundation Design for the Single-Family Residential Structures, Planning Areas PA-3, PA-S, PA-6, PA-9, PA-10, and PA-13, Robertson Ranch", dated April 14, 2015 (LGC, 2015a) and our letter entitled "Deepened Footing Recommendation of Building Foundation Adjacent to Proposed Nexus eWater Recycler System, Planning Areas PA-3, PA-5, PA-6, PA-9, PA-b, and PA-13, Robertson Ranch" dated July 23, 2015 (LGC, 2015c). The previous recommendations remain applicable for the design of the proposed structures on the subject lots. - Based on the expansion potential and corrosion laboratory testing of representative soils on the subject lots, Lots 59 and 234 through 244 have a very low expansion potential; Lots 216 through 225 have a low expansion potential; and Lots 60, 299 through 301, 308 through 310, and 320 through 324 have a medium expansion potential. The finish grade soils on these lots are considered to have negligible sulfate content and are corrosive to severely corrosive to buried metals. The results of the expansion potential and corrosion testing are presented in Appendix B. Project No. 133023-03 Page 10 February 3, 2016 4. 6 Control of Surface Water and Drainage Surface drainage should be carefully taken into consideration during fine-grading, landscaping, and building construction. Positive drainage of surface water away from structures is very important. No water should be allowed to pond adjacent to buildings or the top of slopes. Positive drainage may be accomplished by providing drainage away from buildings at a gradient of at least 2 percent for a distance of at least 5 feet, and further maintained by a swale of drainage path at a gradient of at least 1 percent. Where limited by 5-foot side yards, drainage should be directed away from foundations for a minimum of 3 feet and into a collective swale or pipe system. Where necessary, drainage paths may be shortened by use of area drains and collector pipes. Eave gutters also help reduce water infiltration into the subgrade soils if the downspouts are properly connected to appropriate outlets. The impact of heavy irrigation or inadequate runoff gradient can create perched water conditions, resulting in seepage or shallow groundwater conditions where previously none existed. Maintaining adequate surface drainage and controlled irrigation will significantly reduce the potential for nuisance-type moisture problems. To reduce differential earth movements (such as heaving and shrinkage due to the change in moisture content of foundation soils, which may cause distress to a structure or improvement), the moisture content of the soils surrounding the structure should be kept as relatively constant as possible. All area drain inlets should be maintained and kept clear of debris in order to function properly. Rerouting of site drainage patterns and/or installation of area drains should be performed, if necessary. A qualified civil engineer or a landscape architect should be consulted prior to rerouting of drainage. Project No. 133023-03 Page 11 February 3, 2016 5.0 LIMITATIONS Our services were performed using the degree of care and skill ordinarily exercised, under similar circumstances, by reputable engineers and geologists practicing in this or similar localities. No other warranty, expressed or implied, is made as to the conclusions and professional advice included in this report. The samples taken and submitted for laboratory testing, the observations made and the in-situ field testing performed are believed representative of the entire project; however, soil and geologic conditions revealed by excavation may be different than our preliminary findings. If this occurs, the changed conditions must be evaluated by the project soils engineer and geologist and design(s) adjusted as required or alternate design(s) recommended. This report is issued with the understanding that it is the responsibility of the owner, or of his/her representative, to ensure that the information and recommendations contained herein are brought to the attention of the architect and/or project engineer and incorporated into the plans, and the necessary steps are taken to see that the contractor and/or subcontractor properly implements the recommendations in the field. The contractor and/or subcontractor should notify the owner if they consider any of the recommendations presented herein to be unsafe. The findings of this report are valid as of the present date. However, changes in the conditions of a property can and do occur with the passage of time, whether they be due to natural processes or the works of man on this or adjacent properties. In addition, changes in applicable or appropriate standards may occur, whether they result from legislation or the broadening of knowledge. Accordingly, the findings of this report may be invalidated wholly or partially by changes outside our control. Project No. 133023-03 Page 12 February 3, 2016 APPENDIX A References American Society of Civil Engineers (ASCE), 2013, Minimum design loads for buildings and other structures, ASCE/SEI 7-10, Third Printing, 2013. California Building Standards Commission (CBSC), 2013a, California Building Code, California Code of Regulations, Title 24, Part 2, Volume 1 and 2 of 2 (based on the 2012 International Building Code). CBSC, 2013b, California Residential Building Code, California Code of Regulations, Title 24, Part 2.5,(based on the 2012 International Residential Code). CBSC, 2013c, California Green Building Standards Code, California Code of Regulations, Title 24, Part 11. GeoSoils, Inc., 2002, Geotechnical evaluation of the Robertson Ranch Property, City of Carlsbad, San Diego County, California, W.O. 3098-Al-SC, dated January 29, 2002. GeoSoils, Inc., 2004, Updated geotechnical evaluation of the Robertson Ranch property, Carlsbad, San Diego County, California, W.O. 3098-A2-SC, dated September 20, 2004. GeoSoils, Inc., 2010, Updated geotechnical investigation for Robertson Ranch West Village, Carlsbad, San Diego County, California, W.O. 6145-A-SC, dated October 10, 2010. GeoSoils, Inc., 2011, Supplement to the updated geotechnical investigation for Rancho Costera (formerly Robertson Ranch West Village), Carlsbad, San Diego County, California, W.O. 6145-Al-SC, dated June 6. GeoSoils, Inc., 2012, Preliminary geotechnical review of "vesting master tentative map for Rancho Costera," 40-scale plans, sheets 1 through 21, Job No. 101307, Revised May 1, 2012, by O'Day Consultants, W.O. 6145-A9-SC, dated May 24, 2012. GeoSoils, Inc., 2013, Addendum to the updated and supplemental geotechnical investigations for Rancho Costera (formerly Robertson Ranch West Village), Carlsbad, San Diego County, California, W.O. 6145-Al0-SC, dated July 16, 2013. LGC Valley, Inc., 2014a, Geotechnical and environmental recommendations for Robertson Ranch West, Carlsbad Tract No. 13-03, Carlsbad, California, Project Number 133023-03, dated April 29, 2014. LGC Valley, Inc., 2014b, Change of geotechnical consultant, Robertson Ranch West Project, Carlsbad Tract No. 13-0, Carlsbad, California, Project No. 133023-03, dated May 6, 2014. LGC Valley, Inc., 2015a, Preliminary foundation design for the single-family residential structures, Planning Areas PA-3, PA-5, PA-6, PA-9, PA-b, and PA-13, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 1.33023-06, dated April 14, 2015. Project No. 133023-03 Page ,4-1 February 3, 2016 References (continued) LGC Valley, Inc., 2015b, Preliminary Review of Building Setbacks for the Proposed Residential Planning Areas 3, 5, 6, 9, 10, and 13, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-03, dated February 27, 2015, revised June 24, 2015. LGC Valley, Inc., 2015c, Deepened Footing Recommendation of Building Foundation Adjacent to Proposed Nexus eWater Recycler System, Planning Areas PA-3, PA-5, PA-6, PA-9, PA- 10, and PA-13, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-03, dated July 23, 2015. LGC Valley, Inc., 2015d, Geotechnical Post-Tension Foundation Plan Review for The Vistas Development within Planning Area 6 (PA-6), Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-06, dated August 4, 2015. LGC Valley, Inc., 2015e, Geotechnical Post-Tension Foundation Plan Review for The Vistas Development within Planning Area 6 (PA-6), Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-06, dated October 21, 2015. LGC Valley, Inc., 2015f, Geotechnical Post-Tension Foundation Plan Review for The Terraces Development within Planning Areas 9 and 10 (PA-9 and PA-b), Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-06, dated November 23, 2015. LGC Valley, Inc., 2015g, Presaturation Recommendations Concerning the Proposed Single-Family Residential Structures of The Vistas Development, Lots 1 through 23 of Planning Area PA- 13 and Lots 158 through 244 of Planning Area PA-6, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-06, dated December 2, 2015. LGC Valley, Inc., 2015h, Presaturation Recommendations Concerning the Proposed Single-Family Residential Structures, The Bluffs, Lots 25 through 60 of Planning Area PA-S, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-06, dated December 9, 2015. LGC Valley, Inc., 2015i, Presaturation Recommendations Concerning the Proposed Single-Family Residential Structures, The Terraces, Lots 252 through 326 of Planning Areas PA-9 and PA- 10, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023- 06, dated December 9, 2015. LGC Valley, Inc., 2015j, Geotechnical Post-Tension Foundation Plan Review for The Bluffs Development within Planning Area 5 (PA-5), Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-06, dated December 22, 2015. LGC Valley, Inc., 2016a, Updated Corrosivity Results, Planning Areas PA-5, PA-9, and PA-10, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-09, dated January 27, 2016. LGC Valley, Inc., 2016b, Geotechnical Post-Tension Foundation Plan Review for The Terraces Development within Planning Areas 9 and 10 (PA-9 and PA-b), Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-11, dated February 1, 2016. Proj ect No. 133023-03 Page A-2 February 3, 2016 References (continued) Nexus eWater, 2015, Recycler System Standard Drawings, 9 Sheets, dated April 30, 2015. O'Day Consultants, 2014a, Vesting tentative map for Carlsbad Tract No. 13-03-2, 23 Sheets, dated January 16, 2014. O'Day Consultants, 2014b, Grading plans for Rancho Costera, Robertson Ranch West Village, Carlsbad Tract No. 13-03, Drawing No. 480-3A, 44 Sheets, dated August 25, 2014. Post-Tensioning Institute, 2006, Design of post tensioned slabs-on-ground, Third Addition, Addendum 1 dated May 2007, and Addendum 2 dated May 2008, with errata February 4, 2010. Specialty Steel, 2015, Post-Tension Plans, Details, and General Notes for The Bluffs (PA-5) at Robertson Ranch, Carlsbad, California, Reference No. 4302, dated December 17, 2015. Specialty Steel, 2016, Post-Tension Plans, Details, and General Notes for The Terraces at Robertson Ranch, PA-9 and PA-b, Carlsbad, California, Reference No. 4301, dated November 20, 2015 with Delta 1 Dated January 29, 2016. Suncoast Post-Tension, 2015, Post-Tension Plans, Details, and General Notes for The Vistas at Robertson Ranch, PA-6, Carlsbad, California. Project No. 15-6428, dated August 3, 2015 Delta 1 dated October 8, 2015. United States Geological Survey (USGS), 2008a, "2008 National Seismic Hazard Maps - Fault Parameters" retrieved from: hLtp:Hgeohazards.usgs.gov/cfusion/hazfaults search/hf search main .cfm USGS, 2008b, "2008 Interactive Deaggregations (Beta)," retrieved from: https://geohazards.usgs.gov/deaggint/2008/ USGS, 2013, U.S. Seismic Design Maps, retrieved from: hltp:Hgeohazards.usgs.gov/desigmnaps/us/batch.php#csv Project No. 133023-03 Page A-3 February 3, 2016 APPENDJX B Laboratory Testing Procedures and Test Results Expansion Index Tests: The expansion potential of selected materials was evaluated by the Expansion Index Test, U.B.C. Standard No. 18-I-B. Specimens are molded under a given compactive energy to approximately the optimum moisture content and approximately 50 percent saturation or approximately 90 percent relative compaction. The prepared 1-inch thick by 4-inch diameter specimens are loaded to an equivalent 144 psf surcharge and are inundated with tap water until volumetric equilibrium is reached. The results of these tests are presented in the table below: Test Representative Lots Sample Description Expansion Expansion Location Index Potential Lot 55 Lots 55-59 Pale brown fine SAND 11 Very Low Lot 60 Lots 60&68-70 Medium brown silty to clayey 70 Medium SAND Pale orange brown silty fine Lot 221 Lots 214-225 34 Low SAND Lot 240 Lots 234-244 Pale gray brown silty fme SAND 10 Very Low Olive green sandy CLAY/clayey Lot 302 Lots 299-3 07 89 Medium SAND Pale olive green silty to clayey Lot 309 Lots 308-3 16 SAND 86 Medium Lot 321 Lots 3 17-326 Medium olive brown clayey fme 76 Medium SAND Project No. 133023-03 Page B-i February 3, 2016 Laboratory Testink Procedures and Test Results (continued) Soluble Sulfates: The soluble sulfate contents of selected samples were determined by standard geochemical methods (Caltrans 417). The test results are presented in the table below: Test Location Sample Description Sulfate Content (% by Weight) Potential Degree of Sulfate Attack* PA-5 Pale gray silty fine SAND 0.016 Negligible PA-5 Light grayish brown silty fine SAND 0.033 Negligible PA-6 Medium brown silty clayey SAND 0.025 Negligible PA-9 Pale yellow brown clayey SAND 0.071 Negligible PA-10 Olive green silty to sandy CLAY 0.056 Negligible * Per ACT 318R-08 Table 4.3.1. Chloride Content: Chloride content was tested in accordance with Caltrans Test Method (CTM) 422. The results are presented below: Test Location Sample Description Chloride Content (ppm) Potential Degree of Chloride Attack* PA-5 Pale gray silty fine SAND 110 Negligible PA-5 Light grayish brown silty fine SAND 220 Negligible PA-6 Medium brown silty clayey SAND 205 Negligible PA-9 Pale yellow brown clayey SAND 175 Negligible PA-10 Olive green silty to sandy CLAY 230 Negligible * Extrapolation from California Test Method 532, Method for Estimating the Time to Corrosion of Reinforced Concrete Substructures and previous experience Project No. 133023-03 Page B-2 February 3, 2016 Laboratory Testin' Procedures and Test Results (continued) Minimum Resistivity and pH Tests: Minimum resistivity and pH tests were performed in general accordance with CTM 643 and standard geochemical methods. The electrical resistivity of a soil is a measure of its resistance to the flow of electrical current. As results of soil's resistivity decreases corrosivity increases. The results are presented in the table below: Test Sample Description Minimum Resistivity Potential Degree Location (ohms-cm) of Corrosivity* PA-5 Pale gray silty fine SAND 1500 Corrosive PA-5 Light grayish brown silty fine SAND 570 Severely Corrosive PA-6 Medium brown silty clayey SAND 640 Severely Corrosive PA-9 Pale yellow brown clayey SAND 800 Severely Corrosive EPA- Olive green silty to sandy CLAY 360 Severely Corrosive * NACE Corrosion Basics Project No. 133023-03 Page B-3 February 3, 2016 C 0 N S U L T A/N T s TRANSMITTAL LETTER To: -ra// ,6'& S. Date: ,Z. & '2O/Ob No.:______ Project: ,1AkVO CO2e4 Re: ;4/, CcZ6Z' Attn: 52,6V TM.: d72f- ' DWG.: We are enclosing blueline sepias original drawings or DFor your files DFor your review and approval Deer your request DFor information DPleese aign.