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Home My WebLink AboutCDP 2021-0025; SWAN RESIDENCE; 1ST RESPONSE BY ROCK SOLID GEOTECHNICAL TO 2ND REVIEW COMMENTS; 2024-07-22 TRE Architecture 300 Carlsbad Village Drive Suite 108a-336 Carlsbad, Ca 92008 July 22, 2024 Project No. 171.1 Attention: Allan Teta; allan@trearch.com Subject: 1st Response by Rock Solid Geotechnical to 2nd Review Comments 2668 Ocean Street, Carlsbad, California 92008 Proposed Single-Family Residence References: See Attached Dear Mr. Teta, In response to the referenced geotechnical report review comments, we have prepared this document to address geotechnical related review comments made on February 17, 2024, by the City of Carlsbad (Project ID: CDP2021-0025) (Grading Permit No.: GR2022-036). We have reviewed the referenced geotechnical reports prepared by Hetherington Engineering, Inc. (Hetherington) relative to the proposed new construction, along with Rock Solid’s relatively recent review response, and we generally concur with the findings and recommendations with the exception of the updated recommendations provided by our response to the geotechnical review comments below. Should you have any questions, please do not hesitate to contact the undersigned. Respectfully Submitted, Rock Solid Geotechnical, Inc. (Rock Solid). Jamie K. Fink President Professional Geologist 7626 Certified Engineering Geologist 2636 Expires 10/31/25 Sean P. Prenovost Associate Senior Engineer Professional Engineer 94193 Expires 12/31/24 Note: For convenience, we have rewritten the comments in italics. Our response is written directly below each comment. GEOTECHNICAL J El 333 Third Street, Suite 2 Laguna Beach, CA 92651 949.558.9776 jamie@rocksolidgeotechnical.com www.rocksolidgeotechnical.com 1st Response by Rock Solid Geotechnical to 2nd Review Comments Proposed Single-Family Residence 2668 Ocean Street, Carlsbad, California 92008 July 22, 2024 Project No. 171.1 #1: Please provide updated seismic design parameters for the proposed development based on the 2019 California Building Code and ASCE 7-16. (repeat comment – please revisit and confirm the Seismic Design Category (SDC) that is provided in the “GEOR Letter and Second Revised 1st Response by Rock Solid Geotechnical…” report (“Null”) and revise as necessary in accordance with Tables 1613.2.5(1) and 1613.2.5(2) of the CBC and Tables 11.6-1 and 11.6-2 of ASCE 7-16.) Response: As requested, the seismic design parameters are provided in the table below based on the 2019 California Building Code and ASCE 7-16. The Seismic Design Category has been updated in accordance with Tables 1613.2.5(1) and 1613.2.5(2) of the CBC and Tables 11.6-1 and 11.6-2 of ASCE 7-16. Table - 2019 CBC Seismic Design Criteria Seismic Parameters Site Class D Seismic Design Category (SDC) D Risk Category II Spectral Response (SS) 1.099 Spectral Response (S1) 0.397 g Spectral Response (SMS) 1.166 g Spectral Response (SM1) Null – See Section 11.4.8 Spectral Response (SDS) 0.777 g Spectral Response (SD1) Null – See Section 11.4.8 Site Coefficient (Fa ) 1.06 Site Coefficient (Fv) Null – See Section 11.4.8 Modified Peak Ground Acceleration PGAM 0.542 #2: Please provide specific backcut recommendations to address the construction of the site retaining wall that is proposed immediately along and adjacent to the eastern property boundary. As it appears that an approximate 6’ cut will be necessary immediately along the property boundary to construct the proposed wall, the recommendations should full address the condition and provide guidelines as necessary to assure worker safety and protect adjacent off-site property from any adverse impacts from the proposed construction. If slot cutting and vertical cuts are proposed, please provide dimensions and calculations demonstrating the stability of the proposed vertical cuts, widths of slots, and the time that the cuts may remain exposed. (repeat comment - the response to this comment provided in the "GEOR Letter and Second Revised 1st Response by Rock Solid Geotechnical..." report stated the use of a permanent shoring retaining wall is being proposed. However, the consultant's response to the previously issued comment below (#3) stated shoring is not required and further provides recommendations for A-B-C slot cut sequence method for the construction of the proposed retaining wall. Please clarify the proposed method of construction for the proposed retaining wall at the rear of the property. 9 333 Third Street, Suite 2 Laguna Beach, CA 92651 1st Response by Rock Solid Geotechnical to 2nd Review Comments Proposed Single-Family Residence 2668 Ocean Street, Carlsbad, California 92008 July 22, 2024 Project No. 171.1 Response: Varying options have been presented at various times with respect to constructing a retaining wall. Ultimately, the client has decided to leave the existing wall in place and construct the new retaining wall in front of the existing retaining wall. The design of the wall footing has also changed, placing the key at the front of the new wall foundation in order to accommodate the geotechnical maximum vertical cut of 3-feet that will be necessary to construct the new wall. The referenced grading plans provide a section through the updated location and footing dimensions (Sheet 2 of 5). Additional subsurface exploration was performed directly in front of the existing low height retaining wall in order to evaluate the condition of the soil that will be exposed during the slot cut excavation. The results of the direct shear run on the sample are provided as an attachment to this response. Slot cut analyses were performed using the results of the laboratory test and are attached to this response. The temporary excavations are expected to be performed in A-B-C slot cut sequence method consisting of a maximum width of 8-feet and a maximum height of 3-feet. The An A-B-C construction sequencing method with a maximum width of 8 feet and a maximum vertical excavation of 3-feet may be utilized for construction of the above-mentioned retaining wall. A standard figure has been attached illustrating the slot cut method. Slot A-B-C construction method should follow the procedure sequence outlined below: 1. Trim the area of proposed excavation for the retaining wall at a 1:1 (horizontal: vertical) 2. Excavate ‘A’ slot sections to bottom of foundation elevation. 3. Set reinforcing at footing per detail with a minimum rebar extension on both sides of the footing as designed by the structural engineer. 4. Place concrete in accordance with the structural plans and allow at least 48 hours for concrete to cure. a. Compressive strength testing for concrete may be required to ensure concrete achieves adequate strength. 5. Construct the masonry retaining wall as designed by the structural engineer. 6. Allow at least 48 hours for grout to cure. a. Compressive strength testing for grout may be required to ensure grout achieves adequate strength. 