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ENVIRONMENTAL - - c_oNsuLTA:N-Ts ENVIRONMENTAL tiEAL7Fi DIVISION r, 20 CORPOMJJ P A]A . -RT BRAui,CauFO 92660 1 - -- - _ ��i Fe (949)644-2691 - P 0.__B&368, Stockton CA 952010388' Approved -.. Denied D Conddions� October 19, 1999. Public Health Services an JoaquinCounty = (fir s Piu n i«A- K .e.w�t� Attn Ms. Carol Oz 304 East-_Weber Avenue, Th1r oor i Stockton, California.95201 Subject. (Revised) Work Plan for Groundwater Assessment and Monitoring Well Installation at Joe's Truck Stop, at 15600 South Harlan Road, Lathrop, California. - Ms; OZ: Pursuant to your request, Avalon Environmental Consultants (Avalon) is pleased to submitthis work plan `tq perform a Groundwater A_ ssessment and Monitoring Well Installation_et Joe's Truck Sto _ _ pat 15600 South_Harlan Road_-m Lathrop, County ofSan.Joaquin, California This- - investi ation;-will consist of__installm g g-six groundwater:monitoring :wells on the subject, property.- The purpose of this investigation-is to-establish-the groundwate�;gracr" t;'Nand to= ._ _ monitorlevels of Methyl Tertiary Butyl Ether-(MTBE) and other hydrocarbon contamination= _ in the groundwater The impact was previously---i dentified through=groundwater grab:samples- collected by Avalon, dunng a_Phase II Site Assessment dated December 17;,_1998 Elevated levels of diesel at 11-,000 parts per billion (ppb) and -5;200 ppb were identified rin the- groundwater samples from tw_o:b0rings in the area'of the fo�mer-dies61 tank pit in the southern portion: of the property. Elevated levels of MTBE, were identlfied;ain.-groundwater samples_' taken from.bonng"s in the northern tank_prt area _Levels in the groundwaterwere as`high as } r 1,700.ppb. Due to.these elevated levels of hydrocarbons,-additional characterization was recommended by the consultants This investigation wild consrs4_of dnllmg.and sampling six groundwater monitoring wells on=_ the-subject property The levels of contamination identified in=Avalon's Phase Il:report _ suggests thafthe gradient is to the north, however, atrue-gradient direction on the subjectP. rl property has hot-been,establishe_d We-recommend lacm -:-one monitoring well imthe center `- -P g_of_each of the tank areas (One:in the northern-tank area:and one in the southern tank-area). --Add itional ly,16-ne monitoring=well is:recommended north of the northern tank area and three monrtonng,wells are:recommended mthe remaining three corners of the property. Once monitoring well construction is complete; and the_monitoring wells have been developed, the' - locations and=top of casings-will-be surveyed by a State Licensed;:'Land Surveyor.__Once this= - - - �_ is complete,ahe wells:will be.given one'week to_stabilize;ipnor to=nleasur ng and=sampling___ '. This will allow groundwater-1eve ls"oto-stabilize,--thereby-giving.ace urate data.