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HomeMy WebLinkAboutCT 12-05; LA COSTA RESIDENTIAL; GEOTECHNICAL; 2013-07-22July 22,2013 Ms. April Tomillo Taylor Morrison 8105 Irvine Center Drive, Suite 1450 Irvine, California 92618 Project No. 12043-01 RECORD COPY Initial Date Subject: Geotechnical Review, Acceptance of Geotechnical Consultant of Record, and Response to Review Questions by the City of Carlsbad for Proposed La Costa Town Center Residential Development, Carlsbad, California Geotechnical Review and Acceptance of Geotechnical Consultant of Record In accordance with your request, LGC Geotechnical, Inc. has reviewed the referenced reports by Leighton and Associates, Inc. (attached). It is our professional opinion that the work performed for development of the area to the existing condition was in accordance with the standard of care for the industry. With this letter, LGC Geotechnical accepts the work performed at the subject site to date and takes on the role of geotechnical consultant of record. The development of the site should be performed in accordance with the recommendations in the attached reports by Leighton unless superseded by this office during construction. Response to Review Questions by the City of Carlsbad It is our understanding that the City of Carlsbad has three outstanding review questions. These questions are attached to this report, and the responses to the questions have been written directly adjacent to the questions. 00 o z o UJ o 120 Calle Iglesia, Suite A, San Clemente, CA 92672 11 (949) 369-6141 fif www.lgcgeotechnical.com Should you have any questions, please do not hesitate to contact our office. We appreciate this opportunity to be of service. Sincerely, LGC Geotechnical, Inc. Tim Lawson, CEG 1821, GE 2626 Geotechnical Engineer/Geologist TJL/kmh Attachments: Leigliton and Associates, Inc., Geotechnical Update Investigation, Proposed La Costa Town Center Residential Development, Carlsbad, California, Project No. 042631-001, dated September 27, 2012. Leighton and Associates, Inc., Geotechnical Update and Addendum to Geotechnical Investigation, Proposed La Costa Town Center Residential Development, Carlsbad, California, Project No. 042631-001, dated November 16, 2012. Leighton «& Associates, Inc., Response to City Review Comments, La Costa Town Square, Carlsbad, California, Project No. 042631-001, dated February 1,2013. Review Questions by the City of Carlsbad, California (written directly on 3 pages of previous Leighton Report). Southern California Soil & Testing, Inc., As-Graded Geotechnical Report, La Costa Town Center, Rancho Santa Fe Road and La Costa Avenue, Carlsbad, California, SCS&TNo. 0411014, Report No. 4, dated April 20, 2004. Distribution: (1) Addressee (via email) (1) Latitude 33 Planning and Engineering (via email) Attn: Mr. Armando Urquidez Project No. 12043-0! Page 2 July 22, 2013 GiCOTECHNICAL UPDATE AND ADDENDUM TO GEOTECHNICAL INVESTIGATION PROPOSED LA COSTA TOWN CENTER RESIDENTIAL DEVELOPMENT, CARLSBAD, CALIFORNIA Prepared for: TAYLOR MORRISON OF CA, LLC 8105 Irvine Center Drive, Suite 1450 Irvine, California 92618 Project No. 042631-001 November 16, 2012 4 Leighton and Associates, Inc. A LEIGHTON GROUP COMPANY Leighton and Associates, Inc. A LEIGHTON GROUP COMPANY November 16, 2012 Project No. 042631-001 Taylor Morrison of CA, LLC 8105 Irvine Center Drive, Suite 1450 Irvine, California 92618 Attention: Ms. April Tomillo Subject: Geotechnical Update and Addendum to Geotechnical Investigation Proposed La Costa Town Center Residential Development Carlsbad, California References: Leighton and Associates, Inc. 2012, Geotechnical Investigation, Proposed La Costa Town Center Residential Development, Carlsbad, California, Project No. 042631-001, dated March 3, 2012 Latitude 33, 2012, Grading Plans, La Costa Town Center, Received October 2012 In accordance with your request and authorization, we have prepared this geotechnical update and addendum letter for the proposed La Costa Town Center, Carlsbad, California. As part of this update and addendum, we attended a project meeting on October 16, 2012, reviewed the above- referenced geotechnical report along with recent project grading plans. As requested by Taylor Morrison, the purpose of our update letter is revise geotechnical recommendations for building pad over-excavation from 4 feet to 3 feet, and to update our geotechnical map and geologic cross-section to new building pad elevations that have recently been raised. Based on our review of the current grading plans for the project prepared by Latitude 33, (Latitude 33, 2012), we understand the proposed development will include construction of thirty-two single- family residential buildings and associated improvements including roadways, building patios, driveways, parking areas, concrete flatwork, underground utilities, landscaping, etc. We also 3934 Murphy Canyon Road, Suite B205 • San Diego, CA 92123-4425 858.292.8030 • Fax 858.292.0771 c www.leightongroup.com 042631-001 understand that the proposed buildings will be two story structures and will likely be constructed with conventional or post-tension foundations. Based on the preliminary development plans, we anticipate the proposed finish grade elevations will be within a 1 to 5 feet of the existing mass- graded pad elevations. In addition, the proposed building pad grades on recent grading plans were raised approximately 1 foot. Addendum Recommendations In general, the geotechnical conditions of the site remain essentially as presented in the referenced geotechnical report, and it is our professional opinion that our previous geotechnical recommendations are still applicable and should be incorporated into the design, grading and construction of the proposed development, including addendum recommendations provided below. Note that we also recommend that the grading, retaining wall, and foundation plans be reviewed by Leighton prior to commencing construction. • Mitigation of Cut/Fill Transition Conditions and Building Pad Overexcavation In order to reduce the potential for differential settlement in areas of transition or cut-fill building pads and to remove metavolcanic rock in cut areas, we recommend that the entire cut portion of the building pad be overexcavated to a minimum depth of 3 feet below finished grade and replaced with properly compacted fill. This depth may be increased depending on adjacent fill depth as part of the recommended removals of artificial fill beneath the building pads. The overexcavation and recompaction should laterally extend at least 5 feet beyond limits of the building footprint. Based on our review of the updated grading plans, we have provided an approximate location of building pads overexcavations (Plate 1). Note that Leighton previously recommended 4 foot pad overexcavations was to mitigate risk of encountering difficult to non-rippable rock, minor grade variations during grading and to facilitate foundation and utility trench excavations. For deep utilities, we recommend the utility adjustments (streets, etc.) be over-excavated a minimum of 1 foot below the deepest utility. The recommendations provided in this update letter and our previous geotechnical report are based on preliminary design information and subsurface conditions provided during previous site As-graded reports. The interpolated subsurface conditions should be checked in the field during grading and/or construction. Construction observation of all onsite excavations and field density testing of all compacted fill should be performed by a representative of this office. -2- Leighton 042631-001 If you have any questions regarding our update letter, please contact this office. We appreciate this opportunity to be of service. Respectfully submitted, LEIGHTON AND ASSOCIATES, INC. William D. Olson, RCE 45283 ^^isT^^ Associate Engineer Mike D. Jensen, CEG 2457 Project Geologist Attachment: Figures - Geotechnical Map and Geologic Cross-section Appendix A - Geotechnical Report Distribution: (6) Addressee Leighton Lusardi Construction April 20, 2004 La Costa Town Center SCS& T No. 0411014-4 Page 4 1.2.5. Fill Slopes Fill and fill-over-cut slopes were constructed at several locations within the subject site. In order to provide for a uniformly compacted slope surface, the face of the slopes were track-walked with a Caterpillar 08 bulldozer. Field density tests taken in the slope surface indicated at least 90 percent relative compaction. 1.2.6. Cut Slopes Cut slopes were observed by an SCS&T geologist and found to be tree of significant adverse geologic conditions. 1.2.7. Storm Drain Trench Backfill Three storm drains were installed for this project. Storm Drain A is located on site and Storm Drains B and C are located east of the new Rancho Santa Fe Road in the borrow site. The backfill soils for the storm drain trenches were tested by our firm for relative compaction. The approximate locations of the trench backfill tests for Storm Drain A are noted on Plate No, 1 A. The approximate locations of the trench backfill tests for Storm Drains B and C are noted on Plate No. 2. The storm drain in-place density tests have been labeled "SD". Typically, the soils generated from the borrow pit were used as backfill material. The backfill material was compacted to at least 90 percent of maximum dry density determined in accordance with ASTM D 1557-00 procedures. Compaction was achieved primarily by means of an excavator-mounted sheepsfoot compaction wheel and other heavy construction equipment. 1.2.8. Subdrain Groundwater was encountered in the western corner of the subject site at the bottom of the removal excavation. A subdrain was installed in this area due to the presence of the groundwater. The subdrain consisted of a 4-inch diameter perforated pipe (SDR-35), surrounded by about 6 cubic feet of crushed rock per lineal foot, wrapped in filter fabric. The subdrain was connected to an existing storm drain inlet adjacent to the existing Rancho Santa Fe Road. Approximately 12 feet of fill was placed prior to construction of the subdrain to maintain fall into the storm drain pipe. The approximate location and flow line elevations of the subdrain are indicated on Plate No. 1. An abandoned storm drain pipe was encountered in the narrow area at the northeastern corner of the site. The eastern portion of the pipe was removed. The excavation resulting from the removal was backfilled with compacted fill. In-place density tests indicated relative compaction values of 90 percent or greater. The western portion of the storm drain was left in place because it connected to a live storm drain box slightly to the southeast of existing Rancho Santa Fe Road. It is our understanding that the southeast terminus of this segment was capped with Lusardi Construction ^P"' ^0, 2004 La Costa Town Center SCS& T No. 0411014-4 Page 5 concrete at the point where it exits the southeast-facing cut slope. SCS&T did not observe the capping of the pipe. 1.3. FIELD OBSERVATION AND TESTING Field obsen/ations and density tests were performed by a representative of SCS&T during the grading operations. The density tests were performed according to ASTM D 2922-01 (nuclear gauge) procedures. Rock corrections were applied as necessary as described in Section 1.4. In- place density testing was limited within the rock/soil fills due to excessive rock content. Where testing was impractical, the fill was observed as it was placed and in potholes to verify that sufficient moisture content, soil matrix material and uniform compaction effort had been achieved. Test locations are shown on Plate Nos. 1 and 2, while the test results are shown on Plate Nos. 3 through 6. The accuracy of the in-situ density test locations and elevations is a function of the accuracy of the survey control provided by others. Unless othenwise noted, their locations and elevations were determined by pacing and hand level methods and should be considered accurate only to the degree implied by the method used. As used herein, the term "obsen/ation" implies only that we observed the progress of work we were involved with, and performed field density tests, which in conjunction with our obsen/ations were the basis for our opinion as to whether the work was performed in substantial conformance with the geotechnical recommendations and the requirements of the applicable agencies. 1.4. LABORATORY TESTS Maximum dry density determinations were performed on representative samples of the soils used in the compacted fills according to ASTM D 1557-00, Procedure A and C. Procedure A is used when the soil contains 20 percent or less by mass of material retained on the #4 sieve. This procedure specifies that a 4-inch diameter cylindrical mold of 1/30 cubic foot volume be used and that the soil tested be placed in 5 equal layers wrtth each layer compacted by 25 blows utilizing a 10-pound hammer with an 18-inch drop. Procedure C is used when the soil contains more than 20 percent by weight of material is retained on the 3/8-inch sieve and less than 30 percent by mass is retained on the 3/4-inch sieve. This procedure specifies that a 6-inch diameter cylindrical mold of 1/13 cubic foot volume be used and that the soil tested be placed in 5 equal layers with each layer compacted by 56 blows utilizing a 10-pound hammer with an 18-inch drop. The results of these tests, presented on Plate No. 5, were used in conjunction with the field density tests to determine the degree of relative compaction of the compacted fill. Rock corrections were applied to the soil samples having not more than 40 percent by weight retained on the #4 sieve or not more than 30 percent by weight retained on the 3/4-inch sieve according to ASTM D 4718-87 (reapproved 1994) procedures. The results of these tests, as Lusardi Construction April 20, 2004 La Costa Town Center SCS& T No. 0411014-4 Page 6 presented on Plate No, 5, were used in conjunction with the field density tests to determine the degree of relative compaction of the compacted fill. The expansion potential of the prevailing foundation soils was determined using UBC Test Method 18-2. The results of these tests, shown on Plate No. 5 indicate expansion potential ranging from medium to high. The recommendations contained herein reflect these conditions. Results of soluble sulfate tests are pending. 1.5. AS-BUILT GEOLOGY Based on the results of on-site geological observations, the following conclusions are presented: 1) The geological conditions exposed at the site were found to be similar to those described in the referenced geotechnical report(s). 2) Cut slopes were observed and found to be free of significant adverse geologic conditions. 3) All areas which were to receive fill were observed and found to be suitable for the support of the proposed structural fill and settlement sensitive improvements. 4) To the best of our knowledge, the site is geologically suitable for the proposed construction. 1.6. REMAINING WORK The following operations remain to be completed. It is recommended that field obsen/ations and relative compaction tests be performed during these operations to verify that they are performed in accordance with job requirements and local grading ordinances. Placement of additional fill to achieve proposed grades; Backfilling of underground utility trenches. 2. CONCLUSIONS To the best of our knowledge based on our field observations and the in-place density test results, the subject grading was performed in substantial accordance with the recommendations contained in the referenced geotechnical reports, the City of Carlsbad Grading Ordinance, and the Uniform Building Code. A site plan depicting the currently-proposed scheme for the future development of the subject site is included herein as Plate No. IB. The recommendations presented below are based upon this development scheme. Any significant changes to the development scheme should be reviewed by SCS&T so that recommendations can be modified as necessary. In particular, it is noteworthy that the building pad undercuts were designed to accommodate the specific building locations and finish Lusardi Construction April 20, 2004 La Costa Town Center SCS&T No. 0411014-4 Page 7 floor elevations depicted on Plate No. 1B. Modifications to the locations or elevations of the buildings may necessitate additional undercuts, including possible additional blasting. 3. RECOMMENDATIONS 3.1. FOUNDATIONS 3.1.1. General Shallow foundations may be utilized for the support of the proposed improvements. The footings for the proposed structures should have a minimum depth of 24 inches below lowest adjacent pad grade. Footings for exterior improvements such as retaining walls may have a minimum depth of 18 inches. A minimum width of 12 inches and 24 inches is recommended for continuous and isolated footings, respectively. A bearing capacity of 2000 pounds per square foot (psf) may be assumed for said footings. The bearing capacities may be increased by 1/3 when considering wind or seismic forces. Footings adjacent to or within slopes should be deepened such that a minimum horizontal distance of 7 feet exists between the bottom outside footing edge and the face of the slope. For retaining wall footings, the minimum distance shouki be increased to 10 feet. 3.1.2. Reinforcement Continuous footings should be reinforced with at least two No. 5 bars positioned near the bottom of the footing and at least two No. 5 bars positioned near the top of the footing. This reinforcement is based on geotechnical considerations and is not intended to be in lieu of reinforcement necessary to satisfy structural considerations. 3.1.3. Seismic Design Factors Based upon the 1997 edition of the Uniform Building Code, the following seismic design factors are considered appropriate for the subject site. Seismic Zone 4: Z=0.40 Source Fault: Rose Canyon Fault Zone Seismic Source Type: B Soil Profile Type: Sc Distance to Seismic Source: 11 kilometers Near-Source Factor Na=1.0 Near-Source Factor Nv=1.0 It is likely that the site will experience the effects of at least one moderate to large earthquake during the life of the proposed structure. Lusardi Construction April 20, 2004 La Costa Town Center SCS& T No. 0411014-4 Pages 3.1.4. Foundation Excavation Observation It is recommended that all foundation excavations be approved by a representative from this office prior to forming or placing reinforcing steel. 3.1.5. Settlement Characteristics The anticipated total and differential settlements may be considered to be within tolerable limits provided the recommendations presented in this report are followed. It should be recognized that minor cracks normally occur in concrete slabs and foundations due to shrinkage during curing or redistribution of stresses and some cracks may be anticipated. Such cracks are not necessarily an indication of excessive vertical movements. 3.1.6. Expansion Characteristics Expansion Index tests indicate expansion potentials ranging from medium to high. The recommendations contained in this report reflect a highly expansive condition. 3.1.7. Foundation Plan Review Foundation plans should be submitted to this office for review to ascertain that the recommendations contained in this report are implemented and no revised recommendations are necessary due to changes in the development scheme. 3.1.8. Soluble Sulfates Soluble sulfate tests are pending. Appropriate recommendations will be provided as necessary once results are available. 