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HomeMy WebLinkAboutCT 80-46; HIGHLAND DRIVE 5 LOT SF RESIDENCES; RESPONSE TO CITY COMMENTS HIGHLAND 5; 2022-08-22Project No. G2861-11-01 August 22, 2022 California West Communities 5927 Priestly Drive, Suite 110 Carlsbad, California 92008 Attention: Mr. Matt Howe Subject: RESPONSE TO CITY COMMENTS HIGHLAND 5 2908 – 2924 HIGHLAND DRIVE CARLSBAD, CALIFORNIA References: 1. Update Geotechnical Investigation, Highland 5, 2908 – 2924 Highland Drive, Carlsbad, California, prepared by Geocon Incorporated, dated December 29, 2021 (Project No. G2861-11-01). 2. Preliminary Geotechnical Evaluation, Proposed 5-Lot Subdivision, Tract No. 80-46, Carlsbad, San Diego County, California, Assessor’s Parcel Number (APN’s) 156- 200-28, -29, -30, -31, -32, prepared by GeoSoils, Inc., dated February 1, 2021 (W.O. 8037-A-SC). 3. Grading Plans for: Highland, 2908 – 2924 Highland Drive, prepared by the Pasco, Laret, Suiter & Associates, dated August 22, 2022 (Project No. CT 80-46)(Drawing No. 534-7A). 4. Geotechnical Report Review Highland Drive – 5 Lot SFR, 2908-2924 Highland Drive, prepared by The City of Carlsbad, 1st Review, dated August 13, 2022. Dear Mr. Howe: In accordance with the request of PLSA, we have prepared this letter to address geotechnical review comments provided by the City of Carlsbad Land Development Engineering regarding the subject project. The geotechnical review comment is included with our response immediately following. Comment 1:Please review the most current grading plan for the project and provide any additional geotechnical recommendations or modifications to the geotechnical report as necessary. Response:We have reviewed the referenced grading plans and opine the plans and details have been prepared in substantial conformance with the recommendations presented in the referenced geotechnical report prepared by Geocon, Inc. We limited our review to geotechnical aspects of project plans and the review did not GEOCON INCORPORATED G E OT E CHN I CAL ■E NV I RONMENTA L ■ MA T ER I A L S 6960 Flanders Drive ■ Son Diego, California 92121-297 4 ■ Telephone 858.558.6900 ■ Fax 858.558.6159 Geocon Project No. G2861-11-01 - 2 - August 22, 2022 include other details on the referenced plans and calculations. Geocon Incorporated has no opinion regarding other details found on the referenced plans and calculations, structural or otherwise, that do not directly pertain to geotechnical aspects of site improvements. Comment 2:Please expand on the description of the proposed project and discuss the proposed grading (Depths and limits of cut/fill, heights of cut/fill slopes, etc., necessary to establish proposed grades) and heights of any proposed retaining walls. Response:Based on a discussion with the civil engineer and review of the grading plans, we anticipate maximums cuts of approximately 10 feet, maximum fills of approximately 4½ feet with a maximum retaining wall height of approximately 6 feet. Comment 3:Please provide a description of the subsurface exploration and sampling methods performed as part of the field investigation. Response:Our update geotechnical report was prepared to become the geotechnical engineer of record for California West utilizing the previous Geotechnical Investigation prepared by GeoSoils, Inc. (2021 – Reference No. 2). The field investigation for the previous Geotechnical Investigation was performed on January 7 and 8, 2021 utilizing a truck-mounted drill rig to excavate five exploratory borings and three percolation test borings. Based on the boring logs in the referenced report, samples were taken using a California Sampler which is typically composed of steel and driven to obtain ring samples. The sampler has an inside diameter of 2.5 inches and an outside diameter of 3 inches. Bulk bag samples were also obtained. Based on the geologic conditions at the site, no additional field exploration was deemed necessary. Comment 4:Please discuss and address site specific infiltration testing for potential storm water infiltration associated with the proposed project. Response:The previous report prepared by GeoSoils, Inc. included the Categorization of Infiltration Condition (Form I-8) that discussed the potential for infiltration at the site. Infiltration testing was conducted in two borings within the vicinity of the proposed storm water basins. They calculated a design infiltration rate of 0.87 inches/hour after a factory of safety of 2 was applied. Due to the dense nature of the underlying formational material, they concluded that allowing infiltration could create a “perched” and mounded water table while increasing the risk of distress to existing and proposed improvements. We opine that the site has been adequately characterized to conclude the site is a no infiltration condition. We have included the previously prepared Form I-8 following the text of this letter. Comment 5:Please discuss the geologic structure associated with the Old Paralic