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HomeMy WebLinkAboutCDP 2022-0062; CRUSE HOUSE REMODEL, ADU/GARAGE; RESPONSE TO GEOTECHNICAL REPORT REVIEW COMMENTS AND GEOTECHNICAL UPDATE REPORT FOR PROPOSED ADDITION; 2024-04-26RESPONSE TO GEOTECHNICAL REPORT REVIEW COMMENTS AND GEOTECHNICAL UPDATE REPORT FOR PROPOSED ADDITION, NEW CAR GARAGE, AND ACCESSORY DWELLING UNIT (ADU), 3912 GARFIELD STREET CARLSBAD, CALIFORNIA 92008 (APN 206-012-02-00) FOR MR. GARY CRUSE 3912 GARFIELD STREET CARLSBAD, CALIFORNIA 92008 W.O. 8382-A1-SC APRIL 26, 2024GeoSoils,lnc. Geotechnical C Geologic C Coastal C Environmental 5741 Palmer Way Suite D, Carlsbad, CA 92010 TEL: (760) 438-3155 - FAX: (760) 931-0915 www.geosoilsinc.com April 26, 2024 W.O. 8382-A1-SC Mr. Gary Cruse 3912 Garfield Street Carlsbad, California 92008 Subject: Response to Geotechnical Report Review Comments and Geotechnical Update Report for Proposed Addition, New Car Garage, and Accessory Dwelling Unit (ADU), 3912 Garfield Street, Carlsbad, California 92008 (APN 206-012-02-00) Dear Mr. Cruse: In accordance with the City of Carlsbad geotechnical report review comments received, and your authorization, GeoSoils, Inc. (GSI) is providing herein responses to the City review comments and a geotechnical update report for the subject site, as noted. It is our understanding that site-specific design criteria from the 2022 California Building Code ([2022, CBC], California Building Standards Commission [CBSC], 2022), are now to be used for foundation designs within the project. As requested, based on the relative age of our referenced geotechnical report (GSI, 2022, see Appendix A) updated seismic design parameters are provided herein per current code standards, and also updated foundation design parameters, where appropriate. The scope of our services has included a review of the City comments, the grading plans by BHA, Inc. (BHAI, 2024), and the referenced documents in Appendix A, discussions with the you, geologic analyses, and preparation of this review response, updated geotechnical design recommendations and accompaniments. This response and geotechnical update should be reviewed in conjunction with the our limited geotechnical investigation for the site (GSI; 2022). Unless specifically superceded herein, the conclusions and recommendations contained in the referenced report by GSI (2022) remain pertinent and applicable, and should be appropriately implemented during remaining planning, design, and construction, as appropriate. GSI REVIEW RESPONSE For convenience, the reviewers comments are repeated below in italics, followed by GSI’s responses. Review Comment No. 1: Please review the most current grading and foundation plans for the proposed project and provide any additional geotechnical recommendations or modifications to the geotechnical report, as necessary. As the submitted geotechnical report was prepared approximately a year and a half ago and references the 2019 California Building Code, please revisit and update sections of the geotechnical report as necessary to address the currently adopted 2022 California Building Code. Response to Review Comment No. 1: Comment acknowledged. GSI has reviewed the grading plans by BHAI (2024) and found them to be in general accordance with our recommendations, and satisfactory from a geotechnical viewpoint. In addition, our updated foundation and seismic design parameters are provided in the following sections of this report, per current code standards (CBC, 2022). Review Comment No. 2: Please provide a statement addressing the potential impact of the proposed project on adjacent off-site properties from a geotechnical standpoint. Response to Review Comment No. 2: Comment acknowledged. GSI has reviewed the grading plans by BHAI (2024), and in our option, the proposed project will not impact adjacent offsite properties from a geotechnical standpoint, provided our recommendations are properly incorporated into grading and development of the property. Review Comment No. 3: Please provide an updated “Boring Location Map” utilizing the most current revision of the grading plan for the project as the base map and at a sufficiently large scale to clearly show (at a minimum): a) existing site topography and improvements, b) existing and proposed structures and improvements, c) proposed finished grades, d) geologic units, and e) the locations of subsurface exploration. Response to Review Comment No. 3: Comment acknowledged. GSI has updated our Boring Location Map with the most current revision of the grading plan by BHAI (2024). See Plate 1 (Boring Location Map). Mr. Gary Cruse W.O. 8382-A1-SC 3912 Garfield Street, Carlsbad April 26, 2024 File:e:\wp21\8300\8382a1.rtg Page 3GeoSoils, Inc. Review