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HomeMy WebLinkAboutCDP 00-50; Preliminary Investigation - Quirk Residence; Preliminary Investigation - Quirk Residence; 2000-09-21American Geotechnical Protecting Your Future PRELIMINARY INVESTIGATION Quirk Residence 3075 Ocean Street Carlsbad, California File No. 22366.01R September 21, 2000 22725 Old Canal Road, Yorba Linda, CA 92887 (714) 685-3900 (800) 275-4436 FAX (714) 685-3909 5764 Pacific Center Boulevard, Suite 112, San Diego, CA 92121 (858) 450-4040 FAX (858) 457-0814 American Geotechnical Protecting Your Future September 21,2000 File No. 22366.01R Mr. Luis Quintanar THORYK ARCHITECTURE 1235 Shafter Street San Diego, California 92106 Subject: PRELIMINARY INVESTIGATION Quirk Residence 3075 Ocean Street Carlsbad, California Dear Mr. Quintanar: As requested, American Geotechnical has prepared the following report presenting the findings of our geotechnical investigation at the subject project. The purpose of the investigation was to evaluate the geotechnical conditions at the site and provide recommendations for the proposed construction. Results of the investigation indicate that the proposed construction is feasible from a geotechnical standpoint provided the recommendations contained herein are incorporated into the project plans and specifications. Specific recommendations for foundation design for the proposed improvements are presented in the following text. The geotechnical report should be reviewed in detail prior to proceeding further with the planned construction. When plans become available, they should be forwarded to this office for review and comment. We appreciate the opportunity to be of service. If you should have any questions or require additional services, please contact this office. Sincerely, AMERICAN GEOTECHNICAL Richard K. Walsh Senior Engineer G.E. 2498 Reviewed by: Todd M. Page Senior Geologist C.E.G. 2083 Edred T. Marsh Chief Geotechnical Engineer G.E. 2387 RKW/TMP/ETM:kr Distribution: Mr. Luis Quintanar - (2) Via Fax & Mail 22725 Old Canal Road, Yorba Linda, CA 92887 (714) 685-3900 (800) 275-4436 FAX (714) 685-3909 5764 Pacific Center Boulevard, Suite 112, San Diego, CA 92121 (858) 450-4040 FAX (858) 457-0814 File NO. 22366.01 BB American Geotechnical September 21,2000 Page 1 1.0 INTRODUCTION 1.1 PURPOSE The following text presents the results of our investigation for the proposed residence at 3075 Ocean Street in Carlsbad, California. The purpose of the investigation was to obtain engineering and geologic information to estimate subsurface conditions and provide soil design parameters and foundation recommendations for construction of the proposed improvements. 1.2 PROPOSED CONSTRUCTION Based on conversations with the project architect, it is our understanding that the proposed construction at the site will include demolishing the existing residence and constructing a new residence in its place. The new residence will encompass the existing footprint as well as extending approximately 11 to 14 feet further out to the rear. Based upon our understanding of the proposed construction and our investigation it appears that minimal grading will be needed to construct the proposed improvements. In areas where loose near-surface material is present, some remedial grading may be needed depending on the type of foundation system selected. Any grading conducted will likely be limited to removing any loose near-surface soil in the area of construction and replacing it as properly compacted fill. Additionally, grading may be necessary to remove and recompact material disturbed during the demolition process. Recommendations for any site grading to be conducted are included in later sections of this report. When additional plans become available, they should be forwarded to this office for review and comment. 1.3 SCOPE OF SERVICES The scope of services performed during our investigation primarily included the following: • Review of available literature and maps pertaining to geotechnical conditions at the site and surrounding area. References utilized are presented in Appendix A. • Excavation of two test pits including logging and soil sampling. The locations of the test excavations are presented on Figure 1 and the logs of the test excavations are presented in Appendix B. • Laboratory testing of collected soil samples collected from the test excavations to estimate engineering properties of the site soil. Results of the laboratory testing are presented in Appendix C. • Engineering and geologic analysis to develop geotechnical recommendations and design parameters. • Preparation of this report including conclusions and recommendations for the proposed construction. Legend AGTP-2 • Approximate location of test pit American Geotechnical Subsurface Location Plan Quirk Residence F.N. 22366.01 September 2000 FIGURE 1 File NO. 22366.01 Hi American Geotechnical September 21,2000 Page 2 2.0 SITE DESCRIPTION The subject site consists of a rectangular shaped lot. The lot lies along the coastline of the Pacific Ocean. The property is located to the southwest of the southern end of Ocean Street in Carlsbad, California. The lot is bordered by Ocean Street to the northeast, by similar residential properties to the northwest and southeast and by the Pacific Ocean to the southwest. Existing improvements on the lot include a single family home with attached garages which has been sub-divided and is currently being utilized as numerous vacation rental properties. Other improvements on the lot primarily include concrete patios and walkways. The foundation for the exiting residence appears to primarily