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HomeMy WebLinkAboutCDP 14-05; TIERRA DEL ORO RESIDENCE; FINAL SOILS REPORT; 2020-08-24 24 August 2020 Thomas J. Taylor Construction, Inc. Job No. 13-10316 Attn: Mr. Dean Jahr Via email at: DJ@thomasjtaylorconstruction.com Subject: Report of Final Grading Observations and Soil Testing Tierra Del Oro Residential Project 5039 Tierra Del Oro Carlsbad, California In accordance with your request, Geotechnical Exploration, Inc. hereby presents this report of final observations and testing performed during the construction phase for the project at the subject site. The work reported herein was performed between July 5, 2016, and March 6, 2020. We previously performed a geotechnical investigation of the site, the results of which were presented in our “Report of Geotechnical Investigation and Coastal Bluff Edge Evaluation” dated November 12, 2013. In addition, the following documents have been issued by our firm: 1. Response of Coastal Bluff Edge Comments dated July 30 and August 4, 2014. 2. Addendum to Report of Geotechnical Investigation dated September 11, 2014. 3. Updated Addendum to Report of Geotechnical Investigation dated November 11, 2014. 4. Response to California Coastal Commission Appeal Staff Report dated July 8, 2015. 5. Foundation Plan Review dated January 25, 2016. Tierra Del Oro Project Job No. 13-10316 Carlsbad, California Page 2 6. Updated Reports of Preliminary Geotechnical Investigation dated January 27 and March 23, 2016. 7. Completion of Basement Level Pad Rough Grading dated July 25, 2016. 8. Addendum to Completion of Basement Level Pad Rough Grading dated August 10, 2016. 9. Report of Grading Observations and Soil Testing dated October 18, 2017. SITE DESCRIPTION The property is more particularly described as Assessor’s Parcel No. 210-020-08-00, Lot 8, according to Recorded Map 3052, in the City of Carlsbad, County of San Diego, State of California. Refer to the Vicinity Map, Figure No. I, for the location of the property. The property is located on the west side of the cul-de-sac at the south end of Tierra Del Oro in Carlsbad, California. Improvements on the lot prior to grading extended from the street to the top of westerly descending rip-rap (previously installed coastal protection consisting of multi-ton angular boulders) that toes out at the beach. Access to the existing garage was provided by a concrete driveway at the southeast corner of the property and an additional concrete drive that descended to the west along the north property line. For purposes of this report, it is assumed that the front of the property faces east. Two structures existed on the westerly descending lot. The easterly structure was single-story and included a two-car garage and an office/apartment living space. The westerly primary structure was two stories high and the main level was approximately 5 to 6 feet lower than the street elevation. The main living area was above a lower- level living space and utility area. The lower-level opened to the rear yard with beach access. Tierra Del Oro Project Job No. 13-10316 Carlsbad, California Page 3 Both structures were of wood frame and stucco construction. The easterly structure was founded on a slab on-grade without a perimeter footing. The eastern portion of the primary structure was founded on a raised wood floor with a perimeter footing and interior piers. The western portion was founded on retaining walls with perimeter footings and a slab on-grade. Other improvements consisted of a large paver patio and entry courtyard between the two structures, a concrete driveway, concrete walkways, stairs and patios, and a concrete ramp extending from the street down to the beach along the north property line. The property is bounded to the north and south by similar residential properties; to the east by the southern cul-de-sac terminus of Tierra Del Oro; and to the west by a westerly descending slope covered with rip-rap and the sand beach of Pacific Ocean. Based on review of the referenced topographic survey, elevations across the site range from approximately 37 feet above Mean Sea Level (MSL) per NVGD29 along the eastern property line and approximately 24 feet above MSL at the western edge of the existing main building pad to the west. The coastal bluff and property descend westward from this elevation to the beach and Pacific Ocean. The rip-rap seawall and a wall-enclosed recreation area underwent some repairs due to storm damage in 1979 and were subsequently removed to allow placement of additional rip-rap as described below. Properties to the north and south of the subject property are also protected by rip-rap. Tierra Del Oro Project Job No. 13-10316 Carlsbad, California Page 4 The western portion of the lot, in the bluff area, was heavily vegetated with a relatively thick growth of iceplant. Other ornamental plants were located