Comment No. 4: Strength (direct shear) testing of the on-site soils is not provided in the reviewed report. Please provide the appropriate laboratory testing to substantiate the values for bearing capacity, passive earth pressure, coefficient of friction, and active/at-rest earth pressures that are presented in the report. If presumptive values from the code are being recommended by the consultant, please indicate the soil class and use values consistent with the appropriate soil type (Class) in Tables 1806.2 and 1610.1 of the 2022 California Building Code. If soil parameters other than soil class 5 in Tables 1806.2 and 1610.1 are provided, please justify the soil type by site specific laboratory testing. The reviewer notes that some values provided in the report exceed the respective values for Class 5 and Class 4 soils in Table 1806.2. Please provide site specific laboratory test results to justify the use of any assumed values of C and Ö for the determination of the parameters requested above. Response to Review Comment No. 4: Previous sieve analysis testing was performed on a representative sample collected during subsurface exploration (GSI, 2022) and the soils were classified as silty SAND (SM). As such, the presumptive load-bearing values of CBC 2022 for bearing capacity, passive earth pressure and coefficient of friction have been appropriately updated in the following sections of this report. Review Comment No. 5: Please provide statements addressing the potential for liquefaction and Tsunami impact with respect to the subject site. Response to Review Comment No. 5: Comment acknowledged. GSI evaluated the liquefaction potential of site by reviewing available regional geotechnical hazard maps. According to the “City of Carlsbad Geotechnical Hazards Analysis and Mapping Study,” prepared by Leighton and Associates, Inc. (L&A, 1992), the subject site is located within Hazard Category No. 53, which includes relatively level mesas underlain by terrace deposits (now referred to as old paralic deposits on current regional geologic maps), sandstone, or granitic/metavolcanic bedrock. L&A (1992) assigned a land-use capability rating of “A” to Hazard Category No. 53. This indicates that the site is at low risk to geotechnical hazards. However, the site is located near the North American and Pacific tectonic plate boundary; and therefore, subject to moderate to strong ground shaking should an earthquake occur along any of the onshore and offshore active faults within the region. The possibility of ground acceleration, or shaking at the site, may be considered as approximately similar to the southern California region as a whole. Based on our review of California Geologic Survey Tsunami Hazard Area Map (CGS, 2024) the site is not located in tsunami hazard area. Mr. Gary Cruse W.O. 8382-A1-SC 3912 Garfield Street, Carlsbad April 26, 2024 File:e:\wp21\8300\8382a1.rtg Page 4GeoSoils, Inc. Review Comment No. 6: Please provide the amount of anticipated total settlement for the proposed development (only the value of potential differential settlement is currently provided in the report). Response to Review Comment No. 6: Based on our evaluations, foundations supporting the proposed ADU should be designed to accommodate static and seismic settlements of 1 inch and ½-inch, respectively (total settlement of 1½ inches), and a differential settlement of 1 inch in a 40-foot horizontal span (angular distortion = 1/480). Review Comment No. 7: Please provide updated seismic design parameters as necessary to address the current 2022 California Building Code Response to Review Comment No. 7: Comment acknowledged. As discussed previously, updated foundation and seismic design parameters have updated herein and are presented in the following sections of this report. Review Comment No. 8: Please provide recommendations (allowed vertical height, angle of inclination, etc.) for temporary cuts anticipated for remedial grading along property boundaries and the construction of the proposed retaining wall along the northwest property line as necessary to prevent adverse impact to adjacent off-site property. Response to Review Comment No. 8: Considering the nature of the onsite earth materials, caving or sloughing could be a factor in subsurface excavations and trenching. Shoring or excavating the trench walls/backcuts at the angle of repose (typically 25 to 45 degrees [except as specifically superceded within the text of this report]), should be anticipated. All excavations should be observed by one of our representatives and minimally conform to local safety codes and Cal-OSHA guidelines for Type “B” soils conditions, provided that groundwater, running sands, and/or other adverse conditions