7. Install the wall subdrain and waterproofing as designed by the structural engineer. 8. Backfill retaining wall active zone with free draining soils in accordance with the geotechnical recommendations (90% per ASTM D1557) to design finished grade prior to beginning slot cut excavations ‘B’ or ‘C’. 9. Excavate ‘B’ slot sections to bottom of foundation elevation and follow steps 3 through 8 above. 10. Excavate ‘C’ slot sections to bottom of foundation elevation and follow steps 3 through 8 above. 9 333 Third Sbeel, Suite 2 Laguna Beach, CA 92651 1st Response by Rock Solid Geotechnical to 2nd Review Comments Proposed Single-Family Residence 2668 Ocean Street, Carlsbad, California 92008 July 22, 2024 Project No. 171.1 The duration that construction excavations may remain open is preliminarily considered, assuming that the work is performed in an expeditious manner, the time it takes to construct the proposed site retaining walls (estimated time 8 to 10-weeks). As mentioned above, an Engineering Geologist should be called for the test excavation and for subsequent slot cut excavations. If different subsurface conditions are observed during construction, Rock Solid should be notified immediately. #3: Please provide recommendations and parameters for shoring if necessary for the construction of the proposed site retaining wall along the eastern property boundary discussed above in comment #2. (repeat comment - the response to this comment provided in the "GEOR Letter and Second Revised 1st Response by Rock Solid Geotechnical..." report provides recommendations for A-B-C slot cut sequence method for the construction of the proposed retaining wall with a guideline of a maximum 4' high vertical cut. The reviewer notes that the retaining wall design provided in the most recent Civil plans suggests a maximum 8' high cut (maximum 5.5' retaining plus 2.5' for wall foundation) adjacent to an existing wall will be required for construction of the proposed retaining wall. Please provide additional recommendations and temporary stability analysis as necessary for the construction of the proposed retaining wall that addresses the maximum vertical cut of 8’. Response: Shoring is not considered necessary at this time as the slot cut method will be utilized to protect the eastern property boundary during construction. Attachments: Direct Shear Results Slot Cut Analysis Slot Cut Standard Figure 9 333 Third Sbeel, Suite 2 Laguna Beach, CA 92651 1st Response by Rock Solid Geotechnical to 2nd Review Comments Proposed Single-Family Residence 2668 Ocean Street, Carlsbad, California 92008 July 22, 2024 Project No. 171.1 REFERENCES 1. “GEOTECHNICAL INVESTIGATION, Proposed Single Family Residence, 2668 Ocean Street, Carlsbad, California,” by Hetherington Engineering, Inc., dated October 9, 2019, Project No. 8889.1. 2. “GEOTECHNICAL UPDATE, Proposed Two-Story Single-Family Residence, 2668 Ocean Street, Carlsbad, California,” by Hetherington Engineering, Inc., dated October 5, 2020, Project No. 8889.1. 3. “RESPONSE TO CITY OF CARLSBAD GEOTECHNICAL COMMENTS, Proposed Single-Family Residence Rear Yard Retaining Wall, 2668 Ocean Street, Carlsbad, California” by Hetherington Engineering, Inc., dated December 10, 2021, Project No. 8889.1. 4. “Grading Plans for 2668 Ocean Street SFD, Carlsbad, California” Sheets 1 through 5, prepared by Pasco Laret Suiter & Associates. 5. “GEOR Letter and Second Revised 1st Response by Rock Solid Geotechnical to Review Comments, 2668 Ocean Street, Carlsbad, California 92008, Proposed Single-Family Residence” by Rock Solid Geotechnical, Inc., dated February 7, 2024. 9 333 Third Street, Suite 2 Laguna Beach, CA 92651 DIRECT SHEAR Tested By: TR Checked By: TR Client: Rock Solid Geotechnical Project: Source of Sample: B-1 Depth: 2.0 Sample Number: B-1 Proj. No.: 171.1 Date Sampled: Sample Type: Natural Description: Dark Yellowish Brown Silty Sand Specific Gravity= 2.65 Remarks: Figure Sample No. Water Content, % Dry Density, pcf Saturation, % Void Ratio Diameter, in. Height, in. Water Content, % Dry Density, pcf Saturation, % Void Ratio Diameter, in. Height, in. Normal Stress, psf Primary Stress, psf Strain, % Residual Stress, psf Strain, % Strain rate, in./min. In i t i a l At T e s t Sh e a r S t r e s s , p s f 0 500 1000 1500 2000 2500 3000 Strain, % 0 5 10 15 20 1 2 3 Re s i d u a l S t r e s s , p s f Pr i m a r y S t r e s s , p s f 0 1000 2000 3000 Normal Stress, psf 0 1000 2000 3000 4000 5000 6000 C, psf f, deg Tan(f) Primary Residual 159 40 0.82 94 34 0.68 1 9.6 111.0 51.9 0.4901 2.40 1.00 14.7 111.8 81.1 0.4796 2.40 0.99 500 632 5.0 443 10.8 0.004 2 9.6 107.4 47.1 0.5402 2.40 1.00 15.1 108.1 75.2 0.5310 2.40 0.99 1000 890 3.7 755 8.2 0.004 3 9.6 110.4 51.1 0.4984 2.40 1.00 15.3 111.5 83.7 0.4834 2.40 0.99 2000 1838 4.1 1453 10.1 0.004 / ... I/ ,, / ," V J,, ,, I/ ,,?' ,,- I / ,, I / I ,, )I< () V ,, ,, I ,; ,, I ,; ,, I v 7 ,_ V ,, V ,,( ,; ,., I/ ,, / ,, V ··'' ,,,,, ,; ,, I/ ,,,.- / .... V ,, ,, ~ ., / .,.,, v ,, v , .• " i,,'-t;.'J,4 r..?" -I/ J \ I 1, -- I I/ I r-., II I I/ V 'I ~H SLOT CUT ANALYSIS SLOT CUT ANALYSIS Project Information Client: Project Location: 2668 Ocean Street, Carlsbad, California Project Number: 171.1 Date: July 22, 2024 Data Entry Profile or Slot Cut? S (P/S) Consider Tension Crack? N (Y/N) Soil Type: Terrace USCS Description: silty sand USCS Symbol: SM (less than 45 degrees) Phi (deg): 30 Cohesion (psf): 80 Sat. Unit Weight (pcf): 120 Vertical Height of Temporary Cut (ft): 3.0 Slope Above Vertical (Y/N): N Slope Angle (deg): 0 Vertical Height of Slope Area (ft): 0.0 Surface Load Per Foot of Cut (psf): 0 Assumed to act above cut slope Width of Slot Cut (ft): 8.0 Reduction Factor for Sidewall Cohesion: 0.5 between 0.5 and 1.0 Results Check: Factor of Safety: 1.45 OK 0 0.5 1 1.5 2 2.5 3 3.5 0 2 4 6 8 OCKSOLIDGEOTECHNICAL 949.558.9776 jamiefink2001@yahoo.com 27682 GolondrinaMission Viejo, CA 92692 J I I I I I I I I I I I I I I I I I I \ \ C. \ \ TRE Architecture 300 Carlsbad Village Drive Suite 108a-336 Carlsbad, Ca 92008 February 7, 2024 Project No. 171.1 Attention: Allan Teta; allan@trearch.com Subject: GEOR Letter and Second Revised 1st Response by Rock Solid Geotechnical to Review Comments 2668 Ocean Street, Carlsbad, California 92008 Proposed Single-Family Residence References: See Attached Dear Mr. Teta, In response to the referenced geotechnical report review comments, we have prepared this document to address geotechnical related review comments made on September 12, 2022, by the City of Carlsbad (Project ID: CDP2021-0025) (Grading Permit No.: GR2022-036). We have reviewed the referenced geotechnical reports prepared by Hetherington Engineering, Inc. (Hetherington) relative to the proposed new construction and we generally concur with the findings and recommendations with the exception of the updated recommendations provided by our response to the geotechnical review comments below. Rock Solid accepts