in planters adjacent to the structures. The newly constructed residence consists of two floors with an expanded addition to the basement level, and newly placed pool on the west side of the property overlooking the ocean. Exterior improvements to the north include pavers with planters draining down to the west. A courtyard, gate house, wood deck, and wood terrace were added in between the area of the new structure and the existing garage with guest house located on the east side of the property. The south side improvements include planters and drainage to the west. Refer to Figure No. II, the Plot Plan, for the general configuration of the property, location of new room additions and improvements and limits of the observed grading. SCOPE OF SERVICES Our scope of services consisted of providing grading observations, consultation, and soil testing in areas to receive new improvements and foundations, and testing of new fill and backfill soils placed in building pad areas, trenches or behind retaining walls. In addition, we performed laboratory testing on collected soil samples. Our services were provided at the request of the project contractor or representative. Finally, as part of our services, we are providing this as-graded report. SOIL TESTING Representative soil samples were collected during grading to determine laboratory maximum dry density of the soils per ASTM D1557-12e1. Density tests were performed at the approximate locations shown on the Plot Plan (Figure No. II). Field Tierra Del Oro Project Job No. 13-10316 Carlsbad, California Page 5 density tests were taken in accordance with ASTM D6938-10 and are attached as Figure Nos. IIIa-b. Laboratory soil test results are attached on Figure No. IIIc. FIELD OBSERVATIONS AND SOIL TESTING 1. July 5, 2016: The garage was the only structure left intact from previously existing structures. A sample of the on-site material was taken to determine its maximum dry density in the laboratory. 2. Our representative observed and tested the lower level pad subgrade soils on July 20 and July 21, 2016. The lower level pad was cut into formational material and the soil surface was properly rolled and moisturized. Shoring was placed on the north and south property lines but was not observed by our firm. 3. The bottom of the pool excavation was observed on July 26, 2020, and found to be in dense/firm soils. A field memo was issued for the pool excavation bottom. 4. Footing excavation subgrade soils were observed intermediately between August 16, 2016, and January 20, 2017. The observed footing excavations include the intermediate level and the lower level of the structure; the excavations for the lower level interior (spread and column) footings located between building lines 1 through 11 on the plans; the excavations for the west perimeter exterior continuous footings of the residential structure and the short extension of the north basement retaining wall footing located to the west; the excavations for the lower basement and mid-landing from approximately grid line 10 to the east end of the basement; the new front garage remodel/addition underpinning and new footing excavations for the Tierra Del Oro Project Job No. 13-10316 Carlsbad, California Page 6 southwest, south, east, and north locations of the existing garage; and the courtyard door. The approved footings were observed to be founded in dense/firm formational soils or recompacted fills and a field memo was issued. 5. Utility plumbing trench backfill was observed intermediately between August 16 and November 16, 2016. The plumbing trenches probed very firm/dense. A vibratory plate was used to smooth out the surface. 6. Waterproofing (Polyguard 650) and drainage (MiraDrain with total drain) was placed on September 12, 2016, on the lower level basement’s north and east retaining walls. The water flow was adjusted to flow to the northwest corner tanks. 7. Backfill placement for the lower level basement retaining walls was observed and tested between October 3, 2016, and January 18, 2017, and included the wall located to the east, the landing wall, the central basement retaining wall, the intermediate level landing retaining wall, and the south retaining wall. Prior to backfill placement, waterproofing and drainage behind the upper basement, and the intermediate level basement walls located on the south and the east, were placed. The J-drain was connected to the lower level basement. North and south wall waterproofing and back drainage were observed to be in place. Waterproofing and back drainage for the lower 4 feet of the south side wall was also observed. Tierra Del Oro Project Job No. 13-10316 Carlsbad, California Page 7 8. Slab subgrades were intermediately observed between October 11 and November 16, 2016. The observed slabs include the lower basement level slab, the intermediate level slab, and the mid-level slab. Vapor barrier and properly compacted sand were placed for the lower level slab and intermediate level slab. 9. Our representative observed and tested the new east entry ramp located on the intermediate level landing area on November 29 and 30, 2016. 