are absent. Excavations made in Type B soils should be performed as follows: • As per OSHA all simple slope excavations 20 feet or less in depth shall have a maximum allowable slope of 1:1. Mr. Gary Cruse W.O. 8382-A1-SC 3912 Garfield Street, Carlsbad April 26, 2024 File:e:\wp21\8300\8382a1.rtg Page 5GeoSoils, Inc. • All benched excavations 20 feet or less in depth shall have a maximum allowable slope of 1:1 and maximum bench dimensions with vertical height of 4 feet. • All excavations 20 feet or less in depth which have vertically sided lower portions shall be shielded or supported to a height at least 18 inches above the top of the vertical side. All such excavations shall have a maximum allowable slope of 1:1. • All other sloped excavations shall be in accordance with the other options permitted in section § 1926.652(b) of the CAL-OSHA guidelines (2011). Should adverse conditions exist, appropriate recommendations would be offered at that time. The above recommendations should be provided to any contractors or subcontractors, etc., that may perform such work. GEOTECHNICAL UPDATE REPORT BACKGROUND AND CURRENT SITE CONDITIONS The site was previously geotechnically investigated by GSI in 2022, as referenced in Appendix A. No significant changes in site or geotechnical conditions were observed since our previous study for the site were conducted. PROPOSED DEVELOPMENT Based on a review of the referenced documents, and review of the grading plans by BHAI (2024), it is our understanding that the proposed development will generally consist of preparing the site for the construction of an addition and remodel of the existing single-family residence, a new driveway, and a new detached garage with a second-story ADU. FAULTING AND REGIONAL SEISMICITY A discussion of local and regional faults are provided in GSI (2022). As requested, and based on the relative age of our previous report, updated seismic and foundation design parameters, per the CBC 2022, are presented below. General In the event of an upper bound (maximum probable) or credible earthquake occurring on any of the nearby major faults, strong ground shaking would occur in the subject site's general area. Potential damage to any structure(s) would likely be greatest from the vibrations and impelling force caused by the inertia of a structure's mass than from those Mr. Gary Cruse W.O. 8382-A1-SC 3912 Garfield Street, Carlsbad April 26, 2024 File:e:\wp21\8300\8382a1.rtg Page 6GeoSoils, Inc. induced by the hazards listed herein. This potential would be no greater than that for other existing structures and improvements in the immediate vicinity. Updated Seismic Shaking Parameters The following table summarizes the reevaluated site-specific design criteria obtained from the 2022 CBC, Chapter 16 Structural Design, Section 1613, Earthquake Loads. The computer program Seismic Design Maps, provided by the Structural Engineers Association of California and California Office of Statewide Health Planning and Development (SEAOC/OSHPD, 2024) has been used to aid in design (https://seismicmaps.org). The short spectral response uses a period of 0.2 seconds. 2022 CBC SEISMIC DESIGN PARAMETERS PARAMETER SITE-SPECIFIC DESIGN VALUE PER ASCE 7-16 2022 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 0.883g (Section 21.3) Section 1613.2.1, Figure 1613.2.1(1) Spectral Response - (1 sec), S1 0.693 g (Section 21.3) Section 1613.2.1, Figure 1613.2.1(2) Site Coefficient, Fa 1.0(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 1.349 g(4) (Section 21.4)Section 1613.2.3 (Eqn 16-36) Maximum Considered Earthquake Spectral Response Acceleration (1 sec),SM1 1.125 g(5) (Section 21.4)Section 1613.2.3 (Eqn 16-37) 5% Damped Design Spectral Response Acceleration (0.2 sec), SDS 0.899 g(6)Section 1613.2.4 (Eqn 16-38) 5% Damped Design Spectral Response Acceleration (1 sec), SD1 0.751 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. 0.568 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)(0.899 g) = 1.349 g 5. Per Section 21.4 of ASCE 7-16, SM1 = (1.5)(SD1) = (1.5)(0.751 g) = 1.125 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, Mapped S1 (0.395 g) # 0.75. Thus, the seismic design category is “D”. Mr. Gary Cruse W.O. 8382-A1-SC 3912 Garfield Street, Carlsbad April 26, 2024 File:e:\wp21\8300\8382a1.rtg Page 7GeoSoils,lnc. GENERAL SEISMIC PARAMETERS PARAMETER VALUE Distance to Seismic Source Elsinore (Rose Canyon) 5.0 mi (8.0 km)(1) Upper Bound Earthquake Elsinore (Rose Canyon) MW = 7.2(2) (1) - Blake (2000a) (2) - Cao, et al. (2003) 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 2022 CBC (CBSC, 2022a) and regular maintenance and repair following locally significant seismic events (i.e., Mw 5.5) will likely be necessary, as