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Il � <br /> €tECrivED'I ^ <br /> M & ASSOCIATES <br /> S <br /> ENVIRONMENTAL k ENGINEERING SERVICES <br /> 11281 RICHMOND AVE. <br /> BUILDING J, SUITE IOOB <br /> tlousTox, TEXAS 770e2-2617 June 5, 1987 <br /> ,SUN 01 1987 <br /> Ms. Laurie Cotulla, R.S. <br /> Environmental Health Division ENVIROMENIAL HEATH <br /> San Joaquin Local Health District VERMITISERVICES <br /> 1601 East Hazelton Ave. <br /> P.O. Box 2009 <br /> Stockton, California 95201 <br /> f <br /> Reference: Monitoring well abandonment and replacement <br /> Dear Ms. Cotulla: <br /> As perq � <br /> your request during our recent telephone conversation, <br /> this letter will identify how the requested monitoring ;�well <br /> abandonment and replacement work will be done at the Kayo Douglas <br /> service station. <br /> Monitoring wells number 1, 1 Redrill, 8, 11, 12 and 13 are <br /> contributing to the problem they were intended to help correct. I <br /> believe you have a copy of my report on the results of recent <br /> cased hole electric logging at this site. The 2" PVC casings' and <br /> screens in these wells and the gravel ,pack will be totally <br /> removed by over-reaming with the same type of hollow stem auger <br /> equipment that was used to install them. The fresh new bore hole <br /> will be pressure cemented from the bottom to the top with anti- <br /> shrink bentonite-cement grout. We use a 1 to 10 ratio of <br /> bentonite to cement to be conservative. Since material costs.� are i <br /> about equal this does not hurt our client and assures a good <br /> seal. The groutwill be brought .all the way to the surface and <br /> the following day the hole will be "topped off" to replace <br /> natural settlement of the grout. <br /> Monitoring wells number 1 Redrill and 8 will be replaced and 'Inot <br /> abandoned. After the old casing, screen and gravel pack have <br /> been removed, new 2" screen, casing and gravel pack will be' <br /> installed. A 4 foot thick bentonite pellet seal will be <br /> installed above the gravel pack, wetted and allowed to swell1or <br /> thirty minutes prior to pressure grouting to the surface with <br /> anti-shrink bentonite cement grout. This time the screen slots <br /> and gravel pack will be sized to suit the geologic formation to <br /> prevent silt and clay from filling in the bottom several feet of t <br /> the monitoring wells. The electric log of number 1 Redrill shows <br /> the bottom of the formation but fill and possibly a too shallow <br /> original total depth in number 8 did not allow the bottom of -the <br /> formation to be found on the electric logs. <br /> ( 713 ) 498 - 3302 <br />