responsibility as the geotechnical consultant of record for the construction of the single-family residence. This office generally concurs with the findings, conclusions, and recommendations from the referenced geotechnical engineering reports and responses to review comments by Hetherington (Reference 1, 2, and 3). Should you have any questions, please do not hesitate to contact the undersigned. Respectfully Submitted, Rock Solid Geotechnical, Inc. (Rock Solid). Jamie K. Fink President Professional Geologist 7626 Certified Engineering Geologist 2636 Sean P. Prenovost Associate Senior Engineer Professional Engineer 94193 GEOTECHNICAL J El 333 Third Street, Suite 2 Laguna Beach, CA 92651 949.558.9776 jamie@rocksolidgeotechnical.com www.rocksolidgeotechnical.com GEOR Letter and Second Revised 1st Response by Rock Solid Geotechnical to Review Comments Proposed Single-Family Residence 2668 Ocean Street, Carlsbad, California 92008 February 7, 2024 Project No. 171.1 Note: For convenience, we have rewritten the comments in italics. Our response is written directly below each comment. #1: The submitted “Geotechnical Investigation…” by Hetherington Engineering, Inc. is approximately 3-years old and addresses an antiquated code cycle (2016 CBC and ASCE 7-10, etc.) and development plan that appears to have since been at least locally revised. The reviewer further notes that the firm Hetherington Engineering, Inc., is no longer doing business. Consequently, a geotechnical update and change of consultant acknowledgement will be required from the new geotechnical consultant that will be performing the geotechnical services for the project moving forward. Response: As discussed on the cover page, Rock Solid accepts responsibility as the geotechnical consultant of record for the construction of the single-family residence. This office generally concurs with the findings, conclusions, and recommendations from the referenced geotechnical engineering reports and responses to review comments by Hetherington (Reference 1, 2, and 3). With the above in mind the State of California currently requires that buildings and structures be designed in accordance with the seismic design provisions presented in the 2022 California Building Code and in ASCE 7-16, “Minimum Design Loads for Buildings and Other Structures.” Based on site geologic conditions and on information from the subsurface exploration at the site, represented in the referenced geotechnical consultant reports, the site may be classified as Site Class D, in accordance with Chapter 20 of ASCE 7-16. Spectral Response Acceleration parameters and site coefficients may be taken directly from the U.S.G.S. website based on the longitude and latitude of the site. For site latitude (33.160772), longitude (-117.355131) and Site Class D, design parameters are presented on the table below. Table - 2022 CBC Seismic Design Criteria Seismic Parameters Site Class D Seismic Design Category (SDC) Null – See Section 11.4.8 Risk Category II Spectral Response (SS) 1.099 Spectral Response (S1) 0.397 g Spectral Response (SMS) 1.166 g Spectral Response (SM1) Null – See Section 11.4.8 Spectral Response (SDS) 0.777 g Spectral Response (SD1) Null – See Section 11.4.8 Site Coefficient (Fa ) 1.06 Site Coefficient (Fv) Null – See Section 11.4.8 Modified Peak Ground Acceleration PGAM 0.542 Source: OSHPD Seismic Design Maps, found at: https://seismicmaps.org/ 9 333 Third Street, Suite 2 Laguna Beach, CA 92651 GEOR Letter and Second Revised 1st Response by Rock Solid Geotechnical to Review Comments Proposed Single-Family Residence 2668 Ocean Street, Carlsbad, California 92008 February 7, 2024 Project No. 171.1 #2: With comment #1 above in mind, please provide a geotechnical update prepared by the new consultant acknowledging their review and acceptance of the Hetherington Engineering, Inc. work and “Geotechnical Investigation…” report for the project and providing updates of any sections of the report (code reference, seismic design parameters, etc.) as necessary to address the current project and currently adopted 2019 California Building Code and ASCE 7-16. Response: The recommendations provided in the referenced reports and response comments remain valid except were amended in our responses to review comments herein. #3: Please review the most current grading plan for the project and provide any additional geotechnical recommendations or modifications to the geotechnical report as necessary based on the current scope of the development. Response: Rock Solid has reviewed the referenced precise grading plans. Updated geotechnical recommendations are provided within our response to review comments by the City of Carlsbad herein. #4: Please provide an updated Geotechnical Map utilizing the most current revision of the grading plan for the project as the base map and at a sufficiently large scale to clearly show (at a minimum): a) existing site topography, b) proposed structures and improvements, c) proposed finished grades, d) geologic units, e) limits of proposed remedial grading, and f) the locations of the subsurface exploration. Response: An updated Geotechnical Map that utilizes the referenced precise grading plans that shows the existing site topography, proposed structures and improvements, proposed finished grades, geologic units, limits of proposed remedial grading, and the locations of the subsurface exploration. #5: Please provide updated seismic design parameters for the proposed development based on the 2019 California Building Code and ASCE 7-16. Response: The updated seismic design parameters for the 2022 California Building Code are provided in our response to review comment #1. #6: Please provide specific backcut recommendations to address the construction of the site retaining wall that is proposed immediately along and adjacent to the eastern property boundary. As it appears that an approximate 6’ cut will be necessary immediately along the property boundary to construct the proposed wall, the recommendations should full address the condition and provide guidelines as necessary to assure worker safety and protect adjacent off-site property from any adverse impacts from the proposed construction. If slot cutting and vertical cuts are proposed please provide dimensions and calculations demonstrating the stability of the proposed vertical cuts, widths of slots, and the time that the cuts may remain exposed. 