__copiee and return to our office Remarks: 0 For your proposal DTransmitted via OMail 0 Parcel Post ,ick up by 0 FAX Doelivered by /MO eE42cd62-' zi7 14e- z.o7 32C S/ 322. AA( 5&ctE/ 2710 Loker Avenue West Suite 100 Carlsbad, California 92008-6603 Tel: 760.931.7700 Fax: 760.931.8680 E-mail: oday©odayconsultants.com By: Civil /gineeMg/ Planning Processing Surveying Ali? GONSULTA NTS Civil Engiizeering Surveying February 24, 2016 J.N. 10-1307-1 Grant Clavier City of Carlsbad Public Works Inspector 1635 Faraday Avenue Carlsbad, CA 92008 RE: Rancho Costera Lot 60, PAS; Lots 320, 321, 322 PAlO of MAP CT 13-03-2, MAP NO. 16092 Dear Inspector: Based upon topographic surveys performed by O'Day Consultants on March 27, 2015 Lot 60, May 12, 2015 Lots 320, 321, 322 the rough grading for land development has been completed within standard tolerance (0.10 feet) in accordance with the approved plan, (City of Carlsbad Dwg. No. 480-3A) and that all embankments, cut slopes and pad sizing are as shown on the approved plans for lots 60, 320, 321, 322. We request the release of pads for building permits for lots 60, 320, 321, 322. Very truly yours, O'DAY CONSULTANTS, INC. YZ George Ola~y Project Manager I O:\ProjeotManagers\transmc\101307\PCPA6 Lot 60, PAS; Lots 320, 321, 322 PAIO.doc O'Day Consultants Inc. E-mail: oday@odayconsultanls.coni 2710 Loker Avenue West, Suite 100 Website: www.odaycorisultants.com Carlsbad. California 92010-6609 Tel: 760931.7700 Fax: 760.931 .8680 345 CI) 340 245\ N \<')\ >/\ 346 14 73 \_24-1 -\ L• —\ 22 222 241 223 242 224 243 225 244 250 251 m 00 CT 332 cRESPI JJJ , \ r13 rn, KEN TNER CIS m cm m cq C,4 CIA co CT335 ) I 1) I- CHASE CT 337 336 ul 330 N) 346 339 CT 13-C LGC Valley, Inc. Geotechnical Consulting AS-GRADED REPORT OF ROUGH-GRADING, LOTS 127 THROUGH 149, PLANNING AREA PA-3, ROBERTSON RANCH, CARLSBAD TRACT NO.13-03, CARLSBAD, CALIFORNIA Project No. 133023-03 Dated: January 29,2016 Prepared For: Toll Brothers 725 Town and Country Road, Suite 200 Orange, California 92868 2420 Grand Avenue, Suite F2 • Vista • CA 92081 • (760) 599-7000 • Fax (760) 599-7007 LGC Valley, Inc. Geotechnical Consulting January 29, 2016 Mr. Greg Deacon Toll Brothers 725 Town and Country Road, Suite 500 Orange, California 92868 Project No. 133023-03 Subject: As-Graded Report of Rough Grading, Lots 127 through 149, Planning Area PA-3, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California In accordance with the request and authorization of Toll Brothers, LGC Valley, Inc. (LGC) has provided geotechnical services during the rough-grading operations for Lots 127 through 149 of Planning Area PA-3; part of the Robertson Ranch project (Carlsbad Tract No. 13-03) located within the City of Carlsbad, California. The accompanying as-graded report of rough-grading summarizes our observations, field and laboratory test results, and the geotechnical conditions encountered during grading of the subject lots. The rough-grading operations for the subject lots were performed in general accordance with previously published project geotechnical reports (Appendix A), geotechnical recommendations made during the course of grading, and the City of Carlsbad grading requirements. It is our professional opinion that the subject lots are suitable for the intended use provided the recommendations included herein and in the project geotechnical reports are incorporated into the fine-grading, design, and construction of the proposed development and associated improvements. As of the date of this report, the rough-grading operations for the subject lots are essentially complete. If you have any questions regarding our report, please contact this office. We appreciate this opportunity to be of service. Respectfully Submitted, LGC Valley, Inc. O~W6'~' Randall Wagner, CEG 1612 Senior Project Geologist RKW/BIH o4AL No.181 Q. CRTflEO * ENGINEERING GEOLOGIST ER t:d \1 A174- Basil Hattar, GE 2734 Principal Engineer Distribution: (3) Addressee (1) Toll Brothers; Attention Mr. Marco Meza-Ruiz (via e-mail) (1) Toll Brothers; Attention Mr. Kevin Brickley (via e-mail) 2420 Grand Avenue, Suite F2 • Vista • CA 92081 • (760) 599.7000 • Fax (760) 599-7007 TABLE OF CONTENTS Section Page 1.0 INTRODUCTION ......................................................................................................................................... 1 2.0 SUMMARY OF ROUGH-GRADING OPERA TIONS ................................................................................. 2 2.1 As-Graded Conditions.......................................................................................................................2 2.2 Site Preparation and Removals.........................................................................................................3 2.3 Stability Fills.....................................................................................................................................4 2.4 Subdrain Installation.........................................................................................................................4 2.5 Overexcavation of Cut/Fill Transition Conditions ............................................................................4 2.6 Overexcavation of Cut Lots...............................................................................................................5 2.7 Fill Placement and Compaction........................................................................................................5 2.8 Laboratory Testing............................................................................................................................5 2.9 Field Density Testing........................................................................................................................5 2.10 Graded Slopes...................................................................................................................................6 3.0 CONCLUSIONS...........................................................................................................................................7 3.1 General.............................................................................................................................................7 3.2 Summary of Conclusions..................................................................................................................7 4.0 RECOMMENDATIONS .............................................................................................................................. 9 4.1 Earthwork.........................................................................................................................................9 4.2 Site Preparation ...............................................................................................................................9 4.3 Excavations ......................................................................................................................................9 4.4 Fill Placement and Compaction.....................................................................................................10 4.5 Preliminary Foundation Recommendations ..................................................................................10 4.6 Control of Surface Water and Drainage ........................................................................................ 11 5.0 LIMITATIONS...........................................................................................................................................12 Appendices Appendix A - References Appendix B - Laboratory Testing Procedures and Test Results Project No. 133023-03 Page i January 29, 2016 1.0 INTRODUCTION In accordance with the request and authorization of Toll Brothers, LGC Valley, Inc. (LGC) has provided geotechnical services during the rough-grading operations for Lots 127 through 149 of Planning Area PA-3 of the Robertson Ranch project (Carlsbad Tract No. 13-03) located within the City of Carlsbad, California. This as-graded report summarizes our observations, field and laboratory test results, and the geotechnical conditions encountered during grading of the subject lots. The subject rough-grading operations were performed in general accordance with previously published project geotechnical reports (Appendix A), geotechnical recommendations made during the course of grading, and the City of Carlsbad grading requirements. As of this date, the rough-grading operations for Lots 127 through 149 of PA-3 are essentially complete. The Rough Grading Plans for the Robertson Ranch project, prepared by O'Day Consultants (O'Day, 2014b), were utilized as a base map to present the as-graded geotechnical conditions and approximate locations of the field density tests. The As-graded Geotechnical Map and the Field Density Test Location Map will be provided in the final as-graded report for Robertson Ranch upon completion of all of the rough-grading operations. Lots 127 through 149 of PA-3 are located in the southwestern portion of Robertson Ranch along La Paz Court and a portion of Wellspring Street. Ultimately, development of Planning Area PA-3 will include the construction of 87 single-family residential lots along with associated retaining walls, slopes, storm water retention basins, and adjacent streets. The rough-grading operations for Lots 127 through 149 of PA-3 were performed as a part of grading operations for the entire Robertson Ranch Development between September 2014 and May 2015. Project No. 133023-03 Page] January 29, 2016 2.0 SUMMARY OF ROUGH-GRADING OPERATIONS Rough-grading of the subject site began on September 5, 2014 and was essentially completed as of May 15, 2015. The grading operations were performed under the observation and testing services of LGC Valley, Inc. Our field technicians were onsite on a full-time basis during the grading operations while our field geologist was onsite on a periodic basis. The rough-grading operations included: Removal and off-site disposal of vegetation and miscellaneous debris; The removal of potentially compressible soils including alluvium, colluvium, topsoil, undocumented fill, and weathered soils to competent formational material; Overexcavation of cut/fill transition conditions within the lots; Overexcavation of buried cut/fill transition conditions such that the resulting fill differential beneath the proposed building pads was less than a 3:1 (maximum fill thickness to the minimum fill thickness); Overexcavation of cut lots due to expansive soils; Preparation of areas to receive fill; The placement of subdrains in the canyon bottom and along the heel of the stability fill key; Excavation of formational material; and The placement of compacted fill soils creating the graded pads and adjacent slopes. The rough-grading operations consisted of the placement of fill up to approximately 45 feet in depth and cuts up to approximately 35 feet within the subject lots. During the rough-grading operations, remedial grading was also performed so that the fill differentials beneath the proposed building pads were less than a 3:1 (maximum fill thickness to the minimum fill thickness). 2.1 As-Graded Conditions The as-graded conditions encountered during grading of the lots were essentially as anticipated. In the vicinity of the Lots 146 through 149, alluvium and colluvium were encountered within the lower portion of the canyon running in a northwest-southeast direction while formational material was encountered on the slopes and at design cut grade below a thin veneer of topsoil and weathered soils on the remainder of the lots. All unsuitable and potentially compressible soils were removed prior to fill placement. This included alluvium, colluvium, undocumented fill (associated with the past agricultural operations), and weathered formational materials. The alluvium and colluvium typically consisted of light brown to brown silty fine sands, sandy clays and clayey sands derived from on-site soils and were found to be very low to highly expansive, porous, and contained scattered organics. Removals of alluvium up to approximately 20 feet in depth were made within the northwest-southeast trending canyon in the vicinity of Lots 146 through 149. Removals of the colluvium, on the order of 2 to 6 feet, were made on the middle and lower portions of the hillsides on the site. Project No. 133023-03 Page 2 January 29, 2016 The formational material encountered on the subject lots consisted of the Santiago Formation. The material was found to be massively bedded to cross-bedded silty sandstones and minor clayey sandstones, silty claystones and sandy siltstones. The claystones and siltstones generally were olive green and orange brown, damp to moist, stiff to hard, moderately fractured and sheared. The sandstone generally consisted of light olive green, light brown and pale orange brown (where iron- oxidized stained), damp to moist, dense to very dense, silty very fine to medium grained sandstone. The majority of the Santiago material encountered within Robertson Ranch consisted of silty fine sands. Bedding within the Santiago Formation was highly variable, but overall, generally dipped 2 to 15 degrees to the west-southwest. Three minor inactive faults were geologically mapped in the back-cut of the stability fill on the south side of Lots 135 through 145. The faults generally trend in a northwest-southeast to north- south direction. Two of the faults were steeply dipping to the west and east while the third fault dipped 50 to 60 degrees to the northeast. The faults were only observed within the Santiago Formation and the two steeply dipping faults appeared to die out to the north. The third fault was mapped extending up the back-cut and across Lots 135 through 137 and extending into the open space area west of Lot 135. Based on our geologic analysis during the current grading operations and review of the applicable geotechnical reports referenced in Appendix A, it is our professional opinion that the faults are not active; and therefore are not a constraint to development. No groundwater was encountered during the grading of the subject lots. However, unanticipated seepage conditions may occur after the completion of grading and establishment of site irrigation and landscaping. If these conditions should occur, steps to mitigate the seepage should be made on a case-by-case basis. 2.2 Site Preparation and Removals Prior to grading, the site was cleared of light vegetation and other miscellaneous debris and the material was disposed of at an offsite facility. Undocumented fill, topsoil, alluvium, colluvium, and weathered formational material were removed down to competent material (i.e. dense unweathered formational material). Remedial removals on site, below the existing ground surface, ranged from approximately 2 to 20 feet in depth. The thickness of compacted fills placed during this recent rough- grading operation, to achieve design rough grades (or sheet-graded pad elevations), ranged from 0 to approximately 45 feet. Following the remedial removals or overexcavations, areas to receive fill were scarified approximately 6-inches, moisture-conditioned, as needed, to obtain a near-optimum moisture content and compacted to a minimum 90 percent relative compaction (for fills of approximately 40 feet or less from design grades) or 93 percent relative compaction (for engineered fill below approximately 40 feet from design finish grades), as determined by ASTM Test Method D6938 (i.e. the nuclear gauge method). Project No. 133023-03 Page 3 January 29, 2016 2.3 Stability Fills Stability fills were constructed to stabilize the exposed blocky claystone/siltstone and/or adverse (i.e. out-of-slope) geologic conditions present within the Santiago Formation. The stability fill keys were excavated to a width of approximately 15 to 25 feet and a minimum depth of 3 to 5 feet below the toe- of-slope. The keyway bottom was angled at least 2 percent into-the-slope. The stability fill front cuts were excavated near vertical while the back-cuts were excavated at an approximate 1:1 to 1.5 (horizontal to vertical) slope inclinations. A stability fill was excavated along the proposed slope on the south side of Lots 135 through 145. 2.4 Subdrain Installation Canyon and stability fill subdrains were installed under the observation of a representative of LGC in general accordance with the planned locations of the approved geotechnical report, and the standard details (LGC, 2014a). After the potentially compressible material in the canyons were removed to competent material or when compacted fill was placed over competent material to obtain flow to a suitable outlet location, a subdrain was installed along the canyon bottom. The canyon subdrains consisted of a 6-inch diameter perforated pipe surrounded by a minimum of 9- cubic feet (per linear foot) of crushed 3/4-inch gravel wrapped in Mirafi 140N filter fabric. In addition to the canyon subdrains, subdrains were also installed along the bottom backside of the stability fill keys. The stability fill subdrains consisted of a 4-inch diameter perforated pipe surrounded by a minimum of 3-cubic feet (per linear foot) of clean 3/4-inch gravel wrapped in Mirafi 140N filter fabric. The canyon and stability fill subdrains were placed with a minimum 1-percent fall (2-percent or greater where possible) to a suitable outlet location. The location of the subdrains placed during the mass grading operations for the project were surveyed by the project civil engineer. 2.5 Overexcavation of Cut/Fill Transition Conditions Based on the as-graded conditions, the cut/fill transition condition present within the lots, as shown on the rough grading plans (O'Day, 2014b), were overexcavated a minimum of 5 feet in depth beneath the proposed finish grade surface of the lot. The overexcavation extended to a distance of at least 10 feet outside the planned building limits. Lots that were overexcavated due to the cut/fill transition condition include Lots 133 and 135 through 145. During the rough-grading operations, remedial grading was also performed so that the fill differential beneath the proposed building pads was less than a 3:1 (maximum fill thickness to the minimum fill thickness). Project No. 133023-03 Page 4 January 29, 2016 2.6 Overexcavation of Cut Lots During the rough-grading operations, the overexcavation of cut lots was performed in order to mitigate potential adverse conditions due to expansive soils. The entire portion of the cut lots were overexcavated a minimum of 5 feet below finish pad grade and replaced with compacted fill having a lower expansion potential. In order to minimize potential ponded ground water conditions on the overexcavation bottom, the bottom was sloped toward the street with a minimum fall of one percent. Cut lots that were overexcavated included Lots 127 through 132. 