deposits and potential impact on the proposed development. Response:The Old Paralic deposits generally consist of dense to very dense, reddish brown and olive brown, silty, fine to coarse sandstone. This unit is typically massively bedded with occasional gravel beds. Bedding is typically not discernible when exposed in a slope or cut areas, therefore, adverse bedding conditions are not expected. The Old Paralic deposits are considered suitable for the support of the Geocon Project No. G2861-11-01 - 3 - August 22, 2022 planned fill and foundation loads for the development. We opine the geologic structure of these deposits will not adversely affect the project performance. Comment 6:Please provide a discussion addressing the local and regional faulting associated with the subject site. Please include the names, distances, and potential magnitudes of faults potentially impacting the subject property. Response:Based on a review of the referenced report prepared by GeoSoils, the site is not underlain by active, potentially active, or inactive faults. The site may be impacted with possible moderate to strong seismic shaking due to nearby fault zones. The active fault zones within 10 miles of the site are summarized in Table 1. TABLE 1 ACTIVE FAULTS WITHIN 10 MILES OF THE SITE LIMITS Fault Name Fault Distance From Site (In Miles) Maximum Earthquake Magnitude Newport-Inglewood (Offshore) 5.7 7.1 Rose Canyon 6.1 7.2 Comment 7:Strength (direct shear) testing of the on-site soils is not provided in the report. Please provide the appropriate laboratory testing to substantiate the values for bearing capacity, passive pressure, coefficient of friction, and active pressure that are presented in the report. If presumptive values are being recommended by the consultant, please state the reference, and use values consistent with the appropriate soil type in Tables 1806.2 and 1610.1 of the 2019 California Building Code (please justify the soil type by laboratory testing if something other than Soil Class 5 in Table 1806.2 is provided as the basis for the assumed values). Response:Laboratory testing was performed by GeoSoils, Inc. that indicated the tested soils would be classified as a Silty Sand (SM) soil type with an expansion index of less than 20. Based on the boring logs and our experience in the project area, we expect that these materials are consistent across the site and have provided recommendations accordingly. Based on these results alone, the soil would be classified as a Soil Class 4 per CBC Table 1806.2 if code-based minimum values were used. However, Geocon Incorporated performed the Geotechnical Investigation and construction services for the Buena Vista Reservoir Park project which bounds the subject property to the north. Soil conditions encountered during that project are consistent with those encountered by GeoSoils, Inc. on the subject site, and as a result, are considered acceptable for use a reference for our geotechnical design recommendations. The direct shear results from laboratory testing at the adjacent site are provided in Table 2. Geocon Project No. G2861-11-01 - 4 - August 22, 2022 TABLE 2 SUMMARY OF LABORATORY DIRECT SHEAR TEST RESULTS - BUENA VISTA RESERVOIR PARK PROJECT (GEOCON, 2019) ASTM D 3080 Sample No. Geologic Unit Average Dry Density(pcf) Average Moisture Content (%) Peak [Ultimate*] Cohesion (psf) Peak [Ultimate*] Angle of Shear Resistance (degrees) Initial Final T2-1†Qudf 119.0 9.0 13.3 700 [575] 26 [26] T3-1†Qop 122.0 7.6 12.1 700 [535] 25 [24] T10-2 Qop 110.5 6.9 15.8 575 [565] 26 [25] *Ultimate defined as the end-of-test strength after about 0.2 inches of deflection. †Sample was remolded to a dry density of about 90 percent of the laboratory maximum dry density. Therefore, based on the results of on-site and adjacent property laboratory testing and our experience with similar materials, we consider the design recommendations provided in our Geotechnical Investigation for the subject site to be adequate and that the use of code-based minimum values does not apply. Comment 8:Please justify the use of an active pressure of 35 pcf (see Comment #7 above). Response:See response to Comment 7 above. Comment 9:The text of the report (page 10) and lab testing indicate the on-site soils are considered “non-expansive” with an Expansion Index less than 20. However, Table 7.6 on page 15 of the report indicates the foundation recommendations are for an Expansion Index less than 50. As soils with expansion index (EI) over 20 are considered expansive and required mitigation in accordance with Sections 1803.5.3 and 1808.6 of the 1029 CBC, please revised Table 7.6 or provide the methods that are being recommended to address expansive soils (for soils with an EI between 20 and 50) and provide a statement that the foundation system for the proposed residential structures will meet the requirements of Section 1808.6 of the 2019 California Building Code. Response:We anticipate that the onsite soils will be “non-expansive” based on previous laboratory testing. However, we have provided the recommendations in our report to accommodate the “very low” to “low” expansion potential as a measure of conservatism. Our recommendations for minimum steel reinforcement for shallow foundations, concrete slabs-on-grade and exterior concrete flatwork and our retaining wall design loads are provided to accommodate the “very low” to “low” expansion potential. Therefore, the recommendations provided in our report are intended to provide the structural engineer with minimum design values that meet the requirements of Section 1808.6 of the 2019 California Building Code for expansive soils. Comment 10:Please provide the minimum thickness for the vapor retarder (15-mil, etc.) from a geotechnical standpoint. Response:From a geotechnical standpoint we recommend a minimum vapor retarder of between 10 and 15 mil thickness. Geocon Project No. G2861-11-01 - 5 - August 22, 2022 Comment 11:Please provide geotechnical recommendations (slope inclination, keys, subdrains, etc.) for the construction of fill and/or cut slopes associated with the proposed development. Response:Grading recommendations for slopes, keyways and subdrains are included in Appendix C of the referenced Geocon report. Comment 12:Please provide recommendations (maximum allowed vertical cut, inclination of backcut, etc.) for temporary slopes from a geotechnical standpoint. Response:It is the responsibility of the contractor and their competent person to ensure all temporary excavations, temporary slopes, and trenches are properly constructed and maintained in accordance with applicable OSHA guidelines in order to maintain safety and the stability of the excavations and adjacent improvements. These excavations should not be allowed to become saturated or to dry out. Surcharge loads should not be permitted to a distance equal to the height of the excavation from the top of the excavation. The top of the excavation should be a minimum of 15 feet from the edge of existing improvements. Excavations steeper than those recommended or closer than 15 feet from an existing surface improvement should be shored in accordance with applicable OSHA codes and regulations. The stability of the excavations is dependent on the design and construction of the shoring system and site conditions. Therefore, Geocon Incorporated cannot be responsible for site safety and the stability of the proposed excavations. Comment 13:Please add retaining wall and keyway subdrains, temporary slopes, and hardscape subgrade to the list of “Expected Geotechnical Testing and Observation Services”. Response:We have included a revised table of expected services below. TABLE 3 EXPECTED GEOTECHNICAL TESTING AND OBSERVATION SERVICES Construction Phase Observations Expected Time Frame Grading Base of Removal Part Time During Removals Geologic Logging Part Time to Full Time Fill Placement and Soil Compaction Full Time Subdrain Installation Part Time Foundations Foundation Excavation Observations Part Time Utility Backfill and Temporary Slopes Fill Placement and Soil Compaction Part Time to Full Time Retaining Wall Backfill Fill Placement and Soil Compaction Part Time to Full Time Subdrain Installation Part Time Subgrade for Hardscape, Curb/Gutter, and Pavement Soil Compaction Part Time Pavement Construction Base Placement and Compaction Part Time Asphalt Concrete Placement and Compaction Full Time Geocon Project No. G2861-11-01 - 6 - August 22, 2022 If you have any questions regarding this correspondence, or if we may be of further service, please contact the undersigned at your convenience. Very truly yours, GEOCON INCORPORATED Kenneth W. Haase PG 9974 Matt R. Love RCE 84154 John Hoobs CEG 1524 KWH:SFW:JH:arm Attachments: Form I-8A (e-mail) Addressee GeoSoils, Inc. Cross Real Estate Investors, LLC W.O. 8037-A-SC Tract 80-46, Carlsbad January 27, 2021 File:e:\wp12\8000\8037.pge Page 37 STORM WATER TREATMENT AND HYDROMODIFICATION MANAGEMENT USDA Study A review of the United States Department of Agriculture database ([USDA]; 1973, 2020) indicates that site soils located within the upper and lower elevations of the western two- thirds of the site are classified as Marina loamy coarse sand (2-30 percent slopes). The USDA study further indicates that the Marina series is classified as belonging to Hydrologic Soil Group “B.” A review of USDA (1973 and 2019) indicates that the capacity of the most limiting layer to transmit water (Ksat) within the Marina loamy coarse sand is moderately high to high (0.57 to 01.98 inches per hour [in/hr]). Some soils identified as Marina loamy coarse sand may be removed and recompacted as engineered fill during grading operations. Infiltration Feasibility Per our onsite infiltration test results, an infiltration rate at the location tested onsite ranged between 1.74 inches per hour to 2.82 inches per hour (See Table below). Test holes IB-1 and IB-2 are generally above the recommended feasibility threshold