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Home My WebLink AboutCT 2017-0003; LA COSTA TOWN SQUARE PARCEL 3 RESIDENTIAL; GEOTECHNICAL REPORT AND RESPONSE FOR PROPOSED REPAIRS TO ANCHOR RETAINING WALL; 2023-07-12STANDALONE GEOTECHNICAL REPORT AND RESPONSE TO CITY OF CARLSBAD GEOTECHNICAL REVIEW MEMORANDUM DATED JULY 7, 2023, PROPOSED REPAIRS TO EXISTING ANCHOR RETAINING WALL NO. 1 LA COSTA TOWN SQUARE PROJECT CARLSBAD, SAN DIEGO COUNTY, CALIFORNIA APN 223-050-73-00 PROJECT ID: CT2017-0003 GRADING PERMIT NO.: GR2022-0001 FOR WOODSIDE 05S, LP 1250 CORONA POINTE COURT, SUITE 500 CORONA, CALIFORNIA 92879 W.O. 8144-B-SC JULY 12, 2023 CT 2017-0003 GR2022-0001 DWG 536-1A CONSTRUCTION CHANGE DELTA 1 Geotechnical C Geologic C Coastal C Environmental 5741 Palmer Way C Carlsbad, California 92010 C (760) 438-3155 C FAX (760) 931-0915 C www.geosoilsinc.com July 12, 2023 W.O. 8144-A-SC Woodside 05S, LP 1250 Corona Pointe Court, Suite 500 Corona, California 92879 Attention:Mr. Craig Moreas Subject:Standalone Geotechnical Report and Response to City of Carlsbad Geotechnical Review Memorandum Dated July 7, 2023, Proposed Repairs to Existing Anchor Retaining Wall No. 1, La Costa Town Square Project, Carlsbad, San Diego County, California, APN 223-050-73-00, Project ID: CT2017-0003, Grading Permit No.: GR2022-0001 Dear Mr. Moreas: In accordance with your request and authorization, (GSI) is providing the following responses to the July 7, 2023 geotechnical report review comments issued by the City of Carlsbad in regards to the proposed repair of existing Anchor Retaining Wall No. 1 at the subject parcel (City of Carlsbad, 2023 [see the Appendix]). Our services included reviews of the referenced documents listed in the Appendix, analysis of data, and the preparation of this response. Unless specifically superceded herein, the conclusions and recommendations contained in the project geotechnical reports prepared by GSI and referenced in the Appendix remain valid and applicable. RESPONSE TO GEOTECHNICAL REPORT REVIEW COMMENTS The geotechnical report review comments included in City of Carlsbad (2023) are repeated below in italics, followed by GSI’s response. City of Carlsbad (2023) Comment No. 1 The referenced “Review of Construction Change Rough Grading Plans, La Costa Town Square Project . . .” by GeoSoils, Inc. does not appear to address the damage and proposed repair of the existing MSE retaining wall. Consequently, please provide a standalone geotechnical report that describes and illustrates the damage to the existing MSE retaining wall and provides recommendations for repair from a geotechnical standpoint. The following comments are provided with the above in mind. GeoSoils, Inc. GSI’s Response Existing Anchor Retaining Wall No. 1 was damaged during the overnight hours of June 20 and 21, 2023 as a result of an unattended excavation created near the wall’s toe for the installation of a subdrain proposed for the mitigation of perched groundwater. The groundwater appears to be accumulating within the gravel bedding beneath the wall-facing units and within the gravel-filled trenches associated with the outlet pipes for the existing wall subdrain system. The perched groundwater was also observed seeping from “daylighted” discontinuities within the Delmar Formation and atop layers of slurry that apparently were placed during the original rough grading operations or during the construction of Anchor Retaining Wall No. 1, both of which were conducted under the geotechnical purview of Southern California Soil & Testing, Inc. and SCST, Inc. The perched groundwater was encountered within remedial grading excavations conducted near the retaining wall. There was no evidence of perched groundwater within this area of the project site during previous subsurface exploration performed by SCST, Inc. ([SCST], 2017) and GSI (2021) that followed the original rough grading of the subject parcel and the construction of Anchor Retaining Wall No. 1. The source of the perched groundwater is likely infiltrated rainwater