2.7 Fill Placement and Compaction After processing the areas to receive fill, native soil was generally spread in approximately 8-inch loose lifts, moisture-conditioned as needed to attain near-optimum moisture content, and compacted to at least 90 or 93 percent of the maximum dry density determined in accordance with ASTM Test Method D1557. Fill soils less than 40 feet below the design finish grades were compacted to a minimum 90 percent relative compaction while fill soils greater than 40 feet below the design finish grades were compacted to a minimum 93 percent relative compaction. Compaction was achieved by use of heavy-duty construction equipment. Areas of fill in which either field density tests indicated less than 90 or 93 percent relative compaction or the soils exhibited nonuniformity and/or showed an inadequate or excessive moisture content, were reworked, recompacted, and retested until a minimum 90 or 93 percent relative compaction and near-optimum moisture content was achieved. 2.8 Laboratory Testinj' Maximum dry density tests of representative on-site soils were performed (by others during the previous investigation and by LGC during the current rough-grading operations) in general accordance with ASTM Test Method D1557. Expansion potential, soluble sulfate content, and corrosion testing of representative finish grade soils within the subject lots were performed. Based on the laboratory testing, Lots 127 through 130 and 135 through 145 have a low expansion potential while Lots 131 through 134 and 146 through 149 have a medium expansion potential. Laboratory testing also indicated that the near surface soils have a negligible soluble sulfate content; are corrosive to severely corrosive to buried metals based on the minimum soil resistivity values; and are corrosive to buried metals and reinforcing steel in concrete based on the chloride concentrations. The laboratory test results are presented in Appendix B. 2.9 Field Density Testinji Field density testing was performed using the Nuclear-Gauge Method (ASTM Test Method D6938). The approximate test locations and the results of the field density tests will be provided in the final as-graded report for Robertson Ranch upon completion of the rough grading operations. The field density testing was performed in general accordance with the applicable ASTM standards and the current standard of care in the industry. In-situ soil density testing is intended to verify the Project No. 133023-03 Page 5 January 29, 2016 effectiveness of the earthmoving operation in general and is performed on a spot-check basis; as such, some variations in relative compaction should be expected from the results documented herein. 2.10 Graded Slopes Manufactured fill slopes within the subject lots were surveyed by the civil engineer and constructed with slope inclinations of 2:1 (horizontal to vertical) or flatter. Permanent graded fill slopes adjacent to or within the subject areas range from approximately 5 to 90 feet in height. There are no permanently graded cut slopes within or adjacent to the subject areas. The on-site fill slopes are considered grossly and surficially stable from a geotechnical standpoint (under normal irrigation/precipitation patterns) provided the project geotechnical recommendations are incorporated into the fine-grading, post-grading, construction, and post-construction phases of site development. Project No. 133023-03 Page 6 January 29, 2016 3.0 CONCLUSIONS 3.1 General The rough-grading of Lots 127 through 149 of PA-3 of Robertson Ranch located within the City of Carlsbad, California was performed in general accordance with the project geotechnical report (LGC, 2014a), geotechnical recommendations made during the course of grading, and the City of Carlsbad grading requirements. It is our professional opinion that the subject lots are suitable for the intended use provided the recommendations of the referenced geotechnical reports (LGC, 2014a and 2015a through 2015f) are incorporated into the design and construction; and that proper landscaping, irrigation, and maintenance programs are implemented. 3.2 Summary of Conclusions The following is a summary of our conclusions concerning the rough-grading of Lots 127 through 149 of Planning Area PA-3: Rough-grading of the lots is essentially complete. Geotechnical conditions encountered during the rough-grading operation were generally as anticipated. The geologic units encountered during the rough-grading of the site consisted of undocumented fill soils, topsoil, colluvium, alluvium, and the Santiago Formation. Unsuitable undocumented fill soils, topsoil, colluvium, alluvium, and desiccated and/or weathered formational material were removed to competent formational material within the limits of grading. Landslides or surficial slope failures were not encountered during the grading operations. No evidence of active faulting was encountered during the rough-grading operations; however, three minor inactive faults were encountered in the stability fill back-cut on the south side of Lots 135 through 145; but are not considered a constraint to development. Ground water seepage conditions were not encountered during the subject grading operations. A stability fill was constructed to improve the gross stability of the cut slope exposing fractured and blocky formational material and/or adverse geologic conditions on the site along the south side of Lots 135 through 145. The stability fill key was excavated in accordance with the project geotechnical recommendations. Subdrains were placed in the canyon bottom and along the heel of the stability fill key. The subdrains were (or will be) outletted into suitable storm drain facilities or near the toe-of-slope of the stability fill slopes. The cut/fill transition conditions present within the limits of Lots 133 and 135 through 145 were overexcavated a minimum of 5 feet beneath the finish grade surface and to a distance of at least 10 feet outside the planned building limits. Project No. 133023-03 Page 7 January 29, 2016 Overexcavation of Lots 127 through 132 was performed in order to mitigate potential adverse conditions due to expansive soils. The entire portion of the cut lots were overexcavated a minimum of 5 feet below finish pad grade and replaced with compacted fill having a lower expansion potential. During the rough-grading operations, remedial grading was performed so that the fill differential beneath the proposed building pads was less than a 3:1 (maximum fill thickness to the minimum fill thickness). Fill soils were derived from on-site soils. Where tested, the fill soils within the site were compacted at least a 90 or 93 percent relative compaction (based on ASTM Test Method D1557) and near-optimum moisture content in accordance with the recommendations of the project geotecimical report (LGC, 2014a) and the requirements of the City of Carlsbad. Fill soils less than 40 feet below the design finish grades were compacted to a minimum 90 percent relative compaction while fill soils greater than 40 feet below the design finish grades were compacted to a minimum 93 percent relative compaction. Due to the dense nature of the on-site soils, it is our professional opinion that the liquefaction hazard at the site is considered low. Representative testing of the finish grade soils on the building pads of Lot 127 through 149 indicated that the near-surface soils on Lots 127 through 130 and 135 through 145 have a low expansion potential while Lots 131 through 134 and 146 through 149 have a medium expansion potential. The test results are presented in Appendix B. The potential for soluble sulfate attack on concrete in contact with the finish grade soils of Lots 127 through 149 is considered negligible based on ACT Criteria (ACI 318R-05 Table 4.3.1). The soluble sulfate content test results are included in Appendix B. Laboratory testing of representative soil samples indicated that the near surface soils are corrosive to severely corrosive to buried metals. The laboratory test results are presented in Appendix B. It is our professional opinion that the slopes of the development are considered to be grossly and surficially stable, as constructed, under normal irrigation/precipitation patterns, provided the recommendations in the project geotechnical reports are incorporated into the post-grading, construction and post-construction phases of site development. Project No. 133023-03 Page 8 January 29, 2016 4.0 RECOMMENDATIONS 4.1 Earthwork We anticipate that future earthwork at the site will consist of site preparation, fine-grading, utility trench excavation and backfill, retaining wall backfill, and street/driveway and parking area pavement section preparation and compaction. We recommend that the earthwork on site be performed in accordance with the geotechnical recommendations presented in the project preliminary geotechnical report (LGC, 2014a) and the City of Carlsbad grading requirements. 4.2 Site Preparation During future grading (if any), the areas to receive structural fill or engineered structures should be cleared of surface obstructions, potentially compressible material (such as desiccated fill soils or weathered formational material), and stripped of vegetation. Vegetation and debris should be removed and properly disposed of off-site. Holes resulting from removal of buried obstructions that extend below finish site grades should be replaced with suitable compacted fill material. Areas to receive fill and/or other surface improvements should be scarified to a minimum depth of 12 inches, brought to optimum moisture condition, and recompacted to at least 90 percent relative compaction (based on ASTM Test Method D1557). If the length of time between the completion of grading and the construction of the development is longer than six months, we recommend that the building pads be evaluated by the geotechnical consultant and, if needed, the finish grade soils on the building pads should be scarified a minimum of 12 inches, moisture-conditioned to optimum moisture-content and recompacted to a minimum 90 percent relative compaction (based on ASTM Test Method D1557). 4.3 Excavations Excavations of the on-site materials may generally be accomplished with conventional heavy-duty earthwork equipment. It is not anticipated that blasting will be required or that significant quantities of oversized rock (i.e. rock with maximum dimensions greater than 8 inches) will be generated during future grading. However, localized cemented zones within the cut areas may be encountered on the site that may require heavy ripping and/or removal. If oversized rock is encountered, it should be placed in accordance with the project geotechnical recommendations (LGC, 2014a), hauled offsite, or placed in non-structural or landscape areas. Temporary excavations maybe cut vertically up to five feet. Excavations over five feet should be slot- cut, shored, or cut to a 1:1 (horizontal to vertical) slope gradient. Surface water should be diverted away from the exposed cut, and not be allowed to pond on top of the excavations. Temporary cuts should not be left open for an extended period of time. Planned temporary conditions should be reviewed by the geotechnical consultant in order to reduce the potential for sidewall failure. The geotechnical consultant may provide recommendations for controlling the length of sidewall exposed. Project No. 133023-03 Page 9 January 29, 2016 4.4 Fill Placement and Compaction The on-site soils are generally suitable for use as compacted fill provided they are free or organic material, debris, and rock fragments larger than 8 inches in maximum dimension. We do not recommend that high or very high expansive soils be utilized as fill for the building pads or as retaining wall backfill. All fill soils should be brought to 2-percent over the optimum moisture content and compacted in uniform lifts to at least 90 percent relative compaction based on the laboratory maximum dry density (ASTM Test Method D1557). The optimum lift thickness required to produce a uniformly compacted fill will depend on the type and size of compaction equipment used. In general, fill should be placed in lifts not exceeding 8 inches in compacted thickness. Placement and compaction of fill should be performed in general accordance with current City of Carlsbad grading ordinances, sound construction practices, and the project geotechnica! recommendations. If import soils are to be used as fill, they should be: 1) essentially free from organic matter and other deleterious substances; 2) contain no materials over 6 inches in maximum dimension; 3) have a very low to low expansion potential (i.e. an Expansion Index ranging from 0 to 50); and 4) have a negligible sulfate content. Representative samples of the desired import source should be given to the Geotechnical Consultant at least 48 hours (2 working days) before importing grading begins so that its suitability can be determined and appropriate tests performed. 4.5 Foundation Recommendations The preliminary foundation design recommendations applicable to the construction of the residential structures on Lots 127 through 149 of Planning Area PA-3 were previously provided in the our letter report entitled "Preliminary Foundation Design for the Single-Family Residential Structures, Planning Areas PA-3, PA-5, PA-6, PA-9, PA-b, and PA-13, Robertson Ranch", dated April 14, 2015 (LGC, 2015a) and our letter entitled "Deepened Footing Recommendation of Building Foundation Adjacent to Proposed Nexus eWater Recycler System, Planning Areas PA-3, PA-5, PA-6, PA-9, PA-b, and PA-13, Robertson Ranch" dated July 23, 2015 (LGC, 2015c). The previous recommendations remain applicable for the design of the proposed structures on the subject lots. Based on the expansion potential and corrosion laboratory testing of representative soils on the subject lots, Lots 127 through 130 and 135 through 145 have a low expansion potential while Lots 131 through 134 and 146 through 149 have a medium expansion potential. The finish grade soils on these lots are considered to have a negligible sulfate content and are corrosive to severely corrosive to buried metals. The results of the expansion potential and corrosion testing are presented in Appendix B. Project No. 133023-03 Page 10 January 29, 2016 4.6 Control of Surface Water and Drainaj'e Surface drainage should be carefully taken into consideration during fine-grading, landscaping, and building construction. Positive drainage of surface water away from structures is very important. No water should be allowed to pond adjacent to buildings or the top of slopes. Positive drainage may be accomplished by providing drainage away from buildings at a gradient of at least 2 percent for a distance of at least 5 feet, and further maintained by a swale of drainage path at a gradient of at least 1 percent. Where limited by 5-foot side yards, drainage should be directed away from foundations for a minimum of 3 feet and into a collective swale or pipe system. Where necessary, drainage paths may be shortened by use of area drains and collector pipes. Eave gutters also help reduce water infiltration into the subgrade soils if the downspouts are properly connected to appropriate outlets. The impact of heavy irrigation or inadequate runoff gradient can create perched water conditions, resulting in seepage or shallow groundwater conditions where previously none existed. Maintaining adequate surface drainage and controlled irrigation will significantly reduce the potential for nuisance-type moisture problems. To reduce differential earth movements (such as heaving and shrinkage due to the change in moisture content of foundation soils, which may cause distress to a structure or improvement), the moisture content of the soils surrounding the structure should be kept as relatively constant as possible. All area drain inlets should be maintained and kept clear of debris in order to function properly. Rerouting of site drainage patterns and/or installation of area drains should be performed, if necessary. A qualified civil engineer or a landscape architect