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Home My WebLink AboutCT 2021-0002; GARFIELD BEACH HOMES; GEOTECHNICAL INVESTIGATION AND INFILTRATION TESTING; 2021-07-14 GEOTECHNICAL INVESTIGATION AND INFILTRATION TESTING Proposed Residential Development 3570 & 3588-3590 Garfield Street Carlsbad, California HETHERINGTON ENGINEERING, INC. July 14, 2021 Project No. 9325.1 Log No. 21469 Rincon Homes/Rincon Real Estate Group 3005 S. El Camino Real San Clemente, California 92672 Attention: Mr. Tom St. Clair Subject: GEOTECHNICAL INVESTIGATION AND INFILTRATION TESTING Proposed Residential Development 3570 & 3588-3590 Garfield Street Carlsbad, California References: Attached Dear Mr. St. Clair: In accordance with your request, we have performed a geotechnical investigation for the proposed twelve, three-story townhome residences at the subject site. Our work was performed during May through July 2021. The purpose of the investigation was to evaluate the geologic and soil conditions at the site in order to provide grading and foundation recommendations for the proposed construction and to provide infiltration rates for use in on-site storm water disposal designs. Our scope of work included the following:  Research and review of readily available geologic literature, geotechnical reports and plans pertinent to the site.  Underground Service Alert mark out and notification.  Subsurface exploration consisting of three borings to depths of 4.5 to 13.5-feet for bulk and relatively undisturbed soil sampling, and geologic logging.  Infiltration testing consisting of two double ring infiltration tests.  Laboratory testing of soil samples obtained during the subsurface exploration.  Engineering and geologic analysis.  Preparation of a report providing the results of our field and laboratory work, analysis and our conclusions and recommendations. SOIL & FOUNDATION ENGINEERING ENGINEERING GEOLOGY HYDROGEOLOGY (760) 931-1917 Fax (760) 931-0545 333 Third Stree Laguna Beach, CA 9265 (949) 715-5440 Fax (949) 715-5442 Carlsbad, CA 92008-43695365 Avenida Encinas, Suite A HETHERINGTON ENGINEERING, INC. www.hetheringtonengineering.com • • • • • • • • GEOTECHNICAL INVESTIGATION AND INFILTRATION TESTING Project No. 9325.1 Log No. 21469 July 14, 2021 Page 2 SITE DESCRIPTION The subject properties are located at 3570 & 3588-3590 Garfield St, Carlsbad, California (see Location Map, Figure 1). The site consists of two relatively flat rectangular shaped parcels. The sites presently support three, single-story single-family structures, 3570 Garfield St on the northern parcel and 3588 & 3590 Garfield St on the southern parcel. The properties are bounded by a single-family residence and condominium complex to the northwest, by a single-family residence to the northeast, by Garfield Street to the southwest and by a single-family residence and multi-family townhomes to the northeast. PROPOSED DEVELOPMENT Proposed development consists of twelve, three-story townhome residences. We anticipate wood-frame and masonry construction founded on conventional continuous/spread footings with raised wood and relatively light slab-on-grade floors. Building loads are expected to be typical for this type of relatively light construction. Grading is expected to consist of cut and fill on the order of approximately 3 to 4-feet. SUBSURFACE EXPLORATION Subsurface conditions were explored by drilling three boreholes to depths of 4.5 to 13.5- feet below existing site grades. The approximate locations of the boreholes are shown on the attached Plot Plan, Figure 2. The subsurface exploration was supervised by an engineer from this office, who visually classified the soil, and obtained bulk and relatively undisturbed samples for laboratory testing. The soils were visually classified according to the Unified Soil Classification System. Classifications are shown on the attached Logs of Borings, Figures 3 through 5. LABORATORY TESTING Laboratory testing was performed on samples obtained during the subsurface exploration. Tests performed consisted of the following:  Dry Density/Moisture Content (ASTM: D 2216)  Maximum Dry Density/Optimum Moisture Content (ASTM: D 1557)  Direct Shear (ASTM: D 3080) HETHERINGTON ENGINEERING, INC. GEOTECHNICAL INVESTIGATION AND INFILTRATION TESTING Project No. 9325.1 Log No. 21469 July 14, 2021 Page 3  Soluble Sulfate (Cal Test 417) Results of the dry density and moisture content determinations are presented on the Logs of Borings, Figures 3 through 5. The remaining laboratory test results are presented on the attached Laboratory Test Results, Figure 6. SOIL AND GEOLOGIC CONDITIONS 1. Geologic Setting The subject site lies within a relatively level marine terrace that is contained within the coastal plain region of northern San Diego County, California. The coastal plain region is characterized by numerous regressive marine terraces of Pleistocene age that have been established above wave-cut platforms of underlying middle Eocene bedrock and were formed during glacio-eustatic changes in sea level. The terraces extend from areas of higher elevation east of the site and descend generally west- southwest in a “stair-step” fashion down to the present day coastline. These marine terraces increase in age eastward. The site area is contained within the southwest portion of the California Department of Conservation San Luis Rey 7-1/2 minute quadrangle (Reference 9). 2. Geologic Units a. Fill/Weathered Terrace Deposits: Fill/weathered terrace deposits were observed to immediately underlie the property to a depth of approximately 3 to 4-feet below existing site grades. The fill/weathered terrace deposits consist generally of damp, medium dense, silty sand. The existing fill/weathered terrace deposits are not considered suitable for support of proposed improvements or compacted fill in their existing condition. b. Terrace Deposits: Underlying the fill/weathered terrace deposits are sediments classified as Pleistocene terrace deposits. These sediments consist generally of damp to moist, medium dense to very dense, silty to slightly clayey silty sand. HETHERINGTON ENGINEERING, INC. GEOTECHNICAL INVESTIGATION AND INFILTRATION TESTING Project No. 9325.1 Log No. 21469 July 14, 2021 Page 4 3. Groundwater Groundwater or seepage was not encountered in the borings to the maximum explored depths explored. Fluctuations in the amount and level of groundwater may occur due to variations in rainfall, irrigation, and other factors that might not have been evident at the time of our field investigation. 4. Infiltration Testing Infiltration testing was performed by this office on May 6 and 7, 2021 in accordance with the Double Ring Infiltrometer Method ASTM D3385, as described in the City of Carlsbad, BMP Design Manual Section D.3.2.3. The locations of the infiltration tests were at or within 50-feet of the proposed bioretention area location. The approximate locations of the infiltration tests are shown on the attached Plot Plan, Figure 2 and test results are shown on the attached Double-Ring Infiltration Test Data sheets, Figures 7 through 10. The infiltration rates based on the infiltration testing are 1.80 inch/hr for I-1 and 2.79 inch/hr for I-2 (without considering factors-of-safety). No groundwater was encountered to the maximum depth of 13.5-feet in the boreholes drilled at the site. Completed worksheet Form I-8 and Form I-9 per the City of Carlsbad BMP Design Manual are attached to this report. SEISMICITY Based on our review of the available geologic maps/literature, there are no active or potentially active faults that traverse the subject site, and the property is not located within the currently mapped limits of an Alquist-Priolo Earthquake Fault Zone. The following table lists the known active faults that would have the most significant impact on the site: Fault Maximum Probable Earthquake (Moment Magnitude) Slip Rate (mm/year) Rose Canyon (4.8-miles/7.7 kilometers southwest)6.9 1.5 Palos Verdes/Coronado Bank (20.5-miles/33.0-kilometers southwest) 7.7 3.0 HETHERINGTON ENGINEERING, INC. GEOTECHNICAL INVESTIGATION AND INFILTRATION TESTING Project No. 9325.1 Log No. 21469 July 14, 2021 Page 5 SEISMIC EFFECTS 1. Ground Accelerations The most significant probable earthquake to affect the property would be a 7.7 magnitude earthquake on the Palos Verdes/Coronado Bank fault. Based on Section 1803.5.12 of the 2016 California Building Code and Section 11.8.3 of ASCE 7-10, peak ground accelerations (PGAM) of 0.540g are possible for the design earthquake. 2. Landsliding Review of the referenced geologic maps/literature indicates that the subject property is not included within the limits of any previously mapped landsliding. The risk of seismically induced landsliding affecting the proposed structures is considered low due to the relatively level topography. 