of 0.52 inches per hour per the EPA (Clar, et al., 2004), and 0.50 inches per hour per the County (2019) for full infiltration. With a factor of safety of 2, and utilizing the most conservative design infiltration rate for IB-1, the design rate is 0.87 inches/hour. The permeability of the underlying soil/bedrock can be expected to decrease with depth, as the soil/bedrock becomes less weathered, thereby promoting the lateral migration of water in soil. Test data sheets are presented in Appendix E. Boring locations (IB-1, IB-2 and IB-3), are shown on Plate 1. INFILTRATION TEST HOLE OBSERVED FIELD INFILTRATION RATE (INCHES PER HOUR)SOIL UNIT PER USDA (1973) IB-1 1.74 Marina Loamy Coarse Sand IB-2 2.82 Marina Loamy Coarse Sand Proposed or existing fill, and/or moisture-sensitive improvements, such as pavements, and utility trench backfill, foundations, retaining walls, and below grade building walls, would likely be adversely affected by excessive soil moisture, including existing offsite improvements, causing settlement and distress. Bio-basins can adversely affect the performance of the onsite and offsite structures, foundation systems by: 1) increasing soil moisture transmission rates through concrete flooring, 2) reducing the stability of slopes, and 3) increasing the potential for a loss in bearing strength of soil. Onsite mitigative grading of compressible near-surface soils for the support of structures generally involves removal and recompaction. This is anticipated to create the potential for permeability contrast, and the potential for the development of a shallow “perched” and mounded water table, which can reasonably be anticipated to migrate laterally, beneath the structure(s), or offsite onto adjacent property, causing settlement and associated distress. Based on City (2016), the I I I I I I GeoSoils, Inc. Cross Real Estate Investors, LLC W.O. 8037-A-SC Tract 80-46, Carlsbad January 27, 2021 File:e:\wp12\8000\8037.pge Page 38 calculated infiltration rate with safety factor added yields a rate of 0.87 inches per hour, which is above the minimum acceptable rate of 0.025 inches per hour; however, “no infiltration” is recommended, owing to the potential to cause distress to existing and proposed improvements, both onsite and offsite. In addition, infiltrating into site soils within 10 feet of any settlement sensitive structure/improvement is considered poor engineering judgement. In addition, “no infiltration” is recommended within 10 feet of any planned settlement/expansion sensitive improvement. Based on our review and engineering analysis, the site belongs to HSG “B” and we recommend “ no infiltration” BMP design. In addition, due to the potential for associated settlement, distress, and perched groundwater for any BMP structure within close proximity (i.e., potentially within 10 feet) of any planned basin to building foundations, retaining walls, slopes, and other settlement-sensitive improvement, a “no infiltration” BMP design is warranted. Furthermore, any basin constructed entirely of compacted fill is considered as belonging to HSG D, and a “no infiltration” BMP design is also warranted (Clar, et al., 2004). Form I-8 and Form I-9 (City of Carlsbad, 2016) are presented in Appendix E. Onsite Infiltration-Runoff Retention Systems General design criteria regarding the use of onsite infiltration-runoff retention systems (OIRRS) are presented below. Should onsite infiltration-runoff retention systems (OIRRS) be planned for Best Management Practices (BMPs) or Low Impact Development (LID) principles for the project, some guidelines should be followed in the planning, design, and construction of such systems. Such facilities, if improperly designed or implemented without consideration of the geotechnical aspects of site conditions, can contribute to flooding, saturation of bearing materials beneath site improvements, slope instability, and possible concentration and contribution of pollutants into the groundwater or storm drain and/or utility trench systems. A key factor in these systems is the infiltration rate (sometimes referred to as the percolation rate) which can be ascribed to, or determined for, the earth materials within which these systems are installed. Additionally, the infiltration rate of the designed system (which may include gravel, sand, mulch/topsoil, or other amendments, etc.) will need to be considered. The project infiltration testing is very site specific, any changes to the location of the proposed OIRRS and/or estimated size of the OIRRS, may require additional infiltration testing. Locally, relatively impermeable residual soils include the underlying bedrock, which is anticipated to have a very low vertical infiltration rate. The following geotechnical guidelines should be considered when designing onsite infiltration-runoff retention systems: •It is not good engineering practice to allow water to saturate soils, especially near slopes or improvements; however, the controlling