3.2. SLABS-ON-GRADE 3.2.1. Interior Concrete Slabs-on-Grade Concrete slabs-on-grade should have a minimum thickness of 5 inches and be reinforced with at least No. 4 reinforcing bars placed at 18 inches on-center each way. Slab reinforcement should be placed approximately at mid-height of the slab and should extend at least 12 inches into the adjacent footings. Slabs underlain by retaining wall backfill should have a minimum thickness of 5 inches. In this case, minimum reinforcement should consist of No. 4 bars placed at 18 inches on center each way. Slabs-on-grade should be underlain by a 4-inch thick blanket of clean, poorly graded, coarse sand (sand equivalent = 30 or greater) or crushed rock. This blanket should consist of no more than 20 percent and 10 percent passing the #100 and #200 sieves, respectively. Where moisture sensitive floor coverings are planned, vapor retardant should be placed over the sand layer. An additional 2 inches of sand should be placed over the vapor retardant. Typically, visqueen is used as a vapor retardant. If visqueen is used, a minimum 10- mil is recommended. 3i' Lusardi Construction April 20, 2004 La Costa Town Center SCS& T No. 0411014-4 Page 9 It is our understanding that the moisture barrier described above will allow the transmission of 6 to 12 pounds of moisture per 1000 square feet per day through the slab under normal conditions. Moisture emissions may vary widely depending upon factors such as concrete type and subgrade moisture conditions. If this amount of moisture is excessive, additional recommendations will be provided by this office. It is recommended that moisture emission tests be performed prior to the placement of floor coverings to ascertain whether moisture emission values are within the manufacturer's specifications. In addition, over-watering should be avoided, and good site drainage should be established and maintained to prevent the build-up of excess sub-slab moisture. 3.2.2. Exterior Concrete Slabs-on-Grade Exterior concrete slabs should have a minimum thiickness of 4 inches and should be reinforced with at least No. 3 bars at 18 inches on center each way. All slabs should be provided with weakened plane joints. Joints should be placed where cracks are anticipated to develop naturally, and should be in accordance with the American Concrete Institute (ACI) guidelines Section 3.13. Alternative patterns consistent with ACI guidelines also can be used. The landscape architect can be consulted in selecting the final joint patterns to improve the aesthetics of the concrete slabs-on-grade. A concrete mix with a 1 -inch maximum aggregate size and a water/cement ratio of less than 0,6 is recommended for exterior slabs. A lower water content will decrease the potential for shrinkage cracks. It is strongly suggested that the driveway concrete mix have a minimum compressive strength of 3,000 pounds per square inch. This suggestion is meant to address early driveway use prior to full concrete curing. Both coarse and fine aggregate should conform to the "Standard Specifications for Public Works Construction" ("Greenbook"), prepared by Public Works Standards, Inc. It would be prudent to consult with a materials engineer regarding the review of the concrete mix design, and to retain a registered special inspector to observe the placement of concrete. Special attention should be paid to the method of curing the concrete to reduce the potential for excessive shrinkage and resultant random cracking. It should be recognized that minor cracks occur normally in concrete slabs and foundations due to shrinkage during curing and redistribution of stresses. Some shrinkage cracks should be expected and are not necessarily an indication of excessive vertical movement or structural distress. Factors that contribute to the amount of shrinkage that takes place in a concrete slab include joint spacing, depth, and design; concrete mix components; water/cement ratio and surface finishing techniques. According to the undated "Technical Bulletin" published by the Southern California Rock Products Association and Southern California Ready Mixed Concrete Lusardi Construction April 20, 2004 La Costa Town Center SCS&TNo. 0411014-4 Page 10 Association (see Appendix B), flatwork formed of high-slump concrete (high water/cement ratio) utilizing 3/8-inch maximum size aggregate ("Pea Gravel Grouf mix) is likely to exhibit extensive shrinkage and cracking. Cracks most often occur in random patterns between construction joints. 3.3. EARTH RETAINING WALLS 3.3.1. Foundations The recommendations presented in the foundation section of this report are also applicable to earth retaining structures. 3.3.2. Passive Pressure The passive pressure for retaining wall foundations extending into compacted fill soils may be considered to be 300 psf per foot of depth, up to a maximum of 1500 psf, This pressure may be increased one-third for seismic loading. The coefficient of friction for concrete to soil may be assumed to be 0.25 for the resistance to lateral movement. When combining frictional and passive resistance, the friction should be reduced by 1/3. The upper 12 inches of soil should not be considered when calculating passive pressures for exterior walls. 3.3.3. Active Pressure The active soil pressure for the design of unrestrained and restrained earth retaining structures with level backfills may be assumed to be equivalent to the pressure of a fluid weighing 35 and 55 pounds per cubic foot (pcf), respectively. An additional 15 pcf should be added to the aforementioned values for 2:1 (horizontal to vertical) sloping backfills. These pressures do not consider any other surcharge loads. If any are anticipated, this office should be contacted for the necessary increase in soil pressure. These values also assume a granular and drained backfill condition. 3.3.4. Retaining Wall Subdrains and Waterproofing Retaining wall subdrains should be installed in accordance with the detail presented on Plate No. 7. Waterproofing specifications and details should be provided by the project architect. The geotechnical engineer should be requested to verify that retaining wall subdrains and waterproofing have been properly installed. 3.3.5. Baclcfill All backfill soils should be compacted to at least 90 percent relative compaction. Expansive or clayey soils should not be used for backfill material. Walls should not be backfilled until the masonry has reached an adequate strength. Lusardi Construction April 20,2004 La Costa Town Center SCS&TNo. 0411014-4 ——^ : Page 11 3.3.6. Factor of Safety The above values, with the exception of the allowable soil bearing pressure, do not include a factor of safety. Appropriate factors of safety should be incorporated into the design to prevent walls from overtuming and sliding. 4. LIMITATIONS This report covers only the sen/ices performed between January 16 and March 19. 2004. Our opinions presented herein are based on our obsen/ations and the relative compaction test results and are limited by the scope of the sen/ices that we agreed to perform. Our sen/ices were performed in accordance with the currently accepted standard of practice and in such a manner as to provide a reasonable measure of the compliance of the grading and backfill operations with the job requirements. No warranty, express or implied, is given or intended with respect to the sen/ices which we have performed, and neither the performance of those sen/ices nor the submittal of this report should be constmed as relieving the contractor of the responsibility to conform with the job requirements. Our sen/ices were generally performed on an "on-call" basis. Therefore, the in-place density tests performed by our field representative can only be construed as representative of the areas tested which are shown on the attached plates. Should you have any questions regarding the contents of this report, or if we may be of further assistance, please contact our office at your convenience. Respectfully submitted, SOUTHERN CALIFORNIA SOIL AND TESTING, INC. 'AdISf, RCE 360?^ Michael P. Farr, CEG 1938 Vice Pr^ident x Senior Engineering Geologist DAB:MPF:sd (4) Addressee (2) Aspen Properties, Attn: Mr. Wayne George Six 1 SCS&,T LEGEND '^SS; (tyiproijinsde Location oi in-Ptoce Density Test i3S2.0i Appro«jmato Remowal Bottom Bevation WSBi i^entovatl Bottotn EUivaHom Ftam O'Day Const^ntji Survey Points (rowmted off to the rwarest 0.5 fwrtj (fOI?^ Apfyroximn^ Locaftot* erf Sttwni Oraiirt Density Test " """"1 ;^5proximat« Um^ aif Kcyway mmm i— AfspToximitt Oeo)og<c ConQKt I Removal Limtt —-*— Appreutimate Stitxfcain tocatton wtth DJrerCtioft of Ffow Qaf Compacted m tram Recwt GrjKJitvg Jsp Sanfiago Peak Votcantcx / -if*"" t N* IP —^ i Qaf Jsp i / • 1 Qef / / / ''\/' / . / '\ A North 1" = 60' SOUTHERN CALIFORNIA SOIL & TESTING, INC. ia toftr Tom Cmstr gy" ~Om^-/QOU I Pule: 4/2!/S4 • I '-•r-'-issSB "i ~ ' "•I, "•— ' 'i '"'•\ \S • /V j/jp-: -to— It SCS&T LEGEND ("SD15) Approximate Location of Storm Trench Density Test (mm.'! ! ElfCTFOnC DATA n£S AFE FOR PSIIPOtCe I mr AMD M£ nor 10 Bt USED FOfi HCHaa^fTAl OP tB?K« sufnsr cofmi ®200J O'Day ConsuHon'c, "AS-BUILT RRKfTHMARK; H 'NT 'o^cf * <rwoff .T .-. s' CAsmar or CASimt gm ii» f iwM fi pa. AW APtmaun f :7 iwfj *(»/^« r IT W MlFtSECm Of HAfOiO >*vM /i Anw .4*0 M a«w xn" : ncv LTXftrt BEIIO* ir^% {NO COUHFr W»T i.iMim a*'A) iJ.I.V OAJUt NCW or 192^ , h-^ 1 - - i--!—- _~ pjr-U- "niCITY or CAfilSBABlpT? J It EwoiNcraiNS orPAW'wLNi II BORROW SUE SOUTHERN CALIFORNIA SOIL 3i. TESTING, INC. L» Co»t» Town C»ntw JOB NAME: La Costa Town Center JOB NUMBER: 0411014-4 IN-PLACE DENSITY TESTS TEST ELEVATION MOISTURE DRY DENSITY SOIL REL.COMP. NO. DATE LOCATION (feet.MSL) (percent) (p.c.f.) TYPE (percent) GRADING 1 1/16/04 See Plan 310.0 11.9 125.6 1C 95.9 2 1/16/04 See Plan 3120 10.7 130.2 IF 95.5 3 1/16/04 See Plan 314.0 12.2 127.4 ID 96.1 4 1/16/04 See Plan 316.0 9.8 124.9 IF 91.6 5 1/16/04 See Plan 318.0 11.7 128.4 IE 956 6 1/16/04 See Plan 320.0 11.3 130.0 2F 93,5 7 1/16/04 See Plan 322.0 11.1 129.2 2E 94,2 8 1/19/04 See Plan 324.0 13.2 128.8 2E 93,9 9 1/19/04 See Plan 326.0 118 126.7 2F 91.1 10 1/19/04 See Plan 328.0 12.7 127.2 2F 91 4 11 1/19/04 See Plan 330.0 14.1 125.8 IE 93.7 12 1/19/04 See Plan 332.0 14.6 130.6 IF 95.7 13 1/19/04 See Plan 334.0 14.0 131.4 2F 94.5 14 1/19/04 See Plan 336.0 13.8 127.7 2C 95.3 15 1/19/04 See Plan 338.0 15.1 128.3 2E 93.5 16 1/20/04 See Plan 340.0 10.7 126.8 IE 94.4 17 1/20/04 See Plan 340.0 11.4 130.4 IF 95.6 18 1/20/04 See Plan 342.0 11.7 125.9 ID 94.9 19 1/20/04 See Plan 342.0 10.9 128.6 IF 94.3 20 1/28/04 See Plan 358.0 9.7 123.1 2A 94.0 21 1/28/04 See Plan 361.0 10.4 125.2 2B 94.5 22 1/28/04 See Plan 369.0 11.5 124.3 2B 93.8 23 1/29/04 See Plan 344.0 10.7 126.9 IE 94.5 24 1/29/04 See Plan 344.0 114 128.4 IF 94.1 25 1/29/04 See Plan 346.0 9.2 130.2 IF 95.5 26 1/29/04 See Plan 346.0 8.7 125.6 ID 94.7 27 1/29/04 See Plan 348.0 11.6 127.7 IE 95.1 28 1/29/04 See Plan 348.0 128 127.4 IE 94.9 29 1/29/04 See Plan 350.0 15.2 1252 ID 94.4 30 1/29/04 See Plan 350.0 11.1 130.0 IF 95.3 31 1/29/04 See Plan 3520 10.6 126.8 IE 94.4 32 1/30/04 See Plan 352.0 9.7 125.4 1E 93.4 33 1/30/04 See Plan 354.0 8.4 130.6 IF 95.7 34 1/30/04 See Plan 354.0 10.8 129.9 IF 95.2 35 1/30/04 See Plan 356.0 11.2 127.4 1F 93.4 36 1/30/04 See Plan 356.0 10.4 126,6 IF 92.8 37 1/30/04 See Plan 358.0 9.6 131.2 1F 96.2 38 1/30/04 See Plan 358.0 10.1 126.3 IF 92.6 39 2/5/04 See Plan 351.0 10.7 129.6 IF 95.0 40 2/5/04 See Plan 353.0 11.5 130.1 IF 95.4 41 2/5/04 See Plan 356.0 9.4 125.9 1D 94.9 42 2/5/04 See Plan 360.0 9.7 126.7 IE 94.3 43 2/5/04 See Plan 360.0 10.1 125.4 1E 93.4 44 2/5/04 See Plan 362.0 8.7 128.2 IF 94.0 45 2/5/04 See Plan 362.0 9.4 127.3 IF 93.3 46 2/12/04 See Plan 364.0 18.9 100.7 7 97.0 47 2/12/04 See Plan 364 0 22.1 100.4 7 96.7 48 2/12/04 See Plan 366.0 20.4 100.2 7 96.5 49 2/12/04 See Plan 366.0 19.8 100.9 7 97.2 PLATE NO. 3 JOB NAME: La Costa Town Center JOB NUMBER: 0411014-4 IN-PLACE DENSITY TESTS TEST ELEVATION MOISTURE DRY DENSITY SOIL REL.COMP. NO. DATE LOCATION (feet.MSL) (percent) (P.c.f.) TYPE (percent) 50 2/13/04 See Plan 364.0 10.6 126.7 1E 94.3 51 2/13/04 See Plan 364.0 11.1 130.2 IF 95.5 52 2/13/04 See Plan 366 0 9.6 128.4 IE 95.6 53 2/13/04 See Plan 366.0 92 131.2 1F 96.2 54 2/17/04 See Plan 368.0 17.9 109.4 3 90.8 55 2/17/04 See Plan 370.0 18.1 110.1 3 91.4 56 2/17/04 See Plan 372 0 16.9 109.2 3 90.6 57 2/17/04 See Plan 374.0 20.4 106.9 4 90.6 58 2/17/04 See Plan 376.0 19.7 107.3 4 90.9 59 2/25/04 See Plan 378.0 15.9 107.9 4 91.4 60 2/25/04 See Plan 378.0 16.8 106.8 4 90,5 61 2/25/04 See Plan 380.0 14.6 107.8 4 91.4 62 2/25/04 See Plan 380.0 13.8 109.1 4 92.5 63 2/25/04 See Plan 372,0 18.4 89,7 7 86.4 64 2/25/04 See Plan 371.0 19.6 94.8 7 91.3 65 2/25/04 RETEST OF 63 372.0 169 93.9 7 90.5 66 2/25/04 See Plan 371.0 19.2 95.2 7 91.7 67 2/25/04 See Plan 374,0 18.7 99.6 7 96.0 68 2/25/04 See Plan 368,0 16.8 108.2 4 91.7 69 2/25/04 See Plan 371.0 14.4 109.8 4 93.1 70 3/1/04 See Plan 374.0 18.9 97.7 7 94.1 71 3/1/04 See Plan 374.0 19.4 101.1 7 97.4 72 3/1/04 See Plan 373.0 20.1 95,8 7 92.3 73 3/1/04 See Plan 376.0 17.8 97.9 7 94.3 74 3/1/04 See Plan 378.0 16.9 92.1 7 88.7 75 3/1/04 RETEST OF 74 378.0 19.4 94.6 7 91.1 76 3/1/04 See Plan 374.0 14.6 99.2 5 88.6 77 3/1/04 See Plan 374.0 15.9 104.6 5 93.4 78 3/1/04 RETEST OF 7S 374.0 17.7 102.9 5 91.9 79 3/1/04 See Plan 376.5 14.8 101 6 5 90.7 80 3/1/04 See Plan 376-0 16.7 1009 5 90.1 31 3/2/04 See Plan 378.5 17.4 101.5 5 90.6 82 3/2/04 See Plan 380.0 17.9 100.7 7 97,0 83 3/2/04 See Plan 376.0 20.6 102.4 5 91.4 84 3/2/04 See Plan 375.0 16.8 101.1 5 90.3 85 3/2/04 See Plan 378.0 19.4 99.4 5 88.8 86 3/2/04 RETEST OF 85 378.0 18.5 100.9 5 90.1 87 3/2/04 See Plan 377.0 20.2 101.6 5 90.7 88 3/2/04 See Plan 380.0 15.9 102.7 5 91.7 89 3/3/04 See Plan 380.0 19.6 103.6 5 92.5 90 3/3/04 See Plan 379.0 18.8 101.9 5 91.0 91 3/3/04 See Plan 379.0 20.4 102.7 5 91.7 92 3/3/04 See Plan 381.0 21.1 100.9 5 90.1 93 3/3/04 See Plan 381.0 169 104.2 5 93.0 94 3/3/04 See Plan 382.0 18.4 100.8 5 90.0 95 3/8/04 See Plan 372.0 18.6 102.9 5 91.9 96 3/12/04 See Plan 370.0 16.1 102.0 5 91.1 97 3/12/04 See Plan 3720 15.9 101.6 5 90.7 98 3/12/04 See Plan 374.0 17.2 104.7 5 93.5 99 3/12/04 See Plan 382.0 FG 15.6 103.1 5 92.1 100 3/12/04 See Plan 381.0 FG 14.7 1020 5 91,1 PLATE NO. 4 JOB NAME: La Costa Town Center JOB NUMBER: 0411014-4 IN-PLACE DENSITY TESTS TEST NO. DATE ELEVATION LOCATION (feet.MSL) MOISTURE (percent) DRY DENSITY (p.c.f.) SOIL TYPE RELCOMP. (percent) 101 3/12/04 See Plan 381.0 FG 13.9 102.6 5 91.6 102 3/15/04 See Plan 372,0 16.1 101.0 5 90.2 103 3/15/04 See Plan 363.0 14.9 108.1 4 91,6 104 3/15/04 See Plan 368 0 13.7 106.7 4 904 105 3/15/04 See Plan 354.0 16 1 106.9 4 90.6 106 3/15/04 See Plan 369.0 15.6 101.8 5 909 107 3/15/04 See Plan 355.0 13.8 101.3 5 90.4 108 3/15/04 See Plan 371.0 17.2 107.3 4 90.9 109 3/15/04 See Plan 348.0 15.1 106.5 4 90.3 110 3/15/04 See Plan 365.0 19.6 108.3 4 91.8 111 3/15/04 See Plan 372.0 13.1 103.6 5 92.5 112 3/15/04 See Plan 363.0 12.9 102.1 5 91.2 113 3/15/04 See Plan 373.0 15.2 100.9 5 90.1 114 3/15/04 See Plan 356.0 16.7 101.3 5 90.4 115 3/17/04 See Plan 380.0 FG 10.7 102.9 5 91,9 116 3/17/04 See Plan 380.0 FG 11.9 101.6 5 90.7 117 3/17/04 See Plan 380.0 FG 14 1 104.2 5 93.0 118 3/17/04 See Plan 380.0 FG 12.7 100.9 5 90.1 119 3/17/04 See Plan 379.0 FG 12.6 101.4 5 90.5 120 3/17/04 See Plan 378.0 FG 13.1 102.9 5 91.9 121 3/17/04 See Plan 378.0 FG 11.7 103.7 5 92.6 122 3/18/04 See Plan 379.0 FG 12.7 101.4 5 90.5 123 3/18/04 See Plan 379.0 FG 11.1 102.7 5 91 7 124 3/18/04 See Plan 377.0 FG 10.9 103.2 5 92.1 125 3/18/04 See Plan 377.0 FG 13.7 101.5 5 90.6 126 3/18/04 See Plan 377.0 FG 9.9 101.7 5 90.8 127 3/29/04 See Plan 381.0 FG 12.7 104.1 5 92.9 128 3/29/04 See Plan 383.0 FG 10.8 102.7 5 91.7 129 3/29/04 See Plan 383.0 FG 9.8 101.9 5 91,0 130 3/29/04 See Plan 376.0 FG 13.1 103.9 5 92,8 131 3/29/04 See Plan 368.0 FG 12.7 101.6 5 90.7 132 3/29/04 See Plan 374.0 FG 11.4 100.9 5 90.1 133 3/29/04 See Plan 374.0 FG 12.1 106.1 5 94.7 FG = Finish Grade STORM DRAIN SD1 1/26/04 Storm Drain "A" 332.0 10.7 126.7 ID 95.6 SD2 1/26/04 Storm Drain "A" 336.0 11.3 124.9 ID 94.2 SD3 1/26/04 Storm Drain "A" 339.0 9.8 125.4 1E 93.4 SD4 2/2/04 Storm Drain "A" 349.0 9.6 128.7 IF 94.4 SD5 2/2/04 Storm Drain "A" 352.0 8.7 130.1 IF 95.4 SD6 2/2/04 Storm Drain "A" 355.0 9.9 126.4 IE 94.1 SD7 2/2/04 Storm Drain "A" 358.0 10.4 128.8 IF 94,4 SD8 2/9/04 Storm Drain "A" 329.5 9.7 127.5 IF 93.5 SD9 2/9/04 Storm Drain "A" 332.0 10.4 130.8 IF 95.9 SD10 2/9/04 Storm Drain "A" 335.0 8.8 126,1 IF 92,4 8011 2/25/04 Storm Drain "C" 315.5 15.2 102.1 5 91.2 SD12 2/25/04 Storm Drain "C" 317.5 14.3 104.8 5 93.6 SD13 2/25/04 Storm Drain "C" 319.5 14.1 103.4 5 92.3 SD14 2/25/04 Storm Drain "C" 321.5 13.6 103.8 5 92.7 PLATE NO. 5 JOB NAME: La Costa Town Center JOB NUMBER: 0411014-4 1 IN-PLACE DENSITY TESTS TEST ELEVATION MOISTURE DRY DENSITY SOIL REL.COMP. NO. DATE LOCATION (feet,MSL) (percent) (pcf.) TYPE (percent) SD15 2/25/04 Storm Drain "C" 323.5 15.2 102.9 5 91.9 SD16 3/12/04 Storm Drain "B" 296.0 12.7 108.4 4 91.9 SD17 3/12/04 Storm Drain "B" 298.0 9,4 106.7 4 90.4 SD18 3/12/04 Storm Drain "B" 300.0 10.6 110.3 4 93,5 SD19 3/12/04 Storm Drain "B" 302.0 11.9 107.9 4 91.4 SD20 3/18/04 Storm Drain "B" 301.0 13.1 109.0 4 92.4 SD21 3/18/04 Storm Drain "B" 303.0 11,0 108.4 4 91.9 SD22 3/19/04 Abandoned Storm Drain 380.0 8.0 121.7 2 94.0 SD23 3/19/04 Abandoned Storm Drain 377.0 7,9 122.4 2 94.5 1 MAXIMUM DENSITY AND OPTIMUM MOISTURE SUMMARY (ASTM D1557r Soil Maximum Optimum Type Soil Description Oensitv. Dcf Moisture. % 1 Reddish Brown Silty Sand 126.2 8.9 1A Reddish Brown Silty Sand with 5% Rock 127.7 8.5 IB Reddish Brown Silty Sand with 10% Rock 129.3 8.1 10 Reddish Brown Silty Sand with 15% Rock 131.0 7.8 1D Reddish Brown Silty Sand with 20% Rock 132.6 7.4 IE Reddish Brown Silty Sand with 25% Rock 134.3 7.0 IF Reddish Brown Silty Sand with 30% Rock 136.4 6.6 2 Brown Silty Sand with rock 129.5 8.1 2A Brown Silty Sand with rock with 5% Rock 131.0 7.8 2B Brown Silty Sand with rock with 10% Rock 132.5 7.4 20 Brown Silty Sand with rock with 15% Rock 134.0 7.1 2D Brown Silty Sand with rock with 20% Rock 135.6 6.7 2E Brown Silty Sand with rock with 25% Rock 137.2 64 2F Brown Silty Sand with rock with 30% Rock 139.1 6.0 3 Light Brown Silty Sand 120.5 7.3 4 Light Tan to White Silty Sand 118.0 12.0 5 Tan to Brown Silty Sand/Sandy Silt with Clay 112.0 11.0 6 Brown Silty Sand with Clay 121.8 9.5 7 Tan Clayey to Sandy Silt 103.8 19.0 j. . . , • • -1 EXPANSION SAMPLE EXPANSION EXPANSION TEST SAMPLE LOCATION INDEX POTENTIAL El South Building 91 high E2 East Building 54 medium E3 South Building 84 medium E4 East Building 63 medium PLATE NO. 6 r 18" min. Compacted Fill . 3/4" . ,.: crushed \ rock, ., 2/3 wall height (§r^\ ' Typical Retaining Wall Subdrain Detail Not to Scale 21 Miradrain 6000 or equivalent. 