10. The central courtyard wall backfill was observed and tested between December 1, 2016, and January 18, 2017. The central portion of the courtyard was cut down to native soils and prepared for imported gravel. Filter fabric was placed over the gravel material that was placed in the courtyard and over the east and west soil edges of the south shoring. Gravel was also placed over the ramp soil fill material located at the east entry as well as in the north and south sides. A large pump truck with a conveyor belt was used to place gravel material in the southwest area between the shoring. Approximately 4 feet of gravel material was placed at the north location, which was compacted without our observations. Finish subgrade tests were taken for the south portion of the courtyard. Filter fabric was placed over the compacted courtyard area. The compacted gravel was observed in the southwest and southeast. Gravel backfill in the north was not compacted every 2 feet. Waterproofing and back drainage were placed for the remaining 4 to 5 feet of the walls. 11. The retaining walls located at the front end of the property were observed and tested on January 17 and 18, 2017. Tierra Del Oro Project Job No. 13-10316 Carlsbad, California Page 8 12. Sewer utility trench backfill was observed and tested in the street on March 6, 2020. The utility trench was backfilled on top of the soil subgrade with recycled base material followed by the asphalt concrete pavement. Grading equipment used for excavation and compaction included a 950 Cat loader, a vibratory plate, and mechanical hand tampers. Water was added, when needed, to increase the soil moisture. Field density tests yielded relative compaction of at least 90 percent (95 percent at certain test locations) of maximum dry density at the tested locations. On-site and imported soils were used during the observed grading and field density testing. The on-site soils consisted of brown silty sand and the import consisted tan-brown and dark-brown silty sand. Proper finish surface drainage for the site is to be implemented by the general contractor prior to completing construction. Field density tests and approximate limits of the graded areas are shown on the attached Plot Plan, Figure No. II. Any pending or future soil related work should be observed by our field representative prior to form and steel reinforcing placement, and just prior to concrete placement. Any pending or future utility trench, drainage trench, or wall backfill, or additional grading, should also be performed under the observation and testing of our firm. A report of additional observation and soil testing will be issued for any work performed by our firm after the date of this report. SITE SUITABILITY AND COMPLIANCE Areas that were graded under our observations and testing are, in our professional opinion, suitable for their intended use. The dense formational soils are, in our professional opinion, suitable to support the recompacted fill and new foundations. Tierra Del Oro Project Job No. 13-10316 Carlsbad, California Page 9 The soil engineering and engineering geologic aspects of the grading are in compliance with the approved geotechnical report and project plans. LIMITATIONS The findings and opinions presented herein have been made in accordance with currently accepted principles and practice in the field of geotechnical engineering in the City of Carlsbad. No warranty, either expressed or implied, is made. All statements in this grading report are applicable only for the grading operation observed by our firm. If any loose fill soils were placed without our knowledge or observation, the firm Geotechnical Exploration, Inc. shall not be held responsible for the fill soils placed without our observations and testing at any other time, or subsequent changes to the site by others, which directly or indirectly cause poor surface or subsurface drainage, water erosion, and/or alteration of the strength of the compacted fill soils. It is not within the scope of our services to provide quality control oversight for surface or subsurface drainage construction or retaining wall sealing and base of wall drain construction. It is the responsibility of the contractor to verify proper wall sealing, geofabric installation, protection board installation (if needed), drain depth below interior floor or yard surfaces; pipe percent slope to the outlet, etc. In the event that any changes in the nature, design, or location of the building or improvements are planned, the conclusions and recommendations contained in this report should not be considered valid unless the changes are reviewed and the