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HomeMy WebLinkAboutPD 2022-0024; 2780 JAMES DRIVE; GEOTECHNICAL EVALUATION; 2022-06-06GEOTECHNICAL EVALUATION PROPOSED SINGLE-FAMILY RESIDENTIAL DEVELOPMENT 2780 JAMES DRIVE, CARLSBAD SAN DIEGO COUNTY, CALIFORNIA 92008 ASSESSOR’S PARCEL NUMBER (APN) 156-142-51-00 FOR A.C. MATTOS, INC. 3276 HIGHLAND DRIVE CARLSBAD, CALIFORNIA 92008 W.O. 8320-A-SC JUNE 6, 2022 Geotechnical C Geologic C Coastal C Environmental 5741 Palmer Way C Carlsbad, California 92010 C (760) 438-3155 C FAX (760) 931-0915 C www.geosoilsinc.com June 6, 2022 W.O. 8320-A-SC A.C. Mattos, Inc. 3276 Highland Drive Carlsbad, California 92008 Attention:Ms. Ana Mattos Subject:Geotechnical Evaluation, Proposed Single-Family Residential Development, 2780 James Drive, Carlsbad, San Diego County, California 92008, Assessor’s Parcel Number (APN) 156-142-51-00 Dear Ms. Mattos: In accordance with your request and authorization, GeoSoils, Inc. (GSI) has performed a geotechnical evaluation of the subject property, relative to the proposed single-family residential development thereon. The purpose of our work was to study the onsite geotechnical conditions in order to develop preliminary recommendations related to earthwork and the design and construction of the proposed improvements. The scope of our services included: a review of the 2004 “Rough Grading Report” prepared by Coast Geotechnical ([CG], 2004 [see Appendix A]) for the site and surrounding Carlsbad Tract (CT) 98-16; site reconnaissance and subsurface exploration with five (5) test pits (Appendix B); evaluations of geologic/seismic hazards and site seismicity (Appendix C); laboratory testing of collected soil samples (Appendix D); geologic and engineering analyses; and the preparation of this summary report. Our study did not include an evaluation of the existing retaining wall near the northern property boundary. SITE CONDITIONS/PROPOSED DEVELOPMENT The subject property consists of Lot 5 of Carlsbad Tract (CT) 98-16. It is a quadrilateral-shaped parcel of land located near the northern terminus of James Drive (see Figure 1, Site Location Map). The physical address of the property is 2780 James Drive, Carlsbad, San Diego County, California 92008. The geographic coordinates of the approximate centroid of the site are 33.1698° North, -117.3377° West. The parcel is bounded by James Drive to the southwest and by developed residential properties to the remaining quadrants. Topographically, the subject property may be characterized as generally flat-lying to very gentle southwestern sloping, anthropogenically modified terrain. According to the 50-scale grading plan prepared by Land Space Engineering ([LSE], 2002), which accompanied CG W.O. SITE LOCATION MAP Figure 1 8320-A-SC Base Map: TOPO!® ©2003 National Geographic, U.S.G.S. San Luis Rey Quadrangle, California -- San Diego Co., 7.5 Minute, dated 1997, current, 1999. Base Map: Google Maps, Copyright 2022 Google, Map Data Copyright 2022 Google 0 1000 2000 3000 4000 This map is copyrighted by Google 2022. It is unlawful to copy or reproduce all or any part thereof, whether for personal use or resale, without permission. All rights reserved. NOT TO SCALE SITE SITE Buena Vista way Buena Vista way Las Flores Dr El m w o o d S t Hi g h l a n d D r GeoSoils, Inc. (2004), the property was brought to elevation 160.5 feet (U.S. Coast and Geodetic Survey datum) during the original rough grading. GSI did not perform a topographic survey of the site nor was a current topographic survey map provided for our review. However, Google Earth satellite imagery indicates a similar site elevation as the pad grade elevation shown on LSE (2002). In addition, we did not observe evidence that additional grading has occurred within the parcel since the conclusion of rough grading in 2003. Site drainage is accommodated by sheet-flow runoff directed toward the southwest where it discharges into James Drive. With the exception of a concrete masonry unit (CMU) retaining wall near the northwestern property boundary, the site is essentially vacant. The retaining wall is approximately 3¼ feet in height and retains up to approximately 2¾ feet of earth. Site vegetation consists of patches of grasses and weeds. Based on information you provided, GSI understands that the proposed development includes the construction of an approximately 3,400 square foot single-family residence with an associated accessory dwelling unit (ADU) and swimming pool. GSI anticipates that the project will also include a driveway and hardscape (i.e., walkways, patios, pool deck, etc.). We expect that the residence and ADU will be supported by shallow foundations with concrete slab-on-grade floors. GEOTECHNICAL BACKGROUND Based on our review of CG (2004), GSI understands that the subject property was graded in early 2003. CG indicated that remedial grading involved the removal of residual soil and weathered terrace deposits (terrace deposits are now referred to as “old paralic deposits” on the current regional geologic map [Kennedy and Tan, 2007]). Excavations of 2 to 3½ feet below the former existing grades were required to remove these earth materials. CG stated that the remedial excavations extended to within 2 feet of the property boundaries. CG reported that following remedial excavation, the onsite soils and minor imported sand were placed within the excavations in approximately 6-inch thick loose lifts, moisture conditioned to about optimum moisture content, and compacted with heavy earth-moving equipment until at least 90 percent relative compaction was attained. CG indicated that the thickness of compacted fill placed within the residential tract ranged between approximately 3½ and 4 feet. CG performed seven field density tests throughout the graded area with one (1) field density test within the subject parcel, approximately 2 feet above the bottom of the remedial grading excavation. The test result indicated that the fill was compacted to more than 90 percent relative compaction, where tested. CG (2004) concluded that the fill materials were properly compacted. In addition, they surmised that the soil parameters recommended for foundation and slab design in their “Preliminary Geotechnical Investigation” report remained valid. A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 3 GeoSoils, Inc. CG (2004) provided updated seismic design parameters conforming to the 1997 Uniform Building Code as well as recommendations for the proposed driveway pavement sections. For driveway pavements, CG recommended 3 inches of asphaltic concrete or 4 inches of concrete over 4 inches of compacted select base (Class 2), placed on 12 inches of compacted subgrade. CG recommended that the subgrade and base materials be compacted to a minimum of 95 percent relative compaction. CG also advised that the driveway pavement sections should be protected from water sources to reduce the potential for pavement failure. CG (2004) further recommended that all underground utility piping be embedded in clean sand to at least 1 foot above the top of pipe, with the sand bedding flooded in place. CG suggested that the overlying trench backfill consist of the onsite granular soils compacted to a minimum of 90 percent relative compaction. CG advised that underground utilities not be installed such that they pass below a 45 degree plane from the nearest bottom edge of an adjacent footing. They indicated that deepened footings, raising the utility invert elevations, or providing additional horizontal separation between footings and underground utilities could address this recommendation. CG (2004) recommended that positive site drainage be maintained at all times. They suggested that water be directed away from foundations and not be allowed to pond or seep into the ground, or migrate beneath concrete flatwork or pavement sections. RECENT FIELD EXPLORATION On April 11, 2022, a GSI representative visited the subject parcel and conducted subsurface exploration with five (5) test pits excavated with a John Deere 410 rubber-tire backhoe. The logs of the test pits are included in Appendix B. The approximate locations of the test pits are shown on Figure 2 (Test Pit Location Map), which uses Google Earth satellite imagery as a base. SITE GEOLOGIC CONDITIONS The geologic units encountered during our recent field investigation included localized undocumented artificial fill, compacted artificial fill placed under the purview of CG (2004), and Quaternary-age old paralic deposits. These earth material units are further described below from the youngest to the oldest. The general distribution of these earth materials across the property are shown on Figure 2. Artificial Fill - Undocumented (Map Symbol - Afu) Based on our surficial observations, a relatively small, localized area of undocumented artificial fill may be present near the northeastern property corner. The fill was not explored A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 4 W.O.DATE:SCALE:8320-A-SC 05/22 1" = 20' Figure 2 TEST PIT LOCATION MAP BASE MAP FROM: GOOGLE EARTH, 2022 N ALL LOCATIONS ARE APPROXIMATE This document or efile is not a part of the Construction Documents and should not be relied upon as being an accurate depiction of design. TP-4 TP-5 TP-3 TP-1 TP-2 N.A.P. N.A.P.N.A.P. N.A.P. Qop Afc Qop Afc Afc Qop TP-5 N.A.P. GSI LEGEND Afu APPROXIMATE LOCATION OF EXISTING RETAINING WALL SUBDRAIN OUTLET Afc Qop Afu GeoSoils, Inc. but is anticipated to be a foot or less in thickness and likely consists of silty sand and clayey sand. Artificial Fill - Compacted (Map Symbol - Afc) Compacted artificial fill was encountered at the surface in all of the test pits. The fill generally extended to depths on the order of 4 to 5¼ feet below the existing grades. It typically consisted of variegated light brown, dark grayish brown, reddish yellow sand with trace silt; variegated light brown, dark grayish brown, reddish yellow, dark yellowish brown, and grayish brown silty sand; and brownish gray clayey sand. The fill locally contained trace clay and gravels, and metal, glass, and asphaltic concrete fragments. The compacted artificial fill was dry to wet and loose to dense. Observations indicate that the upper approximately 1 foot to 1¼ feet of the compacted artificial fill may have been imported to the site. The upper approximately 1 foot to 1¼ feet of the compacted artificial fill appeared weathered. Where weathered, the compacted artificial fill was dry and loose. Thus, the weathered compacted artificial fill is considered potentially compressible in its existing state and should not be relied upon for the support of the proposed improvements. The compacted artificial fill located below 1 foot to 1¼ feet from the existing grades is generally considered suitable bearing materials, based on the available data. Quaternary-age Old Paralic Deposits (Map Symbol - Qop) Quaternary-age old paralic deposits were encountered directly underlying the compacted artificial fill at approximate depths of 4 to 5½ feet below the existing grades. In general, the old paralic deposits consisted of reddish yellow, reddish brown, and brown very fine- to fine-grained clayey sand; brownish gray very fine- to fine-grained silty sand; and dark brown fine- to medium-grained silty sand. Trace to numerous iron-stone concretions were observed within the old paralic deposits. The old paralic deposits were typically moist to wet and dense. The old paralic deposits are considered suitable bearing materials. GEOLOGIC STRUCTURE Based on our observations and past work experience in the vicinity of the subject site, the old paralic deposits are typically thickly bedded. In general, the old paralic deposits are generally flat-lying or gently inclined in a western direction (i.e., toward the Pacific Ocean). No adverse geologic structures that would preclude project feasibility were observed by GSI or during our review of the regional geologic maps (Kennedy and Tan, 2007; Weber, 1982). A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 6 GeoSoils, Inc. GROUNDWATER Groundwater was not encountered within the test pits to the maximum explored depth (approximately 11 feet below the existing grades). GSI estimates that the regional groundwater table is generally coincident with sea level or approximately 160 feet below the lowest site elevation. Based on our understanding of the proposed development and the depth to the regional groundwater table, groundwater is not considered a significant geotechnical factor for the project. Our observations reflect site conditions at the time of our field investigation and do not preclude localized perched groundwater nor future changes in local groundwater conditions from climatic factors, excessive irrigation, above-normal precipitation, or other circumstances that were not obvious, at the time of our field exploration. Based on our observations and experience with similar sites, there is a potential for perched groundwater to occur along zones of contrasting permeabilities (i.e., fill lifts, fill/old paralic deposit contacts, etc.) and geologic discontinuities both during and following site development. This should be disclosed to all interested/affected parties. Should perched groundwater conditions manifest, this office could provide recommendations for mitigation upon request. Typical mitigation includes the installation of subdrain systems or cut-off barriers. GEOLOGIC HAZARDS EVALUATION General According to the “City of Carlsbad Geotechnical Hazard Analysis and Mapping Study” (Leighton and Associates, Inc. [L&A], 1992), the site is located within “Hazard Category” 53. This hazard category includes generally stable, relatively level mesas underlain by terrace deposits, sandstone, or granitic/metavolcanic bedrock. L&A (1992) indicates that sites within this hazard category are susceptible to erosion and ground shaking, and may contain formational sediments or bedrock that present challenges to excavation. Mass Wasting/Landslides Mass wasting refers to the various processes by which earth materials are moved down slope in response to the force of gravity. Examples of these processes include slope creep, surficial failures, and deep-seated landslides. Creep is the slowest form of mass wasting and generally involves the outer 5 to 10 feet of a slope surface. During heavy rains, such as those in El Niño years, creep-affected materials may become saturated, resulting in a more rapid form of downslope movement (i.e., landslides or surficial failures). According to regional landslide susceptibility mapping by Tan and Giffen (1995), the site is located within Relative Landslide Susceptibility Subarea 3-1, which is characterized as A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 7 GeoSoils, Inc. being “generally susceptible” to landsliding due to a combination of weak earth materials and steep slopes (slopes often have angles steeper than 15 degrees from the horizontal plane). Tan and Giffen (1995) indicate that although most slopes within Subarea 3-1 do not currently contain landslides, they are prone to failure, locally, when adversely modified. Our review of geologic mapping by Weber (1982), Tan and Giffen (1995), and Kennedy and Tan (2007) did not reveal the presence of landslides within the subject property. In addition, we did not observe evidence of landslides within the subject parcel during our field investigation. Moreover, geomorphic expressions indicative of past mass wasting events (i.e., scarps, hummocky terrain, debris cones, arcuate drainage patterns, etc.) were not identified during our review of stereoscopic aerial photographs (Park Aerial Surveys, Inc., 1953) nor during our field evaluation. The subject site generally consists of flat-lying to very gentle sloping terrain. It is not located near any significant ascending or descending slopes. Lastly, it is underlain in the near-surface by earth materials that typically exhibit high shear strengths. Based on the above, GSI concludes that the potential for the proposed development to be adversely affected by deep-seated slope instability is considered low. The onsite soils are, however, considered erodible. Properly designed and regularly maintained surface drainage is recommended to mitigate erosion. Faults Our review indicates that there are no known Holocene-active faults (i.e., faults that have ruptured in the last 11,700 years) crossing the subject property (Jennings and Bryant, 2010), and the site is not within an Alquist-Priolo earthquake fault zone (California Geological Survey [CGS], 2018). However, the site is situated in a region subject to periodic earthquakes along Holocene-active faults. According to Blake (2000a), the offshore segment of the Newport-Inglewood fault (part of the Newport-Inglewood - Rose Canyon fault zone) is the closest known Holecene-active fault to the site, located at a distance of approximately 5.7 miles (9.2 kilometers) to the southwest. This fault should have the greatest effect on the site in the form of strong ground shaking, should the design earthquake occur. Cao, et al. (2003) indicate the slip rate on the offshore segment of the Newport-Inglewood fault is 1.5 (±0.5) millimeters per year (mm/yr) and the fault is capable of a maximum magnitude 7.1 earthquake. The location of the offshore segment of the Newport-Inglewood fault and other major faults within 100 kilometers of the site are shown on the “California Fault Map” in Appendix C. The possibility of ground acceleration, or shaking at the site, may be considered as approximately similar to the southern California region as a whole. A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 8 GeoSoils, Inc. Surface Rupture Surface rupture is an offset of the ground surface when fault rupture propagates to the Earth’s surface. Owing to the lack of known Holocene-active or pre-Holocene faults crossing the site, the potential for the proposed development to be adversely affected by surface rupture from fault displacement is considered low. SEISMICITY The acceleration-attenuation relation of Bozorgnia, Campbell, and Niazi (1999) has been incorporated into EQFAULT (Blake, 2000a). EQFAULT is a computer program developed by Thomas F. Blake (2000a), which performs deterministic seismic hazard analyses using digitized California faults as earthquake sources. The program estimates the closest distance between each fault and a given site. If a fault is found to be within a user-selected radius, the program estimates peak horizontal ground acceleration that may occur at the site from an upper bound (formerly “maximum credible earthquake”), on that fault. Upper bound refers to the maximum expected ground acceleration produced from a given fault. Site acceleration (g) was computed by one user-selected acceleration-attenuation relation that is contained in EQFAULT. Based on the EQFAULT program, a peak horizontal ground acceleration from an upper bound event on the offshore segment of the Newport-Inglewood fault may be on the order of 0.57 g. The computer printouts of pertinent portions of the EQFAULT program are included within Appendix C. Historical site seismicity was evaluated with the acceleration-attenuation relation of Bozorgnia, Campbell, and Niazi (1999), and the computer program EQSEARCH (Blake, 2000b, updated to May 8, 2021). This program performs a search of the historical earthquake records for magnitude 5.0 to 9.0 seismic events within a 100-kilometer radius, between the years 1800 through May 8, 2021. Based on the selected acceleration-attenuation relationship, a peak horizontal ground acceleration is estimated, which may have affected the site during the specific time frame. Based on the available data and the attenuation relationship used, the estimated maximum (peak) site acceleration during the period 1800 through May 8, 2021 was about 0.23 g. A historic earthquake epicenter map and a seismic recurrence curve was also estimated/generated from the historical data. Computer printouts of the EQSEARCH program are presented in Appendix C. Seismic Shaking Parameters The following table summarizes the site-specific seismic design criteria obtained from the 2019 CBC, Chapter 16 Structural Design, Section 1613, Earthquake Loads (CBSC, 2019) and American Society of Civil Engineers (ASCE 7-16 [ASCE, 2017]). The A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 9 GeoSoils, Inc. computer program Seismic Design Maps, provided by the California Office of Statewide Health Planning and Development (OSHPD) and the Structural Engineers Association of California (SEAOC) has been used to aid in design (https://seismicmaps.org). The short spectral response uses a period of 0.2 seconds. Based on the findings from our onsite subsurface exploration and our experience with other similar sites, it is our opinion that Site Class “D” conditions are applicable to the proposed development. 