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CT 2024-0001; TYLER STREET HOMES; FINAL GEOTECHNIAL INVESTIGATION REPORT; 2025-01-29
FINAL GEOTECHNICAL INVESTIGATION REPORT Tyler Street Homes 3215-3225 Tyler Street Carlsbad, California JOB NO. 23-14403 29 January 2024 Revised 06 March 2025 Prepared for: Mr. John Norum & Mr. Kirk Moeller i i 29 January 2024 (Revised 06 March 2025) Mr. John Norum Job No. 23-14403 Mr. Kirk Moeller KMJ Real Estate 2888 Loker Avenue East, Suite 220 Carlsbad, CA 92010 Subject: Final Geotechnical Investigation Report Tyler Street Homes 3215-3225 Tyler Street Carlsbad, California Dear Mr. Norum and Mr. Moeller: In accordance with your request and our work agreement of May 8, 2023, Geotechnical Exploration, Inc. has performed a final geotechnical investigation report for the subject project in Carlsbad, California. The field work was performed on August 17, 2023. If the conclusions and recommendations presented in this report are incorporated into the design and construction of the proposed residential building structures and associated improvements, it is our opinion that the site is suitable for the proposed project. This opportunity to be of service is sincerely appreciated. Should you have any questions concerning the following report, please do not hesitate to contact us. Reference to our Job No. 23-14403 will expedite a response to your inquiries. Respectfully submitted, GEOTECHNICAL EXPLORATION, INC. _______________________________ ______________________________ Leslie D. Reed, President Jaime A. Cerros, P.E. C.E.G. 999/P.G. 3391 R.C.E. 34422/G.E. 2007 Senior Geotechnical Engineer 4~~-Geotechnical Exploration, Inc. SOIL AND FOUNDATION ENGINEERING • GROUNDWATER • ENGINEERING GEOLOGY i . rros, . . ,-. ~ '"'\AA""\'"'\/,-.~ ""\r\.r\.~ 7420 TRADE STREET• SAN DIEGO, CA. 92121 • (858) 549-7222 • FAX: (858) 549-1604 • EMAIL: geotech@gei-sd.com TABLE OF CONTENTS I. PROJECT SUMMARY ............................................................................. 1 II. SCOPE OF WORK ................................................................................. 2 III. SITE DESCRIPTION .............................................................................. 3 IV. FIELD INVESTIGATION, OBSERVATIONS & SAMPLING .............................. 3 V. LABORATORY TESTING & SOIL INFORMATION ......................................... 4 VI. REGIONAL GEOLOGIC DESCRIPTION ...................................................... 8 VII. SITE-SPECIFIC SOIL & GEOLOGIC DESCRIPTION ..................................... 8 A. Stratigraphy ................................................................................ 9 B. Structure .................................................................................. 10 VIII. GEOLOGIC HAZARDS ......................................................................... 11 A. Local and Regional Faults ............................................................ 11 B. Other Geologic Hazards .............................................................. 13 IX. GROUNDWATER ................................................................................ 16 X. CONCLUSIONS & RECOMMENDATIONS ................................................. 18 A. Preparation of Soils for Site Development ...................................... 19 B. Seismic Design Criteria ............................................................... 25 C. Foundation Recommendations ..................................................... 26 D. Concrete Slab On-Grade Criteria .................................................. 29 E. Retaining Wall Design Criteria ...................................................... 31 F. Temporary Slopes ...................................................................... 34 G. Pavements ................................................................................ 34 H. Site Drainage Considerations ....................................................... 35 I. General Recommendations .......................................................... 36 XI. GRADING NOTES ............................................................................... 38 XII. LIMITATIONS .................................................................................... 38 REFERENCES FIGURES I. Vicinity Map II. Plot Plan with Site Specific Geologic Map IIIa-f. Exploratory Excavation Logs IVa-d. Laboratory Data V. Geologic Map Excerpt and Legend VI. Retaining Wall Drainage Schematic APPENDICES A. Unified Soil Classification System B. Regional Geologic Descriptions C. ASCE Seismic Summary Report D. Slab Moisture Information and Vapor Barrier Membranes E. Additional Geotechnical Documents FINAL GEOTECHNICAL INVESTIGATION REPORT Tyler Street Homes 3215-3225 Tyler Street Carlsbad, California JOB NO. 23-14403 The following report presents the findings and recommendations of Geotechnical Exploration, Inc. for the subject project. Refer to Figure No. I for the Vicinity Map. For purposes of this report, we refer to the front of the property as facing east toward Tyler Street. I. PROJECT SUMMARY It is our understanding, based on the review of a Site Plan prepared by Kirk Moeller Architects, dated January 15, 2024, that the existing single-story structures and adjacent parking area are to be removed to construct 12 three-story residential structures consisting of four triplexes and associated improvements. The new residential building structures are proposed to be constructed with standard- type building materials utilizing shallow isolated and continuous foundations. Foundation loads are expected to be typical for this type of relatively light construction. When final plans are completed, they should be made available for our review. Additional or modified recommendations will be provided at that time if warranted. The Geologic Map of the Oceanside 30'x60' Quadrangle, California by Kennedy and Tan, 2007, indicates that the subject site is located in an area underlain by Quaternary (late to middle Pleistocene) Old Paralic Deposits Unit 6-7 (Qop6-7) described as “Poorly sorted, moderately permeable, reddish-brown, interfingered strandline, beach, estuarine and colluvial deposits composed of siltstone, sandstone and conglomerate.” Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 2 Based on our current understanding of the proposed construction, it is our opinion that the proposed site development would not destabilize neighboring properties or induce the settlement of adjacent structures or right-of-way improvements if designed and constructed in accordance with our recommendations. It is also our opinion, based on our field investigation, review of pertinent geologic literature and analysis of geological maps, that neither an active nor a potentially active fault or landslide underlies the subject site. II. SCOPE OF WORK The scope of work performed for this investigation was based on the Site Plan prepared by Kirk Moeller Architects, Inc., dated June 5, 2023 (revised plan dated January 15, 2024). Our work included site observations and a subsurface exploration program under the direction of our geologist, with placement, logging and sampling of six (6) exploratory excavations utilizing hand tools and a thin-walled hand driven sampler. In addition, we reviewed available published information pertaining to site geology, evaluated the bearing characteristics of the encountered surficial fill and formational material, performed geotechnical engineering analysis of the field data, and prepared this report. The data obtained and the analyses performed were for the purpose of providing geotechnical design parameters, recommendations, and construction criteria for the development of the proposed new residential building structures and associated improvements. Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 3 III. SITE DESCRIPTION The site is known as Assessor’s Parcel No. 204-010-09-00, Lot 5 of Carlsbad Tract Map No. 1743, and is located at 3215–3225 Tyler Street in City of Carlsbad, California. The property is approximately 0.51-acre in size (22,345 square feet). The relatively level square lot slopes slightly to the northeast, with site elevations ranging from 44 feet above Mean Sea Level (MSL) at the along the eastern property line to approximately 46 feet above MSL at the western property. Elevations across the property were obtained from a Topographic Survey Map, dated August 3, 2023. The property is located at the western edge of Tyler Street in the City of Carlsbad. The rectangular-shaped lot is bordered on the north by a metal warehouse type building, on the south by a three-story storage building structure and on the west by an undeveloped lot. Vegetation on the site consists of residential landscape including mature trees, decorative shrubbery and lawn grass. Refer to Figure No. II, Plot Plan with Site-Specific Geologic Map. IV. FIELD INVESTIGATION, OBSERVATIONS & SAMPLING The field investigation consisted of a surface reconnaissance and a subsurface exploration program utilizing hand tools to investigate and sample the subsurface soils on August 17, 2023. Six exploratory hand pits (HP-1 to HP-6) were excavated where access allowed in the areas of the proposed new structures and associated improvements. The hand pits were excavated into medium dense to dense formational material to depths ranging from 2.5 to 5.5 feet in order to define the soil profile across the site and to obtain representative soil samples. The soils encountered in the hand pits were continuously logged in the field by our Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 4 representative and described in accordance with the Unified Soil Classification System (refer to Appendix A). The approximate locations of the hand pits are shown on Figure No. II, Plot Plan with Site-Specific Geologic Map. Representative soil samples were obtained from the exploratory hand pits at selected depths appropriate to the investigation. Soil sampling included in-place samples and bulk samples collected from the exploratory hand pits to aid in classification and for appropriate laboratory testing. All samples were returned to our laboratory for evaluation and testing. Exploratory hand pit logs have been prepared based on our observations and laboratory test results and are attached as Figure Nos. IIIa-f. The logs and related information reveal subsurface conditions only at the specific locations shown on the plot plan and on the particular date designated on the logs. Subsurface conditions at other locations may differ from conditions occurring at the explored locations. Also, the passage of time may result in changes in the subsurface conditions due to environmental changes. V. LABORATORY TESTING & SOIL INFORMATION Laboratory tests were performed on the soil samples in order to evaluate their physical and mechanical properties and their ability to support the proposed new residential building structures and associated improvements. The test results are presented at their respective depths on Figure Nos. IIIa-f and IVa-d. The following tests were conducted on representative soil samples: Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 5 1. Moisture Content (ASTM D2216-19) 2. Density Measurements (ASTM D2937-17e2) 3. Standard Test Method for Bulk Specific Gravity and Density of Com- pacted Bituminous Mixtures using Coated Samples (ASTM D1188-07) 4. Laboratory Compaction Characteristics (ASTM D1557-12e1) 5. Determination of Percentage of Particles Smaller than #200 Sieve (ASTM D1140-17) 6. Expansion Index (ASTM D4829-19) 7. Resistivity and pH Analysis (CA Test 643) 8. Water Soluble Sulfate (CA Test 417) 9. Water Soluble Chloride (CA Test 422) 10. Standard Test Method for Direct Shear Test of Soils Under Consolidated Drained Conditions (ASTM D-3080) Moisture content and density measurements were performed by ASTM methods D2216-19 and D2937-17e2 respectively, in conjunction with D1188-07 to establish the in-situ moisture and density of samples retrieved from the exploratory excavations. Density measurements were also performed by ASTM method D1188- 07, the bulk specific gravity utilizing paraffin-coated specimens. This method helps to establish the in-situ density of chunk samples retrieved from the excavations. Laboratory compaction values (ASTM D1557-12e1) establish the optimum moisture content and the laboratory maximum dry density of the tested soils. The relationship between the moisture and density of remolded soil samples helps to establish the relative compaction of the existing fill soils and soil compaction conditions to be anticipated during any future grading operation. The particle size smaller than a No. 200 sieve analysis (ASTM D1140-17) aids in classifying the tested soils in accordance with the Unified Soil Classification System and provides qualitative information related to engineering characteristics such as expansion potential, permeability, and shear strength. Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 6 The expansion potential of soils is determined, when necessary, utilizing the Standard Test Method for Expansion Index of Soils (ASTM D4829-19). In accordance with the Standard (Table 5.3), potentially expansive soils are classified as follows: EXPANSION INDEX POTENTIAL EXPANSION 0 to 20 Very low 21 to 50 Low 51 to 90 Medium 91 to 130 High Above 130 Very high Based on the test results, the sampled on-site soils were determined to have very low expansion potential, with a maximum measured expansion index of 0. Special recommendations are not required for the foundations or slabs on-grade due to soil expansivity. Any imported soils will need to an expansion index less than 20. To assess soil corrosivity of the on-site soils, resistivity, pH, chloride and soluble sulfate tests were performed by an outside consultant (Clarkson Laboratory and Supply, Inc.) on samples of the near surface soils most likely to be in contact with concrete and ferrous metals. The most common factor in determining soils corrosivity to ferrous metals is electrical resistivity. As soils’ resistivity decreases, its corrosivity to ferrous metals increases. The tested soils yielded resistivities of 7,700 to 15,000 Ohm-cm, indicating based on the generally adopted corrosion severity ratings, that the soils are moderately to mildly corrosive to ferrous metals. Soils and fluids are considered neutral when pH is measured at 7, acidic when pH is measured at <7 and alkaline when measured at >7. Soils are considered corrosive when the pH gets down to around 5.5 or less. Results of the laboratory testing yielded a pH value of 7.4, indicating that the tested soils slightly alkaline and not a significant factor in soil corrosivity to metals. Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 7 Large concentrations of chlorides will adversely affect any ferrous metals such as iron and steel. Soil with a chloride concentration greater than or equal to 500 ppm (0.05 percent) or more is considered corrosive to ferrous metals. The chloride content of the tested soils measured at approximately 20 ppm or 0.002 percent indicating that, at this site, chloride is not a major factor in corrosion to ferrous metals. The primary cause of deterioration of concrete in foundations and other below ground structures is the corrosive attack by soluble sulfates present in the soil and groundwater. The results of water-soluble sulfate testing performed on a representative sample of the near surface soils in the general area of the proposed structures, yielded a soluble sulfate content of less than 80 ppm or 0.008 percent, indicating that the proposed cement-concrete structures that are in contact with the underlying soils are anticipated to be affected with a negligible sulfate exposure. Two additional laboratory direct shear tests per ASTM D3080 were performed for the building pad on-site soils, on samples taken on February 28, 2025, in order to determine and confirm the soil strength parameters such as the effective internal angle of friction and cohesion. The soil samples were remolded to 90% of the maximum dry density and were performed under saturated and unsaturated conditions. The laboratory testing results are presented in Figure Nos. IVa-d. It should be noted that Geotechnical Exploration Inc., does not practice corrosion engineering and our test results here should be construed as an aid to the owner or owner’s representative. Test results should be evaluated by an engineer specializing in soil corrosivity for any specific design requirement. Based on the field and laboratory test data, our observations of the primary soil types, and our direct shear test results, our Geotechnical Engineer has assigned values for i i Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 8 friction angle, coefficient of friction, and cohesion for those soils that will have significant lateral support or load bearing functions on the project. The following assigned soil strength values have been utilized in determining the recommended bearing value as well as active and passive earth pressure design criteria for foundations and retaining walls. 90% Remolded Condition Unit Weight (pcf) Cohesion (psf) Soil Friction Angle (°) Unsaturated 129 202 34 Saturated 120 173 30 VI. REGIONAL GEOLOGIC DESCRIPTION San Diego County has been divided into three major geomorphic provinces: The Coastal Plain, the Peninsular Ranges and the Salton Trough. The Coastal Plain exists west of the Peninsular Ranges. The Salton Trough is east of the Peninsular Ranges. These divisions are the result of the basic geologic distinctions between the areas. Mesozoic metavolcanic, metasedimentary and plutonic rocks predominate in the Peninsular Ranges with primarily Cenozoic sedimentary rocks to the west and east of this central mountain range (Demere, 1997). For more detailed geologic descriptions, refer to Appendix B. VII. SITE-SPECIFIC SOIL & GEOLOGIC DESCRIPTION Review of the Geologic Map of Oceanside, 30'x60' Quadrangle, CA by Kennedy and Tan, 2007, indicates that the subject site is located in an area underlain by Old Paralic Deposits (Qop6-7). An excerpt of this geologic map and legend is included as Figure No. V. Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 9 A. Stratigraphy Our field investigation, reconnaissance, and review of the “Geologic Map of the Oceanside 30’x60’ Quadrangle, California” by Kennedy and Tan, 2007, indicate that the site is underlain at depth by late to middle Pleistocene-Aged Old Paralic Deposits, Units 6-7 (Qop6-7) formational materials. The geologic map indicates that the Paralic Deposits are underlain at depth by the Tertiary-age Santiago Formation (Tsa). An excerpt of the geologic map is included as Figure No. V. Our exploratory handpits indicate the formational materials are overlain across the site by a thin veneer of artificial fill soils (Qaf). Site-specific geology is shown on Figure No. II, the Plot Plan and Site-Specific Geologic Map. Fill Soil (Qaf): Our site investigation indicates that the areas in the general vicinity of our exploratory handpits at the site are overlain by 1 to 2.5 feet of fill soil. The encountered fill soil consists of slightly moist, brown to dark brown, fine- to medium- grained silty sand (SM). The fill soils are generally loose to medium dense. We also uncovered areas (HP-4, HP-5 and HP-6) where buried debris and trash consisting of plastic, glass, brick and roots where encountered. In our opinion, due to the variable density of the fill soil and the encountered buried trash it is not considered suitable in its current condition to support loads from structures or additional fill. Refer to Figure Nos. IIIa-f for details. Old Paralic Deposits, Unit 6-7 (Qop6-7): The encountered formational materials are described in the literature as Quaternary (late to middle Pleistocene) Old Paralic Deposits, Units 6-7. These formational materials were encountered in all of our exploratory excavations underlying the fill soil at depths from 1 to 2.5 feet. The formational materials consist of fine- to medium-grained, slightly moist to moist, brown and reddish-brown silty sands (SM) with some iron oxide/manganese nodules. Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 10 The formational Old Paralic materials underlying the site were observed to be weathered medium dense and porous in the upper layers and become dense at depths ranging from approximately 2.5 to 3.5 feet in depth. In our opinion, the dense nature of the Old Paralic Deposits, Units 6-7, makes it suitable in its current condition to support loads from structures or additional fill. Refer to Figure Nos. IIIa-f for details. A review of the Kennedy and Tan, 2007, geologic map indicates that the Old Paralic Deposits, Units 6-7, formational materials underlie the entire site at depth. The aforementioned Old Paralic Deposit Units are described as “Poorly sorted, moderately permeable, reddish-brown, interfingered strandline, beach, estuarine and colluvial deposits composed of siltstone, sandstone and conglomerate.” According to the map, there are no faults known to pass through the site (refer to Figure No. V, Geologic Map Excerpt and Legend). B. Structure Visible geologic structure was not identified during our field investigation. The Old Paralic Deposits (Qop6-7) formation was noted to be massive in our exploratory excavations. As shown on the geologic map the Old Paralic Deposits are underlain at depth by the Tertiary Santiago Formation (Tsa). The essentially horizontal contact of Old Paralic Deposits over the Santiago Formation indicates no significant structural deformation has occurred in the area of the project. It is our opinion that the geologic structure of the site does not present a hazard to the site and is stable from a geotechnical perspective. Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 11 VIII. GEOLOGIC HAZARDS Our field work, as well as the references cited, indicate a favorable geologic structure at the site. Based on our reconnaissance and the data obtained in our field investigation, review of pertinent geological literature and analysis of geological maps and aerial photographs, it is our opinion that the area of study has favorable geologic structure and is low risk from a geologic hazard perspective. There are no known active landslide deposits underlying the site. Based on review of available geologic and fault hazards maps and reports, it is our opinion that neither an active nor potentially active fault underlies the site in the area of the proposed new residential building structures and improvements. The following is a discussion of the geologic conditions and hazards common to this area of Carlsbad, as well as project-specific geologic information relating to development of the subject site. A. Local and Regional Faults Reference to the Geologic Map and Legend, Figure No. V (Kennedy and Tan, 2007), indicates that no faults are shown to cross the site. As noted previously, in our professional opinion, neither an active fault nor a potentially active fault underlies the site in the area of the proposed construction. The site, like most of southern California, is located in a seismically active area and regional faulting is present in San Diego County. The major active faults nearest to the site are all part of the Newport-Inglewood-Rose Canyon Fault Zone. Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 12 Newport-Inglewood-Rose Canyon Fault Zone (Oceanside Section): The closest mapped fault in this zone is the Oceanside section of the Newport-Inglewood- Rose Canyon Fault Zone mapped at approximately 4.6 miles west-southwest from the site. The Rose Canyon Fault Zone is the southern portion (San Diego section) of the Newport-Inglewood-Rose Canyon Fault system. This fault zone is formed by several active faults in the San Diego area. The closest mapped faults in this zone are the northern portion of the Mount Soledad Fault, mapped approximately 21 miles south of the site; the Spanish Bight Fault mapped approximately 27 miles south-southeast of the site; the Coronado Bank Fault and the Downtown Grabben Fault, both mapped approximately 31 miles south- southeast of the site; the Silver Strand Fault, located approximately 34 miles south-southeast of the site; and the northern portion of the Rose Canyon Fault, mapped approximately 22 miles south-southeast of the site. Review of the available references indicates that the Rose Canyon Fault Zone system is considered to be capable of generating a M6.9 earthquake (EERI, 2021). Other local and regional faults considered active are: Coronado Bank-Palos Verdes Section of the Coronado-Bank Fault: Mapped approximately 22 miles west of the site. Review of the available references indicates that the Rose Canyon Fault Zone system is considered to be capable of generating a M6.9 earthquake (EERI, 2021). Elsinore Fault Zone: The Temecula and Julian sections of the Elsinore Fault Zone are mapped approximately 23 and 33 miles, respectively, northeast of the site and are estimated to be capable of a of a M6.5 to M7.5 earthquake (SCEDC, 2022). Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 13 San Diego Trough Fault Zone: Mapped approximately 30 miles southwest of the site. San Jacinto Fault: Mapped approximately 49 miles northeast of the site. This fault is estimated to be capable of a M6.5 to M7.5 (SCEDC, 2022). San Clemente Fault: Mapped approximately 59 miles southwest of the site. The most recent surface rupture is of Holocene age (SCEDC, 2022). The above fault distances are measured from the closest point to the subject site. The potential for strong ground shaking from earthquakes on active southern California faults and active faults in northwestern Mexico should be anticipated at the site. Design of building structures in accordance with the current building codes would reduce the potential for injury or loss of human life. Buildings constructed in accordance with current building codes may suffer significant damage but should not undergo total collapse. B. Other Geologic Hazards Ground Rupture: Ground rupture is characterized by bedrock slippage along an established fault and may result in displacement of the ground surface. For ground rupture to occur along a fault, an earthquake usually exceeds M5.0. If a M5.0 earthquake were to take place on a local fault, an estimated surface-rupture length 1 mile long could be expected (Greensfelder, 1974). Our investigation indicates that the subject site is not directly on a known active fault trace and, therefore, the risk of ground rupture is remote. Ground Shaking: Structural damage caused by seismically induced ground shaking is a detrimental effect directly related to faulting and earthquake activity. Ground shaking is considered to be the greatest seismic hazard in San Diego County. The intensity of ground shaking is dependent on the magnitude of the earthquake, the Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 14 distance from the earthquake, and the seismic response characteristics of underlying soils and geologic units. Earthquakes of M5.0 or greater are generally associated with significant damage. It is our opinion that the most serious damage to the site would be caused by a large earthquake originating on a nearby strand of the Rose Canyon, Coronado Bank or Newport-Inglewood Faults. Although the chance of such an event is remote, it could occur within the useful life of the structure. Landslides: Our investigation indicates that the subject site is not located on a known recent or ancient landslide. Review of the “Geologic Map of the Oceanside 30’x60’ Quadrangle, California” by Kennedy and Tan (2007) and the USGS Landslide Hazard Program Site (US Landslide Inventory), indicate that there are no known or suspected ancient landslides located on the site. Slope Stability: Our site observations and topographic mapping indicates that the site slopes gently in a westerly direction, with only a 3-foot difference in elevation across the site. The site is underlain by stable and dense Old Paralic Deposits, Unit 6-7 formational materials at a depth of approximately 1 to 2.5 feet. In our opinion, there is not a slope stability issue with the site. Liquefaction: The liquefaction of saturated sands during earthquakes can be a major cause of damage to buildings. Liquefaction is the process by which soils are transformed into a viscous fluid that will flow as a liquid when unconfined. It occurs primarily in loose, cohesionless saturated silt, sand, and fine-grained gravel deposits of Holocene to late Pleistocene age and in areas where the groundwater is shallower than about 50 feet (DMG Special Publication 117) when they are sufficiently shaken by an earthquake. On this site, the risk of liquefaction of formational materials due to seismic shaking is considered to be very low due to the dense to very dense nature of the underlying formational materials and the lack of shallow static groundwater. Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 15 The site does not have a potential for soil strength loss to occur due to a seismic event. Tsunamis and Seiches: A tsunami is a series of long waves generated in the ocean by a sudden displacement of a large volume of water. Underwater earthquakes, landslides, volcanic eruptions, meteor impacts, or onshore slope failures can cause this displacement. Tsunami waves can travel at speeds averaging 450 to 600 miles per hour. As a tsunami nears the coastline, its speed diminishes, its wave length decreases, and its height increases greatly. After a major earthquake or other tsunami-inducing activity occurs, a tsunami could reach the shore within a few minutes. One coastal community may experience no damaging waves while another may experience very destructive waves. Some low-lying areas could experience severe inland inundation of water and deposition of debris more than 3,000 feet inland. The site is located approximately 0.3-mile from the exposed coastline and at an elevation of approximately 43 to 46 feet above MSL. Review of the Tsunami Hazard Area Map County of San Diego (October 7, 2022), indicates the site is located outside the tsunami inundation hazard area. There is no risk of tsunami inundation at the site. A seiche is a run-up of water within a lake or embayment triggered by fault- or landslide-induced ground displacement. The site is located near a coastal lagoon that is not considered capable of producing a seiche and inundating the subject site. Flood Hazard: Review of the FEMA flood maps number 06073C0761H, effective on 12/19/2019, indicates the project site is located within the Special Flood Hazard Area (SFHA) X. Zone X is described as minimal flood hazard. The civil engineer should verify this statement with the City of Carlsbad and County of San Diego (FEMA, 2019). Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 16 Geologic Hazards Summary: No significant geologic hazards are known to exist on the site that would prohibit the construction of the proposed Residential building structures and associated improvements. Ground shaking from earthquakes on active southern California faults and active faults in northwestern Mexico is the greatest geologic hazard at the property. Design of the proposed structures and associated improvements in accordance with the current building codes would reduce the potential for injury or loss of human life. Structures constructed in accordance with current building codes may suffer significant damage but should not undergo total collapse. It is our opinion, based upon a review of the available maps, our research, and our site investigation, that the proposed structures and associated improvements would not destabilize neighboring properties or induce the settlement of adjacent structures or right-of-way improvements if designed and constructed in accordance with our recommendations. In our professional opinion, no active or potentially active fault or landslide underlies the site in the area of the proposed construction. IX. GROUNDWATER Groundwater was not encountered in any of our exploratory excavations. We do not anticipate significant groundwater problems to develop in the future, if the property is developed as proposed and proper drainage is implemented and maintained. It should be kept in mind that any required construction operations will change surface drainage patterns and/or reduce permeabilities due to the densification of compacted soils. Such changes of surface and subsurface hydrologic conditions, plus irrigation of landscaping or significant increases in rainfall, may result in the appearance of surface or near-surface water at locations where none existed previously. The damage from such water is expected to be localized and cosmetic in Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 17 nature, if good positive drainage is implemented, as recommended in this report, during and at the completion of construction. On properties such as the subject site where dense, low permeability soils exist at shallow depths, even normal landscape irrigation practices on the property or neighboring properties, or periods of extended rainfall, can result in shallow “perched” water conditions. The perching (shallow depth) accumulation of water on a low permeability surface can result in areas of persistent wetting and drowning of lawns, plants and trees. Resolution of such conditions, should they occur, may require site-specific design and construction of subdrain and shallow “wick” drain dewatering systems. Subsurface drainage with a properly designed and constructed subdrain system will be required along with continuous back drainage behind any proposed lower-level basement walls, property line retaining walls, or any perimeter stem walls for raised- wood floors where the outside grades are higher than the crawl space grades. Furthermore, crawl spaces, if used, should be provided with the proper cross- ventilation to help reduce the potential for moisture-related problems. Additional recommendations may be required at the time of construction. It must be understood that unless discovered during site exploration or encountered during site construction operations, it is extremely difficult to predict if or where perched or true groundwater conditions may appear in the future. When site fill or formational soils are fine-grained and of low permeability, water problems may not become apparent for extended periods of time. Water conditions, where suspected or encountered during construction, should be evaluated and remedied by the project civil and geotechnical consultants. The project developer and property owner, however, must realize that post-construction i i Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 18 appearances of groundwater may have to be dealt with on a site-specific basis. Proper functional surface drainage should be implemented and maintained at the property. X. CONCLUSIONS & RECOMMENDATIONS The following recommendations are based upon the practical field investigations conducted by our firm, and resulting laboratory tests, in conjunction with our knowledge and experience with similar soils in the Carlsbad area. The opinions, conclusions, and recommendations presented in this report are contingent upon Geotechnical Exploration, Inc. being retained to review the final plans and specifications as they are developed and to observe the site earthwork and installation of foundations. Accordingly, we recommend that the following paragraph be included on the grading and foundation plans for the project. If the geotechnical consultant of record is changed for the project, the work shall be stopped until the replacement has agreed in writing to accept responsibility within their area of technical competence for approval upon completion of the work. It shall be the responsibility of the permittee to notify the governing agency in writing of such change prior to the recommencement of grading and/or foundation installation work and comply with the governing agency’s requirements for a change to the Geotechnical Consultant of Record for the project. Existing fill soils extend to relatively shallow depths of 1 to 2.5 feet across much of the lot as encountered at the explored locations. The fill soils and upper 1 to 2 feet of paralic deposits are, in general, loose to medium dense, slightly moist to moist, porous with a generally very low expansion potential. The fill soils and upper paralic deposits are not suitable in their current condition to support the proposed new residential building structures and associated improvements. Removal and Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 19 recompaction of all existing fill soils and upper paralic deposits down to adequate bearing formational materials at an approximate depth of 2 to 3 feet will be required. It is our opinion, based on our current understanding of the proposed construction, that the area of study is suitable for the planned new three-story structures and associated improvements, provided the recommendations herein are incorporated during design and construction. A. Preparation of Soils for Site Development 1. General: Grading should conform to the guidelines presented in the 2022 California Building Code (CBC), as well as the requirements of the City of Carlsbad. During earthwork construction, removals and reprocessing of loose and unsuitable porous materials, as well as general grading procedures of the contractor, should be observed and tested by representatives of the geotechnical engineer, Geotechnical Exploration Inc. If any unusual or unexpected conditions are exposed in the field, they should be reviewed by the geotechnical engineer and if warranted, modified and/or additional remedial recommendations will be offered. Specific guidelines and comments pertinent to the planned development are provided herein. The recommendations presented herein have been prepared using the information provided to us regarding site development. If information concerning the proposed development is revised or if any changes in the design and location of the proposed structures are made, they should be approved in writing by this office. Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 20 2. Clearing and Stripping: Complete demolition of the existing structures and associated improvements should be undertaken. This is to include the complete removal of all subsurface footings, utility lines and miscellaneous debris. After clearing, the entire ground surface of the site should be stripped of existing vegetation within the areas of proposed new construction. Once the required excavations have been made down to suitable soils, holes resulting from the removal of root systems or other buried obstructions that extend below the planned grades should be cleared and backfilled with suitable compacted material compacted to the requirements provided under the Recommendations below. Prior to any filling operations, the cleared and stripped vegetation and debris should be disposed of off-site. 3. Excavation: After the pertinent areas of the site have been cleared and stripped, the existing fill soils or soft, loose and porous soils in the area of the new structures and exterior hardscape improvements should be removed and recompacted. It is anticipated that the depth of removal will be 2 to 3 feet below existing grade. Based on our exploratory excavations, unsuitable fill soils in all areas to receive structural improvements that are proposed to bear on compacted fill soils must be removed to expose suitable formational soils and replaced with compacted fill soils to reach final grades. Based on our experience with similar materials in the project area, it is our opinion that the existing fill soils and formational materials can be excavated utilizing ordinary light to heavy weight earthmoving equipment. Contractors should not, however, be relieved of making their own independent evaluation of excavating the on-site materials prior to submitting their bids. Contractors should also review this report along with the excavation logs to understand the Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 21 scope and quantity of grading required for this project. Variability in excavating the subsurface materials should be expected across the project area. Undercutting may be recommended at time of grading if shallow portions of fill removal are encountered in an area and deeper fills in another area under the proposed structures or improvements. The areal extent required to remove the surficial soils and existing fill should be confirmed by our representatives during the excavation work based on their examination of the soils being exposed. The lateral extent of the excavation and recompaction should be at least 5 feet beyond the edge of the perimeter ground level foundation of the new structures bearing on fill soils and any areas to receive exterior improvements where feasible, or to the depth of excavation or fill at that location, whichever is greater. 4. Subgrade Preparation: After the project site area has been cleared, stripped, and the required excavations made, the exposed approved subgrade soils in areas to receive new fill and/or slab on-grade improvements should be scarified to a depth of 6 inches, moisture conditioned, and compacted to the requirements for structural fill. While not anticipated, in the event that planned cuts expose any medium to highly expansive soil materials, they should be scarified and moisture conditioned to at least 5 percent above optimum moisture. 5. Material for Fill: Existing on-site soils have very low expansion potential (Expansion Index between 0 and less than 20 per ASTM D4829-19) granular soils with an organic content of less than 3 percent by volume are, in general, suitable for use as fill. Fill soils containing significant debris, as exposed in HP- 4, HP-5 and HP-6, must be exported off-site. Imported fill material, where required, should have very low expansion potential (E.I. between 0 and less Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 22 than 20). During the building pad preparation, and if encountered, all rock over 6 inches in diameter should be removed from the excavated soils. In addition, any imported and/or existing on-site materials for use as fill should not contain rocks or lumps more than 6 inches in greatest dimension if the fill soils are compacted with heavy compaction equipment (or 3 inches in greatest dimension if compacted with lightweight equipment). All materials for use as fill should be approved by our representative prior to importing to the site. The on-site soils have a very low expansive potential and can be used as structural fill and as retaining wall backfill (if proposed). Backfill material to be placed behind retaining walls should be very low expansive soils (E.I. less than 20), with rocks no larger than 3 inches in diameter. 