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HomeMy WebLinkAboutSDP 2019-0014; CARLSBAD OAKS NORTH LOT 2; ADDENDUM TO FINAL REPORT OF TESTING AND OBSERVATION SERVICES DURING SITE GRADING; 2007-12-26ADDENDUM TO FINAL REPORT OF TESTING AND OBSERVATION SERVICES DURING SITE GRADING CARLSBAD OAKS NORTH BUSINESS PARK –PHASE 1 LOTS 2 AND 6 CARLSBAD, CALIFORNIA PREPARED FOR TECHBILT CONSTRUCTION COMPANY SAN DIEGO, CALIFORNIA DECEMBER 26, 2007 PROJECT NO. 06442-32-04A Project No.06442-32-04A December 26, 2007 Techbilt Construction Company 3575 Kenyon Street San Diego, California 92110 Attention:Mr. Raul Guzman Subject:CARLSBAD OAKS NORTH BUSINESS PARK –PHASE 1 LOTS 2 AND 6 CARLSBAD, CALIFORNIA ADDENDUMTOFINALREPORT OFTESTINGAND OBSERVATIONSERVICES DURINGSITEGRADING Reference:1.Final Report of Testing and Observation Services During Site Grading,Carlsbad Oaks North Business Park –Phase 1, Lots 1 through 9, Carlsbad, California, prepared by Geocon Incorporated, dated August 30, 2006 (Project No.06442- 32-04A). 2.Grading and Erosion Control Plans for: Carlsbad Oaks North, Phase 1, Drawing No. 415-9A, C.T. 97-13, prepared by O’Day Consultants, with City of Carlsbad signature dated October 26, 2004. Dear Mr. Guzman: We have prepared this addendum to the referenced geotechnical report (Reference No. 1).We have provided testing and observation services for minor grading operations performed on the subject lots subsequent to issuance of the geotechnical report.The additional grading was performed between July 2006 and February 2007.The scope of our services included the following: Observing the grading operation. Performing in-place density and moisture content tests in fill placed and compacted on the subject lots. Performing laboratory tests to aid in evaluating the maximum dry density, optimum moisture content of the compacted fill. Additionally, laboratory tests were performed on samples of soil present at finish grade to evaluate the expansion characteristics and water-soluble sulfate content. Revising the As-Graded Geologic Map (specifically Figures 1 and 3) presented in our report dated August 30, 2006 to reflect as-graded conditions. Preparing this addendum report of grading. GRADING As discussed in our report dated August 30. 2006. previous grading on the subject lots consisted of removing surficial deposits to expose dense Santiago Formation. Point Loma Formation, and Granitic Rock. Fills were then placed and compacted vvithin the lots. Selective overexcavation (undercutting) of formation material exposed at pad sheet-grade vvas performed on the lots. Grading resulted \vith slope areas and the outer approximately 15 feet of the pad portion of the lots constructed to design grades presented on the project grading plans (Reference No.2). In general, the central portion of the pads was initially graded to approximately 4 feet to 12 feet below design sheet-grade upon completion of Phase 1 mass grading. Recent grading consisted of placing and compacting fill generated from other areas of the business park in the central portion of Lots 2 and 6. Fills were placed in lifts no thicker than would allow for adequate bonding and compaction. The soil was moisture conditioned, as necessary. and mixed during placement. Fills generally consisted of silty to clayey sand to silty sand. During the grading operation, we observed compaction procedures and performed in-place density testing to evaluate the relative compaction of the fill material. We performed the in-place density testing in general conformance with ASTM Test Method D 2922-05 (nuclear). Results of the in-place dry density and moisture content tests pertinent to recent grading (Test Nos. 599 to 623) are summarized in Table 1. Test Nos. 1 through 598 are presented in our report dated August 30, 2006. In general, the in-place density test results indicate the fill has a relative compaction of at least 90 percent and an appropriate moisture content at the locations tested. We have revised Figures 1 and 3 (see map pocket) of Reference No.1 to include the approximate locations of recent in-place density testing performed on the lots. We performed laboratory testing on samples of material used for fill to evaluate moisture-density relationships. optimum moisture content and maximum dry density (ASTM D 1557-02). For Lot 2 which was graded to design pad sheet-grade, we performed laboratory testing on samples collected at finish grade to determine their expansion potential (ASTM D 4829-04) and water-soluble sulfate content (California Test No. 417). Results of the laboratory tests are summarized on Tables II through IV. Finish Grade Soil Conditions Observations and laboratory test results indicate that prevailing soils randomly sampled at finish grade of Lot 2 have an Expansion Index (El) ranging from 38 to 102 and are classified as having a 1m',' to high expansion potential as defined by the California Building Code (CBC) Table 18-I-B. Table III presents the results of the expansion index testing. PrOject No. 06442-42-04A 2 December 26. 