is the case in all of Southern California. CONCLUSIONS AND RECOMMENDATIONS Based on our review of the available data (see Appendix A), our previous investigation conducted (GSI, 2022), the proposed development of the subject site appears feasible from a geotechnical viewpoint, provided the conclusions and recommendations presented herein, and in GSI 2022 are properly incorporated into the design and construction of the project. All other findings, conclusions and recommendations in previous referenced report by GSI remain pertinent and applicable except as specifically superceded herein. Updated recommendations are presented below. Based on our knowledge of site conditions and conditions in the general area of the proposed development, in our opinion the proposed development will not affect the offsite properties from geotechnical standpoint. RECOMMENDATIONS FOR GRADING General 1. All grading should be performed in accordance with the 2022 CBC, and City of Carlsbad guidelines. 2. Geotechnical observations and compaction testing services should be provided during grading. 3. At the completion of grading and earthwork, and after the geotechnical consultant has finished observations and testing of the work completed, a final as-graded Mr. Gary Cruse W.O. 8382-A1-SC 3912 Garfield Street, Carlsbad April 26, 2024 File:e:\wp21\8300\8382a1.rtg Page 8 I I I I GeoSoils,lnc. compaction report should be prepared, and may be subject to review by the controlling governmental agencies. 4. General Earthwork and Grading Guidelines are provided at the end of this report as Appendix B. Specific recommendations are provided below. PRELIMINARY FOUNDATION RECOMMENDATIONS The proposed foundation systems should be designed and constructed in accordance with current standards of practice, the guidelines contained within the 2022 CBC, the ACI (2015 and 2014a), and the updated total and differential settlement values provided herein. Recommendations by the project's design-structural engineer or architect, which may exceed the geotechnical consultant’s recommendations, should take precedence over the recommendations presented herein. If the information concerning the proposed development plans is not correct, or any changes in the design, location or loading conditions of the proposed structures are made, the conclusions and recommendations contained in the GSI reports should not be considered valid unless the changes are reviewed and conclusions of this report are modified or approved in writing by this office. Upon request, GSI could provide additional input/consultation regarding soil parameters, as they relate to foundation design. General Foundation Design 1. The foundation systems should be designed and constructed in accordance with guidelines presented in the 2022 CBC. 2. Based on soil physical characteristics, and disposition, the presumptive load-bearing values provided in 2022 CBC Table 1806.2 have been used to determine an allowable bearing value of 2,000 pounds per square foot (psf) for the design of one-story footings, that maintain a minimum width of 12 inches and a minimum depth of 12 inches (below the lowest adjacent grade, or two-story footings, that maintain a minimum width of 15 inches and a minimum depth of 18 inches, and are founded entirely into properly compacted, engineered fill. This value may be increased by 20 percent for each additional 12 inches in footing depth to a maximum value of 2,500 psf. These values may be increased by one-third when considering short duration seismic or wind loads. Isolated pad footings should have a minimum dimension of at least 24 inches square and a minimum embedment of 24 inches below the lowest adjacent grade into properly engineered fill. Foundation embedment depth excludes concrete slabs-on-grade, slab underlayment, and any landscaped zones. Mr. Gary Cruse W.O. 8382-A1-SC 3912 Garfield Street, Carlsbad April 26, 2024 File:e:\wp21\8300\8382a1.rtg Page 9GeoSoils, Inc. 3. For foundations deriving passive resistance from engineered fill, a passive earth pressure may be computed as an equivalent fluid having a density of 150 pcf, with a maximum earth pressure of 1,500 psf. 4. For lateral sliding resistance, a 0.25 coefficient of friction may be used for a concrete to soil contact when multiplied by the dead load. 5. When combining passive pressure and frictional resistance, the passive pressure component should be reduced by one-third. 6. All footing setbacks from slopes should comply with Figure 1808.7.1 of the 2022 CBC. GSI recommends a minimum horizontal setback distance of 7 feet as measured from the bottom (i.e., bearing elevation), outboard edge of the footing to the slope face. 7. Footings for structures adjacent to retaining walls should be deepened so as to extend below a 1:1 projection from the heel of the wall should this condition occur. Alternatively, walls may be designed to accommodate structural loads from buildings or appurtenances as described in GSI 2022. 