6. Structural Fill Compaction: All structural fill, and areas to receive any associated improvements, should be compacted to a minimum degree of compaction of 90 percent based upon ASTM D1557-12e1. Fill material should be spread and compacted in uniform horizontal lifts not exceeding 8 inches in uncompacted thickness. When using lightweight compaction equipment, the thickness of loose soils layers to be compacted should be no more than 5 inches. Before compaction begins, the fill should be brought to a water content that will permit proper compaction by either: (1) aerating and drying the fill if it is too wet, or (2) watering the fill if it is too dry. Each lift should be thoroughly mixed before compaction to ensure a uniform distribution of moisture. Low expansive granular soils should be moisture conditioned to 3 percent above optimum moisture content. Soil compaction testing by nuclear method ASTM D6938-17a or sand cone method ASTM D1556-15e1 should be performed every 2 feet or less of fill placement by a representative of Geotechnical Exploration, Inc. Further- Mi Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 23 more, our representative should perform necessary observation of fill placement during grading operations throughout the project. Any rigid improvements founded on the existing undocumented fill soils can be expected to undergo movement and possible damage. Geotechnical Exploration, Inc. takes no responsibility for the performance of any improvements built on loose natural soils or inadequately compacted fills. Subgrade soils in any exterior area receiving concrete improvements should be verified for compaction and moisture by a representative of our firm within 48 hours prior to concrete placement. No uncontrolled fill soils should remain after completion of the site work. If temporary ramps or pads are constructed of uncontrolled fill soils, the loose fill soils should be removed and/or recompacted prior to completion of the grading operation. 8. Trench Backfill: All utility trenches should be backfilled with properly compacted imported fill or low expansive on-site soils, but capped (upper 8 inches) with properly compacted on-site soils. Imported backfill material should be placed in lift thicknesses appropriate to the type of compaction equipment utilized and compacted to a minimum degree of compaction of 90 percent by mechanical means. Any portion of the trench backfill in public street areas within pavement sections should conform to the material and compaction requirements of the adjacent pavement section. Our experience has shown that even shallow, narrow trenches (such as for irrigation and electrical lines) that are not properly compacted can result in problems, particularly with respect to shallow groundwater accumulation and migration. Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 24 9. Observations and Testing: As stated in CBC 2022, Section 1705.6 Soils: “Special inspections and tests of existing site soil conditions, fill placement and load-bearing requirements shall be performed in accordance with this section and Table 1705.6 (see below). The approved geotechnical report and the construction documents prepared by the registered design professionals shall be used to determine compliance. During fill placement, the special inspector shall verify that proper materials and procedures are used in accordance with the provisions of the approved geotechnical report.” A summary of Table 1705.6 “REQUIRED SPECIAL INSPECTIONS AND TESTS OF SOILS” is presented below: a) Verify materials below shallow foundations are adequate to achieve the design bearing capacity; b) Verify excavations are extended to proper depth and have reached proper material; c) Perform classification and testing of compacted fill materials; d) Verify use of proper materials, densities and thicknesses during placement and compaction of compacted fill prior to placement of compacted fill, inspect subgrade and verify that site has been prepared properly. Section 1705.6 “Soils” statement and Table 1705.6 indicate that it is mandatory that a representative of this firm (responsible geotechnical engineering firm), perform observations and fill compaction testing during excavation operations to verify that the remedial operations are consistent with the recommendations presented in this report. All grading excavations resulting from the removal of soils should be observed and evaluated by a representative of our firm before they are backfilled. Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 25 Quality control grading observation and field density testing for the purpose of documenting adequate compaction has been achieved and acceptable soils have been utilized to properly support a project applies not only to fill soils supporting primary structures, but all site improvements such as stairways, patios, pools and pool decking, sidewalks, driveways and retaining walls, building additions, ADUs, etc. Observation and testing of utility line trench backfill also reduces the potential for localized settlement of all of the above including all improvements outside of the footprint of primary structures. The Geotechnical Engineer of Record, in this case Geotechnical Exploration, Inc., cannot be held responsible for the costs and time delays associated with the lack of contact and requests for testing services by the client, general contractor, grading contractor or any of the project design team responsible for requesting the required geotechnical services. Request for services is to be made through our office telephone number (858) 549-7222 and the telephone number of the GEI personnel assigned to the project at least 24 hours in advance prior to the needed service visit. B. Seismic Design Criteria 10. Seismic Data Bases: The estimation of the peak ground acceleration and the repeatable high ground acceleration (RHGA) likely to occur at the site is based on the known significant local and regional faults within 100 miles of the site. 11. Seismic Design Criteria: The proposed structures should be designed in accordance with the 2022 CBC, which incorporates by reference the ASCE 7- 16 for seismic design. We have determined the mapped spectral acceleration values for the site based on a latitude of 33.1573 degrees and a longitude of - 117.3467 degrees, utilizing a program titled “Seismic Design Map Tool” and Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 26 provided by the USGS through SEAOC, which provides a solution for ASCE 7- 16 utilizing digitized files for the Spectral Acceleration maps. Refer to Appendix C for the ASCE Seismic Summary Report. 12. Structures and Foundation Design: The design of the new structures and foundations should be based on Seismic Design Category D, Risk Category II for a Site Class D, Stiff Soils, which considers the dense soils or foundations bearing in dense formational soils. 13. Spectral Acceleration and Design Values: The structural seismic design, when applicable, should be based on the following seismic soil parameter values, which are based on the site location, soil characteristics, and seismic maps by USGS, as required by the 2022 CBC. Seismic design soil parameters were obtained with the SEAOC Seismic Design Map Tool and they are presented in summarized form below. A full computer printout is presented as Appendix C. TABLE I Mapped Spectral Acceleration Values and Design Parameters SS S1 SMS SM1 SDS SD1 Fa Fv PGA PGAM SDC 1.082 0.391 1.155 0.746 0.77 0.498 1.067 1.909 0.478 0.536 D C. Foundation Recommendations 14. Footings: Based on our field exploration and the encountered variable density surficial fill soils at the explored locations of the site where the proposed structures and new foundations are planned, we recommend that the new footings consist of continuous spread or isolated foundations bearing on properly compacted fill soils or medium dense formational soils. Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 27 No footings should be underlain by existing loose or undocumented fill soils. All structure footings should be founded on formational soils or properly compacted fill prepared as recommended in the above recommendations. All footings for the three-story structures should be founded at least 24 inches into dense formational soils or properly compacted fill soils. Footings located adjacent to utility trenches should have their bearing surfaces situated below an imaginary 1.0:1.0 plane projected upward from the bottom edge of the adjacent utility trench. Otherwise, the utility trenches should be excavated farther from the footing locations. 15. Bearing Values: At the recommended depths previously discussed, footings on compacted fill or formational soils can be designed for allowable bearing pressures of 3,000 psf for combined dead and live loads and 3,990 psf, 33 percent increase, for all loads including wind or seismic. For three stories, the footings should, however, have a minimum width of 15 inches and depth of 24 inches into medium dense formation or properly compacted fill. An increase in soil allowable static bearing can be used as follows: 1,000 psf for each additional foot over 2 feet in depth and 600 psf for each additional foot in width, to a total static bearing capacity not exceeding 5,500 psf. As previously indicated, all of the foundations for the proposed structures should be built on properly compacted fill or dense formational soils. For retaining walls (if proposed), foundations may be 1.5 feet deep and be designed for an allowable soil bearing of 2,000 psf, with an allowable increase of 1000 psf for each additional foot in embedment and 600 psf for each additional foot in width over the minimum 1 foot. The total allowable soil bearing capacity should not exceed 5,500 psf. Mi Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 28 16. Shallow Footing Reinforcement: All footings should be reinforced as specified by the structural engineer. However, based on our field investigation findings and laboratory testing, we provide the following minimum recommendations. All continuous footings should contain top and bottom reinforcement to provide structural continuity and to permit spanning of local irregularities. We recommend that, as a minimum, four No. 5 reinforcing bars be provided in the continuous footings (two at the top and two at the bottom). A minimum clearance of 3 inches should be maintained between steel reinforcement and the bottom or sides of the footing. Isolated square footings should contain, as a minimum, a grid of three No. 4 steel bars on 12-inch centers, both ways. In order for us to offer an opinion as to whether the footings are founded on soils of sufficient load bearing capacity, it is essential that our representative inspect the footing excavations prior to the placement of reinforcing steel or forms. NOTE: The project Civil/Structural Engineer should review all reinforcing schedules. The reinforcing minimums recommended herein are not to be construed as structural designs, but merely as minimum reinforcement to reduce the potential for cracking and separations. 17. Lateral Loads: Lateral load resistance for the structures supported on footing foundations may be developed in friction between the foundation bottoms and the supporting subgrade. An allowable friction coefficient of 0.40 is considered applicable. An additional allowable passive resistance equal to an equivalent fluid weight of 270 pounds per cubic foot (pcf) acting against the foundations may be used in design provided the footings are poured neat against dense soils or properly compacted fill materials. Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 29 These lateral resistance values assume a level surface in front of the footing for a minimum distance of three times the embedment depth of the footing and any shear keys, but not less than 8 feet from a slope face, measured from effective top of foundation from retaining walls (if proposed) and from the bottom of foundation for regular building foundations. Retaining walls supporting surcharge loads or affected by upper foundations should consider the effect of those upper loads. 18. Settlement: Settlement under structural design loads is expected to be within tolerable limits for the proposed structure. For footings designed in accordance with the recommendations presented in the preceding paragraphs, we anticipate that total settlement should be within allowable tolerance not exceed 1 inch and angular rotation should be less than 1/240. D. Concrete Slab On-Grade Criteria Slabs on-grade may only be used on new, properly compacted fill or when bearing on medium dense to dense formational soils. 19. Minimum Floor Slab Thickness and Reinforcement: Based on our experience, we have found that, for various reasons, floor slabs occasionally crack. Therefore, we recommend that all interior slabs on-grade contain sufficient reinforcing steel to reduce the separation of cracks, should they occur. Slab subgrade soil should be verified by a Geotechnical Exploration, Inc. representative to have the proper moisture content within 48 hours prior to placement of the vapor barrier and pouring of concrete. Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 30 Actual floor slab thickness and reinforcement recommendations should be provided by the project Structural Engineer. However, based on our investigation and laboratory data, new interior floor slabs should be at least 5 inches thick and be reinforced with a minimum of No. 4 steel bars spaced no farther than 18 inches apart in both directions. Soil moisture content should be kept above the optimum prior to waterproofing placement under the new concrete slab. Interior slabs should be underlain by a vapor barrier (15-mil StegoWrap) that may be placed directly on formational soils or properly compacted subgrade surface. We note that shrinkage cracking can result in reflective cracking in brittle flooring surfaces such as stone and tiles. It is imperative that if movement intolerant flooring materials are to be utilized, the flooring contractor and/or architect should provide specifications for the use of high-quality isolation membrane products installed between slab and floor materials. 20. Garage Slab Thickness and Reinforcement: The garage slab should be at least 5.5 inches thick and be reinforced with a minimum of No. 4 steel bars spaced no farther than 18 inches apart in both directions at the center of the slab, and contain adequate isolation and control joints. Control joints should be spaced no farther than 20 feet apart and at reentrant corners. Concrete should have a minimum compressive strength of 3,500 psi. 21. Slab Moisture Emission: Although it is not the responsibility of geotechnical engineering firms to provide moisture protection recommendations, as a service to our clients, we are providing a discussion regarding minimum protection for slabs as Appendix D. Actual recommendations should be provided by the project architect and waterproofing consultants or product manufacturer. It is recommended to contact the vapor barrier manufacturer Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 31 to schedule a pre-construction meeting and to coordinate a review, in-person or digital, of the vapor barrier installation. 22. Exterior Slab Thickness and Reinforcement: Exterior slab reinforcement and control joints should be designed by the project Structural Engineer. As a minimum for protection of on-site improvements, we recommend that all exterior concrete slabs be at least 4 inches thick, reinforced with No. 3 bars at 15-inch centers, both ways at the center of the slab, and contain adequate isolation and control joints. Control joints should be spaced no farther than 15 feet apart and at reentrant corners. The performance of on-site improvements can be greatly affected by soil base preparation and the quality of construction. It is therefore important that all improvements are properly designed and constructed for the existing soil conditions. The improvements should not be built on loose soils or fills placed without our observation and testing. The subgrade of exterior improvements should be verified as properly prepared within 48 hours prior to concrete placement. E. Retaining Wall Design Criteria It is our understanding that no retaining walls are currently planned for the site. However, if needed, retaining wall recommendations for walls higher than 3 feet that retain more than 3 feet of soil are presented below. 23. Design Parameters – Unrestrained: The active earth pressure to be utilized in the design of any cantilever site retaining walls, utilizing on-site or imported soils with very low expansion potential [EI less than 20] as backfill should be based on an Equivalent Fluid Weight of 38 pcf (for level backfill only). For Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 32 2.0:1.0 sloping very low expansive backfill, the cantilever site retaining walls should be designed with an equivalent fluid pressure of 52 pcf. Unrestrained retaining walls should be backfilled with properly compacted very low to low expansive soils. Unrestrained retaining walls should be designed when vertical load surcharged for a conversion load factor of 0.31 to convert vertical uniform surcharge loads to uniform horizontal lateral surcharge loads. 24. Design Parameters – Restrained: Permanent restrained shoring walls or restrained building retaining walls supporting on-site or imported soils with very low expansion potential, level compacted backfill may utilize a triangular pressure increasing at a rate of 56 pcf for wall design (78 pcf for sloping 2.0:1.0 backfill). The soil pressure produced by any footings, improvements, or any other surcharge placed within a horizontal distance equal to the height of the retaining portion of the wall should be included in the wall design pressure. A conversion factor of 0.47 pcf may be used to convert vertical uniform surcharge loads to lateral uniform pressure behind a restrained retaining wall with level backfill and 0.65 when supporting a 2.0:1.0 sloping backfill. The recommended lateral soil pressures are based on the assumption that no loose soils or unstable soil wedges will be retained by the retaining wall. Backfill soils should consist of very low-expansive on-site or imported soils (EI less than 20) and be placed from the heel of the foundation to the ground surface within the wedge formed by a plane at 30 from vertical, and passing by the heel of the foundation and the back face of the retaining wall. 25. Retaining Wall Seismic Design Pressures: For seismic design of unrestrained walls over 6 feet in exposed height, we recommend that the seismic pressure increment be taken as a fluid pressure distribution utilizing an equivalent fluid weight of 14 pcf. This seismic increment is waived for restrained retaining Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 33 walls. If the walls are designed as unrestrained walls, the seismic load should be added to the static soil pressure. 26. Retaining Wall Drainage: The preceding design pressures assume that the walls are backfilled with properly compacted very low expansion potential materials (Expansion Index less than 20) and that there is sufficient drainage behind the walls to prevent the build-up of hydrostatic pressures from surface water infiltration. We recommend that drainage be provided by a composite drainage material such as J-Drain 200/220 and J-Drain SWD, or equivalent. No perforated pipes or gravel are required with the J-Drain system. The drain material should terminate 12 inches below the exterior finish surface where the surface is covered by slabs or 18 inches below the finish surface in landscape areas. Waterproofing should extend from the bottom to the top of the wall. Refer to Figure No. VI, Retaining Wall Drainage Schematic. Backfill placed behind retaining walls should be compacted to a minimum degree of compaction of 90 percent using light compaction equipment. If heavy equipment is used, the walls should be appropriately temporarily braced. Crushed rock gravel may only be used as backfill in areas where access is too narrow to place compacted soils. Behind shoring walls, sand slurry backfill may be used behind lagging. Geotechnical Exploration, Inc. will assume no liability for damage to structures or improvements that is attributable to poor drainage. The architectural plans should clearly indicate that subdrains for any lower-level walls be placed at an elevation at least 1 foot below the bottom of the lower- level slabs. Mi Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 34 It is not within the scope of our services to provide quality control oversight for surface or subsurface drainage construction or retaining wall sealing and base of wall drain construction. It is the responsibility of the contractor to verify proper wall sealing, geofabric installation, protection board installation (if needed), drain depth below interior floor or yard surfaces, pipe percent slope to the outlet, etc. F. Temporary Slopes Due to the limited 2- to 3-foot depth of removal and recompaction during grading, no significant slopes or temporary slopes should be produced during site preparation. Perimeter property line cuts 2.5 to 3 feet high made during grading will be observed by geotechnical staff and site-specific recommendations given if warranted at that time. G. Pavements 27. Concrete Pavement: We recommend that new driveways subject only to automobile and light truck traffic be at least 6 inches thick and be supported directly on properly prepared/compacted on-site subgrade soils. The upper 6 inches of the subgrade below the slab should be compacted to a minimum degree of compaction of 95 percent within 48 hours prior to paving. The concrete should conform to Section 201 of The Standard Specifications for Public Works Construction, 2021 Edition, for Class 560-C-3250. Garage slab pavement recommendations were provided in a previous section. In order to control shrinkage cracking, we recommend that saw-cut, weakened-plane joints be provided at about 12-foot centers both ways and at re-entrant corners. The pavement slabs should be saw-cut as soon as practical Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 35 but no more than 24 hours after the placement of the concrete. The depth of the shrinkage control joint should be one-quarter of the slab thickness and its width should not exceed 0.02-foot. Reinforcing steel is not necessary unless it is desired to increase the joint spacing recommended above. Control joints should be sealed with concrete pavement sealant. H. Site Drainage Considerations 28. Erosion Control: Appropriate erosion control measures should be taken at all times during and after construction to prevent surface runoff waters from entering footing excavations or ponding on finished building pad areas. 