3. Ground Cracks The risk of fault surface rupture due to active faulting is considered low due to the absence of a known active fault on site. Ground cracks due to shaking from seismic events in the region are possible, as with all of southern California. 4. Liquefaction The risk of seismically induced liquefaction within the site is considered low due to the dense nature of the terrace deposits and lack of shallow groundwater. 5. Tsunamis The site is not located within a mapped tsunami inundation area. The risk of a tsunami adversely impacting the site is considered low due to the elevation of the property above sea level. HETHERINGTON ENGINEERING, INC. GEOTECHNICAL INVESTIGATION AND INFILTRATION TESTING Project No. 9325.1 Log No. 21469 July 14, 2021 Page 6 CONCLUSIONS AND RECOMMENDATIONS 1. General The proposed development is considered feasible from a geotechnical standpoint. Grading and foundation plans should take into account the appropriate geotechnical features of the site. Provided that the recommendations presented in this report and good construction practices are utilized during design and construction, the proposed construction is not anticipated to adversely impact the adjacent properties from a geotechnical standpoint. 2. Seismic Parameters for Structural Design Seismic considerations that may be used for structural design at the site include the following: a. Ground Motion - The proposed improvements should be designed and constructed to resist the effects of seismic ground motions as provided in Section 1613 of the 2019 California Building Code and ASCE 7-16. Site Address: 3588 Garfield Street, Carlsbad, CA 92008 Latitude: 33.1519582 N Longitude: 117.3462458 W b. Spectral Response Accelerations - Using the location of the property and data obtained from the SEAOC/OSHPD Seismic Design Maps Program, short period Spectral Response Accelerations Ss (0.2 second period) and S1 (1.0 second period) are: Ss = 1.094g S1 = 0.395g c. Site Class - In accordance with Chapter 20 of ASCE 7, and the underlying geologic conditions, a Site Class D is considered appropriate for the subject property. HETHERINGTON ENGINEERING, INC. GEOTECHNICAL INVESTIGATION AND INFILTRATION TESTING Project No. 9325.1 Log No. 21469 July 14, 2021 Page 7 d. Site Coefficients Fa and Fv - In accordance with Table 1613.3.3 and considering the values of Ss and S1, Site Coefficients for a Class D site are: Fa = 1.062 Fv = null e. Spectral Response Acceleration Parameters Sms and Sm1 - In accordance with Section 1613.3.3 and considering the values of Ss and S1, and Fa and Fv, Spectral Response Acceleration Parameters for Maximum Considered Earthquake are: Sms = 1.162g Sm1 = null f. Design Spectral Response Acceleration Parameters Sds and Sd1 - In accordance with Section 1613.3.4 and considering the values of Sms and Sm1, Design Spectral Response Acceleration Parameters for Maximum Considered Earthquake are: Sds = 0.775g Sd1 = null g. Long Period Transition Period - A Long Period Transition Period of TL = 8 seconds is provided for use in San Diego County. h. Seismic Design Category - In accordance with Tables 1604.5, 1613.3.5(1) and 1613.3.5(2), and ASCE 7, a Risk Category II and a Seismic Design Category D are considered appropriate for the subject property. 3. Site Grading Prior to grading, areas of proposed improvements should be cleared of existing surface improvements, obstructions, vegetation and debris. Materials generated during clearing should be disposed of at an approved location off-site. Holes resulting from the removal of buried obstructions should be filled with compacted fill or lean concrete. Seepage pits and/or septic systems, if encountered during site development, should be abandoned in accordance with local guidelines. Within the limits of proposed improvements and to 3-feet beyond, any existing fill/weathered paralic deposits should be removed down to approved undisturbed paralic deposits. We anticipate removal depths on the order of 3 to 4-feet below HETHERINGTON ENGINEERING, INC. GEOTECHNICAL INVESTIGATION AND INFILTRATION TESTING Project No. 9325.1 Log No. 21469 July 14, 2021 Page 8 existing site grades. Actual removal depths should be determined in the field by the Geotechnical Consultant based on conditions exposed during grading. Following removals, the exposed surface soils should be scarified to a depth of 6 to 8- inches, moisture conditioned to about optimum moisture content and compacted to at least 90-percent relative compaction (ASTM: D 1557). Fill should be moisture conditioned to about optimum moisture content and compacted by mechanical means in uniform horizontal lifts of 6 to 8-inches in thickness. All fill should be compacted to a minimum relative compaction of 90- percent based upon ASTM: D 1557. The on-site materials are suitable for use as compacted fill provided all vegetation and debris are removed. Rock fragments over 6-inches in dimension and other perishable or unsuitable materials should be excluded from the fill. All grading and compaction should be observed and tested as necessary by the Geotechnical Consultant. 4. Foundation and Slab Recommendations The proposed improvements should be supported on conventional continuous/spread footings founded at least 18-inches into compacted fill and/or approved terrace deposits. Continuous footings should be at least 12-inches wide, and reinforced with a minimum of four #4 bars, two top and two bottom. Foundations located adjacent to utility trenches should extend below a 1:1 (horizontal to vertical) plane projected upward from the bottom of the trench. Foundations bearing as recommended may be designed for a dead plus live load bearing value of 2000-pounds-per-square-foot. This value may be increased by one- third for loads including wind and seismic forces. A lateral bearing value of 250- pounds-per-square-foot per foot of depth and a coefficient of friction between foundation soil and concrete of 0.35 may be assumed. These values assume that footings will be poured neat against the foundation soils. Footing excavations should be observed by the Geotechnical Consultant prior to the placement of reinforcing steel in order to verify that they are founded in suitable bearing materials. Total and differential settlement due to foundation loads is considered to be less than 3/4 and 3/8-inch, respectively, for foundations founded as recommended. HETHERINGTON ENGINEERING, INC. GEOTECHNICAL INVESTIGATION AND INFILTRATION TESTING Project No. 9325.1 Log No. 21469 July 14, 2021 Page 9 Slab-on-grade floors should have a minimum thickness of 5-inches and should be reinforced with #4 bars spaced at 18-inches, center-to-center, in two directions, and supported on chairs so that the reinforcement is at mid-height in the slab. Floor slabs should be underlain with a moisture vapor retarder consisting of a minimum 15-mil membrane. At least 2-inches of sand should be placed over the vapor retarder to assist in concrete curing and at least 2-inches of sand should be placed below the vapor retarder. The vapor retarder should be placed in accordance with ASTM: E 1643. Prior to placing concrete, the slab subgrade soils should be thoroughly moistened. Vapor retarders are not intended to provide a waterproofing function. Should moisture vapor sensitive floor coverings be planned, a qualified consultant/contractor should be consulted to evaluate moisture vapor transmission rates and to provide recommendations to mitigate potential adverse impacts of moisture vapor transmissions on the proposed flooring. 5. Sulfate Content A representative sample of the on-site soil was submitted for sulfate testing. The results of the sulfate content test are summarized on the Laboratory Test Results, Figure 6. The sulfate content is consistent with a not applicable (S0) sulfate exposure classification per Table 4.2.1 of the American Concrete Institute Publication 318, consequently, no special provisions for sulfate resistant concrete are considered necessary. Other corrosivity testing has not been performed, consequently, on-site soils should be assumed to be severely corrosive to buried metals unless testing is performed to indicate otherwise. 