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HomeMy WebLinkAboutCT 01-09; LA COSTA TOWN SQUARE COMMERCIAL; SOILS, GEOTECHNICAL; 2012-07-31SOUTHERN CALIFORNIA SOIL&TESTINGJNC. A r.»liforni,) f f'rtifi«>d Small fluMn»»<.s Fni e i pt is t' i sHF > RECORD COPY San Diego 6280 Riverdale Street 619.280.4321 San Diego, CA 92120 Indio 83-740 Citrus Avenue 760.776.S983 Suite Q Indio, CA 92201-3438 Riverside 1130 Palmyrita Avenue 961.966.8711 Suite 330-A Riverside, CA 92607 Toll Free 877.216.4321 www.scst.com GEOTECHNICAL INVESTIGATION LA COSTA TOWN SQUARE COMMERCIAL DEVELOPMENT CARLSBAD, CALIFORNIA PREPARED FOR: MR. RICK HENDERSON PROPERTY DEVELOPMENT CENTERS 5918 STONERIDGE MALL ROAD PLEASANTON, CAUFORNIA 94588 PREPARED BY: SOUTHERN CALIFORNIA SOIL & TESTING, INC. 6280 RIVERDALE STREET SAN DIEGO, CALIFORNIA 92120 Providing Professional Engineering Services Since 1959 SOUTHERN CALIFORNIA SOIL&TESTING,INC. A California fprt if led Sm/ill Bn'.inps^i FntPrprKf ;SKFl San Oiego 6280 Riverdale Street 619.280.4321 San Diego, CA 92120 Indio 83-740 Citrus Avenue 760.776.6983 Suite G Indio, CA 92201-3438 Riverside 1130 Palmyrita Avenue 961.966.8711 Suite 330^ Riverside. CA 92607 Toll Free 877.216.4321 www.scst.com Januarys, 2012 SCS&T No. 1111199 Revised July 31, 2012 Report No. IR Mr. Jim Reuter Property Development Centers 5918 Stoneridge Mall Road Pleasanton, California 94588 Subject: GEOTECHNICAL INVESTIGATION LA COSTA TOWN SQUARE COMMERCIAL DEVELOPMENT CARLSBAD, CALIFORNIA Dear Mr. Reuter: This letter transmits Southern California Soil & Testing Inc.'s (SCS&T) report describing the updated geotechnical investigation performed for the planned commercial development. The subdivision will be located at the southeast corner of Rancho Santa Fe Road and La Costa Avenue in the City of Carlsbad, California. This investigation was conducted in general conformance with the scope of work presented in SCS&T's proposal dated November 16, 2011. If you have any questions concerning this report, or need additional information, please call us at (619) 280-4321. Respectfully Submitted, SOUTHERN CALIFORNIA SOIL AND Sarrett B. Fountain, GE 2752 Vice President/ Principal Engineer GBF:AKN:aw Douglas A. Skinner, CP©-2«r72 Senior Engineering Geologist (8) Mr. Mark Langan (1) Mr. Mark Langan via e-mail at markl@sca-sd.com (1) Mr. Rick Henderson via e-mail at rick.henderson@pdcenters.com TABLE OF CONTENTS SECTION PAGE EXECUTIVE SUMMARY 1. INTRODUCTION 1.1 GENERAL 1.2 SCOPE OF WORK 1.2.1 Field Exploration 1.2.2 Laboratory Testing 1.2.3 Analysis and Report 2. SITE AND SUBSURFACE CONDITIONS 2 2.1 SITE DESCRIPTION 2 2.2 STOCKPILE 2 2.3 SUBSURFACE CONDITIONS 2 2.4 GROUNDWATER 3 2.5 LANDSLIDES 3 2.6 POTENTIAL GEOLOGIC HAZARDS 3 2.7 SEISMIC DESIGN PARAMETERS 3 3. CONCLUSIONS 4 4. RECOMMENDATIONS 4 4.1 SITE PREPARATION AND GRADING 4 4.1.1 Site Preparation 4 4.1.2 Compressible Soil Removal 5 4.1.3 Excavation Characteristics 5 4.1.4 Expansive Soil 5 4.1.5 Rock Fill Placement 5 4.1.6 Building Pad Over-Excavation Requirements 6 4.1.7 Earthwork 6 4.1.8 Key way 6 4.1.9 Subdrains 7 4.1.10 Fill Slopes 7 4.1.11 Permanent Cut Slopes 7 4.1.12 Temporary Excavation Slopes 7 4.1.13 Shrinkage and Bulkage Estimates 8 4.1.14 Imported Soil 8 4.1.15 Surface Drainage 8 4.1.16 Settlement Monitoring 8 4.1.17 Grading Plan Review 8 4.2 FOUNDATIONS 9 4.2.1 Conventional Footings 9 4.2.2 Foundation Excavation Observations 9 4.2.3 Static Settlement Characteristics 9 4.2.4 Resistance to Lateral Loads 9 4.2.5 Foundation Plan Review 9 4.3 SLABS-ON-GRADE 9 4.3.1 Interior Concrete Slabs-on-Grade 9 4.3.2 Exterior Concrete Slabs-on-Grade 10 TABLE OF CONTENTS (Continued) SECTION PAGE 4.4 EARTH RETAINING WALLS 11 4.4.1 Foundations 11 4.4.2 Passive Pressure 11 4.4.3 A ctive Pressure 11 4.4.4 A t-Rest Pressure 11 4.4.5 Seismic Earth Pressure 11 4.4.6 Waterproofing and Backdrain Observation 12 4.4.7 Backfill 12 4.4.8 Factor of Safety 12 4.5 MSE WALL DESIGN PARAMETERS 12 TABLE 3 12 4.6 PAVEMENT SECTION RECOMMENDATIONS 12 TABLE 4 13 4.7 INFILTRATION RATES 13 5. GEOTECHNICAL ENGINEERING DURING CONSTRUCTION 14 6. CLOSURE 14 TABLES Table 1 Expansion Index Requirements Table 2 Estimated Shrinkage and Bulkage Estimates Table 3 Mechanically Stabilized Earth Wall Design Parameters Table 4 Flexible Pavement Recommendations Table 5 Rigid Pavement Recommendations ATTACHMENTS FIGURES Figure 1 Site Vicinity Map Figure 2 Subsurface Investigation Map Figure 3 Grading Consideration Map Figures 4 and 5 Oversize Rock Placement Detail Figure 6 Subdrain Detail Figure 7 Wall Backdrain Details APPENDICES Appendix I Logs of Exploratory Test Trenches Appendix II Laboratory Testing Appendix III Seismic Traverse Results EXECUTIVE SUMMARY This report presents the results of the geotechnical investigation Southern California Soil and Testing, Inc. (SCS&T), performed for the planned commercial development to be located on the southeast corner of Rancho Santa Fe Road and La Costa Avenue in the City of Carisbad, California. The purpose of our work is to provide conclusions and recommendations regarding the geotechnical aspects of the project. An SCS&T geologist observed the excavation of 7 exploratory test trenches to depths of between 8 feet and 14 feet below the existing grade with a rubber tire backhoe equipped with an 18-inch bucket. The backhoe encountered refusal in test trenches, T-1 and T-7. SCS&T also observed the drilling of 4 exploratory test borings using a truck mounted drill rig equipped with a hollow stem auger. SCS&T tested selected samples from the trenches and borings to evaluate pertinent classification and engineering properties and assist in the development of geotechnical conclusions and recommendations. Additionally, 1 seismic traverse was performed to determine rippability characteristics ofthe underiying rock. Materials encountered in the test trenches and borings and exposed near the surface consist of fill, alluvium, Delmar Formation and Metavolcanic rock. The fill and alluvium are comprised of loose, clayey sand and soft, sandy clay. The Delmar Formation is comprised of very stiff to hard, sandy claystone and clayey sandstone. The metavolcanic rock is comprised of metamorphosed and un-metamorphosed volcanic and sedimentary rock commonly identified as the Santiago Peak Volcanics. The main geotechnical considerations affecting the planned development are: • The presence of compressible alluvial materials; • Expansive soils; • Difficult excavation conditions; • Cut/fill transitions below the building pads; • Oversize materials. Mass grading operations are expected to consist of cuts and fills ranging from between about 5 feet and 50 feet. The on-site clayey materials tested have high expansion potentials. The seismic traverses indicate that the rock on-site will require blasting and specialized rock breaking equipment during excavation. To reduce the potential for differential settlement and/or heaving select grading and over-excavation ofthe building pads will need to be performed. We expect that the excavated rock will need to be processed with the expansive soil to produce a suitable fill material. Production of a suitable fill material is expected to require crushing and/or screening. Shallow spread footings with bottom levels in compacted fill can be used for the support of the planned structures. 1. INTRODUCTION 1.1 GENERAL This report presents the results of the geotechnical investigation Southern California Soil and Testing, Inc. (SCS&T), performed for the planned commercial development to be located on the southeast corner of Rancho Santa Fe Road and La Costa Avenue in the City of Carisbad, California. The purpose of our work is to provide conclusions and recommendations regarding the geotechnical aspects of the project. Figure 1 presents a site vicinity map. 1.2 SCOPE OF WORK 1.2.1 Field Exploration Subsurface conditions were explored by excavating a total of 4 exploratory test trenches to depths of between 8 feet and 14 feet below the existing grade with a rubber tire backhoe equipped with an 18-inch bucket. SCS&T also observed the drilling of 4 exploratory test borings using a truck mounted drill rig equipped with a hollow stem auger. Additionally, 1 seismic traverse was performed to determine the rippability characteristics of the underiying materials. Figure 2 shows the locations of the test trenches, test borings and seismic traverses. An SCS&T geologist logged the test trenches and borings and obtained samples for examination and laboratory testing. The logs of the test trenches and borings are in Appendix I. Soils are classified according to the Unified Soil Classification System illustrated on Figure 1-1. The seismic traverse results are in Appendix III. 1.2.2 Laboratory Testing The laboratory program consisted of tests for: • Expansion Index The results of the laboratory tests, and brief explanations of test procedures, are in Appendix II. 1.2.3 Analysis and Report SCS&T evaluated the results of the field and laboratory tests to develop conclusions and recommendations regarding: 1. Subsurface conditions beneath the site; 2. Site preparation; 3. Excavation characteristics; 4. Potential geologic hazards that may affect the site; 5. Criteria for seismic design in accordance with California Building Code procedures; 6. Appropriate alternatives for foundation support along with geotechnical engineering criteria for design ofthe foundations; iC, Property Development Centers La Costa Town Square Commercial Development Carlsbad, California July 31, 2012 SCS&T Proposal No. 1111199-01R Page 2 7. Resistance to lateral loads; 8. Estimated foundation settlements; 9. Support for concrete slabs-on-grade floors; 10. Lateral pressures for the design of retaining walls; 11. Pavement sections. 