should be consulted prior to rerouting of drainage. Project No. 133023-03 Page]] January 29, 2016 5.0 LIMITATIONS Our services were performed using the degree of care and skill ordinarily exercised, under similar circumstances, by reputable engineers and geologists practicing in this or similar localities. No other warranty, expressed or implied, is made as to the conclusions and professional advice included in this report. The samples taken and submitted for laboratory testing, the observations made and the in-situ field testing performed are believed representative of the entire project; however, soil and geologic conditions revealed by excavation may be different than our preliminary findings. If this occurs, the changed conditions must be evaluated by the project soils engineer and geologist and design(s) adjusted as required or alternate design(s) recommended. This report is issued with the understanding that it is the responsibility of the owner, or of his/her representative, to ensure that the information and recommendations contained herein are brought to the attention of the architect and/or project engineer and incorporated into the plans, and the necessary steps are taken to see that the contractor and/or subcontractor properly implements the recommendations in the field. The contractor and/or subcontractor should notify the owner if they consider any of the recommendations presented herein to be unsafe. The findings of this report are valid as of the present date. However, changes in the conditions of a property can and do occur with the passage of time, whether they be due to natural processes or the works of man on this or adjacent properties. In addition, changes in applicable or appropriate standards may occur, whether they result from legislation or the broadening of knowledge. Accordingly, the findings of this report may be invalidated wholly or partially by changes outside our control. Project No. 133023-03 Page 12 January 29, 2016 References American Society of Civil Engineers (ASCE), 2013, Minimum design loads for buildings and other structures, ASCEISEI 7-10, Third Printing, 2013. California Building Standards Commission (CBSC), 2013a, California Building Code, California Code of Regulations, Title 24, Part 2, Volume 1 and 2 of 2 (based on the 2012 International Building Code). CBSC, 2013b, California Residential Building Code, California Code of Regulations, Title 24, Part 2.5,(based on the 2012 International Residential Code). CBSC, 2013c, California Green Building Standards Code, California Code of Regulations, Title 24, Part 11. GeoSoils, Inc., 2002, Geotechnical evaluation of the Robertson Ranch Property, City of Carlsbad, San Diego County, California, W.O. 3098-Al-SC, dated January 29, 2002. GeoSoils, Inc., 2004, Updated geotechnical evaluation of the Robertson Ranch property, Carlsbad, San Diego County, California, W.O. 3098-A2-SC, dated September 20, 2004. GeoSoils, Inc., 2010, Updated geotechnical investigation for Robertson Ranch West Village, Carlsbad, San Diego County, California, W.O. 6145-A-SC, dated October 10, 2010. GeoSoils, Inc., 2011, Supplement to the updated geotechnical investigation for Rancho Costera (formerly Robertson Ranch West Village), Carlsbad, San Diego County, California, W.O. 6145-Al-SC, dated June 6. GeoSoils, Inc., 2012, Preliminary geotechnical review of "vesting master tentative map for Rancho Costera," 40-scale plans, sheets 1 through 21, Job No. 101307, Revised May 1, 2012, by O'Day Consultants, W.O. 6145-A9-SC, dated May 24, 2012. GeoSoils, Inc., 2013, Addendum to the updated and supplemental geotechnical investigations for Rancho Costera (formerly Robertson Ranch West Village), Carlsbad, San Diego County, California, W.O. 6145-A10-SC, dated July 16, 2013. LGC Valley, Inc., 2014a, Geotechnical and environmental recommendations for Robertson Ranch West, Carlsbad Tract No. 13-03, Carlsbad, California, Project Number 133023-03, dated April 29, 2014. LGC Valley, Inc., 2014b, Change of Geotechnical Consultant, Robertson Ranch West Project, Carlsbad Tract No. 13-0, Carlsbad, California, Project No. 133023-03, dated May 6, 2014. LGC Valley, Inc., 2015a, Preliminary foundation design for the single-family residential structures, Planning Areas PA-3, PA-5, PA-6, PA-9, PA-b, and PA-13, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 1.33023-06, dated April 14, 2015. Project No. 133023-03 Page A-i January 29, 2016 References (continued) LGC Valley, Inc., 2015b, Preliminary Review of Building Setbacks for the Proposed Residential Planning Areas 3, 5, 6, 9, 10, and 13, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-03, dated February 27, 2015, revised June 24, 2015. LGC Valley, Inc., 2015c, Deepened Footing Recommendation of Building Foundation Adjacent to Proposed Nexus eWater Recycler System, Planning Areas PA-3, PA-5, PA-6, PA-9, PA- 10, and PA-13, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-03, dated July 23, 2015. LGC Valley, Inc., 2015d, Geotechnical Post-Tension Foundation Plan Review for The Ridge Development within Planning Area 3 (PA-3), Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-06, dated August 4, 2015. LGC Valley, Inc., 2015e, Geotechnical Post-Tension Foundation Plan Review for The Ridge Development within Planning Area 3 (PA-3), Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-06, dated November 4, 2015. LGC Valley, Inc., 2015f, Presaturation Recommendations Concerning the Proposed Single-Family Residential Structures, The Ridge, Lots 63 through 149 of Planning Area PA-3, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-06, dated December 2, 2015. Nexus eWater, 2015, Recycler System Standard Drawings, 9 Sheets, dated April 30, 2015. O'Day Consultants, 2014a, Vesting tentative map for Carlsbad Tract No. 13-03-2, 23 Sheets, dated January 16, 2014. O'Day Consultants, 2014b, Grading plans for Rancho Costera, Robertson Ranch West Village, Carlsbad Tract No. 13-03, Drawing No. 480-3A, 44 Sheets, dated August 25, 2014. Post-Tensioning Institute, 2006, Design of post tensioned slabs-on-ground, Third Addition, Addendum 1 dated May 2007, and Addendum 2 dated May 2008, with errata February 4, 2010. Suncoast Post-Tension, 2015, Post-Tension Plans, Details, and General Notes for The Ridge at Robertson Ranch, PA-3, Carlsbad, California. Project No. 15-6429, dated Delta 1 - October 29, 2015. United States Geological Survey (USGS), 2008a, 112008 National Seismic Hazard Maps - Fault Parameters" retrieved from: http://geohazards.usgs.gov/cfusionlhazfaultssearchlhf search_main.cthi USGS, 2008b, "2008 Interactive Deaggregations (Beta)," retrieved from: https://geohazards.usgs.gov/deaggint/2008/ USGS, 2013, U.S. Seismic Design Maps, retrieved from: http://geohazards.usgs.gov/designmaps/us[batch.php#csv Project No. 133023-03 Page A-2 January 29, 2016 APPENDIX B Laboratory Testing Procedures and Test Results Expansion Index Tests: The expansion potential of selected materials was evaluated by the Expansion Index Test, U.B.C. Standard No. 18-I-13. Specimens are molded under a given compactive energy to approximately the optimum moisture content and approximately 50 percent saturation or approximately 90 percent relative compaction. The prepared 1-inch thick by 4-inch diameter specimens are loaded to an equivalent 144 psf surcharge and are inundated with tap water until volumetric equilibrium is reached. The results of these tests are presented in the table below: Test Representative Lots Sample Description Expansion Expansion Location Index Potential Lot 139 127-130& 135-141 Light brown silty to clayey fine 43 Low SAND Lot 145 142-145 Light brown silty to clayey fine 41 Low SAND Lot 148 131-134& 146-149 Light brown silty to clayey fine 51 Medium SAND Soluble Sulfates: The soluble sulfate contents of selected samples were determined by standard geochemical methods (Caltrans 417). The test results are presented in the table below: Sulfate Content Potential Degree Sample Description of Sulfate (% by Weight) Aftack* Light brown silty fine SAND 0.011 Negligible Light grayish brown silty fine 0.033 Negligible SAND Pale yellow brown silty fine 0.071 Negligible SAND * Per ACT 318R-08 Table 4.3.1. Project No. 133023-03 Page B-] January 29, 2016 Chloride Content: Chloride content was tested in accordance with Caltrans Test Method (CTM) 422. The results are presented below: Sample Description Chloride Content (ppm) Potential Degree of Chloride Attack* Light brown silty fine SAND 270 Negligible Light grayish brown silty fine SAND 220 Negligible Pale yellow brown silty fine SAND 175 Negligible * Extrapolation from California Test Method 532, Method for Estimating the Time to Corrosion of Reinforced Concrete Substructures and previous experience Minimum Resistivity and pH Tests: Minimum resistivity and pH tests were performed in general accordance with CTM 643 and standard geochemical methods. The electrical resistivity of a soil is a measure of its resistance to the flow of electrical current. As results of soil's resistivity decreases corrosivity increases. The results are presented in the table below: Sample Description Minimum Resistivity Potential Degree (ohms-cm)) of Corrosivity* Light brown silty fine SAND 1200 Moderately Corrosive Light grayish brown silty fine 570 Corrosive SAND Pale yellow brown silty fine 800 Corrosive SAND * NACE Corrosion Basics -I Project No. 133023-03 Page B-2 January 29, 2016 C 0 N S U L T A N T S Civil Engineering • Surveying February 2, 2016 J.N. 10-1307-1 Grant Clavier City of Carlsbad Public Works Inspector 1635 Faraday Avenue Carlsbad, CA 92008 RE: Rancho Costera Lots 127-149 of MAP CT 13-03 PA 3 Dear Inspector: Based upon topographic surveys performed by O'Day Consultants on March 27, 2015 Lots 127-145, 147-149, January 26, 2016 Lot 146, the rough grading for land development has been completed within standard tolerance (0.10 feet) in accordance with the approved plan, (City of Carlsbad Dwg. No. 480-3A) and that all embankments, cut slopes and pad sizing are as shown on the approved plans for lots 127 through 149. We request the release of pads for building permits for lots 127 through 149. 1Iw :- V -. Very truly yours, X", 'DAY CONSULTANTS, INC. *Jiieorge Project Manager 0 :\ProjectManagers\transmc\1O 1307\PCPA6 Lot 127-149 .doc O'Day Consultants Inc. E-mail: oday@odayconsultants.com 2710 Loker Avenue West, Suite 100 Websito: www.odayconsuitants.com Carlsbad, California 92010-6609 Tel: 760931.7700 Fax: 760,931.8680 1. VIFY1 JJ7II F 1 %V1t1J II1EL L1PJ Wfgr RANCH ST LGC Valley, Inc. Geotechnical Consulting AS-GRADED REPORT OF ROUGH-GRADING, LOTS 1 THROUGH 24 OF PA-13, PA-3 AND PA-6 MODEL LOT COMPLEXES, AND PA-4 RECREATION CENTER, ROBERTSON RANCH, CARLSBAD TRA CT NO.13-03, CARLSBAD, CALIFORNIA Project No. 133023-03 Dated: August 7, 2015 Prepared For: Toll Brothers 725 Town and Country Road, Suite 200 Orange, California 92868 2420 Grand Avenue, Suite F2 • Vista • CA 92081 • (760) 599-7000 • Fax (760) 599-7007 LGC Valley, Inc. Geotechnical Consulting August 7, 2015 Mr. Peter Kim Toll Brothers 725 Town and Country Road, Suite 500 Orange, California 92868 Project No. 133023-03 Subject: As-Graded Report of Rough-Grading, Lots 1 Through 24 of PA-13, PA-3 and PA-6 Model Lot Complexes, and PA-4 Recreation Center, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, California In accordance with your request and authorization, LGC Valley, Inc. (LGC) has provided geotechnical services during the rough-grading operations for Lots 1 through 24 of Planning Area PA- 13, Lots 101 through 104 of Planning Area PA-3, Lots 206 through 211 of Planning Area PA-6, and the Recreation Center of Planning Area PA-4 of the Robertson Ranch project (Carlsbad Tract No. 13-03) located within the City of Carlsbad, California. Lots 101 through 104 of Planning Area PA-3 and Lots 206 through 211 of Planning Area PA-6 will be the model lot complexes for the respective planning areas. Planning Area PA-4 consists of a sheet-graded pad that ultimately will contain the Robertson Ranch recreation center. The accompanying as-graded report of rough-grading summarizes our observations, field and laboratory test results, and the geotechnical conditions encountered during grading of the subject site. The rough-grading operations for the subject areas were performed in general accordance with previously published project geotechnical reports (Appendix A), geotechnical recommendations made during the course of grading, and the City of Carlsbad grading requirements. It is our professional opinion that the subject site is suitable for its intended use provided the recommendations included herein and in the project geotechnical reports are incorporated into the fine-grading, design, and construction of the proposed development and associated improvements. As of the date of this report, the rough-grading operations for the subject areas of the Robertson Ranch project are essentially complete. If you have any questions regarding our report, please contact this office. We appreciate this opportunity to be of service. Respectfully Submitted, LGC Valley, Inc. omk~r' Randall Wagner, CEG 1612 Senior Project Geologist RKW/BIH Wo.1i2 •. .- a. GER11FIED * £GfNEEPIUG GEOWisT j \ #00- Basil Hattar, GE 2734 Principal Engineer Distribution: (1) Addressee (8) Toll Brothers; Attention Ms. JoAnn Epstine 2420 Grand Avenue, Suite F2 • Vista • CA 92081 (760) 599-7000 • Fax (760) 599-7007 TABLE OF CONTENTS Section Page 1.0 INTRODUCTION ......................................................................................................................................... 1 2.0 SUMMARY OF ROUGH-GRADING OPERA TIONS ................................................................................. 2 2.1 As-Graded Conditions.......................................................................................................................2 2.2 Site Preparation and Removals.........................................................................................................4 2.3 Stability Fills.....................................................................................................................................4 2.4 Subdrain Installation.........................................................................................................................4 2.5 Cut/Fill Transition Conditions ..........................................................................................................5 2.6 Fill Placement...................................................................................................................................5 2.7 Laboratory Testing............................................................................................................................5 2.8 Field Density Testing ........................................................................................................................6 2.9 Graded Slopes...................................................................................................................................6 3.0 CONCLUSIONS...........................................................................................................................................7 3.1 General.............................................................................................................................................7 3.2 Summary of Conclusions..................................................................................................................7 4.0 RECOMMENDATIONS..............................................................................................................................9 4.1 Earthwork.........................................................................................................................................9 4.2 Site Preparation ...............................................................................................................................9 4.3 Excavations ......................................................................................................................................9 4.4 Fill Placement and Compaction.....................................................................................................10 4.5 Preliminary Foundation Recommendations..................................................................................10 4.6 Subdrain Outlet Maintenance ........................................................................................................11 4.7 Control of Surface Water and Drainage ........................................................................................ 11 5.0 LIMITATIONS ........................................................................................................................................... 