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06/330/99 WED 16:50 FAX 510 8r"�8205 CE214 HILL Ya \ QJ 001 'I <br /> CH2MIHILL FAX cM2M MILL <br /> Tel 510-261-2688 ext 2101 <br /> Fax 510-622-8101 ( <br /> To: Richard Fish-(925) 944-1524 From: Keith Sheets <br /> Steve Ronzone (559) 587-1737 r <br /> Company: Del Monte Foods Date; June 30, 1999 f <br /> Fax No.: Total ar / <br /> Pages. I <br /> Voice No.: (925) 944-7276 <br /> Message: <br /> Attached is a revised summary scope of work and cost estimate for the Disco site.The scope <br /> has been reduced;and two dnlfulg methods are utilized to reduce costs. <br /> iResonant Sonrc dnllritg isproposed-Eor.,the boring and'monitoring well withui the core of j <br /> lite pl11m'2 only Iffavorable''geologie conditioiis'arepresent the mifial boring drilled for ` <br /> eollecting the grab'groundwater sample maybe left open and then converted to a <br /> monitoring well,reduurlg tihe number of borings to be grouted.and drifted to <br /> Favorable geologic conditions will be the presence of a 3 to 5 foot thick clay layer beneath <br /> 100 ft bgs. A confining layer such as that will allow us_to place conductor casing into it, f <br /> effectively seahng off the upper and lower zones If a confining layer'is not present <br /> (unlikely) then`we'woulu have to grout up the boring and redrill the for well'anstallation:" <br /> (Two independent bids (Resonant Sonic &Boart Longyearll were solicited, and they are <br /> within$300 of each other-see cost estimate) II <br /> i <br /> The downgradient morutoring;we]]s will b installed using hollow stem:auger.�Tlie <br /> oblecfive'of these wells is to determine the extent of the plume;`thereforc,we want them to <br /> . .� <br /> be non-detect for TPH-I recommend that these wells be installedIn`the houlder ofahe;'"`� I <br /> Ftee ay eliminate the sampling locations on the freeway off-tamp.Tl1is adds about 60 <br /> Eeet;and will ensure that the wells will be non-detect. If they are installed on the off-ramp, <br />'i there is a much greater risk that TPI i will be detected. If we!lave anon-detect.in the wells Y <br /> on the shoulder,we wilt know theat:ihe_plitme'ez"tends to a point Somewhere between the <br /> source-and-150 feet downgradrent which should lie sufficient enough for the regulators. <br /> ncertatnty eiiLsts oFwhere to screen the dowrtgiadientwells.We must make sure we <br /> have Agieement in advance from all stakeholders of the correct depths For screening these <br /> wells. We have two options to resolve the screen depth: <br /> 1. We can make calculations and assumptions on what depth we think the plume will be <br /> 150 feet downgradient,,and screen,accordingly rAssiiming t�he"coyof the plume is STT <br /> between about 70 and 90 ffbgs,placing the screen between go-and'-100 ft bgs should r <br /> t(a <br /> uitercept it(ad us <br /> must be made for elevation differences between the freeway <br /> and the site)' <br /> please call it pages are missing or Illegible or It you receive this tax In error. <br /> 06/30/99 WED 15: 47 ITX/RX NO 86421 <br /> J <br />