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i`f I t: R O U N D W A T E R <br /> r <br /> R 1 0 R E M--E D I AT 1 0 N <br /> E. I. DU PONT DE NEMOURS 8c COMPANY <br /> 4KCDII►D*q1D - <br /> WILMINGTON, DELAWARE 19898 L <br /> CHEMICALS AND PIGMENTS DEPARTMENT <br /> BARLEY MILL PLAZA <br /> February 4, 1988 <br /> Mr. Gary Johnson <br /> Environmental Affairs <br /> California Regional Water Quality <br /> Control Board <br /> Central Valley Region <br /> 3443 . Routier Road <br /> . ,Sacramento, CA 95827--3098 <br /> Dear Mr. Johnson: <br /> This letter outlines Du Pont's current plans for aquifer testing <br /> at Kayo's 4325 Washington St, Stockton, CA site. j <br /> i <br /> The zone to be tested is the first water-bearing horizon. It <br /> consists of sands and silty sands, and is from 25- 62' below the <br /> surface. There may be a partial clay barrier at 50' below surface. <br /> Currently the water table is at 471 , so the zone is unconfined and <br /> contains 15' of water. This zone contains the great majority of the <br /> gasoline contamination at the site. <br /> The aquifer testing will begin Friday, February 5th. The <br /> testing will be conducted by Groundwater Technology Inc. Du Pont's <br /> hydrologist, Dr. Calvin Chien, will be present from the loth through <br /> the 13th to direct testing. A stepped drawdown test of well MW-14 <br /> will be conducted on the 5th to estimate well efficiency and <br /> determine the proper pumping rate for the drawdown test itself. The <br /> sustained pumping test will begin on the morning of the 10th. well <br /> MW-14 will be pumped. The water levels in three well points and in <br /> wells MW-9, MW-10, and MW-11 will be monitored and recorded using <br /> pressure transducers and a data logger. <br /> The insertion of well points will begin Monday, February 8th. <br /> Each well point will be inserted to a depth of 601 , and equipped with <br /> either a 10' or 15' screen at the bottom. One well point will be <br /> inserted 10' west of well MW-14 , just outside of the canopy. A <br /> second will be inserted 15' to the southeast. The third will be <br /> inserted 20' northeast of MW--14 . The well points will be installed <br /> by Du Pont's subcontractor Haliburton Industrial Services, using a <br /> water jet drilling method. We plan to remove the well points <br /> following completion of the aquifer testing. <br /> jl <br />