9 333 Third Slnlel, Sulla 2 Laguna Beach, CA 92651 GEOR Letter and Second Revised 1st Response by Rock Solid Geotechnical to Review Comments Proposed Single-Family Residence 2668 Ocean Street, Carlsbad, California 92008 February 7, 2024 Project No. 171.1 Response: It is understood that a permanent shoring retaining wall is now being proposed, is based on onsite soil conditions, and correspondence with the project team. The recommendations for retaining walls in the referenced geotechnical engineering report remain applicable for shoring design and is provided below. Retaining walls free to rotate (cantilevered walls) should be designed for an active pressure of 40 psf/ft of depth (equivalent fluid pressure) and assumes level backfill. Any additional surcharge pressures behind the retaining wall from existing or proposed structures should be considered. A bearing capacity of 2,000 psf also remains applicable with a skin friction of 200 psf. A point of fixity at two feet below the proposed finished grade should be considered. #7: Please provide recommendations and parameters for shoring if necessary for the construction of the proposed site retaining wall along the eastern property boundary discussed above in comment #6. Response: Based on the redesign of the retaining wall foundations, it is our opinion that shoring will not be required. The proposed retaining wall can be constructed utilizing slot cutting techniques. The slot cutting recommendations are provided below and a representative from this office should observe all excavations for the proposed improvements. Once the temporary excavation has been stabilized the construction of the proposed retaining wall should be completed by a slot cut excavation as described below. An A-B-C construction sequencing method with a maximum width of 6 feet and a maximum vertical excavation of 4 feet may be utilized for areas that require greater than 4-foot vertical excavation to construct the proposed retaining walls should notify this office. Slot A-B-C construction method should follow the procedure sequence outlined below: 1. Trim the area of proposed excavation for the retaining wall at a 1:1 (horizontal: vertical) 2. Excavate ‘A’ slot sections to bottom of foundation elevation. 3. Set reinforcing at footing per detail with a minimum rebar extension on both sides of the footing as designed by the structural engineer. 4. Place concrete in accordance with the structural plans and allow at least 48 hours for concrete to cure. a. Compressive strength testing for concrete may be required to ensure concrete achieves adequate strength. 5. Construct the masonry retaining wall as designed by the structural engineer. 6. Allow at least 48 hours for grout to cure. a. Compressive strength testing for grout may be required to ensure grout achieves adequate strength. 7. Install the wall subdrain and waterproofing as designed by the structural engineer. 8. Backfill retaining wall active zone with free draining soils in accordance with the geotechnical recommendations (90% per ASTM D1557) to design finished grade prior to beginning slot cut excavations ‘B’ or ‘C’. 9 333 Third Slnlel, Sulla 2 Laguna Beach, CA 92651 GEOR Letter and Second Revised 1st Response by Rock Solid Geotechnical to Review Comments Proposed Single-Family Residence 2668 Ocean Street, Carlsbad, California 92008 February 7, 2024 Project No. 171.1 9. Excavate ‘B’ slot sections to bottom of foundation elevation and follow steps 3 through 8 above. 10. Excavate ‘C’ slot sections to bottom of foundation elevation and follow steps 3 through 8 above. A Slot Cut Diagram is provided as an attachment and should be referenced during excavation observations of the slot cuts. #8: Please discuss and evaluate site specific infiltration testing for potential storm water infiltration associated with the proposed project. Response: Based on our understanding of the referenced plans and conversations with the design team, there will not be any onsite detention systems and onsite water will outlet to the street. Attachments: Updated Geotechnical Map Slot Cut Figure 9 333 Third Slnlel, Sulla 2 Laguna Beach, CA 92651 GEOR Letter and Second Revised 1st Response by Rock Solid Geotechnical to Review Comments Proposed Single-Family Residence 2668 Ocean Street, Carlsbad, California 92008 February 7, 2024 Project No. 171.1 References 1. “GEOTECHNICAL INVESTIGATION, Proposed Single Family Residence, 2668 Ocean Street, Carlsbad, California,” by Hetherington Engineering, Inc., dated October 9, 2019, Project No. 8889.1. 2. “GEOTECHNICAL UPDATE, Proposed Two-Story Single-Family Residence, 2668 Ocean Street, Carlsbad, California,” by Hetherington Engineering, Inc., dated October 5, 2020, Project No. 8889.1. 3. “RESPONSE TO CITY OF CARLSBAD GEOTECHNICAL COMMENTS, Proposed Single-Family Residence Rear Yard Retaining Wall, 2668 Ocean Street, Carlsbad, California” by Hetherington Engineering, Inc., dated December 10, 2021, Project No. 8889.1. 4. “Grading Plans, 2668 Ocean Street SFD, Carlsbad” Pasco Laret Suiter & Associates, plot date: August 15, 2022. 9 333 Third Slnlel, Sulla 2 Laguna Beach, CA 92651 N GEOTECHNICAL MAP GEOTECHNICAL CONSULTANTS PROJECT NO.FIGURE NO. 012 10 200515 SCALE: 1" = 10' 171.1 2668 Ocean StreetCarlsbad, CAROCK SOLID GEOTECHNICAL, INC. LEGEND APPROXIMATE LOCATION OF HAND AUGER BORINGHA-2 HA-1 HA-2 1 APPROXIMATE LIMITS OF OVEREXCAVATION & RECOMPACTION BY HETHERINGTON ENGINEERING (2019) FILL TERRACE DEPOSITS APPROXIMATE LIMITS OF OVEREXCAVATION & RECOMPACTION 11 I I \ I l I t i I I I I I I I I I /, I ' 3 I m 3 3 NEIGH.00R'S EX. TRASH I ENCLOSURE .. r= EX. W JER SERVICE FOR APN 203-141'15 TO REMAIN 3 ex. ,, 'f "'_ j I i : /j J, I • ,,~11 1-1 EX. TREE TOR ~ ;,: EX PPT0 REWJN ~ 3:: J ~ Lf_• >< W3 I i . (l'X 40.13) jr 3 J NEWSEWERLATERAI. ' • ~ m PERCBA I -I S-1.SEE OSTOOWC ~ • --f ---SEWcR= ~-• --• ,--• --~. I 17 I I PEAGRAVELPERLS ~ 3 3 (EX 40.45) I-LU 3 LU A' c::: I-(/) /1 z 3 <( LU I (.) ,. • 0 .. I I I ~ PROP. TREE PER u~.:::ER SERVICE T~ BE " 3 METERPERC DTOl"SERVIGE&tfr (EX4040) BAD STO DWG Y/.JA SEE WATER NOTE • ,_, --Ml "llf"'E ~ __ ,,, I ; TRENCH RESURFACING PER CBAD STO [1WG 3 GS-25WPJ AP::ew SEWER LATERAL f"" I {EX 40.48) 200-Ut-15PERCBA0 -1 ~ - OWG S-7. SEE SEWER N:i 8 -f ---;--=-~ AB0Vfi -.. -i -__ 8 ·-· jl • j • i ~ \ I 3 I ~ • • FGU6 ROOF ABOVE [TYP) • APN 203-141-07 PRfVACE FENCE PER\s I N55"59'0-l'IU(9S' ' TC 420 IE 40_g; GARAGE ' ' ' ' ' ' ' '\ I \ I I I I \ • FS ,111 0 y \ \ I I I ··.:·.:·.·:··.·:··.:_:. 411 •• ' ' ' ' NGLE-FAMILY RESIDENCE FE, 42.27 PM41.6 •• ,_, • NCRETE l;ltlll.OG(T'tP) CURB PER I I \ '◄" I I D CON CRETE CURB PER L / APN 203-141-0I( / ~116 RET. WALL PER CTOR TO \/El'JFY ATI0NS UlffiT DISCREPANCIES I I I ACY Fl!HCE PER LS f G'8.Al Gf2~ 1 j-07 l V I r I K APN 203-141-15 T ◄O1/\Xalll'OSE0 APN 203-141-14 CONTRACTOR TO :r· WIII.L PER SORSO ~ &ALERT ENGINEER 0~':N~E~~HCREBORING ElEVATIONS PANCtES \ \ C. \ \ December 10, 2021 Project No. 8889.1 Log No. 21714 Pasco Laret Suiter & Associates 27127 Calle Arroyo, Suite 1904 San Juan Capistrano, CA 92675 Attn: Ms. Tara Goldberg Subject: RESPONSE TO CITY OF CARLSBAD GEOTECHNICAL COMMENTS Proposed Single-Family Residence Rear Yard Retaining Wall 2668 Ocean Street Carlsbad, California Dear Ms. Goldberg: In response to your request, we are providing responses to the geotechnical comments included on the e-mail provided by you dated November 8, 2021. Our numbering corresponding utilized on the e-mail. Our responses are as follows: 1. Retaining wall Type C-5 is considered appropriate for the proposed rear yard retaining wall from a geotechnical standpoint. 