from the above average 2022-2023 rainy season, or from up-gradient land use practices on the adjacent property to the north. The seepage is still occurring after roughly 3 months since its discovery. This suggests that the perched groundwater is being recharged, most likely by regional up-gradient sources. As indicated on Sheet 14 of the “Rough Grading Plans” prepared by SB&O, Inc. (2023), damage to existing Anchor Retaining Wall No. 1 occurs between approximate wall station numbers 2+31.50 and 2+85. As shown in Figure 1, the damage is confined to the wall-facing units. During reconnaissance mapping performed the morning of June 21, 2023, GSI did not observe readily visible evidence of tension cracks on the slope area above Anchor Retaining Wall No. 1 indicating relaxation of the geogrid-reinforced backfill or deep-seated instability at that time (Figure 2). In addition, the existing brow ditch directly behind the wall-facing units did not exhibit readily visible distress features indicating gross wall movement (Figure 3). When GSI arrived at the site the morning of June 21, 2023, much of the failure area was concealed by an emergency, temporary earthen buttress, placed by the grading contractor (Figure 1). This prevented observations of the wall toe within the failure area. However, based on communications with representatives of Geogrid Retaining Wall Systems, Inc. (the contractor who installed Anchor Retaining Wall No. 1), a cascading gravity failure of unsupported wall-facing units likely occurred as a result of raveling within the gravel bedding underlying the facing units. Since the exposed existing geogrid-reinforcement layers do not exhibit damage, Geogrid Retaining Wall Systems, Inc. is proposing to salvage and replace undamaged wall-facing units, and reconnect the geogrid-reinforcement layers to the wall units. Clean, crushed ¾- inch gravels will be placed and manually tamped with non-mechanized equipment behind Woodside 05S, LP W.O. 8144-B-SC La Costa Town Square, Carlsbad July 12, 2023 File:e:\wp21\8100\8144.sgr Page 2 SITE PHOTOGRAPHS Geotechnical • Geologic • Coastal • Environmental DATE 07/23 W.O. 8144-B-SC Figure 1 Photograph 1. Photograph of the failed portion of the facing units for existing Anchor Retaining Wall No. 1 taken during the morning of June 21, 2023. Note the exposed, undamaged geogrid reinforcement layers and the absence of raveling within the gravel drain column. The soil in front of the wall was placed by the grading contractor to serve as a temporary earthen buttress. Photographic view direction is to the north. SITE PHOTOGRAPHS FIGURE 2 SCALE: NTS DATE: 07/23 W.O. 8144-B-SC Photograph 2. Photograph of the slope area above the failed wall facing units taken during the morning of June 21, 2023. Note the absence of tension cracks on the slope face. Photographic view direction is to the northeast. G SITE PHOTOGRAPHS Geotechnical • Geologic • Coastal • Environmental DATE 07/23 W.O. 8144-B-SC Figure 3 Photograph 3. Photograph of the concrete brow ditch above the failed wall facing units taken during the morning of June 21, 2023. Photographic view direction is to the east. G GeoSoils, Inc. the replaced facing units. The repair will require the removal of additional wall-facing units located above an approximately 1:1 (horizontal:vertical [h:v]) plane, along the face of the wall, to the west and east of wall station numbers 2+31.50 and 2+85, respectively. The approximate extent of the wall failure and repair areas are shown on Figure 4, which is adopted from sheet 4 of SB&O, Inc. (2023). From a geotechnical perspective, we recommend that geotechnical observations and monitoring be conducted during the removal of the remaining wall-facing units within the proposed repair area shown on sheet 14 of SB&O, Inc. (2023). The wall repair should conform to the specifications included in the original plans for Anchor Retaining Wall No. 1, prepared by Red One Engineering and those provided on Sheet 14 of SB&O, Inc. (2023). The ¾-inch gravel used to backfill the area behind