13 LIST OF TABLES, APPENDICES. AND ILLUSTRATIONS Fij'ures and Plates Plates 1 and 2 - As-Graded Geotechnical Map (Rear-of-Text) Plates 3 and 4 - Field Density Test Location Map (Rear-of-Text) Appendices Appendix A - References Appendix B - Laboratory Testing Procedures and Test Results Appendix C - Summary of Field Density Test Results Project No. 133023-03 Page i August 7, 2015 1.0 INTRODUCTION In accordance with your request and authorization, LGC Valley, Inc. (LGC) has provided geotechnical services during the rough-grading operations for Planning Areas PA-3, PA-4, PA-6 and PA-13 of the Robertson Ranch project (Carlsbad Tract No. 13-03) located within the City of Carlsbad, California. This as- graded report summarizes our observations, field and laboratory test results, and the geotechnical conditions encountered during grading of the model complexes within PA-3 and PA-6, the recreation area of PA-4, and Planning Area PA-13. The subject rough-grading operations were performed in general accordance with previously published project geotechnical reports (Appendix A), geotechnical recommendations made during the course of grading, and the City of Carlsbad grading requirements. As of this date, the rough-grading operations for Lots 101 through 104 of PA-3, PA-4, Lots 206 through 211 of PA-6, and PA-13 are essentially complete. However, Planning Area PA-4 is currently sheet-graded and will need to be fine-graded in order to construct the planned recreation building pad, pool, driveway/parking area and other anticipated site improvements. A final as-graded report documenting the additional grading operations (i.e. fine grading) and providing addendum and/or additional geotechnical recommendations relative to the proposed development should be prepared upon completion of the future grading operations. The Rough Grading Plans for the Robertson Ranch project, prepared by O'Day Consultants (O'Day, 2014b), were utilized as a base map to present the as-graded geotechnical conditions and approximate locations of the field density tests. The As-graded Geotechnical Map (Plates 1 and 2) and the Field Density Test Location Map (Plates 3 and 4) are presented in the pocket at the rear of the text. Lots 101 through 104 of PA-3, PA-4, and Lots 206 through 211 of PA-6 are located in the central portion of the Robertson Ranch project while PA-13 is located in the extreme eastern portion near the intersection of El Camino Real and Cannon Road. The PA-3 model complex will includes Lot 101 through 104 on the south side of Nelson Court between Glasgow Drive and Wellspring Street. The PA-6 model complex will include Lot 206 through 211 on the east side of Wellspring Street north of Robertson Road. The Robertson Ranch Recreation Center, Planning Area PA-4, is located on the north side of Robertson Road and east of Wellspring Street. PA-13 is located along the south side of Glen Avenue and west of Wind Trail Way. Ultimately, development of the entire Robertson Ranch project will include the construction of 328 single- family residential lots within six single-family residential planning areas (Planning Areas PA-3, PA-5, PA- 6, PA-9, PA-10 and PA-13), park sites, a recreation center (PA-4), a multi-family residential development (PA-7 and a portion of PA-8) a retail center (PA-i1), and a senior housing development (a portion of PA- 8), along with associated retaining walls, slopes, storm water retention basins, interior roads and the improvement of El Camino Real between Cannon Road and Tamarack Avenue. The rough-grading operations for Lots 101 through 104 of PA-3, PA-4, Lots 206 through 211 of PA-6, and PA-13 were performed as a part of grading operations for the entire Robertson Ranch Development between September 2014 and May 2015. Project No. 133023-03 Page 1 August 7, 2015 2.0 SUMMARY OF ROUGH-GRADING OPERATIONS Rough-grading of the subject site began on September 5, 2014 and was essentially completed as of May 15, 2015. The grading operations were performed under the observation and testing services of LGC Valley, Inc. Our field technicians were onsite on a full-time basis during the grading operations while our field geologist was onsite on a periodic basis. The rough-grading operations included: Removal and off-site disposal of vegetation and miscellaneous debris; The removal of potentially compressible soils including alluvium, colluvium, topsoil, undocumented fill, desiccated existing documented fill, and weathered soils to competent terrace deposits or formational material; Overexcavation of cut/fill transition conditions within the limits of the planned buildings; Overexcavation of buried cut/fill transition conditions such that the resulting fill differential beneath the proposed building pads was less than a 3:1 (maximum fill thickness to the minimum fill thickness); Preparation of areas to receive fill; The placement of subdrains in the canyon bottoms; Excavation of formational material; and The placement of compacted fill soils creating the graded pads and adjacent slopes. Grading operations consisted of the placement of fill up to approximately 45 feet in depth within the model lot complex of PA-3 and up to 20 feet in depth within the model lot complex of PA-6, PA-4, and PA- 13. Both the model complexes and PA-13 consisted entirely of fill areas while the northwest portion of PA-4 was in a design cut area with up to 10 feet of design cuts. The cut/fill transition conditions present within the limits of the building pad and pool of PA-4 along the cut/fill transition, as shown on the rough grading plans (O'Day, 2014b), were overexcavated a minimum of 5 to 8 feet in depth and to a distance of at least 10 feet outside the planned building or pool limits. During the rough-grading operations, remedial grading was also performed so that the fill differentials beneath the proposed building pads were less than a 3:1 (maximum fill thickness to the minimum fill thickness). The as-graded geotechnical conditions are presented on the As- Graded Geotechnical Map (Plates 1 and 2). 2.1 As-Graded Conditions The as-graded conditions encountered during grading of the site were essentially as anticipated. In the vicinity of the model lot complexes and PA-4, alluvium and colluvium were encountered within the lower portion of the canyon running in a northwest-southeast direction while formational material was encountered on the slopes and at design cut grade below a thin veneer of topsoil and weathered soils. Planning Area PA-13 had been previously graded in 2008 under the observation and testing of GeoSoils. The previous grading included the removal of compressible soils, placement of fill, and excavation of the terrace deposits within PA-13 creating a sheet-graded pad (GeoSoils, 2008). Processing of the sheet-graded pad in order to receive additional fill involved removing the upper 2 to 4 feet of the existing soil (i.e. documented fill and terrace deposits). No, rotational, other unstable slope instabilities or landslides were observed during the site earthwork operations. Project No. 133023-03 Page 2 August 7, 2015 All unsuitable and potentially compressible soils were removed prior to fill placement. This included alluvium, colluvium, undocumented fill (associated with the past agricultural operations), desiccated documented fills (within PA-13), and weathered terrace and formational materials. The alluvium and colluvium typically consisted of light brown to brown silty fine sands, sandy clays and clayey sands derived from the terrace deposits and the formational material and were found to be very low to highly expansive, porous, and contained scattered organics. Removals of alluvium up to approximately 20 feet in depth were made within the northwest-southeast trending canyon in the vicinity of Lots 102 to 104 of PA-6. Removals of the colluvium, on the order of 2 to 6 feet, were made on the middle and lower portions of the hillsides on the site. Removals of the desiccated documented fill soils and weathered terrace deposits within PA-13 were made to a depth of 2 to 4 feet below the previous site grades. Terrace or older alluvial flood-plain deposits were encountered PA-13 and consisted of silty fine to medium sand to sandy-silty clay with minor gravels. Bedding within the terrace deposits was mainly massive to indistinct; however, a few sand beds that gently dipped to the west and north on the order of 5 degrees or less were encountered. The nature of the contact between the terrace deposits and formational material, where observed, was a relatively sharp contact with a near horizontal orientation. The formational material encountered in the vicinity of the model lot complexes and PA-4 consisted of the Santiago Formation. The material was found to be massively bedded to cross-bedded silty sandstones and minor clayey sandstones and sandy siltstones. The siltstones generally were olive green and orange brown, damp to moist, stiff to hard, moderately fractured and sheared. The sandstone generally consisted of light olive green, light brown and pale orange brown (where iron- oxidized stained), damp to moist, dense to very dense, silty very fine to medium grained sandstone. The majority of the Santiago material encountered within Robertson Ranch consisted of silty fine sands. Bedding within the Santiago Formation was highly variable, but overall, generally dipped 2 to 15 degrees to the west-southwest. A minor fault zone was geologically mapped in the western portion of PA-13 trending in a general northeast-southwest direction, dipping 50 to 60 degrees to the west. The short, somewhat, sinuous fault was only observed within the terrace deposits and appeared to die out to the north and south of PA- 13. The fault was also encountered by GeoSoils during the prior grading operations of PA- 13. The mapping by GeoSoils in 2008, indicated that the fault was observed to die out in the cut slope between PA- 13 and PA- 14 (to the north) and could not be traced south of PA- 13 for more than approximately 350 feet (GeoSoils, 2008). Based on our analysis during the current grading operations and review of the as-graded report by GeoSoils (GeoSoils, 2008) it is our professional opinion that the fault in not active; and therefore is not a constraint to development. The approximate location of the fault is shown on the As-Graded Geotechnical Map (Plate 1). No groundwater was encountered during the grading of the subject areas. However, unanticipated seepage conditions may occur after the completion of grading and establishment of site irrigation and landscaping. If these conditions should occur, steps to mitigate the seepage should be made on a case-by-case basis. Project No. 133023-03 Page 3 August 7, 2015 2.2 Site Preparation and Removals Prior to grading, the site was cleared of light vegetation and other miscellaneous debris and the material was disposed of at an offsite facility. Undocumented fill, topsoil, alluvium, colluvium, desiccated documented fill, weathered terrace soils and formational material were removed down to competent material (i.e. dense unweathered terrace or formational material). Remedial removals on site, below the existing ground surface, ranged from approximately 2 to 20 feet in depth. The thickness of compacted fills placed during this recent rough-grading operation, to achieve design rough grades (or sheet-graded pad elevations), ranged from 0 to approximately 45 feet. Following the remedial removals or overexcavations, areas to receive fill were scarified approximately 6-inches, moisture-conditioned, as needed, to obtain a near-optimum moisture content and compacted to a minimum 90 percent relative compaction (for fills of approximately 40 feet or less from design grades) or 93 percent relative compaction (for engineered fill below approximately 40 feet from design finish grades), as determined by ASTM Test Method D693 8 (i.e. the nuclear gauge method). 2.3 Stability Fills Stability fills were constructed to stabilize the exposed blocky claystone/siltstone and/or adverse (i.e. out-of-slope) geologic conditions present within the Santiago Formation. The stability fill keys were excavated to a width of approximately 15 feet and a minimum depth of 3 to 5 feet below the toe-of- slope. The keyway bottom was angled at least 2 percent into-the-slope. The stability fill front cuts were excavated near vertical while the back-cuts were excavated at an approximate 1:1 (horizontal to vertical) slope inclination. A stability fill was excavated along the proposed slope on the west side of PA-4 and the location is presented on the As-graded Geotechnical Map (Plate 2). 2.4 Subdrain Installation Canyon and stability fill subdrains were installed under the observation of a representative of LGC in general accordance with the planned locations of the approved geoteclmical report, and the standard details (LGC, 2014a). After the potentially compressible material in the canyons were removed to competent material or when compacted fill was placed over competent material to obtain flow to a suitable outlet location, a subdrain was installed along the canyon bottom. The canyon subdrains consisted of a 6-inch diameter perforated pipe surrounded by a minimum of 9- cubic feet (per linear foot) of crushed 3/4-inch gravel wrapped in Mirafi 140N filter fabric. In addition to the canyon subdrains, subdrains were also installed along the bottom backside of the stability fill keys. The stability fill subdrains consisted of a 4-inch diameter perforated pipe surrounded by a minimum of 3-cubic feet (per linear foot) of clean 3/4-inch gravel wrapped in Mirafi 140N filter fabric. Project No. 133023-03 Page 4 August 7, 2015 The canyon and stability fill subdrains were placed with a minimum 1-percent fall (2-percent or greater where possible) to a suitable outlet location. The location of the subdrains placed during the mass grading operations for the project were surveyed by the project civil engineer. The subdrain locations are presented on the As-graded Geotechnical Map (Plate 2). 2.5 Cut/Fill Transition Conditions Based on the as-graded conditions, the cut/fill transition condition present within the limits of the building pad and pool in PA-4, as shown on the rough grading plans (O'Day, 2014b), were overexcavated a minimum of 5 feet in depth beneath the building and 8 feet in depth beneath the pool. The overexcavation extended to a distance of at least 10 feet outside the planned building or pool limits. During the rough-grading operations, remedial grading was also performed so that the fill differential beneath the proposed building pads was less than a 3:1 (maximum fill thickness to the minimum fill thickness). 2.6 Fill Placement After processing the areas to receive fill, native soil was generally spread in approximately 8-inch loose lifts, moisture-conditioned as needed to attain near-optimum moisture content, and compacted to at least 90 or 93 percent of the maximum dry density determined in accordance with ASTM Test Method D1557. Fill soils less than 40 feet below the design finish grades were compacted to a minimum 90 percent relative compaction while fill soils greater than 40 feet below the design finish grades were compacted to a minimum 93 percent relative compaction. Compaction was achieved by use of heavy-duty construction equipment. Areas of fill in which either field density tests indicated less than 90 or 93 percent relative compaction or the soils exhibited nonuniformity and/or showed an inadequate or excessive moisture content, were reworked, recompacted, and retested until a minimum 90 or 93 percent relative compaction and near-optimum moisture content was achieved. 2.7 Laboratory Testin2 Maximum dry density tests of representative on-site soils were performed (by others during the previous investigation and by LGC during the current rough-grading operations) in general accordance with ASTM Test Method D1557. Expansion potential, soluble sulfate content, and corrosion testing of representative finish grade soils within the subject planning areas were performed (with the exception of Planning Area PA-4). The near-surface soils have a very low to high expansion potential; a negligible soluble sulfate content; are moderate to severely corrosive to buried metals based on the minimum soil resistivity values; and are corrosive to buried metals and reinforcing steel in concrete based on the chloride concentrations. The laboratory test results are presented in Appendix B. Project No. 133023-03 Page 5 August 7 2015 2.8 Field Density Testing Field density testing was performed using the Nuclear-Gauge Method (ASTM Test Method D6938). The approximate test locations are shown on the Field Density Test Location Maps (Plates 3 and 4). The results of the field density tests are summarized in Appendix C. The field density testing was performed in general accordance with the applicable ASTM standards and the current standard of care in the industry. In-situ soil density testing is intended to verify the effectiveness of the earthmoving operation in general and is performed on a spot-check basis; as such, some variations in relative compaction should be expected from the results documented herein. 