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Home My WebLink AboutCT 04-08; LA COSTA VALLEY TOWNHOMES; TESTING & OBSERVATION DURING BORROW SITE GRADING; 2013-06-26GEOCON INCORPORATED GEOTECHNICAL • ENVIRONMENTAL. MATERIALS(7) Project No. 07193-32-03A- June 26, 2013 City Ventures 1900 Quail Street Newport Beach, California 92660 Attention: Mr. Matthew Jansen Subject: FINAL REPORT OF TESTING AND OBSERVATION SERVICES DURING BORROW SITE GRADING LA COSTA VILLAGE TOWNHOMES (CARLSBAD 3), CT 04-08 BUILDING PADS 7 AND 8 CARLSBAD, CALIFORNIA Dear Mr. Jansen: In accordance with your request, we have provided testing and observation services during regrading of Building Pads 7 and 8 and Brass Buttons Street after being used as a borrow site/balance area. Our observation and test results perfonned during site grading for the overall development were provided in our document entitled Final Report of Testing and Observation Services during Site Grading, La Costa Village Townho,nes (Carlsbad 3), CT 04-08, Building Pads 1 through .6 and 9 through 13, Carlsbad, California, dated May 31, 2012. The scope of our services during borrow site regrading included the following: Observing the regrading operation including the placement of fill.. Performing in-place density and moisture content tests in fill placed and compacted on the site. Performing laboratory tests to aid in evaluating the compaction, expansion characteristics, and water soluble sulfate content of the soil material used as fill. Preparing an As-Graded Geologic Map. Preparing this final report of grading. GRADING Site grading consisted of removal of existing surficial deposits to expose formationaf materials. During site development, Building Pads 7 and 8 and Brass Buttons Street Were left in an interim 6960 Flanders Drive 0 San Diego, California 92121-2974 M Telephone 858.558.6900 0 Fax 858.558.6159 condition in order to receive footing and trench spoils from other areas within the project limits. The approximate limits of the borrow-site excavation are shown on the As-Graded Geologic Map, Figure 1. Excavations consisted of maximum cuts and fills of approximately 16 feet and 18 feet, respectively. The grading was performed in conjunction with testing and observation services provided by Geocon Incorporated. Fill Materials and Placement Procedures The on-site fill materials generally consisted of silty to clayey sands. The 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. Field In-Place Density and Laboratory Testing During the grading operation, compaction procedures were observed and in-place density tests were performed to evaluate the relative compaction of the fill material. The in-place density tests were performed in general conformance with ASTM D 6938-10 (nuclear). Results of the field density tests and moisture content tests performed during grading are summarized on Table I and are presented on the As-Graded Geologic Map (Figure 1). In general, the in-place density test results indicate that the fill at the locations tested has a relative compaction of at least 90 percent and near or slightly above optimum moisture content. Laboratory tests were performed on samples of material used for fill to evaluate moisture-density relationships, optimum moisture content and maximum dry density, expansion characteristics and water-soluble sulfate content. The results of the laboratory tests are summarized on Tables H through IV. Finish-Grade Soil Conditions Laboratory tests were performed on samples exposed at finish, grade to determine the expansion potential (ASTM D 4829-08A) and the water-soluble sulfate content (California Test No. 417). The results of the laboratory tests are summarized on Tables III and IV. The laboratory tests performed on soil samples to measure the percentage of water-soluble sulfate content indicate that the on-site materials possess "negligible" sulfate exposure to concrete structures, as defined by the 2010 California Building Code (CBC). The soluble-sulfate test results for each lot are presented on Table V. The CBC provides no specific recommendations for concrete subjected to "negligible" sulfate exposure. . Project No. 07193-32-03A -2- June 26, 2013 Geocon incorporated does not practice in the field of corrosion engineering. Therefore, if improvements that could be susceptible to corrosion are planned, it is recommended that further evaluation by a corrosion engineer be performed. SOIL AND GEOLOGIC CONDITIONS The soil and geologic conditions encountered during grading were found to be generally similar to those described in the referenced project geotechnical report. The conditions observed are presented on the As-Graded Geologic Map, Figure 1. CONCLUSIONS AND RECOMMENDATIONS Based on observations and test results, it is the opinion of Geocon Incorporated that the grading, to which this report pertains, has been performed in substantial conformance with the recommendations of the referenced project soil report. Soil and geologic conditions encountered during grading that differ from those anticipated by the project soil report are not uncommon. Where such conditions required a significant modification to the recommendations of the project soil report, they have been described herein. No soil or geologic conditions were observed during grading that would preclude