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Mr. Mike Desso - 2 - 29 August 2007 <br /> Comments <br /> 1. The Work Plan proposes two soil borings (SG-16 and SG-17) adjacent to the west side of <br /> Stockton Avenue, near 320 Stockton Avenue. ECM will collect soil gas samples at 5- and <br /> 10-foot depths in each boring, and deeper if volatile organic compounds (VOCs) are <br /> detected in the 10-foot sample with a hand-held photo ionization detector. In addition, <br /> Regional Water Board staff has determined that the northern-most soil boring (SG-16) <br /> must be advanced to the water table and soil vapor samples collected within the <br /> unsaturated zone at 5-foot intervals for laboratory chemical analyses of VOCs. <br /> 2. All soil gas samples should be collected with summa canisters. If TedlarTm bags are used, <br /> sample analyses must be performed immediately after collection by a California-certified <br /> onsite laboratory. <br /> 3. The Work Plan indicates that soil gas samples collected from 5 feet below the ground <br /> surface in soil borings will be collected no sooner than 48 hours following hole clearance by <br /> hand-auguring. This equilibration time is acceptable provided the boring has been cleared, <br /> the probe placed, and the boring backfilled for 48 hours. <br /> 4. During each field event, weather observations must be recorded throughout the period of <br /> time that field personnel are in Ripon. <br /> 5. The Work Plan does not provide sufficient rational to conclude that soil gas sampling is not <br /> necessary in the parking lot west of the Former Facility or near soil boring SG-8. Soil gas <br /> samples must be collected during the next four consecutive quarters at a depth of five feet <br /> from the parking lot west of the Former Facility between soil boring SG-7 and the source of <br /> VOCs at the Former Facility. Also, Nestle should consider collection of samples near the <br /> location of soil boring SG-8. Installation of soil gas monitor well(s), rather than <br /> advancement of soil boring(s) each quarter, is preferred. <br /> 6. Following completion of the field work, Nestle must revise the 8 January 2007 Soil Gas <br /> Investigation Report to include the supplemental data. Regional Water Board staff will <br /> evaluate that report and make a determination at that time as to the need for additional <br /> quarters of soil vapor sampling. <br /> Nestle must begin the field work within 45 days of the date of this letter and submit the revised <br /> report described in Item 6 above within 60 days of completion of four quarters of soil gas <br /> sampling. Please contact me at (916) 464-4675, or by email at jbrownell@waterboards.ca.gov <br /> if you have anyQquestions. <br /> 1 � <br /> James R. Brownell, P.G. <br /> Associate Engineering Geologist <br /> Distribution: List, page 3 <br />