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r --PARSOrts 2121 N.California Blvd.Suite 500•Walnut Creek,California 94596•(925)941-3700•Fax(925)979-9781 www.parsons.com FEB�C�F�W IE[0 1 4 2008 ENVIRONMENT HEALTH February 12, 2008 PERMIT/SERVICES Ref: 442966.71000 Gerald J. Djuth California Regional Water Quality Control Board Central Valley Region 11020 Sun Center Drive #200 Rancho Cordova, CA 95670 Subject: Installation of Sentry Wells MW-16 and MW-17 Offsite Southeast of Applied Aerospace Structures Corporation Stockton, California Dear Mr. Djuth: The purpose of this letter report is to document the successful installation and initial sampling of the two offsite sentry monitoring wells, MW-16 and MW-17. Drilling, well construction, and initial sampling have been completed as proposed in the report titled: Offsite CPT Groundwater Investigation Report, which was submitted to the RWQCB on February 22, 2007. The wells were constructed on December 3 and 4, 2007, and developed on December 10. Dedicated low-flow sampling pumps were set on January 18, 2008 with the intakes approximately at mid-screen depths. As indicated on the attached boring logs the screened intervals intersect permeable silty sand (SM) in MW-16 and sandy silt(ML) in MW-17. The installed locations of the wells are indicated on Figure 1. Coordinates and elevations were surveyed and those data will be reported in the appendix to the next semiannual report. The logs, coordinate, and analytical data for these wells are being loaded to the State of California's online GeoTracker database. The initial groundwater samples were collected from MW-16 and MW-17 on January 21. As summarized in Table 1, the analytical results for these two wells were comparable to results of the CPT groundwater investigations for borings P-106 and P-103 at the depths corresponding to the screened intervals. Chemicals detected in the two wells were at concentrations below their California MCL concentrations. Per the site monitoring and reporting program, these two wells will be incorporated into the quarterly sampling schedule.