the replaced facing units should be placed in relatively thin (approximately 6- to 8-inch) lifts and densified using a non- mechanized hand tamper. GSI should observe the placement and densification of the gravel bed upon suitable bearing materials (if required); the reconnection of the geogrid- reinforcement layers to the wall-facing units; and the densification of the gravel backfill. City of Carlsbad (2023) Comment No. 2 Please provide a 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 and label the location of the damaged portion of the MSE retaining wall and the limits of the proposed repair. GSI’s Response See Figure 4. City of Carlsbad (2023) Comment No. 3 Please provide a geotechnical cross-section cut through the damaged portion of the MSE retaining wall illustrating the existing (damaged) condition of the wall and also the proposed repaired condition of the wall. GSI’s Response See Figures 5 and 6. City of Carlsbad (2023) Comment No. 4 Please provide complete geotechnical recommendations for the proposed repair of the existing MSE retaining wall (general geotechnical recommendations, recommendations for temporary slopes during the proposed removal of the wall facing units, recommendations Woodside 05S, LP W.O. 8144-B-SC La Costa Town Square, Carlsbad July 12, 2023 File:e:\wp21\8100\8144.sgr Page 6 W.O.DATE:SCALE:8144-B-SC 07/23 1" = 10' Figure 4 GEOTECHNICAL MAP DRAFT N.A.P.N.A.P.N.A.P. Afw Td Afc 2 Afw Td Afc 2 Afw Td Afc 2 Afw Td Afw Td Afw Td Afc 3 Td Afc3 Td Afc3 Td Afc 3 Td Afc Td Afu 3 Afc Td Afu 3 Afu Td Afu Td Afw Td Afu GSI LEGEND Afc3 Afc2 Afw Afc1 Afu Td N.A.P. ALL LOCATIONS ARE APPROXIMATE This document or efile is not a part of the Construction Documents and should not be relied upon as being an accurate depiction of design. NAfu Td Afc3 Td F. ? ? 0 0 7 0 r G ~- AR11RCIAL RLL -UNDOCUMENTED (TEMPORARY EARTHEN BUTTRESS) AR11RCIAL RLL -COMPACTED, PLACED DURING RECENT RDIEDIAL GRADING, ORa.ED M-IERE BURIED AR11RCIAL RLL -COMPACTED, PLACED FOR THE CONS1RUC110N OF THE RLL SLOPE ABO~ 1HE RflNFORCED BAa<FILL UNDER THE PUR'rfEW OF SOUTHERN CALIFORNIA SOIL & TES11NG, INC. (2015), ORa.ED M-IERE BURIED AR11RCIAL RLL -COMPACTED, RLL PLACED DURING THE CONS1RUC110N OF EXIS11NG ANa-tOR RETAINING WALL NO. 1 UNDER THE PIJRl,fEW OF SOUTHERN CALIFORNIA SOIL ct TESTING, INC. {2015), CIRa.ED Mf-lERE BURIED AR11RCIAL RLL -COMPACTED, RLL PLACED DURING MASS GRADING OPERA 110NS UNDER 1HE PURl,fEW OF SOUTHERN CALIFORNIA SOIL & TES11NG, INC. {2015). ORa.ED Mf-lERE BURIED TER11ARY DELMAR FORMA 110N, ORa.ED Mf-lERE BURIED APPROXIMATE LOCA 110N OF GEOLOGIC CONTACT, DOTTED Mf-lERE BURIED, QUERIED Mf-lERE UNCERTAIN APPROXJMA TE AREA OF DAMAGED MS£ RETAINING WALL FAONG ~--APPROXIMATE AREA OF MSE RETAINING WALL FACING ~ TO BE RDIOVED FOR 1HE PROPOSED WALL REPAIR f2 ------, ____ ._ _______ NO_T_A_P._A-RT_OF_m_,s_s_ru_n_r _______ ----1 ~ GRAPHIC SCALE 10 0 5 10 20 1" = 10' ~- ALL LOCATIONS ARE APPROXIMATE This document or efile is not a part of the Construction Documents and should not be relied upon as being an accurate depiction of design. W.O.DATE:SCALE:8144-B-SC 07/23 NTS Figure 5 SCHEMATIC GEOLOGIC CROSS SECTION (EXISTING [DAMAGED] CONDITION) DRAFTTdTd Afc1 Afc 2 Afc 3 Afw GSI LEGEND Afc 3 Afc 2 Afw Afc1 GEOGRID REINFORCEMENT LAYER PER DWG 474-7A Afu WALL SUBDRAIN SYSTEM PER DWG 474-7A Td Afu Afw EXPOSED GRAVEL DRAIN COLUMN CABLE RAILING SLEEVE-IT 1224R ? 0/ 0 0 I ?o " 0 -· ··-· .. -. _._·:: -. -·· 0 0 0 -• -• I /,, 0 0 ___ o --~/,/ 0 ._o. 0 0 0 0 0 0 ---?