2019 CBC SEISMIC DESIGN PARAMETERS PARAMETER SITE SPECIFIC VALUE PER ASCE 7-16 2019 CBC or REFERENCE Risk Category(1) I, II, or III Table 1604.5 Site Class D Section 1613.2.2/Chap. 20 ASCE 7-16 (p. 203-204) Spectral Response - (0.2 sec), Ss 0.872 g Section 1613.2.1 Figure 1613.2.1(1) Spectral Response - (1 sec), S1 0.670 g Section 1613.2.1 Figure 1613.2.1(2) Site Coefficient, Fa 1.086(2)Table 1613.2.3(1) Site Coefficient, Fv 2.5(3) (Section 21.3)Table 1613.2.3(2) Maximum Considered Earthquake Spectral Response Acceleration (0.2 sec), SMS 1.322 g(4) (Section 21.4) Section 1613.2.3 (Eqn 16-36) Maximum Considered Earthquake Spectral Response Acceleration (1 sec),SM1 1.092 g(5) (Section 21.4) Section 1613.2.3 (Eqn 16-37) 5% Damped Design Spectral Response Acceleration (0.2 sec), SDS 0.881 g(6)Section 1613.2.4 (Eqn 16-38) 5% Damped Design Spectral Response Acceleration (1 sec), SD1 0.728 g(7) (Section 21.4) Section 1613.2.4 (Eqn 16-39) PGAM - Probabilistic Vertical Ground Acceleration may be assumed as about 50% of these values. 0.56 g ASCE 7-16 (Eqn 11.8.1) Seismic Design Category D(8) (Section 11.6) Section 1613.2.5/ASCE 7-16 (p. 85: Table 11.6-1 or 11.6-2) 1. Risk Category to be confirmed by the Project Architect or Structural Engineer. 2. Per Table 11.4-1 of ASCE 7-16. 3. Per Section 21.3 of ASCE 7-16, if S1 > 0.2 then Fv is taken as 2.5. 4. Per Section 21.4 of ASCE 7-16, SMS = (1.5)(SDS) = (1.5)(0.881 g) = 1.322 g. 5. Per Section 21.4 of ASCE 7-16, SM1 = (1.5)(SD1) = (1.5)(0.728 g) = 1.092 g. 6. Per Section 21.4 of ASCE 7-16, SDS shall be taken as 90 percent of the maximum spectral acceleration (Sa) obtained from the site- specific spectrum at any period within the range from 0.2 to 5 seconds, inclusive. 7. Per Section 21.4 of ASCE 7-16, SD1 shall be taken as the maximum value of the product TSa obtained from the site-specific spectrum from the period within the range of 1 to 5 seconds, inclusive. 8. Per Tables 11.6-1 and 11.6-2 of ASCE 7-16, SDS (0.881 g) > 0.50 and SD1 (0.576 g) > 0.2. Thus, the seismic design category is “D”. Conformance to the criteria above for seismic design does not constitute any kind of guarantee or assurance that significant structural damage or ground failure will not occur in the event of a large earthquake. The primary goal of seismic design is to protect life, not to eliminate all damage, since such design may be economically prohibitive. Cumulative effects of seismic events are not addressed in the 2019 CBC (CBSC, 2019) and regular A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 10 GeoSoils, Inc. maintenance and repair following locally significant seismic events (i.e., Mw5.5) will likely be necessary, as is the case in all of Southern California. SECONDARY SEISMIC HAZARDS Liquefaction/Lateral Spreading Liquefaction describes a phenomenon in which cyclic stresses, produced by earthquake-induced ground motion, create excess pore pressures in relatively cohesionless soils. These soils may thereby acquire a high degree of mobility, which can lead to vertical deformation, lateral movement, lurching, sliding, and as a result of seismic loading, volumetric strain and manifestation in surface settlement of loose sediments, sand boils and other damaging lateral deformations. This phenomenon occurs only below the water table, but after liquefaction has developed, it can propagate upward into overlying non-saturated soil as excess pore water dissipates. One of the primary factors controlling the potential for liquefaction is the depth to groundwater. Typically, liquefaction has a relatively low potential at depths greater than 50 feet and is unlikely or will produce vertical strains well below 1 percent for depths below 60 feet when relative densities are 40 to 60 percent and effective overburden pressures are two or more atmospheres (i.e., 4,232 pounds per square foot [Seed, 2005]). The condition of liquefaction has two principal effects. One is the consolidation of loose sediments with resultant settlement of the ground surface. The other effect is lateral sliding. Significant permanent lateral movement generally occurs only when there is significant differential loading, such as fill or natural ground slopes within susceptible materials. No such loading conditions exist at the site. Liquefaction susceptibility is related to numerous factors and the following five conditions should be concurrently present for liquefaction to occur: 1) sediments must be relatively young in age and not have developed a large amount of cementation; 2) sediments must generally consist of medium- to fine-grained, relatively cohesionless sands; 3) the sediments must have low relative density; 4) free groundwater must be present in the sediment; and 5) the site must experience a seismic event of a sufficient duration and magnitude, to induce straining of soil particles. Only about one to perhaps two of these five necessary conditions have the potential to affect the site, concurrently. Summary It is the opinion of GSI that the susceptibility of the site to experience damaging deformations from seismically-induced liquefaction is relatively low owing to the dense, nature of the old paralic deposits that underlie the site in the near-surface and the depth to groundwater. In addition, the recommendations for remedial earthwork and foundations would further reduce any significant liquefaction potential. A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 11 GeoSoils, Inc. OTHER GEOLOGIC/SECONDARY SEISMIC HAZARDS The following list includes other geologic/seismic related hazards that have been considered during our evaluation of the site. The hazards listed are considered negligible or mitigated as a result of site location, soil characteristics, and typical site development procedures: •Subsidence •Coseismic Deformation (Ground Lurching or Shallow Ground Rupture) •Tsunami •Seiche EARTH MATERIAL EXCAVATION CHARACTERISTICS No significant difficulty was encountered while excavating the test pits with a John Deere 410 rubber-tire backhoe. Based on our onsite observations and our past experience with nearby sites, GSI anticipates that relatively easy to moderately difficult excavation would be encountered during the planned and remedial excavations, using standard heavy earth- moving equipment in good working order. However, localized areas of cemented old paralic deposit (i.e., concretions) may present very difficult excavation, especially if relatively lightweight excavation equipment such as a backhoe or mini-excavator are used. Therefore, excavation equipment should be appropriately sized and powered for the required excavation task. If additional information regarding the excavation characteristics of the onsite earth materials is needed, this office can perform seismic refraction studies. LABORATORY TESTING General Laboratory tests were performed on relatively undisturbed and representative bulk samples of the onsite earth materials, collected from the test pits, in order to evaluate their physical characteristics and engineering properties. The test procedures used and results obtained are presented below. Classification Soils were classified visually according to the Unified Soils Classification System (Sowers and Sowers, 1979). The soil classifications are shown on the Test Pit Logs in Appendix B. A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 12 GeoSoils, Inc. Moisture-Density Relations The field moisture contents and dry unit weights were evaluated for relatively undisturbed samples of the onsite earth materials in the laboratory. Testing was performed in general accordance with ASTM D 2937 and ASTM D 2216. The dry unit weight was determined in pounds per cubic foot (pcf), and the field moisture content was determined as a percentage of the dry weight. The results of these tests are shown on the Test Pit Logs in Appendix B. Expansion Index A representative sample of the onsite earth materials was evaluated for expansion potential. Expansion index (E.I.) testing and expansion potential classification were performed in general accordance with ASTM Standard D 4829. The results of the expansion index testing are presented in the following table: SAMPLE LOCATION AND DEPTH (FT)EXPANSION INDEX EXPANSION POTENTIAL TP-5 @ 5-6 < 5 Very Low E.I. = 0 to 20 - Very Low Expansion Potential; E.I. = 21 to 50 - Low Expansion Potential; E.I. = 51 to 90 - Medium Expansion Potential; E.I. = 91 to 130 - High Expansion Potential; E.I. = 130 - Very High (Critical) Expansion Potential Saturated Resistivity, pH, and Soluble Sulfates, and Chlorides Testing was performed on a representative sample of the onsite earth materials for general evaluations of soil corrosivity and soluble sulfates, and chlorides. More specifically, the testing included evaluations of soil pH, soluble sulfates, chlorides, and saturated resistivity. Test results are presented in Appendix D and the following table: SAMPLE LOCATION AND DEPTH (FT)pH SATURATED RESISTIVITY (ohm-cm) SOLUBLE SULFATES (% by weight) SOLUBLE CHLORIDES (ppm) TP-1 @ 0-5¼7.3 2,600 0.004 96 Corrosion Summary Laboratory testing indicates that the tested sample of the onsite soils is neutral with respect to soil acidity/alkalinity; is moderately corrosive to exposed, buried metals when moist; presents negligible sulfate exposure to concrete (Exposure Class S0 per Table 19.3.1.1 of A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 13 GeoSoils, Inc. ACI 318-14 [ACI, 2014]); and contains slightly elevated concentrations of soluble chlorides that are below action levels. GSI does not consult in the field of corrosion engineering. Therefore, additional comments and recommendations may be obtained from a qualified corrosion engineer based on the level of corrosion protection required for the project, as determined by the project architect, civil engineer, and structural engineer. PRELIMINARY CONCLUSIONS Based on our review of the available geologic and geotechnical information for the subject property and the data obtained from our recent field exploration, and laboratory testing, the proposed site development is considered technically feasible from a geotechnical perspective, provided the preliminary recommendations presented herein are properly incorporated into the project. The most significant geotechnical factors relative to the proposed site development, include: •Earth material characteristics and the depth to suitable bearing materials below the existing grades. •On-going expansion and corrosion potentials of the onsite earth materials. •Excavation productivity. •The engineering suitability of the existing retaining wall and associated backfill near the northern property boundary. •Perimeter conditions and the associated limitations to remedial grading near the property boundaries and within the influence of existing settlement-sensitive improvements. •Potential for perched groundwater to manifest during and following site development. •Temporary slope stability. •Regional seismic activity. These factors are further described below. The preliminary geotechnical recommendations presented herein consider these as well as other aspects of the site. The project-specific engineering analyses concerning site preparation and the design, and construction of the proposed improvements were performed using the information obtained during our research, field exploration, and laboratory testing. In the event that any significant changes are made to the proposed site development, the conclusions and recommendations contained in this report shall not be considered valid unless the A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 14 GeoSoils, Inc. changes are reviewed and the recommendations of this report are evaluated or modified in writing by this office. Foundation design parameters are considered preliminary until the foundation design, layout, and structural loads are provided to this office for review. 1.Geotechnical observation, and testing services should be performed during earthwork construction to aid the contractor in removing unsuitable soils and in their effort to compact the fill. 2.Geologic observations should be performed during any excavation and grading to verify or further evaluate the onsite geologic conditions. Although unlikely, if adverse geologic structures are encountered, supplemental recommendations and earthwork may be warranted. 3.All undocumented artificial fill and the weathered, near-surface portions of the existing compacted fill materials placed under the purview of CG (2004) are considered potentially compressible in their existing state. Therefore, these earth materials should not be relied upon for the support of the planned settlement- sensitive improvements (i.e., the proposed single-family residence, the ADU, the swimming pool, pavements, underground utilities, etc.) or new planned fills without mitigation. 4.In general, the available subsurface data indicates that remedial grading excavations for the removal of potentially compressible earth materials, within the proposed project area, will need to extend to depths ranging between approximately 1 foot and 1¼ feet below the existing grades. However, local variations of unsuitable soil thicknesses are likely, and thicker sections of potentially compressible earth materials may occur within the project area, and require deeper remedial grading excavations. This should be considered during project planning and budgetary considerations. 5.The engineering of the existing retaining wall near the northern property boundary is currently unknown. The construction and backfill of this retaining wall is not discussed in CG (2004). Thus, it is currently unknown if this retaining wall is capable of accommodating surcharge from the proposed structures and traffic, or if the backfill is suitable to support the proposed settlement-sensitive improvements. On a preliminary basis, GSI recommends that the planned improvements be located below a 1:1 (h:v) plane projected up and toward the south from the bottom, outboard edge of the retaining wall footing. In addition, the proposed site improvements should not be constructed upon the retaining wall backfill without further evaluation. The client may consider the retention of a structural engineer to evaluate the engineering suitability of the existing retaining wall. 6.The 2019 CBC (CBSC, 2019) indicates that the removal of potentially compressible soils be performed across all areas to be graded under the purview of the grading A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 15 GeoSoils, Inc. permit, not just within the influence of the proposed improvements. Relatively thick sections of potentially compressible soils located near the property boundaries or existing onsite, or offsite improvements that need to remain in service may necessitate a special zone of consideration, on perimeter/confining areas. This zone would be approximately equal to the depth to suitable bearing materials below the existing grades, near the perimeter of the site or existing onsite, or offsite improvements that need to remain is service, if remedial grading cannot be performed onsite or offsite. Thus, any proposed settlement-sensitive improvements and planned fills, constructed within this zone, may require deepened foundations, reinforcement, etc., or will retain some potential for settlement and associated distress. On a preliminary basis, the width of this zone may be on the order of 1 foot to 1¼ feet. 7.Groundwater is not considered a significant geotechnical factor relative to the proposed development. Owing to the nature of the onsite earth materials, perched groundwater may manifest both during and following site development along zones of contrasting permeabilities (i.e., fill lifts and the geologic contact between fill and the old paralic deposits) or within geologic discontinuities in the old paralic deposits. 8.On a preliminary basis, unsupported temporary slopes with gross overall heights of 20 feet or less, exposing unsaturated, relatively cohesive earth materials, may be constructed in accordance with California Occupational Safety and Health Act (CAL/OSHA) or United States Department of Labor OSHA guidelines for Type “B” soils (i.e., 1:1 [h:v] temporary slope gradient). Although not anticipated, should groundwater, seepage, or running sands be observed in the temporary slopes, the slopes may require reconstruction to flatter gradients or the use of shoring, or slot grading. All temporary slopes should be observed by a licensed engineering geologist or engineer prior to entry by an unprotected worker. Should adverse conditions be exposed, additional recommendations regarding temporary slope construction would be provided at that time. 9.The seismicity-acceleration values provided herein should be considered during the design and construction of the proposed development. 10.General Earthwork and Grading Guidelines are provided at the end of this report as Appendix E. Specific recommendations are provided below. PRELIMINARY EARTHWORK RECOMMENDATIONS General Grading should conform to the guidelines presented in Appendix J of the 2019 CBC (CBSC, 2019), the requirements of the City of Carlsbad, and the Grading Guidelines A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 16 GeoSoils, Inc. presented in Appendix E, except where specifically superceded in the text of this report. In case of conflict, the most conservative approach should govern. Prior to grading, a GSI representative should be present at the pre-construction meeting to provide additional grading guidelines, if needed, and to review the earthwork schedule. Demolition/Grubbing 1.All vegetation should be removed from the areas of proposed grading/earthwork. 2.Cavities or loose soils remaining after site clearance should be cleaned out and observed by the geotechnical consultant. The cavities should be backfilled with fill materials that have been uniformly moisture conditioned to at least the soil’s optimum moisture content, and compacted to a minimum relative density of 90 percent of the laboratory standard (ASTM D 1557). Alternatively, the cavities may be filled with a 1- to 2-sack sand-cement slurry. 3.Although not anticipated, any abandoned existing underground utilities should be removed as part of the remedial earthwork recommended herein. Abandoned underground utilities that extend beyond the earthwork areas should be capped or plugged with concrete. 