2. SITE AND SUBSURFACE CONDITIONS 2.1 SITE DESCRIPTION The subject site is an irregular shaped lot located on the southeast corner of Rancho Santa Fe Road and La Costa Avenue in the City of Carisbad, California. The site is bounded by vacant land on the east, Rancho Santa Fe Road on the north, and La Costa Avenue and a residential subdivision on the south and west sides. A stockpile of rocks is located at the northeastern portion of the project area. The site is located along a south-facing slope that is characterized by 3r north-south trending, natural drainage swales that flow to the south. The total elevation difference of the site is about 80 feet over a span of 2,000 feet. Vegetation consists of native grasses and shrubs. 2.2 STOCKPILE A stockpile is located at the northeast corner of the site. The material observed in the stockpile consists of clayey soils and rocks that range up to about 4 feet in maximum dimension. This material was most likely derived from excavations performed as part of the construction of Rancho Santa Fe Road and nearby developments. The stockpile appears to be about 20 feet thick at it deepest section and is most likely underiain by metavolcanic rock. 2.3 SUBSURFACE CONDITIONS Alluvium, Delmar Formation, and metavolcanic rock underiie the subject site. Figure 2 shows the approximate limits of the geologic materials. Fill: SCS&T's geologist observed fill comprised of loose clayey sand and sift sandy clay and boulders test trench T-1 and T-7. The fill encountered in test trench T-5 consisted of clayey sand. Figure 2 shows the approximate limits of this material. This fill encountered in our test trenches extended to beyond the maximum depth explored of 10 feet. Alluvium: SCS&T's geologist observed alluvium comprised of loose clayey sand and soft sandy clay with gravel in test trench T-6. In general, this material is located within the drainage swales at the site. This alluvium encountered in our test trench extended to a depth of about 5 feet below the ground surface and overiies the Delmar Formation. 1^ • Property Development Centers July 31, 2012 La Costa Town Square Commercial Development SCS&T Proposal No. 1111199-01R Carlsbad, California Page 3 Delmar Formation: SCS&T's geologist observed the Delmar Formation comprised of very stiff to hard, sandy claystone at the surface in test trenches T-2, T-3 and T-4 and borings B- 1 through B-5. This material extended beyond the maximum depth explored of 47 feet in test boring B-4. Metavolcanic Rock: SCS&T's geologist observed Metavolcanic rock on the surface exposed along the eastern portion of the site. The metavolcanic rock is typically comprised of metamorphosed and un-metamorphosed volcanic and sedimentary rock commonly identified as the Santiago Peak Volcanics. 2.4 GROUNDWATER SCS&T's geologist observes groundwater seepage in the test boring B-4 at a depth of about 34 feet below the existing grade and test trench T-7 at a depth of 8 feet. Water and wet soil should be expected at the bottoms of the existing alluvial channels. Groundwater levels can fluctuate seasonally, and can rise significantly following periods of precipitation. In addition, groundwater can be perched on impermeable layers of the claystone and/or rock as a result of rainfall and irrigation. 2.5 LANDSLIDES No landslides are mapped at or near the subject site. A slope failure occurred northwest of the subject site at the southeastern terminus of Agua Dulce Court in 2005. The slope failure occurred on the northwest facing fill slope built during the construction of the original Rancho Santa Fe Road alignment and was surficial in nature. We understand a buttress and a permanent subdrain system was constructed to reduce the potential for future failures 2.6 POTENTIAL GEOLOGIC HAZARDS No known geologic hazards are mapped across the site. A geologic hazard likely to affect the project is groundshaking as a result of movement along an active fault zone in the vicinity of the subject site. 2.7 SEISMIC DESIGN PARAMETERS The site coefficients and adjusted maximum considered earthquake spectral response acceleration parameters in accordance with the 2010 California Building Code based on the 2009 International Building Code are presented below: Property Development Centers July 31, 2012 La Costa Town Square Commercial Development SCS&T Proposal No. 1111199-01R Carlsbad, California Page 4 Site Coordinates: Latitude 33.083° Longitude -117.229° Site Class: D Site Coefficient Fa = 1.056 Site Coefficient Fv = 1.583 Spectral Response Acceleration at Short Periods Ss = 1.1 Spectral Response Acceleration at 1-Second Period Si = 0.4 SMS^FSSS SMI=FVSI SDS=2/3* SMS SDI=2/3* SMI 3. CONCLUSIONS The main geotechnical considerations affecting the planned development are: • The presence of compressible alluvial materials; • Expansive soils; • Difficult excavation conditions; • Cut/fill transitions below the building pads; • Oversize materials. Mass grading operations are expected to consist of cuts and fills ranging from between about 5 feet and 50 feet. The on-site clayey materials tested have high expansion potentials. The seismic traverses indicate that the rock on-site will require blasting and specialized rock breaking equipment during excavation. To reduce the potential for differential settlement and/or heave, select grading and over-excavation of the building pads will need to be performed. We expect that the excavated rock will need to be processed with the expansive soil to produce a suitable fill material. Production of a suitable fill material is expected to require crushing and/or screening. Other alternatives to produce a suitable fill material can also be considered. Shallow spread footings with bottom levels in compacted fill can be used for the support of the planned structures. 4. RECOMMENDATIONS 4.1 SITE PREPARATION AND GRADING 4.1.1 Site Preparation Site preparation should begin with the removal of the existing vegetation and debris. It is expected that the upper 6 inches of the exposed surface will need to be brushed and exported from the site. The stockpiled materials and existing fill should be excavated in their entirety. Figure 3 presents the approximate bottom elevations of the fill that will be excavated. Lf Property Development Centers La Costa Town Square Commercial Development Carlsbad, California July 31, 2012 SCS&T Proposal No. 1111199-01R Page 5 4.1.2 Compressible Soil Removal It is recommended that existing compressible soils (fill, alluvium and highly weathered formational deposits) underiying areas of the site to be graded be excavated in their entirety. SCS&T expects the compressible soil excavation to be about 3 feet within the alluvial drainage channels. No excavation for remedial grading is expected where rock is exposed on the surface. Figure 3 presents the approximate limits of the compressible soil removal. An SCS&T representative should observe conditions exposed in the bottom of the excavations to determine if additional excavation is required. 4.1.3 Excavation Characteristics Conventional heavy equipment in good working order is expected to be able to excavate the alluvial materials and Del Mar Formation on-site. However, non-rippable rock exists on-site, and these areas will require rock-breaking equipment. In addition, oversized, buried hard rock requiring special handling should be anticipated. Contract documents should specify that the contractor mobilize equipment capable of excavating and breaking the bedrock. Additionally, it should be noted that gravel, cobbles, and boulders up to 48 inches in diameter could be encountered within the stockpile. Contract documents should specify that the contractor mobilize equipment capable of compacting materials with gravel and cobbles. 4.1.4 Expansive Soil The existing materials on-site that were tested have a high expansion potential in accordance with ASTM D 4829. Expansive soil with an expansion index (El) greater than 90 should be placed at least 10 feet below the planned final pad grade elevation and at least 10 feet from the face of all fill slopes and retaining walls. Expansive soil with an El less than 90 can be placed at within 10 feet of the planned final pad grade elevation. Table 1 presents updated expansion index recommendations for the placement ofthe soil. Table 1 Depth Below Planned Final Grade Elevation Expansion Index of Material to be Placed Oto 10 feet Expansion Index Less Than 90 Greater than 10 feet Expansion Index Greater Than 90 Allowed 4.1.5 Rock Fill Placement The quantity of rock generated during grading operations will depend on the grading scheme. The rock will most likely consist of cobbles and boulders of varying size. The rock Property Development Centers July 31,2012 La Costa Town Square Commercial Development SCS&T Proposal No. 1111199-01R Carlsbad, California Page 6 should be mixed with sufficient quantities of soil such that nesting does not occur during placement and the rock is completely surrounded by a soil matrix material. It is expected that crushing and/or screening of on-site material will be required to achieve a suitable fill material. The rock/soil mixture should be placed in lifts of approximately 12 inches in thickness and compacted with a rubber-tire loader. Oversized rock between 6 inches and 2 feet may be placed in structural fills in accordance with the details illustrated in the attached Figures 4 and 5. Larger rock may only be utilized for landscaping purposes. Rocks greater than 3 inches in diameter should not be used within 18 inches of final grade or where foundation or utility trenches will be located. 