2007 The upper portion of fill placed on the pad of Lot 6 consist of silty, fine to coarse grained sands derived from excavations into granitic rock. Based on our experience with the surrounding area and laboratory testing performed throughout the business park. the materials at finish pad grade are considered to posses a verI' lml' to low expansion potential. Samples obtained from Lot 2 for expansion testing were also subjected to \vater-soluble sulfate testing to assess \vhether the soil contains high enough sulfate concentrations that could damage normal Portland cement concrete. The results of the tests indicate a moderate to severe sulfate ratina '=' based on Table 19-A-4 of the CBC. Guidelines presented in the CBC should be followed in determining the type of concrete to be used. The presence of water-soluble sulfates is not a visually discernible characteristic; therefore, other soil samples from the site could yield different concentrations. Additionally, over time landscaping activities (e.g., addition of fertilizers and other soil nutrients) may affect the concentration. Table IV presents the results of the water-soluble sulfate tests. Geocon Incorporated does not practice m the field of corrOSIon engmeenng. Therefore. it is recommended that further evaluation by a corrosion engineer be performed if improvements are planned that are susceptible to corrosion. Design sheet-grade pad elevations shown on the project grading plans were attained on Lot 2. The pad of Lot 6 was generally graded to approximately 1- to 3-feet below design pad grade and it is understood that this will be the final grade. In general and with respect to design pad grades shown on the project grading plans, the upper 10 feet of the pads were limited to soil fill with rock fragments less than 12 inches in maximum dimension and 6 inches in the upper 3 feet. Rock material greater than 12 inches was placed deeper than 10 feet below proposed finish grade. Where an undercut was performed on the pad portion of the lots, the undercut was extended at least 5 feet below design sheet grade and replaced with properly compacted fill. The areas that have been undercut are annotated as Que on the As-Graded Geologic Map. SOIL AND GEOLOGIC CONDITIONS Previous and recent grading on Lots 2 and 6 has resulted in compacted fill (Qcf and Que) overlying the Santiago Formation (Tsa), Point Loma Formation (Kp). and Granitic Rock (Kgr). Formation is exposed at grade on cut slopes and portions of the pads. The As-Graded Geologic Map (Figures 1 and 3) depicts the general geologic conditions observed during grading operations. Geologic contacts should be considered approximate. :-;0 geologic conditions were observed during grading that would preclude the continued development of the lots. Prll.JêCl :\0. CONCLUSIONS 1.0 General 1. I Based on observations and test results. it is the opinion of Geocon Incorporated that the grading, which is the subject of this repolt, has been performed in substantial conformance with the recommendations of the referenced geotechnical report. Soil and geologic conditions encountered during grading that differ from those anticipated by the geotechnical report are not uncommon. Where such conditions required a significant modification to the recommendations of the geotechnical report, they have been described herein. Finish grade elevations on Lot 6 are approximately I to 3 feet below sheet-grade design elevations. 1.2 No soil or geologic conditions were observed during grading that would preclude the continued development of the Lots 2 and 6 as planned. Based upon laboratory test results and field observations, it is our opinion that the fill soils within the subject lots have generally been compacted to at least 90 percent relative compaction at the locations tested. 