29. Surface Drainage: Adequate measures should be taken to properly finish- grade the property after the structures and other improvements are in place. Drainage waters from this site and adjacent properties should be directed away from the footings, floor slabs, and slopes, onto the natural drainage direction for this area or into properly designed and approved drainage facilities by the City of Carlsbad to be indicated by the project Civil Engineer. Roof gutters and downspouts should be installed on the structures with the runoff directed away from the foundation via closed drainage lines. Proper subsurface and surface drainage will help minimize the potential for waters to seek the level of the bearing soils under the footings and floor slabs. Failure to observe this recommendation could result in undermining and possible differential settlement of the structures or other improvements on the site or cause other moisture-related problems. Currently, the CBC requires a minimum 2 percent surface gradient for proper drainage of building pads Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 36 unless waived by the building official. Concrete pavement may have a minimum gradient of 0.5-percent. 30. Planter Drainage: Planter areas, flower beds and planter boxes should be sloped to drain away from the footings and floor slabs at a gradient of at least 5 percent within 5 feet of the perimeter walls. Any planter areas adjacent to the residence or surrounded by concrete improvements should be provided with sufficient area drains to help with rapid runoff disposal. No water should be allowed to pond adjacent to the structures or other improvements or anywhere on the site. 31. Drainage Quality Control: It must be understood that it is not within the scope of our services to provide quality control oversight for surface or subsurface drainage construction or retaining wall sealing and base of wall drain construction. It is the responsibility of the contractor to verify and provide proper surface drainage at the site, wall sealing, geofabric installation, protection board (if needed), drain depth below interior floor or yard surface, pipe percent slope to the outlet, etc. I. General Recommendations 32. Project Start Up Notification: In order to reduce work delays during site development, this firm should be contacted 48 hours prior to any need for observation of footing excavations or field density testing of compacted fill soils. If possible, placement of formwork and steel reinforcement in footing excavations should not occur prior to observing the excavations; in the event that our observations reveal the need for deepening or re-designing foundation structures at any locations, any formwork or steel reinforcement in the affected footing excavation areas would have to be removed prior to correction of the Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 37 observed problem (i.e., deepening the footing excavation, recompacting soil in the bottom of the excavation, etc.). 33. Cal-OSHA: Where not superseded by specific recommendations presented in this report, trenches, excavations, and temporary slopes at the subject site should be constructed in accordance with Title 8, Construction Safety Orders, issued by Cal-OSHA. 34. Construction Best Management Practices (BMPs): Construction BMPs must be implemented in accordance with the requirements of the controlling jurisdiction. Sufficient BMPs must be installed to prevent silt, mud or other construction debris from being tracked into the adjacent street(s) or storm water conveyance systems due to construction vehicles or any other construction activity. The contractor is responsible for cleaning any such debris that may be in the street at the end of each work day or after a storm event that causes breach in the installed construction BMPs. All stockpiles of uncompacted soil and/or building materials that are intended to be left unprotected for a period greater than 7 days are to be provided with erosion and sediment controls. Such soil must be protected each day when the probability of rain is 40% or greater. A concrete washout should be provided on all projects that propose the construction of any concrete improvements that are to be poured in place. All erosion/sediment control devices should be maintained in working order at all times. All slopes that are created or disturbed by construction activity must be protected against erosion and sediment transport at all times. The storage of all construction materials and equipment must be protected against any potential release of pollutants into the environment. Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 38 XI. GRADING NOTES Geotechnical Exploration, Inc. recommends that we be retained to verify the actual soil conditions revealed during site grading work and footing excavation to be as anticipated in this Final Geotechnical Investigation Report for the project. In addition, the placement and compaction of any fill or backfill soils during grading must be observed and tested by the soil engineer. It is the responsibility of the grading contractor and general contractor to comply with the requirements on the grading plans as well as the local grading ordinance. All retaining wall and trench backfill should be properly compacted. Geotechnical Exploration, Inc. will assume no liability for damage occurring due to improperly or uncompacted backfill placed without our observations and testing. XII. LIMITATIONS Our conclusions and recommendations have been based on available data obtained from our field investigation and laboratory analysis, as well as our experience with similar soils and formational materials located in this area of Carlsbad. Of necessity, we must assume a certain degree of continuity between exploratory excavations and/or natural exposures. It is, therefore, necessary that all observations, conclusions, and recommendations be verified at the time grading operations begin or when footing excavations are placed. In the event discrepancies are noted, additional recommendations may be issued, if required. The work performed and recommendations presented herein are the result of an investigation and analysis that meet the contemporary standard of care in our profession within the County of San Diego. No warranty is provided. Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 39 As stated previously, it is not within the scope of our services to provide quality control oversight for surface or subsurface drainage construction or retaining wall sealing and base of wall drain construction. It is the responsibility of the contractor to verify proper wall sealing, geofabric installation, protection board installation (if needed), drain depth below interior floor or yard surfaces, pipe percent slope to the outlet, etc. This report should be considered valid for a period of two (2) years, and is subject to review by our firm following that time. If significant modifications are made to the building plans, especially with respect to the height and location of any proposed structures, this report must be presented to us for immediate review and possible revision. It is the responsibility of the owner and/or developer to ensure that the recommendations summarized in this report are carried out in the field operations and that our recommendations for design of this project are incorporated in the project plans. We should be retained to review the project plans once they are available, to verify that our recommendations are adequately incorporated in the plans. Additional or modified recommendations may be issued if warranted. This firm does not practice or consult in the field of safety engineering. We do not direct the contractor's operations, and we cannot be responsible for the safety of personnel other than our own on the site; the safety of others is the responsibility of the contractor. The contractor should notify the owner if any of the recommended actions presented herein are considered to be unsafe. i i Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 40 The firm of Geotechnical Exploration, Inc. shall not be held responsible for changes to the physical condition of the property, such as addition of fill soils or changing drainage patterns, which occur subsequent to issuance of this report and the changes are made without our observations, testing, and approval. Once again, should any questions arise concerning this report, please feel free to contact the undersigned. Reference to our Job No. 23-14403 will expedite a reply to your inquiries. Respectfully submitted, GEOTECHNICAL EXPLORATION, INC. _______________________________ ______________________________ Leslie D. Reed, President Jaime A. Cerros, P.E. C.E.G. 999/P.G. 3391 R.C.E. 34422/G.E. 2007 Senior Geotechnical Engineer REFERENCES JOB NO. 23-14403 March 2025 2007 Working Group on California Earthquake Probabilities, 2008, The Uniform California Earthquake Rupture Forecast, Version 2 (UCERF 2), U.S Geological Survey Open-file Report 2007-1437 and California Geological Survey Special Report 203. Berger, V. and Schug, D.L., 1991, Probabilistic Evaluation of Seismic Hazard in the San Diego-Tijuana Metropolitan Region, Environmental Perils, San Diego Region, Geological Society of America by the San Diego Association of Geologists, October 20, 1991, p. 89-99. California Geological Survey, 2021a, Earthquake Zones of Required Investigation, La Jolla Quadrangle, Earthquake Fault Zones, Official Map. California Geological Survey, 2021b, Earthquake Zones of Required Investigation, Point Loma Quadrangle, Earthquake Fault Zones, Official Map. Crowell, J.C., 1962, Displacement Along the San Andreas, Fault, California, Geological Society of America, Special Papers, no. 71. Demere, T.A. 1997, Geology of San Diego County, California, San Diego Natural History Museum, http://archive.sdnhm.org/research/paleontology/sdgeol.html, accessed July 30, 2020. Department of Conservation, California Geological Survey, 2018, Earthquake Fault Zones A Guide for Government Agencies, Property Owners/Developers, and Geoscience Practitioners for Assessing Fault Rupture Hazards in California, Special Publication 42. DeFrisco, M., 2021, The Rose Canyon Fault Zone in The Point Loma and La Jolla 7.5 Minute Quadrangles San Diego County, California, California Geological Survey, Fault Evaluation Report 265. Earthquake Engineering Research Institute (EERI), 2021. GeoTracker, 2021, https://geotracker.waterboards.ca.gov/ Grant Ludwig, L.B. and Shearer, P.M., 2004, Activity of the Offshore Newport-Inglewood Rose Canyon Fault Zone, Coastal Southern California, from Relocated Microseismicity, Bulletin of the Seismological Society of America, 94(2), 747-752. Greene, H.G., Bailey, K.A., Clarke, S.H., Ziony, J.I. and Kennedy, M.P., 1979, Implications of fault patterns of the inner California continental borderland between San Pedro and San Diego, in Abbott, P.L., and Elliot, W.J., eds., Earthquakes and other perils, San Diego region: San Diego Association of Geologists, Geological Society of America field trip, p. 21–28. Greensfelder, R.W., 1974, Maximum Credible Rock Accelerations from Earthquakes in California, California Division of Mines and Geology. Hart, E.W. and Bryant, W.A., 1997, Fault-Rupture Hazard Zones in California, California Division of Mines and Geology, Special Publication 42. Hart, E.W., Smith, D.P. and Saul, R.B., 1979, Summary Report: Fault Evaluation Program, 1978 Area (Peninsular Ranges-Salton Trough Region), California Division of Mines and Geology, Open-file Report 79-10 SF, 10. ,m REFERENCES/Page 2 Hauksson, E. and Jones, L.M., 1988, The July 1986 Oceanside (ML=5.3) Earthquake Sequence in the Continental Borderland, Southern California Bulletin of the Seismological Society of America, v. 78, p. 1885-1906. Hileman, J.A., Allen, C.R. and Nordquist, J.M., 1973, Seismicity of the Southern California Region, January 1, 1932 to December 31, 1972; Seismological Laboratory, Cal-Tech, Pasadena, California. Kennedy, M. P., et.al., 1975, Character and Recency of Faulting San Diego Metropolitan Area, California, DMG Special Report 123. Kennedy, M. P. and Clarke, S.H., 1999, Analysis of Late Quaternary Faulting in San Diego Bay and Hazard to the Coronado Bridge, DMG Open File Report 97-10A. Kennedy, M.P. and Tan, S.S., 2007, Geologic Map of the Oceanside 30’x60’ Quadrangle, California. California Geological Survey, Regional Geologic Map No. 3 Scale: 1:100,000. Richter, C.F., 1958, Elementary Seismology, W.H. Freeman and Company, San Francisco, California. Rockwell, T.K., 2010, The Rose Canyon Fault Zone in San Diego, Proceedings of the Fifth International Conference on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics. Paper No. 7.06C. Rockwell, T.K., Dawson, T.E., Young Ben-Horin, J. and Seitz, G., 2014, A 21-Event, 4,000-Year History of Surface Ruptures in the Anza Seismic Gap, San Jacinto Fault, and Implications for Long-term Earthquake Production on a Major Plate Boundary Fault, Pure and Applied Geophysics, v. 172, 1143– 1165 (2015). Rockwell, T.K., Millman, D.E., McElwain, R.S. and Lamar, D.L., 1985, Study of Seismic Activity by Trenching Along the Glen Ivy North Fault, Elsinore Fault Zone, Southern California: Lamar-Merifield Technical Report 85-1, U.S.G.S. Contract 14-08-0001-21376, 19 p. Ross, Z.E., Hauksson E. and Ben-Zion Y., 2017, Abundant Off-fault Seismicity and Orthogonal Structures in the San Jacinto Fault Zone, Science Advances, 2017; 3(3): e1601946. Southern California Earthquake Data Center, 2022, Earthquake information, Fault Name Index, https://scedc.caltech.edu/earthquake/faults.html. Toppozada, T.R. and Parke, D.L., 1982, Areas Damaged by California Earthquakes, 1900-1949, California Division of Mines and Geology, Open-file Report 82-17. Mi VICINITY MAP Proposed Tyler Street Homes 3215-3225 Tyler Street Carlsbad, CA Figure No. I Job No. 23-14403 SITE Thomas Guide San Diego County Edition pg 1106-E6 PACIFIC OCEAN w ~ KNOWLES AV _ _j_ci ?ii Ul D• U ::,0 U.. o "VISA¼:,,., w LJ. 0 0 ~•J a: w ~~I-' s: a:o.. ~~ POINT 2 SCENl1 3 LOREl 4 SAND Geotechnical Exploration, Inc. Approximate Location of Proposed Structures HP-2 HP-3 HP-1 Approximate Location of Exploratory HandpitHP-6 HP-4 HP-6 Artificial FillQaf Qop Very Old Paralic Deposits Units 6-76-7 GEOLOGIC LEGEND 6666-7777777 6-7 6-7 6-777777 Proposed Tyler Street Homes 3215-3225 Tyler Street Carlsbad, CA. Figure No. II Job No. 23-14403 LEGEND PLOT PLAN AND SITE SPECIFIC GEOLOGIC MAP REFERENCE: This Plot Plan is not to be used for legal purposes. Locations and dimensions are approximate. Actual property dimensions and locations of utilities may be obtained from the Approved Building Plans or the “As-Built” Grading Plans. REFERENCE: This Plot Plan was prepared from an undated SITE PLAN by PASCO LARET SUITER & ASSOCIATES on-site field reconnaissance performed by GEI. January 2024 N GRAPHIC SCALE 1” = 20’ ( approximate ) 0 10 20 4030 TYLER STREET 23-14403-P-1-22-25 ( updated January 2025 ) ' s1-1 1 r C )N f: e ~ @© ~1 ~~ ~ ~0 : : , o : : , C ' > ' ) c : : i ~ <- . . i ~ < - . . i II .., , . . . . _ . . , , . : r : "' l"'G ' ~ i:: u . . l . J . J " = t ~: : ~ '- a , ~~ ~~ Ufi l t !I ! --ma >c ID "0 0 -.. Of D .. "' II :: r :: O : : s o- , :: s "' " II -- :: s "' I C, 1j> u , @© ~l~h ~ ;: ) : ~ ~ C, 1j > u , @© ~I ~ ! ~ .., , . . . , , . _ . . , , . UN I T 6 FF = 46 . 4 BM P # 1 PA D = 4 57 ::/ 'a l lt ; • ; •l, I A= 4 8 S F r, . . _ ~ ~- 4 8 _ 2 ' : J- ~L : .: = ] ,- ± : ;E P / - - r- CI I I I J 61 FS I I J f-- 457 F G I H P >1' i I . ~ "' I " ' " ' ~ J: : U . . L u . . , , . ~: : ~ "> - a , ~~ ;/ ~ ' ~ !H '& ~ 4'S T E P : 45 / F G / H P - C- -- - l7 BM P # 9 UN I T 12 A= 4 8 S F FF = 4 6 . 4 48 2 FG PA O = 45 . 7 ~~ - a in r ii (I ) ii ► g~ C, 1j > u , 7 G) G) Il l ~ ~ 1rr ~ ao : : , 0 > ( " ) ~ ~ &~ UN I T 5 l FF = 46 . 4 FF PA D = 4 5 7 P, '- a -- ~ T 4' S T E P 7 -- LJ i f E } 46 . 1 FS 46 . 1 FS ~H ,; t -- - - ~ -1, 48~ \: s - Q UN I T 1 UN I T 1 1 FF = _4, FF = 4 6 . 4 ,, - - B M P # 1 0 PA D - PA D = 4 5 . 7 A= 3 2 S F ~1'- ' > c , " - " - { O> ~ ~ ~ ~ &: ~~ ~ ~ 7 i ' M r,. . . C O ::t : """ ~~ 7J s;: z :: ; m ~ ' G) ~ g z G) 7J s;: z LO T 4 MA P NO 17 4 3 NW 20 4 - 0 1 0 - 0 8 - ( ) 0 C, 1j > u , @© ~l~h ~~ ~~ "'- l"'G ' ~ t ; : i:: u . . L u O > C V , <'> I @( § ) < ' . i M ~~ ~ . . , , . i ;i LO T 6 MA P NO 17 4 3 AP N · 20 4 - 0 7 0 - 2 8 - ( ) 0 C, 1j> u , @© ~ ~1 ~ ~ ~ ) ,., ,g !' 1 47 . 1 4~ j - \ 4' ST E P 46 . B F S ~H :c f- 0 i "" 0 0 PU B L I C RO W ~°" 4 () ~ ~ ) C, 1j> u , @© >- cr' I ~1~~ ~: : : ; "' t-- . ' 0 " " 1 , - . . < ' - i ~ ~~ ~ ~ ~ C, 1j> u , @© >- ~1~~ ~ : : : ; 'O < " ) C ' Y ) ' O < ' - i ~~ ~ ~ ~ H+ - .t - , ~ 11 11 1 : "Ar 5t 5t 46 5 F G ~ I 4' ST E P -- - - - - - - j ~4:: : B i ' s_ \ _ ~ , : I q ~- - -- ~ R O P B I K E R A C K 1 UN JT 8 CL - A7 A ~ ~ •= ! i +- , - - - - 1 - - - ~ ~ •F- , = 46 . 7 !E ~ ' ,, ~ ~1&: ~ ; ~: : ~ "> - a , ;~ " ST U B FO R FU T U I DE V E L O P M E N T W I W j IR R -= = f l R R 7 - F -- G / c I G) ~ I G) ~G G) -+ ii I G) c, I G) r I I .I , ,I I I PR O P TR A N S F O I G) G) G) d,- i:: Lu , . . _ _ _ a "' lf:e G~ t i : ~: : ~ ~ ~ -•- w - w SY M B O L SA M P L E BL O W S / 6" SM SM 1 H 5 SILTY SAND, loose to medium dense, slightly moist, light brown some gravel. MODIFIED CALIFORNIA SAMPLE FIGURE NO. IIIaIN-PLACE HAND-DRIVE SAMPLE STANDARD PENETRATION TEST PERCHED WATER TABLE BULK BAG SAMPLE IN-PLACE SAMPLE SITE LOCATION: 3215-3225 Tyler Street, Carlsbad, CA JOB NUMBER: 23-14403 JOB NAME: Tyler Street Homes LOG NO.HP 1FOOTING * DISTURBED BLOWCOUNT 21 19 18 20 17 13 15 16 14 11 10 12 9 1 2 3 @3.5 Ft. Becomes dense, moist. No Groundwater, No Caving, Backfilled with Cuttings 8 6 7 4 EX P A N S I O N I N D E X % P A S S I N G # 2 0 0 SI E V E OP T I M U M MO I S T U R E ( % ) MA X I M U M D R Y DE N S I T Y ( p c f ) DE N S I T Y ( % o f MD D ) EX P A N ( + % ) CO N S O L ( - % ) BA G S A M P L E Artificial Fill (Qaf) Terrace Deposits (Qop6-7) EQUIPMENT: Hand Tools DIMENSION & TYPE OF EXCAVATION: 2'x2'x3.5'DATE LOGGED: August 17, 2023 LOGGED BY: HE SURFACE ELEVATION: ± 42' Above Mean Sea Level SA M P L E O . D . ( i n ) DE P T H (f e e t ) DESCRIPTION AND REMARKS (Grain Size, Density, Moisture, Color) REVIEWED BY: LDR/JAC GROUNDWATER/SEEPAGE DEPTH: Not Encountered FIELD DESCRIPTION AND CLASSIFICATION U. S . C . S IN - P L A C E MO I S T U R E ( % ) IN - P L A C E D R Y DE N S I T Y ( p c f ) 23SILTY SAND, fine to medium grained, medium dense, slightly moist, red brown, porous. Bottom of Excavation at 3.5 ft. ◄~~-a ~ Geotechnical Exploration, Inc. - -\ I -X -~ - -\ I - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ---- ---= SY M B O L SA M P L E BL O W S / 6" SM SM H 6.4 116.8 1 H EQUIPMENT: Hand Tools DIMENSION & TYPE OF EXCAVATION: 2'x2'x3' DATE LOGGED: August 17, 2023 LOGGED BY: HE SURFACE ELEVATION: ± 42' Above Mean Sea Level % P A S S I N G # 2 0 0 SI E V E SA M P L E O . D . ( i n ) DE P T H (f e e t ) BA G S A M P L E DESCRIPTION AND REMARKS (Grain Size, Density, Moisture, Color) REVIEWED BY: LDR/JAC GROUNDWATER/SEEPAGE DEPTH: Not Encountered FIELD DESCRIPTION AND CLASSIFICATION U. S . C . S IN - P L A C E MO I S T U R E ( % ) IN - P L A C E D R Y DE N S I T Y ( p c f ) OP T I M U M MO I S T U R E ( % ) MA X I M U M D R Y DE N S I T Y ( p c f ) EX P A N S I O N I N D E X DE N S I T Y ( % o f MD D ) EX P A N ( + % ) CO N S O L ( - % ) SILTY SAND, loose to medium dense, slightly moist, light brown some gravel. 