8. All interior and exterior column footings should be tied to the perimeter wall footings in at least one direction for very low expansive soils. The base of the reinforced grade beam should be at the same elevation as the adjoining footings. 9. The project structural engineer should consider the use of transverse and longitudinal control joints to help control slab cracking due to concrete shrinkage or expansion. Two of the best ways to control this movement are: 1) add a sufficient amount of reinforcing steel to increase the tensile strength of the slab; and 2) provide an adequate amount of control or expansion joints to accommodate anticipated concrete shrinkage and expansion. Transverse and longitudinal crack control joints should be spaced no more than 13 feet on center and constructed to a minimum depth of T/4, where "T" equals the slab thickness in inches. Per Portland Cement Association (PCA) and ACI guidelines, joints are commonly spaced at distances equal to 24 to 30 times the slab thickness. Joint spacing that is greater than 15 feet requires the use of load transfer devices (dowels or diamond plates). 10. Foundations supporting the proposed ADU should be designed to accommodate static and seismic settlements of 1 inch and ½-inch, respectively (total settlement of 1½ inches), and a differential settlement of 1 inch in a 40-foot horizontal span (angular distortion = 1/480). Subsurface Water Groundwater was not encountered within any of our exploratory borings conducted during our initial geotechnical investigation (GSI, 2022). The regional groundwater table is Mr. Gary Cruse W.O. 8382-A1-SC 3912 Garfield Street, Carlsbad April 26, 2024 File:e:\wp21\8300\8382a1.rtg Page 10GeoSoils, Inc. anticipated to be coincident with sea level, or approximately 60 feet below the lowest existing site elevation. However, perched groundwater may exist near the geologic contact between the old paralic deposits and the underlying Santiago Formation (Kennedy and Tan, 2007). Seasonal and cyclical variations in groundwater conditions from those encountered during field work, performed in preparation of this update report, cannot be entirely precluded and should be anticipated. Due to its depth below the site, the regional groundwater table is not considered a significant geotechnical concern. Site Improvements If any additional improvements (e.g., structures, walls, etc.) are planned for the site, recommendations concerning the geological or geotechnical aspects of design and construction of said improvements could be provided upon request. 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, utility trench and retaining wall backfills, flatwork, etc. Additional Grading This office should be notified in advance of any fill placement, supplemental regrading of the site, or trench backfilling after rough grading has been completed. This includes completion of grading in the amphitheater areas, utility trench, and retaining wall backfills. Trenching/Temporary Construction Backcuts Considering the nature of the onsite earth materials, caving or sloughing could be a factor in subsurface excavations and trenching. Shoring or excavating the trench walls/backcuts at the angle of repose (typically 25 to 45 degrees [except as specifically superceded within the text of this report]), should be anticipated. All excavations should be observed by one of our representatives and minimally conform to local safety codes and Cal-OSHA guidelines for Type “B” soils conditions, provided that groundwater, running sands, and/or other adverse conditions are absent. Should adverse conditions exist, appropriate recommendations would be offered at that time. The above recommendations should be provided to any contractors or subcontractors, etc., that may perform such work. SUMMARY OF RECOMMENDATIONS REGARDING GEOTECHNICAL OBSERVATION AND TESTING We recommend that observation or testing be performed by GSI at each of the following construction stages: • During grading/recertification. Mr. Gary Cruse W.O. 8382-A1-SC 3912 Garfield Street, Carlsbad April 26, 2024 File:e:\wp21\8300\8382a1.rtg Page 11GeoSoils, Inc. • During excavation. • During placement of subdrains, toe drains, or other subdrainage devices, prior to placing of fill or backfill. • After excavation of building footings, retaining wall footings, and free standing walls footings, prior to the placement of reinforcing steel or concrete. • Prior to pouring any slabs or flatwork, after presoaking/presaturation of