4.GSI observed the possible outlet of the subdrain for the existing retaining wall near the northwest property corner. The subdrain outlet should be connected to a suitable discharge point determined by the project civil engineer or architect. Remedial Grading Potentially compressible undocumented artificial fill and weathered portions of the compacted fill placed under the purview of CG (2004) should be removed to expose suitable, unweathered compacted fill with a minimum in-place relative density of 90 percent of the laboratory standard (per ASTM D1557). Thus, the geotechnical consultant should perform field density testing during remedial excavation. Based on the available subsurface data, the remedial grading excavations are anticipated to extend to depths ranging between approximately 1 foot and 1¼ feet below the existing grades. However, variations are possible and the localized need for deeper remedial excavation cannot be entirely precluded, and should be anticipated. The lateral limits of the remedial excavations should extend at least 5 feet beyond the perimeter foundation of the proposed structures and at least 2 feet outside the perimeters of proposed surface improvements (i.e., driveway, walkways, patios, etc.) unless constrained by property lines or existing improvements that need to remain in service. The exposed subsoils should be lightly scarified, uniformly moisture conditioned to at least the soil’s optimum moisture content, and then be recompacted to a minimum relative density of 90 percent of the laboratory standard (ASTM D 1557). Remedial grading excavations should be observed by the geotechnical consultant prior to scarification and fill placement. A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 17 GeoSoils, Inc. Overexcavation Although not anticipated, in the event that the project requires planned excavations that would place the foundations for the proposed single-family residence and the ADU within 2 feet of the old paralic deposits, the old paralic deposits should be overexcavated (undercut) to provide for at least 24 inches of compacted fill beneath the foundations. The overexcavation bottom should be sloped toward James Drive and observed by the geotechnical consultant. Following geotechnical observation, the bottom of the overexcavation should be lightly scarified, uniformly moisture conditioned to at least the soil’s optimum moisture content, and then be recompacted to a minimum relative density of 90 percent of the laboratory standard (ASTM D 1557). The maximum to minimum compacted fill thickness across the property should not exceed a ratio of 3:1 (maximum:minimum). Compacted Fill Materials Soils intended for use as compacted fill should be cleaned of any organic materials and deleterious debris, uniformly moisture conditioned to at least the soil’s optimum moisture content, placed in relatively thin lifts, and then be recompacted to a minimum relative density of 90 percent of the laboratory standard (ASTM D 1557). Each fill lift should be compacted prior to the placement of the successive lift. The geotechnical consultant should provide observations and field density testing during fill placement. Fill materials should consist of granular soils with an expansion index of 20 or less and a plasticity index of 14 or less. The use of soils with higher expansion index and plasticity index values in compacted fills will require revisions to the herein provided recommendations for foundations, slab-on-grade floors, the swimming pool, and pavements to mitigate shrink/swell and subgrade deformations. Import Soils If import fill is necessary, a sample of the soil import should be evaluated by this office prior to importing, in order to assure compatibility with the onsite soils and the recommendations presented in this report. If non-manufactured materials are used, environmental documentation for the export site should be provided for GSI review. At least five (5) business days of lead time should be allowed by builders or contractors for proposed import submittals. This lead time will allow for environmental document review and laboratory testing, as deemed necessary. At a minimum, import soils should have an expansion index of 20 or less and a plasticity index of 14 or less. The use of subdrains at the bottom of the fill cap may be necessary, and may be subsequently recommended based on compatibility with onsite soils. A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 18 GeoSoils, Inc. Temporary Slopes Temporary slopes for excavations less than 20 feet in overall height should conform to CAL/OSHA or OSHA requirements for Type “B” soils, provided groundwater, seepage, or running sands are not present. Temporary slopes, up to a maximum height of about 20 feet, may be excavated at a 1:1 (h:v) gradient, or flatter, provided groundwater, seepage, or running sands are not exposed. Construction materials and soil stockpiles, or construction equipment storage, and traffic should not occur within “H” of any temporary slope, where “H” equals the height of the temporary slope. All temporary slopes should be observed by a licensed engineering geologist or engineer prior to worker entry into the excavation. Based on the exposed field conditions, inclining temporary slopes to flatter gradients or the use of shoring may be necessary if adverse conditions are observed. If adverse conditions are exposed or if temporary slopes conflict with property boundaries, or existing improvements that need to remain in service, shoring or slot excavations/slot grading may be necessary. The need for shoring or slot excavations/slot grading could be further evaluated during the plan review stage of site development and during site earthwork. Temporary slopes should not pass below a 1:1 (h:v) plane projected down and toward the excavation from proposed and existing settlement-sensitive improvements, or property lines without the use of shoring or slot excavations/slot grading. Slot Excavation/Slot Grading Slot excavation/slot grading may be performed as an alternative to shoring where planned and remedial excavations extend below a 1:1 (h:v) plane projected down and toward the excavation from the proposed improvements and existing settlement-sensitive improvements that need to remain in service, or property lines. The slot excavations may be performed in an “A,” “B,” and “C” sequence, with a maximum slot width of 6 feet. Multiple slots may be simultaneously excavated provided that open slots are separated by at least 12 feet of tested and approved compacted fill or undisturbed soils. The actual number and widths of the slot excavations should not cause the bearing pressure of any existing, adjacent foundation to increase by more than 2.0 times the allowable bearing pressure. This will require proper sequencing during construction. Pre-construction surveys and survey monitoring should be performed in conjunction with slot grading. Excavation Observation and Monitoring (All Excavations) When excavations are made adjacent to an existing improvement (i.e., underground utility, wall, road, building, wall, etc.) there is a risk of some damage even if a well-designed system of excavation is planned and executed. We, therefore, recommend that a systematic program of observations be made before, during, and after construction to determine the effects (if any) of the excavation on existing improvements. We believe that this is necessary for two reasons. First, if excessive movements (i.e., more than ½ inch) are detected early enough, remedial measures can be taken which could A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 19 GeoSoils, Inc. possibly prevent serious damage to existing improvements. Second, the responsibility for damage to the existing improvement can be evaluated more equitably, if the cause and extent of the damage can be determined more precisely. Monitoring should include the measurement of any horizontal and vertical movements of the existing structures/improvements. Locations and types of monitoring devices should be selected prior to the start of construction. The program of monitoring should be agreed upon between the project team, the site surveyor, and the geotechnical consultant, prior to excavation. Reference points should be provided on existing walls, buildings, and other settlement-sensitive improvements. These points should be placed as low as possible on the walls and buildings adjacent to the excavation. Exact locations may be dictated by critical points, such as bearing walls or columns for buildings; and surface points on roadways or curbs, near the top of the excavation. For a survey monitoring system, an accuracy of a least 0.01 foot should be required. Reference points should be installed and read initially prior to excavation. The readings should continue until all construction below ground has been completed and the permanent backfill has been brought to finish grade. The frequency of readings will depend upon the results of previous readings and the rate of construction. Weekly readings could be assumed throughout the duration of construction with daily readings during rapid excavation near the bottom of the excavation. The readings should be plotted by the project surveyor/civil engineer and then reviewed by the geotechnical consultant. In addition to the monitoring system, it would be prudent for the geotechnical consultant and the contractor to make a complete inspection of the existing structures and improvements both before and after construction. The inspection should be directed toward detecting any signs of damage, particularly those caused by settlement. Notes should be made and pictures should be taken where necessary. PRELIMINARY RECOMMENDATIONS - FOUNDATIONS AND CONCRETE SLAB-ON-GRADE FLOORS Preliminary geotechnical recommendations for foundation and concrete slab-on-grade floor design and construction are provided in the following sections. These preliminary recommendations have been developed from our understanding of the currently proposed site development, our review of CG (2004), as well as our site observations, subsurface exploration, laboratory testing, and engineering analyses. Foundation and concrete slab-on-grade floor design should be re-evaluated at the conclusion of site grading/remedial earthwork for the as-graded soil conditions. Although not anticipated, revisions to these recommendations may be necessary. If the information concerning the proposed development plan is not correct, or any changes in the design, location or A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 20 GeoSoils, Inc. loading conditions of the proposed single-family residence and ADU are made, the conclusions and recommendations contained in this report shall not be considered valid unless the changes are reviewed and conclusions of this report are modified or approved in writing by this office. The information and recommendations presented in the following sections are not meant to supercede design by the project structural engineer or a civil engineer specializing in structural design. Upon request, GSI could provide additional input/consultation regarding soil parameters, as related to foundation design. The existing geotechnical data (CG, 2004) and our expansion index testing indicate the subject property is underlain by soils that are very low in expansion potential (E.I. < 20). In the following sections, GSI provides preliminary design and construction recommendations for foundations and concrete slab-on-grade floor systems underlain by soils that are very low in expansion potential. Preliminary Foundation and Concrete Slab-on-Grade Floor Design and Construction Recommendations The following preliminary recommendations are for the design of shallow foundations and slab-on-grade floors underlain by soils with an E.I. of 20 or less and a plasticity index of 14 or less: 1.The foundation system should be designed and constructed in accordance with guidelines presented in the 2019 CBC. 2.Foundations for the proposed single-family residence and ADU should extend into tested and approved compacted fill overlying dense old paralic deposits. 3.An allowable bearing value of 2,000 pounds per square foot (psf) may be used in the design of continuous spread footings that maintain minimum widths of 12 or 15 inches for one- or two- story buildings, respectively, and minimally extend 12 or 18 inches below the lowest adjacent grade for one- or two-story buildings, respectively. A similar bearing value may be used in the design of isolated spread footings that have a minimum dimension of at least 24 inches square and a minimum embedment depth of 24 inches below the lowest adjacent grade. Foundation embedment depth excludes the thickness of exterior pavements, concrete slab-on-grade floors, or the slab underlayment section. The bearing value may be increased by 20 percent for each additional 12 inches in footing depth to a maximum value of 2,500 psf. The bearing value may be increased by one-third when considering short duration seismic or wind loads. 4.For foundations deriving passive resistance from approved compacted fill that is very low in expansion potential (expansion index of 20 or less and a plasticity index A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 21 GeoSoils, Inc. of 14 or less), the passive earth pressure may be computed as an equivalent fluid having a density of 250 psf/ft (pounds per cubic foot [pcf]), with a maximum earth pressure of 2,500 psf. 5.The upper 6 inches of passive pressure should be neglected, if not confined by slabs or pavement. 6.For lateral sliding resistance, a 0.35 coefficient of friction may be used for a concrete to soil contact when multiplied by the dead load. 7.When combining passive pressure and frictional resistance, the passive pressure component should be reduced by one-third. 8.Although not anticipated, based on the existing site topography, all footing setbacks from slopes should comply with Figure 1808.7.1 of the 2019 CBC. GSI recommends a minimum horizontal setback distance of 7 feet, as measured from the bottom, outboard edge of the footing to the face of descending slopes. 9.Footings for the proposed buildings adjacent to existing or proposed retaining walls should be deepened so as to extend below a 1:1 (h:v) plane projected up and toward the proposed buildings from the heel of the retaining wall footing. 10.At a minimum, all continuous footings should be reinforced with four No. 4 steel reinforcing bars. Two reinforcing bars should be placed near the top and two bars should be placed near the bottom of the continuous footings. Isolated spread footings should be reinforced in accordance with the recommendations of the project structural engineer. 11.All interior and exterior isolated spread footings should be tied to the perimeter foundation via a reinforced grade beam in at least one direction. The grade beam should be at least 12 inches square in cross section, and should be provided with a minimum of one No. 4 steel reinforcing bar placed near the top, and one No. 4 steel reinforcing bar placed near the bottom of the grade beam. The base of the reinforced grade beam should be at the same elevation as the adjoining footings. This may require the use of a stepped grade beam, if there are differences in the bearing elevations. 12.A grade beam, reinforced as previously recommended and at least 12 inches square, should be provided across large entrances. The base of the reinforced grade beam should be at the same elevation as the adjoining footings. 13.Stepped footings or grade beams should conform to the requirements in Section 1809.3 of the 2019 CBC. A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 22 GeoSoils, Inc. 14.A minimum concrete slab-on-grade floor thickness of 4½ inches is recommended. A thicker concrete slab-on-grade floor should be used if moisture/water vapor transmission through the floor slab would adversely affect flooring applications or other building components (State of California, 2022), The actual thickness of the slab-on-grade floor should be provided by the project structural engineer based on the anticipated loading conditions and the intended use. 15.At a minimum, concrete slab-on-grade floors should be reinforced with No. 3 steel reinforcing bars placed at 18 inches on center, in two horizontally perpendicular directions (i.e., long axis and short axis). The actual slab-on-grade floor reinforcement should be provided by the project structural engineer based on the planned loading and use. 16.All slab-on-grade floor reinforcement should be supported on chairs (“dobies”) to ensure proper mid-slab height positioning during placement of the concrete. Hooking of reinforcement is not an acceptable method of positioning. 17.Slab subgrade pre-soaking is not required for soils that are very low in expansion potential. However, the client and their contractor should consider pre-wetting the slab subgrade materials to at least the soil’s optimum moisture content to a minimum depth of 12 inches below pad grade, no more than 72 hours prior to the placement of the underlayment sand and vapor retarder. 18.Prior to placement of the concrete, the footing excavations should be lightly moisture conditioned to assist in uniform concrete curing. Care should be taken to not moisten any sand cushion placed between the bottom of the slab-on-grade floor and the vapor retarder. Foundation Settlement Provided that the earthwork recommendations in this report are properly followed, foundations bearing on tested and approved compacted fill, overlying suitable dense old paralic deposits, should be designed to accommodate a total settlement of at least 1½ inches and a differential settlement of no less than ¾-inch over a 40-foot horizontal span (angular distortion = 1/640). SOIL MOISTURE TRANSMISSION CONSIDERATIONS GSI has evaluated the potential for moisture or water vapor transmission through new concrete floor slabs, in light of typical floor coverings and improvements. According to Kanare (2005), slab moisture emission rates range from about 2 to 27 lbs/24 hours/1,000 square feet from a typical slab-on-grade floor, while floor covering manufacturers generally recommend about 3 lbs/24 hours as an upper limit. A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 23 GeoSoils, Inc. The recommendations in this section are not intended to preclude the transmission of moisture or water vapor through the building foundations or slab-on-grade floors. Foundation systems and slab-on-grade floors shall not allow moisture or water vapor to enter into the structure so as to cause damage to another building component or to limit the installation of the type of flooring materials typically used for the particular application (State of California, 2022). These recommendations may be superceded or supplemented by a waterproofing consultant, the project architect, or structural consultant. Thus, the client will need to evaluate the following in light of a cost vs. benefit analysis (owner expectations and repairs/replacement). Also, moisture or water vapor transmission will occur in new slab-on-grade floors as a result of chemical reactions taking place within the curing concrete. Moisture or water vapor transmission through concrete floor slabs as a result of concrete curing has the potential to adversely affect sensitive floor coverings depending on the thickness of the concrete floor slab and the duration of time between the placement of concrete, and the installation of the floor covering. It is possible that a slab moisture sealant may be needed prior to the placement of sensitive floor coverings if the time frame between the foundation and concrete slab-on-grade floor construction, and the installation of the floor coverings, is relatively short. Considering the expansion index test results presented herein, and known soil conditions in the region, the anticipated typical moisture or water vapor transmission rates, floor coverings, and improvements (to be chosen by the client and the project architect) that can tolerate moisture or water vapor transmission rates without significant distress, the following alternatives are provided: •The thickness of the concrete slab-on-grade floors should be increased beyond 4½ inches. •Concrete slab underlayment should consist of a 15-mil vapor retarder, or equivalent, with all laps sealed per the 2019 CBC and the manufacturer’s recommendations. The vapor retarder should comply with the American Society for Testing and