include a slab-on-grade with continuous footings in the front with a small portion of the residence possibly being a raised wood floor foundation with a subfloor crawlspace. The residence appears to be of typical wood-frame construction. It was not determined as part of this investigation when the residence was originally constructed. The lot's topography is gently sloping down from the front to back (northeastern to southwestern) direction. It is estimated that the total relief across the lot is on the order of 20 to 25 feet. It appears that little grading took place during construction of the existing improvements. The general configuration of the site is presented on Figure 1. File NO. 22366.01 HI American Geotechnkal September 21,2000 PageS 3.0 GEOLOGY 3.1 GEOLOGIC SETTING The property is located geomorphically within the Peninsular Range Province. The Peninsular Ranges extend north to the Los Angeles Basin and south to the tip of the Baja Peninsula. The Peninsular Ranges consist of a series of northwest to the southeast trending blocks separated by paralleling faults. Topographic relief reaches a maximum of 10,000 feet at San Jacinto Peak. Rock units ranging from Paleozoic to Quaternary in age can be found in the province. Extensive Cretaceous rocks give way to post-cretaceous marine, and non-marine, and volcanic deposits near the coastline. Within the province, drainage is provided by the San Diego, San Luis Rey, Santa Margarita, and San Diequito Rivers. Local topography is characterized by the gently west sloping terrain consisting of shoreline deposits giving way to more elevated and more resistant Quaternary terrace deposits and Tertiary near shore and lagoonal deposits to the east. 3.2 SITE SPECIFIC GEOLOGY The site is situated at the coastal section of northern San Diego County, just south of Buena Vista Lagoon. The site is specifically located on the beach and adjacent shoreline bluff in Carlsbad at the west terminus of Carlsbad Village Drive. The west portion of the lot consists of a relatively flat sandy beach and the east portion of the lot, containing the four (4) unit rental property, is an elevated bluff consisting of young terrace deposits. The local area supports lithologies ranging from Tertiary, near shore to lagoonal, transgressive and regressive sequences to Recent Artificial Fill and Holocene Beach deposits. According to F. Harold Weber (1982), the site is underlain by Quaternary shoreline deposits. Holocene Beach deposits are found on the west portion of the property and Pleistocene Terrace Deposits are found to the east of the bluff. The Pleistocene Terrace Deposits are characterized as a light brown to orange, medium to coarse grained, massive to thinly laminated, poorly cemented sandstone deposit with occasional beach sand interbeds. The Quaternary terrace deposits transgress rapidly into Holocene Beach Deposits approximately at the east edge of the rear (lower) patio. The Beach Deposits consist primarily of sand, with minor amounts of silt and clay and occasional shell fragments. Shallow fill soils were found to consist primarily of silty sand and ranged from loose to moderately dense. Structurally, the site is resting on a generally stable, gently southwest dipping shoreline platform. A secondary terrace deposit of slightly older age creates a ridge just east of 1-5. No mapped landslides exist within the immediate area of the site. The site is mapped by Tan and Giffen(1995) as being within Zone 4.1, which is defined as an area "most susceptible" to landsliding. Coastal bluff erosion and urban runoff can create unstable slopes in an active shoreline environment. The structure has been in-place for many years, providing an indication of relatively stable slope conditions, however, periods of high tides and strong winter storms can rapidly change coastal geography. During our investigation, no signs of slope instability were observed at the site. File NO. 22366.01 Bi American Gcotechniciil September 21, 2000 Page 4 3.3 GROUNDWATER Groundwater was encountered at a depth of approximately 12 feet in the western most of our excavations. This groundwater should not be a factor in the development proposed. However, groundwater may be a factor in the construction of any deep foundation system and should be considered by the contractor when selecting the method of construction. It should also be noted that surface or shallow perched groundwater conditions can and may develop where no such conditions existed previously. This can occur due to changes made to the natural drainage patterns during development, increased irrigation, heavy rainfall and/or other reasons. Because the introduction of water is usually the triggering mechanism for most common types of soil problems, it is important to provide adequate surface drainage for proposed improvement such as retaining walls, foundations and slab areas and other improvements that could be adversely affected by water. Recommendations for drainage are provided in section 7.6. 