2.9 Graded Slopes Manufactured fill slopes within the subject areas were surveyed by the civil engineer and constructed with slope inclinations of 2:1 (horizontal to vertical) or flatter. Permanent graded fill slopes adjacent to or within the subject areas range from approximately 5 to 20 feet in height. There are no permanently graded cut slopes within or adjacent to the subject areas. The on-site fill slopes are considered grossly and surficially stable from a geotechnical standpoint (under normal irrigation/precipitation patterns) provided the project geotechnical recommendations are incorporated into the fine-grading, post-grading, construction, and post-construction phases of site development. Project No. 133023-03 Page 6 August 7, 2015 3.0 CONCLUSIONS 3.1 General The rough-grading of Lots 101 through 104 of PA-3, PA-4, Lots 206 through 211 of PA-6, and Lots 1 through 24 of PA-13 of Robertson Ranch located within the City of Carlsbad, California was performed in general accordance with the project geotechnical report (LGC, 2014a), geotechnical recommendations made during the course of grading, and the City of Carlsbad grading requirements. It is our professional opinion that the subject site is suitable for the intended use provided the recommendations of the referenced geotechnical reports (LGC, 2014a and 2015a through 2015i) or those provided at the completion of the future fine grading are incorporated into the design and construction; and that proper landscaping, irrigation, and maintenance programs are implemented. The following is a summary of our conclusions concerning the rough-grading of Lots 101 through 104 of PA-3, PA-4, Lots 206 through 211 of PA-6, and PA- 13. 3.2 Summary of Conclusions Rough-grading of Lots 101 through 104 of PA-3, PA-4, Lots 206 through 211 of PA-6, and Lots 1 through 24 of PA- 13 of Robertson Ranch is essentially complete. Geotechnical conditions encountered during the rough-grading operation were generally as anticipated. The geologic units encountered during the rough-grading of the site consisted of documented and undocumented fill soils, topsoil, colluvium, alluvium, terrace deposits, and the Santiago Formation. Unsuitable undocumented fill soils, topsoil, colluvium, alluvium, desiccated documented fill, and weathered terrace deposits and formational material were removed to competent formational material within the limits of grading. Landslides or surficial slope failures were not encountered during the grading operations. No evidence of active faulting was encountered during the site rough-grading operations within the model complex of PA-3 and PA-6 and within the Recreation Lot of PA-4; however, minor inactive faulting was encountered within PA-13 but is not considered a constraint to development. Ground water seepage conditions were not encountered during the subject grading operations. Stability fills were constructed to improve the gross stability of the cut slopes exposing fractured and blocky formational material and/or adverse geologic conditions on the site. The stability fill keys were excavated in accordance with the project geotechnical recommendations. Subdrains were placed in the canyon bottoms and along the heel of the stability fill keys. The subdrains were (or will be) outletted into suitable storm drain facilities or near the toe-of-slope of the stability fill slopes. Project No. 133023-03 Page 7 August 7, 2015 The cut/fill transition conditions present within the limits of the building pad and pool of PA-4 were overexcavated a minimum of 5 feet beneath the building and 8 feet beneath the pool and to a distance of at least 10 feet outside the planned building or pool limits. During the rough-grading operations, remedial grading was performed so that the fill differential beneath the proposed building pads was less than a 3:1 (maximum fill thickness to the minimum fill thickness). Fill soils were derived from on-site soils. Where tested, the fill soils within the site were compacted at least a 90 or 93 percent relative compaction (based on ASTM Test Method D1557) and near-optimum moisture content in accordance with the recommendations of the project geotechnical report (LGC, 2014a) and the requirements of the City of Carlsbad. Fill soils less than 40 feet below the design finish grades were compacted to a minimum 90 percent relative compaction while fill soils greater than 40 feet below the design finish grades were compacted to a minimum 93 percent relative compaction. A summary of the results of the field density tests is presented in Appendix C. Due to the dense nature of the on-site soils, it is our professional opinion that the liquefaction hazard at the site is considered low. Representative testing of the finish grade soils on the building pads of Lot 1 through 24, 101 through 104, and 206 through 211 indicated the near-surface soils have a very low to high expansion potential. The test results are presented in Appendix B. The potential for soluble sulfate attack on concrete in contact with the finish grade soils of Lot 1 through 24, 101 through 104, and 206 through 211 is considered negligible based on ACT Criteria (ACT 318R-05 Table 4.3.1). The soluble sulfate content test results are included in Appendix B. Representative testing of the finish grade soils on the building pads of Lot 1 through 24, 101 through 104, and 206 through 211 was found to be moderately corrosive to corrosive to ferrous metals. The test result is presented in Appendix B. Expansion potential or corrosion testing of representative finish grade soils of Planning Area PA-4 was not performed; however, based on our observations during the site grading operations and test results of similar soils in other portions of the Robertson Ranch project, we anticipate that the soils within PA-4 will have a very low to low expansion potential, a negligible sulfate content and will be moderately corrosive to corrosive to buried metals. These assumptions should be confirmed after the completion of the fine-grade operations of the recreation center. It is our professional opinion that the slopes of the development are considered to be grossly and surficially stable, as constructed, under normal irrigation/precipitation patterns, provided the recommendations in the project geotechnical reports are incorporated into the post-grading, construction and post-construction phases of site development. Project No. 133023-03 Page 8 August 7, 2015 4.0 RECOMMENDATIONS 4.1 Earthwork We anticipate that future earthwork at the site will consist of site preparation, fine-grading, utility trench excavation and backfill, retaining wall backfill, and street/driveway and parking area pavement section preparation and compaction. We recommend that the earthwork on site be performed in accordance with the geotechnical recommendations presented in the project preliminary geotechnical report (LGC, 2014a), recommendations provided after the completion of the fine-grading operations within Planning Area PA-4, and the City of Carlsbad grading requirements. 4.2 Site Preparation During future grading of PA-4, the areas to receive structural fill or engineered structures should be cleared of surface obstructions, potentially compressible material (such as desiccated fill soils or weathered formational material), and stripped of vegetation. Vegetation and debris should be removed and properly disposed of off-site. Holes resulting from removal of buried obstructions that extend below finish site grades should be replaced with suitable compacted fill material. Areas to receive fill and/or other surface improvements should be scarified to a minimum depth of 12 inches, brought to optimum moisture condition, and recompacted to at least 90 percent relative compaction (based on ASTM Test Method D1557). If the length of time between the completion of grading and the construction of the development is longer than six months, we recommend that the building pads be evaluated by the geotechnical consultant and, if needed, the finish grade soils on the building pads should be scarified a minimum of 12 inches, moisture-conditioned to optimum moisture-content and recompacted to a minimum 90 percent relative compaction (based on ASTM Test Method D1557). 4.3 Excavations Excavations of the on-site materials may generally be accomplished with conventional heavy-duty earthwork equipment. It is not anticipated that blasting will be required or that significant quantities of oversized rock (i.e. rock with maximum dimensions greater than 8 inches) will be generated during future grading. However, localized cemented zones within the cut areas may be encountered on the site that may require heavy ripping and/or removal. If oversized rock is encountered, it should be placed in accordance with the project geotechnical recommendations (LGC, 2014a), hauled offsite, or placed in non-structural or landscape areas. Temporary excavations maybe cut vertically up to five feet. Excavations over five feet should be slot- cut, shored, or cut to a 1:1 (horizontal to vertical) slope gradient. Surface water should be diverted away from the exposed cut, and not be allowed to pond on top of the excavations. Temporary cuts should not be left open for an extended period of time. Planned temporary conditions should be Project No. 133023-03 Page 9 August 7 2015 reviewed by the geotechnical consultant in order to reduce the potential for sidewall failure. The geotechnical consultant may provide recommendations for controlling the length of sidewall exposed. 4.4 Fill Placement and Compaction The on-site soils are generally suitable for use as compacted fill provided they are free or organic material, debris, and rock fragments larger than 8 inches in maximum dimension. We do not recommend that high or very high expansive soils be utilized as fill for the building pads or as retaining wall backfill. All fill soils should be brought to 2-percent over the optimum moisture content and compacted in uniform lifts to at least 90 percent relative compaction based on the laboratory maximum dry density (ASTM Test Method D1557). The optimum lift thickness required to produce a uniformly compacted fill will depend on the type and size of compaction equipment used. In general, fill should be placed in lifts not exceeding 8 inches in compacted thickness. Placement and compaction of fill should be performed in general accordance with current City of Carlsbad grading ordinances, sound construction practices, and the project geotechnical recommendations. If import soils are to be used as fill, they should be: 1) essentially free from organic matter and other deleterious substances; 2) contain no materials over 6 inches in maximum dimension; 3) have a very low to low expansion potential (i.e. an Expansion Index ranging from 0 to 50); and 4) have a negligible sulfate content. Representative samples of the desired import source should be given to the Geotechnical Consultant at least 48 hours (2 working days) before importing grading begins so that its suitability can be determined and appropriate tests performed. 4.5 Foundation Recommendations Lots 101 through 104 of PA-3 PA-4, Lots 206 through 211 of PA-6, and PA-13: The preliminary foundation design recommendations applicable to the construction of the residential structures on Lots 101 through 104 of PA-3, Lots 206 through 211 of PA-6, and Lots 1 through 23 of PA-13 were previously provided in the our letter report entitled "Preliminary Foundation Design for the Single- Family Residential Structures, Planning Areas PA-3, PA-5, PA-6, PA-9, PA-b, and PA-13, Robertson Ranch", dated April 14, 2015 (LGC, 2015b) and our letter entitled "Deepened Footing Recommendation of Building Foundation Adjacent to Proposed Nexus eWater Recycler System, Planning Areas PA-3, PA-5, PA-6, PA-9, PA-b, and PA-13, Robertson Ranch" dated July 23, 2015 (LGC, 2015e). The previous recommendations remain applicable for the design of the proposed structures on the subject lots. Based on the expansion potential and corrosion laboratory testing of representative soils on the subject lots, Lots 101 through 104 within PA-3 have a low expansion potential, Lots 206 though 211 of PA-6 have a very low expansion potential, Lots 1 through 12 of PA- 13 have a high expansion potential, and Lots 13 through 23 of PA-13 have a medium expansion potential. The finish grade soils on Lots 101 through 104 of PA-3, Lots 206 through 211 of PA-6, and Lots 1 through 23 of PA-13 are considered to have a negligible sulfates and are moderately to severely corrosive to buried metals. The results Project No. 133023-03 Page 10 August 7, 2015 of the expansion potential and corrosion testing is presented in Appendix B. Recreation Center PA-4: The preliminary foundation design and other recommendations relative to the fine-grading, post-grading, and construction of the recreation center building, pool, and other improvements were previously provided in the our letter report entitled "Review of the Proposed Recreation Center, Planning Area PA-4, Robertson Ranch", dated March 30,2015 (LGC, 2015a). The previous recommendations remain applicable for the design and construction of the proposed improvements within PA-4. Based on our observations during the site grading operations and test results of similar soils in other portions of the Robertson Ranch project, we anticipate that the soils within PA-4 will have a very low to low expansion potential, a negligible sulfate content and will be moderately corrosive to corrosive to buried metals. These assumptions should be confirmed after the completion of the fine-grade operations of the recreation center. 4.6 Subdrain Outlet Maintenance The approximate location of the subdrains and subdrain outlets constructed during the rough- grading operations are identified on the As-Graded Geotechnical Map (Plate 2). All subdrain outlets should be periodically cleared of soil cover or other potential blockage that may have occurred since initial subdrain construction. If retaining walls are proposed along the toe-of-slope in the location of the stability fills/subdrain outlet locations, the existing subdrains should be tied into the retaining wall back-drain system and/or placed into an appropriate storm drain facility. 