6. Retaining Walls Retaining wall foundations should be designed in accordance with the foundation recommendations provided previously in this report. Retaining walls free to rotate (cantilevered walls) should be designed for an active pressure of 35-pounds-per- cubic-foot (equivalent fluid pressure). Walls restrained from movement at the top should be designed for an at-rest pressure of 55-pounds-per-cubic-foot (equivalent fluid pressure). These values are based on level backfill consisting of onsite granular soils. Any additional surcharge pressures behind retaining walls should be added to these values. HETHERINGTON ENGINEERING, INC. GEOTECHNICAL INVESTIGATION AND INFILTRATION TESTING Project No. 9325.1 Log No. 21469 July 14, 2021 Page 10 Retaining walls should be provided with adequate drainage to prevent buildup of hydrostatic pressure and should be adequately waterproofed. The subdrain system behind retaining walls should consist at a minimum of 4-inch diameter Schedule 40 (or equivalent) perforated (perforations “down”) PVC pipe embedded in at least 1- cubic-foot of 3/4-inch crushed rock per lineal foot of pipe all wrapped in an approved filter fabric. The subdrain system should be connected to a solid outlet pipe with a minimum of 1-percent fall that discharges to a suitable drainage device. Recommendations for wall waterproofing should be provided by the Project Architect and/or Structural Engineer. The lateral pressure on retaining walls due to earthquake motions (dynamic lateral force) should be calculated as PA = 3/8 γ H2kh where PA = dynamic lateral force (pounds/foot) γ = unit weight = 110-pounds-per-cubic-foot H = height of wall (feet) kh = seismic coefficient = 0.18 The dynamic lateral force may also be expressed as 15-pounds-per-cubic-foot (equivalent fluid pressure). The dynamic lateral force is in addition to the static force and should be applied as a triangular distribution at 1/3H above the base of the wall. The dynamic lateral force need not be applied to retaining walls 6-feet or less in height. 7. Temporary Slopes Temporary slopes necessary to facilitate construction may be cut vertically in terrace deposits up to 5-feet where the cuts are not influenced by existing property line constraints or structures/improvements. Temporary slopes near existing structures/improvements/property lines, over 5-feet in height, and/or cuts exposing fill should be inclined at a slope ratio no steeper than 1:1 (horizontal to vertical) or shored. Field observations by the Engineering Geologist during grading of temporary slopes are recommended and considered necessary to confirm anticipated conditions and provide revised recommendations if warranted. Shoring recommendations can be provided on request. HETHERINGTON ENGINEERING, INC. GEOTECHNICAL INVESTIGATION AND INFILTRATION TESTING Project No. 9325.1 Log No. 21469 July 14, 2021 Page 11 8. Retaining Wall and Utility Trench Backfill All retaining wall and utility trench backfill should be compacted to at least 90- percent relative compaction (ASTM: D 1557). Backfill should be tested and observed by the Geotechnical Consultant. 9. Site Drainage The following recommendations are intended to minimize the potential adverse effects of water on the structures and appurtenances. a. Consideration should be given to providing the structures with roof gutters and downspouts that discharge to an area drain system and/or to suitable locations away from the structure. b. All site drainage should be directed away from the structures. c. No landscaping should be allowed against buildings. Moisture accumulation or watering adjacent to foundations can result in deterioration of building materials and may effect foundation performance. d. Irrigated areas should not be over-watered. Irrigation should be limited to that required to maintain the vegetation. Additionally, automatic systems must be seasonally adjusted to minimize over-saturation potential particularly in the winter (rainy) season. e. All yard and roof drains should be periodically checked to verify they are not blocked and flow properly. This may be accomplished either visually or, in the case of subsurface drains, by placing a hose at the inlet and checking the outlet for flow. 10. Recommended Observation and Testing During Construction The following tests and/or observations by the Geotechnical Consultant are recommended: a. Observation and testing of grading. b. Foundation excavations prior to placement of forms and reinforcement. HETHERINGTON ENGINEERING, INC. GEOTECHNICAL INVESTIGATION AND INFILTRATION TESTING Project No. 9325.1 Log No. 21469 July 14, 2021 Page 12 c. Utility trench backfill. d. Retaining wall backdrains and backfill. 11. Grading and Foundation Plan Review Grading and foundation plans should be reviewed by the Geotechnical Consultant to confirm conformance with the recommendations presented herein or to modify the recommendations as necessary. LIMITATIONS The analyses, conclusions and recommendations contained in this report are based on site conditions as they existed at the time of our investigation and further assume the excavations to be representative of the subsurface conditions throughout the site. If different subsurface conditions from those encountered during our exploration are observed or appear to be present in excavations during construction, the Geotechnical Consultant should be promptly notified for review and reconsideration of recommendations. Our investigation was performed using the degree of care and skill ordinarily exercised, under similar circumstances, by reputable Geotechnical Consultants practicing in this or similar localities. No other warranty, express or implied, is made as to the conclusions and professional advice included in this report. This opportunity to be of service is sincerely appreciated. If you have any questions, please call this office. Sincerely, HETHERINGTON ENGINEERING, INC. Mark D. Hetherington Edwin R. Cunningham Civil Engineer 30488 Civil Engineer 81687 Geotechnical Engineer 397 (expires 3/31/22) (expires 3/31/22) HETHERINGTON ENGINEERING, INC. GEOTECHNICAL INVESTIGATION AND INFILTRATION TESTING Project No. 9325.1 Log No. 21469 July 14, 2021 Page 13 Daniel Eisele Engineer-in-Training Attachments: Location Map Figure 1 Plot Plan Figure 2 Logs of Test Pits Figures 3 through 5 Laboratory Test Results Figure 6 Double-Ring Infiltration Test Data Figures 7 through 10 Forms I-8 and I-9 Distribution: 1-via e-mail Tom St. Clair (tstclair@rincongrp.com) 4-Addressee HETHERINGTON ENGINEERING, INC. ftr& REFERENCES Project No. 9325.1 Log No. 21469 1) American Society of Civil Engineers/Structural Engineers Institute, "Minimum Design Loads for Buildings and Other Structures,” ASCE 7-10, dated May 2010. 2) California Geological Survey, "Tsunami Inundation Map for Emergency Planning- San Luis Rey Quadrangle," dated June 1, 2009. 3) ICBO, California Building Code, 2016 Edition. 4) Stephen Dalton Architects, Floor Plans, dated May 24, 2021 (Sheets A2-1, A2-2, A2- 3). 5) Peterson, Mark P., et al, “Documentation for the 2008 Update of the United States National Seismic Hazards Maps,” USGS Open File Report 2008-1128, dated 2008. 6) SEAOC/OSHPD Seismic Design Maps Website. 7) Tan, Siang S. and Kennedy, Michael P., "Geologic Maps of the Northwestern Part of San Diego County, California," California Division of Mines and Geology, Open-File Report 96-02, dated 1996. 8) Tan, Siang S. and Giffen, Desmond G., "Landslide Hazards in the Northern Part of the San Diego Metropolitan Area, San Diego, California," California Division of Mines and Geology, Open File Report 95-04, dated 1995. 9) California Department of Conservation- Division of Mines and Geology, "Geologic Maps of the Northwestern Part of San Diego County, California- Plate 1," dated 1996. 10) United States Geological Survey, "San Luis Rey Quadrangle- San Diego County 7.5- Minute Series,“ dated 2015. 11) “City of Carlsbad, BMP Design Manual”, dated 2016. HETHERINGTON ENGINEERING, INC. ADAPTED FROM: The Thomas Guide, San Diego County, 57th Edition, Page 1106 N SCALE: 1" -2000' (1 Grid Equals: 0.5 x 0.5 miles) LOCAT ION MAP HETHERINGTON ENGINEERlf\JG, INC . GEOTECHNICAL CONSULTANTS 3570 & 3588-90 Garfield Street Carlsbad, California PROJECT NO. 9325.1 I FIGURE NO. 1 2 N 012 20 40010 30 SCALE: 1" = 20' LEGEND APROXIMATE LOCATION OF INFILTRATION TESTINGI-2 APROXIMATE LOCATION OF BORINGB-2 B-1 I-2 I-1 GA R F I E L D S T R E E T 3570 GARFIELD 3590 GARFIELD PLOT PLAN GEOTECHNICAL CONSULTANTS HETHERINGTON ENGINEERING,INC. PROJECT NO. FIGURE NO.9325.1 3570 & 3588-90 Garfield StreetCarlsbad, California APROXIMATE LOCATION OF HAND AUGER BORINGHA-1 HA-1 B-2 DRILLING COMPANY: Native Drilling RIG: Tripod DATE: 05/07/21 BORING DIAMETER: 6" DRIVE WEIGHT: 150 lbs. DROP: 30" ELEVATION: I + -ril E-i ril H :,-, -ril H P< E-i E-i o'P (/) -ril P< ~ 0 H -(/) BORING NO. 8-1 r.,., ~ 0 (/) ril et:(/) -(/) r.,., z p:; E-i H ::r: (/) ----- ril D z u u ril (/) 0 -E-i ril E-i :,c: > ts lH (/) E-i H (I) P< H H 0 :,-, 0 H z H ril D p:; H p:; p, 0 0 0 D 0 P'.l 0 P'.l 0 -::,:: u (/) -SOIL DESCRIPTION -0.0 WEATHERED TERRACE DEPOSITS: Light red brown silty sand, damp, medium dense, contains organics -x - 5/6" 93 3.9 SM 10/6" 13/6" - -~ 7/6" 119 3.7 TERRACE DEPOSITS: Orange brown silty sand, damp to 26/6" moist, dense to very dense -~ 39/6" - 5.0-I -50/6" 104 5.2 -- -~ - -- -- 10.0-~ -13/6" 107 4.1 24/6" -35/6" - --17/6" 116 4.7 23/6" -28/6" - ~ -Total Depth = 13.5-feet -No Seepage 15.0-No Caving - -- -- -f-- -- 20.0 BORING LOG 3570 & 3588-90 Garfield Street HETHERINGTON ENGINEERING, INC. Carlsbad, California GEOTECHNICAL CONSULTANTS PROJECT NO. 9325.1 I FIGURE NO. 3 DRILLING COMPANY: Native Drilling RIG: Tripod DATE: 05/07/21 BORING DIAMETER: 6" DRIVE WEIGHT: 150 lbs. DROP: 