3.4 GEOLOGIC HAZARDS Several geologic hazards have been known to exist along the Southern California coastline. These hazards generally consist of landsliding, the possibility of tsunamis immediately along the coastline and ground shaking due to earthquakes. Landsliding is not considered to be a factor in the proposed development and the possibility for occurrence after construction is considered negligible because of the relatively competent materials underlying the site. Given the close proximity of this site to the coastline a tsunami could impact the site if one were to occur. Finally, the presence of beach sand and groundwater in the western portion of the lot indicates this area would likely be susceptible to liquefaction should an earthquake occur. The most likely geologic hazard to affect the site would be ground shaking in the event of an earthquake. The nearest active fault to the site is the Rose Canyon Fault Zone. The fault is found to extend from Downtown San Diego in a north direction, roughly paralleling 1-5, until the fault bends westward through La Jolla before heading offshore and continuing north up the coastline. The offshore segment of the Rose Canyon is approximately 2.5 miles west of the site. The maximum probable magnitude earthquake estimated for the Rose Canyon fault is a (M) 6.0. Additionally, the site lies approximately 1.75 miles northwest of a small unnamed fault segment exposed on the north side of Agua Hedionda Lagoon. If a significant earthquake were to occur near the site, considerable ground shaking could occur. Comparatively, any residence within Southern California, in close proximity to a significant earthquake event, could be expected to experience seismic induced damage. The following table illustrates the characteristics of ground shaking estimated for the site from various nearby faults using an attenuation relationship provided by Campbell generated by EQFAULT 2.0 (Blake 1988-1993): Table 1: Selected Faults Fault Name Rose Canyon Newport-Inglewood-Offshore Palos Verdes-Coronado Banks Elsinore La Nacion San Diego Trgh-Bahia Sol Catalina Escarpment Whittier-North Elsinore Chino Caca Loma Clark (San Jacinto) Glen Helen-Lytle Approximate -. Distance (miles) 2.5 7 20 25 25 30 35 44 46 48 50 Maximum Probable Magnitude 6.00 5.75 6.75 6.75 4.25 6.25 6.25 6.00 5.50 6.75 6.50 Peak Site Acceleration (g) 0.31 0.15 0.10 0.08 0.02 0.04 0.03 0.02 0.02 0.03 0.02 File NO. 22366.01 M American Geotechnkai September 21,2000 PageS 3.5 SEISMICITY AND SEISMIC RISK Our historical search indicates that approximately 114 events have occurred within a 50 mile radius of the site with magnitudes (M) between 4.0 and 9.0, within the last 100 years. The largest event recorded within that time frame was a (M) 6.8 earthquake, approximately 46 miles from the site, which produced a site acceleration of about 0.03g. Even if the structural engineer provides designs in accordance with applicable codes for seismic design, the possibility of damage occurring cannot be ruled out in the event of a large earthquake near the site. This is the case for essentially all homes in Southern California. The structures should be designed in accordance with the latest UBC criteria for seismic design. The site area should be categorized as a Seismic Zone 4. File NO. 22366.01 •§ American Geotechnical September 21,2000 Page 6 4.0 SUBSURFACE EXPLORATION The subsurface exploration consisted of two hand-excavated test pits. The approximate locations of the excavations are depicted on Figure 1. The purpose of the excavations was to delineate the subsurface conditions in the area of the proposed improvements. All excavations were logged by a geologist from our firm who also obtained soil samples for laboratory testing. Additionally, each excavation was backfilled upon completion. The test excavations revealed variable subsurface conditions. AGTP-1 revealed fine to coarse grained beach sands. Variable moisture was also encountered with depth and the sands were found to become dense with depth. Water was encountered in this excavation at a depth of approximately 12 feet. In AGTP-2 approximately 2.4 feet of fill was encountered. This fill was described as fine to medium grained sands, being slightly moist and loose to medium dense. Terrace sands were encountered below the fill. These were described as fine to medium grained sands, being slightly moist and medium dense to dense. Groundwater was encountered in AGTP-1 at a depth of approximately 12 feet and was not encountered in AGTP-2. Detailed logs of these excavations are presented in Appendix B of this report. File NO. 22366.01 Hi American Geotechnkal September 21,2000 Page 7 5.0 LABORATORY TESTING A laboratory testing program was developed for the soil samples recovered during the subsurface exploration. The program was designed to estimate soil properties for use in engineering evaluations. The laboratory testing included field moisture and density, maximum density, hydro-response and direct shear testing. A summary of the laboratory test results is presented in Appendix C. In general, the results of the laboratory testing indicated the soil at the site above the water table possessed fairly low moisture contents and correspondingly low levels of saturation. Additionally, the site soil was found to possess a moderate potential for collapse with the addition of water. Given the relatively cohesionless nature of the soil and the sampling process, a portion of the collapse potential determined through testing could be due to sample disturbance. File NO. 22366.01 • American Geotechnical September 21,2000 PageS 6.0 CONCLUSIONS Based upon the results of our geotechnical investigation at the subject site, no geotechnical conditions were encountered which would preclude the proposed improvements, provided the following conclusions and recommendations are incorporated into the project plans and specifications. Foundation recommendations have been provided to help reduce the potential for problems associated with the soil conditions encountered. The actual recommendations are discussed in detail in the following sections. Based on the results of our subsurface exploration it appears as if the rear portion of the lot is comprised primarily of