4.1.6 Building Pad Over-Excavation Requirements Hard rock or expansive soil is expected to be encountered at the planned final grade elevation for the building pads located along the north side and middle of the site. The remainder of the lots will span a cut/fill transition with a fill differentials ranging between about 5 and 35 feet. Figure 3 presents the expected over excavation requirements for each building pad. The over-excavation depths shown may have to be increased depending on conditions observed during grading. The bottoms of the excavation and subgrades beneath fill areas should be sloped toward the street or fill portion of the lot, and away from its center. Subdrains will be needed at the bottom of the excavated areas. 4.1.7 Earthwork The material exposed in the bottom of the excavation should be scarified to a depth of 12 inches, moisture conditioned and compacted to at least 90% relative compaction. Excavated materials, except for soil containing roots and organic debris, can be used as compacted fill. Fill should be placed in 6- to 8-inch thick loose lifts, moisture conditioned to near optimum moisture content, and compacted to at least 90% relative compaction. The maximum dry density and optimum moisture content for the evaluation of relative compaction should be determined in accordance with ASTM D 1557. Utility trench backfill within 3 feet of the structure and beneath pavements and hardscape should be compacted to a minimum of 90% relative compaction. The upper 12 inches of subgrade beneath slabs and paved areas should be compacted to at least 95% relative compaction. 4.1.8 Keyway A keyway should be established at the base of sloped areas. The keyway should be at least 15 feet wide at the bottom, extend at least 3 feet into competent material and be sloped back at an inclination of about 2%. The keyway may need to be wider to accommodate Property Development Centers July 31, 2012 La Costa Town Square Commercial Development SCS&T Proposal No. 1111199-01R Carlsbad, California Page 7 compaction equipment. Final keyway recommendations will depend on the final grading plans. 4.1.9 Subdrains Canyon subdrains shall be installed at the bottom of canyon removals wherever fill depths exceed 10 feet. Canyon subdrains should consist of a perforated pipe (SDR 35 or equivalent), surrounded by at least 6 cubic feet per lineal foot of crushed rock wrapped in filter fabric (Mirafi MON or equivalent). A canyon subdrain is provided as Figure 6. As- graded canyon subdrain locations should be surveyed. Subdrains may be required at the heel of keyways for buttress slopes and/or fill-over-cut slopes, Figure 6. Subdrains may also be required for some transition undercut areas if warranted by soil conditions or the presence of groundwater. Figure 3 shows the approximate locations ofthe planned subdrains. 4.1.10 Fill Slopes Fill slopes can be constructed at an inclination of 2:1 (horizontahvertical). Compaction of slopes should be performed by back-rolling with a sheepsfoot compactor at vertical intervals of 2 feet or less as the fill is being placed, and by track-walking the face of the slope when the fill is completed. Alternatively, slopes can be overfilled and cut back to expose dense material at the design line and grade. Fills should be benched into temporary slopes and into the rock when the natural slope is steeper than 5:1 (horizontal: vertical). 4.1.11 Permanent Cut Slopes It is our opinion that cut slopes constructed at an inclination of 2:1 or flatter ratio will possess an adequate factor of safety. The engineering geologist should observe all cut slopes during grading to ascertain that no unforeseen adverse conditions requiring revised recommendations are encountered. 4.1.12 Temporary Excavation Slopes It is recommended that temporary cut slopes greater than 3 feet in depth be cut at an inclination no steeper that 1:1. Cuts less than or equal to 3 feet in depth can be made vertical. Temporary cut slopes should be observed by an SCS&T Engineering Geologist during grading to ascertain that no unforeseen adverse conditions are observed. The temporary slopes should be inspected daily by the contractor's Competent Person before personnel are allowed to enter the excavation. Zones of potential instability, sloughing or raveling should be brought to the attention of the Engineer and corrective action implemented before personnel begin working in the trench. No surcharge loads should be placed within a distance from the top of temporary cut slopes equal to half the slope height Property Development Centers July 31, 2012 La Costa Town Square Commercial Development SCS&T Proposal No. Ill 1199-01R Carlsbad, California Page 8 4.1.13 Shrinkage and Bulkage Estimates The estimate shrinkage and bulkage estimates are presented below. Table 2 Soil Type Shrinkage Bulkage Topsoil and alluvium 15% to 20% Del Mar Formation 5% to 10% Metavolcanic Rock 10% to 20% Rock Stockpile 15% to 20% 4.1.14 Imported Soil Imported fill should meet the specifications for Caltrans structure backfill and, if appropriate, be tested by SCS&T prior to transport to the site. 4.1.15 Surface Drainage Final surface grades around the buildings should be designed to collect and direct surface water away from the structure and toward appropriate drainage facilities. The ground around the structures should be graded so that surface water flows rapidly away from the structure without ponding. In general, we recommend that the ground adjacent to the structure slope away at a gradient of at least 2%. Densely vegetated areas where runoff can be impaired should have a minimum gradient of at least 5% within the first 5 feet from the structure. Roof gutters with downspouts that discharge directly into a closed drainage system are recommended on structures. Drainage patterns established at the time of fine grading should be maintained throughout the life of the proposed structures. Site irrigation should be limited to the minimum necessary to sustain landscape growth. Should excessive irrigation, impaired drainage, or unusually high rainfall occur, saturated zones of perched groundwater can develop. 4.1.16 Settlement Monitoring Fills on the order of between 30 feet and 50 feet are expected as part of the mass grading operations. Compacted fill can be expected to settle up to about 0.5% of the fill height. It is suggested that deep fills be monitored to determine when settlement is essentially complete. 4.1.17 Grading Plan Review The grading plans should be submitted to SCS&T for review to ascertain whether the intent of the recommendations contained in this report have been implemented, and that no revised recommendations are necessary due to changes in the development scheme. Property Development Centers July 31, 2012 La Costa Town Square Commercial Development SCS&T Proposal No. 1111199-01R Carlsbad, California Page 9 4.2 FOUNDATIONS 4.2.1 Conventional Footings Structures and retaining walls can be supported on shallow spread footings with bottom levels in compacted fill. A minimum width of 12 inches is recommended for continuous footings for single story structures and 15 inches for 2 story structures. Isolated footings should be at least 24 inches wide. All footings should extend a minimum of 36 inches below lowest adjacent grade. A bearing capacity of 2,500 pounds per square foot (psf) can be used. These values can be increased by Ys when considering the total of all loads, including wind or seismic forces. Footings adjacent to slopes should be extended to a depth such that a minimum distance of 7 feet exists between the bottom ofthe footing and the face ofthe slope. For conventional retaining walls, a minimum 10-foot distance is recommended. 4.2.2 Foundation Excavation Observations It is recommended that all foundation excavations be approved by a representative from SCS&T prior to forming or placing reinforcing steel. 4.2.3 Static Settlement Characteristics Total footing settlements are estimated to be less than 1 inch. Differential settlements between adjacent footings are estimated to be less than 14 inch. Settlements should occur rapidly, and should be completed shortly after structural loads are applied. 4.2.4 Resistance to Lateral Loads Lateral loads will be resisted by friction between the bottoms of the footings and passive pressure on the faces of footings and other structural elements below grade. A friction factor of 0.3 can be used. Passive pressure can be computed using a lateral pressure value of 300 psf per foot of depth below the ground surface. The upper foot of soil should not be relied on for passive support unless the ground is covered with pavements or slabs. 