4.7 Control of Surface Water and Draina2e Surface drainage should be carefully taken into consideration during fine-grading, landscaping, and building construction. Positive drainage of surface water away from structures is very important. No water should be allowed to pond adjacent to buildings or the top of slopes. Positive drainage may be accomplished by providing drainage away from buildings at a gradient of at least 2 percent for a distance of at least 5 feet, and further maintained by a swale of drainage path at a gradient of at least 1 percent. Where limited by 5-foot side yards, drainage should be directed away from foundations for a minimum of 3 feet and into a collective swale or pipe system. Where necessary, drainage paths may be shortened by use of area drains and collector pipes. Eave gutters also help reduce water infiltration into the subgrade soils if the downspouts are properly connected to appropriate outlets. The impact of heavy irrigation or inadequate runoff gradient can create perched water conditions, resulting in seepage or shallow groundwater conditions where previously none existed. Maintaining adequate surface drainage and controlled irrigation will significantly reduce the potential for nuisance- type moisture problems. To reduce differential earth movements (such as heaving and shrinkage due to the change in moisture content of foundation soils, which may cause distress to a structure or improvement), the moisture content of the soils surrounding the structure should be kept as relatively constant as possible. Project No. 133023-03 Page 11 August 7, 2015 All area drain inlets should be maintained and kept clear of debris in order to function properly. Rerouting of site drainage patterns and/or installation of area drains should be performed, if necessary. A qualified civil engineer or a landscape architect should be consulted prior to rerouting of drainage. Project No. 133023-03 Page 12 August 7, 2015 5.0 LIMITATIONS Our services were performed using the degree of care and skill ordinarily exercised, under similar circumstances, by reputable engineers and geologists practicing in this or similar localities. No other warranty, expressed or implied, is made as to the conclusions and professional advice included in this report. The samples taken and submitted for laboratory testing, the observations made and the in-situ field testing performed are believed representative of the entire project; however, soil and geologic conditions revealed by excavation may be different than our preliminary findings. If this occurs, the changed conditions must be evaluated by the project soils engineer and geologist and design(s) adjusted as required or alternate design(s) recommended. This report is issued with the understanding that it is the responsibility of the owner, or of his/her representative, to ensure that the information and recommendations contained herein are brought to the attention of the architect and/or project engineer and incorporated into the plans, and the necessary steps are taken to see that the contractor and/or subcontractor properly implements the recommendations in the field. The contractor and/or subcontractor should notify the owner if they consider any of the recommendations presented herein to be unsafe. The findings of this report are valid as of the present date. However, changes in the conditions of a property can and do occur with the passage of time, whether they be due to natural processes or the works of man on this or adjacent properties. In addition, changes in applicable or appropriate standards may occur, whether they result from legislation or the broadening of knowledge. Accordingly, the findings of this report may be invalidated wholly or partially by changes outside our control. Project No. 133023-03 Page 13 August 7, 2015 A FFENDIX A References American Society of Civil Engineers (ASCE), 2013, Minimum design loads for buildings and other structures, ASCE/SEI 7-10, Third Printing, 2013. California Building Standards Commission (CBSC), 2013a, California Building Code, California Code of Regulations, Title 24, Part 2, Volume I and 2 of 2 (based on the 2012 International Building Code). CBSC, 2013b, California Residential Building Code, California Code of Regulations, Title 24, Part 2.5,(based on the 2012 International Residential Code). CBSC, 2013c, California Green Building Standards Code, California Code of Regulations, Title 24, Part 11. Dahlin Group, 2015, Site plan and perspectives, PA-4 recreation building @ Robertson Ranch, Sheet Al-i through A1-5, dated January 8. GeoSoils, Inc., 2002, Geotechnical evaluation of the Robertson Ranch Property, City of Carlsbad, San Diego County, California, W.O. 3098-Al-SC, dated January 29, 2002. GeoSoils, Inc., 2004, Updated geotechnical evaluation of the Robertson Ranch property, Carlsbad, San Diego County, California, W.O. 3098-A2-SC, dated September 20, 2004. GeoSoils, Inc., 2008, Report of mass grading, Planning Area 12 (13.44 Acres), and Planning Area 13 (6.92 Acres), Robertson Ranch West, Carlsbad, San Diego County, California 92010, City of Carlsbad Planning Department Application No. SUP 06-12/HDP 06-04, W.O. 5247-B1-SC, dated June 5. GeoSoils, Inc., 2010, Updated geotechnical investigation for Robertson Ranch West Village, Carlsbad, San Diego County, California, W.O. 6145-A-SC, dated October 10, 2010. GeoSoils, Inc., 2011, Supplement to the updated geotechnical investigation for Rancho Costera (formerly Robertson Ranch West Village), Carlsbad, San Diego County, California, W.O. 6145-Al-SC, dated June 6. GeoSoils, Inc., 2012, Preliminary geotechnical review of "vesting master tentative map for Rancho Costera," 40-scale plans, sheets 1 through 21, Job No. 101307, Revised May 1, 2012, by O'Day Consultants, W.O. 6145-A9-SC, dated May 24, 2012. GeoSoils, Inc., 2013, Addendum to the updated and supplemental geotechnical investigations for Rancho Costera (formerly Robertson Ranch West Village), Carlsbad, San Diego County, California, W.O. 6145-A1O-SC, dated July 16, 2013. Project No. 133023-03 Page A-] August 7, 2015 References (continued) LGC Valley, Inc., 2014a, Geotechnical and environmental recommendations for Robertson Ranch West, Carlsbad Tract No. 13-03, Carlsbad, California, Project Number 133023-03, dated April 29, 2014. LGC Valley, Inc., 2014b, Change of Geotechnical Consultant, Robertson Ranch West Project, Carlsbad Tract No. 13-0, Carlsbad, California, Project No. 133023-03, dated May 6, 2014. LGC Valley, Inc., 2015a, Geotechnical review of the proposed recreation Center, Planning Area PA- 4, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, California, Project No. 133023-06, dated March 30, 2015 LGC Valley, Inc., 2015b, Preliminary foundation design for the single-family residential structures, Planning Areas PA-3, PA-5, PA-6, PA-9, PA-b, and PA-13, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 1.33023-06, dated April 14, 2015. LGC Valley, Inc., 2015c, As-graded completion letter, Lots 1 through 23, Robertson Ranch, Carlsbad Tract No. 13-03, 4980 El Camino Real, Carlsbad, California, Project No. 133023- 03, dated June 9, 2015. LGC Valley, Inc., 2015d, Preliminary Review of Building Setbacks for the Proposed Residential Planning Areas 3, 5, 6, 9, 10, and 13, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-03, dated February 27, 2015, revised June 24, 2015. LGC Valley, Inc., 2015e, Deepened Footing Recommendation of Building Foundation Adjacent to Proposed Nexus eWater Recycler System, Planning Areas PA-3, PA-5, PA-6, PA-9, PA-b, and PA-13, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-03, dated July 23, 2015. LGC Valley, Inc., 2015f, Geotechnical Foundation Plan Review for the Proposed Recreation Center, Planning Area PA-4, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California Project No. 133023-06, dated July 29, 2015 LGC Valley, Inc., 2015g, Geotechnical Post-Tension Foundation Plan Review for The Ridge Development within Planning Area 3 (PA-3), Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-06, dated August 4, 2015. LGC Valley, Inc., 2015h, Geotechnical Post-Tension Foundation Plan Review for The Vistas Development within Planning Area 6 (PA-6), Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-06, dated August 4, 2015. LGC Valley, Inc., 2015i, Geotechnical Post-Tension Foundation Plan Review for The Vistas Development within Planning Area 13 (PA-13), Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-06, dated August 4, 2015. Project No. 133023-03 Page A-2 August 7 2015 References (continued) Nexus eWater, 2015, Recycler System Standard Drawings, 9 Sheets, dated April 30, 2015. O'Day Consultants, 2014a, Vesting tentative map for Carlsbad Tract No. 13-03-2, 23 Sheets, dated January 16, 2014. O'Day Consultants, 2014b, Grading plans for Rancho Costera, Robertson Ranch West Village, Carlsbad Tract No. 13-03, Drawing No. 480-3A, 44 Sheets, dated August 25, 2014. Post-Tensioning Institute, 2006, Design of post tensioned slabs-on-ground, Third Addition, Addendum 1 dated May 2007, and Addendum 2 dated May 2008, with errata February 4, 2010. Summer/Murphy & Partners, 2015, Robertson Ranch recreation center plot plan, 1 sheet, dated January 5. United States Geological Survey (USGS), 2008a, "2008 National Seismic Hazard Maps - Fault Parameters" retrieved from: http://geohazards.usgs.gov/cfusion/hazfaults_searchlhf search main.cfm USGS, 2008b, "2008 Interactive Deaggregations (Beta)," retrieved from: https://geohazards.usgs.gov/deaggintl2008/ USGS, 2013, U.S. Seismic Design Maps, retrieved from: http://geohazards.usgs.gov/designmaps/us/batch.php4csv Project No. 133023-03 Page A-3 August 7, 2015 APPENDJX B Laboratory Testing Procedures and Test Results Maximum Dry Density Tests: The maximum dry density and optimum moisture content of typical materials were determined in accordance with ASTM Test Method D1557. The results of these tests are presented in the table below. Number Iflp1e Sample Description Maximum Dry Density (pcf) Optimum Moisture Content (%) 1 Gray brown sandy CLAY 117.5 16.0 2 Greenish gray silty CLAY 102.0 21.5 3 Red brown sandy CLAY 118.0 13.5 4 Dark gray brown clayey fine SAND 123.5 11.0 5 Medium brown f-rn SAND 124.5 11.0 6 Light brown silty SAND 114.5 13.5 7 Olive gray clayey SILT 111.5 19.5 8 Pale gray silty fine SAND 115.5 14.5 9 Pale gray silty f-m SAND 127.5 10.5 10 Medium brown clayey SAND 128.0 10.0 11 Light brown clayey SAND 122.0 12.5 12 Pale brown fine sandy CLAY to clayey SAND 124.0 12.0 13 Pale brown fine sandy CLAY to clayey SAND 125 . 11.0 14 Light gray silty fine SAND 117.0 15.0 Project No. 133023-03 Page B-i August 7, 2015 Expansion Index Tests: The expansion potential of selected materials was evaluated by the Expansion Index Test, U.B.C. Standard No. 18-I-B. Specimens are molded under a given compactive energy to approximately the optimum moisture content and approximately 50 percent saturation or approximately 90 percent relative compaction. The prepared 1-inch thick by 4-inch diameter specimens are loaded to an equivalent 144 psf surcharge and are inundated with tap water until volumetric equilibrium is reached. The results of these tests are presented in the table below: Lots Numbers Sample Description Expansion Index Expansion Potential 1-12 (PA-13) Brown clayey SAND 108 High 13-23 (PA-13) Brown clayey SAND 57 Medium 88-91 & 100-104 (PA-3) Light brown silty fine SAND 35 Low 206-211 (PA-6) Light gray silty SAND 16 Very Low Soluble Sulfates: The soluble sulfate contents of selected samples were determined by standard geochemical methods (Caltrans 417). The test results are presented in the table below: Lot Numbers Sulfate Content Potential Degree Sample Description (% by Weight) of Sulfate Attack* Lots 1-23 (PA-13) Light brown silty fine SAND 0.011 Negligible Lots 101-104 (PA-3) Medium brown silty clayey 0.025 Negligible SAND Lots 206-211 (PA-6) Pale yellow brown silty fine 0.071 Negligible SAND * Per ACI 318R-08 Table 4.3.1. Project No. 133023-03 Page B 2 August 7, 2015 Chloride Content: Chloride content was tested in accordance with Caltrans Test Method (CTM) 422. The results are presented below: Chloride Potential Degree Lot Numbers Sample Description Content (ppm) of Chloride Attack* Lots 1-23 (PA-13) Light brown silty fine SAND 270 Negligible Lots 101-104 (PA-3) Medium brown silty clayey 205 Negligible SAND Lots 206-211 (PA-6) Pale yellow brown silty fine 175 Negligible SAND * Extrapolation from California Test Method 532, Method for Estimating the Time to Corrosion of Reinforced Concrete Substructures and previous experience Minimum Resistivity and pH Tests: Minimum resistivity and pH tests were performed in general accordance with CTM 643 and standard geochemical methods. The electrical resistivity of a soil is a measure of its resistance to the flow of electrical current. As results of soil's resistivity decreases corrosivity increases. The results are presented in the table below: Lot Numbers Sample Description Minimum Resistivity Potential Degree (ohms-cm)) of Corrosivity* Lots 1-23 (PA-13) Light brown silty fine SAND 1200 Moderately Corrosive Lots 101-104 (PA-3) Medium brown silty clayey 640 Corrosive SAND Lots 206-211 (PA-6) Pale yellow brown silty fine 800 Corrosive SAND * NACE Corrosion Basics Project No. 133023-03 Page B 3 August 7 2015 APPENDIX C Summary of Field Density Test Results Project No. 133023-03 Page C-i August 7 2015 LGC Valley, Inc. 2420 Grand Avenue, Suite F2, Vista, California 92081 760-599-7000 / Fax 760-599-7007 REPORT OF COMPACTION TEST DATA Print Date: Project No. Client. Project Name: Location: Reviewed by: August 10, 2015 133023-03 Toll Brothers Robinson Ranch (PA3&6 Model Lots, PA4, and PA-la) Carlsbad, CA Test # Nuclear Gauge or Sand Cone (S) Test Date Test Location Soil Type Test of Elevation or Depth . infeet) Moisture (%) Dry Density (pc__TT_elative Compaction (%) Comments Field Optimum Field . Maximum Obtained Required 1 N 9/3/2014 PA-13 Lot 21 i _2 - CF 65.0 18.5% 21.5% 94.6 102.0 1 93% 90% retest on 1A 1A N 9/3/2014 PA-13 Lot 21 _2 - CF 65.0 21.8% 21.5% 94.0 102.0 92% 90% retest of 1 2 N 9/3/2014: PA-13 Lot 17 2 CF 67.0 13.5% 21.5% 96.2 102.0 94% 90% retest on 2A 2A N 9/3/2014 PA-13 Lot 17 _2 - CF 67.0 21.6% 21.5% 92.6 102.0 91% 90% retest of 2 - 3 N 9/3/2014 PA-13 Lot 15 2 CF 68.0 22.6% 21.5% 942 102.0 92% 90% 4 N 9/3/2014 PA-13 Lot 20 - - CF 67.0 16.8% 16.0% 106.1 117.5 90% 90% 5 N 9/4/2014 PA-13 Lot 13 2 CF 69.0 24.3% 21.5% 93.6 102.5 91% 90% 6 N 9/4/2014 PA-13 Lot 22 3 CF 68.0 14.6% 13.5% 108.3 118.0 92% 90% 7 - - 9/4/2014 PA-13 Lot 24 2 CF 67.0 20.3% 21.5% 92.8 102.0 91% 90% 8 - - 9/4/2014 PA-l3 Lot l 3 CF 69.0 14.1% 13.5% 106.8 118.0 91% 90% 9 - - 9/4/2014 PA-13 Lot 4 3 CF 69.0 15.4% 13.5% 107.8 118.0 91% 90% 10 - N 9/4/2014 PA-1 3 Lot 8 1 CF 70.0 19.4% 16.0% 105.8 117.5 90% 90% ii N 9/4/2014 PA-13 Lot ii 1 CF 70.0 16.3% 16.0% 107.8 117.5 92% 90% 31 N 9/12/2014 PA-13 Lot 1 CF 70.0 15.6% 16.0% 107.7 117.5 92% 90% 32 N 9/12/2014, PA-13 Lot 1 CF 71.0 19.7% 16.0% 108.7 117.5 93% 90% 33 N 9/12/2014 PA-i3 Lot i0 1 CF 71.0 18.8% 16.0% 106.9 117.5 91% 90% 34 N 9/12/2014 PA-13 Lot 12 3 CF 70.0 14.9% 13.5% 107.1 118.0 91% 90% 35 N 9/12/2014 PA-13 Lot 23 3 CF 69.0 14.0% 13.5% 108.6 118.0 92% 90% 46 N 9/15/2014 PA-13 Lot 23 Slope 4 CF 71.0 9.9% 11.0% 114.2 123.5 92% 90% 47 N 9/15/2014 PA-13 Lot 22 Slope 4 CF 72.0 12.9% 11.0% 112.3 123.5 91% 90% 51 N 9/16/2014 PA-13 Lot I 4 CF 71.0 11.2% 11.0% 1 111.6 123.5 90% 90% 52 N 9/16/2014 PA-13 Lot 4 CF 72.0 10.0% 11.0% 112.6 123.5 91% 90% 53 N 9/16/2014, PA-13 Lot '. 6 CF 72.0 13.7% 135% 106.8 114.5 93% 90% 65 N 9/17/2014 PA-13 Lot ii 5 CF 72.0 10.5% 11.0% 117.2 124.5 94% 90% 66 N 9/17/2014 PA-13 Lot 5 CF 72.0 11.8% 11.0% 119.6 124.5 96% 90% 67 N 9/17/2014 PA-13 Lot 5 CF 71.0 10.6% 11.0% 120.0 124.5 96% 90% 73 N 9/17/2014 PA-13 Lot ii 1 CF 73.0 15.7% 16.0% 105.9 117.5 90% 90% 74 N 9/17/2014 PA-13 Lot 8 . 4 CF 73.0 11.8% 11.0% 111.8 123.5 91% 90% 75 N 9/17/2014 PA-13 Lot 5 CF 73.0 9.8% 11.0% 115.1 124.5 92% 90% 76 N 9/17/2014. PA-13 Lot 5 CF 72.0 12.8% 11.0% 112.9 124.5 91% 90% 86 N 9/18/2014 PA-13 Lot 4 CF 73.0 12.6% 11.0% 111.7 123.5 90% 90% 87 N 9/18/2014 PA-13 Lot 4 CF 73.0 12.2% 11.0% 113.1 123.5 92% 90% 88 N 9/18/2014 PA-13 Lot 4 CF 73.0 13.0% 11.0% 113.8 123.5 92% 90% 89 N 9/18/2014 PA-13 Lot 12 5 CF 73.0 13.5% 11.0% 114.0 124.5 92% 90% 92 N 9/19/2014 PA-13 Lot 8 CF 74.0 14.8% 14.5% 107.2 115.5 93% 90% 93 N 9/19/2014 PA-13 Lot 8 CF 74.0 15.8% 14.5% 104.9 115.5 91% 90% 94 N 9/19/2014 PA-13 Lot 4 CF 74.0 12.8% 11.0% 113.5 123.5 92% 90% 95 N 9/19/2014 PA-l3 Lot i 8 CF 73.0 15.5% 14.5% 106.8 115.5 92% 90% 96 N 9/19/2014 PA-13 Loti2 Slope 3 CF 74.0 14.6% 13.5% 111.2 118.0 94% 90% 97 N 9/19/2014 PA-13 Lot 1 3 CF 74.0 15.3% 13.5% 110.2 118.0 93% 90% 100 N 9/19/2014 PA-13 Lot 4 CF 74.0 11.9% 11.0% 115.6 123.5 94% 90% 101 N 9/22/2014 PA-13 Lot5 4 CF 75.0 11.4% 11.0% 114.9 123.5 93% 1 90% 102 N 9/22/2014 PA-13 Lot 10 4 CF 75.0 12.3% 11.0% 115.3 123.5 93% 90% 103 N 9/22/2014 PA-13 Lot 4 CF 75.0 11.8% 11.0% 117.4 123.5 95% 90% 104 N 9/2212014 PA-13 Lots 4 CF 75.0 12.2% 11.0% 113.3 123.5 92% 90% 105 N 9/2212014 PA-13 Lot 10 4 CF 76.0 13.8% 11.0% 112.8 123.5 91% 90% 106 N 9/23/2014 A-13 Lot 11 4 CF 77.0 9.9% 11.0% 112.9 123.5 91% 90% 107 N 9/23/2014 A-13 Lot 8 3 CF 76.0 12.5% 13.5% 107.4 118.0 91% 90% 108 N 9/23/2014 A-13 Lot 4 CF 76.0 9.9% 11.0% 116.9 123.5 95% 90% 109 N 9/23/2014 A-13 Lot 1 4 CF 75.0 10.3% 11.0% 114.2 123.5 92% 90% 110 N 9/23/2014 A-13 Lot 4 CF 78.0 10.7% 11.0% 112.3 123.5 91% 90% 111 N 9/23/2014 A-13 Lot 4 CF 76.0 13.9% 11.0% 115.9 123.5 94% 90% 112 N 9/23/2014 A-13 Lot 4 CF 77.0 11.3% 11.0% 115.5 123.5 94% 90% 113 N 9/23/2014 A-13 Lot 1 3 CF 76.0 13.8% 13.5% 107.9 118.0 91% 90% 120 N 9/24/2014 A-13 Lot CF 76.0 10.7% 11.0% 113.8 123.5 92% 90% 121 N 9/24/2014 A-13 Lot 4 CF 76.0 10.6% 11.0% 1 112.1 123.5 91% 90% 8/11/2015 Page 1 of 5 LGC Valley, Inc. 2420 Grand Avenue, Suite F2, Vista, California 92081 760-599-7000 I Fax 760-599-7007 REPORT OF COMPACTION TEST DATA Print Date: Project No. Client. Project Name: Location: Reviewed by: August 10, 2015 133023-03 Toll Brothers Robinson Ranch (PA3&6 Model Lots, PA-4, and PA-13) Carlsbad, CA Test # Nuclear Gauge (N) or Sand Cone (S) Test Date T I . t Test Location - . Soil Type Test of Elevation or Depth . (in feet) Moisture (%) Dry Density (pcf) Relative Compaction (%)l Comments . Field . Optimum . Field . Maximum . Obtained . Required 122 N 9/24/2014 PA-13 Lot 9 3 CF 78.0 12.9% 13.5% 112.0 118.0 95% 90% 123 N 9/24/2014 A-13 Lot 1'. 