2/3 wall height HE © Floor Slab (?) Filter Fabric between rock and soil d) Backcut (4) Waterproof back of wall following architect's specifications @ 4* minimum perforated pipe, SDR35 or equivalent, holes down, 1 % fall to outlet, top of pipe below top of slab, encased in 3/4* crushed rock. Provide 3 cubic feet per linear foot crushed rock minimum. Crushed rock to be surrounded by filter fabric (Mirafi 140N or equivalent), with 6" minimum overlap. Provide solid outlet pipe at suitable location. SOUTHERN CALIFORNIA LA COSTA TOWN CENTER SOIL & TESTING, INC. BY: Mf DATE: 04-20-04 SOIL & TESTING, INC. JOB NUI^BER: 0411014-4 PLATE NO.: 7 August 12,2013 Project No. 12043-01 Ms. April Tomillo Taylor Morrison 8105 Irvine Center Drive, Suite 1450 Irvine, California 92618 Subject: Clarification of Geotechnical Parameters for Retaining Wall Design Adjacent to Bio- Retention Basins Proposed La Costa Town Center Residential Development, Carlsbad, California Introduction In accordance with your request, LGC Geotechnical, Inc. has prepared this letter to clarify our geotechnical parameters for retaining wall design for the walls adjacent to the proposed bio retention basins. Geotechnical Parameters forRetainim WallDesien For design purposes, the following lateral earth pressure values for level or sloping backfill are recommended for retaining walls backfilled with onsite soils of Low expansion potential. For the bio retention basins only, we recommend the design engineer ignore all of the passive pressure attributed to the planting media material. Full passive pressures may be used for the gravel below this planter mix. Table 6 Static Equivalent Fluid Weight (pcf) Conditions Level 2:1 Slope Active 40 65 At-Rest 55 90 Passive *200 (Maximum of 3 ksf) 140 (Sloping Dovra) Ignore the upper 18" (all planting media) 0^ n o z o z o Unrestrained (yielding) cantilever walls up to 15 feet in height should be designed for an active equivalent pressure value provided in table above. If conditions other than those covered herein are anticipated, the ^| 120 Calle Iglesia, Suite A, San Clemente, CA 92672 (949) 369-6141 C www.lgcgeotechnical.com equivalent fluid pressure values should be provided on an individual case basis by the geotechnical engineer. A surcharge load for a restrained or unrestrained wall resulting from automobile traffic may be assumed to be equivalent to a uniform horizontal pressure of 75 psf which is in addition to the equivalent fluid pressure given above. For other uniform surcharge loads, a uniform horizontal pressure equal to 0.35q should be applied to the wail (where q is the surcharge pressure in psf). To account for potential redistribution of forces during a seismic event, basement walls, if any, that fall within the requirements of ASCE 7-05 Section 15.6.1 should also be checked considering an additional uniform seismic pressure distribution equal to lOH psf, where H equals the overall retained height in feet. The wall pressures assume walls are backfilled with free draining materials and water is not allowed to accumulate behind walls. A typical wall drainage design is provided in Appendix D. Importing or selective grading may be necessary to obtain retaining wall backfill material. Wall backfill should be brought to at least 3 percent above the optimum moisture content and compacted by mechanical methods to at least 90 percent relative compaction (based on ASTM D1557). Wall footings should be designed in accordance with the foundation design recommendations and reinforced in accordance with structural considerations. The allowable bearing pressure for retaining walls should be limited to 2,500 psf for footing founded in compacted fill on the gravel storage blanket below the basins. Footing embedment depth should be at least 18 inches below the lowest adjacent grade. Lateral soil resistance developed against lateral structural movement can be obtained from the passive pressure value provided above. Further, for sliding resistance, the friction coefficient of 0.33 may be used at the concrete and soil interface. These values may be increased by one-third when considering loads of short duration including wind or seismic loads. The total resistance may be taken as the sum of the frictional and passive resistance provided that the passive portion does not exceed two-thirds of the total resistance. Should you have any questions, please do not hesitate to contact our office. We appreciate this opportunity to be of service. Sincerely, LGC Geotechnical, Inc. Tim Lawson, CEG 1821, GE 2626 Geotechnical Engineer/Geologist TJL/kmh Distribution: (I) Addressee (via email) (1) Latitude 33 Planning and Engineering (via email) Attn: Mr. Armando Urquidez (1) Oreo Block, Inc. Attn. Mr. Tim Mallis (via email) Project No. 12043-01 Page 2 August 12. 2013 TABLE OF CONTENTS (Continued) SECTION p^Qg ATTACHMENTS PLATES Plate 1A As-Built Geotechnical Map Plate 1B Proposed Development Plate 2 Field Density Test Locations - Storm Drain Plates 3-6 Field Density and Laboratpry Test Results Plate 7 Retaining Wall Subdrain Detail PHONE (619) 280-4321 I O L I. FREE (877) 215-4321 F A X (619) 280-4717 P.O. Box 600627 San Diego, CA 92160-0627 6280 Riverdale Street San Diego, CA 92120 www.scst.com April 20, 2004 Mr. Jeff Jenco Lusardi Construction 1570 Linda Vista Drive San Marcos, California 92069 SCS&T No. 0411014 Report No. 4 Subject: AS-GRADED GEOTECHNICAL REPORT LA COSTA TOWN CENTER RANCHO SANTA FE ROAD AND LA COSTA AVENUE CARLSBAD, CALIFORNIA References: 1) 2) 3) "Existing Storm Drain, La Costa Town Center, Rancho Santa Fe and La Costa Avenue, Carlsbad, Califomigf ; prepared by Southern California Soil and Testinq Inc.; dated March 12, 2004 (SCS&T 0411014-3). "Fill Slope Construction, La Costa Town Center, Rancho Santa FeandLa Costa Avenue, Carlsbad, California'; prepared by Southern California Soil and Testinq Inc.; dated January 20, 2004 (SCS&T 0411014-2). "Preliminary Geotechnical Study Update, Parcels S.E. 13 and25 Acres Easterly of La Costa Avenue and Mission Estanciel'; prepared by GeoSoils, Inc • dated June 6, 1990. Dear Mr. Jenco: In accordance with your request, this report has been prepared to present the results of field obsen/ations and testing performed in conjunction with mass grading operations at the subject site. Our services were performed between January 16 and March 19,2004. The grading was performed by Erreca's of El Cajon, California. To assist in determining the locations and elevations of our field density tests, we were provided with a set of plans prepared by O'Day Consultants, dated December 18, 2003, which define the general extent of site grading. 1. SUMMARY OF OBSERVATION AND TESTING 1.1. PROJECT DESCRIPTION The project site is located about 1,000 feet to the northeast of the intersection of Rancho Santa Fe Road and La Costa Avenue in Carlsbad, California. The site is bordered by the existing Rancho April 20, 2004 Lusardi Construction g^jg^ T No. 0411014-4 La Costa Town Center pggg 2 Santa Fe Road to the northwest, the new alignment of Rancho Santa Fe Road (currently under construction) to the south, and the recently completed Paseo Lupino to the east. The recent grading operations that are the subject of this report produced a street-graded configuration with drainage directed toward a catch basin near the west corner of the site. The western portion of the site is bordered by newly-constructed fill slopes up to about 40 feet in height that descend to the existing and new Rancho Santa Fe Road alignments. The eastem portion of the site is bordered by cut and fill-over-cut slopes ranging up to about 25 feet in height, descending to the new Rancho Santa Fe Road and Paseo Lupino. All slopes were constructed at a 2-1 (horizontal:vertical) ratio. Additional grading will be performed at a later date to achieve final proposed grades. The site will ultimately be developed with a retail center, including two retail structures and an asphalt parking lot. The sheet graded configuration of the site established by the recent mass grading is depicted on Plate No. 1 A. The currently proposed site development scheme is depicted on Plate No. 1B. 1.2. SITE PREPARATION 1.2.1. Grading Equipment The primary equipment employed for the subject grading operations included: 2 - Caterpillar D10 Bulldozer 1 - Water truck 1 - Caterpillar 992 Loader 1 - Excavator 1 - Caterpillar D9 Bulldozer 3 - Caterpillar 773 Rock Trucks 1 - Caterpillar D8 Bulldozer 1.2.2. Clearing and Grubbing Site preparation began with the removal of existing vegetation and organic matter from the area to be graded. The detrimental material generated from this operation was exported from the site. 1.2.3. Site Grading Existing fill topsoil and alluvial deposits were removed from the areas to receive proposed settlement-sensitive improvements. The bottoms of the removal areas generally exposed metavolcanic rock. Pre-existing fill soils associated with the existing and new alignments of Rancho Santa Fe Road were left in place at the western end of the site. Temporary slopes were cut into the fill soils at a 1:1 ratio as removals were made. The fill exposed in the 1:1 slope was benched as fill operations progressed. Removal depths ranged up to a maximum of about 25 feet below existing grades. % April 20, 2004 Lusardi Construction SCS&T No. 0411014-4 ,ln to about 56 feel of fill was placed to actiieve proposed stieet.graded elevations in the w stn pol e Site, v^iie cuts of up to a.»u. 2S fee. (including „ve,.excava.,on) were Tq , d in the eastern portion of tfte site. Tt,e proposed building pads were overexcavated to rium d P hs of approximately 5 feet below proposed finish floor elevations. Paring areas Trroverll^ted'o a minimum 0. approximately ,0 fee, belo» final par.^ elevations. Blasting was required to achieve the required cuts in the eastem portion of the site. Much of the ma ll produced by blasting consisted of rock fragments up to 2 leet in diameter w, adequate To llx materia, for placemen, as compacted fili. These rock/soi, fills were typically mo,s u e 0 dTned and placed in me deep ,111 areas o, the s«e (a, least 10 fee. below proposed rade) n ft of abol f 5 to 2.0 ,eet in thlcKness. Compaction was achieved pnmaril, »th rock trucks, in lilts of aooui 1 .= to ^ suflident fines to fill voids between Soil matrix material was added in some cases to pioviuo nanerallv rock Iraaments Blasted material possessing only limited soil matrix material was generally mol ind stockpiled in the designated stockpile area ,o ,he east o, the new Rancho San a Pe Illgnment'occasional boulders iarger than 2 ^''f-J^^;!^^^-":::^^ '^^ compacted tills, Individually or in winrows, under observation of SCS&T s soils lechnician. nil Placed within the upper 5 feet ol me building pads and the upper ,0 leet o, the paiKing lot a la cfn^td of JL capping material. This ma,erial was comprised primanly ol si«y Td sindy », with variable clay and rock fragments generally no, exceeding 6 inches n sand/sanoy w i ' taukjers larger ,han 6 inches may be presen,. Similar re^^o^irerrr*^^^^^^^ Thel^rmlrlal was obtained f^m on-site topsoil and alluvial deposits, as well as a borrow Site to the east of Rancho Santa Fe Road. Excavation bottoms were generally not scarified due to the rocky nature of the exposed material. ™ enerated from the removal operations, on-site cuts, and import fill from e borrow 1 we e Placed in the removed areas as uniformly compacted fill material. Typically fill soils were p Iced^^^^^^ conditioned lifts and compacted until field density tests indicated a rilu^QO percent relative compaction. Compaction was achieved primarily by means of a o:Z:: ZlL^ rock trucks and other heavy construction equipment. This process continued until designed elevations were reached. 12 4 Keyways TO p ovide support for the proposed fill and fill-over-cut slopes, keyways were cut into dense me.rran^ r«k along ,he proposed ,oes Che slopes. Thekeyways were generally at least TsTe^wide and sloped back into the existing sloping terrain atan approximate gradientof two percent. RESPONSE TO CITY REVIEW COMMENTS LA COSTA TOWN SQUARE CARLSBAD, CALIFORNIA Prepared For: TAYLOR MORRISON OF CA, LLC 8105 Irvine Center Drive, Suite 1450 Irvine, California 92618 Project No. 042631-001 February 1, 2013 4 Leighton and Associates, Inc. A LEIGHTON GROUP COMPANY Leighton and Associates, Inc. A LEIGHTON GROUP COMPANY February 1, 2013 Project No. 042631-001 Taylor Morrison of CA, LLC 8105 Irvine Center Drive, Suite 1450 Irvine, California 92618 Attention: Ms. April Tornillo Subject: Geotechnical Response to Review Comments Proposed La Costa Town Center Residential Development Carlsbad, California References: Latitude 33, 2013, Tentative Map, La Costa Town Center, Sheets 1 through 8, received January 24, 2013 Leighton and Associates, Inc. 2012, Geotechnical Investigation, Proposed La Costa Town Center Residential Development, Carlsbad, California, Project No. 042631-001, dated March 3, 2012 City of Carlsbad, 2013, Cycle Review Comments, CT 12-05/PUD 12-07 Development Services, dated January 14, 2013 This letter presents our responses to the comments raised as part of the City of Carlsbad's Cycle Reviews (referenced above). Please note that only responses pertinent to geologic comments are included in this letter. Our comments are presented below; 3934 Murphy Canyon Road, Suite B205 « San Diego, CA 92123-4425 858.292,8030 « Fax 858.292.0771 » wwwJeightongeo.com 042631-001 Engineering Cycle Review Comments Comment No. 6 The recent soils report update did not include design recommendations for the proposed bioretention basins. Please provide an update letter addressing the suitability of the proposed bioretention basins at the proposed locations as shown on the site plan. The update letter should include bioretention design recommendations, including set- back requirement from top of slopes. Response During the design of the civil plans, we have been coordinating with Latitude 33 concerning the design of bioretention basins. To mitigate against potential slope instability and negative impacts from lateral migration of storm water within fill material and Metavolcanic rock, we recommended a 20 mil HDPE liner for all bioretention basins at the site. In addition the liner will be underlain with a 2 inch sand layer at the base of the liner to avoid puncturing liner on Metavolcanic rocic present at bioretention basin excavation. We also recommended the basins adjacent to descending slopes have the same minimum setback as site retaining walls, a horizontal distance from the outside base of the footing or bottom of basin excavation 10 feet to daylight of as stated in section 5.6 of the reference geotechnical report. It should be noted that we have reviewed the referenced site plans and details regarding the site bioretention basins for La Costa Town Square and found that they are in conformance with the referenced geotechnical report and recommendations and they are suitable for the planned site development. We have attached a copy of the referenced geotechnical report at the rear of the text. The conclusions and recommendations in this letter are based in part upon data that were obtained from a limited number of observations, site visits, excavations, samples, and tests. Such information is by necessity incomplete. The nature of many sites is such that differing geotechnical or geological conditions can occur within small distances and under varying climatic conditions. Changes in subsurface conditions can and do occur over time. Therefore, the findings, conclusions, and recommendations presented in this report can be relied upon only if Leighton and Associates has the opportunity to observe the subsurface conditions during grading and construction of the project, in order to 4 Leighton 042631-001 confirm that our preliminary findings are representative for the site. If you have any questions regarding our report, please contact this office. We appreciate this opportunity to be of service to you. Respectfully submitted LEIGHTON AND ASSOCIATES. INC. Mike D. Jensen, CEG 2457 Project Geologist ^ y A , jf ''I j ' •1 i William D. Olson, RCE 45283 Associate Engineer Attachments; Geotechnical Investigation Distribution: (2) Addressee (3) Latitude 33. Attention: Mr. Annando Urquidez -3- Leighton i g I H II I I H V I « « R n 18 APPENDIX B LABORATORY TESTING AND FIELD DENSITY TESTS^ilTHERS ^f^^J^^ 042631-001 6.0 LIMITATIONS VS I The conclusions and recommendations presented in this report are based in part upon data that were obtained from a limit^jiijuiibarjDli^ site visits, excavations, samples, and tests^-^agh'TnfoTrnation is^ nature of many sites is such that differing geotechnicarwg&ological corfdittims^caQ^^occur within small distances and under varying climatic conditions. Changes in subsurace conditions can and do occur over time. Therefore, the findings, conclusions, arfd recommendations presented in this report can be relied upon only if Leightprfhas the opportunity *' observe the subsurface conditions during grading and„GOnstruction of the project, order to confirm that our preliminary findings are re^^ntative for the site. . L&c -31- Leighton 1 NO. 2626 EXR 06/30/13 042631-001 ^^JecHJ^^ef the tree) in order to prevent penetration of the tree roots beneath the foundation ^*i=2f^ c^^i^s^ of the structure or improvement. Locating planters adjacent to buildings or structures should be avoided as much as possible. If planters are utilized in these locations, they should be properly designed so as to prevent fluctuations in the moisture content of the subgrade soils. Planting areas at grade should be provided with appropriate positive drainage. Wherever possible, exposed soil areas should be above paved grades. Planters should not be depressed below adjacent paved grades unless provisions for drainage, such as catch basins and drains, are made. Adequate drainage gradients, devices, and curbing should be provided to prevent runoff from adjacent pavement or walks into planting areas. Watering should be done in a uniform, systematic manner as equally as possible on all sides of the foundation, to keep the soil moist. Irrigation methods should promote uniformity of moisture in planters and beneath adjacent concrete flatwork. Ovenwatering and undenwatering of landscape areas must be avoided. Areas of soil that do not have ground cover may require more moisture, as they are more susceptible to evaporation. Ponding or trapping of water In localized areas adjacent to the foundations can cause differential moisture levels in subsurface soils and, therefore, should not be allowed. Trees located within a distance of 20 feet of foundations would require more water in periods of extreme drought, and in some cases, a root injection system may be required to maintain moisture i equilibrium. During extreme hot and dry periods, close obsen/ations should be carried out around foundations to ensure that adequate watering is being undertaken to prevent soil from separating or pulling back from the foundation. 