beach sands overlying more competent material at depth. In it's present state this beach sand material is not considered suitable for support of the proposed structure. This unsuitable material extends to depths exceeding 12 feet near the outer edge of the proposed residence. Near the rear of the existing residence competent terrace deposits were encountered at a relatively shallow depth. As such, it anticipated that a majority of the existing residence is founded in competent terrace deposits. Considering this, it should be anticipated that proposed construction extending out past the rear of the existing residence will need to have a foundation system deepened to competent formational soil. If the recommendations herein are followed, it is anticipated that tolerable levels of soil related movement can be expected for the proposed structures. File NO. 22366.01 IB American Geotcchnical September 21,2000 Page 9 7.0 RECOMMENDATIONS 7.1 GENERAL Conclusions and recommendations contained in this report are based on information provided, information gathered, laboratory testing, engineering and geologic evaluations, experience and professional judgment. Recommendations contained herein are consistent with current industry practices. Other alternatives exist and can be discussed on request. Regardless of the approach taken, some risk will remain, as is always the case. The recommendations and design parameters presented below should be utilized by the design civil/structural engineer for the design of foundations. Once plans have been developed, they should be forwarded to this office for review and comment. 7.2 EARTHWORK AND SITE PREPARATION Given the improvements proposed and the configuration of the lot, it is anticipated that little grading will be necessary as part of improvements at the site. If any grading is necessary, it would be anticipated that it would be primarily for access, to remove and recompact any loose near surface material, or to remove and recompact any material disturbed during the demolition process. Prior to any grading, the site should be cleared of all surface and subsurface obstructions including things such as debris, buried utilities, existing improvements and should be stripped of vegetation. Vegetation, debris and demolition material should be disposed of off-site. Any holes or excavations made which extend below the finished grade should be filled with compacted soil. 7.2.1 CUTS AND EXCAVATIONS It is not anticipated that extensive cuts or excavations will be conducted during the construction of site improvements. However, if any removals or excavations are required they should not be conducted at angles of inclination of steeper than 2:1 (horizontalrvertical) without additional analysis and input by the geotechnical consultant. Additionally, no excavation or cut should be deeper than five (5) feet without additional analysis and recommendations by the geotechnical consultant. 7.2.2 FILLS Our investigation did not indicate the presence of expansive soils within the subject lot. If expansive soils are encountered during construction, it is recommended that they not be placed within five (5) feet of finish grade in the building pad area(s) or beneath appurtenant structures and should be kept a minimum of five (5) feet away from proposed structures, unless special design considerations are implemented. With this exception, the on-site soils are generally suitable for use as compacted fill provided they are free of organic material and debris. All areas planned to receive fills and/or improvements will require removal and recompaction of the loose near surface soil and/or unsuitable materials. If grading is to be conducted, additional input will be needed from the geotechnical consultant. All fill to be placed should be moisture conditioned and compacted to a minimum of 90 percent of the maximum dry density per ASTM D-1557. Fill should be placed in thin, uniform lifts (6 to 8 inches loose thickness). Fills placed on natural slopes should be keyed and benched into firm, competent material and inspected prior to the placement of fill. Any permanently graded site slopes should be constructed at inclinations no steeper that 2:1 (horizontal:vertical). The geotechnical consultant should be on-site to test and observe all fills/removals during grading operations, and also to review footing excavations, cuts, etc. File NO. 22366.01 Bl American Geotechnical September 21, 2000 Page 10 7.2.3 CUT/FILL TRANSITIONS AND LOT CAPPING Structures planned should not straddle cut/fill transitions. In order to prevent this, footings for the planned new residence should be deepened to competent formational soil. This can likely be accomplished with continuous footings where the existing residence now sits and by a deepened foundation system where the proposed residence will extend further to the rear than the existing residence. 