1 2 SILTY SAND, fine to medium grained, medium dense, slightly moist, red brown, porous.3 Artificial Fill (Qaf) 4 5 6 No Groundwater, No Caving, Backfilled with Cuttings Bottom of Excavation at 3 ft. @2.5 Ft. Becomes dense, moist. Terrace Deposits (Qop6-7) 9 7 8 12 10 11 15 13 14 17 16 19 18 21 FOOTING * DISTURBED BLOWCOUNT JOB NUMBER: 23-14403 20 FIGURE NO. IIIbIN-PLACE HAND-DRIVE SAMPLE STANDARD PENETRATION TEST LOG NO.HP 2JOB NAME: Tyler Street Homes SITE LOCATION: 3215-3225 Tyler Street, Carlsbad, CA PERCHED WATER TABLE BULK BAG SAMPLE IN-PLACE SAMPLE MODIFIED CALIFORNIA SAMPLE ◄~~-a ~ Geotechnical Exploration, Inc. - \ I - \ I - - - - - - - - - - - - - ---- _C __ ______._ _ _____.._________. SY M B O L SA M P L E BL O W S / 6" SM SM 1 3.6 104.0 1 H IN - P L A C E MO I S T U R E ( % ) IN - P L A C E D R Y DE N S I T Y ( p c f ) OP T I M U M MO I S T U R E ( % ) MA X I M U M D R Y DE N S I T Y ( p c f ) EX P A N S I O N I N D E X DE N S I T Y ( % o f MD D ) EX P A N ( + % ) CO N S O L ( - % ) SILTY SAND, loose to medium dense, slightly moist, light brown some gravel. 1 2 EQUIPMENT: Hand Tools DIMENSION & TYPE OF EXCAVATION: 2'x2'x3'DATE LOGGED: August 17, 2023 LOGGED BY: HE SURFACE ELEVATION: ± 44' Above Mean Sea Level % P A S S I N G # 2 0 0 SI E V E SA M P L E O . D . ( i n ) DE P T H (f e e t ) BA G S A M P L E DESCRIPTION AND REMARKS (Grain Size, Density, Moisture, Color) REVIEWED BY: LDR/JAC GROUNDWATER/SEEPAGE DEPTH: Not Encountered FIELD DESCRIPTION AND CLASSIFICATION U. S . C . S 6 3 @3.0 Ft. Becomes dense, moist. 4 5 Artificial Fill (Qaf) SILTY SAND, fine to medium grained, medium dense, slightly moist, red brown, porous. Bottom of Excavation at 3 ft. No Groundwater, No Caving, Backfilled with Cuttings Terrace Deposits (Qop6-7) 9 7 8 12 10 11 13 14 16 15 18 17 20 19 21 FOOTING * DISTURBED BLOWCOUNT JOB NUMBER: 23-14403 8.0 128.7 23-2 FIGURE NO. IIIcIN-PLACE HAND-DRIVE SAMPLE STANDARD PENETRATION TEST LOG NO.HP 3JOB NAME: Tyler Street Homes SITE LOCATION: 3215-3225 Tyler Street, Carlsbad, CA PERCHED WATER TABLE BULK BAG SAMPLE IN-PLACE SAMPLE MODIFIED CALIFORNIA SAMPLE ◄~~-a ~ Geotechnical Exploration, Inc. - --\ I -X -~ - -\ I - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ---- ---= SY M B O L FT G . D E P T H BL O W S / 6" SM SM 1 H EQUIPMENT: Hand Tools DIMENSION & TYPE OF EXCAVATION: 2'x2'x3.5'DATE LOGGED: August 17, 2023 LOGGED BY: HE SURFACE ELEVATION: ± 43' Above Mean Sea Level % P A S S I N G # 2 0 0 SI E V E SA M P L E O . D . ( i n ) DE P T H (f e e t ) SA M P L E DESCRIPTION AND REMARKS (Grain Size, Density, Moisture, Color) REVIEWED BY: LDR/JAC GROUNDWATER/SEEPAGE DEPTH: Not Encountered FIELD DESCRIPTION AND CLASSIFICATION U. S . C . S IN - P L A C E MO I S T U R E ( % ) IN - P L A C E D R Y DE N S I T Y ( p c f ) EX P A N S I O N I N D E X OP T I M U M MO I S T U R E ( % ) MA X I M U M D R Y DE N S I T Y ( p c f ) DE N S I T Y ( % o f MD D ) EX P A N ( + % ) CO N S O L ( - % ) SILTY SAND, fine to medium grained, loose to medium dense, slightly moist, dark brown, some roots.1 2 3 Bottom of Excavation at 3.5 ft. @ 1 ft. trash, glass, plastic, brick. 6 Artificial Fill (Qaf) Terrace Deposits (Qop6-7) 4 5 @3 ft. Becomes dense. SAND to SILTY SAND, fine to medium grained, loose to medium dense, moist brown. 7 8 No Groundwater, No Caving, Backfilled with Cuttings 9 12 10 11 13 14 16 15 18 17 20 19 21 FOOTING * DISTURBED BLOWCOUNT JOB NUMBER: 23-14403 FIGURE NO. IIIdIN-PLACE HAND-DRIVE SAMPLE STANDARD PENETRATION TEST LOG NO.HP 4JOB NAME: Tyler Street Homes SITE LOCATION: 3215-3225 Tyler Street, Carlsbad, CA PERCHED WATER TABLE BULK BAG SAMPLE IN-PLACE SAMPLE MODIFIED CALIFORNIA SAMPLE ◄~~-a ~ Geotechnical Exploration, Inc. - - - - -:l:lll~ll - -\ I - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ---- ---= SY M B O L FT G . D E P T H BL O W S / 6" SM SM 1 3.6 124.5 26 1 H U. S . C . S IN - P L A C E MO I S T U R E ( % ) EX P A N S I O N I N D E X OP T I M U M MO I S T U R E ( % ) MA X I M U M D R Y DE N S I T Y ( p c f ) DE N S I T Y ( % o f MD D ) EX P A N ( + % ) CO N S O L ( - % ) IN - P L A C E D R Y DE N S I T Y ( p c f ) EQUIPMENT: Hand Tools DIMENSION & TYPE OF EXCAVATION: 1.5'x2'x2.5'DATE LOGGED: August 17, 2023 LOGGED BY: HE SURFACE ELEVATION: ± 43' Above Mean Sea Level % P A S S I N G # 2 0 0 SI E V E SA M P L E O . D . ( i n ) DE P T H (f e e t ) SA M P L E DESCRIPTION AND REMARKS (Grain Size, Density, Moisture, Color) REVIEWED BY: LDR/JAC GROUNDWATER/SEEPAGE DEPTH: Not Encountered FIELD DESCRIPTION AND CLASSIFICATION Artificial Fill (Qaf) SILTY SAND, fine to medium grained, medium dense, slightly moist, brown, porous.3 1 2 SILTY SAND, loose to medium dense, slightly moist, light brown, debris, ac fragments. 4 5 6 No Groundwater, No Caving, Backfilled with Cuttings @2.5 Ft. Becomes dense, moist. Bottom of Excavation at 2.5 ft. Terrace Deposits (Qop6-7) 9 7 8 12 10 11 13 14 16 15 18 17 20 19 21 FOOTING * DISTURBED BLOWCOUNT JOB NUMBER: 23-14403 FIGURE NO. IIIeIN-PLACE HAND-DRIVE SAMPLE STANDARD PENETRATION TEST LOG NO.HP 5JOB NAME: Tyler Street Homes SITE LOCATION: 3215-3225 Tyler Street, Carlsbad, CA PERCHED WATER TABLE BULK BAG SAMPLE IN-PLACE SAMPLE MODIFIED CALIFORNIA SAMPLE ◄~~-a ~ Geotechnical Exploration, Inc. - \ I - I I - - - - - - - - - - - - - ---- _C __ ______._ _ _____.._________. SY M B O L FT G . D E P T H BL O W S / 6" SM SM 1 H EQUIPMENT: Hand Tools DIMENSION & TYPE OF EXCAVATION: 2'x2'x5.5'DATE LOGGED: August 17, 2023 LOGGED BY: HE SURFACE ELEVATION: ± 43' Above Mean Sea Level % P A S S I N G # 2 0 0 SI E V E SA M P L E O . D . ( i n ) DE P T H (f e e t ) SA M P L E DESCRIPTION AND REMARKS (Grain Size, Density, Moisture, Color) REVIEWED BY: LDR/JAC GROUNDWATER/SEEPAGE DEPTH: Not Encountered FIELD DESCRIPTION AND CLASSIFICATION U. S . C . S IN - P L A C E MO I S T U R E ( % ) IN - P L A C E D R Y DE N S I T Y ( p c f ) OP T I M U M MO I S T U R E ( % ) MA X I M U M D R Y DE N S I T Y ( p c f ) DE N S I T Y ( % o f MD D ) EX P A N ( + % ) CO N S O L ( - % ) 1 2 EX P A N S I O N I N D E X SILTY SAND, fine to medium grained, loose to medium dense, slightly moist, dark brown, some roots. @ 1 ft. trash, glass, plastic, brick. Artificial Fill (Qaf) 3 4 5 @3 ft. Becomes dense. SAND to SILTY SAND, fine to medium grained, loose to medium dense, moist brown. Terrace Deposits (Qop6-7) 6 hand augered from 3 to 5 ft. No Groundwater, No Caving, Backfilled with Cuttings Bottom of Excavation at 5.5 ft. 9 7 8 12 10 11 13 14 16 15 18 17 20 19 21 FOOTING * DISTURBED BLOWCOUNT JOB NUMBER: 23-14403 FIGURE NO. IIIfIN-PLACE HAND-DRIVE SAMPLE STANDARD PENETRATION TEST LOG NO.HP-6JOB NAME: Tyler Street Homes SITE LOCATION: 3215-3225 Tyler Street, Carlsbad, CA PERCHED WATER TABLE BULK BAG SAMPLE IN-PLACE SAMPLE MODIFIED CALIFORNIA SAMPLE ◄~~-a ~ Geotechnical Exploration, Inc. - - - \ ) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ---- ---= Compaction Curve HP-3 Depth:1.5-2.5 ft. Description of Material:Silty Sand Dark Brown Test Method:ASTM D1557 Method A Maximum Dry Density (PCF)128.7 Optimum Water Content (%)8.0 Expansion Index (EI)NA % Passing #200 23 Coarse Material (%)0.0 Corrected Maximum Dry Density (PCF)0.0 Corrected Optimum Water Content (%)0.0 Curves of 100% Saturation for Specific Gravity Equal to: 2.80 2.70 2.60 Source of Material: ROCK CORRECTION TEST RESULTS MOISTURE-DENSITY RELATIONSHIP Figure Number: IVa Tyler Street Homes 3215-3225 Tyler Street, Carlsbad, CA Job No. 23-14403 90 100 110 120 130 140 150 0 5 10 15 20 25 30 Dr y D e n s i t y ( p c f ) Moisture Content (%) 2.60 2.70 2.80 \ ' \ \ ' \ \ \ \ I\ ' \ \ ' \ \ \ \ \ \ \ \ \ \ \ ' \ \ \ ' \ ' ' \ \ ' \ ' ' \ V' ?"'-\ ,n " I\ \ ~ \ \ J .\ \ l I \ I\ \ ' I \ \ \ \ -, \ \ \ ' \ \ \ \ \ \ I\ \ \ -, \ \ \ \ I\ ' r, I\ ' \ \ \~ I\ I\ ' \ I\ I\ \ ' \ I\ I\ I\ \ \. \ I\ \ ti. I\ \ \ \ \._ \ I\ \ \ ' I\. \. \ "\ \. \ \ i\. \ \. 4~&, ► Geotechnical I Exploration, Inc. -~ '/ ~ Source of MaterialLocation & Depth U.S.C.S. Color 129.4 8.4 N/A N/A N/A Curves of 100% saturation for specific gravity equal to: 2.80 2.70 2.60 Corrected Optimum Moisture Content (%) Corrected Maximum Dry Density (pcf) Optimum Moisture Content (%) FIGURE NO. IVb JOB NAME: Tyler Street Homes SITE LOCATION: 3215-3225 Tyler Street, Carlsbad, CA MOISTURE-DENSITY RELATIONSHIP JOB NUMBER: 23-14403 Expansion Index (E.I.) TEST RESULTS Maximum Dry Density (PCF) Test Method LABORATORY TEST RESULTS On-site S-1 @ 0 to 1' SILTY SAND (SM) ASTM D1557-12(2021) Method A Dark Brown 90 95 100 105 110 115 120 125 130 135 140 145 150 0 5 10 15 20 25 30 Dr y D e n s i t y ( p c f ) Moisture Content (%) Standard Test Method for Laboratory Compaction Charaterisitics of Soil Using Modified Effort \ ' \ \ ' ' \ \ \ ' \ \ \ ' \ \ \ \ \ \ \ \ \ \ \ \ \ I I\ ' \ ' \ .\ \ \ ' \ ' \ ' I\ \ I\ , -~~~---~---~~-,➔1-1,-\--~~-~-------- -+-+-+-+-l-l-l-l-t----lt----lt----lt----lr-'.--, \ \ \ \ ' -\ \ -!-:-,-1--11--11--11--11--1--1,--:-:--:--:--+--v--l'r\-l-'.-i--+--l-:-1-HHHHH---I \ I\ \ ' \ ' \ ' '"""1--1:----:---:--1----:--1--;--1--1-:•-,--:--:--+--:-+-:-'r\-+-''d---'il\.-:•-:--:-+-:--:--:-+-1 I\ I\ ' \ I\ I\ \ ' \ I\ I\ \ ' I\ \ I\ \ \ .\ \ := Geotechnical Exploration, Inc. Source of MaterialLocation & Depth U.S.C.S. Color 120.0 10.2 N/A N/A N/A Curves of 100% saturation for specific gravity equal to: 2.80 2.70 2.60 Corrected Optimum Moisture Content (%) Corrected Maximum Dry Density (pcf) Optimum Moisture Content (%) FIGURE NO. IVc JOB NAME: Tyler Street Homes SITE LOCATION: 3215-3225 Tyler Street, Carlsbad, CA MOISTURE-DENSITY RELATIONSHIP JOB NUMBER: 23-14403 Expansion Index (E.I.) TEST RESULTS Maximum Dry Density (PCF) Test Method LABORATORY TEST RESULTS On-site S-2 @ 0 to 1' SILTY SAND (SM) ASTM D1557-12(2021) Method A Dark Brown 90 95 100 105 110 115 120 125 130 135 140 145 150 0 5 10 15 20 25 30 Dr y D e n s i t y ( p c f ) Moisture Content (%) Standard Test Method for Laboratory Compaction Charaterisitics of Soil Using Modified Effort \ ' \ \ ' ' \ \ \ ' \ \ \ ' \ \ \ \ \ \ \ \ \ \ \ \ \ I I\ ' \ ' \ .\ \ ' I\ \ I \ \ ' I\ I\ ' \ I\ I\ \ ' \ I\ I\ \ ' \ \ I\ \ \ .\ \ := Geotechnical Exploration, Inc. LABORATORY TEST RESULTS FIGURE NO. IVd JOB NAME: Tyler Street Homes SITE LOCATION: 3215-3225 Tyler Street, Carlsbad, CA DIRECT SHEAR JOB NUMBER: 23-14403 U.S.C.S. / Description SILTY SAND (SM) / Dark Brown SILTY SAND (SM) / Dark Brown 30.7 Cohesion (psf)201.98 173.12 On-site Material Remolded to 90% MDD at 3% over the optimum; Saturated, Peak Stress Symbol Sample No.S-1 S-1 Sample Location On-site Material Friction Angle ᶲ (degrees)34.2 Test Method Remolded to 90% MDD at 3% over the optimum; Unsaturated, Peak Stress 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 0 500 1000 1500 2000 2500 3000 3500 4000 4500 Sh e a r S t r e n g t h ( p s f ) Normal Load (psf) Standard Test Method for Direct Shear Tests of Soils -+--+- 4~~= Geotechnical Exploration, Inc. ~ SITE PACIFIC OCEAN Figure No. V Job No. 23-14403 TYLER-ST-HOMES-GEO-OC.ai Proposed Tyler Street Homes 3215-3225 Tyler Street Carlsbad, CA. DESCRIPTION OF MAP UNITS Qop Quartenary Old Paralic Deposits, Unit 6-76-7 EXCERPT FROM Quartenary Old Paralic Deposits, Unit 2-4 Qop2-4 Qvop Very Old Paralic Deposits, Unit 13 13 Qvop Very Old Paralic Deposits, Unit 12 12 Tsa Santiago Formation September 2023 ONSHORE MAP SYMBOLS Contact - Contact between geologic units; dotted where concealed. Fault - Solid where accurately located; dashed where approximately located; dotted where concealed. U = upthrown block, D = downthrown block. Arrow and number indicate direction and angle of dip of fault plane. Anticline - Solid where accurately located; dashed where approximately located; dotted where concealed. Arrow indicates direction of axial plunge. Syncline - Solid where accurately located; dotted where concealed Arrow indicates direction of axial plunge. Landslide - Arrows indicate principal direction of movement. Quired where existence is questionable Strike and dip of beds Inclined Inclined Inclined Strike and dip of igneous foliation Strike and dip of metamorphic foliation Kgp - Granite pegmatite dike. Overturned Vertical Horizontal Vertical Strike and dip of igneous joints Inclined Vertical Strike and dip of sedimentary joints Vertical Base Map Onshore base (hypsography, hydrography, and transportation) from U.S.G.S. digital line graph (DLG) data, Oceanside 30' x 60' metric quadrangle. Shaded topographic base from U.S.G.S. digital elevation models (OEM's). Offshore bathymetric contours and shaded bathymetry from N.O.A.A. single and multibeam data. Projection is UTM, zone 11, North American Datum 1927. EUSGS sclencefof11changlngworld This map was funded in part by the U.S. Geological Survey National Cooperative Geologic Mapping Program, STATEMAP Award no. 01NQAG0092. Prepared in cooperation with the U.S. Geological Survey, Southern California Areal Mapping Project. Copyright C 2007 by the California Department of Conservation. All rights reserved. No part of this publication may be reproduced without written consent of the California Geological Survey. The Department of Conservation makes no warranties as to the suitability of this product for any particular purpose. GEOLOGIC MAP OF THE OCEANSIDE 30' x 60' QUADRANGLE, CALIFORNIA Compiled by 70 _L_~----D t t ........-..-<!!>..... C:) © 70 ---'--- 70 -b-- -+- EB ~ -+- 60 -&- 55 ......_ --- '- Michael P. Kennedy1 and Siang S. Tan 1 2007 Digital preparation by Kelly R. Bovard2, Rachel M. Alvarez2, Michael J. Watson2, and Carlos I. Gutierrez1 1. Department of Conservation, California Geological Survey 2. U.S. Geological Survey, Department of Earth Sciences, University of California, Riverside -~-, $ Geotechnical Exploration, Inc. RECOMMENDED RETAINING WALL DRAINAGE SCHEMATIC Seal to 6 Inches above ·:--_.::,:;:,:>-/V�¾�'" :,"-f /\): Miradrai: 6000 /-. /,... " ... . ·• .... . >r:�·?:;;,:<} .. ;�. • ..... "i .;� .· .. }··:�·;:�< 'I_:/_:�.:: Exterior Footing/· ::.·. •_.: · Retaining Wall ./·c·�:� �\_\./, {:'{) ��: .. �--:� .. �t:·r\?�: :: :�•:· ... :�: __ )· ,; . · .. · ... ,;. .· ... :� .. : �::•. :·.:-:·� ·.� � .. ·;)·.: ::·: .. ··-�-� Sealant ... ·. .•. Waterproofing To Top Of Wall Sealant Properly Compacted Backfill ����..,......,,.�����,........,,,-:;'·: ... •.:.,·-�· Perforated PVC Schedule 40 or SOR 3" diameter pipe with 0.5%min. slope with bottom of pipelocated 12" below bottom of garage slab elevation, with 1.5 (cu.ft.) of gravel 1" diameter max.wrapped with filter cloth such as Mirafi 140N. Ameridrain, Quickdrain, J-Drain or equivalent may be usedas an alternative to a perforated pipe and gravel drain.: ◄ �-· .. · . . •.: .: �-: &?"R ;IrF{\\!\\�:){ti(\''!{/ NOTTO SCALE 23-14403-VI.dwg T Between Bottom12" of Slab and1 Pipe Bottom Mirafi 140N Filter Cloth .,.. • Figure No. VI Job No. 23-14403 Geotecl,nicel :: I &plon,tion, Inc. � October 2023 adjacent ground level --~~-·--~:; / Min. 2% Fall Away - Slab-on-grade \ , ' . "' Coarse-grained (More than half of material is larger than a No. 200 sieve) GRAVELS, CLEAN GRAVELS GW Well-graded gravels, gravel and sand mixtures, little (More than half of coarse fraction or no fines. is larger than No. 4 sieve size, but smaller than 3”) GP Poorly graded gravels, gravel and sand mixtures, little or no fines. GRAVELS WITH FINES GC Clay gravels, poorly graded gravel-sand-silt mixtures (Appreciable amount) SANDS, CLEAN SANDS SW Well-graded sand, gravelly sands, little or no fines (More than half of coarse fraction is smaller than a No. 4 sieve) SP Poorly graded sands, gravelly sands, little or no fines. SANDS WITH FINES SM Silty sands, poorly graded sand and silty mixtures. (Appreciable amount) SC Clayey sands, poorly graded sand and clay mixtures. Fine-grained (More than half of material is smaller than a No. 200 sieve) SILTS AND CLAYS Liquid Limit Less than 50 ML Inorganic silts and very fine sands, rock flour, sandy silt and clayey-silt sand mixtures with a slight plasticity CL Inorganic clays of low to medium plasticity, gravelly clays, silty clays, clean clays. OL Organic silts and organic silty clays of low plasticity. Liquid Limit Greater than 50 MH 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. HIGHLY ORGANIC SOILS PT Peat and other highly organic soils APPENDIX A UNIFIED SOIL CLASSIFICATION CHART SOIL DESCRIPTION APPENDIX B REGIONAL GEOLOGIC DESCRIPTION In the Coastal Plain region, the “basement” consists of Mesozoic crystalline rocks. Basement rocks are also exposed as high relief areas (e.g., Black Mountain northeast of the subject property and Cowles Mountain near the San Carlos area of San Diego). Younger Cretaceous and Tertiary sediments lap up against these older features. These sediments form a “layer cake” sequence of marine and non-marine sedimentary rock units, with some formations up to 140 million years old. Faulting related to the La Nación and Rose Canyon Fault zones has broken up this sequence into a number of distinct fault blocks in the southwestern part of the county. Northwestern portions of the county are relatively undeformed by faulting (Demere, 1997). The Peninsular Range forms the granitic spine of San Diego County. These rocks are primarily plutonic, forming at depth beneath the earth’s crust 140 to 90 million years ago as the result of the subduction of an oceanic crustal plate beneath the North American continent. These rocks formed the much larger Southern California batholith. Metamorphism associated with the intrusion of these great granitic masses affected the much older sediments that existed near the surface over that period of time. These metasedimentary rocks remain as roof pendants of marble, schist, slate, quartzite and gneiss throughout the Peninsular Ranges. Locally, Miocene-age volcanic rocks and flows have also accumulated within these mountains (e.g., Jacumba Valley). Regional tectonic forces and erosion over time have uplifted and unroofed these granitic rocks to expose them at the surface (Demere, 1997). The Salton Trough is the northerly extension of the Gulf of California. This zone is undergoing active deformation related to faulting along the Elsinore and San Jacinto Fault Zones, which are part of the major regional tectonic feature in the southwestern portion of California, the San Andreas Fault Zone. Translational movement along these fault zones has resulted in crustal rifting and subsidence. The Salton Trough, also referred to as the Colorado Desert, has been filled with sediments to depth of approximately 5 miles since the movement began in the early Miocene, 24 million years ago. The source of these sediments has been the local mountains as well as the ancestral and modern Colorado River (Demere, 1997). The San Diego area is part of a seismically active region of California. It is on the eastern boundary of the Southern California Continental Borderland, part of the Peninsular Ranges Geomorphic Province. This region is part of a broad tectonic boundary between the North American and Pacific Plates. The actual plate boundary is characterized by a complex system of active, major, right-lateral strike-slip faults, trending northwest/southeast. This fault system extends eastward to the San Andreas Fault (approximately 70 miles from San Diego) and westward to the San i i APPENDIX B/Page 2 Clemente Fault (approximately 50 miles off-shore from San Diego) (Berger and Schug, 1991). In California, major earthquakes can generally be correlated with movement on active faults. The three-tier fault classification used by the City of San Diego is as follows: • Active Faults: This class of faults has had demonstrable surface displacement during Holocene time. • Potentially Active Faults: These are faults with Quaternary displacement but Holocene surface displacement is indeterminate. • Inactive Faults: These are pre-Quaternary faults. During recent history, prior to April 2010, the San Diego County area has been relatively quiet seismically. The youngest paleoearthquake that cuts the early historical living surface is likely the 1862 San Diego earthquake that had an estimated magnitude of M6 (Legg and Agnew, 1979; Singleton et al., 2019). Paleoseismic trenches at the Presidio Hills Golf Course on the main trace of the Rose Canyon Fault contained evidence for historical ground rupturing earthquakes as recently as 1862 and the mid-1700s. Results of the study also suggest the Rose Canyon Fault has a ~700-800-year recurrence interval (Singleton et al., 2019). On June 15, 2004, a M5.3 earthquake occurred approximately 45 miles southwest of downtown San Diego (26 miles west of Rosarito, Mexico). Another widely felt earthquake on a distant southern California fault was a M5.4 event that took place on July 29, 2008, west-southwest of the Chino Hills area of Riverside County. Several earthquakes ranging from M5.0 to M6.0 occurred in northern Baja California, centered in the Gulf of California on August 3, 2009. A M5.8 earthquake followed by a M4.9 aftershock occurred on December 30, 2009, centered about 20 miles south of the Mexican border city of Mexicali. On April 04, 2010, a large earthquake occurred in Baja California, Mexico. It was widely felt throughout the southwest including Phoenix, Arizona and San Diego in California. This M7.2 event, the Sierra El Mayor earthquake, occurred in northern Baja California, approximately 40 miles south of the Mexico-USA border at shallow depth along the principal plate boundary between the North American and Pacific plates. According to the U.S. Geological Survey this is an area with a high level of historical seismicity, and it has recently also been seismically active, although this is the largest event to strike in this area since 1892. The April 04, 2010, earthquake appears to have been larger than the M6.9 earthquake in 1940 or any of the early 20th century events (e.g., 1915 and 1934) in this region of northern Baja California. APPENDIX B/Page 3 This event's aftershock zone extends