conclusions of this report modified or verified in writing. Tierra Del Oro Project Job No. 13-10316 Carlsbad, California Page 10 This opportunity to be of service is sincerely appreciated. If you have any questions regarding this letter, please contact our office. Reference to our Job No. 13-10316 will help expedite a response to your inquiry. Respectfully submitted, GEOTECHNICAL EXPLORATION, INC. _______________________________ ______________________________ Jaime A. Cerros, P.E. Richard A. Cerros, E.I.T. R.C.E. 34422/G.E. 2007 Staff Engineer Senior Geotechnical Engineer VICINITY MAP Tierra Del Oro LLC. 5039 Tierra Del Oro Carlsbad, CA. Figure No. I Job No. 13-10316 Site Thomas Bros Guide - San Diego County pg. 1126-F2 Approximate Limitsof Observed Grading5746832133Approximate Location of Field Density Test1011121314151617189192021222423252627282930313332QafQop6-7QafQop6-7QafQop6-7QafQop6-7QafQop6-7QafQop6-7Artificial FillGEOLOGIC LEGENDOld Paralic Deposits (units 6-7)September 2017PLOT PLAN13-10316-p4.aiREFERENCE: This Plot Plan was prepared from an existing undated GRADING AND EROSION CONTROL PLAN providedby COFFEY ENGINEERING and from on-site field reconnaissance performed by GEI.LEGENDSCALE: 1” = 20’(approximate)REFERENCE: This Site Plan is not to be used for legalpurposes. Locationss and dimensions are approximate.Actual property dimensions and locations of utilitiesmay be obtained from the Approved Building Plansor the “As-Built” Grading Plans.Tierra Del Oro LLC.5039 Tierra Del OroCarlsbad, CA.Figure No. IIJob No. 13-10316(revised August 2020) TABLE A ApproximateWater DryDegree of Test Elevation Content DensityCompaction Compaction No. Date of Test Test Location (Feet) (%) (pcf) (%) Curve No. Remarks 1 7/20/16 Lower Pad FSG 12.6 108.6 95 12 7/20/16 Lower Pad FSG 6.5 110.6 97 13 7/20/16 Lower Pad FSG 8.8 109.2 95 14 7/21/16 Lower Pad- Media Room FSG 11.4 106.9 93 15 7/21/16 Lower Pad- Basement Landing FSG 9.4 108.3 95 16 10/3/16 Basement (Landing) Wall Backfill 24 10.9 104.2 91 17 10/3/16 Basement (Landing) Wall Backfill 24 9.3 102.9 90 18 10/6/16 Basement (Landing) Wall Backfill 26 FSG 6.6 107.3 94 19 10/6/16Basement (Landing) Wall Backfill Courtyard (South)23 10.9 110.1 96 110 10/6/16Basement (Landing) Wall Backfill Courtyard (South)23 11.1 111.7 98 111 10/18/16Basement (Landing) Wall Backfill Courtyard (South)24.5 7.8 103.9 91 112 10/18/16Basement (Landing) Wall Backfill Courtyard (South)24.5 6.1 105.5 92 113 11/29/16 Basement Wall Backfill (East) 29 8.5 109.9 96 114 11/30/16 Basement Wall Backfill (East) 31 4.9 109.4 96 115 11/30/16 Basement Wall Backfill (East) 31.5 4.5 110.8 97 116 11/30/16 Basement Wall Backfill Courtyard 25.5 6.9 113.4 99 117 11/30/16 Basement Wall Backfill Courtyard 25.5 7.4 112.0 98 118 12/1/16 Basement Wall Backfill Courtyard 27 5.1 111.6 97 119 12/1/16 Basement Wall Backfill Courtyard 27 4.9 108.8 95 120 12/8/16 Basement Wall Backfill Courtyard 30 5.5 119.3 94 221 12/8/16 Basement Wall Backfill Courtyard 30 6.1 121.8 96 222 1/17/17 Basement Wall Backfill (East) 33 16.6 118.8 92 323 1/17/17 Basement Wall Backfill (East) 35 15.3 120.2 94 324 1/18/17 Basement Wall Backfill (East) 35.5 14.4 122.3 95 325 1/18/17 Basement Wall Backfill (East) 37 9.4 125.2 97 326 1/18/17 Basement Wall Backfill (South) 37 10.1 123.3 96 327 1/18/17 Wall Backfill Courtyard 32.5 (FSG) 10.9 119.4 93 328 1/18/17 Wall Backfill Courtyard 32.5 (FSG) 10.3 120.4 94 3Job No. 13-1031629 1/18/17 Wall Backfill (Southwest) 32 (FSG) 10.6 120.1 93 3Figure No. IIIaSUMMARY OF FIELD DENSITY TEST RESULTS (ASTM D1556 and/or ASTM D6938)Notes: 1) Curve number refers to Table B 2) FSG denotes finish subgrade elevation 3) FBG denotes finish base grade elevation 4) FPG denotes finish pavement grade TABLE A ApproximateWater DryDegree of Test Elevation Content DensityCompaction Compaction No. Date of Test Test Location (Feet) (%) (pcf) (%) Curve No. Remarks SUMMARY OF FIELD DENSITY TEST RESULTS (ASTM D1556 and/or ASTM D6938)30 1/18/17 Wall Backfill East Entrance 37.25(FSG)10.0 121.3 94 331 3/6/20 Sewer Trench Backfill FSG 6.1 126.3 96 432 3/6/20 Sewer Trench Backfill FPG-0.33 - 140.2 96 5 Wet Density33 3/6/20 Sewer Trench Backfill FPG - 143.1 98 5 Wet DensityJob No. 13-10316Figure No. IIIbNotes: 1) Curve number refers to Table B 2) FSG denotes finish subgrade elevation 3) FBG denotes finish base grade elevation 4) FPG denotes finish pavement grade Job No. 13-10316 Figure No. IIIb TABLE B LABORATORY COMPACTION TEST RESULTS (ASTM D1557) Compaction Maximum Maximum Optimum Test Source of Dry Density Water Content Curve No. Description of Material Material (pcf) % 1 (SP/SM) SILTY to POORLY GRADED SAND; Brown On-Site 114.5 9.0 2 (SM) SILTY SAND; Tan-Brown Import 127.0 10.0 3 (SM) SILTY SAND; Dark Brown Import 128.5 10.0 4 (SM) SILTY SAND; Dark Reddish-Brown On-Site 131.3 8.2 5 (AC) Asphalt Concrete Import 146.0 *  *Hveem provided by manufacturer.