7.3 FOUNDATION DESIGN PARAMETERS Based on our subsurface exploration it should be anticipated that the proposed expansion of the building footprint to the rear of the home be constructed on a deepened foundation system extending to competent formational materials at depth. Due to the varying depth of competent formational material it may be possible to provide a combination of continuous footings and piers. The structural engineer may want to consider this possibility in the design process. The near surface soil in the area of the proposed addition consisted of a relatively loose, cohesionless beach sand. As such, this material is not considered suitable for the support of structures without deepened foundations. The deepened foundations would also provide added protection against possible future erosion of the beach area which could possibly encroach on the subject property. Additionally, the beach sand below a depth of approximately 12 feet is considered saturated and could be subject to liquefaction should an earthquake occur. The portion of the residence to be constructed within the footprint of the existing residence is anticipated to be sitting on competent terrace deposits and these soil deposits are considered to have a negligible to very low potential for liquefaction. Continuous Footings Minimum Embedment depth into competent formational soil 2.0 feet Minimum width 18 inches Allowable Bearing Pressure for Continuous Footings Founded in Competent Formational Material 2,500 psf Total Loads (including wind or seismic) 3,500 psf Increases Capacity for Each Additional Foot of Depth Deeper Than Minimum 500 psf Maximum Value 6,000 psf Resistance to Lateral Loads Passive Soil Pressure (equivalent fluid pressure) 300 pcf Coefficient of Sliding Friction for Cast Concrete on Compacted Fill 0.35 Any footing near slopes should satisfy a minimum horizontal setback as indicated in the Uniform Building Code, Chapter 18, Figure 18-1-1. This distance should be measured from the lower leading edge of the footing to the slope face. Deepened Foundation Minimum pier dimension (either diameter or side of rectangular of square shaft) 2.0 feet Minimum pier embedment into competent formational soil 5.0 feet* File NO. 22366.01 M American Geotechnical September 21,2000 Page 11 Bearing Capacity for piers in competent formational soil (End Bearing) 6,000 psf * the depth of competent formational soil adjacent the residence is presented, on the logs in Appendix B and the depth of competent formational soil at the rear of the proposed addition was not determined during our subsurface exploration but is estimated to be approximately 15 to 20 feet based on experience and observations in other areas. Lateral Loading Lateral loads should be included in the design of piers. The following lateral loading criteria should be incorporated into the project design: Active Pressure 30pcf* At-Rest Pressure 45 pcf* Passive Pressure 300 pcf** *To be applied over three (3) pier diameters. This would account for a loss of support on the beach side of the piers. Additionally, this assumes clean, non-expansive backfill. Other design parameters may need to be provided at the time of construction if conditions differing from those anticipated are encountered. **To be applied over two (2) pier diameters. Should be calculated from the ground surface but neglected above the depth of water which was approximately 12 feet. Seismic Design Parameters The following site seismic parameters were determined in accordance with Section 16, Division IV-Earthquake Design of the Uniform Building Code (1997): Seismic Zone 4 Seismic Zone Factor (Z) 0.40 Soil Profile Type Sd Seismic Source Type B Seismic Coefficient (Ca) 0.44Na Seismic Coefficient (Cv) 0.64NV Near Source Factor (Na) 1.15 Near Source Factor (Nv) 1.4 It should be noted that these values are considered "minimum design values" as dictated in the Uniform Building Code. 7.4 STANDARD FOUNDATION RECOMMENDATIONS Actual foundation details should be determined by the designer using the criteria in Section 7.3, however, the following are presented as a guideline to supplement the design process. These recommendations should not preclude structural requirements. File NO. 22366.01 BB American Geotechnkal September 21,2000 Page 12 7.4.1 SLABS AND FOOTINGS New footings should be designed utilizing the criteria presented above. The new interior floor surface for the addition will likely either be raised wood flooring or a slab-on-grade. New interior and exterior slabs should be at least five (5) inches thick, and reinforced with a minimum of No. 4 rebar at 16 inches on center each way. Experience and research have shown that concrete with a high water/cement ratio can experience problems such as excessive shrinkage cracking, moisture intrusion, and high vapor emissions, among other things. Generally speaking, the higher the water/cement ratio, the higher the porosity and permeability of the concrete, and the lower the strength. Concrete designed for compressive strengths on the order of 2000 to 2500 psi can oftentimes have excessive levels of mixing water and correspondingly a high water/cement ratio. Consideration should be given to using the lowest possible water/cement ratio while still maintaining workability. It is recommended that concrete used for footings and slab areas have a minimum compressive strength of 3,000 psi with a maximum water/cement ratio of 0.45. All steel and concrete materials, details, placement procedures, and curing should be performed strictly in accordance with ACI specifications and guidelines. The slab design by the structural engineer and/or architect should consider shrinkage of the concrete to limit cracking to the slab and overlying floor coverings. Any new interior floor slabs should be underlain by a minimum of two (2) inches of clean sand, underlain by a moisture membrane such as visqueen. The visqueen should be a minimum of 10 mil thick and should provide a continuous vapor barrier sealed at all splices and around pipes or other protrusions. A four inch thick open graded gravel base should be placed below the visqueen to provide a capillary break. To help protect the visqueen from punctures during placement, it is recommended that a filter fabric such as Mirafi 140N be placed between the rock and visqueen. Finally, prior to installing any flooring in the residence moisture vapor emissions should generally be 3.0 lbs./l,000 sq. ft./day or less. If the contractor wishes to install flooring on slab with moisture vapor emissions in excess of this value additional input may be needed from the geotechnical consultant regarding steps to take prior to flooring installation. 