significantly to the northwest, overlapping with the portion of the fault system that is thought to have ruptured in 1892. Ground motions for the April 04, 2010, main event, recorded at stations in San Diego and reported by the California Strong Motion Instrumentation Program (CSMIP), ranged up to 0.058g. On July 07, 2010, a M5.4 earthquake occurred in Southern California at 4:53 pm (Pacific Time) about 30 miles south of Palm Springs, 25 miles southwest of Indio, and 13 miles north-northwest of Borrego Springs. The earthquake occurred near the Coyote Creek segment of the San Jacinto Fault. The earthquake exhibited right lateral slip to the northwest, consistent with the direction of movement on the San Jacinto Fault. It was followed by more than 60 aftershocks of M1.3 and greater during the first hour. In the last 50 years, there have been four other earthquakes in the magnitude M5.0 range within 20 kilometers of the Coyote Creek segment: M5.8 in 1968, M5.3 on 2/25/1980, M5.0 on 10/31/2001, and M5.2 on 6/12/2005. The biggest earthquake near this location was the M6.0 Buck Ridge earthquake on 3/25/1937. i i Tyler Street Homes 3215 Tyler St, Carlsbad, CA 92008, USA Latitude, Longitude: 33.1572911, -117.3467049 Date 10/4/2023, 7:14:14 PM Design Code Reference Document ASCE7-16 Risk Category II Site Class D - Stiff Soil Type Value Description SS 1.083 MCER ground motion. (for 0.2 second period) S1 0.391 MCER ground motion. (for 1.0s period) SMS 1.155 Site-modified spectral acceleration value SM1 null -See Section 11.4.8 = 0.746 Site-modified spectral acceleration value SDS 0.77 Numeric seismic design value at 0.2 second SA SD1 null -See Section 11.4.8 = 0.498 Numeric seismic design value at 1.0 second SA Type Description SDC Value null -See Section 11.4.8= D Seismic design category Fa 1.067 Site amplification factor at 0.2 second Fv null -See Section 11.4.8 = 1.909 Site amplification factor at 1.0 second PGA 0.478 MCEG peak ground acceleration FPGA 1.122 Site amplification factor at PGA PGAM 0.536 Site modified peak ground acceleration TL 8 Long-period transition period in seconds SsRT 1.083 Probabilistic risk-targeted ground motion. (0.2 second) SsUH 1.212 Factored uniform-hazard (2% probability of exceedance in 50 years) spectral acceleration SsD 1.5 Factored deterministic acceleration value. (0.2 second) S1RT 0.391 Probabilistic risk-targeted ground motion. (1.0 second) S1UH 0.432 Factored uniform-hazard (2% probability of exceedance in 50 years) spectral acceleration. S1D 0.6 Factored deterministic acceleration value. (1.0 second) PGAd 0.585 Factored deterministic acceleration value. (Peak Ground Acceleration) PGAUH 0.478 Uniform-hazard (2% probability of exceedance in 50 years) Peak Ground Acceleration CRS 0.894 Mapped value of the risk coefficient at short periods CR1 0.905 Mapped value of the risk coefficient at a period of 1 s CV 1.317 Vertical coefficient APPENDIX C 264 Fresco ' q Carlsbad City Beach Board & Brew -' Carlsbad Village Go gle 'Harbor Fish Cafe .... ' ' t ' ~o -:> \fl ola's 7 Up~ ,.. Market & Deli T OS HPD Pine Pk Chase Fld 9 ' ' ,, 0 ~e Casa Montessori ~~ ~ de Carlsbrirl o~ . ' ' ' Map data ©2023 Google APPENDIX D SLAB MOISTURE INFORMATION AND VAPOR BARRIER MEMBRANES Soil moisture vapor can result in damage to moisture-sensitive floors, some floor sealers, or sensitive equipment in direct contact with the floor, in addition to mold and staining on slabs, walls and carpets. The common practice in Southern California is to place vapor retarders made of PVC, or of polyethylene. PVC retarders are made in thickness ranging from 10- to 60-mil. Polyethylene retarders, called visqueen, range from 5- to 10-mil in thickness. These products are no longer considered adequate for moisture protection and can actually deteriorate over time. Specialty vapor retarding and barrier products possess higher tensile strength and are more specifically designed for and intended to retard moisture transmission into and through concrete slabs. The use of such products is highly recommended for reduction of floor slab moisture emission. The following American Society for Testing and Materials (ASTM) and American Concrete Institute (ACI) sections address the issue of moisture transmission into and through concrete slabs: ASTM E1745-09 Standard Specification for Plastic Water Vapor Retarders Used in Contact Concrete Slabs; ASTM E1643-18a Standard Practice for Selection, Design, Installation, and Inspection of Water Vapor Retarders Used in Contact with Earth or Granular Fill Under Concrete Slabs; ACI 302.2R-06 Guide for Concrete Slabs that Receive Moisture-Sensitive Flooring Materials; and ACI 302.2R- 06 Guide to Concrete Floor and Slab Construction. Based on the above, we recommend that the vapor barrier consist of a minimum 15- mil extruded polyolefin plastic (no recycled content or woven materials permitted). Permeance as tested before and after mandatory conditioning (ASTM E1745 Section 7.1 and subparagraphs 7.1.1-7.1.5) should be less than 0.01 perms (grains/square foot/hour/per inch of Mercury) and comply with the ASTM E1745-09 Class A requirements. Installation of vapor barriers should be in accordance with ASTM E1643-18a. The basis of design is 15-mil StegoWrap vapor barrier placed per the manufacturer’s guidelines. Reef Industries Vapor Guard membrane has also been shown to achieve a permeance of less than 0.01 perms. We recommend that the slab be poured directly on the vapor barrier, which is placed directly on the prepared properly compacted smooth subgrade soil surface. Common to all acceptable products, vapor retarder/barrier joints must be lapped at least 6 inches. Seam joints and permanent utility penetrations should be sealed with the manufacturer’s recommended tape or mastic. Edges of the vapor retarder should be extended to terminate at a location in accordance with ASTM E1643-18a or to an alternate location that is acceptable to the project’s structural engineer. All terminated edges of the vapor retarder should be sealed to the building foundation i i APPENDIX D/Page 2 (grade beam, wall, or slab) using the manufacturer’s recommended accessory for sealing the vapor retarder to pre-existing or freshly placed concrete. Additionally, in actual practice, stakes are often driven through the retarder material, equipment is dragged or rolled across the retarder, overlapping or jointing is not properly implemented, etc. All these construction deficiencies reduce the retarder’s effectiveness. In no case should retarder/barrier products be punctured or gaps be allowed to form prior to or during concrete placement. Vapor barrier-safe screeding and forming systems should be used that will not leave puncture holes in the vapor barrier, such as Beast Foot (by Stego Industries) or equivalent. Vapor retarders/barriers do not provide full waterproofing for structures constructed below free water surfaces. They are intended to help reduce or prevent vapor transmission and/or capillary migration through the soil and through the concrete slabs. Waterproofing systems must be designed and properly constructed if full waterproofing is desired. The owner and project designers should be consulted to determine the specific level of protection required. Following placement of any concrete floor slabs, sufficient drying time must be allowed prior to placement of floor coverings. Premature placement of floor coverings may result in degradation of adhesive materials and loosening of the finish floor materials. i i APPENDIX E Additional Geotechnical Documents 111 Infiltration Feasibility Condition Report 111 29 January 2024 Mr. John Norum Job No. 23-14403 KMJ Real Estate 2888 Loker Avenue East, Suite 220 Carlsbad, CA 92010 Subject: Infiltration Feasibility Condition Tyler Street Homes 3215-3225 Tyler Street Carlsbad, California Dear Mr. Norum: In accordance with your request and our work agreement of November 21, 2023, Geotechnical Exploration, Inc. has prepared this letter regarding the infiltration feasibility conditions at the subject property. Our infiltration feasibility evaluation is based on the findings and opinions in our “Report of Preliminary Geotechnical Investigation,” dated January 29, 2024, review of the geologic map for the subject property, review of the USDA Web Soil Survey, our infiltration testing results, as well as our past experience with materials similar to those encountered at the site. In preparation of this letter, we also reviewed the Site Plan prepared by Kirk Moeller Architects, dated January 15, 2024. It is our understanding that the existing single-story structures and adjacent parking area are to be removed to construct 12 three-story residential structures consisting of four triplexes, as well as BMPs and associated improvements. Refer to Figure No. I, Vicinity Map, for the location of the site. Refer to the Plot Plan and Site-Specific Geologic Map, Figure No. II, for proposed site development and other information. 4~~-Geotechnical Exploration, Inc. SOIL AND FOUNDATION ENGINEERING • GROUNDWATER • ENGINEERING GEOLOGY 7420 TRADE STREET• SAN DIEGO, CA. 92121 • (858) 549-7222 • FAX: (858) 549-1604 • EMAIL: geotech@gei-sd.com Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 2 Currently, the site is occupied by four (4) single-story residential structures with associated exterior improvements, a shed structure, a concrete driveway, a parking area, and some mature vegetation. The site has remained relatively unchanged and no additional grading has occurred since our preliminary investigation. The property is approximately 0.51-acre in size (22,345 square feet). The relatively level square lot descends slightly to the northeast, with site elevations ranging from 44 feet above Mean Sea Level (MSL) along the eastern property line to approximately 46 feet above MSL at the western property line. Information concerning approximate elevations across the site was obtained from a Topographic Survey Map by PLSA Engineering dated August, 10, 2022. This map has also been utilized for the Plot Plan and Site- Specific Geologic Map, Figure No. II. The Geologic Map of the Oceanside 30'x60' Quadrangle, California by Kennedy and Tan, 2007, indicates that the subject site is located in an area underlain by Quaternary (late to middle Pleistocene) Old Paralic Deposits Unit 6-7 (Qop6-7) described as “Poorly sorted, moderately permeable, reddish-brown, interfingered strandline, beach, estuarine and colluvial deposits composed of siltstone, sandstone and conglomerate.” The encountered soil profile in the tested areas of the property consists of approximately 1 foot of silty sand fill soils overlying the Old Paralic Deposits, Unit 6-7 (Qop6-7) formational materials. According to the USDA Web Soil Survey, the on-site soils across the entire subject site is mapped as belonging to Hydrologic Group B, described as “soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission.” Refer to Appendix A, USDA Web Soil Survey Map. i i Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 3 We performed preliminary water infiltration testing on November 30, 2023, for the design of the potential storm water infiltration BMPs associated with the current development and improvements. Two infiltration test borings were excavated outside the footprint of the proposed residential structures where accessible. Based on the prepared plans, we understand that this is the most feasible location on the property. The field investigation consisted of a surface reconnaissance for the potential of infiltration BMPs on the subject property and a subsurface exploration program using hand tools to investigate the subsurface soils. The two borings (INF- 1 and INF-2) for percolation testing were excavated into the formational materials to a depth of 3.5 feet. Based on our laboratory test results of the silty sand (SM) formational materials, 24% (INF-1) and 25% (INF-2) of the soils passed the No. 200 sieve (ASTM D1140-17). Testing at INF-1 revealed falling head rates of 10.0 minutes/inch. The percolation test rate result for INF-1 was converted to an infiltration rate using the Porchet Method, and indicates an infiltration rate of 0.514-inch/hour, with temperature correction and without a factor of safety applied. Testing at INF-2 revealed falling head rates of 14.286 minutes/inch. The percolation test rate result for INF-2 was converted to an infiltration rate using the Porchet Method, and indicates an infiltration rate of 0.357-inch/hour, with temperature correction and without a factor of safety applied. It is our opinion this infiltration rate reflects the rates consistent with the site. Refer to Appendix B for percolation test rate and percolation rate to infiltration rate conversion calculations. Based on review of our previous geotechnical report for the site dated October 19, 2023, the current conceptual site plan, our recent site observations and water infiltration testing results, as well as our past experience with materials similar to those encountered at the site, it is our professional opinion that the design of full or partial storm water infiltration BMPs is not considered feasible on the subject site. i i Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 4 Our conclusion is also based upon the 2023 City of Carlsbad BMP Design Manual, Appendix D, Section D.1 “Analysis of Infiltration Restrictions” and the following considerations for geotechnical analysis of infiltration restrictions: Section D.1, Table D.1-1, of the above referenced BMP Design Manual Appendices states restrictions for consideration “BMP is within 10’ of Structures/Tanks/Walls.” As such, we recommend the proposed infiltration be placed at least 10 feet from structures (foundations) and walls. Based on the proposed plans, this restriction consideration cannot be resolved. Section D.1, Table D.1-1, of the above referenced BMP Design Manual Appendices states restrictions for consideration “BMP is within 10’ of Sewer Utilities.” As such, we recommend the proposed infiltration be placed at least 10 feet from sewer utilities. Based on the proposed plans, this restriction consideration cannot be resolved. Section D.1, Table D.1-1, of the above referenced BMP Design Manual Appendices states restrictions for consideration “BMP is within 10’ of underground Utilities.” As such, we recommend the proposed infiltration be placed at least 10 feet from underground utilities. Based on the proposed plans, this restriction consideration cannot be resolved. Based on the proposed plans and conditions presented above, we recommend that a stormwater retention and treatment be designed for the subject site and discharged to an approved drainage facility. In addition, we recommend that any proposed storm water BMP basin in the planned location be lined with a minimum of 30-mil LDPE impermeable liner. i i Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 5 This opportunity to be of continued service is sincerely appreciated. If you have any questions concerning this matter, please contact our office. Reference to our Job No. 23-14403 will help to expedite a response to your inquiries. Respectfully submitted, GEOTECHNICAL EXPLORATION, INC. _______________________________ ______________________________ Jaime A. Cerros, P.E. Steve Osetek, Project Geologist Senior Geotechnical Engineer R.C.E. 34422/G.E. 2007 cc: Mr. Kirk Moeller, Kirk Moeller Architect VICINITY MAP Proposed Tyler Street Homes 3215-3225 Tyler Street Carlsbad, CA. Figure No. I Job No. 23-14403 SITE Thomas Guide San Diego County Edition pg 1106-E6 PACIFIC OCEAN w ~ KNOWLES AV _ _j_ci ?ii Ul D• U ::,0 U.. o "VISA¼:,,., w LJ. 0 0 ~•J a: w ~~I-' s: a:o.. ~~ POINT 2 SCENl1 3 LOREl 4 SAND Geotechnical Exploration, Inc. Approximate Location of Proposed Structures INF-1 Approximate Location of Infiltration Test INF-1 INF-2 HP-2 HP-3 HP-1 Approximate Location of Exploratory HandpitHP-6 HP-4 HP-5 HP-6 Artificial FillQaf Qop Very Old Paralic Deposits Units 6-76-7 GEOLOGIC LEGEND Qaf Qop 6-7 Qaf Qop6-7 Qaf Qop 6-7 Qaf Qop6-7 Proposed Tyler Street Homes 3215-3225 Tyler Street Carlsbad, CA. Figure No. II Job No. 23-14403 LEGEND PLOT PLAN AND SITE SPECIFIC GEOLOGIC MAP REFERENCE: This Plot Plan is not to be used for legal purposes. Locations and dimensions are approximate. Actual property dimensions and locations of utilities may be obtained from the Approved Building Plans or the “As-Built” Grading Plans.REFERENCE: This Plot Plan was prepared from a CONCEPTUAL SITE PLAN by KIRK MOELLER ARCHITECTS, INC. dated 1-15-24 on-site field reconnaissance performed by GEI.January 2024 N GRAPHIC SCALE 1” = 20’ ( approximate ) 0 10 20 4030 TYLER STREET 23-14403-INF-1-26-24 _j_ __ _ -~ CONCEPTUAL SITE PLAN PROPOSED BIKE RACK (E) F.H. PROPOSED SIDEWALK ~- ------------ PROPOSED BIKE RACK PROPOSED SIDEWALK (E) POWER POLE -1 -~, ~ llRKMOl':LURA•CHIHCT~.IHC. ~-BWUIIAVE.U.IIT,GTEHO CARL.&BAO,CA;iiOIO KIR,c@KHARCHIT'l:CT■IO<C.COM ?MH1l4••1H I r I wr~,--~~6ttaL , ~ I 1 en W ~I :ii!:~ ;I 0 w ffi :::C ~ i1 1-~::g ~I w(/)o QI W O:::N ~ ~ Wal ~w~ 0:: ..J <( ~ ;::'.i I~ :;;! 1->-0 91 ~ I~ ;i:: ,,.. ~ --w IQ >-v, '° C u_ ~ ~ 11,111N<( ::::l:J~ I.I. N CD e!: W M (/) "' ,----7 , ...I w I 1 ...J IO 0::: EXISTING ~ I I D >-N <( AUTOMOTIVE § I : I-M O FACILITY w 1 Q I I I Datt: 1-\>24 I L-P--- Prqed: TYLERST.HOMES I I a. I RIY!lionl: I g i I SITE I 1' PLAN I -A1.1 I i ::1~~LD~NJi -~ 7GAA7\Gc-.;, N -_..-N ~=====~ ----,:;--,,--- nr 1x-1 1 11 11 . i_..':l ,..,..-~-I I I _ ____ I I I<:: _ I I I ----I L ~'"!~ •I f--;:~ ~E~_:;- 1 I ----I I I<:. -I I I I ~ ::c1 ~ ..:J feC:: I I I 13'-11''-t I IT 11·-~· II 4'-0' 12'f ~ -a 7 I m z --< ~ ! i I I I I I§ I~ I n'l I "l ~ ril 1z 0 i' ~ c:,I ~ en c:: ~ ~ m -., m "' a: ~ "' ~ en :::; m JLqr-a ·-•o IL II]., .. '"" I D I< -I"~""'"'~~ ~ '~--;;:;:;,;., UNIT12 ~ I +/-2, 176 SF i \¼ ~PIC)J, C ' 1----- 1 L ___ _ ~ "j ____ ---OF LAND I ... ~ _;.11 __ _ PRIVATE YARD ~ ~ -.,, 13~-10· !a ~ ~ • EXISTING SELF STORAGE BUILDING ~ -~:a ~ Geotechnical Exploration, Inc. APPENDIX A USDA WEB SOIL SURVEY MAP Hydrologic Soil Group—San Diego County Area, California (Tyler Street Homes, Carlsbad) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 11/14/2023 Page 1 of 4 36 6 8 7 5 0 36 6 8 7 6 0 36 6 8 7 7 0 36 6 8 7 8 0 36 6 8 7 9 0 36 6 8 8 0 0 36 6 8 8 1 0 36 6 8 8 2 0 36 6 8 7 5 0 36 6 8 7 6 0 36 6 8 7 7 0 36 6 8 7 8 0 36 6 8 7 9 0 36 6 8 8 0 0 36 6 8 8 1 0 36 6 8 8 2 0 467630 467640 467650 467660 467670 467680 467690 467700 467710 467720 467730 467630 467640 467650 467660 467670 467680 467690 467700 467710 467720 467730 33° 9' 27'' N 11 7 ° 2 0 ' 4 9 ' ' W 33° 9' 27'' N 11 7 ° 2 0 ' 4 5 ' ' W 33° 9' 25'' N 11 7 ° 2 0 ' 4 9 ' ' W 33° 9' 25'' N 11 7 ° 2 0 ' 4 5 ' ' W N Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 11N WGS84 0 25 50 100 150Feet 0 5 10 20 30Meters Map Scale: 1:519 if printed on A landscape (11" x 8.5") sheet. Soil Map may not be valid at this scale. MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Rating Polygons A A/D B B/D C C/D D Not rated or not available Soil Rating Lines A A/D B B/D C C/D D Not rated or not available Soil Rating Points A A/D B B/D C C/D D Not rated or not available Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:24,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: San Diego County Area, California Survey Area Data: Version 19, Aug 30, 2023 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Mar 14, 2022—Mar 17, 2022 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Hydrologic Soil Group—San Diego County Area, California (Tyler Street Homes, Carlsbad) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 11/14/2023 Page 2 of 4 □ □ ( i l l l l I □ □ □ □ □ □ □ □ □ l l : □ ■ ■ Hydrologic Soil Group Map unit symbol Map unit name Rating Acres in AOI Percent of AOI MlC Marina loamy coarse sand, 2 to 9 percent slopes B 0.5 100.0% Totals for Area of Interest 0.5 100.0% Description Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long-duration storms. The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (A/D, B/D, and C/D). The groups are defined as follows: Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes. Rating Options Aggregation Method: Dominant Condition Hydrologic Soil Group—San Diego County Area, California Tyler Street Homes, Carlsbad Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 11/14/2023 Page 3 of 4USDA = Component Percent Cutoff: None Specified Tie-break Rule: Higher Hydrologic Soil Group—San Diego County Area, California Tyler Street Homes, Carlsbad Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 11/14/2023 Page 4 of 4~ APPENDIX B PERCOLATION TEST RATE AND PERCOLATION RATE TO INFILTRATION RATE CONVERSION CALCULATIONS 1125 1135 10 26.000 27.500 1.500 6.667 1135 1145 10 26.200 27.300 1.100 9.091 1145 1155 10 26.000 26.900 0.900 11.111 1155 1205 10 26.000 27.000 1.000 10.000 1205 1215 10 26.000 27.100 1.100 9.091 1215 1225 10 26.000 27.000 1.000 10.000 Date Excavated: 11/30/23 Depth of Test Hole:42" Percolation Test Sheet Project Name: Tyler Street Homes Tested By: SO Project No. 23-14403 Soil Classification: SM Falling Head Rate (min/inches) Test Hole No: INF-1 Test Hole Dia: 6" Initial Time (Minutes)Final Time (Minutes)Time interval (minutes) Initial Water Level (inches) Final Water Level (inches) Change in water (inches) 1128 1138 10 25.500 27.300 1.800 5.556 1138 1148 10 26.000 27.500 1.500 6.667 1148 1158 10 26.000 27.200 1.200 8.333 1158 1208 10 25.500 26.600 1.100 9.091 1208 1218 10 25.800 