building pads and other flatwork subgrade, before the placement of concrete, reinforcing steel, capillary break (i.e., sand, pea-gravel, etc.), or vapor retarders. • During retaining wall subdrain installation, prior to backfill placement. • During placement of backfill for area drains, interior plumbing, utility line trenches, and retaining wall backfill. • During slope construction/repair. • When any unusual soil conditions are encountered during any construction operations, after to the issuance of this report. • When any developer or owner improvements, such as flatwork, foundations, walls, etc., are proposed, prior to construction. GSI should review and approve such plans, prior to construction • 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, or to comply with code requirements. OTHER DESIGN PROFESSIONALS/CONSULTANTS The design civil engineer, structural engineer, foundation designer, 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 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. Please note that the recommendations contained herein are not intended to preclude the transmission of water or vapor through the slab or foundation. The structural engineer/foundation or slab designer should provide recommendations to not allow water or vapor to enter into the Mr. Gary Cruse W.O. 8382-A1-SC 3912 Garfield Street, Carlsbad April 26, 2024 File:e:\wp21\8300\8382a1.rtg Page 12GeoSoils, Inc. structure so as to cause damage to another building component, or so as to limit the installation of the type of flooring materials typically used for the particular application, per the State of California (2024). 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. 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 or expansion characteristics and other design criteria specified herein. 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 and engineering analyses and laboratory data, the conclusions and recommendations are professional opinions. These opinions have been derived in accordance with current standards of practice, and no warranty, either express or implied, is given. Standards of practice are subject to change with time. 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. Mr. Gary Cruse W.O. 8382-A1-SC 3912 Garfield Street, Carlsbad April 26, 2024 File:e:\wp21\8300\8382a1.rtg Page 13GeoSoils, 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 submitt GeoSoils, Inc. 1t~(?v~l Todd A. Greer ~~- ~J.Coover Engineering Geologist, CEG 2377 Geotechnical Engineer, GE 2057 MK/SJC/T AG/sh Enclosures: Appendix A -References Appendix B -General Earthwork and Grading Guidelines Plate 1 (Revised) -Boring Location Map Distribution: (1) Addressee (PDF via email) Mr. Gary Cruse 3912 Garfield Street, Carlsbad File:e:\wp21 \8300\8382a1 .rtg GeoSoils,lnc. W.O. 8382-A1-SC April 26, 2024 Page 14 APPENDIX A REFERENCES GeoSoils, Inc. APPENDIX A REFERENCES American Concrete Institute, 2015, Guide to concrete floor and slab construction (ACI 318-15): reported by ACI Committee 302, dated June. _____, 2014a, Building code requirements for structural concrete (ACI 318-14), and commentary (ACI 318R-14): reported by ACI Committee 318, dated September. _____, 2014b, Building code requirements for concrete thin shells (ACI 318.2-14), and commentary (ACI 318.2R-14), dated September. _____, 2004, Guide for concrete floor and slab construction: reported by ACI Committee 302; Designation ACI 302.1R-04, dated March 23. American Society of Civil Engineers, 2018a, Supplement 1 to minimum design loads and associated criteria for buildings and other structures (ASCE/SEI 7-16), first printing, dated December 13. _____, 2018b, Errata for minimum design loads and associated criteria for buildings and other structures (ASCE/SEI 7-16), by ASCE, dated July 9. _____, 2017, Minimum design loads and associated criteria and other structures, ASCE Standard ASCE/SEI 7-16, published online June 19. _____, 2010, Minimum design loads for buildings and other structures, ASCE Standard ASCE/SEI 7-10. BHA, Inc., 2024, Grading plans for 3912 Garfield street, Carlsbad, dated March 11. Blake, T.F., 2000, EQFAULT, A computer program for the estimation of peak horizontal acceleration from 3-D fault sources; updated to September, 2004. Bryant, W.A., and Hart, E.W., 2007, Fault-rupture hazard zones in California, Alquist-Priolo earthquake fault zoning act with index to earthquake fault zones maps, special publication 42, California Geological Survey. California Building Standards Commission, 2022, California Building Code, California Code of Regulations, Title 24, Part 2, Volumes 1 and 2, based on the 2021 International Building Code, effective January 1, 2023. California Code Of Regulations, 2011, CAL-OSHA State of California Construction and Safety Orders, dated February. GeoSoils, Inc. 