4.2.5 Foundation Plan Review The foundation plans should be submitted to SCS&T for review to ascertain that the intent of the recommendations in this report has been implemented and that revised recommendations are not necessary due to the layout. 4.3 SLABS-ON-GRADE 4.3.1 Interior Concrete Slabs-on-Grade Concrete slabs-on-grade should be designed by the project structural engineer. Slabs-on- grade should be underiain by a 4-inch thick blanket of clean, pooriy graded, coarse sand (sand equivalent = 30 or greater) or Va-inch crushed rock. Where moisture sensitive floor Property Development Centers July 31, 2012 La Costa Town Square Commercial Development SCS&T Proposal No. 1111199-01R Carlsbad, California Page 10 coverings are planned, a vapor retardant should be placed over the sand layer. Typically, visqueen is used as a vapor retardant. If visqueen is used, a minimum 10-mil is recommended. Moisture emissions can vary widely, depending upon such factors as concrete type and subgrade moisture conditions. If these moisture emission values are not within the manufacturer's specifications for the type of flooring to be installed, SCS&T should be contacted to develop appropriate additional damp-proofing recommendations. It is recommended that moisture emission tests be performed prior to the placement of floor coverings. In addition, over-watering should be avoided, and good site drainage should be established and maintained to reduce the potential for the build-up of excess sub-slab moisture. 4.3.2 Exterior Concrete Slabs-on-Grade Exterior slabs should have a minimum thickness of 4 inches and should be reinforced with at least No. 3 bars at 18 inches on center each way. Additionally, slabs should be underiain by at least 6 inches of aggregate base. Slabs should be provided with weakened plane joints. Joints should be placed in accordance with the American Concrete Institute (ACI) Guidelines Section 3.13. Joints should be placed where cracks are anticipated to develop naturally. Alternative patterns consistent with ACI guidelines also can be used. The landscape architect can be consulted in selecting the final joint patterns. A 1-inch maximum size aggregate mix is recommended for concrete for exterior slabs. A water/cement ratio of less than 0.6 is recommended, in order to 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 (psi). Coarse and fine aggregate in concrete should conform to the "Greenbook" Standard Specifications for Public Works Construction. Special attention should be paid to the method of curing the concrete to reduce the potential for excessive shrinkage and resultant random cracking. Minor cracks occur normally in concrete slabs and foundations due to shrinkage during curing and redistribution of stresses. Some shrinkage cracks can be expected. These cracks are not necessarily an indication of vertical movements or structural distress. Factors that contribute to the amount of shrinkage that takes place in a slab-on-grade 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 Association, flatwork formed of high-slump concrete (high water/cement,^atio) c Property Development Centers July 31, 2012 La Costa Town Square Commercial Development SCS&T Proposal No. 1111199-01R Carlsbad, California Page 11 utilizing 3/8-inch maximum size aggregate ("Pea Gravel Grout" mix) is likely to exhibit extensive shrinkage and cracking. Cracks most often occur in random patterns between construction joints. 4.4 EARTH RETAINING WALLS 4.4.1 Foundations The recommendations provided in the foundation section of this report are also applicable to earth retaining structures. 4.4.2 Passive Pressure The passive pressure for the retaining walls can be considered to be 300 psf per foot of depth up to a maximum of 1,500 psf. This pressure may be increased by Ys for seismic loading. The coefficient of friction for concrete to soil may be taken as 0.3 for resistance to lateral movement. When combining friction and passive resistance, the friction should be reduced by Vs. The upper 12 inches of soil in front of retaining wall footings should not be included in passive pressure calculations unless pavement extends adjacent to the footing. 4.4.3 Active Pressure The active soil pressure for the design of unrestrained earth retaining structures with level backfills can be taken as equivalent to the pressure of a fluid weighing 40 pounds per cubic foot (pcf). An additional 20 pcf should be added for walls with sloping backfills of 2:1(horizontal:vertical) or flatter. A granular and drained backfill condition has been assumed. Surcharge loads from vehicles can be taken into account by assuming an additional 2 feet of soil is supported by the wall. If any other surcharge loads are anticipated, SCS&T should be contacted for the necessary increase in soil pressure. The project architect should provide waterproofing specifications and details. A typical wall backdrain detail is shown on Figure 7. 4.4.4 At-Rest Pressure The at-rest soil pressure for the design of restrained earth retaining structures with level backfills can be taken as equivalent to the pressure of a fluid weighing 60 pcf. An additional 20 pcf should be added for walls with sloping backfills of 2:1(horizontal:vertical) or flatter. A granular and drained backfill condition has been assumed. If any surcharge loads are anticipated, SCS&T should be contacted for the necessary increase in soil pressure. 4.4.5 Seismic Earth Pressure The seismic earth pressures can be taken as an inverted triangular distribution with a maximum pressure at the top equal to 16H pounds per square foot (with H being the height of the retained earth in feet). This pressure is in addition to the un-factored statb-t^sign Property Development Centers La Costa Town Square Commercial Development Carlsbad, California July 31, 2012 SCS&T Proposal No. 1111199-01R Page 12 wall load. The allowable passive pressure and bearing capacity can be increased by Vz in determining the stability of the wall. 4.4.6 Waterproofing and Backdrain Observation The geotechnical engineer should be requested to verify that waterproofing has been applied and that the backdrain has been properiy installed. However, unless specifically asked to do so, we will not verify proper application of the waterproofing. SCS&T does have a waterproofing division that can provide this service if requested. 4.4.7 Backfill All backfill soils should be compacted to at least 90 percent relative compaction. Expansive or clayey soils should not be used for backfill material. The wall should not be backfilled until the grout has reached an adequate strength. 4.4.8 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. 4.5 MSE WALL DESIGN PARAMETERS The following soil parameters can be used for the design of Mechanically Stabilized Earth (MSE) walls. Table 3 Mechanically Stabilized Earth Wall Design Parameters Reinforced Soil Retained Soil Foundation Soil Internal Friction Angle (degrees) 30° 30° 30° Cohesion (pounds per square foot) 0 0 0 Moist Unit Weight (pounds per cubic foot) 130 130 130 4.6 PAVEMENT SECTION RECOMMENDATIONS The pavement support characteristics of the soils encountered during our investigation range from poor to good. It is anticipated that these deposits will be mixed and the resulting blend will have moderately good pavement support characteristics. An "R" value of 25 was assumed for this blend. The actual "R" value of the subgrade soils will be determined after grading. Based on an "R" value of 25, the following structural sections are recommended for the assumed Traffic Indices. Property Development Centers La Costa Town Square Commercial Development Carlsbad, California July 31, 2012 SCS&T Proposal No. 1111199-01R Page 13 Table 4 Flexible Pavement Recommendations Traffic Index Asphalt Concrete (inches) Aggregate Base^ (inches) 6.0 4 9 7.5 5 12 Note 1: AB shall conform to Class 2 Aggregate Base in Section 26-1.02 ofthe Standard Specifications of The State of California Department of Transportation or Crushed Miscellaneous Base In accordance with the Standard Specifications for Public Works and City of Carlsbad Standards. Based on an "R"-Value of 25 the following rigid pavement sections are recommended for the Traffic Index presented below. Table 5 Traffic Type Traffic Index JPCP*/Aggregate Base^ (Inches) Parking Stalls 6.0 6/6 Drive Lanes 7.5 6/6 'Jointed Plain Concrete Pavement. Note 1: AB shall conform to Class 2 Aggregate Base In Section 26-1.02 of the Standard Specifications of The state of California Department of Transportation or Crushed Miscellaneous Base in accordance with the Standard Specifications for Public Works and City of Carlsbad Standards. Bus turnouts should be constructed in accordance with the San Diego Regional Standard Drawings SDG-109, 9 inches of concrete underiain by at least 12 inches of aggregate base. The concrete should have a compressive strength of at least 3250 pounds per square inch. SDG&E concrete maintenance areas should have a concrete thickness of at least 714 inches underiain by at least 12 inches of aggregate base. Trash enclosures should have a thickness of at least 714 and be underiain by at least 12 inches of aggregate base. The upper 12 inches of subgrade should be scarified, moisture conditioned to above optimum moisture requirements, and compacted to at least 95% of the maximum dry density. All soft or spongy areas should be excavated and replaced with compacted fill. The base material should be compacted to at least 95% of its maximum dry density. All materials and methods of construction should conform to good engineering practices and the minimum standards set forth by the City of Carisbad. 