26.600 0.800 12.500 1218 1228 10 26.000 26.700 0.700 14.286 Date Excavated: 11/30/23 Depth of Test Hole: 42" Percolation Test Sheet Project Name: Tyler Street Homes Tested By: SO Project No. 23-14403 Soil Classification: SM Falling Head Rate (min/inches) Test Hole No: INF-2 Test Hole Dia: 6" Initial Time (Minutes)Final Time (Minutes)Time interval (minutes) Initial Water Level (inches) Final Water Level (inches) Change in water (inches) 1 42 10 26.000 27.500 16.000 14.500 1.500 15.250 3 270 335 0.806 2 42 10 26.200 27.300 15.800 14.700 1.100 15.250 3 198 335 0.591 3 42 10 26.000 26.900 16.000 15.100 0.900 15.550 3 162 341 0.475 4 42 10 26.000 27.000 16.000 15.000 1.000 15.500 3 180 340 0.529 5 42 10 26.000 27.100 16.000 14.900 1.100 15.450 3 198 339 0.584 6 42 10 26.000 27.000 16.000 15.000 1.000 15.500 3 180 340 0.529 in/hr °F ft2/s °F ft2/s in/hr 0.529 0.514Temperature Corrected Infiltration Rate: 58Average Daily Mean Temperature During Rainfall Months: Typical Rainfall Months: November to April 0.000012439Kinematic Viscosity of Water at 58°F (µTypical ): Kinematic Viscosity of Water at 60°F (µTest ):0.00001208 60 Initial Infiltration Rate (K test ): SITE LOCATION: 3215-3225 Tyler Streett, Carlsbad, CA TEST NO. INF-1 TEMPERATURE CORRECTED INFILTRATION RATE JOB NUMBER: 23-14403 JOB NAME: Tyler Street Homes Temperature During Percolation Testing: REVIEWED BY: JAC USCS SOIL CLASSIFICATION: SM Test No. EB Depth (inches) Δt (min) Water Depth 1 (inches) Water Depth 2 (inches) H 1 (inches) H 2 (inches) ΔH (inches) H avg (inches) r radius (inches) ΔHX60 Xr Δt*(r+2 h avg) In. Inf. rate (in/hr) CALCULATED BY: SO DIAMETER OF TEST HOLE: 6" PERCOLATION RATE TO INFILTRATION RATE CONVERSION PORCHET METHOD TEST DATE: Novemeber 30, 2023 TEST METHOD: Percolation Test TEMPERATURE: 60°F DEPTH OF TEST HOLE: 42" Initial Infiltration Rate: =∆ × × ∆ Corrected Infiltration Rate: T = T × (µ µ ) I ( ) I I --I ~ Geotechnical Exploration, Inc. ~ 1 42 10 25.500 27.300 16.500 14.700 1.800 15.600 3 324 342 0.947 2 42 10 26.000 27.500 16.000 14.500 1.500 15.250 3 270 335 0.806 3 42 10 26.000 27.200 16.000 14.800 1.200 15.400 3 216 338 0.639 4 42 10 25.500 26.600 16.500 15.400 1.100 15.950 3 198 349 0.567 5 42 10 25.800 26.600 16.200 15.400 0.800 15.800 3 144 346 0.416 6 42 10 26.000 26.700 16.000 15.300 0.700 15.650 3 126 343 0.367 in/hr °F ft2/s °F ft2/s in/hr CALCULATED BY: SO DIAMETER OF TEST HOLE: 6" PERCOLATION RATE TO INFILTRATION RATE CONVERSION PORCHET METHOD TEST DATE: Novemeber 30, 2023 TEST METHOD: Percolation Test TEMPERATURE: 60°F DEPTH OF TEST HOLE: 42" REVIEWED BY: JAC USCS SOIL CLASSIFICATION: SM Test No. EB Depth (inches) Δt (min) Water Depth 1 (inches) Water Depth 2 (inches) H 1 (inches) H 2 (inches) ΔH (inches) Typical Rainfall Months: November to April H avg (inches) r radius (inches) ΔHX60 Xr Δt*(r+2 h avg) In. Inf. rate (in/hr) Initial Infiltration Rate (K test ):0.367 TEMPERATURE CORRECTED INFILTRATION RATE Temperature During Percolation Testing:60 Kinematic Viscosity of Water at 60°F (µTest ):0.00001208 Average Daily Mean Temperature During Rainfall Months:58 Kinematic Viscosity of Water at 58°F (µTypical ):0.000012439 Temperature Corrected Infiltration Rate: 0.357 JOB NUMBER: 23-14403 JOB NAME: Tyler Street Homes SITE LOCATION: 3215-3225 Tyler Streett, Carlsbad, CA TEST NO. INF-2 Initial Infiltration Rate: =∆ × × ∆ Corrected Infiltration Rate: T = T × (µ µ ) I ( ) I I --I ~ Geotechnical Exploration, Inc. ~ Grading Plan Review Conformance Letter 111 20 January 2025 (REVISED 22 January 2025) Mr. John Norum Job No. 23-14403 KMJ Real Estate 2888 Locker Avenue East, Suite 200 Carlsbad, CA 92010 Subject: Civil Grading Plan Review Tyler Street Homes 3215-3225 Tyler Street Carlsbad California Dear Mr. Norum: As requested by Eric Asari with Pasco Laret and Suiter (PLSA), we have reviewed the latest civil plans (undated) for the subject project, and prepared by PLSA showing details for the driveway and pedestrian, and walkways to be constructed with pavers, and other details for runoff water infiltration and site drainage. The undated reviewed plans include seven sheets (SH-1 through SH-7) have been reviewed from a geotechnical engineering viewpoint to verify adequate conformance with our geotechnical recommendations presented in our preliminary geotechnical report for the project dated January 29, 2024, as well as comments made via emails with the same objective. Furthermore, and as requested, we are including with this letter Appendix A that presents Form D as an attachment of the Infiltration Testing, performed at the subject site as described in our report Infiltration Feasibility Conditions, dated January 29, 2024. We understand that in the alley area, concrete pavers are required, and the pavement cross- section shown in the plans has been recommended by our firm. Based on methodology by ASCE and the Structural Design of Interlocking Concrete Pavement for Municipal Street and Roads, by ICPI, and using a conservatively estimated R-value of 25 and traffic index of 5, we recommend the following: For the vehicular paver pavement, the cross section should consist of at least 3-1/8 thick concrete pavers; on 1.0 inch minimum of sand bedding type ASTM No.8; on 6 inches of crushed rock gravel type ASTM No.57; on 4 inches of ASTM gravel No.2 (ASTM C-33), on properly compacted 12 inches of subgrade soils. For the pedestrian paver pavement, the cross section should consist of at least 2-3/8 thick concrete pavers; on 1.0 inch minimum of sand bedding type ASTM No.8; on 6 inches of crushed rock gravel type ASTM No.57; on 2 inches of ASTM gravel No.2 (ASTM C-33), on properly compacted 12 inches of subgrade soils. 4~~-Geotechnical Exploration, Inc. SOIL AND FOUNDATION ENGINEERING • GROUNDWATER • ENGINEERING GEOLOGY 7420 TRADE STREET• SAN DIEGO, CA. 92121 • (858) 549-7222 • FAX: (858) 549-1604 • EMAIL: geotech@gei-sd.com Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 2 The gravel base and subbase layer and subgrade soils for both vehicular and pedestrian cross sections shall be compacted to at least 95 percent relative compaction. The sand bedding material shall be vibrated with the paver blocks after these are set on the bedding sand. Sand type ASTM 8 shall also fill the voids between the blocks. Concrete curbs shall be installed to prevent lateral movement of the concrete pavers. A copy of our preliminary geotechnical report and this letter should be provided to all pertinent contractors involved with the soil preparation and foundation construction. Any grading should be performed per the city approved plans and grading ordinance, and per the recommendations presented in our geotechnical report. Should you have any questions, please feel free to call our office. Reference to our Job No. 23-14403 will expedite a response to your inquiries. Respectfully submitted, GEOTECHNICAL EXPLORATION, INC. ______________________________ _____________________________ Jaime A. Cerros, P.E. Richard A. Cerros, P.E. R.C.E. 34422/G.E. 2007 R.C.E. 94223 Senior Geotechnical Engineer APPENDIX A Infiltration Forms for Pavers, Planters, and Tree Wells. Appendix D: Geotechnical Engineer Analysis D-1 Jan. 2024 Appendix D Geotechnical Engineer Analysis Analysis of Infiltration Restrictions This section is only applicable if the analysis of infiltration restrictions is performed by a licensed engineer practicing in geotechnical engineering. The SWQMP Preparer and Geotechnical Engineer must work collaboratively to identify any infiltration restrictions identified in Table D.1-1 below. Upon completion of this section, the Geotechnical Engineer must characterize each DMA as Restricted or Unrestricted for infiltration and provide adequate support/discussion in the geotechnical report. A DMA is considered restricted when one or more restrictions exist which cannot be reasonably resolved through site design changes. Table D.1-1: Considerations for Geotechnical Analysis of Infiltration Restrictions Restriction Element Is Element Applicable? (Yes/No) Mandatory Considerations BMP is within 100’ of Contaminated Soils BMP is within 100’ of Industrial Activities Lacking Source Control BMP is within 100’ of Well/Groundwater Basin BMP is within 50’ of Septic Tanks/Leach Fields BMP is within 10’ of Structures/Tanks/Walls BMP is within 10’ of Sewer Utilities BMP is within 10’ of Groundwater Table BMP is within Hydric Soils BMP is within Highly Liquefiable Soils and has Connectivity to Structures %03LVZLWKLQ7LPHVWKH+HLJKWRI$GMDFHQW6WHHS6ORSHV County Staff has Assigned “Restricted” Infiltration Category Optional Considerations BMP is within Predominantly Type D Soil BMP is within 10’ of Property Line %03LVZLWKLQ)LOO'HSWKVRI· ([LVWLQJRU3URSRVHG BMP is within 10’ of Underground Utilities BMP is within 250’ of Ephemeral Stream Other (Provide detailed geotechnical support) Result Based on examination of the best available information, I have not identified any restrictions above. Unrestricted Based on examination of the best available information, I have identified one or more restrictions above. Restricted Table D.1-1 is divided into Mandatory Considerations and Optional Considerations. Mandatory 23-14403 Tyler Street Homes Pavers NO NO NO NO NO NO NO NO NO NO NO NO NO NO NO NO NO X D.1 Appendix D: Geotechnical Engineer Analysis D-2 Jan. 2024 Considerations include elements that may pose a significant risk to human health and safety and must always be evaluated. Optional Considerations include elements that are not necessarily associated with human health and safety, so analysis is not mandated through this guidance document. All elements presented in this table are subject to the discretion of the Geotechnical Engineer if adequate supporting information is provided. Applicants must evaluate infiltration restrictions through use of the best available data. A list of resources available for evaluation is provided in Section B.2 Determination of Design Infiltration Rates This section is only applicable if the determination of design infiltration rates is performed by a licensed engineer practicing in geotechnical engineering. The guidance in this section identifies methods for identifying observed infiltration rates, corrected infiltration rates, safety factors, and design infiltration rates for use in structural BMP design. Upon completion of this section, the Geotechnical Engineer must recommend a design infiltration rate for each DMA and provide adequate support/discussion in the geotechnical report. Table D.2-1: Elements for Determination of Design Infiltration Rates Item Value Unit Initial Infiltration Rate Identify per Section D.2.1 in/hr Corrected Infiltration Rate Identify per Section D.2.2 in/hr Safety Factor Identify per Section D.2.3 unitless Design Infiltration Rate Corrected Infiltration Rate ÷ Safety Factor in/hr 23-14403 Tyler Street Homes Pavers 2 0.367 0.357 0.1875 D.2 Appendix D: Geotechnical Engineer Analysis D-1 Jan. 2024 Appendix D Geotechnical Engineer Analysis Analysis of Infiltration Restrictions This section is only applicable if the analysis of infiltration restrictions is performed by a licensed engineer practicing in geotechnical engineering. The SWQMP Preparer and Geotechnical Engineer must work collaboratively to identify any infiltration restrictions identified in Table D.1-1 below. Upon completion of this section, the Geotechnical Engineer must characterize each DMA as Restricted or Unrestricted for infiltration and provide adequate support/discussion in the geotechnical report. A DMA is considered restricted when one or more restrictions exist which cannot be reasonably resolved through site design changes. Table D.1-1: Considerations for Geotechnical Analysis of Infiltration Restrictions Restriction Element Is Element Applicable? (Yes/No) Mandatory Considerations BMP is within 100’ of Contaminated Soils BMP is within 100’ of Industrial Activities Lacking Source Control BMP is within 100’ of Well/Groundwater Basin BMP is within 50’ of Septic Tanks/Leach Fields BMP is within 10’ of Structures/Tanks/Walls BMP is within 10’ of Sewer Utilities BMP is within 10’ of Groundwater Table BMP is within Hydric Soils BMP is within Highly Liquefiable Soils and has Connectivity to Structures %03LVZLWKLQ7LPHVWKH+HLJKWRI$GMDFHQW6WHHS6ORSHV County Staff has Assigned “Restricted” Infiltration Category Optional Considerations BMP is within Predominantly Type D Soil BMP is within 10’ of Property Line %03LVZLWKLQ)LOO'HSWKVRI· ([LVWLQJRU3URSRVHG BMP is within 10’ of Underground Utilities BMP is within 250’ of Ephemeral Stream Other (Provide detailed geotechnical support) Result Based on examination of the best available information, I have not identified any restrictions above. Unrestricted Based on examination of the best available information, I have identified one or more restrictions above. Restricted Table D.1-1 is divided into Mandatory Considerations and Optional Considerations. Mandatory 23-14403 Tyler Street Homes Planters NO NO NO NO NO NO NO NO NO NO NO NO NO NO NO NO NO X D.1 Appendix D: Geotechnical Engineer Analysis D-2 Jan. 2024 Considerations include elements that may pose a significant risk to human health and safety and must always be evaluated. Optional Considerations include elements that are not necessarily associated with human health and safety, so analysis is not mandated through this guidance document. All elements presented in this table are subject to the discretion of the Geotechnical Engineer if adequate supporting information is provided. Applicants must evaluate infiltration restrictions through use of the best available data. A list of resources available for evaluation is provided in Section B.2 Determination of Design Infiltration Rates This section is only applicable if the determination of design infiltration rates is performed by a licensed engineer practicing in geotechnical engineering. The guidance in this section identifies methods for identifying observed infiltration rates, corrected infiltration rates, safety factors, and design infiltration rates for use in structural BMP design. Upon completion of this section, the Geotechnical Engineer must recommend a design infiltration rate for each DMA and provide adequate support/discussion in the geotechnical report. Table D.2-1: Elements for Determination of Design Infiltration Rates Item Value Unit Initial Infiltration Rate Identify per Section D.2.1 in/hr Corrected Infiltration Rate Identify per Section D.2.2 in/hr Safety Factor Identify per Section D.2.3 unitless Design Infiltration Rate Corrected Infiltration Rate ÷ Safety Factor in/hr 23-14403 Tyler Street Homes Planters 2 0.367 0.357 0.1875 D.2 Appendix D: Geotechnical Engineer Analysis D-1 Jan. 2024 Appendix D Geotechnical Engineer Analysis Analysis of Infiltration Restrictions This section is only applicable if the analysis of infiltration restrictions is performed by a licensed engineer practicing in geotechnical engineering. The SWQMP Preparer and Geotechnical Engineer must work collaboratively to identify any infiltration restrictions identified in Table D.1-1 below. Upon completion of this section, the Geotechnical Engineer must characterize each DMA as Restricted or Unrestricted for infiltration and provide adequate support/discussion in the geotechnical report. A DMA is considered restricted when one or more restrictions exist which cannot be reasonably resolved through site design changes. Table D.1-1: Considerations for Geotechnical Analysis of Infiltration Restrictions Restriction Element Is Element Applicable? (Yes/No) Mandatory Considerations BMP is within 100’ of Contaminated Soils BMP is within 100’ of Industrial Activities Lacking Source Control BMP is within 100’ of Well/Groundwater Basin BMP is within 50’ of Septic Tanks/Leach Fields BMP is within 10’ of Structures/Tanks/Walls BMP is within 10’ of Sewer Utilities BMP is within 10’ of Groundwater Table BMP is within Hydric Soils BMP is within Highly Liquefiable Soils and has Connectivity to Structures %03LVZLWKLQ7LPHVWKH+HLJKWRI$GMDFHQW6WHHS6ORSHV County Staff has Assigned “Restricted” Infiltration Category Optional Considerations BMP is within Predominantly Type D Soil BMP is within 10’ of Property Line %03LVZLWKLQ)LOO'HSWKVRI· ([LVWLQJRU3URSRVHG BMP is within 10’ of Underground Utilities BMP is within 250’ of Ephemeral Stream Other (Provide detailed geotechnical support) Result Based on examination of the best available information, I have not identified any restrictions above. Unrestricted Based on examination of the best available information, I have identified one or more restrictions above. Restricted Table D.1-1 is divided into Mandatory Considerations and Optional Considerations. Mandatory 23-14403 Tyler Street Homes Tree Well NO NO NO NO NO NO NO NO NO NO NO NO NO NO NO NO NO X D.1 Appendix D: Geotechnical Engineer Analysis D-2 Jan. 2024 Considerations include elements that may pose a significant risk to human health and safety and must always be evaluated. Optional Considerations include elements that are not necessarily associated with human health and safety, so analysis is not mandated through this guidance document. All elements presented in this table are subject to the discretion of the Geotechnical Engineer if adequate supporting information is provided. Applicants must evaluate infiltration restrictions through use of the best available data. A list of resources available for evaluation is provided in Section B.2 Determination of Design Infiltration Rates This section is only applicable if the determination of design infiltration rates is performed by a licensed engineer practicing in geotechnical engineering. The guidance in this section identifies methods for identifying observed infiltration rates, corrected infiltration rates, safety factors, and design infiltration rates for use in structural BMP design. Upon completion of this section, the Geotechnical Engineer must recommend a design infiltration rate for each DMA and provide adequate support/discussion in the geotechnical report. Table D.2-1: Elements for Determination of Design Infiltration Rates Item Value Unit Initial Infiltration Rate Identify per Section D.2.1 in/hr Corrected Infiltration Rate Identify per Section D.2.2 in/hr Safety Factor Identify per Section D.2.3 unitless Design Infiltration Rate Corrected Infiltration Rate ÷ Safety Factor in/hr 23-14403 Tyler Street Homes Tree Well 2 0.367 0.357 0.1875 D.2 Response to City of Carlsbad Land Development Engineering Review Project ID: CT 2024-0001 First Review 111 23 January 2025 Mr. John Norum Job No. 23-14403 KMJ Real Estate 2888 Locker Avenue East, Suite 200 Carlsbad, CA 92010 Subject: Response to City of Carlsbad LDE First Review: CT2024-0001 Tyler Street Homes 3215-3225 Tyler Street Carlsbad California Dear Mr. Norum: As requested by Mr. Eric Asari with Pasco Laret Suiter & Associates, your project civil engineer, and as required by the City of Carlsbad reviewer, we are issuing this response letter for the geotechnical comments to our “Geotechnical Investigation Report of Preliminary Geotechnical Investigation” dated January 29, 2024. The geotechnical reviewer’s document is dated November 20, 2024. GEOTECHNICAL COMMENTS 1. Please review the most current grading plan for the project and provide any additional geotechnical recommendations or modifications to the geotechnical report if necessary. GEI Response: We have reviewed the latest, undated grading plan by Pasco Laret Suiter (PLSA) and we have provided additional recommendations in regards to the vehicular and pedestrian pavers in our grading plan review letter with a revised date of January 22, 2025. 2. Please provide an updated “Site Specific Geologic Map” utilizing the most current revision of the grading plan for the project as the base map and at a sufficiently large scale to clearly show (at a minimum): a) existing site topography and improvements, b) proposed structures and improvements, c) proposed finished grades, d) geologic units, and e) the locations of subsurface exploration. 4~~-Geotechnical Exploration, Inc. SOIL AND FOUNDATION ENGINEERING • GROUNDWATER • ENGINEERING GEOLOGY 7420 TRADE STREET• SAN DIEGO, CA. 92121 • (858) 549-7222 • FAX: (858) 549-1604 • EMAIL: geotech@gei-sd.com Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 2 GEI Response: As requested, we are including a copy of the revised site specific geologic/ geotechnical map based on the latest grading plan, which includes the existing site topography and improvements, proposed structures and improvements, proposed finished grades, geologic units, and the locations of subsurface exploratory pits and infiltration test borings performed by our firm. Included as Appendix E in the Final Geotechnical Investigation Report. 