30" ELEVATION: I + -fil E---l fil ,-:i ;>-1 -fil ,-:i /:1, E---l E---l dP {/J -fil /:1, ~ 0 H -{/J BORING NO. B-2 fr., -~ 0 {/J fil ei: {/J {/J fr., z p:; E---l ,-:i ::r:: {/J '---fil :::> z u u fil {/J 0 -E---l fil E---l ~ > :s 4-l {/J E---l ,-:i {fJ /:1, ,-:i H 0 ;>-1 0 H z H fil :::> p:; ,-:i p:; °' 0 0 0 :::> 0 o::i 0 o::i 0 -:;;: u {/J -SOIL DESCRIPTION ~ 0.0 SM TOPSOIL: Light brown silty sand, dry to damp, loose to medium dense, contains organics r -~ WEATHERED TERRACE DEPOSITS: Light orange brown - 5/6" 109 4.6 5/6" silty sand, damp, medium dense, contains organics -10/6" - SM -- -~ 8/6" 110 4.9 TERRACE DEPOSITS: Red brown to tan silty slightly clayey 11/6" sand, damp to moist, medium dense to dense 5.0-16/6" - 15/6" 116 7.0 --25/6" -40/6" -I - -- -\ - 10.0---16/" 108 4.2 @10': Light beige to orange to grey sand, damp, medium 26/6" dense -31/6" - f---- -Total Depth = 11.5-feet - No Seepage No Caving -- -- 15.0-- -- -- -- -- 20.8 BORING LOG 3570 & 3588-90 Garfield Street HETHERINGTON ENGINEERING, INC. Carlsbad, California GEOTECHNICAL CONSULTANTS PROJECT NO. 9325.1 I FIGURE NO. 4 DRILLING COMPANY: Native Drilling RIG: Tripod DATE: 05/07/21 BORING DIAMETER: 6" DRIVE WEIGHT: 150 lbs. DROP: 30" ELEVATION: I + -fil E---< fil H >-< -fil H 04 E---< E---< 0\0 UJ -fil 04 ~ 0 H -UJ BORING NO. HA-1 Ii-, ~ 0 UJ fil ei; UJ -UJ Ii-, z pc; E---< H :r:: UJ ------ fil b z u u fil UJ 0 -E---< fil E---< :,,:; :> :s 4---l UJ E---< ,-:i UJ 04 H H 0 >-< 0 H z H fil b pc; H pc; °' 0 0 0 b 0 i:o 0 i:o 0 -:8 u UJ -SOIL DESCRIPTION ,_ 0.0 WEATHERED TERRACE DEPOSITS: Red brown to tan silty slightly clayey sand, damp to moist, medium dense -<-- -<-- SM -<-- 7/6" 111 4.3 11/6" -15/6" 1-- ~ 5.0-Total Depth = 4.5-feet --No Seepage No Caving -Note: Hand Auger directly next to B-2 to recover missing drive ~ sample at 3'. Same conditions encountered to 3' as in B-2. -~ -~ -~ 10.0-1-- -<-- -'-- -'-- -<-- 15.0--- -~ -~ -~ -~ 20.v BORING LOG 3570 & 3588-90 Garfield Street HETHERINGTON ENGINEERING, INC. Carlsbad, California GEOTECHNICAL CONSULTANTS PROJECT NO. 9325.1 I FIGURE NO. 5 LABORATORY TEST RESULTS Figure 6 Project No. 9325.1 Log No. 21469 DIRECT SHEAR (ASTM: D 3080) Sample Location Angle of Internal Friction (º) Cohesion (psf) Remarks B-1 @ 1’ to 3’ 34 75 2.5 – in. ring, remolded to 90%, soaked, consolidated, drained SULFATE TEST RESULTS (CAL 417) Sample Location Soluble Sulfate in Soil (%) B-1 @ 1’ to 3’ 0.0022 MAXIMUM DRY DENSITY/OPTIMUM MOISTURE CONTENT (ASTM: D 1557A) Sample Location Description Maximum Dry Density (pcf) Optimum Moisture Content (%) B-1 @ 1’ to 3’ Dark brown silty sand 125.5 10.0 HETHERINGTON ENGINEERING, INC. I I Project No. 9325.1 Project Name: 3570 Garfield 167.53 11 :00 0:12 0.00 3039.94 6366.1 6.572 4.583 11: 13 0:10 57.80 35.00 58.4 27.1 11 :23 0:22 22.80 1873.20 31 .3 4540.1 4.050 3.269 11 :29 0:10 58.00 20.80 58.4 26.3 11 :39 0:32 37.20 1113.22 32.1 4406 2.407 3.172 11 :45 0:15 57.90 41.90 58 58 12:00 0:47 16.00 2242.49 0 9716.7 4.848 6.996 12:09 0:15 57.50 35.00 58 30 12:24 1 :02 22.50 1873.20 28 5025.9 2.025 3.618 12:32 0:15 57.00 35.00 57 .5 41 .2 12:47 1 :17 22.00 1873.20 16.3 6902.2 2.025 4.969 12:52 0:15 57.90 10.80 58 .5 26.8 13:07 1 :32 47.10 578.02 31.7 4489.8 0.312 0.808 13:10 0:15 57.90 12.10 58 .3 28.8 13:25 1 :47 45.80 647.59 29.5 4824.9 0.015 0.037 13:30 0:15 58.00 10.30 58 25 13:45 2:02 47.70 551.26 33 4188.3 0.015 0.038 13:48 0:15 47.70 11.20 58 .5 21 14:03 2:17 36.50 599.42 37.5 3518.1 1.296 2.533 14:05 0:15 58.00 17.20 58 44.4 14:20 2:32 40.80 920.54 13.6 7438.3 1.990 5.355 14:29 0:15 57.80 36.10 57.3 47.3 14:44 2:47 21.70 1932.07 10 7924.2 4.177 5.705 14:56 0:15 56.20 23.80 57.4 33.4 15: 11 3:02 32.40 1273.78 24 5595.5 2.754 4.029 15:16 0:15 58.00 4.30 58.2 33.9 15:31 3:1 7 53.70 230.14 24.3 5679.3 0.498 4.089 15:35 0:15 53.70 14.30 57 .2 32.4 '15:50 3:32 39.40 765.34 24.8 5428 1.655 3.908 15:55 0 15 39.40 15 .20 58 .5 26.5 16:10 3:47 24.20 813.50 32 4439.5 1.759 3.196 16:1 3 0:15 57.50 20.00 57.3 23 .9 16:28 4:02 37.50 1070.40 33.4 4004 2.314 2.883 *Flow, Qf=~HxVr **Infiltration Rate, l=(Qf/Ar)/M Figure No. 7 Project No. 9235.1 Log No. 21469 >-.. ..c 7 6 s "? 4 ~ ro er: C .g ro ~ 3 ~ C 2 1 Infiltrati on Rat e vs Time o e---------'--------L---=~------'------------'---------'---------' 0 so 100 150 Elapsed Time (min) 200 250 300 -+-Inner Ring -+-Annular Ring Figure No. 8 Project No. 9235.1 Log No. 21469 -41 ...., ';'J ~."i:..~ •• mF.,J;u~-120UBl!ERING INEIJ.;:JJIRQMHEgtJl:.SJIDAif_ki ;=;: ... ;. g ,;;a;;;;rHJ,mi erojecf rsJatne ana~est cocation· H =•~~ j;I = =-=-ERin§ Dat~ "Cbniairfars~· l~'.M,' ,~ ·,;;o•-· ,.~'-=,---=--'C,: -,cl"-~' ·...c• " !!'I-.... R _ l:I . =-~ I ·;.., :l-='!!:~ ~';, .,·•• .;i ~~ .. " ~~~ . ,. ""'"di ..}_ iialil Project No. 9325.1 ! --Area,~Ar Qeotln of Project Name: 3570 Garfield :*--,., ~(~r:ri2),i; li.igwid (i.D )1 _!'Jstbt...L. ,..JfJ!:J 1'G,il)!,)li Location: 1-2 ~Dl!_Lll.-729 6 1 53.52 ,Nst-~"Q B. R. l"~~~i'• ~ a --_ifpac;e:' 2189 6 2 167.53 wli1etr aole DE!Stm -P~netrl tici'A'of RingsJrifo S011@1 :~' ltmer: CDuie-r:~ =" === =lii== ·~ ~ Grour,id,; =~~ I;,=!~ ~ " ~-" feate7uf-Tw ~ ~ --· .lei 1□. .,, 5/7/2021 ~d. --H20 tth '?fi:l"f!R"t:H"'l--f-'Pl. ~ Ligiuid Level Ma1otainetl oy using:= -="',_ " ( ) Flow Valve () Float Valve (X) Marriotte Tube () Other: 1• _ A~dftio_nal: 11. _ ,L,omme~.ts_:i!::; ~ : ='-:~ ~ .. 11 l,;ir~er R,ir:rg JI t, =Armular;-Ring ~~~ IQfilfration l:\ate)11*1. l=ib f~ 1.;;; " -"' II' or, ' ..,. ~· A~ .. -,, ~7=ir,me = "'t · ::~ Dt (min) &~ Elev.,'-;R 'Ii ~H <1wl -s~e::, ~f lin) &'1. ~biqui "" l'Ven,arkis !!l'le ' =-_=ii"_ Ou~~r -' .-.--~ffii -ir"ltewal= ~ c,, ~ IJ~Q~r,,1r;i/11f' U:,JQYhr~: (l1r:min), . u:::1ota1 ~ ~ml~ ~ ~~ -t:1,-(cr.n) Y (ml) tremp "f:i ,adb-';;:;: ==== ;Jr ~:;;;ta rt 9:28 0:15 57.70 56.50 58 46.9 ~~ 9:43 0:15 1.20 3023.88 11.1 7857.2 6.537 5,657 "' 2 -Sfaff 9:50 0:15 58.30 52.20 57.6 40.4 ==-Erta 10:05 0:30 6.10 2793.74 17.2 6768.2 6.040 4.873 .:;1,--Sfart 10: 11 0:14 57.00 57.00 58.4 32.6 ... r:;a:a 10:25 0:44 0.00 3050.64 25.8 5461.5 6.595 3.932 ~4 -Start-10:31 0:15 58.00 27.80 58.3 30.3 =, Er,id 10:46 0:59 30.20 1487.86 28 5076.2 3.217 3.655 ..,!ll . s tart 10:51 0:15 57.80 18.40 58.2 23.7 ~11'.\Z:I 11 :06 114 39 .40 984.77 34.5 3970.5 2.129 2.859 ti5 --Stai;t 11 :13 0:15 58 .00 50.00 58.3 39 -=' Enq 11 :28 1 :29 8.00 2676.00 19.3 6533.7 5.785 4.704 ~~1aJf 11 :44 0:1 5 58 .00 27.00 57.3 15.4 -_l_li;;'.n rl 11 :59 1 :44 31.00 1445.04 41.9 2580 3.124 1.857 ~g -Sfart 12:04 0:15 58 .00 26.00 58 .3 32.3 Eric! 12:19 1 :59 32.00 1391 .52 26 541 1.2 3.008 3.896 ; 9 '~ Stari 12:25 0:15 56.00 33.80 58.1 31,5 ~Eiid: 12:40 2:14 22.20 1808.98 26.6 5277.2 3.91 1 3.799 l G\---Stan 12:45 0:15 58.20 15.70 58.5 33.5 1= ~End 13:00 2:29 42.50 840.26 25 5612.3 1.817 4.041 ia:,,11--S taJi 13:07 0:15 42.50 21 .00 58 35.5 .... ...-c r:iG(, 13:22 2:44 21 .50 1123.92 22.5 5947.3 2.430 4.282 ;:;1 as -s r:;u:ii 13:29 0:15 58.00 30.60 58.4 31 """' t:nd 13:44 2:59 27.40 1637.71 27.4 5193.4 3.541 3.739 1""13 ~.,.~_tact 13:48 0:15 58.20 19.20 57.5 28 .3 ~~i:i]l 14:03 3:14 39.00 1027.58 29.2 4741.1 2.221 3.413 ,-1-¾~ 1 Sfait 14:14 0:15 57.40 20.00 58.3 33.8 1== EnGI 14:29 3:29 37.40 1070.40 24,5 5662.5 2.314 4.077 1-,Mii~-Sta11 14:33 0:15 37.40 10.20 58.5 25 ~~rid 14:48 3:44 27.20 545.90 33.5 4188.3 1.180 3.015 ii@-;;, Start 14:49 0:15 27.20 27.20 33.5 33.5 "" End 15:04 3:59 0.00 1455.74 0 5612.3 3.147 4.041 ,;1..7 ,..::;tali 15:10 0:15 58.20 32.80 58.5 32.1 ~-::; r-:.nij 15:25 4:14 25.40 1755.46 26.4 5377.7 3.795 3.872 ,.18 -Start 15:30 o:·I5 25.40 20.40 58.5 31 ""=;: End 15:45 4:29 5.00 1091 .81 27.5 5-193.4 2.360 3.739 19 -Star:! 15:50 0:15 58.00 32.50 58.5 27.3 -..;-... -c~_d, 16:05 4:44 25.50 1739.40 31.2 4573.6 3.760 3.293 *Flow, Qf=~HxVr **Infiltration Rate, l=(Qf/Ar)/~t Figure No. 9 Project No. 9235.1 Log No. 21469 Infiltration Rat e vs Tim e 8 7 6 5 '-..c ---C _;!; ro cc 4 ! 11 ii\ I \I\ ! I\ I ~\I )} I -e-lnner Ring -e-Annular Ring c;:::: C 3 2 1 o-------~-------~------~-------~------~---------' 0 50 100 150 Elapsed Time (min) 200 250 300 Figure No. 1 O Project No. 9235.1 Log No. 21469 Categorization of Infiltration Feasibility Form I-8 Condition 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? Criteria Screening Question 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 Appendi." D. Yes No X Provide basis: Two infiltration tests using the Double Ring lnfiltrometer test method were performed in the weathered paralic deposits. The test results were 1.80 inch/hr and 2.79 inch/hr (without considering safety factors). See "Geothechnical Investigation and Infiltration Testing ... ", by Hetherington Engineering, Inc., dated July 14, 2021. Summarize findings of studies; provide reference to srudies, calculations, maps, data sources, etc. Provide narrative discussion of study/ data source applicabili t:y. 