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Home My WebLink AboutCDP 2017-0024; Highland James Subdivision (Highland Drive Portion); Update to Geotechnical Investigation and Plan Review; 2020-12-21 December 21, 2020 CTE Job No. 10-12998G Veck Investment Properties, LLC Attention: Elizabeth Temple 3276 Highland Drive Carlsbad, California 92008 Telephone: (619) 204-4903 Via Email: elizabethktemple@gmail.com CC: James A Chinn, Architect, Attn: James A Chinn, Via Email: jameschinn400@gmail.com Subject: Update to Geotechnical Investigation and Plan Review Highland James Subdivision 3970 & 3980 Highland Drive Carlsbad, California References: At end of document Ms. Temple: As requested, Construction Testing & Engineering, Inc. (CTE) provides the following plan review and update to the preliminary geotechnical investigation report in accordance with the comments in the City of Carlsbad Third-Party Geotechnical Review (First). Based on the age of the Geotechnical Investigation, this update is provided, which addresses current project plans and provides updated design criteria consistent with the 2019 California Building Code and ASCE 7-16. We understand that proposed improvements will consist of constructing two two-story residential structures, with paved driveways, retention basins, flatwork, utilities, and other associated improvements. Based on review of the project plans and referenced geotechnical documents, the data, conclusions, and recommendations presented therein are considered appropriate for project design, except as specified below. However, CTE reserves the right to further modify the recommendations based on actual conditions exposed during construction and/or foundation installation operations. As part of the update to the geotechnical report, CTE performed a recent site reconnaissance and advanced an additional boring to a depth of approximately five feet below grade to collect a representative bulk sample of subgrade material for expansion testing. Locations of the recent boring and previous explorations are presented on the revised grading plan (Figure 2). A geologic cross section is also attached as Figure 2A. Based on laboratory testing, the improvement area soils are generally anticipated to have a very low expansion potential (EI of 0). This expansion potential is consistent with the findings of the referenced geotechnical report. Therefore, recommendations provided in the report remain applicable with respect to expansion index and associated foundation design. Construction Testing & Engineering, Inc. Inspection I Testing I Geotechnical I Environmental & Construction Engineering I Civil Engineering I Surveying 1441 Montiel Road, Suite 11 5 I Escondido, CA 92026 I Ph (760) 746-4955 I Fax (760) 746-9806 I www.cte-inc.net Update to Geotechnical Investigation and Plan Review Page 2 Highland James Subdivision 3970 & 3980 Highland Drive, Carlsbad, California December 21, 2020 CTE Job No. 10-12998G \\file01\CTE Share\Projects\10-12000 to 10-12999 Projects\10-12998G\Update Report\Ltr_Update and Plan Rev.doc Grading and construction of the proposed improvements is not generally anticipated to have an impact on adjacent properties provided the recommendations included in this update and the referenced geotechnical report are incorporated into the grading and construction. Regarding recommended observation and testing during grading and construction, the following is provided: As is typical and at a minimum, a CTE geotechnical representative should observe and approve the dimensions and bottoms of excavations for overexcavation, footings, utilities, and other subsurface features. Additionally, CTE should be scheduled by others to test field relative compaction and moisture content of placed engineered fill soils, and should be allowed to collect additional geotechnical samples, as necessary and appropriate. 