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. _____, 2008, Guidelines for evaluating and mitigating seismic hazards in California: California Geological Survey Special Publication 117A (revised 2008), 102 p. California Geological Survey Tsunami hazardmMap, 2024, https://maps.conservation .ca.gov/cgs/informationwarehouse/ts_evacuation/. Cao, T., Bryant, W.A., Rowshandel, B., Branum, D., and Wills, C.J., 2003, The revised 2002 California probabilistic seismic hazard maps, dated June, http://www.conservation.ca.gov/cgs/rghm/psha/fault_parameters/pdf/Documents /2002_CA_Hazard_Maps.pdf. City of Carlsbad Land Development Engineering, 2024, Geotechnical report review, 3912 Garfield Street (1st review), 2 pgs., proj. ID, CPD2022-0062, grading permit no. GR2023-0043, dated January 19. GeoSoils, Inc., 2022, Limited geotechnical investigation of proposed addition, new car garage, and accessory dwelling unit (ADU), 3912 Garfield Street, Carlsbad, San Diego County, California, W.O. 8382-A-SC, dated August 15. Kennedy, M.P., and Tan, SS., 2007, Geologic map of the Oceanside 30' by 60' quadrangle, California, regional map series, scale 1:100,000, California Geologic Survey and United States Geological Survey, www.conservation.ca.gov/ cgs/rghm/rgm/preliminary_geologic_maps.html Leighton and Associates, Inc., 1992, City of Carlsbad geotechnical hazards analysis and mapping study, Carlsbad, California, 115 sheets, scale: 1 inch = 400 feet, dated November. Structural Engineers Association of California and California Office of Statewide Health Planning and Development, 2024, Seismic design maps, https://seismicmaps.org/. Mr. Gary Cruse Appendix A File:e:\wp21\8300\8382a1.rtg Page 2GeoSoils, Inc. APPENDIX B 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), and/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 accordance with test methods ASTM designation D 1556, D 2937 or D 2922, GeoSoils, Inc. 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 Codes 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 or treated in a manner recommended by the geotechnical consultant. Soft, dry, spongy, Mr. Gary Cruse Appendix B File:e:\wp21\8300\8382a1.rtg Page 2GeoSoils, Inc. 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 utilized in the fill provided that each material has been evaluated to be suitable by the geotechnical consultant. These materials should be free of roots, tree branches, other organic matter, Mr. Gary Cruse Appendix B File:e:\wp21\8300\8382a1.rtg Page 3GeoSoils, Inc. 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 utilized 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/or the developer’s representative. If import material is required for grading, representative samples of the materials to be utilized 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. Mr. Gary Cruse Appendix B File:e:\wp21\8300\8382a1.rtg Page 4GeoSoils, 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/or 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/or 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. Mr. Gary Cruse Appendix B File:e:\wp21\8300\8382a1.rtg Page 5GeoSoils, 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, and/or 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. Mr. Gary Cruse Appendix B File:e:\wp21\8300\8382a1.rtg Page 6GeoSoils, 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/or 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/or be planted in accordance with the project specifications and/or as recommended by a landscape architect. Such protection and/or 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. 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. Mr. Gary Cruse Appendix B File:e:\wp21\8300\8382a1.rtg Page 7GeoSoils, Inc. 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. Mr. Gary Cruse Appendix B File:e:\wp21\8300\8382a1.rtg Page 8GeoSoils, 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/or 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 and/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/or the proper controlling authorities. Mr. Gary Cruse Appendix B File:e:\wp21\8300\8382a1.rtg Page 9GeoSoils, Inc. Plate 1 SCALE: 1”= 10’ DATE: 04/24 W.O. 8382-A1-SC ALL LOCATIONS ARE APPROXIMATE This document or e-file is not part of the Construction Documents and should not be relied upon as being an accurate depiction of design. BORING LOCATION MAP GSI LEGEND Artificial fill - undocumented Afu Quaternary-age old paralic deposits, circled where buried Qop Figure adapted from: Grading Plan by BHA Inc., 2024 HA-5 Approximate location of hand-auger boring by GSI. 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