agency/authority may now require this. GeoSoils, Inc. Cross Real Estate Investors, LLC W.O. 8037-A-SC Tract 80-46, Carlsbad January 27, 2021 File:e:\wp12\8000\8037.pge Page 39 •Areas adjacent to, or within, the OIRRS that are subject to inundation should be properly protected against scouring, undermining, and erosion, in accordance with the recommendations of the design engineer. •Where infiltration systems are located near slopes or improvements, impermeable liners and subdrains should be used along the bottom of bioretention swales/basins located within the influence of such slopes and structures. Impermeable liners used in conjunction with bioretention basins should consist of a 30-mil polyvinyl chloride (PVC) membrane that is covered by a minimum of 12 inches of clean soil, free from rocks and debris, with a maximum 4:1 (h:v) slope inclination, or flatter, and meets the following minimum specifications: Solid Soils Specific Gravity (ASTM D792): 1.2 (g/cc, min.); Tensile (ASTM D882): 73 (lb/in-width, min); Elongation at Break (ASTM D882): 380 (%, min); Modulus (ASTM D882): 32 (lb/in-width, min.); and Tear Strength (ASTM D1004): 8 (lb/in, min); Seam Shear Strength (ASTM D882) 58.4 (lb/in, min); Seam Peel Strength (ASTM D882) 15 (lb/in, min). •Subdrains should consist of at least 4-inch diameter Schedule 40 or SDR 35 drain pipe with perforations oriented down. The drain pipe should be sleeved with a filter sock. •Storm drain, standpipes, and utilities that cross BMPs should be slurried with a 2-sack mix, to 5 feet outside the structure. Final project plans (grading, precise grading, foundation, retaining wall, landscaping, etc.), 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 and/or further geotechnical studies may be warranted. It should be noted that structural and landscape plans were not available for review at this time. DEVELOPMENT CRITERIA Slope Deformation Compacted fill slopes designed using customary factors of safety for gross or surficial stability and constructed in general accordance with the design specifications should be expected to undergo some differential vertical heave or settlement in combination with differential lateral movement in the out-of-slope direction, after grading. This post-construction movement occurs in two forms: slope creep, and lateral fill extension (LFE). Slope creep is caused by alternate wetting and drying of the fill soils which results in slow downslope movement. This type of movement is expected to occur throughout the Storm Water Standards February 2016 Edition Appendices: BMP Design Manual I-3 Appendix I: Forms and Checklists Categorization of Infiltration Condition Form I-8 Part 1 - Full Infiltration Feasibility Screening Criteria Would infiltration of the full design volume be feasible from a physical perspective without any undesirable consequences that cannot be reasonably mitigated? Note that it is not necessary to investigate each and every criterion in the worksheet if infiltration is precluded. Instead a letter of justification from a geotechnical professional familiar with the local conditions substantiating any geotechnical issues will be required. Criteria Screening Question Yes No 1 Is the estimated reliable infiltration rate below proposed facility locations greater than 0.5 inches per hour? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.2 and Appendix D. X Provide basis: Yes. Testing demonstrates that the estimated reliable infiltration rate is 0.87 in/hr, which is greater than 0.5 in/hr Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicability. 2 Can infiltration greater than 0.5 inches per hour be allowed without increasing risk of geotechnical hazards (slope stability, groundwater mounding, utilities, or other factors) that cannot be mitigated to an acceptable level? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.2. No Provide basis: No. This is a 5-lot project. Given the nature of the bedrock, there is a high potential for mounding, nad lateral migration of groundwater, onsite and offsite, to adversely affect existing and proposed improvements, causing distress. Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicability. Storm Water Standards February 2016 Edition Appendices: BMP Design Manual I-4 Page 2 of 4 Criteria Screening Question Yes No 3 Can infiltration greater than 0.5 inches per hour be allowed without increasing risk of groundwater contamination (shallow water table, storm water pollutants or other factors) that cannot be mitigated to an acceptable level? The response to this Screening Question shall be based on a comprehensible evaluation of the factors presented in Appendix C.3. Provide basis: No response required. See Criteria No. 2. Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicability. 4 Can infiltration greater than 0.5 inches per hour be allowed without causing potential water balance issues such as a change of seasonality of ephemeral streams or increased discharge of contaminated groundwater to surface waters? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.3. Provide basis: No response required. See Criteria No. 2. Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicability. Part 1 Result* In the answers to rows 1-4 are “Yes” a full infiltration design is potentially feasible. The feasibility screening category is Full Infiltration If any answer from row 1-4 is “No”, infiltration may be possible to some extent but would not generally be feasible or desirable to achieve a “full infiltration” design. Proceed to Part 2 Proceed to Part 2 * To be completed using gathered site information and best professional judgement considering the definition of MEP in the MS4 Permit. Additional testing and/or studies may be required by [City Engineer] to substantiate findings. Storm Water Standards February 2016 Edition Appendices: BMP Design Manual I-5 Page 3 of 4 Part 2 - Partial Infiltration vs. No Infiltration Feasibility Screening Criteria Would infiltration of water in an appreciable amount be physically feasible without any negative consequences that cannot be reasonably mitigated? Criteria Screening Question Yes No 5 Do soil and geologic conditions allow for infiltration in any appreciable rate or volume? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.2 and Appendix D. X Provide basis: Testing and analyses show the near-surface earth materials have an estimated reliable infiltration rate of roughly 0.87 in/hr in the general vicinity of the proposed BMP. Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicability. 6 Can infiltration in any appreciable quantity be allowed without increasing risk of geotechnical hazards (slope stability, groundwater mounding, utilities, or other factors) that cannot be mitigated to an acceptable level? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.2. X Provide basis: If storm water infiltration into the onsite soils were to occur, there would be an increased potential for shallow perched groundwater conditions (i.e., groundwater mounding) to develop, owing to the collection of water upon the indurated and less permeable unweathered old paralic deposits, which occur at depths ranging between approximately 2 feet and 3 feet below the existing grades, within the project area. Perched groundwater conditions which would adversely affect the performance of the existing and proposed improvements, onsite and offsite, as well as the public right-of-way, and cuase distress, has a high potential to occur. Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicability. Storm Water Standards February 2016 Edition Appendices: BMP Design Manual I-6 Page 4 of 4 Criteria Screening Question Yes No 7 Can Infiltration in any appreciable quantity be allowed without posing significant risk for groundwater related concerns (shallow water table, storm water pollutants or other factors)? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.3. Provide basis: See criteria No. 6 Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicability. 8 Can infiltration be allowed without violating downstream water rights? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.3. Provide basis: Downstream water rights are a legal matter that do not fall under the purview of geotechnical engineering. However, there are no water courses traversing the subject site. See criteria No. 6 Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicability. Part 2 Result* If all answers from row 5-8 are yes then partial infiltration design is potentially feasible. The feasibility screening category is Partial Infiltration. If any answer from row 5-8 is no, then infiltration of any volume is considered to be infeasible within the drainage area. The feasibility screening category is No Infiltration. No Infiltration * To be completed using gathered site information and best professional judgement considering the definition of MEP in the MS4 Permit. Additional testing and/or studies may be required by Agency/Jurisdictions to substantiate findings. Appendix I: Factor of Safety and Design Infiltration Rate Worksheet D-19 February 26, 2016 Factor of Safety Infiltration Rate Worksheet Form I-9 Factor Criteria Factor Description Assigned Weight (w) Factor Value (v) Product (p) p = w x v A Suitability Assessment Soil assessment methods 0.25 1 0.25 Predominant soil texture 0.25 1 0.25 Site soil variability 0.25 1 0.25 Depth to groundwater/impervious layer 0.25 1 0.25 ASuitability Assessment Safety Factor, S = Ep Min = 2.0 B Design Level of pretreatment/expected sediment loads 0.5 Redundancy/resiliency 0.25 Compaction during construction 0.25 BDesign Safety Factor, S = Ep total A BCombined Safety Factor, S = S x S 2.0 min observedObserved Infiltration Rate, inch/hr, K (corrected for test-specific bias)1.74 in/hr design observed totalDesign Infiltration Rate, in/hr, K = K / S 0.87 in/hr Supporting Data Briefly describe infiltration test and provide reference to test forms: See Appendix E of Geotechnical Report by GeoSoils, Inc. (2021).