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. X Provide basis: On-site infiltration is considered acceptable from a geotechnical standpoint provided that the geotechnical recommendations included in the "Geotechnical Investigation ... " are implemented during design and construction. Summarize findings of srudies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/ data source applicability. Criteri a 3 Form I-8 Page 2 of 4 Screening Question 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 comprehensive evaluation of the factors presented in Appencli., C.3. Yes No X Provide basis: On-site storm water pollutant concerns are unknown at this time. The test pits at the site with a maximum depth of 13.5-feet did not encounter groundwater. Infiltrated water will migrate at least X-feet before reaching groundwater. In addition, we are not aware of any known soil contamination present. 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 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. X Provide basis: No ephemeral streams are present at the site. Groundwater was not encountered to a depth of at least 13.5-feet and we are not aware of any contaminated groundwater in t11e site vicinity. Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/ data source applicability. Part 1 Result * If all 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 Full Infiltration *To be con1p1eted using gathered site infom1at1on and best professional judgment cons1denng the definition of NIEP 111 the £1'1S4 Permit. Additional testing and/or studies may be required by the City to substantiate findings. Factor of Safety and Design Infiltration Rate Worksheet Form 1-9 Factor Category Factor Description Assigned Factor Product (p) \'{'eight (w) Value (v) p=wxv Soil assessment methods 0.25 1 0.25 Predominant soil texture 0.25 1 0.25 Suitability Site soil variability 0.25 1 0.25 A Assessment Depth to groundwater I impervious 0.25 2 0.50 layer Suitability Assessment Safety Factor, SA = 1:p 1.25 Level of pretreatment/ expected 0.5 0.5 sediment loads 1 B Design Redundancy/ resiliency 0.25 1 0.25 Compaction during constrnction 0.25 3 0.75 Design Safety Factor, SB = 1:p 1.50 Combined Safety Factor, Smc-tl= st\ X SB 2.75 Observed Infiltration Rate, inch/hr, l(,,b,en·cd 1-1 and 1-2= (corrected for test-specific bias) 2.3-inch/hr. (ave) Design Infiltration Rate, in/hr, Kdcsign = l(,,b,crvcd / Srornl 1-1 and 1-2 = 0.8-inch/hr. (ave) Supporting Data Briefly describe infiltration test and provide reference to test forms: Two Double Ring lnfiltrometer infiltration tests were performed. See "Geotechnical Investigation and Infiltration Testing .. " by Hetherington Engineering, Inc., dated July 14, 2021 . November 4, 2021 Project No. 9325.1 Log No. 21669 Rincon Homes/Rincon Real Estate Group 3005 S. El Camino Real San Clemente, California 92672 Attention: Mr. Tom St. Clair Subject: REVISED I-9 FORM Infiltration Testing Proposed Residential Development 3570 & 3588-3590 Garfield Carlsbad, California Dear Mr. St. Clair: In response to the request of Bryan Knapp, Pasco Laret Suiter and Associates, we are providing a revised Form I-9 (see attached). The combined safety factor, Stotal is revised from 1.875 to 2.0. The Design Infiltration Rate, Kdesign is revised from 0.8 to 1.15 inches/hour. This opportunity to be of service is appreciated. If you have any questions, please contact our Carlsbad office. Sincerely, HETHERINGTON ENGINEERING, INC. Edwin R. Cunningham Mark D. Hetherington Civil Engineer 81687 Civil Engineer 30488 (expires 3/31/22) Geotechnical Engineer 397 (expires 3/31/22) Attachments: Form I-9 Distribution: 1-via e-mail (tstclair@rincongrp.com) 1-via e-mail (bknapp@plsaengineering.com) SOIL & FOUNDATION ENGINEERING ENGINEERING GEOLOGY HYDROGEOLOGY (760) 931-1917 Fax (760) 931-0545 333 Third Street Laguna Beach, CA 92651 (949) 715-5440 Fax (949) 715-5442 Carlsbad, CA 92008-43695365 Avenida Encinas, Suite A HETHERINGTON ENGINEERING, INC. www.hetheringtonengineering.com • • • • • • • • Factor of Safety and Design Infiltration Rate Worksheet Form I-9 Factor Category Factor Description Assigned Weight (w) Factor Value (v) Product (p) p = w x v A Suitability Assessment Soil assessment methods 0.25 Predominant soil texture 0.25 Site soil variability 0.25 Depth to groundwater / impervious layer 0.25 Suitability Assessment Safety Factor, SA = p B Design Level of pretreatment/ expected sediment loads 0.5 Redundancy/resiliency 0.25 Compaction during construction 0.25 Design Safety Factor, SB = p Combined Safety Factor, Stotal= SA x SB Observed Infiltration Rate, inch/hr, Kobserved (corrected for test-specific bias) Design Infiltration Rate, in/hr, Kdesign = Kobserved / Stotal Supporting Data Briefly describe infiltration test and provide reference to test forms: GEOTECHNICAL | ENVIRONMENTAL | MATERIAL September 22, 2022 Project No. 3830-SD Rincon Homes 5315 Avenida Encinas, Suite 200 Carlsbad, California 92008 Attention: Mr. Tom St. Clair Subject: Response to Third-Party Geotechnical Review Comments Proposed Residential Development 3750 & 3588-3590 Garfield Street Carlsbad, California Reference: See Page 6 Dear Mr. St. Clair: As requested, by Bryan Knapp, Pasco Laret Suiter & Associates (PLSA), GeoTek, Inc., (GeoTek) has prepared this letter to provide a supplemental respond to City of Carlsbad third-party review comments of the “Geotechnical Investigation and Infiltration Testing, Proposed Residential Development, 3570 & 3588-3590 Garfield Street, Carlsbad, California, Project No. 9325.1” by Hetherington Engineering, Inc. (HEI), dated July 14, 2021 and “Grading Plans For: 3570 Garfield Street, Project No. CT 2021-0002” by Pasco Laret Suiter & Associates, dated 2022 (sheets 1 through 8). Our numbering corresponds to that used by the reviewer. Review Comment No. 1 The Geotechnical Consultant should review the project grading and foundation plans and provide any additional geotechnical recommendations, as appropriate, and indicate if the plans have been prepared in accordance with the geotechnical recommendations provided in the referenced geotechnical report (Hetherington Engineering, Inc., 2021). Response to Review Comment No. 1 We have reviewed the project grading and foundation plans. The grading and foundation plans have incorporated the geotechnical recommendations provided in the referenced geotechnical report (Hetherington Engineering, Inc., 2021) and are considered suitable from a geotechnical standpoint. The conclusions and recommendations provided in the geotechnical report (Hetherington Engineering, Inc., 2021) remain applicable to the referenced grading and foundation plans. GeoTek, Inc. 1384 Poinsettia Avenue, Suite A Vista, CA 92081-8505 (760) 599-0509 Office (760) 599-0593 f;i www.geotekusa.com RINCON HOMES Project No. 3830-SD Garfield Beach Homes September 22, 2022 3570 Garfield Street, Carlsbad, California Page 2 Review Comment No. 2 The Geotechnical Consultant should provide a geotechnical cross-section(s) of the site or discussion as to why one is not presented. If a geologic cross section is prepared, an updated geotechnical map/plot plan showing the location of the cross-section should be provided. Response to Review Comment No. 2 We have provided an updated geotechnical map/plot plan as Figure 1and a geologic cross section as Figure 2. Review Comment No. 3 The Geotechnical Consultant should provide a geotechnical map/plot plan to clearly show the limits of the proposed structures and the lateral limits of the recommended remedial grading. Response to Review Comment No. 3 A geotechnical map/plot plan is provided as Figure 1. Review Comment No. 4 The Geotechnical Consultant should provide recommendations for import materials to be used for general fill, retaining wall backfill, and utility trench backfill. Response to Review Comment No. 4 Import fill used as general fill should consist of granular soil with a “very low” to “low” expansion potential (EI of 50 or less) and free of deleterious material or rock larger than 6-inches. Import fill used as select backfill for retaining walls should consist of granular soil with a “very low” expansion potential (EI of less than 20) and free of deleterious material or rock larger than 6- inches. GeoTek should be notified of the imported soil source and should be authorized to perform laboratory testing of import soil prior to its arrival at the site to evaluate its suitability as fill. Review Comment No. 5 The Geotechnical Consultant should provide recommendations for vehicular pavements. Response to Review Comment No. 5 Traffic indices have not been provided during this stage of site planning. In addition, site conditions have not been graded to a final design to evaluate specific pavement subgrade conditions. Therefore, the minimum structural sections provided below are based on an assumed R-Value of 10 and assumed traffic indices. GEOTEK RINCON HOMES Project No. 3830-SD Garfield Beach Homes September 22, 2022 3570 Garfield Street, Carlsbad, California Page 3 PRELIMINARY ASPHALT PAVEMENT STRUCTURAL