1.0 SEISMIC GROUND MOTION VALUES The seismic ground motion values listed in the table below were derived in accordance with the ASCE 7-16 Standard that is incorporated into the 2019 California Building Code. This was accomplished by establishing the Site Class based on average anticipated resistance for the upper 100 feet. Site coefficients and parameters were calculated using the SEAOC-OSHPD U.S. Seismic Design Maps application. Seismic ground motion values are based on the approximate site coordinates of 33.1535° latitude and -117.3293° longitude. These values are intended for the design of structures to resist the effects of earthquake ground motions. TABLE 1.0 SEISMIC GROUND MOTION VALUES (CODE-BASED) 2019 CBC AND ASCE 7-16 PARAMETER VALUE 2019 CBC/ASCE 7-16 REFERENCE Site Class D ASCE 16, Chapter 20 Mapped Spectral Response Acceleration Parameter, SS 1.045 Figure 1613.2.1 (1) Mapped Spectral Response Acceleration Parameter, S1 0.379 Figure 1613.2.1 (2) Seismic Coefficient, Fa 1.082 Table 1613.2.3 (1) Seismic Coefficient, Fv Null Table 1613.2.3 (2) MCE Spectral Response Acceleration Parameter, SMS 1.131 Section 1613.2.3 MCE Spectral Response Acceleration Parameter, SM1 Null Section 1613.2.3 Design Spectral Response Acceleration, Parameter SDS 0.754 Section 1613.2.5(1) Design Spectral Response Acceleration, Parameter SD1 Null Section 1613.2.5 (2) Peak Ground Acceleration PGAM 0.524 ASCE 16, Section 11.8.3 Update to Geotechnical Investigation and Plan Review Page 3 Highland James Subdivision 3970 & 3980 Highland Drive, Carlsbad, California December 21, 2020 CTE Job No. 10-12998G \\file01\CTE Share\Projects\10-12000 to 10-12999 Projects\10-12998G\Update Report\Ltr_Update and Plan Rev.doc It is anticipated that the project will meet the requirements provided in ASCE 11.4.8, Exception 2, which permits the use of code-based ground motion values, provided the value of the seismic response coefficient Cs is determined as needed by equation 12.8-2 for values of T < 1.5 Ts. 2.0 PLAN REVIEW As requested, CTE has reviewed the referenced plans for the subject project. The object of our review was to identify potential conflicts with the referenced plans and the project geotechnical documents, as they pertain to the proposed improvements. Based on our review, it is recommended that the following items be clarified on the plans: • On Sheet 5, Bioretention BMP (PR-1) Detail, it appears that the basin is only partially lined with the bottom open to subgrade. Based on the proximity of the basins to the property line, infiltrating water could potentially impact the adjacent downgradient properties. CTE recommends lining the entire basin. With the exception of the above noted item, the plans appear to be in general conformance with the recommendations presented in referenced Geotechnical Investigation report and update letter. 3.0 LIMITATIONS The preliminary recommendations herein are based on our review of the currently available design information, previous geotechnical investigations, and recent site observations. The anticipated conditions should be verified in the field during construction. Variations may exist and conditions not observed or described in the geotechnical reports may be encountered during construction. If conditions different from those described in the geotechnical reports are encountered, this office should be notified and additional recommendations, if required, will be provided. The recommendations presented herein have been developed in order to reduce the potential adverse effects of soil expansion and settlement. However, even with the design and construction precautions, some post-construction settlement or heave and associated distress may occur. Update to Geotechnical Investigation and Plan Review Page 4 Highland James Subdivision 3970 & 3980 Highland Drive, Carlsbad, California December 21, 2020 CTE Job No. 10-12998G \\file01\CTE Share\Projects\10-12000 to 10-12999 Projects\10-12998G\Update Report\Ltr_Update and Plan Rev.doc CTE appreciates this opportunity to be of service on this project. If you have any questions regarding this report, please do not hesitate to contact the undersigned. Respectfully submitted, CONSTRUCTION TESTING & ENGINEERING, INC. Dan T. Math, GE #2665 Aaron J. Beeby, CEG #2603 Principal Engineer Senior Engineering Geologist AJB/DTM/JFL Attachments: Figure 2 Geologic/Exploration Location Map Figure 2A Cross Section A-A’ Exploration Log, December 