5.12 Future Investigation The findings of this report indicate that the proposed grading is geotechnically feasible. Prior to construction, addi«griaL-gfiot©Ghi«6aMiwestigat^ will be required to further evaluate metavoTcanic rock and fill areas to provide additional subsurface information regarding/oversized rock and excavation characteristics of metavolcanic rock. In addition, laboratory testing to assess soil corrosivity will need to be performed during k future site investigation. This information may then be utilized to provide additional co^structi^ level recommendations. Leighton PHONE (619) 280-4321 TOLL FREE (877) 215-4321 f A .X (619) 280-4717 P.O. Box 500627 San Diego, CA 92160-0627 6280 Riverdale Street San Diego, CA 92120 www.scst.com AS-GRADED GEOTECHNICAL REPORT LA COSTA TOWN CENTER RANCHO SANTA FE ROAD AND LA COSTA AVENUE CARLSBAD, CALIFORNIA PREPARED FOR: MR. JEFF JENCO LUSARDI CONSTRUCTION 1570 LINDA VISTA DRIVE SAN MARCOS, CALIFORNIA 92069 PREPARED BY: SOUTHERN CALIFORNIA SOIL & TESTING, INC. 6280 RIVERDALE STREET SAN DIEGO, CALIFORNIA 92120 Providing Professional Engineering Services Since 1959 TABLE OF CONTENTS SECTION PAGE 1. SUMMARY OF OBSERVATION AND TESTING I 1.1. PROJECT DESCRimON 1 1.2. SITE PREPARATION 2 1.2.1. Grading Equipment 2 7.2.2. Clearing and Grubbing 2 7.2. J. Site Grading 2 1.2.4. Keyways 7.2.5. Fill Slopes 4 1.2.6. Cut Slopes 4 1.2.7. Storm Drain Trench Baclcfill 4 1.2.8. Subdrain 4 1.2. FIELD OBSERVATION AND TESTING 5 1.4. LA BOR ATOR Y TESTS 5 1.5. AS-BUILT GEOLOGY 6 1.6. REMAINING WORK '• 6 2. CONCLUSIONS 6 3. RECOMMENDATIONS 7 3.1. FOUNDATIONS 7 5.7.7. General 7 3.1.2. Reinforcement 7 3.1.3. Seismic Design Factors 7 3.1.4. Foundation Excavation Observation 8 3.1.5. Settlement Characteristics 8 3.1.6. Expansion Characteristics 8 3.1.7. Foundation Plan Review 8 3.1.8. Soluble Sulfates 8 3.2. SLABS-ON-GRADE 8 3.2.1. Interior Concrete Slabs-on-Grade 8 3.2.2. Exterior Concrete Slabs-on-Grade 9 3.3. EARTH RETAINING WALLS 10 3.3.1. Foundations 70 3.3.2. Passive Pressure 70 3.3.3. Active Pressure /0 3.3.4. Retaining Wall Subdrains and Waterproofing 10 3.3.5. Backfill 10 3.3.6. Factor of Safety 77 4. LIMITATIONS 11 LEIGHTON AND ASSOCIATES, INC. General Earthwork and Grading Specifications LO General Ll Intent These General Earthwork and Grading Specifications are for the grading and earthwork shown on the approved grading plan(s) and/or indicated in the geotechnical report(s). These Specifications are a part of the recommendations contained in the geotechnical report(s). In case of conflict, the specific recommendations in the geotechnical report shall supersede these more general Specifications. Observations of the earthwork by the project Geotechnical Consultant during the course of grading may result in new or revised recommendations that could supersede these specifications or the recommendations in the geotechnical report(s). 1.2 The Geotechnical Consultant of Record Prior to commencement of work, the owner shall employ the Geotechnical Consultant of Record (Geotechnical Consultant). The Geotechnical Consultants shall be responsible for reviewing the approved geotechnical report(s) and accepting the adequacy of the preliminary geotechnical findings, conclusions, and recommendations prior to the commencement of the grading. Prior to commencement of grading, the Geotechnical Consultant shall review the "work plan" prepared by the Earthwork Contractor (Contractor) and schedule sufficient personnel to perform the appropriate level of observation, mapping, and compaction testing. During the grading and earthwork operations, the Geotechnical Consultant shall observe, map, and document the subsurface exposures to verify the geotechnical design assumptions. If the observed conditions are found to be significantly different than the interpreted assumptions during the design phase, the Geotechnical Consultant shall inform the owner, recommend appropriate changes in design to accommodate the observed conditions, and notify the review agency where required. Subsurface areas to be geotechnically observed, mapped, elevations recorded, and/or tested include natural ground after it has been cleared for receiving fill but before fill is placed, bottoms of all "remedial removal" areas, all key bottoms, and benches made on sloping ground to receive fill. The Geotechnical Consultant shall observe the moisture-conditioning and processing of the subgrade and fill materials and perform relative compaction testing of fill to determine the attained level of compaction. The Geotechnical Consultant shall provide the test results to the owner and the Contractor on a routine and frequent basis. LEIGHTON AND ASSOCIATES, INC. General Earthwork and Grading Specifications 1.3 The Earthwork Contractor The Earthwork Contractor (Contractor) shall be qualified, experienced, and knowledgeable in earthwork logistics, preparation and processing of ground to receive fill, moisture-conditioning and processing of fill, and compacting fill. The Contractor shall review and accept the plans, geotechnical report(s), and these Specifications prior to commencement of grading. The Contractor shall be solely responsible for performing the grading in accordance with the plans and specifications. The Contractor shall prepare and submit to the owner and the Geotechnical Consultant a work plan that indicates the sequence of earthwork grading, the number of "spreads" of work and the estimated quantities of daily earthwork contemplated for the site prior to commencement of grading. The Contractor shall inform the owner and the Geotechnical Consultant of changes in work schedules and updates to the work plan at least 24 hours in advance of such changes so that appropriate observations and tests can be planned and accomplished. The Contractor shall not assume that the Geotechnical Consultant is aware of all grading operations. The Contractor shall have the sole responsibility to provide adequate equipment and methods to accomplish the earthwork in accordance with the applicable grading codes and agency ordinances, these Specifications, and the recommendations in the approved geotechnical report(s) and grading plan(s). If, in the opinion of the Geotechnical Consultant, unsatisfactory conditions, such as unsuitable soil, improper moisture condition, inadequate compaction, insufficient buttress key size, adverse weather, etc., are resulting in a quality of work less than required in these specifications, the Geotechnical Consultant shall reject the work and may recommend to the owner that construction be stopped until the conditions are rectified. 2.0 Preparation of Areas to be Filled 2.1 Clearing and Grubbing Vegetation, such as brush, grass, roots, and other deleterious material shall be sufficiently removed and properly disposed of in a method acceptable to the owner, governing agencies, and the Geotechnical Consultant. The Geotechnical Consultant shall evaluate the extent of these removals depending on specific site conditions. Earth fill material shall not contain more than 1 percent of organic materials (by volume). No fill lift shall contain more than 5 percent of organic matter. Nesting of the organic materials shall not be allowed. LEIGHTON AND ASSOCIATES, ESfC. General Earthwork and Grading Specifications If potentially hazardous materials are encountered, the Contractor shall stop work in the affected area, and a hazardous material specialist shall be informed immediately for proper evaluation and handling of these materials prior to continuing to work in that area. As presently defined by the State of California, most refined petroleum products (gasoline, diesel fuel, motor oil, grease, coolant, etc.) have chemical constituents that are considered to be hazardous waste. As such, the indiscriminate dumping or spillage of these fluids onto the ground may constitute a misdemeanor, punishable by fines and/or imprisonment, and shall not be allowed. 2.2 Processing Existing ground that has been declared satisfactory for support of fill by the Geotechnical Consultant shall be scarified to a minimum depth of 6 inches. Existing ground that is not satisfactory shall be overexcavated as specified in the following section. Scarification shall continue until soils are broken down and free of large clay lumps or clods and the working surface is reasonably uniform, flat, and free of uneven features that would inhibit uniform compaction. 2.3 Overexcavation In addition to removals and overexcavations recommended in the approved geotechnical report(s) and the grading plan, soft, loose, dry, saturated, spongy, organic-rich, highly fractured or otherwise unsuitable ground shall be overexcavated to competent ground as evaluated by the Geotechnical Consultant during grading. 2.4 Benching Where fills are to be placed on ground with slopes steeper than 5:1 (horizontal to vertical units), the ground shall be stepped or benched. Please see the Standard Details for a graphic illustration. The lowest bench or key shall be a minimum of 15 feet wide and at least 2 feet deep, into competent material as evaluated by the Geotechnical Consultant. Other benches shall be excavated a minimum height of 4 feet into competent material or as otherwise recommended by the Geotechnical Consultant. Fill placed on ground sloping flatter than 5:1 shall also be benched or otherwise overexcavated to provide a flat subgrade for the fill. 2.5 Evaluation/Acceptance of Fill Areas All areas to receive fill, including removal and processed areas, key bottoms, and benches, shall be observed, mapped, elevations recorded, and/or tested prior to being accepted by the Geotechnical Consultant as suitable to receive fill. The Contractor shall obtain a written acceptance from the Geotechnical Consultant -3- LEIGHTON AND ASSOCIATES, INC. General Earthwork and Grading Specifications prior to fill placement. A licensed surveyor shall provide the survey control for determining elevations of processed areas, keys, and benches. 3.0 Fill Material 3.1 General Material to be used as fill shall be essentially free of organic matter and other deleterious substances evaluated and accepted by the Geotechnical Consultant prior to placement. Soils of poor quality, such as those with unacceptable gradation, high expansion potential, or low strength shall be placed in areas acceptable to the Geotechnical Consultant or mixed with other soils to achieve satisfactory fill material. 3.2 Oversize Oversize material defined as rock, or other irreducible material with a maximum dimension greater than 8 inches, shall not be buried or placed in fill unless location, materials, and placement methods are specifically accepted by the Geotechnical Consultant. Placement operations shall be such that nesting of oversized material does not occur and such that oversize material is completely surrounded by compacted or densified fill. Oversize material shall not be placed within 10 vertical feet of finish grade or within 2 feet of future utilities or underground construction. 3.3 Import If importing of fill material is required for grading, proposed import material shall meet the requirements of Section 3.1. The potential import source shall be given to the Geotechnical Consultant at least 48 hours (2 working days) before importing begins so that its suitability can be determined and appropriate tests performed. 4.0 Fill Placement and Compaction 4.1 Fill Layers Approved fill material shall be placed in areas prepared to receive fill (per Section 3.0) in near-horizontal layers not exceeding 8 inches in loose thickness. The Geotechnical Consultant may accept thicker layers if testing indicates the grading procedures can adequately compact the thicker layers. Each layer shall be spread evenly and mixed thoroughly to attain relative uniformity of material and moisture throughout. LEIGHTON AND ASSOCIATES, INC. General Earthwork and Grading Specifications 4.2 Fill Moisture Conditioning Fill soils shall be watered, dried back, blended, and/or mixed, as necessary to attain a relatively uniform moisture content at or slightly over optimum. Maximum density and optimum soil moisture content tests shall be performed in accordance with the American Society of Testing and Materials (ASTM Test Method D1557). 4.3 Compaction of Fill After each layer has been moisture-conditioned, mixed, and evenly spread, it shall be uniformly compacted to not less than 90 percent of maximum dry density (ASTM Test Method D1557). Compaction equipment shall be adequately sized and be either specifically designed for soil compaction or of proven reliability to efficiently achieve the specified level of compaction with uniformity. 4.4 Compaction of Fill Slopes In addition to normal compaction procedures specified above, compaction of slopes shall be accomplished by backroUing of slopes with sheepsfoot rollers at increments of 3 to 4 feet in fill elevation, or by other methods producing satisfactory results acceptable to the Geotechnical Consultant. Upon completion of grading, relative compaction of the fill, out to the slope face, shall be at least 90 percent of maximum density per ASTM Test Method D1557. 4.5 Compaction Testing Field-tests for moisture content and relative compaction of the fill soils shall be performed by the Geotechnical Consultant. Location and frequency of tests shall be at the Consultant's discretion based on field conditions encountered. Compaction test locations will not necessarily be selected on a random basis. Test locations shall be selected to verify adequacy of compaction levels in areas that are judged to be prone to inadequate compaction (such as close to slope faces and at the fill/bedrock benches). 4.6 Frequencv of Compaction Testing Tests shall be taken at intervals not exceeding 2 feet in vertical rise and/or 1,000 cubic yards of compacted fill soils embankment. In addition, as a guideline, at least one test shall be taken on slope faces for each 5,000 square feet of slope face and/or each 10 feet of vertical height of slope. The Contractor shall assure that fill construction is such that the testing schedule can be accomplished by the Geotechnical Consultant. The Contractor shall stop or slow down the earthwork construction if these minimum standards are not met. -5- LEIGHTON AND ASSOCIATES, INC. General Earthwork and Grading Specifications 4.7 Compaction Test Locations The Geotechnical Consultant shall document the approximate elevation and horizontal coordinates of each test location. The Contractor shall coordinate with the project surveyor to assure that sufficient grade stakes are established so that the Geotechnical Consultant can determine the test locations with sufficient accuracy. At a minimum, two grade stakes within a horizontal distance of 100 feet and vertically less than 5 feet apart from potential test locations shall be provided. 5.0 Subdrain Installation Subdrain systems shall be installed in accordance with the approved geotechnical report(s), the grading plan, and the Standard Details. The Geotechnical Consultant may recommend additional subdrains and/or changes in subdrain extent, location, grade, or material depending on conditions encountered during grading. All subdrains shall be surveyed by a land surveyor/civil engineer for line and grade after installation and prior to burial. Sufficient time should be allowed by the Contractor for these surveys. 6.0 Excavation Excavations, as well as over-excavation for remedial purposes, shall be evaluated by the Geotechnical Consultant during grading. Remedial removal depths shown on geotechnical plans are estimates only. The actual extent of removal shall be determined by the Geotechnical Consultant based on the field evaluation of exposed conditions during grading. Where fill-over-cut slopes are to be graded, the cut portion of the slope shall be made, evaluated, and accepted by the Geotechnical Consultant prior to placement of materials for construction of the fill portion of the slope, unless otherwise recommended by the Geotechnical Consultant. 7.0 Trench Backfills 7.1 Safetv The Contractor shall follow all OSHA and Cal/OSHA requirements for safety of trench excavations. -6- LEIGHTON AND ASSOCIATES, INC. General Earthwork and Grading Specifications 7.2 Bedding and Backfill All bedding and backfill of utility trenches shall be performed in accordance with the applicable provisions of Standard Specifications of Public Works Construction. Bedding material shall have a Sand Equivalent greater than 30 (SE>30). The bedding shall be placed to 1 foot over the top of the conduit and densified. Backfill shall be placed and densified to a minimum of 90 percent of relative compaction from 1 foot above the top of the conduit to the surface. The Geotechnical Consultant shall test the trench backfill for relative compaction. At least one test should be made for every 300 feet of trench and 2 feet of fill. 7.3 Lift Thickness Lift thickness of trench backfill shall not exceed those allowed in the Standard Specifications of Public Works Construction unless the Contractor can demonstrate to the Geotechnical Consultant that the fill lift can be compacted to the minimum relative compaction by his alternative equipment and method. 7.4 Observation and Testing The densification of the bedding around the conduits shall be observed by the Geotechnical Consultant. PROJECTED PLANE 1:1 (HORIZONTAL: VERTICAL) MAXIMUM FROM TOE or SLOPE TD APPROVED GROUND EXISTING GROUND SURFACE 2 FEET MIN.—' KEY DEPTH LOWEST BENCH (KEY) BENCH HEIGHT (4 FEET TYPICAL) REMOVE UNSUITABLE MATERIAL RLL-OVm-CUT SLOPE EXISTING GROUND SURFACE BENCH HEIGHT 4 FEET TYPICAL) REMOVE UNSUITABLE MATERIAL CUT-OVER-FLL a.OPE OVERBUILD AND TRIM BACK -CUT FACE SHALL BE CONSTRUCTED PRIOR TO FILL PLACEMENT TO ALLOW VIEWING OF GEOLOGIC CONDITIONS EXISTING GROUND SURFACE PROJECTED PLANE 1 TO 1 MAXIMUM FROM TOE OF SLOPE TO APPROVED GROUND 2 FEET MIN.- KEY DEPTH UT FACE SHALL BE CONSTRUCTED PRIOR TO FILL PLACEMENT REMOVE UNSUITABLE MATERIAL ^15 FEET MIN.^ LOWEST BENCH (KEY) BENCH HEIGHT (4 FEET TYPICAL) BENCHING SHALL BE DONE WHEN SLOPE'S ANGLE IS EQUAL TO OR GREATER THAN 5:1, MINIMUM BENCH HEIGHT SHALL BE 4 FEET AND MINIMUM FILL WIDTH SHALL BE 9 FEET. KEYING AND BENCHING GENERAL EARTHWORK AND GRADING SPECIFICATIONS STANDARD DETAIL A FINISH GRADE SLOPE FACE • OVERSIZE ROCK IS LARGER THAN 8 INCHES IN LARGEST DIMENSION, • EXCAVATE A TRENCH IN THE COMPACTED FILL DEEP ENOUGH TO BURY ALL THE ROCK. • BACKFILL WITH GRANULAR SOIL JETTED OR FLOODED IN PLACE TO FILL ALL THE VOIDS- • DO NOT BURY ROCK WITHIN 10 FEET OF FINISH GRADE, • WINDROW OF BURIED ROCK SHALL BE PARALLEL TO THE FINISHED SLOPE. GRANULAR MATERIAL TO BE' DENSIFIED IN PLACE BY FLOODING OR JETTING. DETAIL "JETTED OR FLOODED GRANULAR MATERIAL TYPICAL PROFILE ALONG WINDROW OVERSIZE ROCK DISPOSAL GENERAL EARTHWORK AND GRADING SPECIFICATIONS STANDARD DETAIL B 4B N -EXISTING GROUND SURFACE BENCHING REMOVE UNSUITABLE MATERIAL SUBDRAIN TRENCH SEE DETAIL BELOW CALTRANS CLASS 2 PERMEABLE--- -yy OR #2 ROCK (9FT"3/FT) WRAPPED IN FILTER FABRIC // • FILTER FABRIC (MIRAFI 140N OR APPROVED EQUIVALENT)* 4" MIN, BEDDING COLLECTOR PIPE SHALL BE MINIMUM 6" DIAMETER SCHEDULE 40 PVC PERFORATED PIPE- SEE STANDARD DETAIL D FOR PIPE SPECIFICATIONS SMgPRAIN PETAIl DESIGN FINISH • 10" MIN, BACKFILL / ^-^:-XOMPACTE0 F 11 '-.-y.