SECTION Design Criteria Traffic Index (TI) Pavement Thickness (inches) Aggregate Base (AB) Thickness (inches) Driveway 5.0 4 7 Parking Stalls 4.5 4 6 Actual structural pavement design is to be determined by the geotechnical engineer’s testing (R- Value) of the exposed subgrade. It is anticipated that Portland Cement Concrete (PCC) pavements will be utilized. Based on the City of Carlsbad minimum design guidelines for driveways, the following recommended minimum PCC pavement section is provided for these areas: PRELIMINARY PCC PAVEMENT STRUCTURAL SECTION Design Criteria Traffic Index (TI) Pavement Thickness (inches) Aggregate Base (AB) Thickness (inches) Driveway 5.0 7 6 Parking Stalls 4.5 6 0 Review Comment No. 6 The Geotechnical Consultant should provide recommendations for exterior concrete flatwork. Response to Review Comment No. 6 Exterior concrete flatwork should be designed using a four-inch minimum thickness with 6”x6” – WI.4/WI.4 welded wire fabric, placed in the middle of slab. It is recommended that control joints be placed in two directions spaced the numeric equivalent roughly 24 times the thickness of the slab in inches (e.g., a 4-inch slab would have control joints at 96-inch [8-feet] centers). These joints are a widely accepted means to control cracks and should be reviewed by the project structural engineer. Some shrinkage and cracking of the concrete should be anticipated as a result of typical mix designs and curing practices typically utilized in construction. Presaturation of flatwork subgrade should be verified to be a minimum of 100% of the soils optimum moisture to a depth of 12-inches for soils having a “very low” expansive index potential. GEOTEK RINCON HOMES Project No. 3830-SD Garfield Beach Homes September 22, 2022 3570 Garfield Street, Carlsbad, California Page 4 Review Comment No. 7 The Geotechnical Consultant should review the most recent version of the City of Carlsbad Best Management Practices (BMP) Design Manual (2021) and update the worksheets, as appropriate. Response to Review Comment No. 7 An updated stormwater evaluation based on the City of Carlsbads BMP Design Manual (2021) has been included as Appendix A. Review Comment No. 8 The referenced grading plans (Pasco Lauret Suiter & Associates, 2022) depict the structures beign placed in both cut and fill areas of the site. The Geotechnical Consultant should review the plans for areas of potential cut/fill transitions beneath the buildings and provide recommendations for areas of potential cut/fill transitions beneath the buildings and provide recommendations to mitigate these conditions, as appropriate. Response to Review Comment No. 8 Grading may result in a cut/fill transition at the proposed building pad finish grades. If a geologic contact of Formational material against fills is encountered at finish pad grades, the cut portion should be over-excavated a minimum of three feet below pad grades, or two feet below the base of proposed footings, whichever is deeper, and be replaced with engineered fill. Review Comment No. 9 On Page 5 under “Seismic Effects – Ground Accelerations” and on Page 7 under References” of the referenced geotechnical report (Hetherington Engineering, Inc., 2021) there are typos as the reports refers to the 2016 California Building Code (CBC) and American Society of Civil Engineers (ASCE) Publication 7-10 rather than 2019 and 2017 versions, respectively. Response to Review Comment No. 9 We concur that the above referenced documents CBC 2016 and ASCE publication 7-10 are typos, and the correct referenced documents are CBC 2019 and ASCE publication 7-16. The above comment is noted. Review Comment No. 10 There are more recent geology maps available for the project vicinity. The Geotechnical Consultant should review those and may consider updating their references, as appropriate. Response to Review Comment No. 10 The above comment is noted. GEOTEK RINCON HOMES Project No. 3830-SD Garfield Beach Homes September 22, 2022 3570 Garfield Street, Carlsbad, California Page 5 Closure Should you have any questions after reviewing this addendum, please feel free to contact our office at your convenience. Respectfully submitted, GeoTek, Inc. ENCLOSURES Figure 1 – Geotechnical Map Figure 2 – Cross-Section Appendix A – Stormwater Infiltration Distribution: (1) Addressee Via Email (1) PLSA – Bryan Knapp Christopher D. Livesey CEG, 2733 Exp. 05/31/23 Associate Vice President Edwin R. Cunningham RCE, 81687 Exp. 03/31/24 Project Engineer GEOTEK RINCON HOMES Project No. 3830-SD Garfield Beach Homes September 22, 2022 3570 Garfield Street, Carlsbad, California Page 6 References Hetherington Engineering, Inc., 2021, “Geotechnical Investigation and Infiltration Testing, Proposed Residential Development, 3570 & 3588-3590 Garfield Street, Carlsbad, California,” dated July 14, 2021. Ninyo & Moore, 2022, “Third-Party Geotechnical Review, Proposed Residential Development, 3570 & 3588-3590 Garfield Street, Carlsbad, California, Project No. 9325 1: dated July 14.”, dated June 29, 2022. Pasco Laret Suiter & Associates, 2022, “Preliminary Grading Plans For: Garfield Beach Homes, 3570 Garfield Street,) 3 sheets, undated. GEOTEK Qop HE B-1 HE I-2 Qop Qop Qop HE I-1 HE B-2 A A' LEGEND Approximate Location of HEI's Infiltration Tests HE I-2 A'A Qop Old Paralic Deposits Cross Section Approximate Limits of Recommended Remedial Grading Approximate Location of HEI's Exploratory Boring HE B-2 1384 Poinsettia Avenue, Suite A Vista, California 92081DATE: September 2022 0 30 60 Scale: 1" = 30' 10 Rincon Homes Garfield Beach Homes Project 3570 Garfield Street Carlsabd, California PN: 3830-SD Figure 1 Geotechnical Map (9 (9 (9 1-- tlj ~ CJ) a i:d G: ct: ~ 3 EXIS~8"VCP PE~D~:; (9 (9 ,, 11 I 1 ( , ~ (60.45 FL) ~ EXISTING 1" HP GAS MAIN PER DIM'., 43(-81139-7 \ \ /\ PROP-OSED TRANSFORMER cui:1~~~::i~ "' ' MATCH ;& EXIST re "" BEGIN IMRIROVMENTS PCCC&G, (60.95 TC),(60.5 FL) -s --~-.--1, 0 EXISTING POWER POLE!rO llE P OTECTED IN f'/LACE ~ EXISTING/ALM CJ TREE TO Ri MAIN ~ I ' I \ \ " ~ 1A ....._!,,,_ ~---+--?......+. t J er J;: r 2FS (60.6 FSJ t 10 ~ ) .,.,. LA -'9.1% ·_ t· 2. I s _,----=- 3 61.2 RIM 4 PROP SEWllR MH r6tsl~1~ 50.5/E · ' gu-1---tt----;;" - (9 ----+ __ ~,~ ~ ' EXISTING WA,TER LATERAL AND METER TO BE REMOVED (6if65 FS) ! <1.9.7% 20% - I l CONNEU/i TO EXISTING l WATERMAIN I/} \6 CONNECT TO EXISTING , I )J I e9WATER MAIN LA 13 re o (9 P,ROPOSED 6" 8 FIRE SERVICE Ll E (SIZE TBD} ev--/ L EX<SEWERMH (50.4 IE) I EX/ST:NG 6"A.C. WATER'-7/AA/N PER Dv\G 170-8/139-7 j D MATCI-FrO EXIST TC END IMPROVMENTS I PCCC&G; (60.82°fTC),(6049 FL) ~ TC ~o I ADDITIONAL NOTES 120· I 5.5' . •5.0' LA ' l .'. / 1. ALL UTILITIES SHOWN HEREON PER BEST AVAILABLE RECORD INFORMATION 2. ALL EXISTING ONSITE STRUCTURES TO BE DEMOLISHED UNLESS Or:HERWISE NOTED. 3. ALL EXISTING ONSITE TREES TO BE REMOVED UNLESS Or:HERWISE NOTED. 4. ALL ONSITE Vltl\TER, SEWER, AND STORM DRAIN FACILITIES TO BE PR/VA.TEL Y MAINTAINED. 5. HARDSCAPE SHALL DRAIN AVIII\Y FROM PROPOSED STRUCTURES AT A MINIMUM OF 2. 0% FOR 10 FEET. AND LANDSCAPE FOR A MINIMUM OF 5.0% IN ACCORDANCE WITH THE 2016 CALIFORNIA BUILDING CODE SECTION 1804.4. ANY DEVIATION SHALL REQUIRE RECOMMENDATION FROM PROJECT GEOTECHNICAL ENGINEER. ) I \ \ 62.3 \ \ EX S NG2 Cl{Y BL LU "IG f I I (60.8B~EG) 60,91/W@FG I --,--EXISTING STRUCTURE LOT4 MAP 7961 60.7 (58.5 BW@EG) 58.5 7W 1EXISTING STRUCWRE TO REMAIN 61.0 7½,I FG 59.0llW@FG 1 =20FT r----"""-'-"'I X 2.0' 6.0' o-+--SD --, r- 1 58.5 FG t . 61 5 FS 'HI . 58.45 FS r --+~\ i,---+-w --+- LA 61.1 aw H=O.OFT 2.0FT .05FS '--t"""J:,jfr,--;f,'----,~O:..:_F_:_S.,_ 61.5 ::l: 591/BW ' TO REMAIN 60.9 (59.1 BW@EG) SD LA I ,_J 58.5BW@FG H=O.OFT r-- 58.0 7W (56.0 BW@EG) H=2.0FT 18 57.1 TG 55.6/E- 57.1 7W I SlOBW@FG /54.1 BW@EG) N 55'56'01" E 12q.oo• H = 3.0 FT 583 FS , . -_ I~' ~ ;57.5 FS , J ~ , _, ' -, "-, • -~ -· ~ 56.3F · I os · Ir 5l3F _,. , , 51'3FS . _ W · ' W-+-_.___ W ~ VV _....,._ W -----w'--~ W -+-W ---'"-·'W ----W 1. (/) -'w-' · w· (/) "·· w . (/) ~__,,, W · 1,<--W _,;.;,..._ 1W· <I. • W --+--u;v ~-, W ---, 'i\ GF= 58.5 -=---..YJ-5 FG 58.1 FS I UNIT 12 ' F/S =-59.2 PAD=58.5 582FS 58.7FS 58.2FS 56.0FG t 100: . ' Gf =57.5 57.5FG 57·5 FG 6" PRIVATE FIRE SERVICE LINE 577FG 57.6FG UNIT 11 I 57.5FG FF= 58.2 PAD= 57.5 58.2 FS L_ 57.2 FG 14 ( GF = 715 UN,IT 10 FF .., 58.2 PAD ,... S-7.5 ) 57.2 FS 57.7 FS -~S7.2FS H=2.5FT 14 56.SFG 7 567TG 18 55.0 IE ~I •~ _ '~I s "' " 10.0' < 1 12.0' X I 1 ) EX' T Nb ] ,..T R'r 8 OINC 56.0IW 56.0BW@FG (53.0BW@EG) _H=30FT GF =56.5 _ j 56.5FG 56.8 FG 2"DOMESTIC SERVICE TRENCH 56.7FG UN/T9 ..-,,-@ FF=57.2 PAD=56.5 54.3 7W (51.3 BW@EG} H=3.0FT 57.2 FG 18 56.1TG 54.6 IE 56.5 FG 14 [ LOT10 BLOCKQ MAP 1803 12 53.5TW (50.5 BW@EG} H=3.0FT 18557 TG 54.3 IE N 55'57~2" E 122.51' GF =56.5 PROPOSED6" PVC PVT SEWER LATERAL@ 1.0% UN/TB FF= 57.2 PAD =56.5 56.2 FG 57.2 FG \ \ TOP OF SLOPE; 55.5FG - _J LA v-V 55.BF EX NI, T(RVBULDIN, I F EXISTING STRUCWRE TO REMAIN 54.5/W 545TW@FG (50.3 BW@EG) -(5_0_5-B~~~J~EIW~G)'--------, H=42FT (.) H=4.0FT 18 55.4 TG 54_-o IE \GF=565 \ 56.3FS 55.SFG \ UNIT 7\ FF =5 . PAD =56. 