7.4.2 APPURTENANT STRUCTURE FOUNDATIONS The same guidelines for slab and footings would also pertain to design and construction of appurtenant structures, with the exception of exterior flatwork which do not usually necessitate the use of a visqueen moisture barrier. However, the recommendations for slab thickness-and reinforcement for exterior flatwork still pertain to help reduce the potential for cracking and separations. In addition, proper jointing should be used to control cracking. As with interior concrete, all steel and concrete materials, details, placement procedures and curing should be performed strictly in accordance with ACI specifications and guidelines. Special detailing may be necessary to limit unsightly cracking at structural interfaces, such as between foundations and adjacent slabs. Appurtenant structures placed near slope tops could creep over time in response to slope movement. Appurtenant structures should be kept as far away from stop tops as possible. For slopes ten (10) feet in height or less, a minimum setback often (10) feet is recommended unless special detailing is implemented. This might include structurally tying exterior slabs to the foundation or providing a thicker, heavily reinforced section. If needed, actual details should be developed by the project architect and/or structural engineer. File NO. 22366.01 !• American Geotechnical September 21,2000 Page 13 7.4.3 REINFORCEMENT PLACEMENT Care should be taken when placing foundation and slab reinforcement. Placement details should be in conformance with ACI specifications. Unless otherwise specified by the structural engineer, continuous footing reinforcement should be placed in the upper and lower 1/3 portions of the foundation's sections. The bottom foundation steel should not be closer than three inches to the underlying excavation. Slab reinforcement should be placed in a positive fashion between the midpoint and upper 1/3 portion of the slab section. "Lifting" slab steel into place following concrete placement is not recommended. If the contractor elects to "lift" the reinforcement into position following concrete placement, the owner should consider verifying steel placement by coring of the slab. 7.5 RETAINING WALL DESIGN CRITERIA It was not determined if retaining walls are planned at the site. Where planned they should be designed utilizing the following design criteria: Restrained Walls (level backfill): At-Rest Soil Pressure 45 pcf e.f.p. Passive Soil Resistance 300 pcf e.f.p. Cantilever Walls (level backfill): Active Soil Pressure 30 pcf e.f.p. Passive Soil Resistance 300 pcf e.f.p. In order for these soil design parameters to be valid, all planned retaining walls should be designed with appropriate detailing including an adequate backdrain system and a clean, non-expansive backfill for a width of at least the height of the retaining wall for level backfill conditions. All retaining walls should be waterproofed from above the highest point of earth retained to the heel of the foundation. The architect should provide details for waterproofing including termination details and provisions for protecting the waterproofing. Each retaining wall should be provided with an appropriate backdrain system designed by the project architect or civil engineer. It is recommended that the backdrain system extend to the heel of the foundation, and at least one foot below interior slab elevation (where applicable). Water collected in the backdrain system should ideally be recovered in a perforated PVC plastic pipe (perforations down) and directed to a suitable disposal area at two percent gradient unless otherwise specified by the project civil engineer. Retaining wall backfill should be placed in thin lifts (6-8 inches) and compacted by mechanical means. Care should be taken not to utilize heavy compaction equipment in close proximity to the walls to help reduce the possibility of damage to the wall and an increase in the above recommended earth pressures. File NO. 22366.01 Hi American Geotechnical September 21,2000 Page 14 7.6 SITE DRAINAGE Proper surface drainage should be incorporated into the design for the proposed project. Because of potential problems associated with poor drainage conditions, proper surface drainage should be maintained at all times. As a minimum, the following standard drainage guidelines are recommended and should be considered by the civil engineer during final plan preparation: A. Roof drains should be installed on all structures and tied via a "tight line" to a drain system that empties to a storm drain or terrace drain. B. Surface water should flow away from structures and slopes and be directed to suitable (maintained) disposal systems such as yard drains, drainage swales, street gutters, etc. Five percent drainage directed away from structures is recommended, and two percent minimum is recommended over soil areas. Planter areas adjacent the foundation are not recommended, unless the plants are self-contained with appropriate drainage outlets (i.e., drainage outlets tied via a "tight line" to a yard drain system). C. No drains should be allowed to empty adjacent foundations or over slopes. D. PVC Schedule 40 or equivalent is preferred for yard drains. A corrugated plastic yard drain is not recommended. 