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if necessary These well locations were selected to define the magnitude of soil contamination <br /> in the suspected source area Each of the vadose wells are constructed of 2-inch diameter PVC <br /> and extend to a maximum depth of 48 feet below grade The wells are screened with 0 02 inch <br /> slotted casing from total depth to 5 to 10 feet below grade The annular space of the wells are <br /> filled with #3 Monterey sand along the screened interval, sealed with bentonite above the sand, <br /> and grouted with cement to the surface <br /> Groundwater monitoring wells MW7 and MW8 are located in the southeast and southwest <br /> corners of the site, respectively These wells are two of four wells proposed in Thnfty's <br /> Revised Work Plan The remaining two wells are planned for off-site installation on Rivara <br /> Road and Pacific Avenue (see Work Plan for details) The two wells extend to 56 and 58 feet <br /> below grade, respectively Each well is two inches in diameter and is screened with 0 02 inch <br /> slotted casing The well annuli are filled with #3 Monterey sand along the screening, and sealed <br /> with bentonite and grout to the surface Each of the wells is sealed with a locking water-tight <br /> cap and protected with a traffic-rated vault Further details on well construction specifics are <br /> presented in the drilling logs Procedures used for well construction and drilling are presented <br /> in Appendix C Well installation permits are presented in Appendix B <br /> OPW Vault Investigation <br /> At the request of PHSIEHD, Thrifty conducted an investigation of the OPW vault area <br /> located near MW8 This vault is about 10 inches in diameter and covers what appeared <br /> to be a sewer line clean-out The primary concern of this vault was that it might be a <br /> fill ring to an unknown, unregistered underground storage tank Using the drill ng, a <br /> 24-inch diameter hole was excavated adjacent to the OPW vault At about 3 feet below <br /> grade, a cast iron pipe was encountered that appeared to be a sewer line The line was <br /> /�� intentional) broken at the request of Mr Mike Infurna of PHSIEHD, so that it could be <br /> AV inspected The pipe was connected to the OPW pipe opening, but it could not be <br /> conclusively shown that it was a sewer line However, within a few weeks of this <br /> Page 4 <br />