55.5FG I _J ~ 712.0'X-\~I ~~1~4, ~~~~_:_•J--_,~~ - - -=~---f0g ~,-1-+ i x L o+---SD X r 56.5FS 58.4 TG 18 56.3 IE '61.5 56.58W H = 3.0FT END OF EXISTING PCCCURB EXISTING A. C. DRIVEWAY APRON TO REMAIN LA ---SD --SD ---SD X c, o-r--+'S,D --SD EXISTING OWY TO BE PROTECTED IN PLACE 18 57/HG ',\ ;;; 5611\ 591! 57.5BW@FG H= 1.5FT I LOTT EXISTING MAP 7961 STRUCWRE TO REMAIN 575/W (57.5 BW@EG) H=OFT LJ --- ~ >< ---SD --SD -++-+-SD 1857.1 TG 55.6/E 57.3/W /55.8 BW@EG) H= 1.5 FT / I CQ LA SD \---SD \__ N 55'58'18" E 242.55\ \ 56.8/W [5J8BW@ EG} \ H=3.0FT I ( SD 56.8 TG 18 55.0 IE PLAN VIEW -PRELIMINARY DRAINAGE PLAN SCALE.1" = 10' HORIZONTAL ---SD --SD 56.5/W (53.5 BW@EG) H=3.0FT A ~ ---SD --SD"==--SD ---SD ---S D (52.1 BW@EG) H=3.0 FT EXISTING FENCE TO REMAIN / ), \ I I r I I 18 557TG 54.3 IE 54.1/W (511 BW@EG) /-/ = 3.0 FT LOT1 BLOCKQ MAP 1803 TOP OF SLOPE; 55.5FG 1 I ' I j 54.5/W (50.1 BW@EG) H=3.8 FT 545/W 54.5/W@FG '(50.5 BW@EG) H=4.0FT NOTE: SEWER LATERAL LOCATION UNKNOWN. TO BE REMOVED PER CITY STANDARDS. PASCO LARET SUITER ~ ffe.$$(Q)lC!ffe.'flE$ San Diego I Solana Beach I Orange County Phone 858.259.8212 lwww,plsaengineering.com 54.5 7W 53.0TW@FG (505 BW@EG) H=4.0FT \ r _._J '""\ \ .O' \ ( 54.5 7W (50.0 BW@EG) H =4.5FT L ) ) ) (49.0 FG} l I \ / ~(49 .5FG) 54.5 7W I 53.0IW@FG (505 BW@EG) \ H=4.0FT ) \ \ \ . ' 54.5 7W 53.0TW@FG (50.2BW@EG) H=4.3FT L ) . \ Iv \ \ I , \ L \ ) \ r \ I I I ( --- - \ , J \ fsHrri7 CITY OF CARLSBAD I SHE3ETS I LI__j TENTATIVE TRACT MAP PRELIMINARY GRADING PLAN FOR: GARFIELD BEACH HOMES 3570 GARFIELD STREET I ENGINEER OF WORK: TilER G LAWSON I OWN BY: DAlE: CHKD BY: RCE: 80356 _ RVWD BY: A GEOTEK RAK TGL A 60 so JO ~ P\.. 11!1 "' t I a, l .J I "' M ~ I < U) ·;- -... A l"l'R.o.x,r >IA.TE. ....... ------- L:fMl'T5 OF ,a,_•P~S~t, I,. -2 -- STRr.lC.T\IRE -- AffltOXX/1\ATZ! lt.M.:?l5 OF PRo,-,H '> $'TA.Ve.TU I\&: H.E'B-I (PP.eJ :r'!J>) +---------~--+------'------+----.:..--------r-·-.. 1 0 50 100 150 :z.oa DISTANC.E. (J=!!aT) -----TRE.N\>: N SOE -----)-,.. GEO LOGIC CR0SS-S ECTZ:ON A-A' A' ~ I -60 ,.. ._J: _. "" l:: -z -so 0 t-1 I-.( > I.I-I _. l!.I. GE OTE. K P N: .3&3C-.SD R.r >-.JC.otv HoME..$ 3 5 71-0 GJJ.~F~1=1-'b STR.u-T ('.:A~c.., gA hi J CA 1-l" f"pJl'Nl' A Appendix A Stormwater Infiltration GEOTEK Stormwater Infiltration Many factors control infiltration of surface waters into the subsurface, such as consistency of native soils and bedrock, geologic structure, fill consistency, material density differences, and existing groundwater conditions. The current grading plan indicates an infiltration basin located on the east perimeter of the property, which is shown on Figure 1. A review of the site conditions and proposed development was performed in general accordance with the City of Carlsbad BMP design manual. The scope of stormwater evaluation was performed to identify infiltration characteristics. As required by the City of Carlsbad BMP design manual, the following bullet points describe required considerations and some optional considerations. 5.3.1a. Based on a review of www.geotracker.com, environmental impacted sites are not reported within 100 feet of the site. 5.3.1b. Based on a review of Geotracker.com and a reconnaissance of the properties surrounding the site, which were found to be residential, there was not an industrial active building that may pose a lack of source control within 100 feet of the site. 5.3.1c. Based on the surrounding existing development and the understanding that the proposed project will be supported by a municipal sanitation system, the BMPs are not located within 50 feet of septic tanks or leach fields. 5.3.1d. Based on a review of the proposed improvements, the BMPs are designed within 10 feet of retaining walls. 5.3.1e. Based on a review of the proposed improvements, the BMPs are not anticipated to be designed within 10 feet of sewer utilities. 5.3.1f. Based on a review of the topography of the site, hydric soils are not prone to exist. 5.3.1g. Based on the shallow dense paralic deposits, hazards due to liquefiable soils are considered to be low. 5.3.1h. Based on the proposed design, the BMP is not located within 1.5 times the height of an adjacent steep slope (basement). Table D.1-1: Considerations for Geotechnical Analysis oflnfiltration Restrictions Mandatory Considerations Optional Considerations Result Restriction E lement BMP is within 100' of Contaminated Soils Is Element Applicable? (Yes/No) BMP is within 100' of Industrial Activities Lackin Source Control No BMP is within 100' of Well/Groundwater Basin No Bi\CT) is within 50' of Septic Tank s/Leach Fields No Bi\fP is within 10' of Scrucmres/Tanks/Walls Yes B.MP is within 10' of Sewer Utilities No BMP is within 1 O' of Groundwater Table No Bi\n) is within Hydric Soils No BMP is within Highly Liquefiable Soils and has Connectivity to Structures No B!\fP is within 1.5 Times the Height of Adjacent Steep Slopes P-25%) No County Staff has Assigned "Restricted" Infiltration Category No BMP is within Predominanclr Type D Soil B!\•fP is within 1 O' of Property Line Bi\n) is within Fill Depths of ~s• (Existing or Proposed) B fP is within 10' of Underground Utilities Bi\OJ is within 250' of Ephemeral Stream Other (Provide detailed geotcchnical support) Based on examination of the best available information, □ I have not identified any restrictions above. Unrestricted Based on examination of the best available information, I have identified one or more restrictions above. Restricted Table D.1-1 is divided into Mandatory Considerations and Optional Considerations. Mandatory Based on the restricted category of the DMA, the proposed basin can be designed for filtration but the retaining walls for the BMP, should be designed with an impermeable liner to mitigate the potential for the basin water seeping through the walls. Table D.2-1: Elements for Determination of Design Infiltration Races Initial Infiltration Rate Identify per Section 0 .2.1 2.3 in/hr Corrected Infiltration Rate Identify per Section 0.2.2 N/A in/hr Safety Factor unitless Identify per Section D.2.3 1.875 Design Infiltration Rate in/hr Corrected Intilm1tion Rate..,. Safetr Factor 1.2 December 1, 2022 Project No. 3830-SD Rincon Homes 5315 Avenida Encinas, Suite 200 Carlsbad, California 92008 Attention: Mr. Tom St. Clair Subject: Response to Third-Party Geotechnical Review Comments Proposed Residential Development 3750 & 3588-3590 Garfield Street Carlsbad, California Reference: See Page 6 Dear Mr. St. Clair: As requested, by Bryan Knapp, Pasco Laret Suiter & Associates (PLSA), GeoTek, Inc., (GeoTek) has prepared this letter to provide a supplemental responds to City of Carlsbad third-party review comments (second round) of the “Geotechnical Investigation and Infiltration Testing, Proposed Residential Development, 3570 & 3588-3590 Garfield Street, Carlsbad, California, Project No. 9325.1” by Hetherington Engineering, Inc. (HEI), dated July 14, 2021 and “Grading Plans For: 3570 Garfield Street, Project No. CT 2021-0002” by Pasco Laret Suiter & Associates, dated 2022 (sheets 1 through 8). Our numbering corresponds to that used by the reviewer. Review Comment No. 11 On Sheet 5 of the reference grading plans (Pasco Lauret Suiter & Associates, 2022), the Typical Detail – Biofiltration with Partial Retention Basin (BMP 1) in the center of the sheet depicts a BMP devise between two planned retaining walls. The plans show an impermeable liner along the sides of the BMP, but indicate the use of a permeable geofabric at the base of the BMP. The Geotechnical Consultant should provide comment on the suitability of this BMP configuration and also provide recommendations for the use of submerged lateral earth pressures and a submerged bearing capacity value, if appropriate. Response to Review Comment No. 11 The biofiltration with partial retention basin (BMP 1) configuration is suitable from a geotechnical standpoint. The retaining wall adjacent to the eastern property line and part of the BMP 1 structure should be designed usings an active lateral earth pressure of 80-pounds-per-cubic-foot, GeoTek, Inc. 1384 Poinsettia Avenue, Suite A Vista, CA 92081-8505 (760) 599-0509 (760) 599-0593 www.geotekusa.com GEOTEK RINCON HOMES December 1, 2022 Response to Third-Party Review Comments Error! Reference source not found. Garfield Beach Homes Project, Encinitas, California Page 2 equivalent fluid pressure (EFP) for design of cantilevered walls with hydrostatic pressures. No reduction in bearing value is required. Closure Should you have any questions after reviewing this addendum, please feel free to contact our office at your convenience. Respectfully submitted, GeoTek, Inc. Distribution: (1) Addressee Via Email (1) PLSA – Bryan Knapp REFERENCES Hetherington Engineering, Inc., 2021, “Geotechnical Investigation