7.7 UTILITIES It is not recommended that utilities be planned below a 1:1 projection extending down from the outer edge of foundations. Footings should be deepened to satisfy the foregoing recommendation. Backfill for all utilities should be placed by mechanical compaction methods. Flooding and/or jetting of utility or other trench backfill should not be undertaken. 7.8 CORROSIVITY With respect to buried piping, it is considered good construction practice to provide corrosion protection by means of a suitable coating. Placing pressure plumbing overhead instead of under slabs is desirable. It is recommended that slab and footing concrete be at least Type II with a maximum water-cement ratio of 0.45 by weight. 7.9 GEOTECHNICAL SERVICES DURING CONSTRUCTION A representative of this office should be on hand during construction to provide observation and testing services. Our representatives should be on site whenever compacted fill is being placed. We recommend providing observation of all foundation excavations prior to the placement of forms, reinforcement or concrete. Furthermore, it is recommended that our office be requested to review the slab subgrade areas prior to the placement of concrete. 7.10 PLAN REVIEW When final plans are available, they should be forwarded to our office for review and comment and/or signature indicating compliance with the intentions of the recommendations contained in this report. If any of the other design professionals or construction members have any questions regarding the site geotechnical conditions or the recommendations of this report, our office should be contacted. File NO. 22366.01 •• American Geotechnical September 21,2000 Page 15 8.0 OTHER CONSIDERATIONS 8.1 GRADING CONSIDERATIONS Recommended grading included removing and recompacting loose near surface material. Other than possible limited removal and recompaction no other grading is anticipated at the site. If additional grading is planned, the geotechnical consultant should be contacted for additional input and recommendations. 8.2 SUPPLEMENTAL CONSULTING This office should be contacted for review of plans for improvements, and should be involved during construction in order to monitor the geotechnical aspects of the development (i.e., grading, foundation excavations, etc.). Unless other arrangements are made, supplemental consulting will be on a time-and-expense basis. 8.3 FIELD CONSTRUCTION REVIEW During construction, it is recommended that this office verify site geotechnical conditions and conformance with the intentions of the recommendations for construction. Although not all possible geotechnical observation and testing services are required by the governing agencies, the more site reviews performed, the lower the risk of future problems. 8.4 PROJECT SAFETY The contractor is the party responsible for providing a safe site. American Geotechnical will not direct the contractor's operations and cannot be responsible for the safety of personnel other than our own representatives on-site. The contractor should notify the owner if he is aware of, and/or anticipates, unsafe conditions. At the time of construction, if the geotechnical consultant considers conditions unsafe, the contractor, as well as the owner's representative, will be notified. 8.5 GROUND WATER CONSIDERATIONS As discussed groundwater should be anticipated to be a factor in the excavation of any deep foundation system. Excavations in the cohesionless beach sands under water should be considered to likely slough into any open excavations. Excavating below the water table may require temporary shoring and should be considered by the contractor in planning the method of construction. File NO. 22366.01 •§ American Geotechnical September 21, 2000 Page 16 9.0 REMARKS The design parameters and foundation guidelines presented above should be.considered minimums. The structural requirements may dictate more rigorous design and as such should govern. Once final plans have been prepared, they should be submitted to American Geotechnical for review. In addition, all footing excavations, removal and compaction operations should be verified by a representative of this office. Only a portion of subsurface conditions have been reviewed and evaluated. Conclusions and recommendations and other information contained in this report are based upon the assumptions that subsurface conditions do not vary appreciably between and adjacent, observation points. Although no significant variation is anticipated, it must be recognized that variations can occur. This report has been prepared for the sole use and benefit of our client. The intent of the report is to advise our client on geotechnical matters involving the proposed improvements. It should be understood that the geotechnical consulting provided and the contents of this report are not perfect. Any errors or emissions, and/or any other geotechnical aspect of the project, noted by any party reviewing this report, should be reported to this office in a timely fashion. The client is the only party intended by this office to directly receive this advice. Subsequent use of this report can only be authorized by the client. Any transferring of information or other directed use by the client should be considered "advice by the client." File NO. 22366.01 Bl American Geotechnical September 21,2000 APPENDIX A -REFERENCES "Landslide Hazards in the Northern Part of the San Diego Metropolitan Area, San Diego County, California," prepared by Siang S. Tan and Desmond G. Giffen, dated 1995. "Geologic Map of North-Central Coastal Area of San Diego County, California, Showing Recent Slope Failures and Pre-Development