-'s,-. / NONPERFORATEO 6 0 MIN PERFORATED 6" 0 MIN. PIPE -FILTER FABRIC (MIRAFI 140N OR APPROVED EQUIVALENT) CALTRANS CLASS 2 PERMEABLE OR #2 ROCK (9FT-3/FT) WRAPPED IN FILTER FABRIC PETAIL OF CANYON SUBDRAIN OUTLET CANYON SUBDRAINS GENERAL EARTHWORK AND GRADING SPECIFICATIONS STANDARD DETAIL C 15' MIN. OUTLET PIPES 4" 0 NONPERFORATEO PIPE. 100' MAX. OC, HORIZONTALLY, 30' MAX 0,C VERTICALLY BACK CUT 1:1 OR FLATTER SEE SUBDRAIN TRENCH DETAIL LOWEST SUBDRAIN SHOULD iE SITUATED AS LOW AS POSSIBLE TO ALLOW SUITABLE OUTLET -KEY DEPTH (2' MIN ) KEY WIDTH AS NOTED ON GRADING PLANS (15' MIN,) 12" MIN. OVERLAP- FROM THE TOP HOC RING TIED EVERY 6 FEET CALTRANS CLASS PERMEABLE OR §2 ROCK (3 FT-3/FT) WRAPPED IN FILTER FABRIC -4" 0 NON-PERFORATED OUTLET PIPE PROVIDE POSITIVE SEAL AT THE JOINT T-CONNECTION FOR COLLECTOR PIPE TO OUTLET PIPE 4" 0 PERFORATED PIPE FILTER FABRIC ENVELOPE (MIRAFI 140 OR APPROVED EQUIVALENT) 4 MIN, BEDDING SUBDRAIN TRENCH DETAIL SUBDRAIN INSTALLATION - subd'oin collector pipe Shalt be instolled with perforotion down or unless otherwise designoted by the geotechnical consultont. Outlet pipes sholl be non-perforoted pipe. The subdroin pjpe sholl have at leost 8 perforotions uniformly spoced per foot, Perforotion Sholl be 1/4" to 1/2" if drill holes are used. Ail subdroin pipes shell hove o grodieiit of ot leost 2% towords the outlet. SUBDRAIN PIPE - Sutjdroin pipe shall be ASTM D2751. SDR 23,5 or ASTM 01527, Schedule 40 or ASTM 03034, SDR 23,5, Schedule 40 Polyvinyl Chloride Plostic (PVC) pipe All outlet pipe sholl be ploced in o trench no wider thon twice the subdroin pipe. BUTTRESS OR REPLACEMENT FILL SUBDRAINS GENERAL EARTHWORK AND GRADING SPECIFICATIONS STANDARD DETAIL D CUT-FILL TRANSITION LOT OVEREXCAVATION REMOVE UNSUITABLE GROUND• 5" MIN V< TYPICAL BENCHING OVEREXCAVATE AND RECOMPACT UNWEATHERED BEDROCK OR MATERIAL APPRO\€D BY THE GEOTECHNICAL CONSULTANT- TRANSITION LOT FILLS GENERAL EARTHWORK AND GRADING SPECIFICATIONS STANDARD DETAIL E SOIL BACKFILL, COMPACTED TO 90 PERCENT RELATIVE COMPACTION BASED ON ASTM 01557 RETAINING WALL- WALL WATERPROOFING PER ARCHITECT'S SPECIFICATIONS WALL FOOTING FILTER FABRIC ENVELOPE (MIRAFI HON OR APPROVED EQUIVALENT)" 3/4" TO 1-1/2" CLEAN GRAVEL 4" (MIN ) DIAMETER PERFORATED PVC PIPE (SCHEDULE 40 OR EQUIVALENT) WITH PERFORATIONS ORIENTED DOWN AS DEPICTED MINIMUM 1 PERCENT GRADIENT TO SUITABLE OUTLET COMPETENT BEDROCK OR MATERIAL AS EVALUATED BY THE GEOTECHNICAL CONSULTANT NOTE: UPON REVIEW BY THE GEOTECHNICAL CONSULTANT, COMPOSITE DRAINAGE PRODUCTS SUCH AS MIRADRAIN OR J-ORAIN MAY BE USED AS AN ALTERNATIVE TO GRAVEL OR CLASS 2 PERMEABLE MATERIAL INSTALLATION SHOULD BE PERFORMED IN ACCORDANCE WITH MANUFACTURER'S SPECIFICATIONS. RETAINING WALL DRAINAGE GENERAL EARTHWORK AND GRADING SPECIFICATIONS STANDARD DETAIL F ACTIVE ZONE GRAVEL J.-. .VyV DRAINAGE FILL MIN 6" BELOW WALL MIN 12" BEHIND UNITS BACKDRAIN TO 70% OF WALL HEIGHT WALL SUBDRAIN FOUNDATION SOILS REAR SUBDRAIN: 4" (MIN) DIAMETER PERFORATED PVC PIPE (SCHEDULE 40 OR EQUIVALENT) WITH PERFORATIONS DOWN. SURROUNDED BY 1 CU. FT/FT OF 3/4" GFiAVEL WRAPPED IN FILTER FABRIC (MIRAFI 140N OR EQUIVALENT) OUTLET SUBDRAINS EVERY 100 FEET, OR CLOSER, BY TIGHTLINE TO SUITABLE PROTECTED OUTLET GRAVEL DRAINAGE FILL: SIEVE SIZE % PASSING 1 INCH 3/4 INCH NO, 4 NO, 40 NO, 200 100 75-100 0-60 0-50 0-5 NOTES: 1) MATERIAL GRADATION AND PLASTICITY REINFORCED ZONE: SIEVE SIZE % PASSING 1 INCH 100 NO, 4 20-100 NO. 40 0-60 NO, 200 0-35 FOR WALL HEIGHT < 10 FEET. PLASTICITY INDEX < 20 FOR WALL HEIGHT 10 TO 20 FEET, PLASTICITY INDEX < 10 FOR TIERED WALLS, USE COMBINED WALL HEIGHTS WALL DESIGNER TO REQUEST SITE-SPECIFIC CRITERIA FOR WALL HEIGHT > 20 FEET 2) CONTRACTOR TO USE SOILS WITHIN THE RETAINED AND REINFORCED ZONES THAT MEET THE STRENGTH REQUIREMENTS OF WALL DESIGN. 3) GEOGRID REINFORCEMENT TO BE DESIGNED BY WALL DESIGNER CONSIDERING INTERNAL, EXTERNAL, AND COMPOUND STABILITY. 3) GEOGRID TO BE PRETENSIONED DURING INSTALLATION, 4) IMPROVEMENTS WITHIN THE ACTIVE ZONE ARE SUSCEPTIBLE TO POST-CONSTRUCTION SETTLEMENT. ANGLE a 45-i-4>/2, WHERE 4> IS THE FRICTION ANGLE OF THE MATERIAL IN THE RETAINED ZONE. 5) BACKDRAIN SHOULD CONSIST OF J-DRAIN 302 (OR EQUIVALENT) OR 6-INCH THICK DRAINAGE FILL WRAPPED IN FILTER FABRIC, PERCENT COVERAGE OF BACKDRAIN TO BE PER GEOTECHNICAL REVIEW, SEGMENTAL RETAINING WALLS GENERAL EARTHWORK AND GRADING SPECIFICATIONS STANDARD DETAIL G 18" min. I Compacted I Fill • -crushed dr I'l rock, - \| 2/3"wall it height CD' Typical Retaining Wall Subdrain Detail Not to Scale Miradrain 6000 or equivalent. 2f3 waf! height © Floor Slab (5) Filter Fabric between rock and sorl (3) Backcut © Waterproof back of wall foilowing architect s specifications @ 4* minimum perforated pipe, SDR35 or equivalent, fioles down, 1 % fait to outlet, top of pipe betow lop of slab, encased in 3^4* crushed rock. Provide 3 cubic feet per linear foot crushed rock minimum. Crushed rock to be surrounded by filter fabric (Mirati 140N or equivalent), with 6" minimum overlap. Provide solid outlet pipe at suitable location. EC .ST- SOUTHERN CALIFORNIA LA COS IA TOWN CENTER EC .ST-SOIL & TESTING. INC. BY; MF DATE; 04-20-04 JOB NUMBER: 0411014-4 PLATE NO,: 7 APPENDIX C GENERAL EARTHWORK AND GRADING SPECIFICATIONS 042631-001 APPENDIX B Laboratory Testinq Procedures and Test Results Moisture and Density Determination Tests: Moisture content and dry density determinations were performed on relatively undisturbed samples obtained from the test borings. The results of these tests are presented in the boring logs. Where applicable, only moisture content was determined from "undisturbed" or disturbed samples. B-1 JOB NAME: La Costa Town Center JOB NUMBER: 0411014-4 IN-PLACE DENSITY TESTS TEST ELEVATION MOISTURE DRY DENSITY SOIL REL.COMP. NO. DATE LOCATION (feet.MSL) (percent) (p.c.f.) TYPE (percent) GRADING 1 1/16/04 See Plan 310 0 11.9 125.6 1C 95,9 2 1/16/04 See Plan 312.0 10,7 130,2 IF 95,5 3 1/16/04 See Plan 314 0 12,2 127.4 ID 96,1 4 1/16/04 See Plan 3160 9.8 124 9 IF 91,6 5 1/16/04 See Plan 318 0 11,7 128.4 1E 95,6, 6 1/16/04 See Plan 320 0 11.3 130.0 2> • 93.5 7 1/16/04 See Plan 322,0 111 129,2 2E 94.2 8 1/19/04 See Plan 324 0 132 128,8 2E 93,9 9 1/19/04 See Plan 3260 118 126,7 2F 91,1 10 1/19/04 See Plan 328,0 12.7 127.2 2F 91.4 11 1/19/04 See Plan 330.0 14,1 125.8 1E 93,7 12 1/19/04 See Plan 332.0 14.6 130 6 IF 95,7 13 1/19m See Plan 334,0 14,0 131,4 2F 94,5 14 1/19/04 See Plan 336.0 13.8 127.7 2C 953 15 1/19/04 See Plan 338.0 15,1 128.3 2E 93,5 16 1/20/04 See Plan 340,0 10.7 126.8 IE 94,4 17 1/20/04 See Plan 3400 11,4 130,4 IF 95-6 18 1/20/04 See Plan 342 0 11,7 125.9 ID 94.9 19 1/20/04 See Plan 342.0 10.9 128.6 IF 94.3 20 1/28/04 See Plan 358,0 9.7 123.1 2A 94.0 21 1/28/04 See Plan 361,0 10.4 125.2 2B 94.5 22 1/28/04 See Plan 369,0 11.5 124.3 2B 93.8 23 1/29/04 See Plan 344,0 10.7 126.9 ie 94.5 24 1/29/04 See Plan 344.0 11.4 128,4 1F 94,1 25 1/29/04 See Plan 346.0 9.2 130.2 IF 95,5 26 1/29/04 See Plan 346.0 8 7 125.6 ID 94,7 27 1/29/04 See Plan 348.0 11.6 127.7 IE 95.1 28 1/29/04 See Plan 348.0 128 127.4 IE 94,9 29 1/29/04 See Plan 350,0 15.2 125,2 ID 944 30 1/29/04 See Plan 350.0 11.1 130.0 IF 95.3 31 1/29/04 See Plan 352 0 10.6 126.8 IE 94.4 32 1/30/04 See Plan 352.0 9.7 125.4 1E 93.4 33 1/30/04 See Plan 3540 8.4 130.6 IF 95,7 34 1/30/04 See Plan 354.0 10.8 129.9 IF 95.2 35 1/30/04 See Plan 356.0 11.2 127.4 1F 93,4 36 1/30/04 See Plan 356 0 10.4 126 6 IF 92.8 37 1,'30./04 See Plan 358 0 9.6 131.2 1F 96.2 38 1/30/04 See Plan 358.0 10.1 126.3 1F 92,6 39 2/5/04 See Plan 351.0 10.7 129,6 IF 95.0 40 2/5/04 See Plan 353,0 11.5 130.1 IF 95.4 41 2/5/04 See Plan 356.0 9.4 125,9 10 94,9 42 2./5/04 See Plan 360.0 9.7 126.7 1E 94,3 43 215/04 See Plan 360.0 10.1 125.4 IE 93.4 44 2/5/04 See Plan 362.0 8.7 128.2 1F 94.0 45 2/5/04 See Plan 362.0 9.4 127.3 1F 93.3 46 2/12/04 See Plan 364.0 18.9 100.7 7 97,0 47 2/12/04 See Plan 364.0 22.1 100,4 7 96,7 48 2/12/04 See Plan 366,0 20,4 100.2 7 96.5 49 2/12/04 See Plan 366,0 19.8 100.9 7 97.2 PLATE NO. 3 JOB NAME: La Costa Town Center JOB NUMBER: 0411014-4 IN-PLACE DENSITY TESTS TEST ELEVATION MOISTURE DRY DENSITY SOIL REL.CO NO. DATE LOCATION (feet.MSL) (percent) (p.c.f.) TYPE (percei 50 2/13/04 See Plan 364.0 10.6 126,7 1E 94.3 51 2/13/04 See Plan 364,0 11.1 1302 1F 95.5 52 2/13'04 See Plan 366.0 9.6 1284 IE 95,6 53 2/13,/04 See Plan 366.0 9.2 131,2 IF 96,2 54 2/17/04 See Plan 368.0 17,9 109,4 3 90,8 55 2/1 7''04 See Plan 370,0 18 1 110,1 3 91,4 56 2/17.''34 See Plan 372.0 16,9 109.2 3 90.6 57 2/1 7/04 See Plan 374,0 20,4 106.9 4 90,6 58 2/17/04 See Plan 376.0 19,7 107,3 4 90,9 59 2/25/04 See Plan 378.0 15,9 107.9 4 914 60 2/25/04 See Plan 378.0 16,8 106.8 4 90,5 61 2/25/04 See Plan 380.0 14.6 107.8 4 91.4 62 2/25/04 See Plan 380.0 13.8 109.1 4 92.6 63 2/25/04 See Plan 372,0 18,4 89,7 7 864 64 2/25/04 See Plan 371,0 19,6 94.8 7 91,3 65 2/25/04 RETEST OF 63 372,0 16.9 93.9 7 90.6 66 2/25/04 See Plan 371,0 19,2 95.2 7 91.7 67 2/25/04 See Plan 374,0 18.7 99.6 7 96,0 68 2/25/04 See Plan 3680 16.8 108.2 4 91,7 69 2/25/04 See Plan 371 0 14.4 109.8 4 93,1 70 3/1/04 See Plan 374,0 18.9 97.7 7 94 1 71 3/1/04 See Plan 374 0 19.4 101.1 7 97,4 72 3/1/04 See Plan 373,0 20.1 95.8 7 92 3 73 3/1/04 See Plan 376 0 17.8 97 9 7 94,3 74 3/1/04 See Plan 378,0 16.9 92.1 7 88,7 75 3/1/04 RETEST OF 74 378,0 19.4 94.6 7 91,1 76 3/1/04 See Plan 374.0 14,6 99.2 5 88.6 77 3/1/04 See Plan 374.0 15.9 104.6 5 934 78 3/1/04 RETEST OF 76 374.0 17.7 102.9 5 91.9 79 3/1/04 See Plan 376.5 14.8 101.6 5 90.7 80 3/1/04 See Plan 376.0 16.7 100,9 5 90.1 81 3/2/04 See Plan 378,5 17.4 101.5 5 90.6 82 3/2/04 See Plan 380,0 17.9 100 7 7 97.0 83 3/2/04 See Plan 376.0 20.6 102.4 6 91,4 84 3/2/04 See Plan 375.0 16.8 101.1 5 90,3 85 3/2/04 See Plan 378,0 19.4 99.4 5 88.8 86 3/2/04 RETEST OF 85 378.0 18.5 100.9 5 90,1 87 3/2/04 See Plan 377.0 20.2 101.6 5 90,7 88 3/2/04 See Plan 380.0 15.9 102.7 5 91,7 89 3/3/04 See Plan 380.0 19.6 103.6 5 92.5 90 mm See Plan 379.0 18.8 101,9 5 91.0 91 3/3/04 See Plan 379.0 20.4 102.7 5 91.7 92 3/3/04 See Plan 381.0 21.1 100.9 5 90,1 93 3/3/04 See Plan 381.0 16.9 104,2 5 93,0 94 3/3/04 See Plan 382.0 18.4 100.8 5 90.0 95 3/8/04 See Plan 372.0 18.6 102.9 5 91.9 m 3/12/04 See Plan 370.0 16.1 102,0 5 91 1 97 3/12/04 See Plan 372.0 15,9 101.6 5 90.7 98 3/12/04 See Plan 374.0 17.2 104.7 5 93.5 99 3/12/04 See Plan 382.0 FG 15.6 103,1 5 92.1 100 3/12/04 See Plan 381.0 FG 14.7 102,0 5 91,1 PLATE NO, 4 JOB NAME: La Costa Town Center JOB NUMBER: 0411014-4 IN-PLACE DENSITY TESTS TEST NO. DATE LOCATION ELEVATION (feetMSL) MOISTURE (percent) DRY DENSITY (p.c.f.) SOIL TYPE REL.COMP. 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 3/12/04 .3/15/04 3/15/04 3/15/04 3/15/04 3/15/04 3/15/04 3/15/04 3/15/04 3/15/04 3/15/04 3/15/04 3/15/04 3/15/04 3/17/04 3/17/04 3/17/04 3/17/04 3/17/04 3/17/04 3/17/04 3/18/04 3/18/04 3/18/04 3/18/04 3/18/04 3/29/04 3/29/04 3/29/04 3/29/04 3/29/04 3/29/04 3/29/04 See Plan See Plan See Plan See Plan See Plan See Plan See Plan See Plan See Plan See Plan See Plan See Plan See Plan See Plan See Plan See Plan See Plan See Plan See Plan See Plan See Plan See Plan See Plan See Plan See Plan See Plan See Plan See Plan See Plan See Plan See Plan See Plan See Plan 381,0 FG 372,0 363.0 368.0 354 0 369.0 355.0 371,0 348,0 365.0 372,0 363.0 373.0 356,0 380.0 FG 380 380 380 379 378 378 379 379 OFG 0 FG 0 FG 0 FG OFG OFG 0 FG OFG 381 376 377 0 FG 377.0 FG 377 0 FG 0 FG 383 0 FG 383.0 FG 0 FG 368.0 FG 374 0 FG 374.0 FG FG = Finish Grade STORM DRAIN SD1 1/26/04 Storm Drain "A" 332 0 SD2 1/26/04 Storm Drain "A" 336.0 SD3 1/26/04 Storm Drain "A" 339.0 SD4 2/2/04 Storm Drain "A" 349.0 SD5 2/2/04 Storm Drain "A" 352,0 SD6 2/2/04 Storm Drain "A" 355,0 SD7 2/2/04 Storm Drain "A" 358,0 SD8 2/9/04 Storm Drain "A" 329.5 SD9 2/9/04 Storm Drain "A" 332.0 SD10 2/9/04 Storm Drain "A" 335.0 SD11 2/25104 Storm Drain "C" 315.5 SD12 2/25/04 Storm Drain "C" 317.5 SD13 2/25/04 Storm Drain "C" 319.5 SD14 2/25/04 Storm Drain "C 321.5 13,9 16.1 14.9 13,7 16,1 15,6 13 8 172 15.1 196 13.1 12.9 15.2 16.7 10.7 11.9 14,1 12,7 12.6 13,1 11.7 12.7 11.1 10.9 13,7 9.9 12.7 10,8 9.8 13.1 12.7 11.4 12.1 10.7 11.3 9.8 9.6 8.7 9.9 10,4 9.7 104 8.8 15,2 14,3 14.1 13 6 102.6 5 91.6 101.0 5 90.2 108.1 4 91.8 106.7 4 90,4 106.9 4 90,6 101.8 5 90,9 101.3 5 90,4 107.3 4 90,9 106.5 4 90,3 108.3 4 91.3 103.6 5 92.5 102.1 5 91,2 100.9 5 90.1 101.3 5 90.4 102 9 5 91,9 101.6 5 90,7 104.2 5 93,0 100.9 5 90.1 101,4 5 90.5 102.9 5 91.9 103.7 5 92.6 101.4 5 90.5 102.7 5 91.7 103.2 5 92.1 101.5 5 90.5 101.7 5 90.8 104.1 5 92.9 102.7 5 91.7 101,9 5 91.0 103.9 5 92.8 101.6 5 90.7 100.9 5 90.1 106.1 5 94,7 126,7 ID 95.6 124.9 ID 94.2 125.4 IE 934 128.7 1F 944 130.1 1F 95.4 126.4 IE 94.1 128.8 1F 944 127.5 1F 93.5 130.8 IF 95.9 126.1 IF 924 102.1 5 91.2 104.8 5 936 103.4 5 92.3 103.8 5 92.7 PLATE NO. 5 JOB NAME: La Costa Town Center JOB NUMBER: 0411014-4 IN-PLACE DENSITY TESTS TEST ELEVATION MOISTURE DRY DENSITY SOIL REL.COMP. NO. DATE LOCATION (feet.MSL) (percent) (p.c.f.) TYPE (percent) SD15 2/25/04 Storm Drain "G" 323,5 15.2 102.9 5 91.9 SD16 3/12/04 Storm Drain "B" 296 0 12.7 108.4 4 91.9 SD17 3/12/04 Storm Drain "B" 298,0 9.4 106,7 4 90.4 SD18 3/12/04 Storm Drain "B" 300,0 10.6 110.3 4 93,5 SD19 3/12/04 Storm Drain "B" 302,0 11.9 107.9 4 914 SD20 3/18/04 Storm Drain "B" 301 0 13.1 109.0 4 92,4 SD21 3/18/04 Storm Drain "B" 303 0 11.0 108.4 4 91 9 SD22 3/19/04 Abandoned Storm Drain 380,0 8.0 121 7 2 94,0 SD23 3/19/04 Abandoned Storm Drain 377.0 7,9 122,4 2 94,5 MAXIMUM DENSITY AND OPTIMUM MOISTURE SUMMARY (ASTM 01557) Soil Maximum Optimum Type Soil DescriDtion Density, Dcf Moisture, % 1 Reddish Brown Bitty Sand 126.2 8.9 1A Reddish Brown Silty Sand with 5% Rock 127.7 8,5 1B Reddish Brown Silty Sand with 10% Rock 129,3 8.1 1C Reddish Brown Silty Sand with 15% Rock 131.0 7.8 1D Reddish Brown Silty Sand with 20% Rock 132,6 7.4 IE Reddish Brown Silty Sand with 25% Rock 134.3 7.0 IF Reddish Brown Silty Sand with 30% Rock 136.4 6.6 2 Brown Silty Sand with rock 129.6 8,1 2A Brown Silty Sand with rock with 5% Rock 131.0 7.8 28 Brown Silty Sand with rock with 10% Rock 132,5 7.4 20 Brown Silty Sand with rock with 15% Rock 134.0 7.1 2D Brown Silty Sand with rock with 20% Rock 135,6 6.7 2E Brown Silty Sand with rock with 25% Rock 137.2 64 2F Brown Silty Sand with rock with 30% Rock 139.1 6.0 3 Light Brown Silty Sand 120.5 7.3 4 Light Tan to White Silty Sand 118.0 12.0 5 Tan to Brown Silty Sand/Sandy Silt with Clay 112,0 11.0 6 Brown Silty Sard with Clay 121.8 9.5 7 Tan Clayey to Sandy Silt 103.8 19.0 1 EXPANSION SAMPLE EXPANSION EXPANSION TEST SAMPLE LOCATION INDEX POTENTIAL El South Building 91 high E2 East Building 54 medium E3 South Building 84 medium E4 East Building 63 medium PLATE NO. 6 lulap Saved as P:\drafting\042631\001\GlS\of_2012-09-21\Figure1.mxd on 9/25/2012 4:30:40 PM PLATE Proposed Grade r Approximate Limit of Propos*d Ovirsxcavotic duB to metavolcanic n Proposed Grade T Af Af Jsp Approximate Limit of Proposed Overexcavation due to metavolcanic rock LEGEND APPROXIMATE GEOLOGIC CONTACT Af COMPACTED FILL FROM PREVIOUS GRADING (SCS&T. 2012) AfO PRE-EXISTING FILL Jsp SANTIAGO PEAK VOLCANICS (CIRCLED WHERE BURIED) "-If Leighten CROSS-SECTION A-A' LA COSTA TOWN CENTER CARLSBAD, CALIFORNIA Proj: 042631-001 Engraeol: WDO/MDJ Date: 09/2012 APPENDIX A REFERENCES 042631-001 APPENDIX A REFERENCES Blake, 2000, EQFAULT, Version 3.0. Bryant, W.A., and Hart E.W., 2007, Special Publication 42, Fault Rupture Hazard Zones in California, Alquist-Priolo Earthquake Fault Zoning Act with Index to Earthquake Fault Zone Maps, Interim Revision 2007. California Building Standards Commission (CBSC), 2010, California Building Code (CBC). Hart and Bryant, E.W., 2007, Fault-Rupture Hazard Zones in California, Alquist-Priolo Earthquake Fault Zoning with Index to Special Study Zones Maps: Department of Conservation, Division of Mines and Geology, Special Publication 42. Jennings, C.W., 1994, Fault Activity Map of California and Adjacent Areas; California Division of Mines and Geology, Geologic Data Map 6, Scale 1:750,000. Kennedy, M.P., 1977, Geology of San Diego Metropolitan Area, California: California Division of Mines and Geology, Bulletin 200. Latitude 33 Planning and Engineering, 2012, Preliminary Site Grading Plan, La Costa Town Center, Carlsbad, California, received September 2012. Lindvall, S.C., and Rockwell, T.K., 1995, Holocene Activity of the Rose Canyon Fault Zone in San Diego, California: Journal of Geophysical Research, V. 100, No. B12, p. 24, 124-24, 132. Southern California Soil & Testing, Inc., 2012, Update Geotechnical Investigation, La Costa Town Square, North Residential Development, Carlsbad California, dated January 3, 2012 Treiman, J.A., 1984, The Rose Canyon Fault Zone: A Review and Analysis, California Division of Mines and Geology, Funded by Federal Management Agency Cooperative Agreement EMF-83-K-0148. A-1 042631-001 APPENDIX A (Continued) 1993, The Rose Canyon Fault Zone, Southern California: California Division of Mines and Geology, Open-File Report 93-2, 45p. A-2 APPENDIX B LABORATORY TESTING AND FIELD DENSITY TESTS BY OTHERS 042631-001 Table 5 Post-Tensioned Foundation Design Recommendations Design Criteria Cateqorv 1 Very Low to Low Expansion Potential (El 0 to 50) Differential Fill Thickness less than 10 feet Cateqorv 11 Medium Expansion Potential (El 51 to 90) Differential Fill Thickness between 10 and 20 feet Cateaorv III High Expansion Potential (El 91 to 130) Differential Fill Thickness between 20 and 40 feet Edge Moisture Variation, em Center Lift: 9.0 feet 8.3 feet 7.0 feet Edge Moisture Variation, em Edge Lift: 4.8 feet 4.2 feet 3.7 feet Differential Swell, Center Lift: 0.46 inches 0.75 inches 1.09 inches Differential Swell, Edge Lift: 0.65 inches 1.09 inches 1.65 inches Perimeter Footing Depth: 18 inches 24 inches 30 inches Allowable Bearing Capacity 2,000 psf The post-tensioned (PT) foundation and slab should also be designed in accordance with structural considerations. For a ribbed PT foundation, the concrete slabs section should be at least 5 inches thick. Continuous footings (ribs or thickened edges) with a minimum width of 12 inches and a minimum depth of 12 inches below lowest adjacent soil grade may be designed for a maximum allowable bearing pressure of 2,000 pounds per square foot. For a uniform thickness "mat" PT foundation, the perimeter cut off wall should be at least 8 inches below the lowest adjacent grade. However, note that where a foundation footing or perimeter cut off wall is within 3 feet (horizontally) of adjacent drainage swales, the adjacent footing should be embedded a minimum depth of 12 inches below the swale flow line. The allowable bearing capacity may be increased by one-third for short-term loading. The slab subgrade soils should be presoaked in accordance with the recommendation presented in Table 4 above prior to placement of the moisture barrier. -23- Leigtitofl: 042631-001 The slab should be underlain by a moisture barrier as discussed in Section 5.51 above. Note that moisture barriers can retard, but not eliminate moisture vapor movement from the underlying soils up through the slabs. We recommend that the floor covering installer test the moisture vapor flux rate prior to attempting applications of the flooring. "Breathable" floor coverings should be considered if the vapor flux rates are high. A slip-sheet or equivalent should be utilized above the concrete slab if crack-sensitive floor coverings (such as ceramic tiles, etc.) are to be placed directly on the concrete slab. Additional guidance Is provided In ACI Publications 302.1 R-04 Guide for Concrete Floor and Slab Construction and 302.2R-06 Guide for Concrete Slabs that Receive Moisture-Sensitive Floor Materials. Based on an overall geotechnical evaluation of the El values and their locations, we anticipate Post-Tension Foundation Category II and III for the site. 5.6 Retaining Wall Design and Lateral Earth Pressure We anticipate that several relatively small retaining walls are proposed at the site. For design purposes, the following lateral earth pressure values for level or sloping backfill are recommended for retaining walls backfilled with onsite soils of medium to high expansion potential (expansion potential greater than 50 per ASTM Test Method D4829). Table 6 Static Equivalent Fluid Weight (pcf) Conditions Level 2:1 Slope Active 40 65 At-Rest 55 90 Passive 300 (Maximum of 3 ksf) 140 (Sloping Down) Unrestrained (yielding) cantilever walls up to 15 feet in height should be designed for an active equivalent pressure value provided in table above. For the design of walls restrained from movement at the top (nonyielding) such as basement walls, the at-rest pressures should be used. If conditions other than those covered herein are anticipated, the equivalent fluid pressure values should be provided on -24- Lfeiqhton 042631-001 an individual case basis by the geotechnical engineer. A surcharge load for a restrained or unrestrained wall resulting from automobile traffic may be assumed to be equivalent to a uniform horizontal pressure of 75 psf which is in addition to the equivalent fluid pressure given above. For other uniform surcharge loads, a uniform horizontal pressure equal to 0.35q should be applied to the wall (where q is the surcharge pressure In psf). To account for potential redistribution of forces during a seismic event, basement walls, If any, that fall within the requirements of ASCE 7-05 Section 15.6.1 should also be checked considering an additional uniform seismic pressure distribution equal to 10H psf, where H equals the overall retained height in feet. The wall pressures assume walls are backfilled with free draining materials and water is not allowed to accumulate behind walls. A typical wall drainage design Is provided in Appendix D. Importing or selective grading may be necessary to obtain retaining wall backfill material. Wall backfill should be brought to at least 3 percent above the optimum moisture content and compacted by mechanical methods to at least 90 percent relative compaction (based on ASTM D1557). Wall footings should be designed In accordance with the foundation design recommendations and reinforced in accordance with structural considerations. The bearing pressure for retaining walls should be limited to 2,500 psf for footing founded in compacted fill. Footing embedment depth should be at least 18 inches below the lowest adjacent grade. For all retaining walls, we recommend a minimum horizontal distance from the outside base of the footing to daylight of 10 feet. Lateral soil resistance developed against lateral structural movement can be obtained from the passive pressure value provided above. Further, for sliding resistance, the friction coefficient of 0.33 may be used at the concrete and soil interface. These values may be increased by one-third when considering loads of short duration including wind or seismic loads. The total resistance may be taken as the sum of the frictional and passive resistance provided that the passive portion does not exceed two-thirds of the total resistance. 