4 CF 79.0 10.5% 11.0% 115.3 123.5 93% 90% 124 N 9/24/2014 A-13 Lot = 3 CF 77.0 12.8% 13.5% 110.6 118.0 94% 90% 125 N 9/24/2014 A-13 Lot 3 3 CF 77.0 13.3% 13.5% 109.9 118.0 93% 90% 139 N 9/26/2014 A-13 Lot 2 CF 28.0 12.0% 10.5% 120.8 127.5 95% 90% 140 N 9/26/2014 A-13 Lot - - CF 79.0 16.8% 13.5% 110.2 118.0 93% 90% 141 N 9/26/2014 A-13 Lot - - CF 79.0 11.3% 10.5% 114.7 127.5 90% 90% 142 N 9/26/2014 A-13 Lot 10 4 CF 80.0 12.2% 11.0% 112.3 123.5 91% 90% 171 N 9/29/2014 A-13 Lot 21 - - CF 66.0 13.4% 13.5% 106.9 118.0 91% 90% 172 - - N 9/29/2014 A-13 Lot 18 - - CF 67.0 14.8% 13.5% 108.1 118.0 92% 90% 173 N 9/29/2014PA- 13 Lot 14 - 7 CF 68.0 19.4% 19.5% 102.9 111.5 92% 90% 174 - - N 9/29/2014 A-13 Lot 13 - CF 69.0 14.2% 13.5% 108.0 118.0 92% 90% 175 - - N 9/29/2014 A-13 Lot 12 - CF 73.0 11.8% 11.0% 116.5 123.5 94% 90% 176 - - N 9/29/2014 A-13 Lot 9 - 4 CF 8.0 11.2% 11.0% 115.7 123.5 94% 90% 177 - - N 9/29/2014 A-13 Lot CF 80.0 10.5% 11.0% 111.7 123.5 90% 90% 178 - - N 9/30/2014 A-13 Lot 19 = CF 68.0 9.9% 11.0% 118.2 124.5 95% 90% 179 - - N 9/30/2014 A-13 Lot 17 4 CF 68.0 10.7% 11.0% 113.0 123.5 91% 90% 180 - - N 9/30/2014 A-13 Lot 15 CF 69.0 10.2% 11.0% 117.5 124.5 94% 90% 181 - - N 9/30/2014 A-13 Lot 14 - - CF 69.0 9.3% 11.0% 119.0 124.5 96% 90% 182 N 9/30/2014 A-13 Lot 14 - - CF 70.0 13.1% 13.5% 108.9 118.0 92% 90% 186 N 10/1/2014 A-13 Lot 1 - - CF 69.0 11.8% 11.0% 111.9 123.5 91% 90% 187 N 10/1/2014 A-13 Lot 1 - CF 67.0 13.6% 13.5% 107.7 118.0 91% 90% 211 N 10/1/2014 A-13 Lot 4 CF 80.0 11.1% 11.0% 114.3 123.5 93% 90% 212 N 10/1/2014 A-13 Lot CF 81.0 9.5% 11.0% 113.0 123.5 91% 90% 213 N 10/1/2014 A13 Lot 10 3 CF 82.0 15.9% 13.5% 106.9 118.0 91% 90% 216 N 10/2/2014 A-13 Lot 1 4 CF 71.0 13.7% 11.0% 111.2 123.5 90% 90% 217 N 10/2/2014 A-13 Lot 1 4 CF 73.0 19% 11.0% 114.5 123.5 93% 90% 221 N 10/2/2014 PA-13 Lot 3 CF 81.0 14.6% 13.5% 109.3 118.0 93% 90% 222 N 10/2/2014 PA-13 Lot 10 5 CF 83.0 12.7% 11.0% 116.7 124.5 94% 90% 223 N 10/2/2014 PA-13 Lot 1 - CF 75.0 13.2% 11.0% 115.9 124.5 93% 90% 224 N 10/2/2014 PA-13 Lot 4 4 CF 81.0 10.3% 11.0% 114.7 123.5 93% 90% 225 N 10/2/2014 PA-13 Lot 8 - CF 83.0 14.2% 13.5% 107.1 114.5 94% 90% 295 N 10/8/2014 PA-13 Lot 11 7 CF 85.0 23.1% 19.5% 100.7 111.5 90% 90% 296 N 10/8/2014 PA-13 Lot CF 81.0 14.3% 11.01% 115.5 124.5 1 93% 90% 297 N 10/8/2014 PA-13 Lot 1 4 CF 77.0 11.3% 11.0% 112.6 123.5 91% 90% 298 N 10/8/2014 PA-13 Lot 1 CF 79.0 12.0% 11.0% 115.4 124.5 93% 90% 306 N 10/13/2014 PA-13 Lot 11 4 CF 84.0 12.9% 11.0% 113.7 123.5 92% 90% 307 N 10/13/2014 PA-l3 Lot ll - FG 0.0 14.1% 13.5% 110.4 118.0 94% 90% 308 N 10/13/2014 PA-l3 Lot lo 4 FG 0.0 9.2% 11.0% 116.9 123.5 95% 90% 309 N 10/13/2014 PA-13 Lot 9 4 FG 0.0 10.6% 11.0% 118.4 123.5 96% 90% 310 N 10/13/2014 PA-13 Lot 8 4 FG 0.0 9.3% 11.0% 112.7 123.5 91% 90% 331 N 10/13/2014 PA-13 Lot - -3 FG 0.0 12.2% 13.5% 1 110.9 118.0 94% 90% 332 N 10/13/2014 PA-13 Lot - - FG 0.0 12.0% 13.5% 112.5 118.0 95% 90% 333 N 10/13/2014 PA-13 Lot - FG 0.0 12.5% 13.5% 113.2 118.0 96% 90% 334 N 10/13/2014 PA-13 Lot 4 4 FG 0.0 11.4% 11.0% 116.3 123.5 94% 90% 335 N 10/13/2014 PA-13 Lot 4 FG 0.0 9.4% 11.0% 118.4 123.5 96% 90% 336 N 10/13/2014 PA-13 Lot 2 1 FG 1 0.0 18.6% 16.0% 111.1 117.5 95% 90% 337 N 10/13/2014 PA-13 Lot 1 1 FG 0.0 17.9% 1 16.0% 109.6 117.5 93% 90% 377 N 10/18/2014 PA-13 Lot 12 Slope 4 SF 82.0 11.5% 11.0% 112.9 123.5 91% 90% 378 N 10/18/2014 PA-13 Lot 23 Slope 1 SF 78.0 16.2% 16.0% 109.8 117.5 93% 90% 379 "J 10/18/2014 PA-13 Lot 24 Slope 4 SF 70.0 14.6% 11.0% 114.0 123.5 92% 90% 429 - 10/21/2014 PA-13 Lot 22 3 CF 70.0 13.5% 13.5% 106.4 118.0 90% 90% 430 - - 10/21/2014 PA-13 Lot 23 - CF 70.0 16.5% 16.0% 1 107.8 117.5 92% 90% 448 - - 10/24/2014 PA-13 Lot 19 _ 2 CF 70.0 22.2% 21.5% 95.5 102.0 941/6 90% 449 - - 10/24/2014 PA-13 Lot 16 2 CF 71.0 22.8% 21.5% 94.0 102.0 92% 90% 450 - - 10/24/2014 PA-13 Lot 12 4 - CF 75.0 11.6% 11.0% 111.5 123.5 90% 90% 526 10/28/2014 PA-4 South Slope 11 CF 100.0 12.9% 12.5% 112.1 122.0 92% 90% 8/11/2015 Page 2 of 5 LGC Valley, Inc. 2420 Grand Avenue, Suite F2, Vista, California 9208 760-599-7000 / Fax 760-599-7007 REPORT OF COMPACTION TEST DATA Print Date: Project No. Client. Project Name: Location: Reviewed by: August 10, 2015 133023-03 Toll Brothers Robinson Ranch (PA3&6 Model Lots, PA-4, and PA-13) Carlsbad, CA Test # Nuclear Gauge (N), or Sand Cone (S) Test Date I Test Location I L Soil Type Test of Elevation or Depth . (infeet) Moisture (%) Dry Density (pcf) Relative Compaction (%)I Comments Field Optimum Field Maximum Obtained Required 551 N 10/29/2014 A-13 Lot 24 4 CF 68.0 10.7% 11.0% 111.8 123.5 91% 90% 552 N 10/29/2014 A-13 Lot 23 3 CF 70.0 14.9% 13.5% 109.2 118.0 93% 90% 553 N 10/29/2014 A-13 Lot 22 3 CF 71.0 13.8% 13.5% 108.3 118.0 92% 90% 554 N 10/29/2014 A-13 Lot 24 4 CF 69.0 11.3% 11.0% 112.5 123.5 91% 90% 555 N 10/30/2014 A-13 Lot 14 4 CF 71.0 10.3% 11.0% 111.7 123.5 90% 90% 556 N 10/30/2014 A-13 Lot 17 4 CF 70.0 11.0% 11.0% 111.1 123.5 90% 90% 557 N 10/30/2014 A-13 Lot 20 5 CF 69.0 11.3% 11.0% 114.3 124.5 92% 90% 558 N 10/30/2014 A-13 Lot 22 3 FG 0.0 12.5% 13.5% 108.4 118.0 92% 90% 559 4 10/30/2014 A-13 Lot 23 3 FG 0.0 13.1% 13.5% 106.5 118.0 90% 90% 560 - - N 10/30/2014 A-13 Lot 24 5 FG 0.0 10.4% 11.0% 114.2 124.5 92% 90% 561 - - N 10/30/2014 A-13 Lot 12 4 FG 0.0 10.0% 11.0% 113.6 123.5 92% 90% 562 N 10/30/2014 A-13 Lot 13 4 FG 0.0 9.5% 11.0% 112.8 123.5 91% 90% 563 - - N 10/30/2014 A-13 Lot 14 4 FG 0.0 9.9% 11.0% 113.1 123.5 92% 90% 564 - - N 10/30/2014 A-13 Lot 15 5 FG 0.0 10.8% 11.0% 113.0 124.5 91% 90% 565 - - N 10/30/2014 A-13 Lot 16 5 FG 0.0 10.7% 11.0% 112.6 124.5 90% 90% 566 - - N 10/30/2014 A-13 Lot 17 10 FG 0.0 9.2% 10.0% 117.6 128.0 92% 90% 567 N 10/30/2014 A-13 Lot 18 4 FG 0.0 11.1% 11.0% 113.8 123.5 92% 90% 568 N 10/30/2014 A-13 Lot 19 4 FG 0.0 10.7% 11.0% 114.9 123.5 93% 90% 569 N 10/30/2014 A-13 Lot 20 :10: FG 0.0 11.4% 10.0% 117.3 128.0 92% 90% 570 N 10/30/2014 A-13 Lot 21 4 FG 0.0 10.8% 11.0% 111.2 123.5 90% 90% 633 N 11/6/2014 A-4 9 CF 118.0 12.3% 10.5% 117.3 127.5 92% 90% 634 N 11/6/2014 A-4 - - CF 117.0 13.1% 10.5% 116.1 127.5 91% 90% 694 N 11/12/2014 A-8 West Slope 10 CF 137.0 11.3% 10.0% 120.2 128.0 94% 90% 697 N 11/13/2014 PA-8 West Slope 10 CF 139.0 10.9% 10.0% 119.5 128.0 93% 90% 717 N 11/15/2014 PA-3 Lot 153 - - CF 96.0 12.1% 11.0% 114.4 124.5 92% 90% 739 N 11/17/2014 PA-3 Lot 114 Slope - - CF 107.0 14.5% 11.0% 114.0 124.5 92% 90% 751 N 11/18/2014 PA-8 West Slope 11 CF 144.0 13.1% 12.5% 111.9 122.0 92% 90% 765 N 11/19/2014 PA-3 Lot 114 - - CF 108.0 14.1% 11.0% 111.2 123.5 90% 90% 771 N 11/19/2014 PA-6 Lot 209 CF 118.0 13.7% 10.5% 117.4 127.5 92% 90% 772 N 11/19/2014 PA-6 Lot 211 - CF 120.0 13.3% 10.5% 116.1 127.5 91% 90% 787 N 11/20/2014 PA-3 Lot 103 10 CF 116.0 12.1% 10.0% 118.9 128.0 93% 90% 788 N 11/20/2014 PA-3 Lot 104 10 CF 114.0 12.3% 10.0% 117.9 128.0 92% 90% 804 N 11/24/2014 Robertson Rd Sta. 26+65 5 CF 110.0 13.9% 11.0% 115.5 124.5 93% 90% 807 N 11/24/2014 PA-8 128.0 16.2% 13.5% 104.7 114.5 91% 90% 808 N 11/24/2014 PA-8 130.0 15.1% 13.5% 106.4 114.5 93% 90% 820 N 11/25/2014 PA-8 West Slope 148.0 12.5% 11.0% 114.5 124.5 92% 90% 853 N 11/26/2014 PA-6 Lot 208 - - LU - - 144.0 12.4% 11.0% 12.3 124.5 90% 90% 854 N 11/26/2014 PA-6 Lot 209 5 142.0 12.9% 11.0% 15.3 124.5 93% 90% 855 N 11/26/2014 PA-6 Lot 207 146.0 15.1% 11.0% 13.2 124.5 91% 90% 872 N 12/1/2014 PA-8 - - 127.0 10.7% 11.0% 119.0 124.5 96% 90% 880 N 1219/2014 Robertson Rd Sta. 26+95 - - CF 112.0 18.2% 16.0% 110.9 - 17.5 94% 90% 881 N 12/9/2014 Roberston Rd Sta. 26+90 - - CF 111.0 18.9% 16.0% 110.7 - 17.5 94% 90% 884 N 12/10/2014 PA-3 Lot 104 7 CF 119.0 20.0% 19.5% 104.5 - 11.5 94% 90% 885 N 12/10/2014 Wellspring St Sta. 26+00 1 CF 118.0 19.0% 16.0% 106.1 117.5 90% 90% 888 N 12/10/2014 PA-6 Lot 247 5 CF 118.0 10.7% 11.0% 114.4 124.5 92% 90% 889 N 12/10/2014 Wellspring St Sta. 27+40 11 CF 117.0 16.5% 12.51/. 111.3 122.0 91% 90% 897 N 12/23/2014 PA-3 Lot 153 9 CF 122.0 14.2% 10.5% 116.3 127.5 91% 90% 898 N 12/23/2014 Roberston Rd Sta. 26+15 5 CF 123.0 15.1% 11.0% 114.7 124.5 92% 90% 899 N 12/23/2014 PA-3 Lot 103 11 CF 122.0 16.6% 12.5% 112.4 122.0 92% 90% 900 N 12/23/2014 PA-3 Lot 114 11 CF 123.0 17.0% 12.5% 111.9 122.0 92% 90% 905 - - 12/11/2014 Wellspring St Sta. 26+50 5 CF 122.0 14.6% 11.0% 115.3 124.5 93% 90% 906 12/11/2014 PA-3 Lot 104 1 CF 123.0 18.2% 16.5% 108.5 117.5 92% 90% 931 - - 12/29/2014 PA-3 Lot 104 11 CF 130.0 15.4% 12.5% 111.8 122.0 92% 90% 932 12/29/2014 PA-3 Lot 153 11 CF 132.0 16.0% 12.5% 110.0 122.0 90% 90% 933 - - 12/29/2014 Wellspring St Sta. 26+50 5 CF 131.0 13.4% 11.0% 115.8 124.5 93% 90% 934 - - 12/29/2014 PA-6 Lot 210 5 CF 133.0 12.8% 1 11.0% 115,0 124.5 92% 90% 935 12/29/2014 PA-6 Lot 246 5 CF 157.0 14.0% 1 11.0% 1 115.6 124.5 93% 90% 8/11/2015 Page 3of5 LGC Valley, Inc. 2420 Grand Avenue, Suite F2, Vista, California 92081 760-599-7000 I Fax 760-599-7007 REPORT OF COMPACTION TEST DATA Print Date: Project No. Client. Project Name: Location: Reviewed by: August 10, 2015 133023-03 Toll Brothers Robinson Ranch (PA3&6 Model Lots, PA-4, and PA-13) Carlsbad, CA Test # Nuclear Gauge (N) or Sand Cone (S) Test Date I Test Location Soil Type = Test of Elevation or Depth u.1 feet) Moisture (%) I Dry Density (pci) I Relative Compaction (% )l Comments Field Optimum Field Maximum Obtained Required 954 N 1/5/2015 PA-3 Lot 91 Slope 9 CF 141.0 12.4% 10.5% 116.9 127.5 92% 90% 955 N 1/5/2015 PA-3 Lot 81 - 9 CF 142.0 13.2% 10.5% 115.7 127.5 91% 90% 956 N 1/5/2015 PA-3 Lot 90 Slope - 5 CF 140.0 14.1% 11.0% 113.5 124.5 91% 90% 957 N 1/5/2015 PA-3 Lot 80 - 5 CF 139.0 15.2% 11.0% 114.9 124.5 92% 90% 958 N 1/6/2015 PA-6 Lot 206 9 CF 148.0 13.4% 10.5% 115.5 127.5 91% 90% 959 N 1/6/2015 PA-6 Lot 207 5 CF 147.0 15.4% 11.0% 113.7 124.5 91% 90% 965 N 1/6/2015 PA-4 11 CF 123.0 16.4% 12.5% 113.0 122.0 93% 90% 971 N 1/6/2015 PA-6 Lot 247 5 CF 127.0 11.2% 11.0% 114.6 124.5 92% 90% 972 N 1/6/2015 PA-6 Lot 211 5 CF 130.0 12.1% 11.0% 115.1 124.5 92% 90% 973 N 1/6/2015 PA-3 Lot 102 8 CF 143.0 17.6% 14.5% 109.3 115.5 95% 90% 974 N 1/6/2015 PA-3 Lot 101 8 CF 144.0 17.9% 14.5% 108.4 115.5 94% 90% 984 N 1/7/2015 A-6 Lot 211 4 CF 136.0 16.3% 11.0% 112.7 123.5 91% 90% 995 N 1/8/2015 A-3 Lot 102 1 CF 145.0 18.4% 16.0% 106.5 117.5 91% 90% 998 N 1/8/2015 A-3 Lot 90 - 8 CF 144.0 17.5% 14.5% 107.4 15.5 93% 90% 999 N 1/8/2015 A-3 Lot 91 8 CF 145.0 18.1% 14.5% 106.9 115.5 93% 90% 1003 N 1/9/2015 A-3 Lot 113 5 CF 123.0 14.2% 11.0% 112.7 124.5 91% 90% 1018 N 1/15/2015 A-6 Lot 206 5 CF 150.0 14.7% 11.0% 114.0 124.5 92% 90% 1019 N 1/15/2015 A-6 Lot 207 9 CF 148.0 9.0% 10.5% 116.7 127.5 92% 90% 1020 N 1/15/2015 A-6 Lot 208 5 CF 145.0 15.6% 11.0% 116.5 124.5 94% 90% 1021 N 1/15/2015 A-6 Lot 209 11 CF 143.0 15.8% 12.5% 110.7 122.0 91% 90% 1022 N 1/15/2015 A-6 Lot 210 11 CF 141.0 17.4% 12.5% 110.0 122.0 90% 90% 1023 N 1/15/2015 A-6 Lot 211 11 CF 139.0 15.6% 12.5% 112.1 122.0 92% 90% 1042 N 1/16/2015 Roberston Rd Sta. 26+05 4 CF 128.0 13.8% 11.0% 112.8 123.5 91% 90% 1061 N 1/19/2015 A-6 Lot 211 - - CF 139.5 14.5% 11.0% 113.5 124.5 91% 90% 1062 N 1/19/2015 A-6 Lot 210 - - CF 142.0 14.4% 11.0% 114.6 124.5 92% 90% 1 1063 N 1/19/2015 A-6 Lot 209 5 CF 144.0 13.2% 11.0% 114.2 124.5 92% 90% 1064 N 1/19/2015 A-6 Lot 208 - - CF 146.0 13.5% 11.0% 112.2 124.5 90% 90% 1065 N 1/19/2015 A-6 Lot 207 - - CF 149.0 14.3% 11.0% 113.0 124.5 91% 90% 1066 N 1/19/2015 A-6 Lot 206 - - CF 151.0 13.3% 11.0% 113.9 124.5 91% 90% 1088 N 1/20/2015 A-3 Lot lol - - CF 146.0 14.3% 10.5% 118.7 127.5 93% 90% 1089 N 1/20/2015 A-3 Lot 113 - - CF 138.0 15.0% 10.5% 117.8 127.5 92% 90% 1096 N 1/21/2015 A-3 Lot 114 11 CF 136.0 13.4% 12.5% 110.3 122.0 90% 90% 1126 N 1/23/2015 A-3 Lot 91 11 CF 145.0 16.1% 12.5% 110.4 122.0 90% 90% 1127 N 1/23/2015 A-3 Lot 90 5 CF 147.0 14.2% 11.0% 113.5 124.5 91% 90% 1128 N 1/23/2015 A-3 Lot 89 5 CF 149.0 14.7% 11.0%1 112.9 124.5 91% 90% 1161 N 1/26/2015 A-6 Lot 206 11 FG 0.0 14.2% 12.5% 110.4 122.0 90% 90% 1162 - N 1/26/2015 A-6 Lot 207 5 FG 0.0 12.8% 11.0% 114.5 124.5 92% 90% 1163 - N 1/26/2015 A-6 Lot 208 11 FG 0.0 12.9% 12.5% 110.8 122.0 91% 90% 1 1164 _N 1/26/2015 PA-6 Lot 209 5 FG 0.0 10.1% 11.0% 113.1 124.5 91% 90% 1165 N 1/26/2015 PA-6 Lot 210 9 FG 0.0 14.7% 10.5% 116.3 127.5 91% 90% 1170 - N 1/27/2015 PA-3 Lot 88 11 CF 149.0 12.4% 12.5% 109.9 122.0 90% 90% 1234 N 1/30/2015 PA-6 Lot 211 5 FG 0.0 12.1% 11.0% 113.1 117.0 97% 90% 1318 t'. 2/10/2015 PA-3 Lot 103 - - CF 142.0 13.7% 11.0% 113.7 124.5 91% 90% 1319 N 2/10/2015 PA-3 Lot 104 CF 143.0 14.1% 11.0% 113.9 124.5 91% 90% 1320 N 2/10/2015 PA-3 Lot 113 5 CF 140.0 13.3% 11.0% 116.5 124.5 94% 90% 1331 N 2/10/2015 PA-3 Lot 114 4 CF 138.0 14.1% 11.0% 114.9 123.5 93% 90% 1333 N 2/10/2015 PA-3 Lot 112 4 CF 140.0 14.4% 11.0% 113.9 123.5 92% 90% 1340 N 2/11/2015 PA-3 Lot 78 11 CF 159.0 15.2% 12.5% 1 111.1 122.0 1 91% 90% 1341 N 2/11/2015 PA-3 Lot 77 ii CF 161.0 15.0% 12.5% 1 110.5 122.0 91% 90% 1342 N 2/11/2015 PA-3 Lot 79 4- CF 158.0 14.6% 11.0% 115.8 123.5 94% 90% 1343 N 2/11/2015 PA-3 Lot 80 4 CF 157.0 14.5% 11.0% 112.6 123.5 91% 90% 1472 N 2/20/2015 PA-3 Lot 112 - : FG 0.0 11.4% 11.0% 114.4 123.5 93% 90% 1473 N 2/20/2015 PA-3 Lot 113 - : FG 0.0 13.1% 11.0% 113.0 124.5 91% 90% 1474 N 2120/2015 PA-3 Lot 114 - - FG 0,0 14.1% 10.5% 117.2 127.5 92% 90% 1576 N 2/26/2015 PA-3 Lot 100 9 FG 0. 11.4% 10.5% 116.7 127.5 92% 90% 1577 N 2/26/2015 PA-3 Lot 101 FG 0.0 10. 0 1% 10.59/6 117.7 127.5 92% 90% 1578 N 2/26/2015 PA-3 Lot 102 - - FG 0.0 12.6% 1 10.5% 1 118.2 127.5 1 93% 1 90% 1 8/11/2015 Page 4 of 5 LGC Valley, Inc. 2420 Grand Avenue, Suite P2, Vista, California 92081 760-599-7000 / Fax 760-599-7007 REPORT OF COMPACTION TEST DATA Print Date: Project No. Client. Project Name: Location: Reviewed by: August 10, 2015 133023-03 Toll Brothers Robinson Ranch (PA3&6 Model Lots, PA-4, and PA-13) Carlsbad, CA = Test # Nuclear Gauge (N) or Sand Cone (S) 1 Test Date I . I Test Location Soil Type Test of Elevation or Depth . (in feet) I Moisture (%) I Dry Density (pct) .s . Field Optimum . Field 0 Maximum Obtained Relative Compaction (%FC o7mmeRequired 1579 N 2/26/2015 A-3 Lot 103 FG 1 0.0 9.3% 10.5% 118.0 127.5 93% 90% 1580 N 2/26/2015 A-3 Lot 104 FG 0.0 11.6% 10.5% 114.8 127.5 90% 90% 1584 N 2/26/2015 A-3 Lot 80 FG 0.0 14.3% 11.0% 114.7 124.5 92% 90% 1585 N 2/26/2015 A-3 Lot 79 F FG 0.0 12.6% 11.0% 112.1 124.5 90% 90% 1586 N 2/26/2015 A-3 Lot 78 FG 0.0 12.5% 11.0% 115.0 124.5 92% 90% 1587 N 2/26/2015 A-3 Lot 77 5 FG 0.0 10.9% 11.0% 115.9 124.5 93% 90% 1588 N 2/26/2015 A-3 Lot 81 - - FG 0.0 11.7% 11.0% 114.4 124.5 92% 90% 1592 N 2/26/2015 A-3 Lot 111 - - FG 0.0 11.5% 11.0% 112.1 124.5 90% 90% 1593 N 2/26/2015 A-3 Lot 112 - - FG 0.0 13.0% 11.0% 112.7 124.5 91% 90% 1594 N 2/26/2015 A-3 Lot 113 - - FG 0.0 13.2% 11.0% 118.0 124.5 95% 90% 1595 N 2/26/2015 A-3 Lot 114 - - FG 0.0 11.4% 11.0% 114.5 124.5 92% 90% 1711 N 3/16/2015 A-3 Lot 88 13 FG 0.0 11.0% 11.0% 117.9 125.5 94% 90% 1712 N 3/16/2015 A-3 Lot 89 13 FG 0.0 11.9% 11.0% 117.6 125.5 94% 90% 1713 N 3/16/2015 A-3 Lot 90 13 FG 0.0 10.5% 11.0% 115.9 125.5 92% 90% 1714 N 3/16/2015 A-3 Lot 91 13 FG 0.0 11.6% 11.0% 117.5 125.5 94% 90% 2136 N 5/1/2015 A-4 5 CF 127.0 11.0% 11.0% 113.0 124.5 91% 90% 2137 N 5/1/2015 A-4 13 CF 128.0 12.7% 11.0% 113.8 125.5 91% 90% 2138 N 5/1/2015 A-4 13 CF 127.0 12.9% 11.0% 114.0 125.5 91% 90% 2139 N 5/1/2015 A-4 11 CF 125.0 13.1% 12.5% 112.9 122.0 93% 90% 1 Material: S=Soil, AC=Asphalt Concrete, ATB =Asphalt Treated Base, AB =Aggregate Base, STS =Cement Treated Soil, LTS = Lime Treated Soil, 0 = Other Test of: CF = Compacted Fill, FG = Finish Grade, SF = Slope Face, N = Native Soil, U = Utility Trench, W = Wall Backfill, SC = Sidewalk, Curb, Gutter, 0 = Other KEY: FSG = Finish SubGrade, FS = Finish Surface, FBG = Finish BaseGrade, BOF = Bottom of Footing, TOW= Top of Wall N = Nuclear Gauge, S = Sand Cone Notes: Tests were performed by a nuclear density gauge in accordance with the ASTM 02922 method or Sand Cone Method (ASTM D 1556). The maximum dry density and optimum moisture data was tested in accordance with the ASTM 01557 test method (Modified Proctor). The field density test results represent the moisture content and density only at the depths and locations reported. No guarantee or warranty of the contractor's work is made or implied. 8/11/2015 Page 5of5 I PLATE 6i7 I 4f9a fJ £6CV4LLE/NC ~0 1 *C41 I I ir MKS SIM 20 Aim I _ A Mill. IZ4 gill poi IM 'a N --- M. ME is, IMMOM"I I _ _ _ _ • LGC UN Sg -. MHJI • 525 - EXPLAAJA TlOtV 486 Field Density Test Location Approximate Removal Bottom Elevation -' Limits of Report .0 —//---_, Limits of Compacted Fill \\/ç•625 •527 593 SSS \' 14 8l2 - 86 85 - LOT 711 175 106 XO2 L /4/ 805 fo 56 95 , / /86 222 309 221 / ' . ) - 5 59ff3 7a7 -69.1 182 / 562 331i 0T6 7 / 1- 211 563 14 555 ,ff S t -x/ TY°5 139-i 2 _81.q 165 x ITT 5 43 / Efl 121 iö 597 558 140 5P IT 8 33 1449 46 5 A. ' 6611 ly LOT 15 43VOT2J 554 652 585 687 A L / 104' 4olv LOT 17 556 - '6O LO 97 II ii f / 559 2 567 552 6 379 / g 589 / WI 75 448 ç ... / / 5FT/ /72 • 657 LOT 20 17j/ 4cw 50 ~4 171 -: / MH. H l -658 j.7 557 57AT21 GV 1A 100-4 - 550 552 72 558 552 - 52Z __5__ •545 -- - 5'_ sJ5 - -- - 512 -- 59 / - - - - •622 545 515 520 I PLATE 525 625 -- - 59 - - 512 -- —'•." 5, EXPI ANA TION A PUIT 486 Field Density Test Location Approxñnate Removal Bottom Elevation £L' Liwis of Report Li/ts of Compacted Fill