2. The proposed rear yard retaining wall can be constructed with slope cut grading instead of with a 1:1 (horizontal to vertical) slope above a 3-feet high vertical. If you should have any questions, please call our 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) Distribution: 1-via e-mail (tgoldberg@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 • • • • • • • • GEOTECHNICAL INVESTIGATION Proposed Single-Family Residence 2668 Ocean Street Carlsbad, California HETHERINGTON ENGINEERING, INC. HETHERINGTON ENGINEERING, INC. SOIL & FOUNDATION ENGINEERING • ENGIN EERING GEOLOGY • HYDROGEOLOGY TRE Architecture 300 Carlsbad Village Drive, Suite 108-336 Carlsbad, California 92008 Attention: Subj ect: Mr. Allan Teta GEOTECHNICAL INVESTIGATION Proposed Single-Family Residence 2668 Ocean Street Carlsbad, California References: Attached Dear Mr. Teta: October 9, 2019 Project No. 8889.1 Log No. 20676 In accordance with your request, we have performed a geoteclmical investigation for a proposed two-story over basement, single family residence at the subject site. Our work was performed in September and October 2019. The purpose of the investigation was to evaluate geologic and soil conditions in the area of proposed construction, and to provide grading and foundation recommendations. With the above in mind, our scope of work included the following: • Research and review of available geoteclmical reports, plans, and geologic maps/literature pertinent to the site (see References). • Subsurface exploration consisting of two manually excavated hand auger borings to depths of 11 m1d 11.5-feet for bulk and relatively undisturbed soil sampling, and geologic observation. • Laboratory testing of soil samples obtained from the subsurface exploration. • Engineering and geologic mmlysis. • Preparation of this repo1t providing the results of our field and laboratory work, analyses, and our conclusions m1d recommendations. 5365 Avenida Encinas, Suite A • Carlsbad, CA 92008-4369 • (760) 931-1917 • Fax (760) 931-0545 333 Third Street, Suite 2 • Laguna Beach, CA 92651-2306 • (949) 71 5-5440 • Fax (760) 931-0545 www.hetheringtonengineering.com GEOTECHNICAL INVESTIGATION Project No. 8889.l Log No. 20676 October 9, 2019 Page2 SITE DESCRIPTION The subj ect property is located 2668 Ocean Street in the city of Carlsbad, California (see Location Map, Figure 1). The site consists of a relatively level, rectangular shaped property that presently suppmis a one-story, single-family residence and concrete patios. The prope1ty is bounded by Ocean Street to the southwest and similarly developed prope1ties at similar elevations to the 1101iheast, northwest and southeast. RESEARCH Research at the City of Carlsbad resulted in obtaining no site-specific soils repmis or plans. A soils report for 2680 Ocean Street was located (Reference 3). The soils repo1i for 2680 Ocean Street is consistent with the findings of our subsmface exploration. PROPOSED DEVELOPMENT Based on discussion with you, and review of the architectural plans (Reference 11) and foundation plans (Reference 7), we understand that the proposed development consists of demolishing the existing improvements and constructing a new, two-story over basement, single-family residence. The footprint of the proposed structure is shown on the attached Plot Plan, Figure 2. We anticipate wood-frame and masonry/concrete construction founded on conventional continuous/spread footings with slab-on-grade ground floors. Building loads are expected to be typical for this type of relatively light construction. Grading is expected to consist primarily of the basement excavation. SUBSURFACE EXPLORATION Subsurface exploration consisted of drilling two hand auger borings to depths of 11 and 11.5-feet below existing site grades. The approximate locations of the borings 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 bedrock materials, and obtained bulk and relatively undisturbed samples for laboratory testing. The soils were visually classified according to the Unified Soil Classification System. Soil classifications are shown on the attached Boring Logs, Figures 3 and 4. HETHERINGTON ENGINEERING, INC. PROJECT NO.FIGURE NO.GEOTECHNICAL CONSULTANTS HETHERINGTON ENGINEERING,INC. ADAPTED FROM: The Thomas Guide, San Diego County, 57th Edition, Page 1106 SCALE: 1" - 2000'(1 Grid Equals: 0.5 x 0.5 miles) LOCATION MAP 1 2668 Ocean StreetCarlsbad, California 8889.1 N SlliE PACIFIC OCEAN GEOTECHNICAL INVESTIGATION Project No. 8889.1 Log No. 20676 October 9, 2019 Page 3 LABORATORY TESTING Laboratory testing was performed on samples obtained during the subsmface exploration. Tests performed consisted of the following: o Dry Density and Moisture Content (ASTI\I[: D 2216) 0 Soluble Sulfate (Cal. Test 417) o Direct Shear (ASTM: D 3080) o Maximum Dry Density/Optimum Moisture Content (ASTM: D 1557) o Expansion Index (ASTM: D 4829) Results of the ch}' density and moistme content determinations are presented on the Boring Logs, Figures 3 and 4. The remaining laboratory test results are presented on the Laboratory Test Results, Figure 5. SOIL AND GEOLOGIC CONDITIONS 1. Geologic Setting The subject site is located on a relatively level marine terrace that is contained within the coastal plain region of 1101thern 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 platfo1ms of underlying Eocene sedimentary bedrock and were formed dui·ing glacio-eustatic changes in sea level. The tenaces 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 subject prope1ty is contained within the southwest portion of the U.S.G.S San Luis Rey 7-1/2 minute quadrangle. Based on the results of our subsurface investigation, the site is underlain by topsoil, fill and Quaternary marine and non-marine tenace deposits. No known or repo1ted landsliding is known to exist on the site. No knovm or repo1ted active or potentially active faults exist within the site. HETHERINGTON ENGINEERING, INC. GEOTECHNICAL INVESTIGATION Project No. 8889.1 Log No. 20676 October 9, 2019 Page 4 2. Geologic Units a. Topsoil -Topsoil was encountered in boring HA-1 and consists of gray brown silly sand that is dry to damp, loose, and contains abundant roots/rootlets. b. Fill -The fill soils encountered in boring HA-2 consist of orange brown silty to gravelly sand that are moist and loose. c. Terrace Deposits -Encountered at a depth of approximately 1.5-feet in both borings are terrace deposits consisting of dry to moist, loose to medium dense, orange brown and light brown silty sand. The tenace deposits are considered suitable for supp01t of compacted fill and proposed improvements and possess a very low expansion potential. 