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r)4117 '95 11 :01 'D:PG- :Sciences FAX:510-866-F`5 PAGE 4 04/17/86 10:01 V510 746 4232 GTis WC 11004 WENDY L COHEN '2' 10 April 1995 radiant One well will be uaaaM for JUrtho.gradient tacdng to datsrmiae whether the water table is induenctd by tidal impacts on the nearby 14frddlc Rivet. W&LAr levels in the test wall will be manitored evty IS minutes for a 24--horn period. Both t3►t soil and ground vrala samples win be analyud for total purgeable petroleum hydrocwtons(TPpM,total mtractsble hydrocarbons(TEAM and benzen*, toluene, ethylbenzene, and xylene(BTEX)by Standard methods. My comments on the workplait are outlined below. COANMNTS ON WORK PLAN Sail The soil boring and sampling program on page 4-3 of the work plea does not clearly state whether aA borings will be cored or only those which are selected for well installation,nor does the plan sort* whether coring will be continuous or at intervals(i.e., every five feel). Coring should be continuous unless otherwise justified. The program also does not explain the cit"for sample selection, other than that the samples will be collected at intervals"no areata than fivo feet." Above the water table, samples with the highcrt PID readings in each sampling interval should be selected for laboratory analysis. Below the water table, a screening method should be selectod which is cflkctive on wet cores. Coring and sampling should continue to u kast 1S feet bellow the water table to dexarrtine lithology, regardlesa of screening results, and beyond 15 feet below the water table if the results of screening show hydrocarbons. The work plan dons not adequatdy demonstrate that diethylens glycol, triethyleree glycol, and tetraethylene glycol, which have been previously detected in the reboiler unit condensate, do not break down into compounds fbr which thane are water quality objectives(.e., ethyiene glycol). Therefore,the sots samples proximate to the reboiiler unit should be tested for glycal compounds using high pmfunnance liquid chromatography(fULQ_ Additional borings are needed northwest and northeast of the reboiler art toward the site boundaries for Lateral representation of the extent of hydrocarbons in the soli. Gr"xd Water Since the lateral wamt of hydmcarbons in aha soil is not likely to be the same as in the ground water,weU locations ahould be selected based on gradient information, as well as soul analysis results. Water levels should therefore be measured, and gradient information updated, as each well is installed, so that the information may be used in selecting the location for the next well. Additional wells arc needed in the central part of the site, within approximately 50 feet of the reboiler unit, to gather ground water contamination level data for interim remedial design purposes. As requested in our 5 December 1994 letter and ace mpanying tme:morandum,ground water samples should be analyzed for glycol compounds using HPLC, and for semi-volatile organic compounds by standard methods. JDM:jdngtsb