Materials (ASTM) E 1745 - Class A criteria, and be installed in accordance with the latest editions of American Concrete Institute (ACI) 302.1R-15 and ASTM E 1643. •The 15-mil vapor retarder (ASTM E 1745 - Class A) shall be installed per the recommendations of the manufacturer, including all penetrations (i.e., pipe, ducting, rebar, etc.). •The concrete slab-on-grade floor should be immediately underlain by a sand cushion consisting of 2 inches of clean, washed sand (SE > 30), placed atop a 15-mil vapor retarder (ASTM E-1745 -Class A, per Engineering Bulletin 119 [Kanare, 2005]) that is installed per the recommendations of the manufacturer, including all penetrations (i.e., pipe, ducting, rebar, etc.). The manufacturer shall provide instructions for lap sealing, including minimum width of lap, method of sealing, and either supply or specify suitable products for lap sealing (ASTM E 1745), and per code. A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 24 GeoSoils, Inc. ACI 302.1R-15 (ACI, 2015) states, “Experience has shown, however, that the greatest level of protection for floor coverings, coatings, or building environments is provided when the vapor retarder/barrier is placed in direct contact with the slab. Placing concrete in direct contact with the vapor retarder/barrier eliminates the potential for water from sources such as rain, saw-cutting, curing, cleaning, or compaction to become trapped within the fill course. Wet or saturated fill above the vapor retarder/barrier can significantly lengthen the time required for a slab to dry to a level acceptable to the manufacturers of floor coverings, adhesives, and coatings. A fill layer sandwiched between the vapor retarder/barrier and the concrete slab-on-grade floor also serves as an avenue for moisture to enter and travel freely beneath the slab, which can lead to an increase in moisture within the slab once it is covered. Moisture can enter the fill layer through voids, tears, or punctures in the vapor retarder/barrier.” Therefore, additional observation and testing will be necessary for the cushion or sand layer for moisture content, and relatively uniform thicknesses, prior to the placement of concrete. Conversely, ACI 302.1R-15 indicates that placing concrete directly upon the vapor retarder requires additional design and construction considerations to avoid potential slab-related problems, such as excessive concrete settlement and significantly larger length change during casting and drying shrinkage, and when the concrete is subject to environmental changes. In addition, dominant joint behavior can be made worse when the slab is placed in direct contact with the vapor retarder. Further, settlement cracking over reinforcing steel is more likely because of increased settlement resulting from a longer bleeding period. There is also a potential for enhanced slab curl. Lastly, if rapid surface drying conditions are present, the surface of the concrete (i.e., top fraction of an inch [millimeter]) placed directly upon the vapor retarder would have a greater propensity to dry and crust over leaving the underlying concrete relatively less stiff or unhardened. This may impact surface flatness of the concrete slab and result in blistering or delamination. Design and construction measures should be implemented to offset or reduce these effects. Given the above, GSI recommends that all responsible parties participate in a risk/benefit evaluation regarding the specified location of the vapor retarder during project design. •For building pad areas underlain by soils very low in expansion potential (expansion index of 20 or less and plasticity index of 14 or less), the vapor retarder should be underlain by a capillary break consisting of a 2-inch thick layer of clean, washed sand (SE > 30), placed directly on the prepared, moisture conditioned, and compacted subgrade. The vapor retarder should be sealed to provide a continuous membrane under the entire slab, as discussed above. •Concrete with a maximum water-to-cement ratio of 0.50 should be used in the construction of the building foundations and slab-on-grade floors. A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 25 GeoSoils, Inc. •The building owner should be specifically advised which areas are suitable for tile flooring, vinyl flooring, or other types of water/vapor-sensitive flooring and which are not suitable. In all planned floor areas, flooring shall be installed per the manufacturer’s recommendations. •Additional recommendations regarding moisture or water vapor transmission should be provided by the project architect, structural engineer, or waterproofing consultant, and should be consistent with the specified floor coverings indicated by the project architect. Regardless of the mitigation, some limited moisture/water vapor transmission through the building foundations and slab-on-grade floors should be anticipated. Construction crews may require special training for installation of certain product(s), as well as concrete finishing techniques. The use of specialized product(s) should be approved by the slab designer and waterproofing consultant. A technical representative of the flooring contractor should review the floor slab and moisture retarder plans and provide comment prior to the construction of the foundations or improvements. The vapor retarder contractor should have representatives from the vapor retarder manufacturer onsite during the initial installation. PRELIMINARY RETAINING WALL DESIGN PARAMETERS General The following preliminary recommendations are provided for the design and construction of conventional masonry (concrete masonry unit [CMU]) and cast-in-place concrete [CIPC]) retaining walls with retained soil heights of 10 feet or less. Recommendations for specialty walls (i.e., crib, earthstone, mechanical stabilized earth [MSE] retaining walls, etc.) can be provided upon request, and would be based on site-specific conditions. Conventional Retaining Walls The design parameters provided below assume that either select materials (typically Class 2 permeable filter material or Class 3 aggregate base) or native onsite earth materials with an expansion index of 20 or less and a plasticity index of 14 or less are used to backfill any retaining wall. The latter case would require compliance testing prior to or during wall construction. It may be possible to use some of the onsite earth materials for retaining wall backfill, provided that laboratory testing demonstrates they meet the minimum backfill properties recommended herein. The type of backfill (i.e., select or native), should be specified by the wall designer, and clearly shown on the retaining wall plans. Waterproofing should also be considered for all retaining walls in order to reduce the potential for unsightly efflorescence staining, spalling stucco, etc. A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 26 GeoSoils, Inc. Preliminary Retaining Wall Foundation Design The preliminary foundation design for retaining walls that will be included in the proposed development should incorporate the following recommendations: Minimum Footing Embedment - 24 inches below the lowest adjacent grade into tested and approved, compacted fill overlying suitable dense old paralic deposits. Footing embedment excludes the landscape layer (typically the upper 6 inches of soil) and any adjacent pavements. Where potentially compressible earth materials cannot be removed and recompacted below a 1:1 (h:v) plane projected down from the bottom, outboard edge of the proposed retaining wall footing, due to property boundaries or existing improvements that need to remain in service, the wall footing should be founded into suitable, unweathered old paralic deposits. This would likely require a deepened retaining wall footing, based on the available subsurface data. Minimum Footing Width - 24 inches. Allowable Bearing Pressure - An allowable bearing pressure of 2,000 psf may be used in the preliminary design of retaining wall foundations provided that the footing maintains a minimum width of 24 inches and extends at least 24 inches below the lowest adjacent grade into tested and approved compacted fill, overlying suitable dense old paralic deposits or into suitable dense old paralic deposits. This pressure may be increased by one-third for transient short-term wind or seismic loads. Passive Earth Pressure - A passive earth pressure of 250 psf/ft (pcf) with a maximum earth pressure of 2,500 psf may be used in the preliminary design of retaining wall foundations founded into tested and approved compacted fill materials overlying suitable dense old paralic deposits or into suitable dense old paralic deposits that are very low in expansion potential. Lateral Sliding Resistance - A 0.35 coefficient of friction may be used for a concrete to soil contact when multiplied by the dead load. When combining passive pressure and frictional resistance, the passive pressure component should be reduced by one-third. Backfill Soil Density - Backfill soil densities ranging between 125 pcf and 130 pcf may be used in the design of the proposed retaining walls. This assumes an average backfill compaction of at least 90 percent of the laboratory standard (per ASTM D 1557). Footing Setbacks - Although not anticipated based on the relatively flat-lying site topography, all retaining wall footing setbacks from slopes should comply with Figure 1808.7.1 of the 2019 CBC. GSI recommends a minimum horizontal setback A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 27 GeoSoils, Inc. distance of 7 feet, as measured from the bottom, outboard edge of the footing to the face of descending slopes. Restrained Walls Any retaining wall that will be restrained prior to placing and compacting backfill material or retaining walls that have re-entrant or male corners, should be designed for an at-rest equivalent fluid pressure (EFP) of 55 pcf and 65 pcf for select and very low expansive native backfill, respectively. The design should include any applicable surcharge loading. For areas of male or re-entrant corners, the restrained wall design should extend a minimum distance of twice the height of the wall (2H) laterally from the corner. Cantilevered Walls The recommendations presented below are for cantilevered retaining walls with retained soil heights up to 10 feet. Design parameters for retaining walls less than 3 feet in height may be superceded by the regional standard design. Regional standard design retaining walls require the use of select backfill materials owing to the low equivalent fluid pressure used in their design. Active earth pressure may be used for retaining wall design, provided the top of the wall is not restrained from minor deflections. An equivalent fluid pressure approach may be used to compute the horizontal pressure against the wall. Appropriate fluid unit weights are given below for specific slope gradients of the retained material. These do not include other superimposed loading conditions due to traffic, structures, seismic events or adverse geologic conditions. When wall configurations are finalized, the appropriate loading conditions for superimposed loads can be provided upon request. For preliminary planning purposes, the structural consultant/wall designer should incorporate the surcharge of traffic on the back of retaining walls if traffic will occur within “H” of the backside of the retaining walls, where “H” equals the retained soil height. The traffic surcharge may be taken as 100 psf/ft in the upper 5 feet of the wall for light passenger vehicle traffic (i.e., cars, pickup trucks, etc.). Traffic surcharge from heavy-axle trucks (HS20) should be modeled as 300 psf/ft in the upper 5 feet of the wall. This does not include the surcharge of parked vehicles which should be evaluated at a higher surcharge to account for the effects of seismic loading. Equivalent fluid pressures for the design of cantilevered retaining walls are provided in the following table: A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 28 GeoSoils, Inc. SURFACE SLOPE OF RETAINED MATERIAL (HORIZONTAL:VERTICAL) EQUIVALENT FLUID WEIGHT P.C.F. (SELECT BACKFILL)(2) EQUIVALENT FLUID WEIGHT P.C.F. (NATIVE BACKFILL)(3) Level(1) 2 to 1 38 55 50 65 (1) Level backfill behind a retaining wall is defined as compacted earth materials, properly drained, without a slope for a distance of 2H behind the wall, where H is the height of the wall. (2) SE > 30, P.I. < 14, E.I. < 20, and < 10% passing No. 200 sieve. (3) E.I. = 0 to 20, SE > 30, P.I. < 14, E.I. < 20, and < 15% passing No. 200 sieve. Seismic Surcharge For retaining walls incorporated into the buildings, site retaining walls with more than 6 feet of retained materials, as measured vertically from the bottom of the wall footing at the heel to daylight, or retaining walls that could present ingress/egress constraints in the event of failure, GSI recommends that the walls be evaluated for seismic surcharge in general accordance with 2019 CBC requirements. The retaining walls in this category should maintain an overturning Factor-of-Safety (FOS) of approximately 1.25 when the seismic surcharge (seismic increment), is applied. For restrained walls, the seismic surcharge should be applied as a uniform surcharge load from the bottom of the footing (excluding shear keys) to the top of the backfill at the heel of the wall footing. For cantilevered walls, the seismic surcharge should be applied as an inverted triangular pressure distribution for the portion of the wall located above 0.6H up from the bottom of the footing to the top of the wall, where “H” equals the retained soil height. For the evaluation of the seismic surcharge, the bearing pressure may exceed the static value by one-third, considering the transient nature of this surcharge. This is for local wall stability only. This seismic surcharge may be taken as 19H where "H" for restrained walls is the dimension previously noted as the height of the backfill to the bottom of the footing. The 19H is derived from the guidelines set forth in City of Los Angeles Department of Building and Safety (LADBS) Information Bulletin Document No.: P/BC 2020-83 (LADBS, 2020), which are based on Seed and Whitman (1970). (EFP (seismic) = ¾kh(soil Where: (EFP (seismic)is the seismic increment expressed as equivalent fluid pressure (pounds per cubic foot [pcf]); kh is the seismic lateral earth pressure coefficient equivalent to one-half of two-thirds of PGAM (0.56 g x b x ½ = 0.19 g); A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 29 GeoSoils, Inc. (soil is the total unit weight of the retained soils (130 pcf). Thus, for the proposed retaining walls: (EFP (seismic) = ¾ x ½ x b x 0.56 x 130 pcf = 18.5 pcf (use 19 pcf [19H]) Retaining Wall Backfill and Drainage Positive drainage must be provided behind all retaining walls in the form of gravel wrapped in geofabric and outlets. A backdrain system is considered necessary for retaining walls that are 2 feet or greater in height. Details 1, 2, and 3, present the backdrainage options discussed below. At a minimum, backdrains should consist of a 4-inch diameter perforated Schedule 40 or SDR 35 drain pipe, with perforations oriented down, encased in ¾-inch to 1½-inch gravel, wrapped in approved filter fabric (Mirafi 140 or equivalent). The backdrain should flow via gravity (minimum 1 percent slope) toward an approved drainage facility identified by the project civil engineer or architect. For select backfill, the filter material should extend a minimum of 1 horizontal foot behind the base of the walls and upward at least 1 foot. For native backfill that has an expansion index up to 20 and a plasticity index up to 14, continuous Class 2 permeable drain materials should be used behind the wall. This material should be continuous (i.e., full height) behind the wall, and it should be constructed in accordance with the enclosed Detail 1 (Typical Retaining Wall Backfill and Drainage Detail). For limited access and confined areas, (panel) drainage behind the wall may be constructed in accordance with Detail 2 (Retaining Wall Backfill and Subdrain Detail Geotextile Drain). Materials with an expansion index greater than 20 and a plasticity index greater than 14 should not be used as backfill for retaining walls. For more onerous expansive soil conditions, backfill and drainage behind the retaining wall should conform with Detail 3 (Retaining Wall And Subdrain Detail Clean Sand Backfill). Retaining wall backfill should be moisture conditioned to at least the soil’s optimum moisture content, placed in relatively thin lifts, and compacted to a minimum relative density of 90 percent of the laboratory standard (ASTM D 1557). Outlets should consist of a 4-inch diameter solid PVC or ABS pipe spaced no greater than about 100 feet apart, with a minimum of two outlets, one on each end. The use of weep holes, only, in walls higher than 2 feet, is not recommended. The surface of the backfill should be sealed by pavement or the top 18 inches should consist of compacted native soil with an expansion index of 50 or less. Proper surface drainage should also be provided around the retaining walls. Wall/Retaining Wall Footing Transitions Site walls are anticipated to be supported by foundations designed in accordance with the recommendations in this report. Should wall footings transition from old paralic deposits to compacted fill, the wall designer may specify either: A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 30 12 inches (1) Waterproofing membrane Provide surface drainage via an engineered V-ditch (see civil plans for details) (5) Weep hole Proposed grade sloped to drain per precise civil drawings (4) Pipe (3) Filter fabric (2) Gravel 2:1 (h:v) slope 1:1 (h:v) or flatter backcut to be properly benched Slope or level Native backfill Very Low to Low Expansive soils, E.I. <50, P.I. <15 (1) Waterproofing membrane. (2) Gravel: Clean, crushed, 3 4 to 11 2 inch. (3) Filter fabric: Mirafi 140N or approved equivalent. (4) Pipe: 4-inch-diameter perforated PVC, Schedule 40, or approved alternative with minimum of 1 percent gradient sloped to suitable, approved outlet point (perforations down). (5) Weep holes: For CMU walls, Omit grout every other block, at or slightly above finished surface. For reinforced concrete walls, minimum 2-inch diameter weep holesspaced at 20 foot centers along the wall and placed 3 inches above finished surface. Design civil engineer to provide drainage at toe of wall. No weep holes for below-grade walls. (6) Footing: If bench is created behind the footing greater than the footing width using level fill or cut natural earth materials, an additional "heel " drain will likely be required by geotechnical consultant. Footing and wall design by others (6) Footing Structural footing or settlement-sensitive improvement H H/3 CMU or reinforced-concrete wall 6 inches (1) Waterproofing membrane (optional)Provide surface drainage via engineered V-ditch (see civil plan details) (5) Weep hole Proposed grade sloped to drain per precise civil drawings (4) Pipe (3) Filter fabric (2) Composite drain CMU or reinforced-concrete wall 2:1 (h:v) slope 1:1 (h:v) or flatter backcut to be properly benched Slope or level Native backfill Very Low to Low Expansive soils E.I. <50, P.I. <15 (1) Waterproofing membrane (optional): Liquid boot or approved mastic equivalent. (2) Drain: Miradrain 6000 or J-drain 200 or equivalent for non-waterproofed walls; Miradrain 6200 or J-drain 200 or equivalent for waterproofed walls (all perforations down). (3) Filter fabric: Mirafi 140N or approved equivalent; place fabric flap behind core. (4) Pipe: 4-inch-diameter perforated PVC, Schedule 40, or approved alternative with minimum of 1 percent gradient to proper outlet point (perforations down). (5) Weep holes: For CMU walls, Omit grout every other block, at or slightly above finished surface. For reinforced concrete walls, minimum 2-inch diameter