and Infiltration Testing, Proposed Residential Development, 3570 & 3588-3590 Garfield Street, Carlsbad, California,” dated July 14, 2021. Ninyo & Moore, 2022, “Second Round of Third-Party Geotechnical Review, Proposed Residential Development, 3570 & 3588-3590 Garfield Street, Carlsbad, California”, dated October 19, 2022. Pasco Laret Suiter & Associates, 2022, “Preliminary Grading Plans For: Garfield Beach Homes, 3570 Garfield Street,) 3 sheets, undated. Christopher D. Livesey CEG, 2733 Exp. 05/31/23 Associate Vice President Edwin R. Cunningham RCE, 81687 Exp. 03/31/24 Project Engineer GEOTEK February 28, 2023 Project No. 3830-SD Rincon Homes 5315 Avenida Encinas, Suite 200 Carlsbad, California 92008 Attention: Mr. Tom St. Clair Subject: Response to Third-Party Geotechnical Review Comments Proposed Residential Development 3750 & 3588-3590 Garfield Street Carlsbad, California Reference: See Page 3 Dear Mr. St. Clair: As requested, by Bryan Knapp, Pasco Laret Suiter & Associates (PLSA), GeoTek, Inc., (GeoTek) has prepared this letter to provide a a grading plan review and supplemental responce to City of Carlsbad third-party review comments (second round) of the “Geotechnical Investigation and Infiltration Testing, Proposed Residential Development, 3570 & 3588-3590 Garfield Street, Carlsbad, California, Project No. 9325.1” by Hetherington Engineering, Inc. (HEI), dated July 14, 2021 and “Grading Plans For: 3570 Garfield Street, Project No. CT 2021-0002” by Pasco Laret Suiter & Associates, dated 2022 (sheets 1 through 9). A copy of the geotechnical comments have been included as appendix A. Our numbering corresponds to that used by the reviewer. Review Comment No. 11 On Sheet 5 of the reference grading plans (Pasco Lauret Suiter & Associates, 2022), the Typical Detail – Biofiltration with Partial Retention Basin (BMP 1) in the center of the sheet depicts a BMP devise between two planned retaining walls. The plans show an impermeable liner along the sides of the BMP, but indicate the use of a permeable geofabric at the base of the BMP. The Geotechnical Consultant should provide comment on the suitability of this BMP configuration and also provide recommendations for the use of submerged lateral earth pressures and a submerged bearing capacity value, if appropriate. Response to Review Comment No. 11 The biofiltration with partial retention basin (BMP 1) configuration is suitable from a geotechnical standpoint. The retaining wall adjacent to the eastern property line and part of the BMP 1 GeoTek, Inc. 1384 Poinsettia Avenue, Suite A Vista, CA 92081-8505 (760) 599-0509 (760) 599-0593 www.geotekusa.com GEOTEK RINCON HOMES February 28, 2023 Response to Third-Party Review Comments Project No. 3830-SD Garfield Beach Homes Project, Encinitas, California Page 2 structure should be designed usings an active lateral earth pressure of 80-pounds-per-cubic-foot, equivalent fluid pressure (EFP) for design of cantilevered walls with hydrostatic pressures. No reduction in bearing value is recommended. Geotechnical Review of Retaining Plans Changes to the grading plans to reflect the redesigned retaining walls for BMP 1 were reviewed by GeoTek for the purpose of forming an opinion of the geotechnical suitability of the plan to support the proposed improvements and for inclusion of geotechnical design parameters provided in the “Geotechnical Investigation and Infiltration Testing, Proposed Residential Development…” 2021, by Hetherington Engineering, Inc. (HEI) and this Response to Third-Party Review Comments letter. Geotechnical Review of Grading Plans We have reviewed the grading plan prepared by Pasco Laret Suiter and Associates (PLSA), Sheets 1 through 9. Based on our review of the grading plan, they have been prepared in general accordance with the geotechnical recommendations contained within the referenced report by HEI and the geotechnical parameters provided by GeoTek in this letter. Closure Should you have any questions after reviewing this addendum, please feel free to contact our office at your convenience. Respectfully submitted, GeoTek, Inc. Attached: Appendix A Distribution: (1) Addressee Via Email (1) PLSA – Bryan Knapp Christopher D. Livesey CEG, 2733 Exp. 05/31/23 Vice President Edwin R. Cunningham RCE, 81687 Exp. 03/31/24 Project Engineer GEOTEK RINCON HOMES February 28, 2023 Response to Third-Party Review Comments Project No. 3830-SD Garfield Beach Homes Project, Encinitas, California Page 3 REFERENCES Gouvis Engineering, Inc., 2023, “Structural calculations (A 12 Unit Residential Development), Rincon Garfield, Site Retaining Wall, Carlsbad, San Diego, CA”, dated February 23, 2023. Hetherington Engineering, Inc., 2021, “Geotechnical Investigation and Infiltration Testing, Proposed Residential Development, 3570 & 3588-3590 Garfield Street, Carlsbad, California,” dated July 14, 2021. Ninyo & Moore, 2022, “Second Round of Third-Party Geotechnical Review, Proposed Residential Development, 3570 & 3588-3590 Garfield Street, Carlsbad, California”, dated October 19, 2022. Pasco Laret Suiter & Associates, 2023, “Grading Plans For: 3570 Garfield Street, GR 2022-0024, CT 2021-0002,” 9 sheets, received February 28, 2023. GEOTEK APPENDIX A Copy of Geotechnical Review Comments GEOTEK Geotechnlcal & Environmental Sciences Consultants October 19, 2022 Project No. 109343007 Ms. Jessica Nishiura, P.E. Hunsaker & Associates San Diego, Inc. 9707 Waples Street San Diego, California 92121 Subject: Second Round of Third-Party Geotechnical Review Proposed Residential Development 3750 & 3588-3590 Garfield Street Carlsbad, California Dear Ms. Nishiura: At your request, we have prepared this letter providing our second round of review comments to the referenced geotechnical report prepared by Hetherington Engineering dated July 14, 2021 and the referenced letter prepared by GeoTek dated September 22, 2022. Our original comments were prepared in the referenced Ninyo & Moore letter dated June 29, 2022. Based on our review of the more recent letter prepared by GeoTek dated September 22, 2022, the following comment remains: Closed Comment 1: Addressed in the GeoTek letter dated September 22, 2022. Closed Comment 2: Addressed in the GeoTek letter dated September 22, 2022. Closed Comment 3: Addressed in the GeoTek letter dated September 22, 2022. Closed Comment 4: Addressed in the GeoTek letter dated September 22, 2022. Closed Comment 5: Addressed in the GeoTek letter dated September 22, 2022. Closed Comment 6: Addressed in the GeoTek letter dated September 22, 2022. Closed Comment 7: Addressed in the GeoTek letter dated September 22, 2022. Closed Comment 8: Addressed in the GeoTek letter dated September 22, 2022. Closed Comment 9: Addressed in the GeoTek letter dated September 22, 2022. Closed Comment 10: Addressed in the GeoTek letter dated September 22, 2022. Remaining Comment 11: This comment was not formally addressed in the GeoTek letter dated September 22, 2022 and the noted detail in the project grading plans (Pasco Lauret Suiter & Associates, 2022) has not been amended. Accordingly, the following comment remains. 5710 Ruffin Road I San Diego, California 92123 Ip. 858.576.1000 I www.ninyoandmoore.com On Sheet 5 of the referenced grading plans (Pasco Lauret Suiter & Associates, 2022), the Typical Detail -Biofiltration with Partial Retention Basin (BMP 1) in the center of the sheet depicts a BMP device between two planned retaining walls. The plans show an impermeable liner along the sides of the BMP, but indicate the use of a permeable geofabric at the base of the BMP. The Geotechnical Consultant should provide comment on the suitability of this BMP configuration and also provide recommendations for the use of submerged lateral earth pressures and a submerged bearing capacity value, if appropriate. We appreciate the opportunity to be of service. Respectfully submitted, NINYO & MOORE ff!~ Jeffrey T. Kent, PE, GE Principal Engineer JTK/mp Attachment: References Nlnyo & Moore I 3750 & 3588-3590 Garfield Street, Carlsbad, California I 109343007 I October 19, 2022 2 REFERENCES GeoTek, Inc., 2022, Response to Third-Party Geotechnical Review Comments, Proposed Residential Development, 3750 & 3588-3590 Garfield Street, Carlsbad, California, Project No. 3830-SD: dated September 22. Hetherington Engineering, Inc., 2021, Geotechnical Investigation and Infiltration Testing, Proposed Residential Development, 3570 & 3588-3590 Garfield Street, Carlsbad, California, Project No. 9325.1: dated July 14. Ninyo & Moore, 2022, Third-Party Geotechnical Review, Proposed Residential Development, 3750 & 3588-3590 Garfield Street, Carlsbad, California, Project No. 109343007: dated June 29. Pasco Lauret Suiter & Associates, 2022, Grading Plans For 3570 Garfield Street, 3570 Garfield Street, Project No. CT 2021-0002, Drawing Number 538-2A, Sheets 1 through 8. Ninyo & Moore I 3750 & 3588-3590 Garfield Street, Carlsbad, California I 109343007 I October 19, 2022 3