3. Groundwater Groundwater was not encountered in the borings to the maximum depth explored of 11.5-feet. It should be noted, however, that fluctuations in the amount and level of grOlmdwater may occur due to variations in rainfall, inigation, and other factors that may not have been evident at the time of our field investigation. SEISMICITY The site is located within the seismically active southern California region. There aJe, however, no known active or potentially active faults presently mapped that pass through the site nor is the site located within the presently defined limits of an Alquist-Priolo Eaithquake Fault Zone. Active or potentially active fault zones within the site region include the Rose Canyon and Elsinore (Temecula Segment). Strong ground motion could also be expected from eaithqual(es occurring along the San Jacinto and San AndJeas fault zones, which lie northeast of the site at greater distances, as well as numerous other faults which lie offshore. HETHERINGTON ENGINEERING, INC. GEOTECHNICAL INVESTIGATION Project No. 8889.1 Log No. 20676 October 9, 2019 Page 5 The following table lists the known active faults that would have the most significant impact on the site: Maximum Probable Fault Earthquake Slip Rate (Moment Magnitude) (mm/year) Rose Canyon 7.0 1.5 (8 kilometers/5-miles southwest) Elsinore (Temecula Segment) 7.3 3 _(3 9 kilometers/24miles northeast) SEISMIC EFFECTS 1. Ground Accelerations The most significant probable earthquake to effect the site would be a 7.0 magnitude emthquake on the Rose Canyon fault. Based on Section 1803.5.12 of the 2016 California Building Code, peak ground accelerations (PGAM) of 0.484g are possible for the design earthquake. 2. Landsliding The risk of seismically induced landsliding to affect the site is considered low due to the level topography of the site. 3. Ground Cracks The risk of surface fault ruptme 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 to affect the site is considered low due to the dense underlying tenace deposits and absence of shallow groundwater. 5. Tsunamis The "Tsunami Inundation Map ... " (Reference 2) indicates the site is not located within a tsunami inundation zone. HETHERINGTON ENGINEERING, INC. GEOTECHNICAL INVESTIGATION Project No. 8889.1 Log No. 20676 October 9, 2019 Page 6 CONCLUSIONS AND RECOMMENDATIONS 1. General The proposed development is considered feasible from a geotechnical standpoint. Grading and foundation plans should consider the appropriate geotechnical features of the site. Provided that the recommendations presented in this repo1t and good constrnction practices are utilized during the design and construction, the proposed grading and construction is not anticipated to adversely impact adjacent properties from a geotechnical standpoint. 2. Seismic Parameters for Structural Desigri Seismic considerations that may be used for structural design at the site, based on Section 1613 of the 2016 Califo rnia Building Code and ASCE 7-10, include the fo llowing: a. Ground Motion -The proposed structure should be designed and constructed to resist the effects of seismic ground motions as provided in Section 1613 of the 20 16 California Building Code. Site Address: 2668 Ocean StTeet, Carlsbad, California Latitude: 33.16073°N Longitude: 117.35515° W b. Spectral Response Accelerations --Using the location of the property and data obtained from the U. S. G. S. Earthquake Hazard Program (Reference 9), short period Spectral Response Accelerations Ss (0.2 second period) and S1 (1.0 second period) are: Ss = 1.175g S1 = 0.451g c. Site Class -In accordance with Chapter 20 of ASCE 7-10 and the underlying geologic conditions, a Site Class D is considered appropriate for the subject property. HETHERINGTON ENGINEERING, INC. GEOTECHNICAL INVESTIGATION Project No. 8889.1 Log No. 20676 October 9, 2019 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 are: Fa= 1.030 Fv = 1.549 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 = 1.210g Sm1 = 0.699g f. Design Spectral Response Acceleration Parameters Sds and Sd1 -In accordance with Section 1613.3.4 and considering the values of Sms and Sm,, Design Spectral Response Acceleration Parameters for Maximum Considered Earthquake are: Sds = 0.807g Sd1 = 0.466g g. Long Period Transition Period -A Long Period Transition Period of TL = 8 seconds is provided for use in San Diego Cow1ty. h. Seismic Design Category -In accordance with Tables 1604.5, 1613.3 .5, and ASCE 7-10, a Risk Category II and a Seismic Design Category Dare considered appropriate for the subject prope1ty. 3. Site Grading a. Clearing and Grubbing -Existing site improvements, vegetation and miscellaneous debris should be removed to an appropriate offsite disposal area. Holes resulting from the removal of buried obstructions which extend below finished site grades, should be replaced with compacted fill or lean concrete. In the event that abandoned cesspools, septic tanks or storage tanks are discovered during the excavation of the site, they should be removed and backfilled in accordance with local regulations. Existing utility lines to be abandoned should be removed and capped in accordance with local requirements. b. Removal of Unsuitable Soils -Within the limits of the proposed improvements and to 3-feet beyond, where possible, existing topsoil, fill, disturbed tenace HETHERINGTON ENGINEERING, INC. GEOTECHNICJ-\l INVESTIGATION Project No. 8889.1 Log No. 20676 October 9, 2019 Page 8 deposits, and other unsuitable material should be removed to approved terrace deposits. Removal depths of 2 to 4-feet are anticipated. The actual depths and extent of removals should be determined by the Geotechnical Consultant during site grading. c. Scarification -Following removal of unsuitable soils, all areas to receive fill should be scarified to a minimum depth of 6 to 8-inches, brought to near optimum moisture content, and compacted to at least 90-percent relative compaction based upon ASTM: D 1557. d. Compacted Fill -Fill soils should be moisture conditioned to about optimum moisture content and compacted by mechanical means in unifonn horizontal lifts of 6 to 8-inches in thiclmess. All fill should be compacted to a minimwn relative compaction of 90-percent based upon ASTM: D 1557. The on-site materials are suitable for use as compacted fill. Rock fragments over 6-i.nches in largest dimension and other perishable or unsuitable materials should be excluded from the fill. All grading and compaction should be observed and tested by the Geotechnical Consultant. Any impmted soil should have a very low expansion potential and should be approved by the Geotechnical Consultant prior to import. 4. Temporary Excavations Temporary slopes necessaiy to facilitate site grading and the construction of retaining walls may be cut ve1tically up to 3-feet where the cuts are not influenced by existing sh·uctures or prope1ty line constraints. Any po1tion of temporaiy slopes neai· existing improvements, higher than 3-feet, or exposing potentially unstable soils should be sloped at a ratio no steeper than 1: 1 (horizontal to ve1ti.cal), slot cut, or shored. Due to primarily granular soi.ls caving should be expected. Field observations by the Engineering Geologist during grading of temporary slopes is recommended and considered necessary to confirm anticipated conditions and provide additional recommendations as warranted. Slot cut/shoring pai·aineters can be provided upon request. 