1.3 Fine grading and construction of utilities/foundations may encounter non-rippable formational material and/or generate some concretionary fragments and/or rock material 12 inches or greater in size. Deeper excavations within the fill (10 feet or greater) for improvements such as utility lines, loading docks, etc., may also encounter oversize material (12 inches or greater). The potential for these conditions should be taken into consideration when determining the type of equipment to utilize for future excavation operations. The oversize material may require special handling techniques and exportation. 1.4 It is not uncommon for groundwater or seepage conditions to develop where none previously existed, particularly after landscape irrigation is initiated. The occunence of induced groundwater seepage from landscaping can be greatly reduced by implementing and monitoring a landscape program that limits inigation to that sufficient to sUPPOtt the vegetative cover without overwatering. Shallow subdrains may be required in the future if seeps occur after rainy periods or after landscaping is installed. 1.5 References to the thickness and extent of rock hold-down areas within the building pads are approximate and \vere based upon the finish-grade elevations of the approved referenced grading plans. 1.6 Geotechnical recommendations presented in Reference No. I remall1 applicable for the continued development of Lots 2 and 6. Prcljecl 1\0. 1.7 An update geotechnical report presenting fine grading recommendations and geotechnical design criteria for the ultimate development of the individual lots should be prepared by Geocon Incorporated once fine grading plans have been prepared. LIMITATIONS The conclusions and recommendations contained herein apply only to our work with respect to grading and represent conditions at the date of our final observation of grading operations on February 20, 2007. Any subsequent grading should be done in conjunction with our observation and testing services. As used herein, the term observation implies only that we observed the progress of the work with which we agreed to be involved. Our services did not include the evaluation or identification of the potential presence of hazardous materials. Our conclusions and opinions as to whether the work essentially complies with the job specifications are based on our observations, experience and test results. Due to the inaccuracies inherent in most field and laboratory soil tests, and the necessary assumption that the relatively small soil sample tested is representative of a significantly larger volume of soil, future tests of the same soil location or condition should not be expected to duplicate specific individual test results of this report. Subsurface conditions, and the accuracy of tests used to measure such conditions, can vary greatly at any time. We make no warranty, express or implied, except that our services were pelfonned in accordance with engineering principles generally accepted at this time and location. We will accept no responsibility for any subsequent changes made to the site by others, by the uncontrolled action of water, or by the failure of others to properly repair damages caused by the uncontrolled action of water. It is the responsibility of Techbilt Construction Company to ensure that the information and recommendations contained herein are brought to the attention of the architect and engineer for the project, are incorporated into the plans, and that the necessary steps are taken to see that the contractor and subcontractors carry out such recommendations in the field. Recommendations that pel1ain to the future maintenance and care for the property should be brought to the attention of future owners of the property or portions thereof. The findings and recommendations of this report may be invalidated wholly or partially by changes outside our control. Therefore, this repol1 is subject to review and should not be relied upon after a period of three years. ProjCcl :\0. If there arc any questions regarding this report or if \ve may be of further service, please contact the undersigned at your convenience. Very truly yours. GEOCONINCORPORATED Emilio Alvarado RCE 66915 EA:DBE:dmc (6) (3/dd) Addressee Techbilt Construction Incorporated Carlsbad Oaks NOlth Business Park, Job Site Attention: Mr. Fran Richmond Project No. 06442-42-04A - 6 - December 26. 