_, ARTIFICIAL FILL -UNDOCUMENTED (TEMPORARY EARTHEN BUTTRESS) ARTIFICIAL FILL -COMPACTED, PLACED DURING RECENT REMEDIAL GRADING ARTIFICIAL FILL -COMPACTED, PLACED FOR THE CONSTRUCTION OF THE FILL SLOPE ABOVE THE REINFORCED BACKFILL UNDER THE PURVIEW OF SOUTHERN CALIFORNIA SOIL & TESTING, INC. (2015) ARTIFICIAL FILL -COMPACTED, FILL PLACED DURING THE CONSTRUCTION OF EXISTING ANCHOR RETAINING WALL NO. 1 UNDER THE PURVIEW OF SOUTHERN CALIFORNIA SOIL & TESTING, INC. (2015) ARTIFICIAL FILL -COMPACTED, FILL PLACED DURING MASS GRADING OPERA RONS UNDER THE PURVIEW OF SOUTHERN CALIFORNIA SOIL & TESTING, INC. (2015) APPROX/MA TE LOCA noN OF GEOLOGIC CONTACT, QUERIED WHERE UNCERTAIN W.O.DATE:SCALE:8144-B-SC 07/23 NTS Figure 6 SCHEMATIC GEOLOGIC CROSS SECTION (PROPOSED [REPAIRED] CONDITION) DRAFT ALL LOCATIONS ARE APPROXIMATE This document or efile is not a part of the Construction Documents and should not be relied upon as being an accurate depiction of design. Td Td Afc1 Afc 2 Afc 3 Afw GSI LEGEND Afc 3 Afc 2 Afw Afc1 GEOGRID REINFORCEMENT LAYER PER DWG 474-7A WALL SUBDRAIN SYSTEM PER DWG 474-7A Td PROPOSED SUBDRAIN PER DETAIL "A" ON SHEET 4 OF SB&O, INC. (2023) CABLE RAILING SLEEVE-IT 1224R REPLACED WALL FACING UNITS 0 0 0 0 --- 0 0 0 0 . -~-· -.·. _ .. _. · . ·:: ·. ·. . . ... -·-· .··._:·_. ·. -.. -·.• . -·, I 0 0 ?o .. 0 0 . . . 0 0 ._o . 0 0 0 0 0 0 C ?------? ---?_, ARTIFICIAL FILL -COMPACTED, PLACED DURING RECENT REMEDIAL GRADING AND PROPOSED SUBDRAIN CONSTRUCTION ARTIFICIAL FILL -COMPACTED, PLACED FOR THE CONSTRUCTION OF THE FILL SLOPE ABOVE THE REINFORCED BACKFILL UNDER THE PURVIEW OF SOUTHERN CALIFORNIA SOIL & TESTING, INC. (2015) ARTIFICIAL FILL -COMPACTED, FILL PLACED DURING THE CONSTRUCTION OF EXISTING ANCHOR RETAINING WALL NO. 1 UNDER THE PURVIEW OF SOUTHERN CALIFORNIA SOIL & TESTING, INC. (2015) ARTIFICIAL FILL -COMPACTED, FILL PLACED DURING MASS GRADING OPERA RONS UNDER THE PURVIEW OF SOUTHERN CALIFORNIA SOIL & TESTING, INC. (2015) APPROX/MA TE LOCA noN OF GEOLOGIC CONTACT, QUERIED WHERE UNCERTAIN GeoSoils, Inc. addressing the condition of the geogrid and attachment to the wall facing units as necessary, recommendations for the placement and the specifications for the backfill material (size of gravel, etc.) that should be used behind the wall facing units as part of the replacement of the wall, observation/testing during the repair, etc.). GSI’s Response GSI is not the geotechnical consultant-of-record for Anchor Retaining Wall No. 1, and defers to the approved wall plans (Red One Engineering, Inc., 2015) for geotechnical guidance, including temporary stability. Please note that the proposed repair to existing Anchor Retaining Wall No. 1 is intended to replace the failed wall facing. The proposed repair does not involve the removal and replacement of the geogrid-reinforced backfill or geogrid reinforcements. Recommendations for wall construction are provided on the approved wall plans (Red One Engineering, Inc., 2015). Specifications for the proposed wall repair are provided on Sheet 14 of SB&O, Inc. (2023). The suitability of the existing geogrid-reinforcement layers and their reconnection to the wall-facing units should be evaluated by the wall designer during repair. As shown in Figure 1, in their post-failure condition, the geogrid-reinforced backfill and gravel drain column are essentially maintaining a similar slope gradient as the batter of the wall facing. There were no indications of tension cracks along the slope area above the failed portion of the wall that would suggest relaxation of the geogrid-reinforced backfill or gross wall instability. Thus, the temporary slope appeared stable at that time. However, GSI recommends that we observe and monitor the condition of the existing geogrid- reinforced backfill and the overlying slope within the repair area during removal and restoration of the wall-facing units. The clean, crushed ¾-inch gravel used to backfill the area behind the replaced facing units should be placed in relatively thin (approximately 6- to 8-inch) lifts and densified using a non-mechanized hand tamper. Densification by vibratory methods is not recommended as it could result in the raveling or settlement of the existing gravel. City of Carlsbad (2023) Comment No. 5 Please provide statement discussing the stability of the approximate 20' high MSE retaining wall at the phase of the proposed repair when the wall facing units have been removed from the area of repair as indicated on sheet 14 of the submitted rough grading plans. GSI’s Response Again, GSI is not the geotechnical consultant-of-record