4.7 INFILTRATION RATES The underiying earthen materials are comprised of impermeable clay and rock. Infiltration rates will be dependent on the materials placed during mass grading operations. The project civil Property Development Centers July 31, 2012 La Costa Town Square Commercial Development SCS&T Proposal No. 1111199-01R Carlsbad, Califomia Page 14 engineer should design permeable surfaces to collect surface water and direct it toward appropriate drainage facilities. 5. GEOTECHNICAL ENGINEERING DURING CONSTRUCTION The geotechnical engineer should review project plans and specifications prior to bidding and construction to check that the intent of the recommendations in this report has been incorporated. Observations and tests should be performed during construction. If the conditions encountered during construction differ from those anticipated based on the subsurface exploration program, the presence of the geotechnical engineer during construction will enable an evaluation of the exposed conditions and modifications of the recommendations in this report or development of additional recommendations in a timely manner. 6. CLOSURE SCS&T should be advised of any changes in the project scope so that the recommendations contained in this report can be evaluated with respect to the revised plans. Changes in recommendations will be verified in writing. The findings in this report are valid as of the date of this report. Changes in the condition of the site can, however, occur with the passage of time, whether they are due to natural processes or work on this or adjacent areas. In addition, changes in the standards of practice and government regulations can occur. Thus, the findings in this report may be invalidated wholly or in part by changes beyond our control. This report should not be relied upon after a period of two years without a review by us verifying the suitability ofthe conclusions and recommendations to site conditions at that time. In the performance of our professional services, we comply with that level of care and skill ordinarily exercised by members of our profession currently practicing under similar conditions and in the same locality. The client recognizes that subsurface conditions may vary from those encountered at the boring locations, and that our data, interpretations, and recommendations are based solely on the information obtained by us. We will be responsible for those data, interpretations, and recommendations, but shall not be responsible for interpretations by others of the information developed. Our services consist of professional consultation and observation only, and no warranty of any kind whatsoever, express or implied, is made or intended in connection with the work performed or to be performed by us, or by our proposal for consulting or other services, or by our furnishing of oral or written reports or findings. SOUTHERN CALIFORNIA SOIL & TESTING, INC. SITE VICINIP^ MAP lA COSTA TOWN SOUARE COMMERCIAL Date: By: Job No. Scale: 12/23/2011 AKN 1111199-1 Not To Scale Figure: 1 OVERSIZE ROCK FILL PLACEMENT 1.5 eet;.\p-^:y-!^;rv;;:'r]^^^ y~\ y~\ ZONED ZONE A: Compacted soil fill. No rock fragments over 3 inches in any dimension. ZONE B: Compacted soil fill. No rock fragments over 6 Inches in any dimension. ZONE C: No rock fragments over 2 feet in any dimension. Uniformly distributed and well spaced in compacted soil fill. ZONE D: No rock fragments over 4 feet in any dimension. Uniformly distributed and well spaced in compacted soil fill. Note 1: Compacted soil fill should contain at least 40% soil finer than J Inch sieve (by Weight) and be compacted to at least 90% relative compaction. Note 2: Rocks over 4 feet in maximum dimension are not permitted in fill. SOUTHERN CALIFORNIA SOIL & TESTING, INC, OVERSIZE ROCK DISPOSAL lA COSTA TOWN SQUARE - COMMERICAL Date: By: Job No. Scale: 4/16/2012 EL 1111199-1 Not To Scale Figure: 4 Revised Typical Windrow Detail (End View) Horizontal Placed Compacled Rll 6- to 8-incti lids Granular soil ttoocled lo till voids- Typical Windrow Detail (Profile View) OVERSIZE ROCK DISPOSAL (Structral Soil - Rock Fill) -P/L- ^M^^^^^^S^ONE B O/l-O^O^W^H^O^oZONECo^O^O^ 4' MlN-n LEGEND NOTES: 1. Compacted soil fill shall contain at least 40% soil size passing | inch sieve, (by weight), and be compacted at least 90% relative compaction. 2. Rocks over 4 feel in maximum dimension not permitted in fill. ZONE A: Compacted soil fill. No rock fragments over 3 inches in any dimension. ZONE B: Compacted soil 1 No rock fragments over 6 inches in any dimension. ZONE C: No rock fragments over 2 feet in any dimension. Uniformly distributed and well spaced in compacted soil fill. ZONE D: No rock fragments over 4 feet in any dimension. Uniformly distributed and well spaced in compacted soil flit. ZONE E; Required for all existing slopes 5:1 and steeper. At least 90% comapction Zone A or B material can be used. I cn CD Q. CQ C SOUTHERN CALIFORNIA SOIL & TESTING, INC. OVERSIZE ROCK DISPOSAL LA COSTA TOWN SQUARE - COMMERICAL Date: By: Job No.: Scale: 4/16/2012 EL 1111199-1 Not To Scale I I I I \ CANYON SUBDRAIN DETAIL / Natural Ground Benching Remove Unsuitable Material ^ii- Ocj Subgrain Trench: See Details A and B I DETAIL A Perforated Pipe Surrounded with Filter Material Filter Material 6 cubic feeVfoot -Cover Perforated Pipe* Filter Material Shall be Class 2 permeable material per Section 68 of CALTRANS standard specifications, or approved alternate. I I DETAIL B f inch open-graded gravel wrapped in filter fabric (Mirafi 140N or equivalent) 6" minimum overlap Detail B-1 — Filter Material —(Mirafi MON or approved equivalent) Perforated Pipe f inch open graded gravel or equivalent 6 cubic feet/foot Detail B-2 (for fills over 35' deep) DETAIL of Canyon Subdrain Outlet Design Finish Grade •20' MIN-Is" Mill -Non-perforated Pipe* - j Perforated Pipe*- SUBDRAIN INSTALLATION Subdrain pipe shall be installed with perforation down. SUBDRAIN PIPE Subdrain pipe shall be PVC or ABS, type SDR35 for fills up to 35 feet deep, or type SDR21 for fills up to 100 feet deep. * MINIMUM DIAMETER 4" min = 0 - 500' Drain. 6" min = 500- 1,000 Drain 8" min = 1,000+ Drain SUBGRADIN DETAIL Date: 1/1/2012 Figure: jn SOUTHERN CALIFORNIA gg^S01L& TESTING, INC. By: EL Figure: jn SOUTHERN CALIFORNIA gg^S01L& TESTING, INC. lA COSTA TOWN SQUARE -Job No.: 1111199-1 jn SOUTHERN CALIFORNIA gg^S01L& TESTING, INC. COMMERICAL Scale: Not To Scale 6 Miradrain 6000 or Equivalent 1 - Filter fabric between rock and soli. 2 - Backcut as recommended in accordance with CALOSHA 3 - Waterproof back of wall. 4 - A 4-inch minmum diameter perforated pipe, SDR35 or equivalent, holes c 1% fall to outlet, encased in 3/4" crushed rock. Provide 3 cubic feet per lineal foot of crushed rock minimum. Crushed rock to be surrounded by filter fabric (Mirafi HON or equivalent), with a 6-inch minumum overiap. Provide solid outlet pipe at suitable location. 5 - 3/4-inch crushed rock SOUTHERN CAUFORNIA SOIL & TESTING, INC. WALL. BACKDRAIN L^.COSTA.TOWN.SQUARE.-.COMMERCIAL Date: By: Job No. Scale: 4/16/2011 GBF 1111199-01 NOTTOSCALE Figure: 7 APPENDIX I APPENDIX I FIELD INVESTIGATION Seven exploratory test trenches were excavated and 4 test borings were drilled at the locations shown on Figure 2. The fieldwork was performed under the observation of our geology personnel, who also logged the trenches/borings and obtained samples of the materials encountered. The logs are presented on Figures 1-2 through 1-15. Soils are classified in accordance with the Unified Soil Classification System illustrated on Figure 1-1. SiC SUBSURFACE EXPLORATION LEGEND UNIFIED SOIL CLASSIFICATION CHART SOIL DESCRIPTION GROUP SYMBOL TYPICAL NAMES I. COARSE GRAINED, more than 50% of material is larger than No. 200 sieve size. CLEAN GRAVELS GW Well graded gravels, gravel-sand mixtures, little or no fines GP Poorly graded gravels, gravel sand mixtures, little or no fines. GRAVELS More than half of coarse fraction is larger than No. 4 sieve size but smaller than 3". GRAVELS WITH FINES GM Silty gravels, poorly graded gravel-sand-silt mixtures. (Appreciable amount of fines) GC Clayey gravels, poorly graded gravel-sand-clay mixtures. SANDS More than half of coarse fraction is smaller than No. 4 sieve size. CLEAN SANDS SW Well graded sand, gravelly sands, little or no fines. SP Poorly graded sands, gravelly sands, little or no fines. SANDS WITH FINES SM Silty sands, poorly graded sand and silty mixtures. (Appreciable amount of fines) SC Clayey sands, poorly graded sand and clay mixtures. il. FINE GRAINED, more than 50% of material is smaller than No. 200 sieve size. SILTS AND CLAYS (Liquid Limit less than 50) |^|_ Inorganic silts and very fine sands, rock flour, sandy silt or clayey-silt- sand mixtures with slight