5.7 Preliminary Pavement Design The appropriate pavement section will depend on the type of subgrade soil, shear strength, traffic load, and planned pavement life. Since an evaluation of the actual subgrade soils cannot be made at this time, we have used an assumed R-value of 15 and Traffic Indices (TI) of 4.5, 5 and 6 for the parking/auto driveways and truck -25- Leiqliton 042631-001 driveways, respectively. The range of onsite pavement sections presented on Table 7 Is to be used for preliminary planning purposes only. Final pavement designs should be completed after R-value tests have been performed on actual subgrade materials. Table 7 Preliminary Pavement Section Designs Traffic Index Preliminary Pavement Section 4.5 4 inches AC over 5 Inches Class 2 Aggregate Base 5 4 inches AC over 6 Inches Class 2 Aggregate Base 6 4 Inches AC over 12 Inches Class 2 Aggregate Base Prior to placing the pavement section, the subgrade soils should have a relative compaction of at least 95 percent to a minimum depth of 12 inches (based on ASTM Test Method D1557). Aggregate Base should be compacted to a minimum of 95 percent relative compaction (based on ASTM Test Method D1557) prior to placement of the AC. All concrete pavement sections, including concrete curbs and gutters, should be underlain by at least 6 Inches of aggregate base (AB) compacted to 95 percent relative compaction. The Asphalt Concrete (AC) and Class 2 Aggregate Base shall conform to and be placed in accordance with the latest revision of the California Department of Transportation Standard Specifications (Section 26), the Greenbook specifications, and/or the City of Carlsbad requirements. Asphalt Concrete shall conform to and be placed in accordance with the "Greenbook" Standard Specifications for Public Works Construction and the City of Carlsbad requirements. The following table presents recommendations for the concrete pavement sections subject to vehicle loading. Subgrade soils are assumed to have an R-value of least 15 and compacted to at least 95 percent relative compaction. -26- Leighton 042631-001 Table 8 1 Preliminary Concrete Pavement Design Traffic Index Minimum PCC Section (MR = 600 psi min.) 5 6.5 Inches PCC 6 7.0 Inches PCC 5.8 Slope Stability It is our understanding that the existing slopes up to 35 feet in height will remain. Based on our experience and observation of the performance of similar smaller slopes in the site area, it is our opinion that the existing 2 to 1 (horizontal to vertical) slopes, will be grossly stable. 5.9 Concrete Flatworit Concrete sidewalks and other flatwork (Including construction joints) should be designed by the project civil engineer and should have a minimum thickness of 4 inches. For all concrete flatwork, the upper 12 inches of subgrade soils should be moisture conditioned to at least 3 to 6 percent above optimum moisture content depending on the soil type and compacted to at least 90 percent relative compaction based on ASTM Test Method D1557 prior to the concrete placement. For all concrete flatwork driveways and sidewalks, the subgrade soils should be should also be presoaked as discussed In Table 4 above prior to placement of concrete, and should contain reinforcement steel with dowels Into existing adjacent concrete to the concrete placement. Moisture testing by Leighton should be performed 24 hours prior to concrete placement. 5.10 Slope IVIaintenance Guidelines It is the responsibility of the owner or owner's association to maintain the slopes, including adequate planting, proper irrigation and maintenance, and repair of faulty irrigation systems. To reduce the potential for erosion and slumping of graded slopes, all slopes should be planted with ground cover, shrubs, and plants that develop dense, deep root structures and require minimal irrigation. Slope planting should be carried out as soon as practical upon completion of -27- Leiqhtoii 042631-001 grading. Surface-water runoff and standing water at the top-of-slopes should be avoided. Oversteepening of slopes should also be avoided during construction activities and landscaping. Maintenance of proper drainage, undertaking of Improvements in accordance with sound engineering practices, and proper maintenance of vegetation. Including regular slope Irrigation, should be performed. Slope Irrigation sprinklers should be adjusted to provide maximum uniform coverage with minimal of water usage and overlap. Overwatering and consequent runoff and ground saturation should be avoided. If automatic sprinklers systems are Installed, their use must be adjusted to account for rainfall conditions. Trenches excavated on a slope face for any purpose should be properly backfilled and compacted in order to obtain a minimum of 90 percent relative compaction, in accordance with ASTM Test Method D1557. Observation/testing by the geotechnical consultant during trench backfill are recommended. A rodent- control program should be established and maintained. Prior to planting, recently graded slopes should be temporarily protected against erosion resulting from rainfall, by the implementing slope protection measures such as polymer covering, jute mesh, etc. 5.11 Landscaping and Post-Construction Landscaping and post-construction practices carried out by the owner and their representatives exert significant influences on the integrity of structures founded on expansive soils. Improper landscaping and post-construction practices, which are beyond the control of the geotechnical engineer, are frequently the primary cause of distress to these structures. Recommendations for proper landscaping and post-construction practices are provided in the following paragraphs within this section. Adhering to these recommendations will help in minimizing distress due to expansive soils, and In ensuring that such effects are limited to cosmetic damages, without compromising the overall integrity of structures. Initial landscaping should be done on all sides adjacent to the foundation of a structure or associated improvements, and adequate measures should be taken to ensure drainage of water away from the foundation or improvement. If larger, shade providing trees are desired, such trees should be planted away from structures or improvements (at a minimum distance equal to half the mature height -28- Leighton 042631-001 of the tree) In order to prevent penetration of the tree roots beneath the foundation of the structure or improvement. Locating planters adjacent to buildings or structures should be avoided as much as possible. If planters are utilized in these locations, they should be properly designed so as to prevent fluctuations in the moisture content of the subgrade soils. Planting areas at grade should be provided with appropriate positive drainage. Wherever possible, exposed soil areas should be above paved grades. Planters should not be depressed below adjacent paved grades unless provisions for drainage, such as catch basins and drains, are made. Adequate drainage gradients, devices, and curbing should be provided to prevent runoff from adjacent pavement or walks into planting areas. Watering should be done In a uniform, systematic manner as equally as possible on all sides of the foundation, to keep the soil moist. Irrigation methods should promote uniformity of moisture In planters and beneath adjacent concrete flatwork. Overwatering and underwatering of landscape areas must be avoided. Areas of soil that do not have ground cover may require more moisture, as they are more susceptible to evaporation. Ponding or trapping of water in localized areas adjacent to the foundations can cause differential moisture levels in subsurface soils and, therefore, should not be allowed. Trees located within a distance of 20 feet of foundations would require more water in periods of extreme drought, and in some cases, a root injection system may be required to maintain moisture equilibrium. During extreme hot and dry periods, close observations should be carried out around foundations to ensure that adequate watering is being undertaken to prevent soil from separating or pulling back from the foundation. 5.12 Future Investigation The findings of this report indicate that the proposed grading is geotechnically feasible. Prior to construction, additional geotechnical investigation will be required to further evaluate metavolcanic rock and fill areas to provide additional subsurface information regarding oversized rock and excavation characteristics of metavolcanic rock. In addition, laboratory testing to assess soil corrosivity will need to be performed during a future site investigation. This information may then be utilized to provide additional construction level recommendations. Leighton 042631-001 5.13 Construction Observation and Testing and Plan Review The geotechnical consultant should perform construction observation and testing during the fine, and post grading operations, future excavations and foundation or retaining wall construction at the site. Additionally, footing excavations should be observed and moisture determination tests of the slab subgrade soils should be performed by the geotechnical consultant prior to the pouring of concrete. Foundation design plans should also be reviewed by the geotechnical consultant prior to excavations. ^9 -30- Leigliton 042631-001 6.0 LIMITATIONS The conclusions and recommendations presented in this report are based in part upon data that were obtained from a limited number of observations, site visits, excavations, samples, and tests. Such Information is by necessity incomplete. The nature of many sites Is such that differing geotechnical or geological conditions can occur within small distances and under varying climatic conditions. Changes in subsurface conditions can and do occur over time. Therefore, the findings, conclusions, and recommendations presented In this report can be relied upon only If Leighton has the opportunity to observe the subsurface conditions during grading and construction of the project, in order to confirm that our preliminary findings are representative for the site. -31- Leigtiton FIGURES 042631-001 consultant, sound construction practices, and the General Earthwork and Grading Specifications for Rough Grading presented in Appendix C. Proposed fills placed on slopes steeper than 5 to 1 (horizontal to vertical) and repairs of the existing fill slopes should be keyed and benched into dense formational or competent fill soils (see Appendix C for benching details). Fills placed within 5 feet of finish pad grades should consist of granular soils of very low to medium expansion potential and contain no materials over 8 Inches In maximum dimension. Oversize material, if encountered, may be Incorporated into structural fills if placed in accordance with the recommendation of Appendix C. Import soils, if necessary, should consist of granular soils of very low to low expansion potential (expansion index 50) and contain no materials over 8 inches in maximum dimension. 5.1.4 Cut/Fill Transition Mitigation and Pad Overexcavation In order to reduce the potential for differential settlement in areas of transition or cut-fill building pads and to remove metavolcanic rock in cut areas, we recommend that the entire cut portion of the building pad be overexcavated to a minimum depth of 4 feet below finished grade and replaced with properly compacted fill. This depth may be increased depending on adjacent fill depth as part of the recommended removals of artificial fill beneath the building pads. The overexcavation and recompaction should laterally extend at least 5 feet beyond limits of the building footprint. Based on our review of the preliminary plans, we provided an approximate location of building pads overexcavations (Plate 1). In order to reduce the potential for excessive differential settlement under future building or retaining walls, the transition from cut to fill subgrade should be gradual. We recommend that the maximum differential fill height to not exceed 10 feet over a horizontal distance of 30 feet. The actual overexcavation limits and depth should be further evaluated prior to the grading operations based on the final design of the project and the actual building location and dimension. Also, additional over-excavation or deeper removals may be recommended during site grading based on the actual field conditions. -17- Leigtitoii 042631-001 5.2 Rock Fill Specifications We anticipate that the relatively shallow cuts on the mass graded pad that will generate oversized rock. Fill placement 1 foot below deepest utilities in roadways and within the upper 3 feet of finish grade, fill soils should not contain rock greater than 8 Inches in maximum dimension In order to facilitate foundation and utility trench excavation. For fill soils between 3 and 10 feet below finish grade, the fill may contain rock up to 12 inches in maximum dimension and should be mixed with sufficient soil to eliminate voids. Below a depth of 10 feet and at least 3 feet horizontally from the slope face, rocks up to a maximum dimension of 36 inches may be Incorporated into the fill utilizing rock blankets. A typical soil- rock fill detail is included within Appendix C. Rocks up to 5 feet in maximum dimension should be hauled offsite or utilized in nonstructural fill or landscaped area. 5.3 Temporary Excavations Sloped excavations may be utilized when adequate space allows. Based on findings, we provide the following recommendations for sloped excavations in fill soils or competent bedrock materials without seepage conditions. Table 3 Temporary Excavation Recommendations Excavation Depth Below Adjacent Surface (feet) Maximum Slope Ratio In Fill Soils Maximum Slope Ratio In Competent Bedrock Material 0to5 VA-.I (H : V) Vertical 5 to 20 1:1 1/2:1 Excavations greater than 20 feet in height will require an alternative sloping plan or shoring plan prepared by a California registered civil engineer. The above values are based on the assumption that no surcharge loading or equipment will be placed within 10 feet of the top of slope. All excavations should comply with OSHA requirements The contractor's "competent person" should review all excavations on a daily basis for signs of instability. -18- Leighton 042631-001 5.4 Surface Drainage and Erosion Surface drainage should be controlled at all times. Proposed structures should have an appropriate drainage system to collect roof runoff. Positive surface drainage should be provided to direct surface water away from structures toward the street or suitable drainage facilities. Planters should be designed with provisions for drainage to the storm drain. Ponding of water should be avoided adjacent to any structures. Regarding Low Impact Development (LID) measures, we are of the opinion that bioswales, Infiltration basins, and other onsite retention and Infiltration systems can potentially create adverse perched ground water conditions both on-site and off- site. In particular, this site is underlain by fill or formations that are known to contain both permeable and impermeable layers which can transmit and perch ground water in unpredictable ways. Therefore, given the site geologic conditions and project type, some types of LID measures may not be appropriate for this site and project. We recommend that infiltration systems are lined with a 15 mil HDPE Impermeable liner. 5.5 Foundation and Slab Considerations Foundations and slabs should be designed in accordance with structural considerations and the following recommendations. These recommendations assume that the soils encountered within 5 feet of pad grade have a medium to high expansion potential (i.e. an expansion index less than 130) for expansion and a differential fill thickness of less than 15 feet. Additional expansion testing should be performed as part of the fine grading operations. If very high expansive soils are encountered and selective grading cannot be accomplished, additional foundation design may be necessary. 