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CLEARWATER � Q <br /> c R a U n, z N c. <br /> configuration, regardless of how large the applied vacuum. Clearwater <br /> recommends the following approach to better define existing hydrocarbon <br /> concentrations in this area, and provide for effective remedial action in this area if it <br /> is determined to be required: <br /> Drilla single soil boring within five feet of existing VW-3. Continuously core <br /> the boring from 11 feet to 17 feet bgs, and send a sample from each one-foot <br /> interval to the project lab for analysis of gasoline compounds. Construct a 2-inch <br /> diameter soil vapor extraction well within this boring, screened from completed <br /> depth to 13 feet bgs in an effort to provide a mechanism for vapor extraction, <br /> should soil sample analysis indicate the presence of same. If the results of lab . <br /> analysis indicate that concentrations of residual hydrocarbons are negligible or <br /> non-existent, the well would not be incorporated into the existing system, and- <br /> the samples would be considered "confirmation samples". 'If concentrations are <br /> significant, plumbing currently connected to VW-3 would be removed and .re- <br /> attached to the new extraction well, enabling a more focused remedial <br /> application in this area. <br /> The removal of VW-1 and 2 from the existing system, and the replacement of VW-3 <br /> as described (if required), would eliminate approximately 85 feet of unnecessary <br /> vapor extraction well screen. The system currently is plumbed to extract from 130 <br /> feet of screen. <br /> Clearwater hopes that this information is satisfactory to the PHS/EHD, and looks <br /> forward to moving with you towards project closure. <br /> Sincerely, <br /> Clearwater Group, Inc. <br /> Markus B. Niebanck, R. G. . <br /> Operations Manager <br /> CC. Mrs. Margaret Ekholm <br /> Ms. Brooke Birkie <br /> Ms. Elizabeth Thayer, RWQCB <br /> Mr. George Lockwood, USTCF <br />