the continued development of the property as planned. Based upon laboratory test results and field observations, it is our opinion that the fill soils have generally been compacted to at least 90 percent relative compaction at the locations tested. Based on our observations and test results performed during the grading operation, it is our opinion that "the site is adequate for its intended use." - LIMITATIONS The conclusions and recommendations contained herein apply only to our work with respect to regrading of Building Pads 7 and 8 and Brass Button Street and represent conditions at the date of our final observation on June 14, 2013. Changes in the conditions of a property can occur with the passage of time due to natural processes or the works of man on this or adjacent properties. In addition, changes in applicable or appropriate standards may occur, resulting from legislation or the broadening of knowledge in the fields of geotechnical engineering or geology. Accordingly, the findings of this report may be invalidated wholly or partially by changes outside of our control. Therefore, this report is subject to review and should not be relied upon after a period of three years. 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 Project No. 07193-32-03A . - 3 - June 26, 2013 potential presence of hazardous or corrosive 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 performed 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 City Ventures to ensure that the information and recommendations contained herein are brought to the attention of the architect and engineer for the project, and 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 pertain to the future maintenance and care for the property should be brought to the attention of future owners of the property or portions thereof. Should you have any questions regarding this report, or if we may be of further service, please contact the undersigned at your convenience. Very truly yours, GEOCON INCORPORATED Trevor E. Myers 0No. RCE63773W RCE 63773 rn TEM:DBE:dmc Vt OF (2) Addressee (email) City Ventures -Job Site Trailer Attention: Mr. Jordan Gardner David Evan CEG 1860 4oNAL DADB c iL No 18 CERTIFIED —• * ENGINEERING * GEOLOGIST kv Project No. 07193-32-03A -4- June 26. 2013 I I CARLSBAD 3 CARLSBAD, CALIFORNIA SCALE: 1' = 20' GEOCON LEGEND I\\\\\\\\\\ \ \\\ \ç 00 00 \ \ \ \\Ta- Qcf COMPACTED FILL Tsa........SANTIAGO FORMATION (Dotted Where Buried) 199 106APPROX. LOCATION OF IN-PLACE DENSITY TEST \- FG .... Finish Grade ST .... Slope Test \ \ \ \ \ \ 206 \ \ \ 201......... APPROX. ELEVATION (FT) AT BASE OF FILL ........APPROX. LIMITS OF BORROW SITE 00 \\\ \ \ \ GE-OCON cO1'oRArEi) GEOTECHNICAL . ENVIRONMENTAL a MATERIALS 6960 FLANDERS DRIVE- SAN DIEGO, CALIFORNIA 92121- 2974 PHONE 858 558-6900 . FAX 858 558-6159 PROJECT NO. 07193 -32 -03A FIGURE I AS-GRADED GEOLOGIC MAP DATE 06-26 -2013 YPROJECTS\07183-32-03A MOONSTONE'SHEET31,07193-32-03A AS-GRO MAP 01 dwg TABLE I SUMMARY OF FIELD DENSITY TEST RESULTS Elev. Plus Field Field Field Reqd. or 3/4" Dry Moist. Rel. Rel. Depth Curve Rock Dens. Cont. Comp. Comp. Test No. Date Location (ft) No. (°"°) (pcO (%) (%) (%) 97 10/16/12 Brass Buttons/Lot 7 203 8 0 106.4 13.8 91 90 98 10/18/12 Lot . 204 . 8 0 106.5 14.5 91 90 99 12/12/12 Lot 206 8 0 106.9 13.7 92 90 100 12/12/12 Lot 207 8 0 105.l 14.1 90 90 101 02/27/13 Lot 210 8 0 106.3 13.9 91 90 102 02/27/13 Lot 210 8 0 107.2 14.1 92 90 FG 103 06/14/13 Lot 213 . 8 0 106.6 13.8 91 90 FG 104 06/14/13 Lot 213 8 0 108.0 14.2 93 90 FG 105 06/14/13 Lot 214 8 0 107.7 14.1 92 90 FG 106 06/14/13 Lot 214 8 0 107.4 14.3 92 90 Project No. 07193-32-03A June 26, 2013 TABLE I EXPLANATION OF CODED TERMS - TEST SUFFIX A, B, C, . . . : Retest of previous density test failure, following moisture conditioning and/or recompaction. - STRIKE-OUT Fill in area of density test failure was removed and replaced with properly compacted fill soil. - PREFIX CODE DESIGNATION FOR TEST NUMBERS FG - FINISH GRADE ST - SLOPE TEST SZ - SLOPE ZONE VW - \TERDURA WALL WB - WALL BACKFILL - CURVE NO. C 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 D 1556) NU: Nuclear Density Test (ASTM D6938 and D 2950) OT: Other - ELEVATION/DEPTH Test elevations/depths have been rounded to the nearest whole foot. Project No. 07193-32-03A June 26. 2013 TABLE II SUMMARY OF LABORATORY MAXIMUM DRY DENSITY AND OPTIMUM MOISTURE CONTENT TEST RESULTS ASTM D 1557-09 I Proctor I I Source and Description Maximum Dry Optimum Moisture Curve No. . Density (pet) I Content (%) 8 Yellowish-Browi, Silty, fine to medium SAND; with I I I trace clay 116.7 13.9 TABLE III SUMMARY OF LABORATORY EXPANSION INDEX TEST RESULTS ASTM D 4829-08A Sample No. Moisture Content (°') Dry Density I (pcf) Expansion I Index I Before Test I After Test EI-12 I 17.5 112.5. Low TABLE IV SUMMARY OF LABORATORY WATER-SOLUBLE SULFATE TEST RESULTS CALIFORNIA TEST NO. 417 Sample No. . Water-Soluble Sulfate (%) Sulfate Exposure EI-12 0.057 Negligible TABLE V SUMMARY OF FINISH GRADE EXPANSION INDEX AND SULFATE EXPOSURE TEST RESULTS, AND RECOMMENDED FOUNDATION CATEGORY BUILDING PADS 7 AND 8 Building Sample at Expansion CBC Recommended Sulfate Pad Number Finish Grade Index Expansion Foundation Exposure Classification Category 7 and 8 EI-12 26 Low I Negligible Project No. 07193-32-03A . June 26, 2013