for Anchor Retaining Wall No. 1. Based on our observations of the generally intact conditions of the exposed geogrid- reinforced backfill and the gravel drain column where the wall-facing units failed, and the absence of readily visible distress features along the brow ditch, as well as the lack of tension cracks throughout the slope area above the failed portion of the wall facing (see Figures 1 through 3), the approximate 20-foot high MSE retaining wall does not exhibit Woodside 05S, LP W.O. 8144-B-SC La Costa Town Square, Carlsbad July 12, 2023 File:e:\wp21\8100\8144.sgr Page 10 GeoSoils, Inc. features that indicate instability at this time. However, delaying the proposed wall repair further increases the potential that temporary stability will be adversely impacted. Thus, GSI strongly recommends that the wall be repaired immediately. City of Carlsbad (2023) Comment No. 6 With respect to the location of the proposed subdrain and associated trench fronting the existing MSE retaining wall (and also backing buildings 5 through 16), please provide the basis for recommending the use of a plane of influence of 0.5:1 (H:V) to address potential influence/surcharge from the adjacent MSE wall and building versus the typical and more conservative 1:1 (H:V). GSI’s Response Since the load imparted by Mechanically Stabilized Earth (MSE) Anchor Retaining Wall No. 1 is distributed over an area that is roughly equivalent to the length of the wall multiplied by the length of the geogrid reinforcements, which according to Red One Engineering, Inc. (2015) vary between 21 and 23 feet, potential influence/surcharge from the retaining wall on the proposed subdrain is considered negligible. In other words, the wall is essentially a reinforced mass of compacted fill with an erosion-resistant facing that will not impose a concentrated load on the subdrain. In addition, a contoured bulb of vertical pressure on a strip footing typically shows a primary (most conservative) zone of influence starting from the bottom, outer edge of the footing, down at a gradient of a:1 (h:v). Typically, by a depth of 24 inches, a 24-inch wide footing has induced about 50 percent of its load. Given that the planned residential structures will be supported by post- tensioned slab foundations with deepened perimeter grade beams, which will also distribute the building loads over a broader area and act as a rigid structural element, it is our opinion that the use of a 0.5:1 (or ½:1 [h:v]) slope gradient to define the plane of influence is a reasonably conservative approach. City of Carlsbad (2023) Comment No. 7 At the completion of the proposed repair of the damaged section of the MSE retaining wall, an as-built geotechnical report should be prepared that describes the repair that was performed and provides the results of all geotechnical observation and testing services that were performed as part of the repair. GSI’s Response The requested as-built geotechnical report will be provided at the conclusion of the repairs to Anchor Retaining Wall No. 1. Woodside 05S, LP W.O. 8144-B-SC La Costa Town Square, Carlsbad July 12, 2023 File:e:\wp21\8100\8144.sgr Page 11 GeoSoils, Inc. LIMITATIONS Inasmuch as this study is based upon our review and engineering analyses, the conclusions and recommendations are professional opinions. These opinions have been derived in accordance with current standards of practice, and no warranty is express or implied. Standards of practice are subject to change with time. GSI assumes no responsibility or liability for work or testing performed by others, or their inaction; or work performed when GSI is not requested to be onsite, to evaluate if our recommendations have been properly implemented. Use of this report constitutes an agreement and consent by the user to all the limitations outlined above, notwithstanding any other agreements that may be in place. In addition, this report may be subject to review by the controlling authorities. Thus, this report brings to completion our scope of services for this