Landslides," prepared by F. Harold Weber, Jr., dated 1982. "Geology of the San Diego Metropolitan Area, California, Bulletin 200," prepared by Michael P. Kennedy, dated 1975. "Physical Geology," prepared by James S. Monroe and Reed Wiscander, dated 1992. File NO. 22366.01 •{American Geotechnical September 21,2000 APPENDIX B - SUBSURFACE LOGS • AGTP-1 • AGTP-2 test'Pit No:AGTP-1 ^.N. 22366 project Name:_QuirkResidence_Sheet: 1 of 1 Location = 3075 Ocean Street, Carlsbad. CA. 17' S & 14.5' W of NW corner of building.Start =7/26/00 Estimated Surface Elevations.Total nept-.h: 12' Rig Type: Hand Excavated/Sawcut End:7/26/00 e a Field Description ByrTMP Surface Conditions: Dry Concrete = ° subsurface conditions:FORMATION: Classification, color, moisture, tightness, etc 0.0-= 0.5-0-0.3' - CONCRETE SLAB. W^m BEACH SANDS (Ob): 0.3-4.2' - Fine SAND, light brown, slightly moist, loose to moderately dense with depth, massive, possibly fill soils. 4.2-5.0' - Fine SAND, light brown/black, moist, medium dense to dense, laminated bedding in upper 6". 5.0-6.3' - Coarse SAND, orange light brown; moist to very moist with depth, medium dense to dense, clean. @ 6.0' - Becomes dense. 6.3-9.0' - Fine SAND, olive light brown, slightly moist, dense, occasional rounded gravel to 1/2" diameter, occasional shell fragments. 9.0-12.0' - Coarse SANDS, olive light brown, moist, medium dense, no binder. 11.2' - Becomes dense, moist to very moist. 12.0' - Saturated SANDS, ground water, salt water wedge?. Test pit terminated. Seepage at 12.0'. Legend: Large Bag American Geotechnical Test Pit AGTP-1- f est^Pit No:AGTP-2 P.P. 22366 project Name:J2MilkResidence_Sheet- 1 Of 1 Location: 3075 Ocean Street, Carlsbad, CA. 11.5' S of NW corner of building, adjacent footing.Start :7/26/00 Estimated Surface Elevations 10'Total nppth: 9' Rig Typg: Hand Excavated/Sawcut End:7/26/00 0) <DQ Cu e aITJ >i Field Description By: IMP Surface Conditions: Dry Concrete subsurface conditions:FORMATION: Classification, color, moisture, tightness, etc o.o- 0.5- 1.0- 1.5- 2.0- 2.5- 3.0- 3.5- 4.0- 4.5- 5.0- 5.5- 6.0- 6.5- 7.0- 7.5- 8.0- 8.5- 9.0- 0-0.37' - CONCRETE SLAB. FILL: 0.30-2.4' - Fine to Medium SANDS, olive brown, slightly moist, loose to medium dense, occasional rootlets/rounded cobble to 6" diameter, undulatory lower contact variable from 1.8-2.4', lower at NW corner of test pit. @ 0.90' - Ash bed, 1/4" thick. TERRACE SAND (Obyl: 2.4-3.5' - Fine to Medium SAND, orange light brown, slightly moist to moist, medium dense to dense, slightly cemented. 3.5-5.8' - Fine SAND, olive light brown, slightly moist, medium dense, inter-tongued beach sands. 6.5-7.5' - Medium SAND, orange light brown, slightly moist, dense, no binder, beach sands?, inter-tongued beach sands below 3.5'. 8.5-9.0' - Fine to Medium SANDS, tan, slightly moist, medium dense to dense, no binder, beach sands. @ 9.0' - Test pit terminated. No caving. No seepage. Legend: LJ Large Bag American Geotechnical Test Pit AGTP-2- File NO. 22366.01 HI American Gcotechnical September 21,2000 APPENDIX C - LABORATORY PROCEDURES & RESULTS Moisture Content Determinations Moisture content determinations were made in accordance with ASTM method of test D2216-92. Dry Unit Weight Dry unit weight testing of soil samples were determined in accordance with conventional laboratory techniques. Compaction Tests Maximum dry density and optimum moisture content determinations were performed in accordance with ASTM method of test D1557-91 A. Direct Shear Direct shear tests were performed on samples remolded to in-place moisture and density. Soil samples were allowed to soak for about 24 hours while under the confining pressure specified for testing. Consolidated drained conditions were approximated by using a slow, strain-controlled approach, similar to that outlined in ASTM method of test D3080-90. Simple Collapse Tests Simple collapse tests were performed on remolded ring samples in accordance with ASTM test method D5333- 92, except that time-rate readings were not taken. File No. 22366.01 September 21, 2000 American Geotechnkal MOISTURE/DENSITY RELATIONSHIP TEST SUMMARY AGTP-1 @ 0.4-1.9' Beach SAND ASTMD1557-91, "A" File No. 22366.01 September 21,2000 American Geotechnical FIELD DENSITY TEST SUMMARY LOCATION (in feet) AGTP-1 @ 0.4- 1.9' AGTP-1 @ 3.3-4.9' AGTP-1 @ 5.0-6.3' AGTP-2 @ 2.3-3.7' AGTP-2 @ 4.3-5.8' AGTP-2 @ 6.7-7.5' AGTP-2 @ 8.5-9.0' FIELD DRY DENSITY (pcf) 94.7 101.6 103.0 96.7 96.2 85.7 91.2 AFIELD MOISTURE CONTENT (%) 4.6 5.7 10.8 5.3 3.3 3.7 3.2 DEGREE OF SATURATION (%) 16 23 46 19 12 10 10 SAMPLE TYPE T T T T T T T T = Shelby Tube Sample File No. 22366.01 September 21,2000 American Geotechnkal SIMPLE COLLAPSE TEST DATA SUMMARY AGTP-2 @ 2.3-3.7' AGTP-2 @ 4.3-5.8' AGTP-2 @ 6.7-7. 5' AGTP-2 @8.5-9.0' T T T T 96.7 96.2 85.7 91.2 5.3 3.3 3.7 3.2 1000 1000 1000 1000 19 12 10 10 -0.86 -0.67 -1.51 -1.53 T = Shelby Tube Sample 135 133 131 129 127 125 123 121 119 D R 117 Y D 115 E N 113 S j 111 Y 109 P 0 JQ., u n d 105 s p 103 e r 101 C 99 u b i 97 c F 0 o 93 t 91 89 87 85 83 81 79 77 75( / / > _wf \ • ' 1 ^ / ' \ v i/ \ ^ V - /^. y\\ \ < 1 f / *^ v\ \ v '•>«, \ •k v\ \ - v ^--. \ - k^_ File no Project Des \ v v\ \ > \\ \ " v\ \ 22366.01 Date 8/2/00 Ouirk residence Source of ma :riptionof Mai Test Me s\ - \ > \ \\ \ >x O s\ \ i^-i AGTP-1® 0.4-1.9' terial medium coarse beach sand thod A.S.T.M.D1557-91,"A" TEST RESULTS Maximum Dry Density 112. 5 PCF ptimum Water Content 12.0% CURVES OF 100% SATURATIONFOR SPECIFIC GRAVITY EQUAL TO: hv ~ 2'8° \ - 270 ^ \ ^^_\. -- 2.60 1 • \A \ ^\\\ \L - \ \ \ • V ^ '^V \ \ ]V rs. 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