3. Strength (direct shear) testing of the on-site soils is not provided in the report. Please provide the appropriate laboratory testing to substantiate the values for bearing capacity, passive pressure, coefficient of friction, and active pressure that are presented in the report. If presumptive values are being recommended by the consultant, please state the reference and use values consistent with the appropriate soil type in Table 1806.2 and 1610.1 of the 2019 California Building Code (please justify the soil type by laboratory testing if something other than soils class 5 in Table 1806). GEI Response: Based on our experience and a chart provided by NAVFAC Manual, Figure 7, page 7.1-149 and also in Table 3.5 of page 80 of Geotechnical Engineering Techniques and Practices, by Roy Hunt, we assigned a conservative value of 32 degrees and a cohesion value of 50 psf for properly compacted on-site silty sands or similar imported soils. We also used a soil total unit weight of 120 pcf to calculate the ultimate and the allowable soil bearing capacity for footings embedded at least 24 inches in depth with a minimum width of 15 inches for a 3-story building. The ultimate soils bearing capacity was calculated based on the bearing capacity factors by Meyerhoff as presented in Foundations Analysis and Design, by Joseph E. Bowles, 5th Edition, page 223. The calculated ultimate bearing capacity was 8,991 psf. When the factor of safety of 3 is included, the adjusted allowable bearing capacity is 2,997 psf. Our report recommended an allowable soil bearing capacity of 3,000 psf for an acceptable allowable settlement. To calculate the allowable soil passive resistance, we used a factor of safety of 1.5 applied to the calculated ultimate passive resistance. The passive resistance was calculated from the following equation: 𝑃 =𝛾′ℎ𝑡𝑎𝑛2 ቆ45+𝜑′ 2 ቇ +2𝑐tan ቆ45° + 𝜑′ 2 ቇ ,m Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 3 Where γ’ is the effective soil unit weight in pcf, h is the depth of the footing in feet (we used 1 foot rather than 2 feet for calculation purposes), and φ’ is the soil friction angle in degrees. The calculated ultimate value was 570 pcf. With a factor of safety of 1.5, the allowable passive resistance was 380 pcf. We recommended 270 pcf in our report. Regarding the allowable friction coefficient, the ultimate value of the soils is tan φ’, which for 32 degrees is 0.62. After applying a factor of safety of 1.5, the allowable friction coefficient is 0.42. Our report recommended a value of 0.40. For soil active pressure calculation, we neglected the soil cohesion value and used the equation: 𝐾 =𝛾𝑡𝑎𝑛ଶ ቀ45 −ఝᇱ ଶ ቁ . We used a value of 120 pcf for the soil weight and a friction angle of 32 degrees. The result yielded a value of 36.87 pcf. Our report recommended a value of 38 pcf for level backfill. 4. Please justify the use of an active pressure of 38 pcf (see comment No. 6 above). GEI Response: If we use a friction angle of 32 degrees, based on the explanation presented above, and a soil unit weight of 120 pcf, 𝐾 = 120 .𝑡𝑎𝑛ଶ ቀ45 −ଷଶᇱ ଶ ቁ =36.87, which we rounded up to 38 pcf because the soil will be compacted backfill upon completion of the project. 5. The “Material for Fill” section of the report (page 21) locally indicates soils used as fill should have an expansion index below 50 (“Low”). However, other pages of the report indicate the on-site soils possess an expansion index of 0 (Very Low) per the laboratory testing (which the reviewer assumes was used for the foundation recommendations provided in the report). As soils with expansion index (EI) over 20 are considered expansive and require mitigation in accordance with Section 1803.5.3 and 1808.6 of the 2022 CBC, please revise as necessary the “Material for Fill” section of the report that present the allowable use of soils with an expansion index below 50 to provide requirements for soils to have an expansion index below 20. If soils with an expansion index of 50 are used, please provide that are being recommended to address expansive soils (for soils with an EI between 20 and 50), revise the foundation recommendations accordingly to satisfy Section 1808.6, and provide a statement that the foundation system for the proposed residential ,m Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 4 structures will meet the requirements of Section 1808.6 of the 2022 California Building Code. GEI Response: The following recommendations are for soils with an expansion index value of zero (obtained in our laboratory testing): Imported soils should be similar to the on-site soils and tested to verify the expansion index is below 20. For soils having an expansion index over 20, we recommend that foundations be at least 24 inches in depth and have a width of at least 15 inches wide. The slab on-grade should be at least 5 inches thick and have reinforcing of at least No. 4 bars 18 inches apart in both directions. These recommendations are based in the Technical Manual, Foundations in Expansive Soils, TM 5-818-7, Headquarters, Department of the Navy, page 6-2. The grade beams or continuous foundations should not exceed spacing of 20 feet apart. If desired, the structural engineer may use other acceptable structural design methods to satisfy the Section 1808.6 of the 2022 California Building Code for soils with expansion index values over 20. 6. Please clarify the recommendations (allowed vertical height, angle of inclination, etc.) for temporary cuts anticipated for this specific project for the proposed remedial grading and/or utility trenches. Please provide recommendations to prevent adverse impact to adjacent off-site property with respect to the temporary cuts along the property boundaries that will apparently be necessary for the recommended remedial grading and to promote worker safety for potentially deeper cuts for utility trenches. GEI Response : We do not anticipate any vertical cuts on the project site as the site is relatively flat. Basements are not proposed based on the finished pad grade information. If temporary cuts are necessary for utilities, we recommend a 3-foot vertical cut with a 1:1 (H:V) backcut in the upper portion. ABCD slot cutting should be used if there is a necessity to cut near property lines as not to undermined existing structures. The slots should have a width not exceeding 6 feet and 3-feet in depth. 7. Please provide geotechnical recommendations for the proposed permeable pavers for the driveway areas of the project. GEI Response: Recommendations for the proposed permeable pavers were provided in our plan review letter for the civil grading plans dated January 22, 2025. ,m Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 5 8. Please evaluate and discuss the potential for storm water infiltration at the subject site as part of the proposed project. GEI Response: We evaluated and discussed the potential for storm water infiltration at the subject site in our Infiltration Feasibility Condition letter dated January 29, 2024. 9. Please provide a summary list of the geotechnical observation and testing services that should be performed as part of the proposed development. GEI Response: During the construction phase of the project, we should observe and evaluate the excavation bottom bearing soils of removed fill soils and prior to the start of backfill placement in the excavated areas and any other areas to receive fill or backfill soils. We will collect soil samples of imported soils to be used for fill or existing backfill (if warranted) on the project site, in order to determine the expansion index, maximum dry density and optimum moisture of the sampled soils being placed as fill material. Materials with an expansion index over 50 will not be accepted to be imported to the site. We will verify the compaction adequacy and moisture content of subgrade soils that will receive pavement or flatwork improvements. Backfill soil will be placed in lifts not exceeding 8-inches and tested every 2 feet in vertical thickness. Soil samples will be collected to perform R-Value tests, if requested, in areas that will receive pavement. Adequacy of compaction of asphalt concrete can be verified provided a Hveem value by the asphalt concrete manufacturer. We will observe the bearing soils in foundation excavation bottoms prior to the placement of wood forms, steel reinforcement, and concrete. If requested, we will perform laboratory soil shear tests. Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 6 Should you have any questions, please feel free to call our office. Reference to our Job No. 23-14403 will expedite a response to your inquiries. Respectfully submitted, GEOTECHNICAL EXPLORATION, INC. ______________________________ ___________________________ Jaime A. Cerros, P.E. Richard A. Cerros, P.E. R.C.E. 34422/G.E. 2007 R.C.E. 94223 Senior Geotechnical Engineer chard A. Cerros, P. E. r F q47:n Response to City of Carlsbad Land Development Engineering Review Project ID: CT 2024-0001 Second Review 111 06 March 2025 Mr. John Norum Job No. 23-14403 KMJ Real Estate 2888 Locker Avenue East, Suite 200 Carlsbad, CA 92010 Subject: Response to City of Carlsbad LDE Second Review: CT2024-0001 Tyler Street Homes 3215-3225 Tyler Street Carlsbad California Dear Mr. Norum: As requested by Mr. Eric Asari with Pasco Laret Suiter & Associates, your project civil engineer, and as required by the City of Carlsbad reviewer, we are issuing this response letter regarding City geotechnical comments to our “Final Geotechnical Investigation Report” with a revised date of January 23, 2025. The geotechnical reviewer’s document is dated February 05, 2025. 1. Strength (direct shear) testing of the on-site soils is not provided in the reviewed report. Please provide the appropriate laboratory testing to substantiate the values for bearing capacity, passive pressure, coefficient of friction, and active pressure that are presented in the report. If presumptive values are being recommended by the consultant, please indicate the soil class and use values consistent with the appropriate soil type (Class) in Tables 1806.2 and 1610.1 of the 2022 California Building Code. If soil parameters other than soil class 5 in Tables 1806.2 and 1610.1 are provided, please provide site specific laboratory test results to justify the parameters or use of assumed values of C and φ for calculation of parameters above. (Repeat comment-justification of the geotechnical parameters for foundation design is required at a minimum should be consistent with California Building Code requirements. The results of strength testing (direct shear or any other provided in the “Response to City of Carlsbad.” report. In accordance with Sections 1803.5.2, and 1806.2 of the 2022 California Building Code; if the load bearing values provided in the geotechnical report are superior to those specified in the code (Table 4~~-Geotechnical Exploration, Inc. SOIL AND FOUNDATION ENGINEERING • GROUNDWATER • ENGINEERING GEOLOGY 7420 TRADE STREET• SAN DIEGO, CA. 92121 • (858) 549-7222 • FAX: (858) 549-1604 • EMAIL: geotech@gei-sd.com Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 2 1806.2) then data shall be provided with to substantiate the higher values. With the response provided by the geotechnical consultant in the “Response to City of Carlsbad…: report in mind which references the NAVFAC manual and other engineering textbooks for the derivation of the C and φ parameters used to develop the foundation recommendations for the proposed development, please provide the laboratory testing of the on-site soils that justifies the assumed values of (C=50) and φ =32 and provide copies of the specific tables/charts from NAVFAC and the calculations reportedly used to determine the values of bearing capacity, passive pressure, friction, and active pressure provide in the geotechnical report for design of the project. GEI Response: We have recently performed two direct remolded shear tests on soil samples taken at the project site. The soil samples were remolded to 90% of maximum dry density. The shear tests were performed under unsaturated and saturated conditions. In our first response, we originally assumed the unit weight and friction angles based on the following charts provided by NAVFAC Manual, Figure 7, page 7.1-149 and also in Table 3.5 of page 80 of Geotechnical Engineering Techniques and Practices, by Roy Hunt, respectively. 45 ANGLE OF INTERNAL FRICTION VS DENSITY (FOR COAIISE GR.AJNED SOILS) ;;; 40 ~ ~ '9- z 35 0 ~ 0: .. .J. ,0 ' 08TAINED FllOM z EFFECTIVE STRESs " "' F.llUJRE ENVELOl'ES ... ,!; APPRO~IIIIIATE OORR£UTKlH ... IS FOR COH~LESS 0 .., 25 MATEIMLS WITIIOUT ... i PLASTIC FINES • 20 .......... ___ ....._ ___ ._ __ ___. ___ ....._ ___ ..._ __ ___. ___ _, 75 80 90 100 110 120 130 140 l!IO . DRY UNIT W£1GHT (yDl, PCF 1.2 I.I LO 0.9 Q9W, 0.706606 QM Q5 o,e 0,4 o.35 o., 02:I 0.2 0.15 VOID RATIO,t 0.55 0.5 0.4 0.35 0.3 0.2 0.15 POROSITY,n (G<2.68) FIGURE 7 Cor relations of Su ength Characteris tics for Granular Soils Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 3 In our first response prior to our direct shear test results, we conservatively assigned a value of 32 degrees and a cohesion value of 50 psf for medium dense, properly compacted on-site silty sands or similar imported soils. We also used a soil total unit weight of 120 pcf to calculate the ultimate and allowable soil bearing capacity for footings embedded at least 24 inches in depth with a minimum width of 15 inches for a 3-story building. The ultimate soils bearing capacity was calculated based on the bearing capacity factors by Meyerhoff as presented in Foundations Analysis and Design, by Joseph E. Bowles, 5th Edition, page 223. The previously calculated ultimate bearing capacity was 8,991 psf. When the factor of safety of 3 is included, the adjusted allowable bearing capacity is 2,997 psf. After recent soil shear test results were obtained, we also calculated the bearing capacity using the Vesic soil bearing capacity formula, using both saturated and unsaturated shear strength values, which yielded a higher allowable bearing capacity. Refer to the appended spreadsheet calculations. Our geotechnical report recommended an allowable soil bearing capacity of 3,000 psf for an acceptable allowable settlement. TABLE 3.5 COMMON l'ROPERTIES OF COHESIONLESS S011.S" i Mt1ori1I dry.I Compaclncu D1t,'l• N' g/cm1 CW:well-grnded Dense 75 90 2.21 gravels. gravel-Medium dense 50 55 2.08 sand mixtures Loose 25 <28 1.97 GP: poorly graded Dense 75 10 2.04 gravels. grovel-Medium dense so so 1.92 sand mixtures Loose 25 <20 1.83 SW: well-graded sands. Dense 75 65 1.89 gravelly sands Medium dense so 35 1.79 Loose 25 <IS 1,70 SP: poorly graded Dense 75 so 1.16 sands. gravelly Medium dense so 30 1.67 sands Loose 25 <10 I.S9 SM: silly sands Dense 7S 4S 1.65 Medium dense so 2S 1.5S Loose 2S <8 1.49 ML: inorganic sills, very Dense 7S 3S 1.49 fine sands Medium dense so 20 1.41 Loose 2S <4 1.35 ·N is blows per fool of penclr>lion In lhc SPT. Adjustmonls for gredolion ore ofter Burmlslcr (19621," S.c Tobie 6., for general relolionships of o. vs. N. fOensily given ls for C, • 2.68 (quarlz groins} /Friction angle Q depends on mineral lype, normal stress, ond grain ongulnri1y ns well as D• and ~••1!01ion (sec fig. 3.29). "'From Hunl (1984}1 Reprinted with permission ofMcGraw,11111 Book Company. Vold ntlo Stn:ngthl • C 0.22 40 0.28 36 0.36 32 0.33 38 0.39 35 0.47 32 0.43 37 0.49 34 0,57 30 0.52 36 0.60 33 0.65 29 0.62 35 0.74 32 0.80 29 0.80 33 0.90 31 1.0 27 131 Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 4 To calculate the allowable soil passive resistance, we used a factor of safety of 1.5 applied to the calculated ultimate passive resistance. The passive resistance was calculated from the following equation: 𝑃 =𝛾′ℎ𝑡𝑎𝑛2 ቆ45+𝜑′ 2 ቇ +2𝑐tan ቆ45° + 𝜑′ 2 ቇ Where γ’ is the effective soil unit weight in pcf, h is the depth of the footing in feet (we used 1 foot rather than 2 feet for calculation purposes), and φ’ is the soil friction angle in degrees. The calculated ultimate value was 570 pcf. With a factor of safety of 1.5, the allowable passive resistance was 380 pcf. We recommended 270 pcf in our report. Regarding the allowable friction coefficient, the ultimate value of the soils is tan φ’, which for 32 degrees is 0.62. After applying a factor of safety of 1.5, the allowable friction coefficient is 0.42. Our report recommended a value of 0.40. For soil active pressure calculation, we neglected the soil cohesion value and used the equation: 𝐾 =𝛾𝑡𝑎𝑛ଶ ቀ45 −ఝᇱ ଶ ቁ . We used a value of 120 pcf for the soil weight and a friction angle of 32 degrees. The result yielded a value of 36.87 pcf. Our report recommended a value of 38 pcf for level backfill. 2. Please justify the use of an active pressure of 38 pcf (level) and 56 pcf (at- rest) that are provided for retaining walls (see comment #1). (repeat comment-see comment #1 above.) GEI Response: Based on our recent laboratory direct shear results which yielded friction angles of 31 and 34 degrees. We previously used a friction angle of 32 degrees as the average from our shear results and a soil unit weight of 120 pcf to calculate the active pressure for level backfill 𝐾 = 120 .𝑡𝑎𝑛ଶ ቀ45 −ଷଶᇱ ଶ ቁ =36.87 𝑝𝑐𝑓, which we conservatively rounded up to 38 pcf for level backfill. For the at rest pressure, we use 𝐾 = 120 × ሺ1 −sin32°ሻ which gives us 56 pcf. 3. The “Material for Fill” section of the report (page 21) locally indicates soils used as fill should have an expansion index below 50 (“Low”). However, other pages of the report indicate the on-site soils possess an expansion index of 0 (Very Low) per the laboratory testing (which the reviewer assumes was used for the foundation recommendations provided in the report). As soils with expansion index (EI) over 20 are considered expansive and require mitigation in accordance with Section 1803.5.3 and 1808.6 of the 2022 CBC, please revise as necessary the “Material for Fill” section of the report that present the ,m Tyler Street Homes Job No. 23-14403 Carlsbad, California Page 5 allowable use of soils with an expansion index below 50 to provide requirements for soils to have an expansion index below 20. If soils with an expansion index of 50 are used, please provide that are being recommended to address expansive soils (for soils with an EI between 20 and 50), revise the foundation recommendations accordingly to satisfy Section 1808.6, and provide a statement that the foundation system for the proposed residential structures will meet the requirements of Section 1808.6 of the 2022 California Building Code. (Repeat Comment- the “Material for Fill” and Retaining Wall Design Criteria” sections of the recently provided “Final Geotechnical Investigation Report, Tyler Street Homes” report still provides recommendations based on soils with an Expansion Index (E.I.) less than 50. As previously requested, if soils with an Expansion Index between 20 to 50 are considered acceptable for use as appears to be indicated in the response to this comment in the “Response to City Review…” and “Material for Fill” and Retaining Wall Design Criteria: sections for the recently provided “Final Geotechnical Investigation Report, Tyler Street Homes…” report, please provide the parameters (Effectively Plasticity Index, etc.) as necessary for the specific method of Section 1808.6 (1808.6.1 through 1808.6.4) that GEI is recommending to satisfy the requirement for expansive soils and Section 1808.6.2 for slab-on-ground floor design. GEI Response: We have removed reference to low expansive soils with an expansion index (E.I.) between 20 and 50. The existing on-site soils have an expansion index (E.I.) of 0, which based on ASTM D-4829, is considered very low expansive. Any imported fills, if used, should consist of an E.I less than 20 and be tested for expansivity by our firm prior to use as backfill. No additional recommendations are required for the structural design of the footings and slabs on-grade. Should you have any questions, please feel free to call our office. Reference to our Job No. 23-14403 will expedite a response to your inquiries. Respectfully submitted, GEOTECHNICAL EXPLORATION, INC. ______________________________ ___________________________ Jaime A. Cerros, P.E. Richard A. Cerros, P.E. R.C.E. 34422/G.E. 2007 R.C.E. 94223 Senior Geotechnical Engineer Inputs Foot Width. B=1.25 ft Foot Length. L=1 ft Foot Depth. D 2ft Soil Friction φ=31 ° Base Inclin.α=0 °Cohesion c=173 psf Slope Inclin.i=0 °Eccentricity e=0 ft i=0 rads 3 Nc 32.67 Nq 20.63 Nϒ 25.99 Inputs sc 1.466 See Factor c 173 psf q 115.2 psf gϒ 1.000 bc 1.000 See Factor Nc 32.67 Nq 20.63 B 1.250 ic 1.000 See Factor ϒ 57.6 pcf bq 1.000 Nϒ 25.99 gc 1.000 See Factor D 2 ft iq 1.000 bϒ 1.000 sq 1.450 See Factor gq 1.000 iϒ 0.612 sϒ 0.733 See Factor 12417.56 psf 4139.19 psf ultimate 8286 + 1723.02 xD + 336.00 xW allowable 2761.90 + 574.34 xD + 112.00 xW Final Inputs AllowableUltimate Soil Unit Weight ϒ 57.6 pcf Factor of Safety 𝑞 =𝑐𝑁𝑠𝑏𝑖𝑔 +𝑞𝑁𝑠𝑏𝑖𝑔 +0.5𝛾𝐵𝑁ఊ𝑠ఊ𝑏ఊ𝑖ఊ𝑔ఊ 𝑞 =𝑐𝑁𝑠𝑏𝑖𝑔 +𝑞𝑁𝑠𝑏𝑖𝑔 +0.5𝛾𝐵𝑁ఊ𝑠ఊ𝑏ఊ𝑖ఊ𝑔ఊ These depend on what is calculated above. FOLLOW ARROW for to input appropriate factors This bearing capacity is based on the saturated shear strength parameters. Vesic Method 11 1 1 1 1 1 1 -- Inputs Foot Width. B=1.25 ft Foot Length. L=1 ft Foot Depth. D 2ft Soil Friction φ=34 ° Base Inclin.α=0 °Cohesion c=200 psf Slope Inclin.i=0 °Eccentricity e=0 ft i=0 rads 3 Nc 42.16 Nq 29.44 Nϒ 41.06 Inputs sc 1.466 See Factor c 200 psf q 134 psf gϒ 1.000 bc 1.000 See Factor Nc 42.16 Nq 29.44 B 1.250 ic 1.000 See Factor ϒ 67 pcf bq 1.000 Nϒ 41.06 gc 1.000 See Factor D 2 ft iq 1.000 bϒ 1.000 sq 1.450 See Factor gq 1.000 iϒ 0.620 sϒ 0.733 See Factor 19341.82 psf 6447.27 psf ultimate 12361 + 2860.10 xD + 625.31 xW allowable 4120.44 + 953.37 xD + 208.44 xW Final Inputs AllowableUltimate Soil Unit Weight ϒ 67 pcf Factor of Safety 𝑞 =𝑐𝑁𝑠𝑏𝑖𝑔 +𝑞𝑁𝑠𝑏𝑖𝑔 +0.5𝛾𝐵𝑁ఊ𝑠ఊ𝑏ఊ𝑖ఊ𝑔ఊ 𝑞 =𝑐𝑁𝑠𝑏𝑖𝑔 +𝑞𝑁𝑠𝑏𝑖𝑔 +0.5𝛾𝐵𝑁ఊ𝑠ఊ𝑏ఊ𝑖ఊ𝑔ఊ These depend on what is calculated above. FOLLOW ARROW for to input appropriate factors This is based on the unsaturated direct shear test result. Vesic Method 11 1 1 1 1 1 1 --