weep holesspaced at 20 foot centers along the wall and placed 3 inches above finished surface. Design civil engineer to provide drainage at toe of wall. No weep holes for below-grade walls. (6) Gravel: Clean, crushed, 3 4 to 11 2 inch. (7) Footing: If bench is created behind the footing greater than the footing width using level fill or cut natural earth materials, an additional "heel" drain will likely be required by geotechnical consultant. (6) 1 cubic foot of 3 4-inch crushed rock (7) Footing Footing and wall design by others Structural footing or settlement-sensitive improvement (1) Waterproofing membrane Provide surface drainage (5) Weep hole Proposed grade sloped to drain per precise civil drawings (4) Pipe (3) Filter fabric (2) Gravel CMU or reinforced-concrete wall 2:1 (h:v) slope 1:1 (h:v) or flatter backcut to be properly benched Slope or level (8) Native backfill (1) Waterproofing membrane: Liquid boot or approved masticequivalent. (2) Gravel: Clean, crushed, 3 4 to 11 2 inch. (3) Filter fabric: Mirafi 140N or approved equivalent. (4) Pipe: 4-inch-diameter perforated PVC, Schedule 40, or approved alternative with minimum of 1 percent gradient to proper outlet point (perforations down). (5) Weep hole: For CMU walls, Omit grout every other block, at or slightly above finished surface. For reinforced concrete walls, minimum 2-inch diameter weep holesspaced at 20 foot centers along the wall and placed 3 inches above finished surface. Design civil engineer to provide drainage at toe of wall. No weep holes for below-grade walls. (6) Clean sand backfill: Must have sand equivalent value (S.E.) of 35 or greater; can be densified by water jetting upon approval by geotechnical engineer. (7) Footing: If bench is created behind the footing greater than the footing width using level fill or cut natural earth materials, an additional "heel" drain will likely be required by geotechnical consultant. (8) Native backfill: If E.I. <21 and S.E. >35 then all sand requirements also may not be required and will be reviewed by the geotechnical consultant. (6) Clean sand backfill H ±12 inches H/2 minimum Heel width (7) Footing Footing and wall design by others Structural footing or settlement-sensitive improvement GeoSoils, Inc. a)A minimum of a 2-foot overexcavation and recompaction of the old paralic deposits for a distance of 2H, from the point of transition. b)Increase of the amount of reinforcing steel and wall detailing (i.e., expansion joints or crack control joints) such that a angular distortion of 1/360 for a distance of 2H on either side of the transition may be accommodated. Expansion joints should be placed no greater than 20 feet on-center, in accordance with the structural engineer’s/wall designer’s recommendations, regardless of whether or not transition conditions exist. Expansion joints should be sealed with a flexible, non-shrink grout. c) Embed the footings entirely into suitable dense old paralic deposits (i.e., deepened footings). If transitions from old paralic deposits to compacted fill transect the wall footing alignment at an angle of less than 45 degrees (plan view), then the designer should follow recommendation “a” (above) and until such transition is between 45 and 90 degrees to the wall alignment. SURCHARGE OF EXISTING RETAINING WALL Unless evaluated and deemed acceptable by a licensed structural engineer, the existing retaining wall near the northern property boundary should not receive surcharge from planned fills, the proposed improvements, traffic (including heavy construction equipment traffic), soil or building material stockpiles, etc. If the structural engineer concludes that the existing retaining wall cannot tolerate surcharge from the aforementioned, additional loading should be avoided above a 1:1 (h:v) plane projected up and into the site from the heel of the retaining wall footing. Alternatively, the existing retaining wall may be replaced by a new retaining wall that can tolerate the applied surcharge. It is currently unknown if the design of the existing retaining wall considers the effects of seismic loading. Thus, there is a potential that the existing wall may deform or fail in the event of a strong earthquake. Failure or deformation of the wall may have adverse affects on the proposed development. Recommendations for mitigation can be provided once the structural design of the existing wall has been evaluated. PRELIMINARY OUTDOOR POOL/SPA DESIGN RECOMMENDATIONS The following preliminary recommendations are provided for consideration in the design and planning of the proposed pool/spa. A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 34 GeoSoils, Inc. General 1.Refer to the “Preliminary Recommendations - Foundations and Concrete Slab-on-Grade Floors” section of this report for the design and construction of shallow foundations incorporated into the proposed pool/spa. The foundations for retaining walls incorporated into the proposed pool/spa should adhere to the recommendations in the “Preliminary Retaining Wall Foundation Design” section of this report. 2.The equivalent fluid pressure to be used in the pool/spa design should be 60 pcf for pool/spa walls with level backfill, and 75 pcf for a 2:1 (h:v) sloped backfill condition. In addition, backdrains should be provided behind pool/spa walls subjacent to slopes. Should drains not be desired, full hydrostatic pressure (62.4 pcf) should be added to the equivalent fluid pressures indicated above. 3.Where pools/spas are planned near structures, appropriate surcharge loads need to be incorporated into the design and construction by the pool/spa designer. This includes, but is not limited to landscape berms, decorative walls, footings, built-in barbeques, utility poles, etc. 4.All pool/spa walls should be designed as “free standing” and be capable of supporting the water in the pool/spa without soil support. The shape of the pool/spa in cross section and in plan view may affect the performance of the pool/spa, from a geotechnical standpoint. Pools and spas should also be designed in accordance with the latest adopted Codes. The bottoms of the pools/spas, should maintain a distance H/3, where H is the height of the slope (in feet), from the slope face. This distance should not be less than 7 feet, nor need not be greater than 40 feet. 5.Hydrostatic pressure relief valves should be incorporated into the pool and spa designs. A pool/spa under-drain system may also be considered, with an appropriate sump pump and outlet for discharge, but this is not a geotechnical requirement, provided the relief valves are constructed. Sump pumps should be designed and constructed to not cause saturation of the surrounding soils. 6.All fittings and pipe joints, particularly fittings in the side of the pool or spa, should be properly sealed to prevent water from leaking into the adjacent soils materials, and be fitted with slip or expandible joints between connections transecting varying soil conditions. 7.An elastic expansion joint (elastomeric grout) should be installed to prevent water from seeping into the soil at all deck joints. If the decking consists of wood or brick pavers, then this recommendation is not warranted. A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 35 GeoSoils, Inc. 8.A reinforced grade beam should be placed around skimmer inlets to provide support and mitigate cracking around the skimmer face. 9.In order to reduce unsightly cracking, concrete deck slabs should be a minimum of 4 inches thick, and be reinforced with No. 3 steel reinforcing bars placed at 18 inches on-center and arranged in two perpendicular directions. All slab reinforcement should be supported on chairs to ensure proper mid-slab positioning during the placement of concrete. Wire mesh reinforcing is specifically not recommended. Deck slabs should not be tied to the pool/spa structure. Pre-moistening or pre-soaking of the slab subgrade to the soil’s optimum moisture content is recommended, to a depth of 12 inches for soils that are very low in expansion potential. This moisture content should be maintained in the subgrade soils during concrete placement to promote uniform curing of the concrete and to reduce the development of unsightly shrinkage cracks. Slab underlayment should consist of a 1- to 2-inch leveling course of sand (S.E. > 30) and a minimum of 4 to 6 inches of Class 2 aggregate base compacted to 90 percent of the laboratory standard (per ASTM D 1557). 10.Pool/spa structures should be founded entirely into suitable dense old paralic deposits. Compacted fill/old paralic deposit contacts beneath the pool/spa should be avoided. 11.In order to reduce unsightly slab cracking, the outer edges of the pool/spa decking, to be bordered by landscaping, and the edges immediately adjacent to the pool/spa should be underlain by an 8-inch wide concrete cut-off wall (thickened edge) extending to a depth of at least 12 inches below the bottoms of the slabs to mitigate excessive infiltration of water under the pool/spa deck. These thickened edges should be reinforced with two No. 4 steel reinforcing bars, one placed at the top and one placed at the bottom of the wall. 12.Surface and shrinkage cracking of the finished deck slab may be reduced if a low slump and water-cement ratio are maintained during concrete placement. Concrete used should have a minimum compressive strength of 4,000 pounds per square inch (psi). Excessive water added to concrete prior to placement is likely to cause shrinkage cracking, and should be avoided. Some concrete shrinkage cracking, however, is unavoidable. 13.Joint and sawcut locations for any pool/spa concrete deck should be determined by the design engineer and contractor. However, spacings should not exceed 6 feet on-center. 14.Temporary slopes created during excavations for pool/spa construction should adhere to the recommendations in the “Temporary Slopes” section of this report. All excavations should be observed by a representative of the geotechnical A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 36 GeoSoils, Inc. consultant, including the project geologist or engineer, prior to workers entering the excavation or trench, and minimally conform to CAL/OSHA, state, and local safety codes. Should adverse conditions exist, appropriate recommendations should be offered at that time by the geotechnical consultant. GSI does not consult in the area of safety engineering and the safety of the construction crew is the responsibility of the pool/spa builder. 15.It is imperative that adequate provisions for surface drainage are incorporated and maintained by the property owner into their overall improvement scheme. The ponding of water, ground saturation, and flow over slope faces are all situations which must be avoided to enhance the long-term performance of the pool/spa and associated improvements, and to reduce the likelihood of distress. 16.Regardless of the methods employed, once the pool/spa is filled with water, should it be emptied, there exists some potential significant distress to occur. Accordingly, once filled, the pool/spa should not be emptied unless evaluated by the pool/spa designer. 17.The temperature of the water lines for spas and pools may affect the corrosion properties of the site soils. Thus, a corrosion specialist should be retained to review all spa and pool plans, and provide mitigative recommendations, as warranted. Concrete mix design should be reviewed by a qualified corrosion consultant and materials engineer. 18.All backfill placed within pool/spa underground utility trenches should be uniformly moisture conditioned to at least the soil’s optimum moisture content and be compacted to a minimum relative density of 90 percent of the laboratory standard (per ASTM D 1557), under the full-time observation and testing of a qualified geotechnical consultant. Underground utility trench bottoms should be sloped away from the primary structures on the property (i.e., the proposed single-family residence and ADU). 19.Pool and spa underground utility lines should not cross those associated with the proposed single-family residence and ADU (i.e., not stacked, or sharing of trenches, etc.). 20.The pool/spa or associated underground utilities should not intercept, interrupt, or otherwise adversely impact any area drain, roof drain, or other drainage conveyances. If it is necessary to modify, move, or disrupt the existing retaining wall subdrain or associated tightlines, then the design civil engineer should be consulted for mitigative measures. Such measures should be further reviewed and approved by the geotechnical consultant, prior to proceeding with any further construction. A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 37 GeoSoils, Inc. 21.The geotechnical consultant should review and approve all aspects of pool/spa and flatwork design prior to construction. A design civil engineer should review all aspects of such design, including drainage and setback conditions. Prior to acceptance of the pool/spa construction, the project builder, geotechnical consultant and civil designer should evaluate the performance of the area drains and other site drainage pipes, following pool/spa construction. 22.Any changes in the design or location of the pool/spa should be reviewed and approved by the geotechnical consultant and design civil engineer prior to construction. Field adjustments should not be allowed until written approval of the proposed field changes are obtained from the geotechnical consultant and design civil engineer. 23.Failure to adhere to the above recommendations will significantly increase the potential for distress to the pool/spa, flatwork, etc. 24.Local seismicity or the design earthquake will cause some distress to the pool/spa and decking or flatwork, possibly including total functional and economic loss. The pool/spa designer may consider the incorporation of the seismic increment (19H), recommended herein, into the structural engineering. 25.The information and recommendations discussed above should be provided to any contractors and subcontractors, or homeowners, interested/affected parties, etc., that may perform or may be affected by such work. PORTLAND CEMENT CONCRETE (PCC) DRIVEWAYS, PEDESTRIAN PAVEMENTS, AND OTHER IMPROVEMENTS To reduce the likelihood of distress, the following recommendations are presented for all exterior PCC surface improvements (i.e., driveways, walkways, patios) and other exterior improvements: 1.Remedial grading should be performed in accordance with the recommendation previously provided in this report. 2.The design and construction of the pool/spa deck should follow the recommendations in the preceding section. 3.Within 72 hours of concrete placement, the subgrade area for exterior concrete slabs-on-grade to receive pedestrian traffic should be brought to at least the soil’s optimum moisture content and compacted to achieve a minimum 90 percent relative compaction (per ASTM D 1557). The subgrade for exterior PCC slabs-on-grade that will receive vehicular traffic should be compacted to achieve a A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 38 GeoSoils, Inc. minimum 95 percent relative compaction (per ASTM D 1557). The subgrade preparation should be observed and tested by GSI. 4.Exterior concrete slabs-on-grade should be cast over a relatively non-yielding surface, consisting of a 4-inch layer of crushed rock, gravel, or clean sand, that should be compacted and level prior to placing concrete. The layer should moisturized completely, prior to placing concrete, to reduce the loss of concrete moisture to the surrounding earth materials. 5.Exterior concrete slabs-on-grade should be a minimum of 4 inches thick. PCC slabs-on-grade that will receive vehicular traffic should have a thickened edge (at least 6 inches wide and extending a minimum of 12 inches below the pavement subgrade), where located adjacent to landscape areas. The purpose of the thickened edge is to help impede infiltration of landscape water under the slab. 6.The use of transverse and longitudinal control joints are recommended to help control slab cracking due to concrete shrinkage or expansion. Two ways to mitigate such cracking are: a) add a sufficient amount of reinforcing steel, increasing tensile strength of the slab; and, b) provide an adequate amount of control or expansion joints to accommodate anticipated concrete shrinkage and expansion. In order to reduce the potential for unsightly cracks, exterior concrete slabs-on- grade should be reinforced at mid-height with a minimum of No. 3 steel reinforcing bars placed at 18 inches on center, in each direction. The exterior concrete slabs should be scored or saw cut, ½ to d inches deep, often enough so that no section is greater than 10 feet by 10 feet. For sidewalks or narrow slabs, control joints should be provided at intervals of every 6 feet. The building foundations and exterior concrete slabs should be separated with expansion joint filler material. In areas directly adjacent to a continuous source of moisture (i.e., irrigation, planters, etc.), all joints should be additionally sealed with flexible mastic. 7.No traffic should be allowed upon the newly placed concrete slabs until they have been properly cured to within 75 percent of design strength. Concrete compressive strength should be a minimum of 2,500 psi. 8.Planters and walls should not be structurally tied to the proposed buildings. 9.Overhang structures should be supported on the exterior PCC slabs-on-grade or structurally designed with continuous or isolated footings tied to the perimeter foundation of the buildings. 10.Any masonry landscape walls that are to be constructed throughout the property should be supported by continuous footings with a minimum width of 12 inches that A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 39 GeoSoils, Inc. extend at least 12 inches into tested and approved compacted fill overlying suitable dense old paralic deposits or into suitable, dense old paralic deposits. The walls should be grouted and articulated in segments no more than 20 feet long. These segments should be keyed or doweled together. 11.Positive site drainage should be maintained at all times. In general, site drainage should conform to Section 1804.4 of the 2019 CBC. Drainage reversals could occur, including post-construction settlement, if relatively flat drainage gradients are not periodically maintained by the property owner. 12.Air conditioning (A/C) units should be supported by slabs that are incorporated into the building foundations or constructed on a rigid slab with flexible couplings for plumbing and electrical lines. A/C waste water lines should be drained to a suitable non-erosive outlet. 