5.5.1 Preliminary Foundation and Slab Design The proposed buildings may be supported by conventional, continuous or isolated spread footings. Footings should extend a minimum of 30 inches beneath the lowest adjacent soil grade. At these depths, footings may be designed for a maximum allowable bearing pressure of 2,500 pounds per square foot (psf) if founded in dense compacted fill soils. The allowable bearing pressures may also be increased by one-third when considering loads of short duration such as wind or seismic forces. The minimum -19- Leighton 042631-001 recommended width of footings is 18 inches for continuous footings and 24 Inches for square or round footings. Footings should be designed in accordance with the structural engineer's requirements. We recommend a minimum horizontal setback distance from the face of slopes for all structural footings and settlement-sensitive structures. This distance Is measured from the outside edge of the footing, horizontally to the slope face (or to the face of a retaining wall) and should be a minimum of H/2, where H is the slope height (in feet). The setback should not be less than 10 feet and need not be greater than 20 feet. Please note that the soils within the structural setback area, other than those addressed within this report, possess poor lateral stability, and improvements (such as retaining walls, sidewalks, fences, pavements, etc.) constructed within this setback area may be subject to lateral movement and/or differential settlement. Slabs on grade should be reinforced with reinforcing bars placed at slab mid-height. Slabs should have crack joints at spacings designed by the structural engineer. Columns, If any, should be structurally isolated from slabs. Slabs should be a minimum of 5 inches thick and reinforced with No. 4 rebars at 18 inches on center on center (each way). If applicable, slabs should also be designed for the anticipated traffic loading using a modulus of subgrade reaction of 100 pounds per cubic inch. All waterproofing measures should be designed by the project architect. In accordance with the current guidelines of the 2010 CALGreen Code, Section 4.505.2, post-tensioned and conventional slabs should be underlain by a vapor barrier which is in turn underlain by 4 inches of 1/2 inch gravel. The slab subgrade soils should be presoaked prior to the placement of gravel. ACI 302.2R-06 guidance recommends use of a vapor barrier with a perm rating of 0.01 or less where moisture-sensitive floor coverings are provided. The vapor barrier should possess adequate puncture resistance such that these properties are preserved when subjected to construction traffic. Placement of concrete in direct contact with the vapor barrier requires additional design and construction considerations on the part of the structural engineer, architect and contractor. Additional guidance is -20- Leighton 042631-001 provided in ACI Publications 302.1 R-04 Guide for Concrete Floor and Slab Construction and 302.2R-06 Guide for Concrete Slabs that Receive Moisture-Sensitive Floor Materials. Only an experienced concrete contractor familiar with proper construction techniques needed for constructing slabs directly on the vapor retarder/barrier should perform the work. The slab subgrade soils underlying the foundation systems should be presoaked In accordance with the recommendations presented in Table 4 prior to placement of the moisture barrier and slab concrete. The subgrade soil moisture content should be checked by a representative of Leighton prior to slab construction. Presoaking or moisture conditioning may be achieved in a number of ways. But based on our professional experience, we have found that minimizing the moisture loss on pads that has been completed (by periodic wetting to keep the upper portion of the pad from drying out) and/or berming the lot and flooding for a short period of time (days to a few weeks) are some of the more efficient ways to meet the presoaking recommendations. If flooding Is performed, a couple of days to let the upper portion of the pad dry out and form a crust so equipment can be utilized should be anticipated. Table 4 Presoaking Recommendations Based on Finish Grade Soil Expansion Potential Expansion Potential Presoaking Recommendations Very Low Near-optimum moisture content to a minimum depth of 6 inches Low 120 percent of the optimum moisture content to a minimum depth of 12 inches below slab subgrade Medium 130 percent of the optimum moisture content to a minimum depth of 24 inches below slab subgrade High 130 percent of the optimum moisture content to a minimum depth of 30 Inches below slab subgrade -21- Leighton 042631-001 5.5.2 Settlement Fill depths between 2 and 55 feet are anticipated beneath the proposed building footings following final grading. Based on this configuration, the maximum total settlement Is estimated at approximately 1 Inch with differential settlement anticipated to be approximately % to 1 inch over a horizontal distance of 100 feet. 5.5.3 Post-Tension Foundation Recommendations As an alternative to the conventional foundations for the buildings, post- tensioned foundations may be used. We recommend that post-tensioned foundations be designed using the geotechnical parameters presented in table below and criteria of the 2010 California Building Code and the Third Edition of Post-Tension Institute Manual. A post-tensioned foundation system designed and constructed in accordance with these recommendations is expected to be structurally adequate for the support of the buildings planned at the site provided our recommendations for surface drainage and landscaping are carried out and maintained through the design life of the project. Based on an evaluation of the depths of fill beneath the building pads, the attached Table 5 presents the recommended post-tension foundation category for residential buildings on subject site. -22- Leighton 042631-001 4.0 CONCLUSIONS Based on our review of the previously documented Update Geotechnical Investigation and As-Graded Geotechnical reports (SCS&T, 2012), it Is our professional opinion that the proposed development of the site is feasible from a geotechnical standpoint, provided the following conclusions and recommendations are incorporated into the design, grading, and construction of the project. Additional subsurface exploration should be performed to further characterize the bedrock beneath the site. The following is a summary of the geotechnical factors that may affect development of the site. • Based on our reference review, the documented fill and underlying formational material are dense and well compacted, excluding the upper 1 to 2 feet which appears dry and is disturbed and/or weathered. The upper 2 feet of existing fill is considered unsuitable for support of additional fill soils, structural loads or surface improvements in their present condition. Remedial grading measures such as removals, scarification and recompaction will be necessary to mitigate this condition, If not removed by the proposed grading. • Based on the review of the as-graded documents, minimum fill depths across mass- graded pad below the existing ground surface are on the order of approximately 2 feet beneath the proposed building footprints. Because site grades are being lowered a cut/fill transition will be created and additional overexcavation will be required. The pad overexcavations will encounter metavolcanic rock with oversized rock material. • Based on previous laboratory testing, the near surface soils on the site generally possess a medium to high expansion potential. Measures to mitigate expansive/swelling soils will be necessary during design and construction. Additional expansion testing should be performed after pad grading is performed. • Laboratory tests should be conducted to determine the onsite soils' potential for sulfate exposure on concrete once pad grading is performed. • The existing onsite soils appear to be suitable material for use as fill provided they are relatively free of organic material, debris, and rock fragments larger than 8 Inches in maximum dimension. Review of the as-graded report indicates that some oversized material was generated during site grading but placed below proposed foundation grades. However, in areas where proposed pad grades are lowered and -13- Leiqhton 042631-001 deep utility excavations are planned, especially outside the previous pad overexcavations (building and parking lot), oversized metavolanic rock should be anticipated. Oversize material if encountered should be placed in nonstructural areas or disposed of offsite. Ground water or seepage was not encountered during the previous site grading or investigations (SCS&T, 2012); however, perched ground water and seepage may develop during periods of precipitation. The site Is located in an area underlain by the fill and formational material that is known to contain both permeable and Impermeable layers which can transmit and perched ground water in unpredictable ways. Therefore, given the site geologic conditions, the use of some LID measures may not be appropriate for this project. -14- Leiqhton 042631-001 5.0 RECOMMENDATIONS 5.1 Earthwork We anticipate that earthwork at the site will consist of site preparation, remedial grading and placement of compacted fill. We recommend that earthwork on the site be performed in accordance with the following recommendations and the General Earthwork and Grading Specifications for Rough Grading included in Appendix C. In case of conflict, the following recommendations shall supersede those in Appendix C. 5.1.1 Site Preparation Prior to grading of areas to receive structural fill or engineered structures and improvements, the areas should be cleared of surface vegetation, any existing debris, and removal of potentially compressible material, which Includes the existing upper 1 to 2 feet of disturbed/weathered fill. Vegetation and debris should be removed and properly disposed of offsite. Holes resulting from the removal of buried obstructions, which extend below finished 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 8 inches, brought to above-optimum moisture condition, and recompacted to at least 90 percent relative compaction (based on American Standard of Testing and Materials [ASTM] Test Method D1557). A Leighton representative should observe conditions exposed in the bottom of the excavation to determine if additional removal is required. 5.1.2 Excavations and Oversize Material Based on the review of previous site reports and our site reconnaissance, it appears that the near surface fill is rippable with heavy-duty construction equipment in good working order (i.e. a single shank D9 Dozer or equivalent). However, moderately difficult ripping to very difficult ripping and localized blasting should be anticipated where Santiago Peak Volcanic Rock is mapped near the surface, in the fill areas between 2 to 5 feet below the ground surface on the central and eastern portions of the site, and where proposed pad grades are lower than existing grade. Deeper excavations into the rock is expected to be marginally rippable to 4 -15- Leighton 042631-001 unrippable, becoming progressively less fractured with Increasing depth. Heavy/very difficult to unrippable and blasting is anticipated for planned excavations below a depth of 2 feet and for localized areas within 10 feet on the ground surface. Note previous cut-graded portions of the site will likely encounter heavy/very difficult to unrippable rock significantly shallower than anticipated. Localized residual boulders of dense rock are also anticipated within otherwise rippable zones. The depth of mass- graded pad overexcavation to metavolcanic rock and at grade metavolcanic rock Is displayed on the Geotechnical Map (Plate 1). We understand that a portion of the site was overexcavated at the previous proposed building pads and parking lot area, and were generally capped with material not exceeding 6 inches in diameter. Outside the limits of the previously overexcavated parking lot and proposed building pads significant amount of rock including oversize material (i.e. rock typically over 8 inches in maximum dimension) will be generated during the grading of the site. Rocks greater than 8 inches in diameter should not be placed within fill the upper three of fill. Note that the western portion of the site (i.e. outside the limits of the previously proposed pads and parking lot overexcavation) it is unknown if the fills near pad grade was capped with material less 6 inches in diameter. Excavations in western portion of the site should anticipate oversized rock material. All oversized rock that is encountered should be placed as fill in accordance with the recommendations in section 5.2 or hauled off site for disposal. 5.1.3 Fill Placement The onsite soils are generally suitable for reuse as compacted fill, provided they are free of organic materials and debris. Areas to receive structural fill and/or other surface improvements should be scarified to a minimum depth of 8 inches; brought to at least 3 percent above optimum moisture content; and recompacted to at least 90 percent relative compaction (based on ASTM Test Method D1557). The optimum lift thickness to produce a uniformly compacted fill will depend on the type and size of compaction equipment used. In general, fill should be placed in uniform lifts not exceeding 8 inches In thickness. Placement and compaction of fill should be performed In general accordance with the current City of Carlsbad grading ordinances under the observation and testing of the geotechnical -16- Leighton 042631-001 2.2.2 Artificial Fill - Documented (Af) Artificial fill placed during the previous site mass grading is anticipated to be present throughout the entire site. The documented fill generally consist of reddish-brown to brown, medium dense to dense, moist, silty sands with clays, gravel, and cobble. The estimated depth of fill beneath the existing site grades ranges from approximately 1.5 to 55 feet below the existing surface grades. These artificial fills are expected to be suitable to support the proposed residential development; although minor reconditioning and/or removal of loose desiccated surficial soils may be necessary. We have provided density tests and laboratory testing (SCS&T, 2012) In Appendix B. 2.2.3 Santiago Peak Volcanics (Jsp) Santiago Peak metavolcanic rock outcrops were observed across the eastern portion of the site and underlie the entire site. The rock generally consisted of light gray-olive brown to reddish brown, damp, highly fractured, moderately to highly weathered metavolcanic rock. Where observed, the metavolcanic rock becomes fresh bedrock is anticipated within 2 feet to 10 feet of the surface. Excavations and cuts (greater than ±2 feet at the east end of the site will likely require very heavy ripping and/or blasting and will likely generate some oversized materials. Fresh rock zones may also be encountered at shallower depths. Additional subsurface exploration is recommended to further evaluate depth bedrock beneath the site. 2.3 Geologic Structure Based on our review of the as-graded geotechnical report, and regional geologic maps, the Jurassic-aged Santiago Peak Volcanics have a regional northwesterly foliation/fracturing trend in the metavolcanic rock bedding and generally flat bedding where present. Jointing was generally oriented parallel to previous existing slopes with steep to moderate dip. -6- Leightofl: 042631-001 2.4 Surface and Ground Water No indication of surface water or evidence of surface ponding was encountered during our review. However, surface water may drain as sheet flow In the higher portions of the site during rainy periods and sheet across the lower portions of the site. Ground water was not reported during the original mass grading. Ground water levels are anticipated to be relatively deep; however, perched ground water conditions may develop following site development at contact areas of artificial fill and the underlying bedrock. Ground water Is not expected to Impact the proposed development. 2.5 Landslides No ancient landslides were identified beneath or adjacent to the site. In addition, no evidence of landsliding was documented during mass grading of the site. The potential for significant landslides or large-scale slope instability at the site Is considered low. 2.6 Flood Hazard According to a Federal Emergency Management Agency (FEMA) flood insurance rate map (FEMA, 1997); the site is not located within a flood zone. Based on review of dam inundation and topographic maps per SANGIS, the site is not located downstream from dam inundation areas. 2.7 Engineering Characteristics of the On-Site Soils Based on our review of previous site reports laboratory testing of representative on-site soils and our professional experience on near-by sites with similar soils, the engineering characteristics of the on-site soils are discussed below. 2.7.1 Expansion Potential The majority of the onsite soils are expected to have a medium to high expansion potential. The expansion index tests performed after site grading ranged from 54 to 91 (SCS&T, 2012). Previous expansion index testing is provided in Appendix B. Geotechnical observation and/or laboratory testing 4 -7- Leighton 042631-001 upon completion of the anticipated fine grading operations are recommended to determine the actual expansion potential of finish grade soils on the site. 2.7.2 Earthwork Shrinkage and Bulking Based on our professional experience with similar projects In the general vicinity of the site, we have estimated bulking and shrinkage of the on-site soils. The volume change of excavated on-site materials upon recompaction as fill is expected to vary with materials and location. Typically, the surficial soils and bedrock materials vary significantly in natural and compacted density, and therefore, accurate earthwork shrinkage/bulking estimates cannot be determined. However, the following factors (based on professional experience on nearby sites) are provided on Table 1 as guideline estimates. If possible, we suggest an area where site grades can be adjusted (during the later portion of the site grading operations) be provided as a balance area. Table 1 Earthwork Shrinkage and Bulking Estimates Geologic Unit Estimated Shrinkage/Bulking Documented and Existing Fills 0 to 3 percent shrinkage Metavolcanic Rock (highly weathered) 0 to 10 percent bulking Metavolcanic Rock (less-weathered) 5 to 15 percent bulking Excavation Characteristics It is anticipated the onsite fill soils can be excavated with conventional heavy-duty construction equipment. However, excavations deeper than 5 feet, especially in the eastern portion of the site, is expected to be marginally to nonippable in some area or will need to be blasted prior to excavation. Note that based on the current grading plans and review of the existing or previously pad overexcavation limits, portions of the site will require additional overexcavation of rock to depths of at least 4 feet below finish grade. Note that the overexcavation will be within metavolcanic rock and Leighton 042631-001 may require heavy ripping or blasting. The approximate limits of anticipated metavolcanic rock overexcavation is depicted on Geotechnical Map (Plate 1). Also note that large rock may be generated during overexcavation and the rock may have to be hauled off site or burled in deep fill areas on the site. Additional subsurface exploration should be performed to further characterize the bedrock. 2.7.4 Oversize Material Numerous exposures of jointed metavolcanic bedrock occur across the site. On average the jointed rock Is anticipated to yield approximately one foot diameter blocks with a potential for larger boulders. Based on our professional experience with projects in similar geologic conditions, it Is likely that oversized rock will be generated during grading. Recommendations have been provided for appropriate handling of oversized materials. 