8, 2020 Third-Party Geotechnical Review (First), Dated November 16, 2020 REFERENCES Geotechnical Investigation Proposed 5-Unit Residential Subdivision 3980 Highland Drive Carlsbad, California CTE Job No. 10-12998G, Dated November 9, 2016 Seven Sheet Grading Plan Highland James Subdivision (Highland Drive Portion) 3970 & 3980 Highland Drive Carlsbad, CA 92008 REC Consultants, Inc., Dated October 23, 2020 B-3 B-1 Qop B-2 A A' HA-1 TP-3 B-3 Approximate Boring Location (2016) LEGEND T-3 Approximate Test Pit Location (Soil Testers 2005) HA-1 Approximate Boring Location (2020) 120ELEVATION (FEET)100DISTANCE (FEET)CROSS SECTION A-A'0501009080110150200A13014070150160170120100908011013014070150160170A'B-1B-2TD=4'TD=2'Proposed StructureProposed GradeQopTsa????Existing GradeLEGENDTERTIARY SANTIAGO FORMATION TsaAPPROXIMATE GEOLOGIC CONTACTQUATERNARY OLD PARALIC DEPOSITSQop Exploration Log, December 8, 2020 DEFINITION OF TERMS PRIMARY DIVISIONS SYM BOLS SECONDARY DIVISIONS WELL GRADED GRAVELS, GRAVEL-SAND MIXTURESLITTLE OR NO FINESPOORLY GRADED GRAVELS OR GRAVEL SAND MIXTURES, LITTLE OF NO FINESSILTY GRAVELS, GRAVEL-SAND-SILT MIXTURES,NON-PLASTIC FINESCLAYEY GRAVELS, GRAVEL-SAND-CLAY MIXTURES, PLASTIC FINESWELL GRADED SANDS, GRAVELLY SANDS, LITTLE OR NOFINES POORLY GRADED SANDS, GRAVELLY SANDS, LITTLE OR NO FINES SILTY SANDS, SAND-SILT MIXTURES, NON-PLASTIC FINES CLAYEY SANDS, SAND-CLAY MIXTURES, PLASTIC FINES INORGANIC SILTS, VERY FINE SANDS, ROCK FLOUR, SILTY OR CLAYEY FINE SANDS, SLIGHTLY PLASTIC CLAYEY SILTS INORGANIC CLAYS OF LOW TO MEDIUM PLASTICITY,GRAVELLY, SANDY, SILTS OR LEAN CLAYSORGANIC SILTS AND ORGANIC CLAYS OF LOW PLASTICITY INORGANIC SILTS, MICACEOUS OR DIATOMACEOUS FINE SANDY OR SILTY SOILS, ELASTIC SILTSINORGANIC CLAYS OF HIGH PLASTICITY, FAT CLAYS ORGANIC CLAYS OF MEDIUM TO HIGH PLASTICITY,ORGANIC SILTY CLAYS PEAT AND OTHER HIGHLY ORGANIC SOILS GRAIN SIZES GRAVEL SAND COARSE FINE COARSE MEDIUM FINE 12" 3" 3/4" 4 10 40 200 CLEAR SQUARE SIEVE OPENING U.S. STANDARD SIEVE SIZE ADDITIONAL TESTS (OTHER THAN TEST PIT AND BORING LOG COLUMN HEADINGS) MAX- Maximum Dry Density PM- Permeability PP- Pocket Penetrometer GS- Grain Size Distribution SG- Specific Gravity WA- Wash Analysis SE- Sand Equivalent HA- Hydrometer Analysis DS- Direct Shear EI- Expansion Index AL- Atterberg Limits UC- Unconfined Compression CHM- Sulfate and Chloride RV- R-Value MD- Moisture/Density Content , pH, Resistivity CN- Consolidation M- Moisture COR - Corrosivity CP- Collapse Potential SC- Swell Compression SD- Sample Disturbed HC- Hydrocollapse OI- Organic Impurities REM- Remolded FIGURE:BL1 GW SILTS AND CLAYS LIQUID LIMIT IS LESS THAN 50 SILTS AND CLAYS LIQUID LIMIT IS GREATER THAN 50 SANDS MORE THAN HALF OF COARSE FRACTION IS SMALLER THAN NO. 4 SIEVE GRAVELS MORE THAN HALF OF COARSE FRACTION IS LARGER THAN NO. 4 SIEVE CLEAN GRAVELS < 5% FINES GRAVELS WITH FINES CLEAN SANDS < 5% FINES SANDS WITH FINES COARSE GRAINED SOILS MORE THAN HALF OF MATERIAL IS LARGER THAN NO. 200 SIEVE SIZE GP GM GC SW SP SM SC ML CL OL MH CH OH PT FINE GRAINED SOILS MORE THAN HALF OF MATERIAL IS SMALLER THAN NO. 200 SIEVE SIZE HIGHLY ORGANIC SOILS SILTS AND CLAYS COBBLES COBBLES BOULDERS PROJECT:DRILLER:SHEET:of CTE JOB NO:DRILL METHOD:DRILLING DATE: LOGGED BY:SAMPLE METHOD:ELEVATION:Depth (Feet)Bulk SampleDriven TypeBlows/FootDry Density (pcf)Moisture (%)U.S.C.S. SymbolGraphic LogBORING LEGEND Laboratory Tests DESCRIPTION Block or Chunk Sample Bulk Sample Standard Penetration Test Modified Split-Barrel Drive Sampler (Cal Sampler) Thin Walled Army Corp. of Engineers Sample Groundwater Table Soil Type or Classification Change ??????? Formation Change [(Approximate boundaries queried (?)] "SM"Quotes are placed around classifications where the soilsexist in situ as bedrock FIGURE:BL2 PROJECT:SHEET:of CTE JOB NO:DRILL METHOD:DRILLING DATE: LOGGED BY:SAMPLE METHOD:ELEVATION:Depth (Feet)Bulk SampleDriven TypeBlows/6"Dry Density (pcf)Moisture (%)U.S.C.S. SymbolGraphic LogDESCRIPTION "SM" Total Depth: 5' No Groundwater Encountered HA-1 EI grained SANDSTONE, oxidized, massive, QUATERNARY OLD PARALIC DEPOSITS:Medium dense, slightly moist, reddish brown, silty fine