5. Foundation and Slab Recommendations The following ai·e considered geotechnical minimums and may be increased by structural requirements. The proposed structure should be suppo1ted on conventional continuous/spread footings founded at least 18-inches into compacted fill and/or terrace deposits. \ HETHERINGTON ENGINEERING, INC. GEOTECHNICAL INVESTIGATION Project No. 8889.1 Log No. 20676 October 9, 2019 Page 9 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 h·enches should extend below a 1: 1 (horizontal to ve1tical) plane projected upward from the bottom of the trench. Foundations beming as recommended may be designed for a dead plus live load beaJing 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 to a maximum value of 2000-pounds-per- square-foot and a coefficient of friction between foundation soil and concrete of 0.35 may be assumed. These values asswne 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 are considered to be less than 3/4 and 3/8-inch, respectively, for foundations founded as recommended. Slab-on-grade floors should have a minimwn thickness of 5-inches and should be reinforced with #4 bars spaced at 18-inches, center-to-center, in two directions, and supp01ted on chairs so that the reinforcement is at mid-height in the slab. Floor slabs should be underlain with a minimun1 15-mil moisture vapor retarder. At least 2- inches of sand should be placed over the vapor retarder to assist in concrete cming and at least 2-inches of sand should be placed below the vapor retarder. The vapor retru·der should be placed in accordance with ASTM: E 1643. Prior to placing concrete, the slab subgrade soils should be thoroughly moistened. Vapor retarders me 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. 6. Retaining Walls Retaining walls free to rotate ( cantilevered walls) should be designed for an active pressure of 40-pounds-per-cubic-foot (equivalent fluid pressure) assuming level backfill consisting of onsite soils. Walls restrained from movement at the top should be designed for an at-rest eruth pressure of 60-pounds-per-cubic-foot (equivalent fluid pressure). Any additional surchru·ge pressures behind the retaining walls should be added to these values. HETHERINGTON ENGINEERING, INC. GEOTECHNICAL INVESTIGATION Project No. 8889 .1 Log No. 20676 October 9, 20,19 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 minimw11 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 approved filter fabric. Other subdrain systems that may be contemplated for use behind retaining walls due to the ultimate design and construction methodology will be considered on a case-by-case basis. Recommendations for wall wate1woofing should be provided by the Project Architect and/or Structmal Engineer. The lateral pressme on retaining walls due to earthqualce motions (dynamic lateral force) may be calculated as PA = 3/8 'Y H2kh where 'Y H dynamic lateral force (pounds/foot) unit weight= 120 pounds-per-cubic-foot height of wall (feet) seismic coefficient= 0.16 The dynamic lateral force may also be expressed as 14.4-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 H/3 above the base of the wall. The dynamic lateral force need not be applied to retaining walls 6-feet or less in height. 7. Retaining Wall and Utility Trench Backfill All retaining wall and utility trench backfill soils should be moisture conditioned to about optimum moisture content and compacted by mechanical means in wuform horizontal lifts. Lift thickness should be dependent on the type of equipment used for compaction, but in no case should exceed 8-inches in thickness. All utility trench backfill 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. Rock fragments over 6-inches in dimension and other perishable or unsuitable materials should be excluded from the fill. HETHERINGTON ENGINEERING, INC. GEOTECHNICAL INVESTIGATION Project No. 8889.1 Log No. 20676 October 9, 2019 Page 11 8. Conosivity A representative sample of the on-site soils was submitted for sulfate testing. The result of the test is summarized on the Laboratory Test Results, Figure 5. The sulfate content is consistent with a not-applicable sulfate exposure classification per Table 4.5.3 of the American Concrete Institute Publication 318. Consequently, special provisions for sulfate resistant concrete are not considered necessary. Other conosivity testing has not been performed, consequently, the on-site soils should be assumed to be severely corrosive to bmied metals tmless testing is performed to indicate otherwise. 9. Concrete Flatwork Concrete flatwork should be at least 5-inches thick (actual) and reinforced with #4 bars spaced at 18-inches on center (two directions) and placed on chairs so that the reinforcement is in the center of the slab. Slab subgrade should be thoroughly moistened prior to placement of concrete. Conh·action joints should be provided at 8- feet spacing (maximum). Joints should create square panels where possible. For rectangular panels (where necessary) the long dimension should be no more than 1.5 times the sho1i dimension. Joint depth should be at least 0.25 times the flatwork thickness. 10. Site Drainage The following recommendations are intended to mm1m1ze the potential adverse effects of water on the structure and appmienances. Surface drainage should be designed by the project Architect and/or Civil Engineer. a. Consideration should be given to providing the structure 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 structure. The on-site soils are generally sandy in nature and considered erodible if exposed to concentrated drainage. c. Landscaping planned adjacent to the sb.-ucture should be designed so as to minimize the amount of moisture that can penetrate the pad subgrade soils to prevent damage to the structure. Moisture accumulation or watering adjacent to foundations can result in deterioration of wood/stucco. HETHERINGTON ENGINEERING, INC. GEO TECHNICAL INVESTIGATION Project No. 8889.1 Log No. 20676 October 9, 2019 Page 12 d. Irrigated areas should not be over-watered. Inigation should be limited to that required to maintain the vegetation. Additionally, automatic systems should 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 clear 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. 11. Recommended Observation and Testing During Construction The following tests and/or observations by the Geotechnical Consultant are recmmnended: a. Observation and testing of grading. b. Observation of temporary slopes. c. Observation of foundation excavations pnor to placement of forms and reinforcing steel. d. Observation and testing ofretaining wall backdrains and backfill. e. Observation and testing of interior and exterior utility trench backfill. f. Observation and testing of concrete flatwork sub grade. 