4 -9- Leigiiton 042631-001 3.0 FAULTING AND SEISMICITY 3.1 Faulting Our discussion of faults on the site is prefaced with a discussion of California legislation and state policies concerning the classification and land-use criteria associated with faults. By definition of the California Mining and Geology Board, an active fault is a fault which has had surface displacement within Holocene time (about the last 11,000 years). The state geologist has defined a potentialIv active fault as any fault considered to have been active during Quaternary time (last 1,600,000 years). This definition Is used In delineating Earthquake Fault Zones as mandated by the Alquist-Priolo Earthquake Faulting Zones Act of 1972 and as most recently revised in 2007 (Hart and Bryant, 2007). The intent of this act is to assure that unwise urban development and certain habitable structures do not occur across the traces of active faults. Based on our review, the site is not located within any Earthquake Fault Zone (EFZ) as created by the Alquist-Priolo Act. A review of available geologic literature pertaining to the subject site indicates that there are no known active regional faults that transect the subject site. The nearest known active regional fault is the Rose Canyon Fault Zone located approximately 7.1 miles west of the site. 3.2 Seismicity The principal seismic considerations for most structures in southern California are surface rupturing of fault traces and damage caused by strong ground shaking or selsmlcally induced ground settlement. Historically, the San Diego region has been spared major destructive earthquakes. The site is considered to lie within a selsmlcally active region, as can all of Southern California. The effect of seismic shaking may be mitigated by adhering to the California Building Code (see Section 3.2.6 of this report for CBC seismic parameters) or state-of-the-art seismic design parameters of the Structural Engineers Association of California. Secondary effects associated with severe ground shaking following a relatively large earthquake can include shallow ground rupture, soil liquefaction, lateral spreading, earthquake-induced settlement, and tsunamis/seiches. These secondary effects of seismic shaking are discussed in the following sections. -10- Leighton 042631-001 3.2.1 Shallow Ground Rupture No active faults are mapped crossing the site. The nearest known active fault is the Rose Canyon 7.1 miles west of the site. Due to absence of known active faults, cracking due to shaking of a seismic event is not considered a significant hazard, although it Is possible at any site. 3.2.2 LIguefaction Liquefaction and dynamic settlement of soils can be caused by strong vibratory motion due to earthquakes. Both research and historical data Indicate that loose, saturated, granular soils are susceptible to liquefaction and dynamic settlement. Liquefaction is typified by a total loss of shear strength in the affected soil layer, thereby causing the soil to flow as a liquid. This effect may be manifested by excessive settlements and sand boils at the ground surface. The unsaturated artificial fill and formational materials that underlie the site are not considered liquefiable due to their dense physical characteristics and lack of ground water. 3.2.3 Earthguake-lnduced Settlement Granular soils tend to densify when subjected to shear strains induced by ground shaking during earthquakes. Simplified methods were proposed by Tokimatsu and Seed (1987) and Ishlhara and Yoshimine (1992) involving SPT N-values to estimate earthquake-induced soil settlement. However, since liquefaction at the site is considered low, there is relatively no potential for earthquake-induced settlements. 3.2.4 Lateral Spread Empirical relationships have been derived by Youd and others (Youd, 1993; Bartlett and Youd, 1995; and Youd et. al., 1999) to estimate the magnitude of lateral spread due to liquefaction. These relationships include parameters such as earthquake magnitude, distance of the earthquake from the site, slope height and angle, the thickness of liquefiable soil, and gradation characteristics of the soil. 4 -11- Leighton 042631-001 Since there is relative no potential for liquefaction at the site, there Is no susceptibility to earthquake-induced lateral spread. 3.2.5 Tsunamis and Seiches Based on the distance between the site and large, open bodies of water, barriers between the site and the open ocean, and the elevation of the site with respect to sea level, the possibility of seiches and/or tsunamis is considered to be nil. 3.2.6 Building Code Seismic Parameters The following geotechnical design parameters have been determined in accordance with the 2010 CBC (CBSC, 2010) and the USGS Ground Motion Parameter Calculator (Version 5.10). Table 2 CBC Seismic Design Parameters Description Values CBC Reference Site Class D Table 1613.5.2 Short Period Spectral Acceleration Ss 1.118 Figure 1613.5(3) 1-Second Period Spectral Acceleration Si 0.420 Figure 1613.5(4) Short Period Site Coefficient Fa 1.053 Table 1613.5.3(1) 1-Second Period Site Coefficient Fv 1.58 Table 1613.5.3(2) Adjusted Short Period Spectral Acceleration SMS 1.177 Equation 16-36 Adjusted 1-Second Period Acceleration SMI 0.663 Equation 16-37 Design Short Period Spectral Response Parameter SDS 0.785 Equation 16-38 Design 1-Second Period Spectral Response Parameter SDI 0.442 Equation 16-39 -12- Leiqhton hllCAL UPDATE INVESTIGATION, >ED LA COSTA TOWN CENTER RcolDENTIAL DEVELOPMENT CARLSBAD, CALIFORNIA Prepared For: TAYLOR MORRISON OF CA, LLC 8105 Irvine Center Drive, Suite 1450 Irvine, California 92618 Project No. 042631-001 September 27, 2012 4 Leighton and Associates, Inc. A LEIGHTON GROUP COMPANY Leighton and Associates, Inc. A LEIGHTON GROUP COMPANY September 27, 2012 Project No. 042631-001 Taylor Morrison of CA, LLC 8105 Irvine Center Drive, Suite 1450 Irvine, California 92618 Attention: Ms. April Tornillo Subject: Geotechnical Update Investigation Proposed La Costa Town Center Residential Development Carlsbad, California In accordance with your request and authorization, we have conducted a review of pertinent documentation (SCS&T, 2012) and have prepared this geotechnical update investigation for a proposed La Costa Town Center residential development to be built north of Rancho Santa Fe Road, south of Old Rancho Santa Fe Road, and west of Paseo Lupino in Carlsbad, California. Based on the results of our review, it is our professional opinion that the site is suitable for the proposed residential development provided that the recommendations presented herein are incorporated into the design, grading, and construction of the site. The accompanying report presents a summary of our investigation and provides preliminary geotechnical conclusions and recommendations relative to the proposed site development Note that additional site exploration is recommended to further evaluate depth and characteristics of bedrocic beneath the site. If you have any questions regarding our report, please do not hesitate to contact this office. We appreciate this opportunity to be of service. Respectfully submitted, LEIGHTON AND ASSOCIATE Mike D. Jensen, CEG 24 Project Geologist Distribution: (3) Addressee William D. Olson, RCE 45283 Associate Engineer 3934 Murphy Canyon Road, Suite B205 • San Diego, CA 92123-4425 858.292.8030 « Fax 858.292.0771 • www.leightongroup.com 042631-001 TABLE OF CONTENTS Section Page 1.0 INTRODUCTION 1 1.1 PURPOSE AND SCOPE 1 1.1.1 Scope of Work 1 1.2 SITE LOCATION AND DESCRIPTION 2 1.3 PREVIOUS SITE DEVELOPMENT AND SITE GRADING 2 1.4 PROPOSED DEVELOPMENT 3 1.5 PREVIOUS LABORATORY TESTING 4 2.0 SUMMARY OF GEOTECHNICAL CONDITIONS 5 2.1 GEOLOGIC SETTING 5 2.2 SITE-SPECIFIC GEOLOGY 5 2.2.1 Artificial Fill - Previously Existing (Afo) 5 2.2.2 Artificial Fill - Documented (Af) 6 2.2.3 Santiago Peak Volcanics (Jsp) 6 2.3 GEOLOGIC STRUCTURE 6 2.4 SURFACE AND GROUND WATER 7 2.5 LANDSLIDES 7 2.6 FLOOD HAZARD 7 2.7 ENGINEERING CHARACTERISTICS OF THE ON-SITE SOILS 7 2.7.1 Expansion Potential 7 2.7.2 Earthwork Shrinkage and Bulking 8 2.7.3 Excavation Characteristics 8 2.7.4 Oversize Material 9 3.0 FAULTING AND SEISMICITY 10 3.1 FAULTING 10 3.2 SEISMICITY 10 3.2.1 Shallow Ground Rupture 11 3.2.2 Liquefaction 11 3.2.3 Earthquake-Induced Settlement 11 3.2.4 Lateral Spread 11 3.2.5 Tsunamis and Seiches 12 3.2.6 Building Code Seismic Parameters 12 4.0 CONCLUSIONS 13 5.0 RECOMMENDATIONS 15 5.1 EARTHWORK 15 5.1.1 Site Preparation 15 5.1.2 Excavations and Oversize Material 15 Leiqhton 042631-001 1.0 INTRODUCTION 1.1 Purpose and Scope This report presents the results of our geotechnical update investigation for a proposed residential development to be constructed on the existing sheet graded parcel that is north of Rancho Santa Fe Road, south of Old Rancho Santa Fe Road, and west of Paseo Lupino in Carlsbad, California, (see Figure 1). Our investigation included a review of a previously Update Geotechnical Investigation and the As-Graded Geotechnical reports (SCS&T, 2012), and preparation of this report. The purpose of our geotechnical update investigation was to evaluate existing geotechnical conditions present at the site and to provide preliminary conclusions and geotechnical recommendations relative to the proposed residential development of the property. 1.1.1 Scope of Work As part of our geotechnical update, we performed the following: • Review of available pertinent, published and unpublished geotechnical literature maps, and aerial photographs (Appendix A). • Review of the available previous geotechnical reports by others and conceptual site development plans (SCS&T, 2012; Latitude 33, 2012). • Field reconnaissance of the existing onsite geotechnical conditions. • Review local and regional seismicity, and provide seismic parameters for the site in accordance with 2010 California Building Code (CBC). • An updated geotechnical map and geologic cross-section. • Preparation of this report presenting our findings, conclusions, and geotechnical recommendations with respect to the proposed design, site grading and general construction considerations. 4 -1- LeiqlitDii 042631-001 1.2 Site Location and Description The proposed project is located north of Rancho Santa Fe Road, southeast of Old Rancho Santa Fe Road, and west of Paseo Lupino in Carlsbad, California. As background this parcel, was previously mass-graded pad (SCS&T, 2012), and has minor surface improvements consisting of a shallow concrete lined drainage ditches, a desilting basin, and landscaping of perimeter slopes extending down Old Rancho Santa Fe Road, Rancho Santa Fe Road, and along Paseo Lupino. The topography of the area is gently sloping with elevations ranging from approximately 380 feet mean sea level (msl) in the north corner to approximately 380 feet msl in the southeast corner and approximately 367 feet msl in the southwestern corner. Vegetation at the site consists of native grasses and weeds. Descending 2:1 fill slope, a fill over cut slope, a cut a slope all that borders the majority of the site except along a segment along Old Rancho Santa Fe Road in the northeastern section of the site. Latitude: 33.0839 degrees Longitude: -117.2339 degrees 1.3 Previous Site Development and Site Grading As background, the site was rough graded in 2004 by Erreca's for Lusardi Construction. The grading was observed and tested by Southern California Soil & Testing (SCS&T, 2012). In general, grading consisted of installing keyways at the toe of several fill slopes, creation of cut and fill slopes, installation of a subrain trench backfill. Specifically, the grading consisted of excavating (i.e., cutting) the eastern portion of the site and placement of fill in the western portion of the site. Up to approximately 55 feet of fill was placed in the western portion of the site, while cut excavations extended up to approximately 31 feet below the previous existing grade at the eastern portion of the site. An overexcavation of the previously proposed building pads and parking area cut portion was performed into the underlying metavolcanic and replaced with capping fill material of less than 6 inches in diameter. Previously proposed building pads were overexcavated 2 to 7 feet below ground surface (bgs) and previously proposed parking areas were overexcavated to a minimum of 10 feet bgs and replaced with documented fill. Remedial grading consisted of removal of topsoil, alluvium, and existing fill to depth up to 25 feet below previous existing grades. In the southwest portion of the site, previous existing fills that were associated with -2- Leiqhton 042631-001 grading and construction of Rancho Santa Fe Road were left-in-place. We have provided a geotechnical map (Plate 1) with approximate remedial grading and overexcavation elevations and limits of fill across the site. Note that blasting of the underlying formational bedrock was required in the eastern portion of the site. The resulting material, containing rock fragments of up to 2 feet in diameter was then moisture conditioned and placed as fill. Fills placed within the upper 5 feet of previously proposed building pads and the upper 10 feet of previously proposed parking areas consisted of select capping material, comprised primarily of silty sand and sandy silt with variable clay and rock fragments generally no larger than 6 inches in diameter. Similar fill materials were used as compacted fill within the outermost 6 feet of fill slopes. This select capping material was derived from on-site non-organic topsoil and alluvial deposits, and some borrowed material from off-site sources. Excavations extending to metavolcanic rock were not scarified due to the nature of the exposed material. Excavated soils, cuts, and imported fill were placed as uniformly compacted fill material. The soils to be placed were moisture conditioned and compacted to a minimum of 90 percent relative compaction. 1.4 Proposed Development Based on our review of the conceptual site development plans (Latitude 33, 2012), we understand the proposed development will include construction of thirty-two single-family residential buildings and associated improvements including roadways, building patios, driveways, parking areas, concrete flatwork, underground utilities, landscaping, etc. We also understand that the proposed buildings will be two story structures and will likely be constructed with conventional or post-tension foundations. Based on the preliminary development plans, we anticipate the proposed finish grade elevations will be within a 1 to 4 feet of the existing mass-graded pad elevations. Leialiton 042631-001 1.5 Previous Laboratory Testing Laboratory testing was performed during the previous site grading to evaluate maximum density and expansion Index characteristics of the subsurface soils. The previous laboratory tests performed by Southern California Soil & Testing (SCS&T, 2012) are presented in Appendix B. -4- Leighton 042631-001 2.0 SUMMARY OF GEOTECHNICAL CONDITIONS 2.1 Geologic Setting The subject site is located In the coastal section of the Peninsular Range Province, a geomorphic province with a long and active geologic history throughout Southern California. Throughout the last 54 million years, the area known as the "San Diego Embayment" has undergone several episodes of marine Inundation and subsequent marine regression, resulting in the deposition of a thick sequence of marine and nonmarine sedimentary rocks on the basement rock of the Southern California bathollth. Gradual emergence of the region from the sea occurred in Pleistocene time, and numerous wave-cut platforms, most of which were covered by relatively thin marine and nonmarine terrace deposits, formed as the sea receded from the land. Accelerated fluvial erosion during periods of heavy rainfall, coupled with the lowering of the base sea level during Quaternary time, resulted in the rolling hills, mesas, and deeply incised canyons which characterize the landforms we see In the general site area today. 2.2 Site-Specific Geology Based on our review of the previous site geotechnical documents, a site reconnaissance, and review of pertinent geologic literature and maps, the site Is generally underlain by documented artificial fill soils and the Jurassic-aged Santiago Peak Volcanics. A brief description of the geologic units at the site are presented below. 2.2.1 Artificial Fill - Previouslv Existino (Afo) Artificial fill placed during the previous grading operations along Rancho Santa Fe Road. This fill is present below the fill slopes at the western end of the site. As described, this fill generally consists of reddish-brown to brown, medium dense to dense, moist, silty sands with clays, gravel, and cobble. The estimated depth of fill beneath the existing slope faces should be no greater than 10 feet below the adjacent roadway surface. These artificial fills are expected to be suitable to support the proposed residential development. Leighton 042631-001 TABLE OF CONTENTS (Continued) Section Page 5.1.3 Fill Placement 16 5.1.4 Cut/Fill Transition Mitigation and Pad Overexcavation 17 5.2 ROCK FILL SPECIFICATIONS 18 5.3 TEMPORARY EXCAVATIONS 18 5.4 SURFACE DRAINAGE AND EROSION 19 5.5 FOUNDATION AND SLAB CONSIDERATIONS 19 5.5.1 Preliminary Foundation and Slab Design 19 5.5.2 Settlement 22 5.5.3 Post-Tension Foundation Recommendations 22 5.6 RETAINING WALL DESIGN AND LATERAL EARTH PRESSURE 24 5.7 PRELIMINARY PAVEMENT DESIGN 25 5.8 SLOPE STABILITY 27 5.9 CONCRETE FLATWORK 27 5.10 SLOPE MAINTENANCE GUIDELINES 27 5.11 LANDSCAPING AND POST-CONSTRUCTION 28 5.12 FUTURE INVESTIGATION 29 5.13 CONSTRUCTION OBSERVATION AND TESTING AND PLAN REVIEW 30 6.0 LIMITATIONS 31 TABLES TABLE 1 - EARTHWORK SHRINKAGE AND BULKING ESTIMATES - PAGE 7 TABLE 2 - CBC SEISMIC DESIGN PARAMETERS - PAGE 11 TABLE 3 - TEMPORARY EXCAVATION RECOMMENDATIONS - PAGE 17 TABLE 4 - PRESOAKING RECOMMENDATIONS BASED ON FINISH GRADE SOIL EXPANSION POTENTIAL - PAGE 20 TABLE 5 - POST-TENSIONED FOUNDATION DESIGN RECOMMENDATIONS - PAGE 22 TABLE 6 - STATIC EQUIVALENT FLUID WEIGHT (PCF) - PAGE 23 TABLE 7 - PRELIMINARY PAVEMENT SECTION DESIGNS - PAGE - 25 TABLE 8 - PRELIMINARY CONCRETE PAVEMENT DESIGN - PAGE - 26 FIGURE FIGURE 1 - SITE LOCATION MAP - REAR OF TEXT Leighton 042631-001 TABLE OF CONTENTS (Continued) PLATE Plate 1 - Geotechnical Map - In Pocket Plate 2 - Geologic Cross Section - In Pocket APPENDICES APPENDIX A - REFERENCES APPENDIX B - LABORATORY TESTING AND DENSITY TESTING BY OTHERS APPENDIX C - GENERAL EARTHWORK AND GRADING SPECIFICATIONS Leighton LEGEND Af Afo Jsp APPROXIWE LIMITS OF KEYWAY APPROXIMATE LOCATION OF RECOMMENDED 9UILDING PAD OVEREXCAVATION DUE TO TRANSmON CONDITIONS AND METAVOLCANIC ROOK GEOLOGIC CROSS-SECTION APPROXIMATE GEOLOGIC CONTACT APPROXIMATE REMOVAL BOTTOM ELEVATION COMPACTED nLL FROM PflEWOUS GRADING {SCS&T, 2012) PRE-EXISTING FILL SANTIAGO PEAK VOLCANICS (CIRCl£D WHERE BURLED) ^.,.T OF PREWOUS BUILDING PAD AND PARKING LOT OVEREXCAVATION (SCS&T. 2012) x_ Af / C^'™ • \\"\(^ Af Afo " Af Afo - — '[SE \^ Jsp Jsp WMCmO SANTA f^ROAD GEOTECHNICAL MAP LA COSTA TOWN CENTER CARLSBAD. C Proj: 042631-001 Eng/Geol: WDO/MDJ Scale: r=40' Dale; 11/2012 Approximate Limit of Propos*d Ovsrixcavotlon dua to metavolcanic Proposed Grodo A" T ^Approxlmota Limit of Proposed Oversxcovotion due to motovolconlc rock 380 LEGEND APPROXIWATE GEOLOGIC CONTACT Af COMPACTED FILL FROM PREVIOUS GRADING (SCS4T. 2012) Afo PRE-EXISTING FILL Jsp SANTIAGO PEAK VOLCANICS (CIRCLED WHERE BURIED) CROSS-SECTION A-A' LA COSTA TOWN OENTER CARLSBAD. CALIFORNIA PTOJ: 042631-001 Scale: 1"=40' Eng/Geol: WDO/MDJ Date: 11/2012