plasticity. Ql_ Inorganic clays of low/ to medium plasticity, gravelly clays, sandy clays, silty clays, lean clays. OL Organic silts and organic silty clays of low plasticity. SILTS AND CLAYS (Liquid Limit greater than 50) 1^1^ Inorganic silts, micaceous or diatomaceous fine sandy or silty soils, elastic silts. CH Inorganic clays of high plasticity, fat clays. OH Organic clays of medium to high plasticity. I. HIGHLY ORGANIC SOILS PT Peat and other highly organic soils. FIELD SAMPLE SYMBOLS £^><CJi - Bulk Sample CAL - Modified California penetration test sampler CK - Undisturbed chunk sample MS - Maximum Size of Particle • Water seepage at time of excavation or as indicated SPT - Standard penetration test sampler ST - Shelby Tube \/ - Water level at time of excavation or as indicated LABORATORY TEST SYMBOLS AL - Atterberg Limits CON - Consolidation COR - Corrosivity Test - Sulfate - Chloride - pH and Resistivity DS - Direct Shear El - Expansion Index MAX - Maximum Density RV - Rvalue SA - Sieve Analysis UC - Unconfined Compression SC SOUTHERN CALIFORNIA S T SOIL & TESTING, INC. LA COSTA TOWN SOUARE COMMERCIAL SC SOUTHERN CALIFORNIA S T SOIL & TESTING, INC. By: DAS Date: 1/4/2012 SC SOUTHERN CALIFORNIA S T SOIL & TESTING, INC. Job Number: 1111199-1 Figure: 1-1 LOG OF TEST TRENCH NUMBER T-1 Date Excavated: 12/9/2011 Logged by: AKN Equipment: Case 580L with 18-inch bucket Project Manager: GBF Surface Elevation (ft): 271 Depth to Water (ft): Seepage at 8 feet X I-D- UJ a CO o CO Z3 SUMMARY OF SUBSURFACE CONDITIONS SAMPLES UJ h- o o Q. 3 >- OH D - 2 - 4 - 6 - 8 - 10 - 12 - 14 - 16 - 18 L 20 SC FILL (Qaf) - Light brown, moist, loose, CLAYEY SAND. CL Medium brown, moist, medium stiff, SANDY CLAY with GRAVEL. sc Light grayish brown, moist, medium dense, CLAYEY SAND with GRAVEL. Boulders encountered below 7 feet. PRACTICAL REFUSAL AT 10 FEET ON BOULDERS. SOUTHERN CALIFORNIA ST SOIL & TESTING, INC. LA COSTA TOWN SQUARE COMMERCIAL SOUTHERN CALIFORNIA ST SOIL & TESTING, INC. By: AKN Date: 1/4/2012 SOUTHERN CALIFORNIA ST SOIL & TESTING, INC. Job Number: 1111199-1 Figure: 1-2 LOG OF TEST TRENCH NUMBER T-2 Date Excavated: 12/9/2011 Logged by: AKN Equipment: Case 580L with 18-inch bucket Project Manager: GBF Surface Elevation (ft): 329 Depth to Water (ft): Not observed X I- Q. UJ Q CO O CO 3 SUMMARY OF SUBSURFACE CONDITIONS SAMPLES UJ CC H CO o o CL 3 > a - 2 - 4 - 6 - 8 - 10 - 12 - 14 16 - 18 20 DELMAR FORMATION (Td) - Light brown and medium greenish gray, moist, very stiff to hard, SANDY CLAYSTONE. Light gray and brown, moist, dense to very dense, fine- to medium-grained, SILTY SANDSTONE. BOTTOM OF TEST TRENCH AT 8 FEET. NO GROUNDWATER OR SEEPAGE ENCOUNTERED. SOUTHERN CALIFORNIA ST SOIL & TESTING, INC. LA COSTA TOWN SQUARE COMMERCIAL SOUTHERN CALIFORNIA ST SOIL & TESTING, INC. By: AKN Date: 1/4/2012 SOUTHERN CALIFORNIA ST SOIL & TESTING, INC. Job Number: 1111199-1 Figure: 1-3 LOG OF TEST TRENCH NUMBER T-3 Date Excavated: 12/9/2011 Logged by: AKN Equipment: Case 580L with 18-inch bucket Project Manager: GBF Surface Elevation (ft): 320 Depth to Water (ft): Not observed SAMPLES "H (ft) CO O RBED ISTURE (%) NT. (pcf) >- DC O CO DERI CO 3 SUMMARY OF SUBSURFACE CONDITIONS )ISTU BUL ISTURE (%) 1- z LABORA TES1 z 3 O DRY L LABORA TES1 DELMAR FORMATION (Td) - Liqht reddish qrav, moist hard. \ 1 El -SANDY CLAYSTONE. \ - 2 - 4 h - 6 - 8 - 10 Light gray, moist, very dense, fine-grained, SILTY SANDSTONE. - 12 - 12 BOTTOM OF TEST TRENCH AT 12 FEET. NO GROUNDWATER OR SEEPAGE ENCOUNTERED. - 14 - 16 - 18 - 20 SOUTHERN CALIFORNIA ST SOIL & TESTING, INC. LA COSTA TOWN SQUARE COMMERCIAL SOUTHERN CALIFORNIA ST SOIL & TESTING, INC. By: AKN Date: 1/4/2012 SOUTHERN CALIFORNIA ST SOIL & TESTING, INC. Job Number: 1111199-1 Figure: 1-4 LOG OF TEST TRENCH NUMBER T-4 Date Excavated: 12/9/2011 Logged by: AKN Equipment Case 580L with 18-inch bucket Project Manager: GBF Surface Elevation (ft): 345 Depth to Water (ft): Not observed X I- CL UJ Q CO o CO 3 SUMMARY OF SUBSURFACE CONDITIONS SAMPLES UJ Cd 3 I- CO o o Q. 3 >-Cd a Cd O CO o ^ m < - 2 - 4 - 6 - 8 - 10 - 12 - 14 - 16 - 18 L- 20 DELMAR FORMATION (Td) - Light gray, moist, very stiff to hard, SANDY CLAYSTONE. Light brownish gray, moist, very dense, fine-grained, CLAYEY SANDSTONE. BOTTOM OF TEST TRENCH AT 14 FEET. NO GROUNDWATER OR SEEPAGE ENCOUNTERED. SOUTHERN CALIFORNIA ST SOIL & TESTING, INC. LA COSTA TOWN SQUARE COMMERCIAL SOUTHERN CALIFORNIA ST SOIL & TESTING, INC. By: AKN Date: 1/4/2012 SOUTHERN CALIFORNIA ST SOIL & TESTING, INC. Job Number: 1111199-1 Figure: 1-5 LOG OF TEST TRENCH NUMBER T-5 Date Excavated: 12/9/2011 Logged by: AKN Equipment: Case 580L with 18-inch bucket Project Manager: GBF Surface Elevation (ft): 358 Depth to Water (ft): Not observed X I-CL UJ Q CO o CO 3 SUMMARY OF SUBSURFACE CONDITIONS SAMPLES UJ Cd 3 h- CO o o Q. 3 > Cd Q >- Od O CO O ^ CQ < - 2 - 4 - 6 - 8 - 10 - 12 - 14 - 16 - 18 L 20 sc ARTIFICIAL FILL (Qaf) - Medium brown, moist, medium dense, CLAYEY SAND with GRAVEL. DELMAR FORMATION (Td) - Light orange brown, moist, dense to very dense, SILTY SANDSTONE. Gravel beds throughout. Light gray, moist hard, SANDY CLAYSTONE. BOTTOM OF TEST TRENCH AT 14 FEET. NO GROUNDWATER OR SEEPAGE ENCOUNTERED. g^ SOUTHERN CALIFORNIA ST SOIL & TESTING, INC. LA COSTA TOWN SQUARE COMMERCIAL g^ SOUTHERN CALIFORNIA ST SOIL & TESTING, INC. By: AKN Date: 1/4/2012 g^ SOUTHERN CALIFORNIA ST SOIL & TESTING, INC. Job Number: 1111199-1 Figure: 1-6 LOG OF TEST TRENCH NUMBER T-6 Date Excavated: 12/8/2011 Logged by: AKN Equipment: Case 580L with 18-inch bucket Project Manager: GBF Surface Elevation (ft): 258 Depth to Water (ft): Not observed X H CL UJ D CO o CO 3 SUMMARY OF SUBSURFACE CONDITIONS SAMPLES UJ Od 3 I- CO O o Q. 3 >- Cd Q - 2 - 6 - 8 - 10 - 12 14 - 16 - 18 L 20 ALLUVIUM (Qal) - Dark brown, very moist, soft, SANDY CLAY. Gravel encountered throughout. DELMAR FORMATION (Td) - Light grayish brown, moist, very stiff to hard, SANDY CLAYSTONE. BOTTOM OF TEST TRENCH AT 9 FEET. NO GROUNDWATER OR SEEPAGE ENCOUNTERED. g^ SOUTHERN CALIFORNIA ST SOIL & TESTING, INC. LA COSTA TOWN SQUARE COMMERCIAL g^ SOUTHERN CALIFORNIA ST SOIL & TESTING, INC. By: AKN Date: 1/4/2012 g^ SOUTHERN CALIFORNIA ST SOIL & TESTING, INC. Job Number: 1111199-1 Figure: 1-7 LOG OF TEST TRENCH NUMBER T-7 Date Excavated: 12/8/2011 Logged by: AKN Equipment: Case 580L with 18-inch bucket Project Manager: GBF Surface Elevation (ft): 269 Depth to Water (ft): Seepage at 8 feet X I- Q. UJ O CO o CO 3 SUMMARY OF SUBSURFACE CONDITIONS SAMPLES UJ Od 3 I- co o o Q. z 3 > Cd Q sc ARTIFICIAL FILL (Qaf) - Medium grayish brown, moist to very moist, stiff, SANDY CLAY. - 2 - 4 - 6 - 8 - 10 - 12 - 14 - 16 - 18 L 20 /"Light grayish brown, saturated, medium dense, CLAYEY / SAND with GRAVEL. Boulders encountered below 7 feet. Seepage encountered below 8 feet. PRACTICAL REFUSAL AT 9 FEET DUE TO TRENCH- WALL CAVING. g^ SOUTHERN CALIFORNIA S T SOIL & TESTING, INC. LA COSTA TOWN SQUARE COMMERCIAL g^ SOUTHERN CALIFORNIA S T SOIL & TESTING, INC. By: AKN Date: 1/4/2012 g^ SOUTHERN CALIFORNIA S T SOIL & TESTING, INC. Job Number: 1111199-1 Figure: 1-8 LOG OF EXPLORATORY BORING NUMBER B-1 Date Excavated: 3/18/2005 Logged by: MPF Equipment HSA (Ingersol-Rand A300) Project Manager DBA Surface Elevation (ft): 331 Depth to Water (ft): Not observed SAMPLES CO DEPTH (ft) USCS SUMMARY OF SUBSURFACE CONDITIONS UNDISTURBED BULK PENETRATION (blows/ ft. of drive) MOISTURE (%) DRY UNIT WT. (pcf) LABORATORY TESl DELMAR FORMATION (Td) - Rust to qravish-brown. moist, humid. -SANDY CLAYSTONE. Not - 2 suitable capping material X - 4 - 6 - 8 X - 10 - 10 Gray with rust mottling, moist, hard/dense, SILTY SANDSTONE. Suitable capping material - 12 - 14 X - 16 SPT 57 - 18 X - 20 SC ST SOUTHERN CALIFORNIA SOIL & TESTING, INC. LA COSTA TOWN SQUARE COMMERCIAL By: DB/VSD Job Number: 1111199-1 Date: 4/6/2005 Figure: 1-9 LOG OF EXPLORATORY BORING NUMBER B-1 (continued) Date Excavated: 3/18/2005 Logged by: MPF Equipment: HSA (Ingersol-Rand A300) Project Manager: DBA Surface Elevation (ft): 331 Depth to Water (ft): Not observed X H D. LU Q CO O CO 3 SUMMARY OF SUBSURFACE CONDITIONS SAMPLES O c -a o o LU Cd 3 I- co O o CL Z 3 >- Od Q CO I-co LU h- > Od O I-< Cd o CQ < - 22 24 - 26 - 28 - 30 32 - 34 h 36 s - 40 l_ 41 Gray with rust mottling, moist, hard/dense, SILTY SANDSTONE. Suitable capping material 23': Slight color change, more rust iron oxide staining SPT 50/4" Gradational contact 33' - 35'+ Dark olive to grayish-bia'c'^ moist7humid,'SANbY'cLAY^ Not suitable capping material @ 40': Numerous shell fragments, high decayed organic content in sample SPT 60/3" BOTTOM OF BORING AT 41 FEET. NO GROUNDWATER OR SEEPAGE ENCOUNTERED. SOUTHERN CALIFORNIA SOIL & TESTING, INC. LA COSTA TOWN SQUARE COMMERCIAL SOUTHERN CALIFORNIA SOIL & TESTING, INC. By: DB/VSD Date: 4/6/2005 SOUTHERN CALIFORNIA SOIL & TESTING, INC. Job Number: 1111199-1 Figure: 1-10 LOG OF EXPLORATORY BORING NUMBER B-2 Date Excavated: Equipment: Surface Elevation (ft): 3/18/2005 HSA (Ingersol-Rand A300) 305 Logged by: Project Manager: Depth to Water (ft): MPF DBA Not observed Q- UJ Q CO O CO 3 SUMMARY OF SUBSURFACE CONDITIONS SAMPLES i I o 0:^ LU Cd 3 h- CO O o CL 3 >-Cd a CO I-co LU I- > Od O H < Cd o CQ < - 2 - 4 - 6 - 8 - 10 - 12 - 14 - 16 - 20 •s - 23 DELMAR FORMATION (Td) - Gray with