12. Grading and Foundation Plan Review Grading and foundation plans should be reviewed by the Geotechnical Consultant to confinn conformance with the recommendations presented herein or to modify the recmmnendations 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 fmiher assume the excavations to be representative of the subsurface conditions throughout the site. If different subsurface conditions from those encountered during our exploration are HETHERINGTON ENGINEERING, INC. GEOTECHNICAL INVESTIGATION Project No. 8889.l Log No. 20676 October 9, 2019 Page 13 observed or appear to be present in excavations, the Geotechnical Consultant should be promptly notified for review and reconsideration of the recommendations. Om 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 wananty, 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. 1v1 ngmeer ~,.,...___. eologist 3772 Geotechnical Engine ified Engineering Geologist 1153 ( expires 3/3 1/20) rtified Hydro geolo gist 591 Attachments: Location Plot Plan Boring Logs Laboratory Test Results Distribution: 4-Addressee I-via email (allan@tre.team) pires 3/31/20) Figure 1 Figure 2 Figures 3 and 4 Figure 5 HETHERINGTON ENGINEERING, INC. REFERENCES 1. ASCE 7-10, "Minimum Design Loads for Buildings and Other Structures," American Society of Civil Engineers/Structural Engineers Institute, dated May 20 10. 2. California Emergency Management Agency, "Tsunami Inundation Map for Planning, Oceanside Quadrangle/San Luis Rey Quadrangle," dated June 1, 2009. 3. East County Consultation and Engineering, Inc., "Limited Geo technical Investigation, Proposed Single-Fan1ily Residence, 2680 Ocean Street, City of Carlsbad, California 92008," dated March 2, 20 17. 4. ICBO, California Building Code, 20 16 Edition. 5. ICBO, "Maps of Known Active Fault Near-Source Zones in California and Adjacent Portions of Nevada," California Division of Mines and Geology, 1998. 6. Jennings, Charles W., "Fault Activity Map of California and Adjacent Areas," California Data Map Series, Map No. 6, dated 1994. 7. Palos Verdes Engineering, "Swan Residence, 2668 Ocean St., Carlsbad, CA.," dated Janumy 27, 2015 (Sheets Sl-S4, SD1-SD4, and SNl). 8. Peterson, Mark P., et al, "Documentation for the 2008 Update of the United States National Seismic Hazards Maps," USGS Open File Repo1t 2008-1128, dated 2008. 9. Structural Engineers Association, Emthqualce Hazard Program, Seismic Design Maps. 10. Tan, Siang S. and Kennedy, Michael P., "Geologic Maps of the Northwestern Pait of San Diego County, California", California Division of Mines and Geology, Open-File Report 96-02, dated 1996. 11. TRE Architecture, "Swan Residence, Cm-lsbad, California," dated November 25, 2014 (Sheets Al. 1, A2.1, A2.2, A3 . l, A4.1 and A4.2). 12. United States Geological Survey, "San Luis Rey 7.5-Minute Quadrm1gle," dated 1997. 13. Weber, F. Hm·old, "Recent Slope Failures, Ancient Landslides, And Related Geology of the N01th-Central Coastal Area, San Diego County, California," California Division of Mines and Geology, Open-File Report 82-12, dated 1982. 14. 2007 Working Group and California Emthqualce Probability, "The Uniform California Ea1thquake Rupture Forecast, Version 2 (UCERF-2)," USGS Open File Report 2007-1437 and California Geological Survey Special Report 23, dated 2008. HETHERINGTON ENGINEERING, INC. Project No. 8889.1 Log No. 20676 PLOT PLAN GEOTECHNICAL CONSULTANTS HETHERINGTON ENGINEERING,INC. PROJECT NO.FIGURE NO. 012 5 1015200 2668 Ocean StreetCarlsbad, California 8889.1 N SCALE: 1" = 10' 2 LEGEND APPROXIMATE LOCATION OF HAND AUGER BORINGHA-2 HA-1 HA-2 Base Map: TRE Architecture, "Swan Residence, Carlsbad , California," dated November 25, 2019 (Sheet A1.1). I I 20'-0" FRONT YARD SETBACK I ~! ~---N ------J ~ I I I P--------..--~- APN· 203-141-7 N5'"22'E 70• 2 STORY RESIDENCE WITH BASEMENT FF. 96.75@ GARAGE ! ~□□-~6~-L~~~-~~~~~~--------~ FENCE WOOD HUB , X=50!6. 78 ~ Y-4952551 Z=!00.00 [X SINGLE FAMILY RESIDENCE APN· 203-141 9 10'-0" REAR YARD SETBACK N5'"22 5' 101 100 101 108 106 SM TOPSOIL: Gray brown silty sand; dry to damp, loose, contains roots/rootlets WEATHERED TERRACE DEPOSITS: Orange brown silty sand; dry to damp, medium dense, contains roots/rootlets @4': Orange brown silty sand; moist, medium dense, scattered roots Total depth 11.5-feet No groundwater No caving 3.8 4.8 4.8 3.8 4.6 SO I L C L A S S . (U . S . C . S . ) 8889.1 3 40lb DR I V E S A M P L E BL O W S / F O O T DR Y D E N S I T Y (p c f ) MO I S T U R E CO N T E N T ( % ) RIG: DROP: INC. GEOTECHNICAL CONSULTANTS PROJECT NO. BORING NO. SOIL DESCRIPTION FIGURE NO. ELEVATION: DATE: BORING LOG 4"BORING DIAMETER:DRIVE WEIGHT:30" DE P T H ( F E E T ) BU L K S A M P L E 0.0 5.0 10.0 15.0 20.0 Mansolf Excavation '+ HA-1 DRILLING COMPANY: HETHERINGTON ENGINEERING, - 2668 Ocean Street 09/16/19 Carlsbad, California Hand Auger - -f-- --1 f-- -f-- -_I f-- -- -I f-- -f-- -I f-- -f-- -- -~I f-- -f-- -f-- -f-- -- -f-- -f-- -f-- -f-- I 106 112 105 106 105 SP ARTIFICIAL TURF: 1.5-inches thick FILL: Orange brown gravelly sand; moist, loose WEATHERED TERRACE DEPOSITS: Dark orange brown sand; moist, medium dense, contains scattered rootlets @7': Light orange brown sand; moist, medium dense Total depth 11.0-feet No groundwater No caving 7.5 8.5 7.4 5.9 6.2 SO I L C L A S S . (U . S . C . S . ) 8889.1 4 40lb DR I V E S A M P L E BL O W S / F O O T DR Y D E N S I T Y (p c f ) MO I S T U R E CO N T E N T ( % ) RIG: DROP: INC. GEOTECHNICAL CONSULTANTS PROJECT NO. BORING NO. SOIL DESCRIPTION FIGURE NO. ELEVATION: DATE: BORING LOG 4"BORING DIAMETER:DRIVE WEIGHT:30" DE P T H ( F E E T ) BU L K S A M P L E 0.0 5.0 10.0 15.0 20.0 Mansolf Excavation '+ HA-2 DRILLING COMPANY: HETHERINGTON ENGINEERING, - 2668 Ocean Street 09/16/19 Carlsbad, California Hand Auger - \ r ---f-- --1 f-- -f-- -I f-- --1 - -f-- -I f-- -f-- -f-- -~I - -f-- -f-- -f-- -- -f-- -f-- -f-- -f-- I LABORATORY TEST RESULTS Figure 5 Project No. 8889.1 Log No. 20676 SULFATE TEST RESULTS (Cal Test 417) Sample Location Soluble Sulfate in Soil (%) HA-1 @ 2 to 5’ 0.032 DIRECT SHEAR (ASTM: D 3080) Sample Location Angle of Internal Friction () Cohesion (psf) Remarks HA-1 @ 8’ 36 0 Undisturbed, soaked, consolidated, drained MAXIMUM DRY DENSITY/OPTIMUM MOISTURE CONTENT (ASTM: D 1557A) Sample Location Description Maximum Dry Density (pcf) Optimum Moisture Content (%) HA-1 @ 2 to 5’ Orange brown silty sand 130.0 9.5 EXPANSION INDEX (ASTM: D 4829) Sample Location Initial Moisture (%)Compacted Dry Density (pcf) Final Moisture (%) Expansion Index Expansion Potential HA-1 @ 2 to 5’ 8.4 115.7 13.8 0 Very low ATTERBERG LIMITS (ASTM: D 4318) Sample Location Liquid Limit (%) Plastic Limit (%) Plasticity Index (%) U.S.C.S. Class HA-1 @ 2 to 5’ - --Non-plastic