portion of the project. Woodside 05S, LP W.O. 8144-B-SC La Costa Town Square, Carlsbad July 12, 2023 File:e:\wp21\8100\8144.sgr Page 12 GeoSoils, Inc. The opportunity to be of service is sincerely appreciated. If you should have any questions, please do not hesitate to contact our office. Respectfully submitted, GeoSoils, Inc. John P. Franklin Stephen J. Coover Engineering Geologist, CEG 1340 Geotechnical Engineer, GE 2057 RBB/JPF/SJC/sh Attachments:Appendix - References Distribution:(1) Addressee (PDF via email) Woodside 05S, LP W.O. 8144-B-SC La Costa Town Square, Carlsbad July 12, 2023 File:e:\wp21\8100\8144.sgr Page 13 GeoSoils, Inc. APPENDIX REFERENCES GeoSoils, Inc. APPENDIX REFERENCES City of Carlsbad, 2023, Geotechnical report review memorandum, La Costa Town Square, MSE retaining wall repair, project id: CT2017-0003, grading permit no.: GR2022- 0001, dated July 7. GeoSoils, Inc., 2023a, Memorandum: Geotechnical review of post tension plans, La Costa Town Square affordable project, City of Carlsbad, California APN 223-050-73-00, W.O. 8144-A-SC, dated July 10. _____, 2023b, Memorandum: Review of construction change rough grading plans, La Costa Town Square project, City of Carlsbad, California, APN 223-050-73-00, project no.: CT 2017-0003, drawing no.: 536-1A, W.O. 8144-B-SC, dated June 29. _____, 2023c, Geotechnical update and addendum to “Geotechnical Due Diligence Report and Attachments, La Costa Town Square Project, City of Carlsbad, California APN 223-050-73-00" W.O. 8144-A-SC, dated February 9, 2023, W.O. 8144-A-SC, dated June 20. _____, 2023d, Memorandum: Geotechnical recommendations for subdrain construction north of planned building pads for Lots 6 through 16 and Private Driveways “C” through “H”, La Costa Town Square project, City of Carlsbad, California APN 223- 050-73-00, project no.: CT 2017-0003, drawing no.: 536-1A, W.O. 8144-B-SC, dated May 30. _____, 2023e, Memorandum: Review of precise grading plans, La Costa Town Square project, City of Carlsbad, California APN 223-050-73-00, project no.: CT 2017-0003, drawing no.: 536-1A, W.O. 8144-B-SC, dated May 30. _____, 2023f, Memorandum: Geotechnical due diligence report and attachments, La Costa Town Square project, City of Carlsbad, California, APN 223-050-73-00, W.O. 8144-A-SC, dated February 9. _____, 2022a, Geotechnical plan review, La Costa Town Square project, City of Carlsbad, California, APN 223-050-73-00, W.O. 8144-A-SC, dated August 15. _____, 2022b, Review and response to third party geotechnical review comments, La Costa Town Square townhome site (APN 223-050-73-00), La Costa Boulevard, City of Carlsbad, California, W.O. 8144-A-SC, dated March 24. _____, 2021, Geotechnical due diligence evaluation of the La Costa Town Square townhome site, APN 223-050-73-00, La Costa Avenue, City of Carlsbad, San Diego County, California 92011, W.O. 8144-A-SC, dated June 17. GeoSoils, Inc. Red One Engineering, Inc., 2015, La Costa Town Square - office, Anchor retaining wall plan, 6 sheets, various scales, project no.: C.T. 08-07, drawing no.: 474-7A, dated July 16 (delta 1 [as-built]). SB&O, Inc., 2023, Rough grading plans for: La Costa Town Square,” 14 sheets, various scales, project no.: CT 2017-0003, drawing no.: 536-1A, construction change plan set dated June 29. SCST, Inc., 2017, Limited geotechnical investigation, La Costa Town Square multi-family housing, La Costa Boulevard, Carlsbad, California, SCST no.: 160518N, report no.: 1, dated February 28. _____, 2015, Final as-graded geotechnical report, La Costa Town Square - office development, La Costa Avenue, Carlsbad, California, tract no.: C.T. 01-09, SCST no.: 1211179, report no.: 70, dated November 13. Southern California Soil & Testing, Inc., 2013, Interim as-graded geotechnical report, La Costa Town Square commercial development, pads 1 through 10, 14, and 22, and office development, La Costa Avenue, Carlsbad, California, project nos: C.T. 01-09 and C.T.08-07, SCS&T no: 1211179, report no.: 25, dated July 2. Woodside 05S, LP Appendix File:e:\wp21\8100\8144b.sgr Page 2