rust, moist, hard/dense. SILTY SANDSTONE. Suitable capping material Gray to maroon, moist hard, SANDY SILTSTONE. Suitable capping material E Dark orange-brown to dark grayish-brown, moist, hard, SANDY CLAYSTONE. Not suitable capping material Concretion at 12.5'+, difficult drilling X SPT 50/5" Dark blackish-gray 20': Hard cemented siltstone in sample tip SPT 50/4" AUGER REFUSAL AT 23 FEET. NO GROUNDWATER OR SEEPAGE ENCOUNTERED. g^ SOUTHERN CALIFORNIA ST SOIL & TESTING, INC. LA COSTA TOWN SQUARE COMMERCIAL By: DB/VSD Job Number: 1111199-1 Date: 4/6/2005 Figure: 1-11 LOG OF EXPLORATORY BORING NUMBER B-3 Date Excavated: Equipment: Surface Elevation (ft): 3/18/2005 HSA (Ingersol-Rand A300) 311 Logged by: Project Manager: Depth to Water (ft): MPF DBA Not observed X I-Q. LU Q CO O CO 3 SUMMARY OF SUBSURFACE CONDITIONS SAMPLES UJ Cd 3 I- co o o Q. 3 >- Cd Q CO I- co LU I-> Cd o I-< Cd o CQ < - 2 - 4 - 6 - 8 - 10 - 12 - 14 - 16 - 18 L 20 DELMAR FORMATION (Td) - Gray with rust, moist, hard/dense. SILTY SANDSTONE. Suitable capping material X Green to dark grayish-brown Dark blackish-gray, moist, hard, SANDY CLAYSTONE. Not suitable capping material X PRACTICAL REFUSAL AT 15 FEET. NO GROUNDWATER OR SEEPAGE ENCOUNTERED. g^ SOUTHERN CALIFORNIA ST SOIL & TESTING, INC. LA COSTA TOWN SQUARE COMMERCIAL g^ SOUTHERN CALIFORNIA ST SOIL & TESTING, INC. By: DB/VSD Date: 4/6/2005 g^ SOUTHERN CALIFORNIA ST SOIL & TESTING, INC. Job Number: 1111199-1 Figure: 1-12 LOG OF EXPLORATORY BORING NUMBER B-4 Date Excavated: 3/18/2005 Logged by: MPF Equipment: HSA (Ingersol-Rand A300) Project Manager: DBA Surface Elevation (ft): 352 Depth to Water (ft): Seepage at 34 feet SAMPLES LABORATORY TESTS DEPTH (ft) USCS SUMMARY OF SUBSURFACE CONDITIONS UNDISTURBED BULK PENETRATION (blows/ ft. of drive) MOISTURE (%) DRY UNIT WT. (pcf) LABORATORY TESTS ASPHALT CONCRETE OVER AGGREGATE BASE DELMAR FORMATION (Td) - Olive to mauve with sulphur yellow - 2 seams, very moist, stiff, SANDY CLAYSTONE. - 4 Not suitable capping material X - 6 - 8 X - 10 - 12 - 14 - 16 SPT 28 - 18 - 20 g^ SOUTHERN CALIFORNIA ST SOIL & TESTING, INC. LA COSTA TOWN SQUARE COMMERCIAL g^ SOUTHERN CALIFORNIA ST SOIL & TESTING, INC. By: DB/VSD Date: 4/6/2005 g^ SOUTHERN CALIFORNIA ST SOIL & TESTING, INC. Job Number: 1111199-1 Figure: 1-13 LOG OF EXPLORATORY BORING NUMBER B-4 (continued) Date Excavated: 3/18/2005 Logged by: MPF Equipment HSA (Ingersol-Rand A300) Project Manager: DBA Surface Elevation (ft): 352 Depth to Water (ft): Seepage at 34 feet X h- CL UJ Q CO o CO 3 SUMMARY OF SUBSURFACE CONDITIONS SAMPLES CD > "O "o In o LU Cd 3 I- CO O o Q. Cd Q CO I- co UJ I- >- Cd O I-< 01 o CQ < 22 24 - 26 - 28 30 - 32 - 34 - 36 - 38 L 40 Contact at 20'+, distinct change in cuttings Gray'with'Tusrmoistliard/d'eTrsersILTY SANDSTONE. Suitable capping material Occasional SANDY CLAYSTONE layers. May not be suitable capping material SPT 75 Light water seepage at 34' Dark yellowish-brown, moist very hard, SILTSTONE. Suitable capping material Grades to SANDY CLAYSTONE. Not suitable capping material SOUTHERN CALIFORNIA SOIL & TESTING, INC. LA COSTA TOWN SQUARE COMMERCIAL SOUTHERN CALIFORNIA SOIL & TESTING, INC. By: DB/VSD Date: 4/6/2005 SOUTHERN CALIFORNIA SOIL & TESTING, INC. Job Number: 1111199-1 Figure: 1-14 LOG OF EXPLORATORY BORING NUMBER B-4 (Continued) Date Excavated: 3/18/2005 Logged by: MPF Equipment: HSA (Ingersol-Rand A300) Project Manager: DBA Surface Elevation (ft): 352 Depth to Water (ft): Seepage at 34 feet DEPTH (ft) USCS SUMMARY OF SUBSURFACE CONDITIONS SAMPLES PENETRATION (blows/ ft. of drive) MOISTURE (%) DRY UNIT WT. (pcf) LABORATORY TESTS DEPTH (ft) USCS SUMMARY OF SUBSURFACE CONDITIONS UNDISTURBED BULK PENETRATION (blows/ ft. of drive) MOISTURE (%) DRY UNIT WT. (pcf) LABORATORY TESTS - 42 • 44 -46 SPT 50/5" - 42 • 44 -46 Tan to gray to rust, moist hard, SILTSTONE. Suitable capping material SPT 50/5" AUGER REFUSAL AT 47 FEET. (COBBLE OR SANTIAGO - 48 PEAK VOLCANICS ?). - 50 - 52 - 54 - 56 -58 - 60 SC ST SOUTHERN CALIFORNIA SOIL & TESTING, INC. LA COSTA TOWN SQUARE COMMERCIAL By: DB/VSD Job Number: 1111199-1 Date: 4/6/2005 Figure: 1-15 APPENDIX II APPENDIX II LABORATORY TESTING SUMMARY Laboratory tests were performed to provide geotechnical parameters for engineering analyses. The following tests were conducted: • CLASSIFICATION: Field classifications were verified in the laboratory by visual examination. The final soil classifications are in accordance with the Unified Soil Classification System. • EXPANSION INDEX TESTS: One expansion index tests was performed in accordance with ASTIVl D 4289. The result of these tests is presented on Figure 11-1. Soil samples not tested are now stored in our laboratory for future reference and analysis, if needed. Unless notified to the contrary, all samples will be disposed of 30 days from the date of this report. EXPANSION INDEX ASTM- D4829 SAMPLE DESCRIPTION EXPANSION INDEX T-3 at 0'-5' Medium brown, CLAYEY SAND 111 T-5 at 0'-5' Medium brown, CLAYEY SAND 44 B-1 at 8' to 9' Grayish brown, sandy clay 104 B-2 at 6' to T Grayish, sandy clay 60 B-1 at 23' to 25' Grayish, sandy clay 54 CLASSIFICATION OF EXPANSIVE SOIL EXPANSION INDEX POTENTIAL EXPANSION 0-20 Very Low 21 -50 Low 51 -90 Medium 91 - 130 High Above 130 Very High SC SOUTHERN CALIFORNIA ST SOIL & TESTING, INC. LA COSTA TOWN SQUARE - COMMERCIAL SC SOUTHERN CALIFORNIA ST SOIL & TESTING, INC. By: DAS/GBF Date: 1/4/12 SC SOUTHERN CALIFORNIA ST SOIL & TESTING, INC. Job Number: 1111199-1 Figure: 11-1 APPENDIX (COMMERCIAL 1111199-01) SiC sh- SEISMIC REFRACTION SURVEY LA COSTA TOWN CENTER CARLSBAD, CALIFORNIA PREPARED FOR: Southem Califomia Soil & Testing 6280 Riverdale Street San Diego, CA 92120 PREPARED BY: Southwest Geophysics, Inc. 8057 Raytheon Road, Suite 9 San Diego, CA92111 December 29, 2011 ProjectNo. 111399 SOUTHWeST GEOPHYSICS, INC. YOUR SUBSURFACE SOLUTION December 29, 2011 ProjectNo. 111399 Mr. Doug Skinner Southem Califomia Soil & Testing 6280 Riverdale Street San Diego, CA 92120 Subject: Seismic Refraction Survey La Costa Town Center Carlsbad, Califomia Dear Mr. Skinner: In accordance with your authorization, we have performed a seismic refraction survey pertaining to the proposed La Costa Town Center project located along Rancho Santa Fe Road in Carlsbad, Califomia. Specifically, our survey consisted of performing 10 seismic refraction lines at the subject site. The purpose of the sUidy was to develop subsurface velocity profiles ofthe project area and to evaluate the apparent rippability of the shallow subsurface materials. This report pre- sents our survey methodology, equipment used, analysis, and results from our survey. We appreciate the opportunity to be of service on this project. Should you have any questions related to this report, please contact the undersigned at your convenience. Sincerely, SOUTHWEST GEOPHYSICS, INC. y Patrick Lehrmann, P.G., R.Gp. Principal Geologist/Geophysicist HV/PFL/hv Distribution: Addressee (electronic) Hans van de Vmgt, C.E.G, R.Gp. Principal Geologist/Geophysicist 8057 Raytheon Road, Suite 9 • SanOiego • California 92111 • Telephone 858-527-0849 • Fax 858-225-0114 La Costa Town Center December 29, 2011 Carlsbad, Califomia Project No. 111399 TABLE OF CONTENTS Page 1. INTRODUCTION 1 2. SCOPE OF SERVICES 1 3. SITE AND PROJECT DESCRIPTION 1 4. SURVEY METHODOLOGY 1 5. RESULTS 3 6. CONCLUSIONS AND RECOMMENDATIONS 4 7. LIMITATIONS 5 8. SELECTED REFERENCES 6 Tables Table 1 - Rippability Classification 3 Table 2 - Seismic Traverse Results 3 Figures Figure 1 - Site Location Map Figure 2 - Line Location Map Figure 3a - Site Photographs (SL-1 to SL-4) Figure 3b - Site Photographs (SL-5 to SL-7) Figure 3c - Site Photographs (SL-8 to SL-10) Figure 4a - Seismic Profiles, SL-1 and SL-2 Figure 4b - Seismic Profiles, SL-3 and SL-4 Figure 4c - Seismic Profiles, SL-5 and SL-6 Figure 4d - Seismic Profiles, SL-7 and SL-8 Figure 4e - Seismic Profiles, SL-9 and SL-10 La Costa Town Center December 29, 2011 Carlsbad, Califomia Project No. 111399 1. INTRODUCTION In accordance with your authorization, we have performed a seismic refraction survey pertaining to the proposed La Costa Town Center project located along Rancho Santa Fe Road in Carlsbad, Califomia (Figure 1). Specifically, our survey consisted of performing 10 seismic refraction lines at the subject site. The purpose of the study was to develop subsurface velocity profiles of the project area and to evaluate the apparent rippability of the shallow subsurface materials. This re- port presents our survey methodology, equipment used, analysis, and results from our survey. 2. SCOPE OF SERVICES Our scope of services for this study included: • Performance of 10 seismic refraction lines at the project site. • Compilation and analysis of the data collected. • Preparation of this report presenting our results, conclusions, and recommendations. 3. SITE AND PROJECT DESCRIPTION The study area is located along the south side of Rancho Santa Fe Road, near its intersection with Paseo Lupino in the Carlsbad area of San Diego (Figure 1). The site is generally undeveloped with the exception of a few dirt roads which transect the site. Topography consists of relatively gentle slopes. Vegetation consists of annual grass and bmsh. Figures 2 and 3a through 3c depict the general site conditions in the area of the refraction lines. It is our understanding that resi- dences may be constmcted at the site and that cuts up to 45 feet may be performed during grading. 