13.Shrinkage cracks could become excessive if proper finishing and curing practices are not followed. Finishing and curing practices should be performed per the Portland Cement Association Guidelines. Mix design should incorporate rate of curing for climate and time of year, sulfate content of soils, corrosion potential of soils, and fertilizers used on site. DEVELOPMENT CRITERIA Surface Drainage Adequate surface drainage is a very important factor in reducing the likelihood of adverse performance of foundations and pavements. Surface drainage should be sufficient to prevent ponding of water anywhere on the property, and especially near structures and pavements. Surface drainage should be carefully taken into consideration during landscaping so that future landscaping or construction activities do not create adverse drainage conditions. Water should be directed away from foundations and pavements, and not allowed to pond or seep into the ground. Consideration should be given to avoiding construction of open-bottom planters within 10 horizontal feet from the proposed buildings. As an alternative, closed-bottom type planters could be used. An outlet placed in the bottom of the planter, could be installed to direct drainage away from the buildings or any exterior concrete flatwork. If planters are constructed adjacent to the buildings, the sides and bottom of the planter should be provided with a moisture retarder to prevent penetration of irrigation water into the subgrade. Provisions should be made to drain the excess irrigation water from the planters without saturating the subgrade below or adjacent to the planters. Planters should not be structurally connected to the buildings. Site drainage should be directed toward James Drive or other approved drainage facilities. Areas of seepage may develop due to irrigation or heavy rainfall, and should be A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 40 GeoSoils, Inc. anticipated. Minimizing irrigation will lessen this potential. If areas of seepage develop, recommendations for reducing this effect could be provided upon request. Planting Water has been shown to weaken the inherent strength of all earth materials. Only the amount of irrigation necessary to sustain plant life should be provided. Over-watering should be avoided as it can adversely affect site improvements, and cause perched groundwater conditions. Plants selected for landscaping should be lightweight, deep rooted types that require little water and are capable of surviving the prevailing climate. Using plants other than those recommended above will increase the potential for perched water, staining, mold, etc., to develop. A rodent control program to prevent burrowing should be implemented. These recommendations regarding plant type, irrigation practices, and rodent control should be provided to all interested/affected parties. Landscape Maintenance Consideration should be given to the type of vegetation chosen and its potential effect upon surface improvements (i.e., some trees will have an effect on foundations, slab-on- grade floors, and pavements with their extensive root systems). From a geotechnical standpoint leaching is not recommended for establishing landscaping. If the surface soils are processed for the purpose of adding amendments, they should be recompacted to 90 percent minimum relative compaction. Gutters and Downspouts The installation of gutters and downspouts should be considered to collect roof water that may otherwise infiltrate the soils adjacent to the buildings. If used, the downspouts should be drained into PVC collector pipes or other non-erosive devices (e.g., paved swales or ditches; below grade, solid tight-lined PVC pipes; etc.), that will carry the water away from the house, to an appropriate outlet, in accordance with the recommendations of the design civil engineer. Downspouts and gutters are not a requirement; however, from a geotechnical viewpoint, provided that positive drainage is incorporated into project design (as discussed previously). Site Improvements If any additional improvements are planned for the site, recommendations concerning the geological or geotechnical aspects of design and construction of said improvements are recommended to be provided at that time. This office should be notified in advance of any fill placement, grading of the site, or trench backfilling after rough grading has been completed. This includes any grading and underground utility trench, and retaining wall backfills. A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 41 GeoSoils, Inc. Any proposed improvement constructed upon or within the influence of potentially compressible earth materials (i.e., undocumented fill, colluvium [topsoil], weathered old paralic deposits, etc.) may experience distress as a result of settlement. This potential should be disclosed to all interested/affected parties. Recommendations are provided in this report to reduce this potential. Foundation Excavations All foundation excavations should be observed by a representative of the geotechnical consultant subsequent to trenching and prior to the placement of concrete form work, steel reinforcement, and concrete. The purpose of the observations is to evaluate that the excavations are made into the recommended bearing material and to the minimum widths and depths recommended for construction. If loose or compressible earth materials are exposed within the foundation excavation, a deeper footing would be recommended at that time. Footing trench spoil and any excess soils generated from underground utility trenches should be compacted to a minimum relative compaction of 90 percent, if not removed from the site. Trenching Considering the nature of the onsite soils, it should be anticipated that caving or sloughing could be a factor in subsurface excavations and trenching. Shoring or excavating the trench walls at the angle of repose (typically 25 to 45 degrees) may be necessary and should be anticipated. All excavations should be observed by a licensed engineering geologist or engineer and minimally conform to local safety codes and CAL/OSHA guidelines for Type “B” soils conditions, provided that groundwater, running sands, or other adverse conditions are absent. Underground Utility Trench Backfill 1.All underground utility trench backfill should be brought to at least the soil’s optimum moisture content and then compacted to obtain a minimum relative compaction of 90 percent of the laboratory standard (per ASTM D 1557). Observation, probing, and field density testing should be provided to verify the desired results. 2.Exterior trenches adjacent to, and within, areas extending below a 1:1 (h:v) plane projected down and away from the outside bottom edge of the footing, and all trenches beneath hardscape features should be compacted to at least 90 percent of the laboratory standard. Sand backfill, unless excavated from the trench, should not be used in these backfill areas. Compaction testing and observations, along with tactile probing, should be accomplished to verify the desired results. 3.Underground utilities crossing grade beams, perimeter beams, or footings should either pass below the footing or grade beam using a hardened collar or foam A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 42 GeoSoils, Inc. spacer, or pass through the footing or grade beam in accordance with the recommendations of the structural engineer. SUMMARY OF RECOMMENDATIONS REGARDING GEOTECHNICAL OBSERVATION AND TESTING We recommend that geotechnical observation and testing be performed by GSI at each of the following construction stages: •During significant excavation (i.e., greater than 4 feet). •During remedial excavation and the placement of compacted fills. •After the excavation of the building, retaining wall, and pool/spa foundations, prior to the placement of reinforcing steel or concrete. •After the excavation of the pool/spa, prior to the placement of reinforcing steel or concrete. •During compaction of the subgrade and any base layer for pool/spa decking and surface improvements. •During placement of backfill for area drain, interior plumbing, and underground utility line trenches. •After the construction of retaining wall subdrains, prior to the placement of the retaining wall backfill. •During the placement of retaining wall backfill. •When any unusual soil conditions are encountered during any construction operations, subsequent to the issuance of this report. •A report of geotechnical observation and testing should be provided at the conclusion of each of the above stages, in order to provide concise and clear documentation of site work, and to comply with code requirements. OTHER DESIGN PROFESSIONALS/CONSULTANTS The design civil engineer, structural engineer, architect, landscape architect, wall designer, etc., should review the recommendations provided herein, incorporate those recommendations into all their respective plans, and by explicit reference, make this report A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 43 GeoSoils, Inc. part of their project plans. This report presents minimum design criteria for the design of slabs, foundations and other elements possibly applicable to the project. These criteria should not be considered as substitutes for actual designs by the structural engineer/designer. The structural engineer/designer should analyze actual soil-structure interaction and consider, as needed, bearing, expansive soil influence, and strength, stiffness and deflections in the various slab, foundation, and other elements in order to develop appropriate, design-specific details. As conditions dictate, it is possible that other influences will also have to be considered. The structural engineer/designer should consider all applicable codes and authoritative sources where needed. If analyses by the structural engineer/designer result in less critical details than are provided herein as minimums, the minimums presented herein should be adopted. It is considered likely that some, more restrictive details will be required. If the structural engineer/designer has any questions or requires further assistance, they should not hesitate to call or otherwise transmit their requests to GSI. In order to mitigate potential distress, the foundation or improvement’s designer should confirm to GSI and the governing agency, in writing, that the proposed foundations or improvements can tolerate the amount of differential settlement and expansion characteristics and design criteria specified herein. PLAN REVIEW Final project plans should be reviewed by this office prior to construction, so that construction is in accordance with the conclusions and recommendations of this report. Based on our review, supplemental recommendations or further geotechnical studies may be warranted. A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 44 GeoSoils, Inc. LIMITATIONS The materials encountered on the project site and used for our analysis are believed representative of the area; however, soil and bedrock materials vary in character between excavations and natural outcrops or conditions exposed during mass grading. Site conditions may vary due to seasonal changes or other factors. Inasmuch as our study is based upon our review, engineering analyses, and laboratory data, the conclusions and recommendations presented herein are professional opinions. These opinions have been derived in accordance with current standards of practice, and no warranty is express or implied. Standards of practice are subject to change with time. This report has been prepared for the purpose of providing soil design parameters derived from testing of a soil sample received at our laboratory, and does not represent an evaluation of the overall stability, suitability, or performance of the property for the proposed development. GSI assumes no responsibility or liability for work or testing performed by others, or their inaction; or work performed when GSI is not requested to be onsite, to evaluate if our recommendations have been properly implemented. Use of this report constitutes an agreement and consent by the user to all the limitations outlined above, notwithstanding any other agreements that may be in place. In addition, this report may be subject to review by the controlling authorities. Thus, this report brings to completion our scope of services for this portion of the project. A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 45 GeoSoils, Inc. The opportunity to be of service is sincerely appreciated. If you should have any questions, please do not hesitate to contact our office. Respectfully submitted, GeoSoils, Inc. John P. Franklin Stephen J. Coover Engineering Geologist, CEG 1340 Geotechnical Engineer, GE 2057 Ryan B. Boehmer Staff Geologist RBB/SJC/JPF/sh Attachments:Appendix A - References Appendix B - Test Pit Logs Appendix C- Seismicity Appendix D - Laboratory Test Results Appendix E - General Earthwork and Grading Guidelines Distribution:(3) Addressee (2 wet signed/stamped copies, 1 copy, and PDF via email) A.C. Mattos, Inc.W.O. 8320-A-SC 2780 James Drive, Carlsbad June 6, 2022 File:e:\wp21\8300\8320a.gep Page 46 GeoSoils, Inc. APPENDIX A REFERENCES GeoSoils, Inc. APPENDIX A REFERENCES American Concrete Institute, 2015 Guide for concrete floor and slab construction, ACI 302.1R-15, reported by ACI Committee 302. dated June. _____, 2014, Building code requirements for structural concrete (ACI 318-14), and commentary (ACI 318R-14): reported by ACI Committee 318, dated September. American Society of Civil Engineers, 2017, Minimum design loads and associated criteria for buildings and other structures, provisions, ASCE Standard ASCE/SEI 7-16. Blake, Thomas F., 2000a, EQFAULT, A computer program for the estimation of peak horizontal acceleration from 3-D fault sources; Windows 95/98 version. _____, 2000b, EQSEARCH, A computer program for the estimation of peak horizontal acceleration from California historical earthquake catalogs; Updated to May 8, 2021, Windows 95/98 version. Bozorgnia, Y., Campbell K.W., and Niazi, M., 1999, Vertical ground motion: Characteristics, relationship with horizontal component, and building-code implications; Proceedings of the SMIP99 seminar on utilization of strong-motion data, September 15, Oakland, pp. 23-49. California Building Standards Commission, 2019, California Building Code, California Code of Regulations, Title 24, Part 2, Volumes 1 and 2, based on the 2018 International Building Code. California Department of Conservation, California Geological Survey (CGS), 2018, Earthquake fault zones, a guide for government agencies, property owners/developers, and geoscience practitioners for assessing fault rupture hazards in California: California Geological Survey Special Publication 42 (revised 2018), 93 p. Cao, T., Bryant, W.A., Rowshandel, B., Branum, D., and Wills, C.J., 2003, The revised 2002 California pro ba bi l is tic s eismi c hazar d ma ps, dated June, http://www.conservation.ca.gov/cgs/rghm/psha/fault_parameters/pdf/Documents /2002_CA_Hazard_Maps.pdf. City of Los Angeles Department of Building and Safety, 2020, Information bulletin / public - building code, reference no.: LABC 1610.1, 1807.2, document no.: P/BC 2020-083, dated January 1. Coast Geotechnical, 2004, Rough grading report, proposed five (5) lot subdivision, portion of Lots 3 and 4, Map 2169, Carlsbad Tract 98-16, Buena Vista Way, Carlsbad, California, W.O. G-304099, dated January 7. GeoSoils, Inc. Jennings, C.W., and Bryant, W.A., 2010, Fault activity map of California, scale 1:750,000, California Geological Survey, Geologic Data Map No. 6. Kanare, H.M., 2005, Concrete floors and moisture, Engineering Bulletin 119, Portland Cement Association. Kennedy, M.P., and Tan, SS., 2007, Geologic map of the Oceanside 30' by 60' quadrangle, Cal ifornia, regional map series, sca le 1:100,000, California Ge ol og ic S u r v e y an d U nited S t a t e s G e o l o gi c a l Su rv e y , www.conservation.ca.gov/cgs/rghm/rgm/preliminary_geologic_maps.html Land Space Engineering, 2002, Grading and erosion control plans for: Carlsbad Tract 98- 16, sheet 3 of 4, 50-scale, project no.: CT 98-16, drawing no.: 382-9A, dated November 5. Leighton and Associates, Inc., 1992, City of Carlsbad geotechnical hazards analysis and mapping study, Carlsbad, California, 115 sheets, 1:4,800-scale, dated November. Park Aerial Surveys, Inc., 1953, Stereoscopic aerial photographs, flight: AXN-1953, frame nos. 14M-19 and 14M-20, 1:20,000-scale, dated May 2. Seed, 2005, Evaluation and mitigation of soil liquefaction hazard “evaluation of field data and procedures for evaluating the risk of triggering (or inception) of liquefaction”, in Geotechnical earthquake engineering; short course, San Diego, California, April 8-9. Seed, H. B. and Whitman, R. V., 1970, Design of earth retaining structures for dynamic loads, ASCE Specialty Conference, Lateral Stresses in the Ground and Design of Earth Retaining Structures, pp. 103-147. Sowers and Sowers, 1979, Unified soil classification system (After U. S. Waterways Experiment Station and ASTM 02487-667) in Introductory soil mechanics, New York. State of California, 2022, Civil Code, Sections 896 et seq. Tan, S.S., and Giffen, D.G., 1995, Landslide hazards in the northern part of the San Diego Metropolitan area, San Diego County, California, Landslide hazard identification map no. 35, Plate 35A, Department of Conservation, Division of Mines and Geology, DMG Open File Report 95-04. Weber, F.H., 1982, Recent slope failures, ancient landslides, and related geology of the north-central coastal area, San Diego County, California, California Department of Conservation, Division of Mines and Geology Open-File Report 82-12 LA. A.C. Mattos, Inc.Appendix A File:e:\wp21\8300\8320a.gep Page 2 GeoSoils, Inc. APPENDIX B TEST PIT LOGS UNIFIED SOIL CLASSIFICATION SYSTEM CONSISTENCY OR RELATIVE DENSITY Major Divisions Group Symbols Typical Names CRITERIA Co a r s e - G r a i n e d S o i l s Mo r e t h a n 5 0 % r e t a i n e d o n N o . 2 0 0 s i e v e Gr a v e l s 50 % o r m o r e o f co a r s e f r a c t i o n re t a i n e d o n N o . 4 s i e v e Cl e a n Gr a v e l s GW Well-graded gravels and gravel-sand mixtures, little or no fines Standard Penetration Test Penetration Resistance N Relative (blows/ft) Density 0 - 4 Very loose 4 - 10 Loose 10 - 30 Medium 30 - 50 Dense > 50 Very dense GP Poorly graded gravels and gravel-sand mixtures, little or no fines Gr a v e l wi t h GM Silty gravels gravel-sand-silt mixtures GC Clayey gravels, gravel-sand-clay mixtures Sa n d s mo r e t h a n 5 0 % o f co a r s e f r a c t i o n pa s s e s N o . 4 s i e v e Cle a n Sa n d s SW Well-graded sands and gravelly sands, little or no fines SP Poorly graded sands andgravelly sands, little or no fines Sa n d s wi t h Fi n e s SM Silty sands, sand-silt mixtures SC Clayey sands, sand-clay mixtures Fi n e - G r a i n e d S o i l s 50 % o r m o r e p a s s e s N o . 2 0 0 s i e v e Sil t s a n d C l a y s Liq u i d l i m i t 50 % o r l e s s ML Inorganic silts, very fine sands,rock flour, silty or clayey finesands Standard Penetration Test Unconfined Penetration Compressive Resistance N Strength (blows/ft) Consistency (tons/ft 2) <2 Very Soft <0.25 2 - 4 Soft 0.25 - .050 4 - 8 Medium 0.50 - 1.00 8 - 15 Stiff 1.00 - 2.00 15 - 30 Very Stiff 2.00 - 4.00 >30 Hard >4.00 CL Inorganic clays of low to medium plasticity, gravelly clays, sandy clays, silty clays, lean clays OL Organic silts and organic silty clays of low plasticity Si l t s a n d C l a y s Li q u i d l i m i t gr e a t e r t h a n 5 0 % MH Inorganic silts, micaceous or diatomaceous fine sands or silts, elastic silts CH Inorganic clays of high plasticity, fat clays OH Organic clays of medium to high plasticity Highly Organic Soils PT Peat, mucic, and other highly organic soils 3" 3/4" #4 #10 #40 #200 U.S. Standard Sieve Unified Soil Classification Cobbles Gravel Sand Silt or Clay coarse fine coarse medium fine MOISTURE CONDITIONS MATERIAL QUANTITY OTHER SYMBOLS Dry Absence of moisture: dusty, dry to the touch trace 0 - 5 % C Core Sample Slightly Moist Below optimum moisture content for compaction few 5 - 10 % S SPT Sample Moist Near optimum moisture content little 10 - 25 % B Bulk Sample Very Moist Above optimum moisture content some 25 - 45 % – Groundwater Wet Visible free water; below water table Qp Pocket Penetrometer BASIC LOG FORMAT: Group name, Group symbol, (grain size), color, moisture, consistency or relative density. Additional comments: odor, presence of roots, mica, gypsum, coarse grained particles, etc. EXAMPLE: Sand (SP), fine to medium grained, brown, moist, loose, trace silt, little fine gravel, few cobbles up to 4" in size, some hair roots and rootlets. File:Mgr: c;\SoilClassif.wpd PLATE B-1 W.O. 8320-A-SC A.C. Mattos, Inc. 2780 James Drive, Carlsbad Logged By: RBB April 11, 2022 LOG OF EXPLORATORY TEST PIT TEST PIT NO. ELEV. (ft.) DEPTH (ft.) GROUP SYMBOL SAMPLE DEPTH (ft.) MOISTURE (%) FIELD DRY DENSITY (pcf) DESCRIPTION TP-1 ~160 0-5¼SP/SM UND @ 2 UND @ 4¾ BULK @ 0-5¼ 5.2 7.0 132.6 118.6 ARTIFICIAL FILL - COMPACTED: SAND and SILTY SAND, variegated light brown, dark grayish brown, and reddish yellow, dry becoming moist at approximately 2 feet and becoming damp at approximately 4¾ feet, loose becoming dense at approximately 1 foot; trace angular and subrounded gravels, trace metal, glass, and asphaltic concrete fragments. 