2007 TABLE I SUMMARY OF FIELD DENSITY TEST RESULTS Eln. Plus Fìeld Field Field Reg'd. or 3/4" Dr~ Moist. Rei Rei Depth Curve Rock Dens. Can!. Camp. Camp. Test No, Dale Location 1ft) No, t";; ) (pef) (%) Ilk) ('k) 599 07131/06 Lot 2 251 7 0 107,6 13.5 91 90 600 07/31/06 Lot 2 253 7 0 110.2 14.4 93 90 601 08/01106 Lot 2 253 33 0 101.7 17.3 9] 90 602 08/02/06 Lot 2 257 33 0 ]04,0 18.2 93 90 603 08/02/06 Lot 2 256 33 0 101.2 17,] 90 90 ~ ~ - - -- - - - - - - - - - - - - - - ~ - - - - - - - - - - - - - - - - - - - - - - -- ~ - - - - - - ~ - - - - - - ~ - - - - - - - - - ----------- .. - ~ - - - - - - - - -- ------ 604 08/02/06 Lot 2 257 33 0 102.0 17.7 9] 90 605 08/04/06 Lot 2 258 33 0 103.2 18, I 92 90 606 08/04/06 Lot 2 258 33 0 100,9 17,4 90 90 607 08/08/06 Lot 2 256 7 0 110.3 15.6 93 90 608 08/08/06 Lot 2 255 7 0 107,2 13,3 90 90 ---------- -----._-- ------" 609 08/08/06 Lot 2 259 "7 0 ]08.4 ]4,1 91 90 I 610 08/09/06 Lot 2 257 7 0 106.8 15,3 90 90 611 08/10/06 Lot 2 254 32 0 117,7 8,2 88 90 611 A 08/10/06 Lot 2 254 32 0 119,6 9,3 89 90 611 B 08/10/06 Lot 2 254 ~') 0 121.9 81 91 90 -'- 612 08/10/06 Lot 2 256 32 0 121.3 7,6 91 90 613 08/1 1/06 Lot 2 258 7 0 110.6 10.2 93 90 614 08/1 1/06 Lot 2 258 7 0 106.9 12.6 90 90 615 08/1 1/06 Lot 2 258 7 0 111.0 9.9 93 90 615 A 08/1 1/06 Lot 2 258 7 0 108,3 14,1 91 90 616 08/17/06 Lot 2 260 32 0 121.3 10,9 91 90 617 08/17/06 Lot 2 260 33 0 105,8 14.3 94 90 618 08/24/06 Lot 6 360 34 0 125,1 8.3 90 90 619 08/24/06 Lot 6 361 34 0 125.4 7.7 90 90 620 08/24/06 Lot 2 259 9 0 102.8 17.5 91 90 621 08/25/06 Lot 6 359 34 0 125.1 8.0 90 90 622 08/28/06 Lot 2 258 9 0 103,5 18.1 92 90 623 08/28/06 Lot 2 258 34 0 125,6 8.0 90 90 624 09/20/06 Lot 6 358 I 0 1\3.9 6.1 88 90 624 A 10/10/06 Lot 6 358 I 0 117,2 9,2 91 90 ------ 625 10/26/06 Lot 2 262 18 0 104,0 15.0 90 90 626 10/26/06 Lot 2 262 18 0 ]04.3 14.7 90 90 FG 627 12/06/06 Lot 2 265 18 0 112.6 14.7 97 90 FG 628 12/06/06 Lot 2 265 ~~ 0 105,0 15.9 94 90 " FG 629 12106/06 Lot 2 262 33 0 104,0 16,5 93 90 FG 630 12/06/06 Lot 2 263 18 0 109,3 12,5 95 90 FG 631 12/06/06 Lot 2 265 15 0 108.3 18.1 97 90 FG 632 12/06/06 Lot 2 267 I" 0 1073 16,6 96 90 FG 6~~ 02/20/07 Lot 6 358 3 0 1192 7,5 93 90 .) ~") FG 634 02/20/07 Lot6 362 3 0 116,2 ,"'7 91 90 FG 635 02/20/07 Lot 6 359 3 0 116.9 7.9 91 90 ,\0, 06442-32-04A December 26. 2007 TABLE I EXPLANATION OF CODED TERMS - TEST SUFFIX A, R C . . . : Retest of previous density test failure, following moisture conditioning and/or recompaction. - STlUKI: OCT Fill in area of density test failure V.ias removed and replaced with properly compacted fill soil. - PREFIX CODE DESIGNATION FOR TEST NUMBERS DTN - DUPLICATE TEST NUMBER ST - SLOPE TEST CCRVENO. FG FINISH GRADE Corresponds to curve numbers listed in the summary of laboratory maximum dry density and optimum moisture content test results table for selected fill soil samples encountered during testing and observation. - ROCK CORRECTION For density tests with rock percentage greater than zero, laboratory maximum dry density and optimum moisture content were adjusted for rock content. For tests with rock content equal to zero, laboratory maximum dry density and optimum moisture content values are unadjusted. - TYPE OF TEST SC: Sand Cone Test (ASTM D1556) NU: Nuclear Density Test (ASTM D2922) 01': Other - ELEVATION/DEPTH Test elevations/depths have been rounded to the nearest whole foot. Project '\0. 06442-32-04A December2ó. 2007 TABLE II SUMMARY OF LABORATORY MAXIMUM DRY DENSITY AND OPTIMUM MOISTURE CONTENT TEST RESULTS ASTM D 1557-02 Proctor :Maximum Optimum Curve No. Source and Description Dry Density :Moisture Content (pet) (%) 1 Dark brown, Silty, fine SAND 129.2 8.5 " Very dark brown, Clayey, fine to coarse 128.0 8.9 .J SAND with trace gravel 7 Light olive to yellowish brown, Clayey, 118.8 13.2 fine to medium SAND with trace silt 9 Light olive, fine to medium, Sandy SILT l12.9 n.3 with little clay 15 Olive green, Silty CLAY 112.2 n.8 18 Light brown, fine, Sandy SILT 115.5 15.0 32 Dark yellowish brown, Silty, fine to coarse 134.0 7.3 SAND with trace gravel and clay 33 Olive green, Sandy SILT with trace clay 112.1 16.9 34 Dark olive brown, Clayey, fine to coarse 138.9 7.5 SAND TABLE III SUMMARY OF LABORATORY EXPANSION INDEX TEST RESULTS ASTM D 4829-03 Sample No. Moisture Content (%) Dry Density Expansion (Lot No.2 and location After Test (per) Index on Pad) Before Test EI-38A (East Portion) 10.4 22.6 106.7 57 EI-38B (South Central) 11.1 24.2 103.0 66 EI-38C (Central POltion) 11.8 24.6 103.4 59 EI-38D (West Central) 11.8 23.0 103.5 38 EI-38E 15.8 34.7 91.4 102 (South\vest Portion) EI-38F l3.7 29.2 96.0 56 (Southwest POltiol1) I ProJèc[ "n. 06442-42-041\ TABLE IV SUMMARY OF LABORATORY WATER-SOLUBLE SULFATE TEST RESULTS CALIFORNIA TEST NO. 417 Sample No. (Lot No. 2)* Water-Soluble Sulfate (%) Sulfate Exposure EI-38A 0.216 Severe EI-38B 0.443 Severe EI-38C 0.222 Severe EI-38D 0.394 Severe EI-38E 0.155 Moderate EI-38F 0.863 Severe "'See Table IV for location on pad. PrUjèct :\0.