4. SURVEY METHODOLOGY A seismic P-wave (compression wave) refraction survey was conducted at the site to evaluate the rippability characteristics of the subsurface materials and to develop a subsurface velocity profile of the site. The seismic refraction method uses first-arrival times of refracted seismic waves to estimate the thicknesses and seismic velocities of subsurface layers. Seismic P-waves generated at the surface, using a hammer and plate, are refracted at boundaries separating materials of con- trasting velocities. These refracted seismic waves are then detected by a series of surface vertical La Costa Town Center December 29, 2011 Carlsbad, Califomia Project No. 111399 component geophones, and recorded with a 24-channel Geometries Strata View seismograph. The travel times of the seismic P-waves are used in conjunction with the shot-to-geophone dis- tances to obtain thickness and velocity information on the subsurface materials. Ten seismic lines/profiles (SL-1 through SL-IO) were conducted at the site as part of this study. The ap- proximate locations of the lines are depicted on Figure 2. Shot points (signal generation locations) were conducted at each end of the line and at the midpoint. The lines were 150 feet long and the general locations were selected by your office. The refraction method requires that subsurface velocities increase with depth. A layer having a velocity lower than that of the layer above will generally not be detectable by the seismic refrac- tion method and, therefore, could lead to errors in the depth calculations of subsequent layers. In addition, lateral variations in velocity, such as those caused by core stones/outcrops, can also re- sult in the misinterpretation of the subsurface conditions. In general, seismic wave velocities can be correlated to material density and/or rock hardness. The relationship between rippability and seismic velocity is empirical and assumes a homoge- nous mass. Localized areas of differing composition, texture, and/or stmcture may affect both the measured data and the actual rippability of the mass. The rippability of a mass is also dependent on the excavation equipment used and the skill and experience of the equipment operator. The rippability values presented in Table 1 are based on our experience with similar materials and assumes that a Caterpillar D-9 dozer ripping with a single shank is used. We emphasize that the cutoffs in this classification scheme are approximate and that rock characteristics, such as fracture spacing and orientation, play a significant role in determining rock rippability. These characteristics may also vary with location and depth. For trenching operations, the rippability values should be scaled downward. For example, veloci- ties as low as 3,500 feet/second may indicate difficult ripping during trenching operations. In addition, the presence of boulders, which can be troublesome in a narrow trench, should be an- ticipated. La Costa Town Center Carlsbad, Califomia December 29, 2011 ProjectNo. 111399 Table 1 - Rippability Classification Seismic P-wave Velocity Rippability 0 to 2,000 feet/second Easy 2,000 to 4,000 feet/second Moderate 4,000 to 5,500 feet/second Difficult, Possible Blasting 5,500 to 7,000 feet/second Very Difficult Probable Blasting Greater than 7,000 feet/second Blasting Generally Required It should be noted that the rippability cutoffs presented in Table 1 are slightly more conservative than those published in the Caterpillar Performance Handbook (Caterpillar, 2004). Accordingly, the above classification scheme should be used with discretion; and contractors should not be relieved of making their own independent evaluation of the rippability of the on-site materials prior to submitting their bids. 5. RESULTS Table 2 lists the average P-wave velocities and depths calculated from the seismic refraction traverses conducted during our evaluation. The approximate locations of the seismic refraction traverses are shown on the Line Location Map (Figure 2). Layer velocity profiles are also in- cluded in Figures 4a through 4e. Please note the vertical scale changes for the profiles. It should also be noted that, as a general mle, the effective depth of evaluation for a seismic refraction traverse is approximately one-third to one-fifth the length of the refraction line. The lengths of the seismic refraction lines are listed with their interpretations in Table 2. Table 2 - Seismic Traverse Results Traverse No. And Length P-wave Velocity feet/second Approximate Depth to Bottom of Layer in feet Rippability* SL-1 150 feet VI = 1,615 V2 = 3,475 V3 = 6,795 1-5 7-16 Easy Moderate Very Difficult Probable Blasting SL-2 150 feet VI = 1,355 V2 = 7,050 12-19 Easy Blasting Generally Required SL-3 150 feet VI = 1,820 V2 = 7,640 8-17 Easy Blasting Generally Required La Costa Town Center Carlsbad, Califomia December 29, 2011 ProjectNo. 111399 Table 2 - Seismic Traverse Results Traverse No. And Length P-wave Velocity feet/second Approximate Depth to Bottom of Layer in feet Rippability* SL-4 150 feet VI = 1,325 V2 = 6,115 12-17 Easy Very Difficult, Probable Blasting SL-5 150 feet VI = 1,310 V2 = 7,190 16-19 Easy Blasting Generally Required SL-6 150 feet VI = 1,250 V2 = 9,370 17-21 Easy Blasting Generally Required SL-7 150 feet VI = 1,365 V2 = 8,080 21-28 Easy Blasting Generally Required SL-8 150 feet VI = 1,395 V2 = 7,535 18-27 Easy Blasting Generally Required SL-9 150 feet VI = 1,215 V2 = 3,500 V3 = 8,770 1-5 12-22 Easy Moderate Blasting Generally Required SL-10 150 feet VI = 1,340 V2 = 10,960 15-22 Easy Blasting Generally Required * Rippability criteria based on the use of a Caterpillar D-9 dozer ripping with a single shank 6. CONCLUSIONS AND RECOMMENDATIONS The results from this seismic survey revealed two to three distinct geologic layers at the locations surveyed. Based on our site observations and discussions with you, the study area is generally underlain by surficial soils (i.e., topsoil, colluvium, and/or fill) and crystalline bedrock with vary- ing degrees of weathering. The layer velocities measured for the surficial layers are generally consistent; however, the bedrock velocities vary across the site. Significant scatter was noted in the first-arrivals indicating the presence of inhomogeneities in the subsurface materials. These inhomogeneities may be due to buried core stones/remnant boul- ders, dikes, and/or differential weathering of the bedrock. Therefore, significant variability in the excavatability (including excavation depth) of the subsurface materials should be expected across the project area. A contractor with excavation experience in similar conditions should be consulted for expert advice on excavation methodology, equipment, production rate, and over- sized materials. La Costa Town Center December 29, 2011 Carlsbad, Califomia Project No. 111399 7. LIMITATIONS The field evaluation and geophysical analyses presented in this report have been conducted in general accordance with current practice and the standard of care exercised by consultants per- forming similar tasks in the project area. No warranty, expressed or implied, is made regarding the conclusions, recommendations, and opinions presented in this report. There is no evaluation detailed enough to reveal every subsurface condition. Variations may exist and conditions not observed or described in this report may be present. Uncertainties relative to subsurface condi- tions can be reduced through additional subsurface exploration. Additional subsurface surveying will be performed upon request. This document is intended to be used only in its entirety. No portion of the document, by itself, is designed to completely represent any aspect of the project described herein. Southwest Geophys- ics, Inc. should be contacted if the reader requires additional information or has questions regarding the content, interpretations presented, or completeness of this document. This report is intended exclusively for use by the client. Any use or reuse of the findings, conclusions, and/or recommendations of this report by parties other than the client is undertaken at said parties' sole risk. La Costa Town Center December 29, 2011 Carlsbad, Califomia Project No. 111399 8. SELECTED REFERENCES Caterpillar, Inc., 2004, Caterpillar Performance Handbook, Edition 35, Caterpillar, Inc., Peoria, Illinois. Mooney, H.M., 1976, Handbook of Engineering Geophysics, dated Febmary. Rimrock Geophysics, 2003, Seismic Refraction Interpretation Programs (SIPwin), V-2.76. Telford, W.M., Geldart, L.P., Sheriff, R.E., and Keys, D.A., 1976, Applied Geophysics, Cam- bridge University Press. El Cj»mirvo am Coi»itry Club Tn Crty Lake I ^-1 Monk VH18 Or Ocean H*» Coi^try CM) Calavera Hills, Viliafle Twin O Go»f ^— Agua ^ 1# HediorKJa ^7 O "5^ San Mar McCiellan Palorrsar Airport fid i Lake San Marcos i -5 I O Ol 5 H.1I Lagoon o .La Costa * Country Cfcjb San Efc|o Hilts La Costa Oaks So^mi KlgesAf Oliver>ha*i Brxiges / Rancho Santa Fe Emer at TN . San Eh/6 ^ Lagoon Rancho Santa Fe 62011 Google Solana 5 t? 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