5¼-10 SC BULK @ 5¼-10 4.4 QUATERNARY OLD PARALIC DEPOSITS: CLAYEY SAND, reddish yellow, moist, dense:, very fine to fine grained, abundant iron-stone concretions. 10-11 SM SILTY SAND, dark brown, moist, dense; fine to medium grained. UND= Relatively Undisturbed Sample BULK = Representative Bulk Soil Sample Total Depth = 11’ No Groundwater or Caving Encountered Backfilled 4-11-22 PLATE B-2 W.O. 8320-A-SC A.C. Mattos, Inc. 2780 James Drive, Carlsbad Logged By: RBB April 11, 2022 LOG OF EXPLORATORY TEST PIT TEST PIT NO. ELEV. (ft.) DEPTH (ft.) GROUP SYMBOL SAMPLE DEPTH (ft.) MOISTURE (%) FIELD DRY DENSITY (pcf) DESCRIPTION TP-2 ~160 0-4½SM ARTIFICIAL FILL - COMPACTED: SILTY SAND, variegated dark yellowish brown, grayish brown, and reddish yellow, dry becoming damp at approximately 1 foot, loose becoming dense at approximately 1 foot; trace clay. 4½-5¾SC UND @ 5¼9.2 119.8 QUATERNARY OLD PARALIC DEPOSITS: CLAYEY SAND, reddish brown, moist, dense:, very fine to fine grained, trace iron-stone concretions. UND= Relatively Undisturbed Sample Total Depth = 5¾’ No Groundwater or Caving Encountered Backfilled 4-11-22 PLATE B-3 W.O. 8320-A-SC A.C. Mattos, Inc. 2780 James Drive, Carlsbad Logged By: RBB April 11, 2022 LOG OF EXPLORATORY TEST PIT TEST PIT NO. ELEV. (ft.) DEPTH (ft.) GROUP SYMBOL SAMPLE DEPTH (ft.) MOISTURE (%) FIELD DRY DENSITY (pcf) DESCRIPTION TP-3 ~160 0-1 SC ARTIFICIAL FILL - COMPACTED: CLAYEY SAND, brownish gray, dry, loose; trace angular gravels. 1-4½SM UND @ 3 8.4 128.8 SILTY SAND, variegated dark grayish brown and reddish yellow, moist to wet, dense; trace angular gravels. 4½-5 SM QUATERNARY OLD PARALIC DEPOSITS: SILTY SAND, brownish gray, moist, dense:, very fine to fine grained, trace clay, trace iron- stone concretions. 5-6½SC UND @ 6 BULK @ 5-6 12.0 10.0 116.7 CLAYEY SAND, brown, wet, dense; very fine to fine grained, trace iron-stone concretions, slightly porous. UND= Relatively Undisturbed Sample BULK = Representative Bulk Soil Sample Total Depth = 6½’ No Groundwater or Caving Encountered Backfilled 4-11-22 PLATE B-4 W.O. 8320-A-SC A.C. Mattos, Inc. 2780 James Drive, Carlsbad Logged By: RBB April 11, 2022 LOG OF EXPLORATORY TEST PIT TEST PIT NO. ELEV. (ft.) DEPTH (ft.) GROUP SYMBOL SAMPLE DEPTH (ft.) MOISTURE (%) FIELD DRY DENSITY (pcf) DESCRIPTION TP-4 ~160 0-1¼SC ARTIFICIAL FILL - COMPACTED: CLAYEY SAND, brownish gray, dry, loose; trace angular gravels. 1¼-4 SM UND @ 2½5.0 127.6 SILTY SAND, variegated dark grayish brown and reddish yellow, damp, dense; trace angular gravels. 4-5 SC QUATERNARY OLD PARALIC DEPOSITS: CLAYEY SAND, brown, moist, dense; very fine to fine grained, abundant iron-stone concretions. UND= Relatively Undisturbed Sample Total Depth = 5’ No Groundwater or Caving Encountered Backfilled 4-11-22 PLATE B-5 W.O. 8320-A-SC A.C. Mattos, Inc. 2780 James Drive, Carlsbad Logged By: RBB April 11, 2022 LOG OF EXPLORATORY TEST PIT TEST PIT NO. ELEV. (ft.) DEPTH (ft.) GROUP SYMBOL SAMPLE DEPTH (ft.) MOISTURE (%) FIELD DRY DENSITY (pcf) DESCRIPTION TP-5 ~160 0-1 SM SM BAG @ 0-1 5.2 ARTIFICIAL FILL - COMPACTED: CLAYEY SAND, brownish gray, dry, loose; trace angular gravels. 1-4½SM BULK @ 2½-3 5.9 SILTY SAND, variegated dark grayish brown and reddish yellow, dry, dense; trace subangular and angular gravels, trace trash (plastic). 4½-5¼CL QUATERNARY OLD PARALIC DEPOSITS: CLAYEY SAND, brown, moist, dense; very fine to fine grained, trace iron-stone concretions. SM BAG = SM BAG SAMPLE BULK = Representative Bulk Soil Sample Total Depth = 5¼’ No Groundwater or Caving Encountered Backfilled 4-11-22 PLATE B-6 GeoSoils, Inc. APPENDIX C SEISMICITY *********************** * * * E Q F A U L T * * * * Version 3.00 * * * *********************** DETERMINISTIC ESTIMATION OF PEAK ACCELERATION FROM DIGITIZED FAULTS JOB NUMBER: 8320-A-SC DATE: 04-09-2022 JOB NAME: A.C. MATTOS, INC. CALCULATION NAME: 8320 FAULT-DATA-FILE NAME: C:\Users\Ryan\Documents\EQFAULT1\CGSFLTE.DAT SITE COORDINATES: SITE LATITUDE: 33.1698 SITE LONGITUDE: 117.3377 SEARCH RADIUS: 62.2 mi ATTENUATION RELATION: 11) Bozorgnia Campbell Niazi (1999) Hor.-Pleist. Soil-Cor. UNCERTAINTY (M=Median, S=Sigma): S Number of Sigmas: 1.0 DISTANCE MEASURE: cdist SCOND: 0 Basement Depth: 5.00 km Campbell SSR: 0 Campbell SHR: 0 COMPUTE PEAK HORIZONTAL ACCELERATION FAULT-DATA FILE USED: C:\Users\Ryan\Documents\EQFAULT1\CGSFLTE.DAT MINIMUM DEPTH VALUE (km): 3.0 W.O. 8320-A-SC PLATE C-1 --------------- EQFAULT SUMMARY --------------- ----------------------------- DETERMINISTIC SITE PARAMETERS ----------------------------- Page 1 ------------------------------------------------------------------------------- | |ESTIMATED MAX. EARTHQUAKE EVENT | APPROXIMATE |------------------------------- ABBREVIATED | DISTANCE | MAXIMUM | PEAK |EST. SITE FAULT NAME | mi (km) |EARTHQUAKE| SITE |INTENSITY | | MAG.(Mw) | ACCEL. g |MOD.MERC. ================================|==============|==========|==========|========= NEWPORT-INGLEWOOD (Offshore) | 5.7( 9.2)| 7.1 | 0.573 | X ROSE CANYON | 6.2( 10.0)| 7.2 | 0.567 | X CORONADO BANK | 21.9( 35.2)| 7.6 | 0.264 | IX ELSINORE (TEMECULA) | 23.4( 37.6)| 6.8 | 0.145 | VIII ELSINORE (JULIAN) | 23.7( 38.1)| 7.1 | 0.175 | VIII ELSINORE (GLEN IVY) | 32.7( 52.7)| 6.8 | 0.102 | VII SAN JOAQUIN HILLS | 34.7( 55.9)| 6.6 | 0.119 | VII PALOS VERDES | 35.7( 57.5)| 7.3 | 0.132 | VIII EARTHQUAKE VALLEY | 43.8( 70.5)| 6.5 | 0.062 | VI NEWPORT-INGLEWOOD (L.A.Basin) | 45.4( 73.1)| 7.1 | 0.089 | VII SAN JACINTO-ANZA | 45.9( 73.9)| 7.2 | 0.095 | VII SAN JACINTO-SAN JACINTO VALLEY | 46.4( 74.6)| 6.9 | 0.076 | VII CHINO-CENTRAL AVE. (Elsinore) | 46.9( 75.5)| 6.7 | 0.092 | VII WHITTIER | 50.8( 81.7)| 6.8 | 0.064 | VI SAN JACINTO-COYOTE CREEK | 51.9( 83.6)| 6.6 | 0.055 | VI ELSINORE (COYOTE MOUNTAIN) | 58.2( 93.7)| 6.8 | 0.056 | VI W.O. 8320-A-SC PLATE C-2 SAN JACINTO-SAN BERNARDINO | 58.8( 94.7)| 6.7 | 0.052 | VI PUENTE HILLS BLIND THRUST | 60.7( 97.7)| 7.1 | 0.093 | VII ******************************************************************************* -END OF SEARCH- 18 FAULTS FOUND WITHIN THE SPECIFIED SEARCH RADIUS. THE NEWPORT-INGLEWOOD (Offshore) FAULT IS CLOSEST TO THE SITE. IT IS ABOUT 5.7 MILES (9.2 km) AWAY. LARGEST MAXIMUM-EARTHQUAKE SITE ACCELERATION: 0.5726 g W.O. 8320-A-SC PLATE C-3 SITE -100 0 100 200 300 400 500 600 700 800 900 1000 1100 -400 -300 -200 -100 0 100 200 300 400 500 600 CALIFORNIA FAULT MAP A.C. MATTOS, INC. W.O. 8320-A-SC PLATE C-4 .001 .01 .1 1 .1 1 10 100 MAXIMUM EARTHQUAKES A.C. MATTOS, INC. Ac c e l e r a t i o n ( g ) Distance (mi) W.O. 8320-A-SC PLATE C-5 ************************* * * * E Q S E A R C H * * * * Version 3.00 * * * ************************* ESTIMATION OF PEAK ACCELERATION FROM CALIFORNIA EARTHQUAKE CATALOGS JOB NUMBER: 8320-A-SC DATE: 04-09-2022 JOB NAME: A.C. MATTOS, INC. EARTHQUAKE-CATALOG-FILE NAME: C:\Users\Ryan\Documents\EQSEARCH\ALLQUAKE-2021.DAT MAGNITUDE RANGE: MINIMUM MAGNITUDE: 5.00 MAXIMUM MAGNITUDE: 9.00 SITE COORDINATES: SITE LATITUDE: 33.1698 SITE LONGITUDE: 117.3377 SEARCH DATES: START DATE: 1800 END DATE: 2021 SEARCH RADIUS: 62.2 mi 100.1 km ATTENUATION RELATION: 11) Bozorgnia Campbell Niazi (1999) Hor.-Pleist. Soil-Cor. UNCERTAINTY (M=Median, S=Sigma): S Number of Sigmas: 1.0 ASSUMED SOURCE TYPE: SS [SS=Strike-slip, DS=Reverse-slip, BT=Blind-thrust] SCOND: 0 Depth Source: A Basement Depth: 5.00 km Campbell SSR: 0 Campbell SHR: 0 COMPUTE PEAK HORIZONTAL ACCELERATION MINIMUM DEPTH VALUE (km): 3.0 W.O. 8320-A-SC PLATE C-6 ------------------------- EARTHQUAKE SEARCH RESULTS ------------------------- Page 1 ------------------------------------------------------------------------------- | | | | TIME | | | SITE |SITE| APPROX. FILE| LAT. | LONG. | DATE | (UTC) |DEPTH|QUAKE| ACC. | MM | DISTANCE CODE| NORTH | WEST | | H M Sec| (km)| MAG.| g |INT.| mi [km] ----+-------+--------+----------+--------+-----+-----+-------+----+------------ DMG |33.0000|117.3000|11/22/1800|2130 0.0| 0.0| 6.50| 0.231 | IX | 11.9( 19.2) MGI |33.0000|117.0000|09/21/1856| 730 0.0| 0.0| 5.00| 0.048 | VI | 22.8( 36.7) MGI |32.8000|117.1000|05/25/1803| 0 0 0.0| 0.0| 5.00| 0.038 | V | 29.0( 46.7) DMG |32.7000|117.2000|05/27/1862|20 0 0.0| 0.0| 5.90| 0.056 | VI | 33.4( 53.7) PAS |32.9710|117.8700|07/13/1986|1347 8.2| 6.0| 5.30| 0.038 | V | 33.7( 54.3) T-A |32.6700|117.1700|12/00/1856| 0 0 0.0| 0.0| 5.00| 0.030 | V | 35.8( 57.7) T-A |32.6700|117.1700|10/21/1862| 0 0 0.0| 0.0| 5.00| 0.030 | V | 35.8( 57.7) T-A |32.6700|117.1700|05/24/1865| 0 0 0.0| 0.0| 5.00| 0.030 | V | 35.8( 57.7) DMG |33.7000|117.4000|05/15/1910|1547 0.0| 0.0| 6.00| 0.053 | VI | 36.8( 59.2) DMG |33.7000|117.4000|04/11/1910| 757 0.0| 0.0| 5.00| 0.029 | V | 36.8( 59.2) DMG |33.7000|117.4000|05/13/1910| 620 0.0| 0.0| 5.00| 0.029 | V | 36.8( 59.2) DMG |33.2000|116.7000|01/01/1920| 235 0.0| 0.0| 5.00| 0.029 | V | 36.9( 59.4) DMG |33.6990|117.5110|05/31/1938| 83455.4| 10.0| 5.50| 0.038 | V | 37.9( 60.9) DMG |32.8000|116.8000|10/23/1894|23 3 0.0| 0.0| 5.70| 0.040 | V | 40.3( 64.8) MGI |33.2000|116.6000|10/12/1920|1748 0.0| 0.0| 5.30| 0.030 | V | 42.7( 68.7) DMG |33.7100|116.9250|09/23/1963|144152.6| 16.5| 5.00| 0.024 | V | 44.2( 71.2) DMG |33.7500|117.0000|04/21/1918|223225.0| 0.0| 6.80| 0.074 | VII| 44.5( 71.7) W.O. 8320-A-SC PLATE C-7 DMG |33.7500|117.0000|06/06/1918|2232 0.0| 0.0| 5.00| 0.024 | V | 44.5( 71.7) MGI |33.8000|117.6000|04/22/1918|2115 0.0| 0.0| 5.00| 0.023 | IV | 46.1( 74.1) DMG |33.5750|117.9830|03/11/1933| 518 4.0| 0.0| 5.20| 0.026 | V | 46.5( 74.9) DMG |33.6170|117.9670|03/11/1933| 154 7.8| 0.0| 6.30| 0.049 | VI | 47.6( 76.7) DMG |33.8000|117.0000|12/25/1899|1225 0.0| 0.0| 6.40| 0.053 | VI | 47.7( 76.7) DMG |33.6170|118.0170|03/14/1933|19 150.0| 0.0| 5.10| 0.023 | IV | 49.9( 80.2) GSP |33.5290|116.5720|06/12/2005|154146.5| 14.0| 5.20| 0.024 | IV | 50.6( 81.5) DMG |33.9000|117.2000|12/19/1880| 0 0 0.0| 0.0| 6.00| 0.038 | V | 51.0( 82.1) GSG |33.4200|116.4890|07/07/2010|235333.5| 14.0| 5.50| 0.027 | V | 51.9( 83.6) PAS |33.5010|116.5130|02/25/1980|104738.5| 13.6| 5.50| 0.027 | V | 52.8( 84.9) GSP |33.5080|116.5140|10/31/2001|075616.6| 15.0| 5.10| 0.021 | IV | 52.9( 85.2) DMG |33.5000|116.5000|09/30/1916| 211 0.0| 0.0| 5.00| 0.020 | IV | 53.4( 86.0) DMG |33.0000|116.4330|06/04/1940|1035 8.3| 0.0| 5.10| 0.021 | IV | 53.6( 86.3) DMG |33.6830|118.0500|03/11/1933| 658 3.0| 0.0| 5.50| 0.026 | V | 54.2( 87.3) GSP |33.4315|116.4427|06/10/2016|080438.7| 12.3| 5.19| 0.022 | IV | 54.7( 88.0) DMG |33.7000|118.0670|03/11/1933| 51022.0| 0.0| 5.10| 0.020 | IV | 55.7( 89.7) DMG |33.7000|118.0670|03/11/1933| 85457.0| 0.0| 5.10| 0.020 | IV | 55.7( 89.7) DMG |34.0000|117.2500|07/23/1923| 73026.0| 0.0| 6.25| 0.039 | V | 57.5( 92.6) MGI |34.0000|117.5000|12/16/1858|10 0 0.0| 0.0| 7.00| 0.064 | VI | 58.1( 93.5) DMG |33.3430|116.3460|04/28/1969|232042.9| 20.0| 5.80| 0.029 | V | 58.5( 94.1) DMG |33.7500|118.0830|03/11/1933| 323 0.0| 0.0| 5.00| 0.018 | IV | 58.7( 94.5) DMG |33.7500|118.0830|03/11/1933| 910 0.0| 0.0| 5.10| 0.019 | IV | 58.7( 94.5) DMG |33.7500|118.0830|03/13/1933|131828.0| 0.0| 5.30| 0.021 | IV | 58.7( 94.5) DMG |33.7500|118.0830|03/11/1933| 2 9 0.0| 0.0| 5.00| 0.018 | IV | 58.7( 94.5) DMG |33.7500|118.0830|03/11/1933| 230 0.0| 0.0| 5.10| 0.019 | IV | 58.7( 94.5) GSG |33.9530|117.7610|07/29/2008|184215.7| 14.0| 5.30| 0.021 | IV | 59.3( 95.4) DMG |33.9500|116.8500|09/28/1946| 719 9.0| 0.0| 5.00| 0.017 | IV | 60.7( 97.7) DMG |33.4000|116.3000|02/09/1890|12 6 0.0| 0.0| 6.30| 0.037 | V | 62.0( 99.7) ******************************************************************************* -END OF SEARCH- 45 EARTHQUAKES FOUND WITHIN THE SPECIFIED SEARCH AREA. TIME PERIOD OF SEARCH: 1800 TO 2021 LENGTH OF SEARCH TIME: 222 years THE EARTHQUAKE CLOSEST TO THE SITE IS ABOUT 11.9 MILES (19.2 km) AWAY. LARGEST EARTHQUAKE MAGNITUDE FOUND IN THE SEARCH RADIUS: 7.0 LARGEST EARTHQUAKE SITE ACCELERATION FROM THIS SEARCH: 0.231 g W.O. 8320-A-SC PLATE C-8 COEFFICIENTS FOR GUTENBERG & RICHTER RECURRENCE RELATION: a-value= 0.924 b-value= 0.369 beta-value= 0.851 ------------------------------------ TABLE OF MAGNITUDES AND EXCEEDANCES: ------------------------------------ Earthquake | Number of Times | Cumulative Magnitude | Exceeded | No. / Year -----------+-----------------+------------ 4.0 | 45 | 0.20270 4.5 | 45 | 0.20270 5.0 | 45 | 0.20270 5.5 | 16 | 0.07207 6.0 | 9 | 0.04054 6.5 | 3 | 0.01351 7.0 | 1 | 0.00450 W.O. 8320-A-SC PLATE C-9 SITE LEGEND M = 4 M = 5 M = 6 M = 7 M = 8 -100 0 100 200 300 400 500 600 700 800 900 1000 1100 -400 -300 -200 -100 0 100 200 300 400 500 600 EARTHQUAKE EPICENTER MAP A.C. MATTOS, INC. W.O. 8320-A-SC PLATE C-10 .001 .01 .1 1 10 100 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 EARTHQUAKE RECURRENCE CURVE A.C. MATTOS, INC. Cu m m u l a t i v e N u m b e r o f E v e n t s ( N ) / Y e a r Magnitude (M) W.O. 8320-A-SC PLATE C-11 GeoSoils, Inc. APPENDIX D LABORATORY TEST RESULTS 7.3 96 Samples testing in accordance with:pH - CTM 643, Resistivity - CTM 643 Sulfate - CTM 417, Chloride - CTM 422 Remarks: Chloride Content (mg/kg) TP-1, 0-5.25ft 2600 0.004 Report Date:April 29, 2022 SAMPLE ID pH (H+) Minimum Resistivity (ohm/cm) Sulfate Content (wt%) 5741 Palmer Way, Carlsbad CA 92010 Phone (760) 438-3155 CORROSION REPORT SUMMARY Project No:8320-A-SC Project Name:A.C. Mattos, Inc W.O. 8320-A-SC PLATE D-1 GeoSoils, Inc. APPENDIX E GENERAL EARTHWORK AND GRADING GUIDELINES GeoSoils, Inc. GENERAL EARTHWORK AND GRADING GUIDELINES General These guidelines present general procedures and requirements for earthwork and grading as shown on the approved grading plans, including preparation of areas to be filled, placement of fill, installation of subdrains, excavations, and appurtenant structures or flatwork. The recommendations contained in the geotechnical report are part of these earthwork and grading guidelines and would supercede the provisions contained hereafter in the case of conflict. Evaluations performed by the consultant during the course of grading may result in new or revised recommendations which could supercede these guidelines or the recommendations contained in the geotechnical report. Generalized details follow this text. The contractor is responsible for the satisfactory completion of all earthwork in accordance with provisions of the project plans and specifications and latest adopted Code. In the case of conflict, the most onerous provisions shall prevail. The project geotechnical engineer and engineering geologist (geotechnical consultant), or their representatives, should provide observation and testing services, and geotechnical consultation during the duration of the project. EARTHWORK OBSERVATIONS AND TESTING Geotechnical Consultant Prior to the commencement of grading, a qualified geotechnical consultant (soil engineer and engineering geologist) should be employed for the purpose of observing earthwork procedures and testing the fills for general conformance with the recommendations of the geotechnical report(s), the approved grading plans, and applicable grading codes and ordinances. The geotechnical consultant should provide testing and observation so that an evaluation may be made that the work is being accomplished as specified. It is the responsibility of the contractor to assist the consultants and keep them apprised of anticipated work schedules and changes, so that they may schedule their personnel accordingly. All remedial removals, clean-outs, prepared ground to receive fill, key excavations, and subdrain installation should be observed and documented by the geotechnical consultant prior to placing any fill. It is the contractor’s responsibility to notify the geotechnical consultant when such areas are ready for observation. Laboratory and Field Tests Maximum dry density tests to determine the degree of compaction should be performed in accordance with American Standard Testing Materials test method ASTM designation D-1557. Random or representative field compaction tests should be performed in GeoSoils, Inc. accordance with test methods ASTM designation D-1556, D-2937 or D-2922, and D-3017, at intervals of approximately ±2 feet of fill height or approximately every 1,000 cubic yards placed. These criteria would vary depending on the soil conditions and the size of the project. The location and frequency of testing would be at the discretion of the geotechnical consultant. Contractor's Responsibility All clearing, site preparation, and earthwork performed on the project should be conducted by the contractor, with observation by a geotechnical consultant, and staged approval by the governing agencies, as applicable. It is the contractor's responsibility to prepare the ground surface to receive the fill, to the satisfaction of the geotechnical consultant, and to place, spread, moisture condition, mix, and compact the fill in accordance with the recommendations of the geotechnical consultant. The contractor should also remove all non-earth material considered unsatisfactory by the geotechnical consultant. Notwithstanding the services provided by the geotechnical consultant, it is the sole responsibility of the contractor to provide adequate equipment and methods to accomplish the earthwork in strict accordance with applicable grading guidelines, latest adopted Code or agency ordinances, geotechnical report(s), and approved grading plans. Sufficient watering apparatus and compaction equipment should be provided by the contractor with due consideration for the fill material, rate of placement, and climatic conditions. If, in the opinion of the geotechnical consultant, unsatisfactory conditions such as questionable weather, excessive oversized rock or deleterious material, insufficient support equipment, etc., are resulting in a quality of work that is not acceptable, the consultant will inform the contractor, and the contractor is expected to rectify the conditions, and if necessary, stop work until conditions are satisfactory. During construction, the contractor shall properly grade all surfaces to maintain good drainage and prevent ponding of water. The contractor shall take remedial measures to control surface water and to prevent erosion of graded areas until such time as permanent drainage and erosion control measures have been installed. SITE PREPARATION All major vegetation, including brush, trees, thick grasses, organic debris, and other deleterious material, should be removed and disposed of off-site. These removals must be concluded prior to placing fill. In-place existing fill, soil, alluvium, colluvium, or rock materials, as evaluated by the geotechnical consultant as being unsuitable, should be removed prior to any fill placement. Depending upon the soil conditions, these materials may be reused as compacted fills. Any materials incorporated as part of the compacted fills should be approved by the geotechnical consultant. Any underground structures such as cesspools, cisterns, mining shafts, tunnels, septic tanks, wells, pipelines, or other structures not located prior to grading, are to be removed A.C. Mattos, Inc.Appendix E File:e:\wp21\8300\8320a.gep Page 2 GeoSoils, Inc. or treated in a manner recommended by the geotechnical consultant. Soft, dry, spongy, highly fractured, or otherwise unsuitable ground, extending to such a depth that surface processing cannot adequately improve the condition, should be overexcavated down to firm ground and approved by the geotechnical consultant before compaction and filling operations continue. Overexcavated and processed soils, which have been properly mixed and moisture conditioned, should be re-compacted to the minimum relative compaction as specified in these guidelines. Existing ground, which is determined to be satisfactory for support of the fills, should be scarified (ripped) to a minimum