to medium AJB BULK ~161 FEET BORING: HA-1 Laboratory Tests 5-UNIT SUBDIVISION DRILLER:AJB 1 1 10-12998G HAND AUGER 12/8/2020 0 5 10 15 20 25 Third Party Geotechnical Reivew . HETHERINGTON ENGINEERING, INC, SOIL & FOUNDATION ENGINEERING • ENGINEERING GEOLOGY• I-IYDROGEOLOGY City of Carlsbad Laiicl t>evelopment Engineering 1635 Faraday Avenue QaJ·lSb11Cl, Cal.iforllia 92008-7314 Attention: Ms, Kyre1111e Chua November 16, 2020 Project No. 9245.1 Log No. 21201 Subject: THIRD-PARTY GEOTECHNICAL.REVIEW {FIRST) Proposed 5 l)nit Residential Subdivision 3980 Highland Dl'ive Carlsbad, Caljfoq1ia Project ID: CDP 2017-0024/CDP 2011,0025 Refere1wcs: 1, "Oeotechnical Investigation, Proposed 5-Unit Residential Sr1bclivision, 3980 lliglila11cl Drive, Carlsbac!, Galifot·n ia", by Construction Testing & Engineering, Inc., dated November 9, 2016. · 2. "Grading Plans For: Highland James Subdivision, 3970 & 3980 Highlat1d Dr., Cadsbad, CA", by REC Consultants, Tnc., dated October 23, 2020 (Sheets l .through 7). Dear•Ms, Chua: Th accordance with your request, Hetherington Engineeri11g, Inc, has provided third-party geowohnical review of Reference J, The following comments are provided for analyses iuid/pr response by the Geo.technical Consultant, REVIEW OFGEOTECHNICAL REPORTS L Due to the age ofthe ''Geotechnical Inves(igation ..• ", .(Reference J), .the Consultant should pi·ovide an updated geotechnical report addressing the plans, and provide updated grading .and foundation recommendations and seismic design cl'iteria c:onslstent with the 2019 California Building Code alldASCE 7" 16. 2. 'fhe Gonsulta11t sh@lr! J"eyiew the project .gradi11g and foundation plans, provide any additional geotechnical 1'eco1rtmenc;Jations considered Mcessary, and confirm that the Plans have been pl·epm·ed in accot'dance With the geotechnlcal recommendations pl'ovided in the geotechnical reports. 3. The Cons;1ltant should provide an updated geoteclmical map/plot plan utiliiing the latest grncli11g plan fc:H' the. project to clearly show (at a minimum), a) existing site topography, b) proposed stt·uc.t.ures/improvements, c) propo.s.ed foJished g1·ades, d) 5~65 Avianltja Encinas, .Suite.A• o,.rlsbad, CA 92008-4369 • (760) 931-1911' • Fax (760) 931-0545 .333 Third Stree • Laguna Bflaoh, CA 9265 • (949) 715-.5440 • Fax (949) 715-5442 WWW:helherlngtonengineering.com . THIRD-PARTY OEOTECHNICAL .REVIEW (FIRST) Project No. 9245.1 Log No. 21201 November 16, 2020 Page2 locatlons of the subsw·foce exploration, c).geo]ogic contacts, and l) i-e111edial grading Jifnils, .\ltC, 4. · The. Cons\1ltant should prnvide geologic cross 0 sections .utilizing the current grading plan to clearly show (at a minimum), u) ~xlsting site topog1'aphy, ti) propqsed 5ti•ucttU·t:,.~/i111p1·oveme1lts, c) Jiro11osed finished grades, d) geologic contacts, e) geologic structure, f) . locations of .the subsurface exploration, g) temporary cottstrui,tio11slppes, and h)wmedial.grading, .etc. 5, The Qonsultant should proyide a state111ent regarding the. impact of the proposed · grading and construction o.n ,1djacentpr<Jperties iit1tl il11pt·qve111e1us. 6. Fcu1ndationan(I sl&b .design 9ritet'ia for soils shpuld be co11s.istent with Section l 808.6 of.th~ 2019 California Bl!ilding Code. The Consultai1t should provide expansion index test resillts an.d update foundation reco11111wndations, as necessary. 7. Tite,Consultanl sfi<mld prov id,;, a list Ofl'eco1nn1\indecl o.bservatiQ1.1 and testing \lul'ing sitegtadltig and cofis!l"l1ctloi1. The ◊Pp◊rtLtfiity to be. of ,service• is sincerely appreciated. If you have any questions regardingthls,r,:.yiew, please contaet th.is office .at your conve!1ience. Sincerely, HETHERINGTON ENGINf;ERlNG, INC. M. rlc /Htitlii~itl,o Giyil Engineer 304 Geqtechnical Engin (expires 3/31/22) ~,,.£~ ~\;\ttWt/4-" aul A, B<JgSeth ~ . · •~ ii: PAULA, ·~ mfessional Geologist 377'2 !!=i POGSETH . er!ifiedEngineel'ing Geologistll53 u Nfi,tE,G,1163 · ertified Iclydl-ogeoJogist591 · *. Expi ___ * xpires3/3l/22) · ~~ · 'iit-.. ~e·o,: CAl\~a . Disfribution: I ,vi& e-mail (kyter\lie,Chqa@earlsbadca.gov) I ,via e0mail (Ilriget.Boka@eadsbadea:gov) HETHERINGTON ENGUNEERUNG, IN.IC.