depth of 6 to 8 inches, or as directed by the geotechnical consultant. After the scarified ground is brought to optimum moisture content, or greater and mixed, the materials should be compacted as specified herein. If the scarified zone is greater than 6 to 8 inches in depth, it may be necessary to remove the excess and place the material in lifts restricted to about 6 to 8 inches in compacted thickness. Existing ground which is not satisfactory to support compacted fill should be overexcavated as required in the geotechnical report, or by the on-site geotechnical consultant. Scarification, disc harrowing, or other acceptable forms of mixing should continue until the soils are broken down and free of large lumps or clods, until the working surface is reasonably uniform and free from ruts, hollows, hummocks, mounds, or other uneven features, which would inhibit compaction as described previously. Where fills are to be placed on ground with slopes steeper than 5:1 (horizontal to vertical [h:v]), the ground should be stepped or benched. The lowest bench, which will act as a key, should be a minimum of 15 feet wide and should be at least 2 feet deep into firm material, and approved by the geotechnical consultant. In fill-over-cut slope conditions, the recommended minimum width of the lowest bench or key is also 15 feet, with the key founded on firm material, as designated by the geotechnical consultant. As a general rule, unless specifically recommended otherwise by the geotechnical consultant, the minimum width of fill keys should be equal to ½ the height of the slope. Standard benching is generally 4 feet (minimum) vertically, exposing firm, acceptable material. Benching may be used to remove unsuitable materials, although it is understood that the vertical height of the bench may exceed 4 feet. Pre-stripping may be considered for unsuitable materials in excess of 4 feet in thickness. All areas to receive fill, including processed areas, removal areas, and the toes of fill benches, should be observed and approved by the geotechnical consultant prior to placement of fill. Fills may then be properly placed and compacted until design grades (elevations) are attained. COMPACTED FILLS Any earth materials imported or excavated on the property may be used in the fill provided that each material has been evaluated to be suitable by the geotechnical consultant. A.C. Mattos, Inc.Appendix E File:e:\wp21\8300\8320a.gep Page 3 GeoSoils, Inc. These materials should be free of roots, tree branches, other organic matter, or other deleterious materials. All unsuitable materials should be removed from the fill as directed by the geotechnical consultant. Soils of poor gradation, undesirable expansion potential, or substandard strength characteristics may be designated by the consultant as unsuitable and may require blending with other soils to serve as a satisfactory fill material. Fill materials derived from benching operations should be dispersed throughout the fill area and blended with other approved material. Benching operations should not result in the benched material being placed only within a single equipment width away from the fill/bedrock contact. Oversized materials defined as rock, or other irreducible materials, with a maximum dimension greater than 12 inches, should not be buried or placed in fills unless the location of materials and disposal methods are specifically approved by the geotechnical consultant. Oversized material should be taken offsite, or placed in accordance with recommendations of the geotechnical consultant in areas designated as suitable for rock disposal. GSI anticipates that soils to be used as fill material for the subject project may contain some rock. Appropriately, the need for rock disposal may be necessary during grading operations on the site. From a geotechnical standpoint, the depth of any rocks, rock fills, or rock blankets, should be a sufficient distance from finish grade. This depth is generally the same as any overexcavation due to cut-fill transitions in hard rock areas, and generally facilitates the excavation of structural footings and substructures. Should deeper excavations be proposed (i.e., deepened footings, utility trenching, swimming pools, spas, etc.), the developer may consider increasing the hold-down depth of any rocky fills to be placed, as appropriate. In addition, some agencies/jurisdictions mandate a specific hold-down depth for oversize materials placed in fills. The hold-down depth, and potential to encounter oversize rock, both within fills, and occurring in cut or natural areas, would need to be disclosed to all interested/affected parties. Once approved by the governing agency, the hold-down depth for oversized rock (i.e., greater than 12 inches) in fills on this project is provided as 10 feet, unless specified differently in the text of this report. The governing agency may require that these materials need to be deeper, crushed, or reduced to less than 12 inches in maximum dimension, at their discretion. To facilitate future trenching, rock (or oversized material), should not be placed within the hold-down depth feet from finish grade, the range of foundation excavations, future utilities, or underground construction unless specifically approved by the governing agency, the geotechnical consultant, and the developer’s representative. If import material is required for grading, representative samples of the materials to be used as compacted fill should be analyzed in the laboratory by the geotechnical consultant to evaluate it’s physical properties and suitability for use onsite. Such testing should be performed three (3) days prior to importation. If any material other than that previously tested is encountered during grading, an appropriate analysis of this material should be conducted by the geotechnical consultant as soon as possible. A.C. Mattos, Inc.Appendix E File:e:\wp21\8300\8320a.gep Page 4 GeoSoils, Inc. Approved fill material should be placed in areas prepared to receive fill in near horizontal layers, that when compacted, should not exceed about 6 to 8 inches in thickness. The geotechnical consultant may approve thick lifts if testing indicates the grading procedures are such that adequate compaction is being achieved with lifts of greater thickness. Each layer should be spread evenly and blended to attain uniformity of material and moisture suitable for compaction. Fill layers at a moisture content less than optimum should be watered and mixed, and wet fill layers should be aerated by scarification, or should be blended with drier material. Moisture conditioning, blending, and mixing of the fill layer should continue until the fill materials have a uniform moisture content at, or above, optimum moisture. After each layer has been evenly spread, moisture conditioned, and mixed, it should be uniformly compacted to a minimum of 90 percent of the maximum density as evaluated by ASTM test designation D 1557, or as otherwise recommended by the geotechnical consultant. Compaction equipment should be adequately sized and should be specifically designed for soil compaction, or of proven reliability to efficiently achieve the specified degree of compaction. Where tests indicate that the density of any layer of fill, or portion thereof, is below the required relative compaction, or improper moisture is in evidence, the particular layer or portion shall be re-worked until the required density and moisture content has been attained. No additional fill shall be placed in an area until the last placed lift of fill has been tested and found to meet the density and moisture requirements, and is approved by the geotechnical consultant. In general, per the latest adopted Code, fill slopes should be designed and constructed at a gradient of 2:1 (h:v), or flatter. Compaction of slopes should be accomplished by over-building a minimum of 3 feet horizontally, and subsequently trimming back to the design slope configuration. Testing shall be performed as the fill is elevated to evaluate compaction as the fill core is being developed. Special efforts may be necessary to attain the specified compaction in the fill slope zone. Final slope shaping should be performed by trimming and removing loose materials with appropriate equipment. A final evaluation of fill slope compaction should be based on observation and testing of the finished slope face. Where compacted fill slopes are designed steeper than 2:1 (h:v), prior approval from the governing agency, specific material types, a higher minimum relative compaction, special reinforcement, and special grading procedures will be recommended. If an alternative to over-building and cutting back the compacted fill slopes is selected, then special effort should be made to achieve the required compaction in the outer 10 feet of each lift of fill by undertaking the following: 1.An extra piece of equipment consisting of a heavy, short-shanked sheepsfoot should be used to roll (horizontal) parallel to the slopes continuously as fill is placed. The sheepsfoot roller should also be used to roll perpendicular to the slopes, and extend out over the slope to provide adequate compaction to the face of the slope. A.C. Mattos, Inc.Appendix E File:e:\wp21\8300\8320a.gep Page 5 GeoSoils, Inc. 2.Loose fill should not be spilled out over the face of the slope as each lift is compacted. Any loose fill spilled over a previously completed slope face should be trimmed off or be subject to re-rolling. 3.Field compaction tests will be made in the outer (horizontal) ±2 to ±8 feet of the slope at appropriate vertical intervals, subsequent to compaction operations. 4.After completion of the slope, the slope face should be shaped with a small tractor and then re-rolled with a sheepsfoot to achieve compaction to near the slope face. Subsequent to testing to evaluate compaction, the slopes should be grid-rolled to achieve compaction to the slope face. Final testing should be used to evaluate compaction after grid rolling. 5.Where testing indicates less than adequate compaction, the contractor will be responsible to rip, water, mix, and recompact the slope material as necessary to achieve compaction. Additional testing should be performed to evaluate compaction. SUBDRAIN INSTALLATION Subdrains should be installed in approved ground in accordance with the approximate alignment and details indicated by the geotechnical consultant. Subdrain locations or materials should not be changed or modified without approval of the geotechnical consultant. The geotechnical consultant may recommend and direct changes in subdrain line, grade, and drain material in the field, pending exposed conditions. The location of constructed subdrains, especially the outlets, should be recorded/surveyed by the project civil engineer. Drainage at the subdrain outlets should be provided by the project civil engineer. EXCAVATIONS Excavations and cut slopes should be examined during grading by the geotechnical consultant. If directed by the geotechnical consultant, further excavations or overexcavation and refilling of cut areas should be performed, or the remedial grading of cut slopes should be performed. When fill-over-cut slopes are to be graded, unless otherwise approved, the cut portion of the slope should be observed by the geotechnical consultant prior to placement of materials for construction of the fill portion of the slope. The geotechnical consultant should observe all cut slopes, and should be notified by the contractor when excavation of cut slopes commence. If, during the course of grading, unforeseen adverse or potentially adverse geologic conditions are encountered, the geotechnical consultant should investigate, evaluate, and make appropriate recommendations for mitigation of these conditions. The need for cut slope buttressing or stabilizing should be based on in-grading evaluation by the geotechnical consultant, whether anticipated or not. A.C. Mattos, Inc.Appendix E File:e:\wp21\8300\8320a.gep Page 6 GeoSoils, Inc. Unless otherwise specified in geotechnical and geological report(s), no cut slopes should be excavated higher or steeper than that allowed by the ordinances of controlling governmental agencies. Additionally, short-term stability of temporary cut slopes is the contractor’s responsibility. Erosion control and drainage devices should be designed by the project civil engineer and should be constructed in compliance with the ordinances of the controlling governmental agencies, and in accordance with the recommendations of the geotechnical consultant. COMPLETION Observation, testing, and consultation by the geotechnical consultant should be conducted during the grading operations in order to state an opinion that all cut and fill areas are graded in accordance with the approved project specifications. After completion of grading, and after the geotechnical consultant has finished observations of the work, final reports should be submitted, and may be subject to review by the controlling governmental agencies. No further excavation or filling should be undertaken without prior notification of the geotechnical consultant or approved plans. All finished cut and fill slopes should be protected from erosion and be planted in accordance with the project specifications and as recommended by a landscape architect. Such protection and planning should be undertaken as soon as practical after completion of grading. JOB SAFETY General At GSI, getting the job done safely is of primary concern. The following is the company's safety considerations for use by all employees on multi-employer construction sites. On-ground personnel are at highest risk of injury, and possible fatality, on grading and construction projects. GSI recognizes that construction activities will vary on each site, and that site safety is the prime responsibility of the contractor; however, everyone must be safety conscious and responsible at all times. To achieve our goal of avoiding accidents, cooperation between the client, the contractor, and GSI personnel must be maintained. In an effort to minimize risks associated with geotechnical testing and observation, the following precautions are to be implemented for the safety of field personnel on grading and construction projects: Safety Meetings: GSI field personnel are directed to attend contractor’s regularly scheduled and documented safety meetings. A.C. Mattos, Inc.Appendix E File:e:\wp21\8300\8320a.gep Page 7 GeoSoils, Inc. Safety Vests: Safety vests are provided for, and are to be worn by GSI personnel, at all times, when they are working in the field. Safety Flags:Two safety flags are provided to GSI field technicians; one is to be affixed to the vehicle when on site, the other is to be placed atop the spoil pile on all test pits. Flashing Lights:All vehicles stationary in the grading area shall use rotating or flashing amber beacons, or strobe lights, on the vehicle during all field testing. While operating a vehicle in the grading area, the emergency flasher on the vehicle shall be activated. In the event that the contractor's representative observes any of our personnel not following the above, we request that it be brought to the attention of our office. Test Pits Location, Orientation, and Clearance The technician is responsible for selecting test pit locations. A primary concern should be the technician’s safety. Efforts will be made to coordinate locations with the grading contractor’s authorized representative, and to select locations following or behind the established traffic pattern, preferably outside of current traffic. The contractor’s authorized representative (supervisor, grade checker, dump man, operator, etc.) should direct excavation of the pit and safety during the test period. Of paramount concern should be the soil technician’s safety, and obtaining enough tests to represent the fill. Test pits should be excavated so that the spoil pile is placed away from oncoming traffic, whenever possible. The technician's vehicle is to be placed next to the test pit, opposite the spoil pile. This necessitates the fill be maintained in a driveable condition. Alternatively, the contractor may wish to park a piece of equipment in front of the test holes, particularly in small fill areas or those with limited access. A zone of non-encroachment should be established for all test pits. No grading equipment should enter this zone during the testing procedure. The zone should extend approximately 50 feet outward from the center of the test pit. This zone is established for safety and to avoid excessive ground vibration, which typically decreases test results. When taking slope tests, the technician should park the vehicle directly above or below the test location. If this is not possible, a prominent flag should be placed at the top of the slope. The contractor's representative should effectively keep all equipment at a safe operational distance (e.g., 50 feet) away from the slope during this testing. The technician is directed to withdraw from the active portion of the fill as soon as possible following testing. The technician's vehicle should be parked at the perimeter of the fill in a highly visible location, well away from the equipment traffic pattern. The contractor should inform our personnel of all changes to haul roads, cut and fill areas or other factors that may affect site access and site safety. A.C. Mattos, Inc.Appendix E File:e:\wp21\8300\8320a.gep Page 8 GeoSoils, Inc. In the event that the technician’s safety is jeopardized or compromised as a result of the contractor’s failure to comply with any of the above, the technician is required, by company policy, to immediately withdraw and notify his/her supervisor. The grading contractor’s representative will be contacted in an effort to affect a solution. However, in the interim, no further testing will be performed until the situation is rectified. Any fill placed can be considered unacceptable and subject to reprocessing, recompaction, or removal. In the event that the soil technician does not comply with the above or other established safety guidelines, we request that the contractor bring this to the technician’s attention and notify this office. Effective communication and coordination between the contractor’s representative and the soil technician is strongly encouraged in order to implement the above safety plan. Trench and Vertical Excavation It is the contractor's responsibility to provide safe access into trenches where compaction testing is needed. Our personnel are directed not to enter any excavation or vertical cut which: 1) is 5 feet or deeper unless shored or laid back; 2) displays any evidence of instability, has any loose rock or other debris which could fall into the trench; or 3) displays any other evidence of any unsafe conditions regardless of depth. All trench excavations or vertical cuts in excess of 5 feet deep, which any person enters, should be shored or laid back. Trench access should be provided in accordance with Cal/OSHA and state, and local standards. Our personnel are directed not to enter any trench by being lowered or “riding down” on the equipment. If the contractor fails to provide safe access to trenches for compaction testing, our company policy requires that the soil technician withdraw and notify his/her supervisor. The contractor’s representative will be contacted in an effort to affect a solution. All backfill not tested due to safety concerns or other reasons could be subject to reprocessing or removal. If GSI personnel become aware of anyone working beneath an unsafe trench wall or vertical excavation, we have a legal obligation to put the contractor and owner/developer on notice to immediately correct the situation. If corrective steps are not taken, GSI then has an obligation to notify Cal/OSHA and the proper controlling authorities. A.C. Mattos, Inc.Appendix E File:e:\wp21\8300\8320a.gep Page 9