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IN/ <br /> i .. March 6, 2001 <br /> San Joaquin County Motor Pool Facility <br /> Supplemental Contamination Assessment Workplan <br /> Phase One <br /> The Phase One exploratory borings will consist of initial and step-out borings. The <br /> locations of the initial borings are illustrated on Figure 1 (attached). Advancement and <br /> sampling of the exploratory borings will proceed until the lateral and vertical extent of soil <br /> and groundwater impact is delineated based on the results of laboratory analyses. If soil <br /> and/or groundwater contamination is evident in samples collected from the initial borings, <br /> the grid pattern will be expanded to locate and advance additional step-out borings. <br /> Advancement of step-out borings would continue until soil and/or groundwater impact is <br /> no longer evident. Locations and rationale for the step-out borings, if any, would be <br /> ' reported verbally and via correspondence to the San Joaquin County Public Health <br /> Services, Environmental Health Division. A separate work plan for advancement of step- <br /> Foutiborings-wou d not+�be- ubmitted. This-reporting scenario will a 6 "the supptepientary <br /> contamination ass essr en�to proceed continuously. 1t <br /> Due tol the d&ns It lvery dens __predominately granular flu4ia de osi sil lsa4 to <br /> sands) encountered d n ,g the initial site assessdneft,�T ro ellevha <br /> electronic cone pene ronetry (E P) woul be a viable dptit a va e �{pl rator ' <br /> b' rings, or to c lePdlaboratory <br /> resent h soil groundwat r ample f r I o a o �n lyslos. <br /> T�erefore, the4epl aborings w6ill b drilled an sampled u ing ho I w-stemau erdrilling and salinpds/techn que . At eachi a Iplorato ori g it samples r 1 <br /> lithologic descriptlonia -analy es will be doll ct a fi a-f of i tervals`. Upon <br /> encountering grounitlwater, a disposable bailer will jbe to i side thehollow-stem <br /> auger to collect '(a groundwater sample fo� laboratory 1a lys s. i Cbl orhia-certified s <br /> mobile laboratory, lll be used to analyze tie oil and yroundw�ttr sflple oil cted <br /> Laboratory analyses of soil samples colt ct1d below groundwater (-40 to 45 feet be] <br /> q` ` <br /> La and surficel_pbgs]) to a total depth of aifeet bgs duringAhe irlitial�te essment in <br /> borings B-1 and B-2 were found to contain elevated concentrations of TPH-G, BTEX and <br /> MTBE. To determine the vertical extent of soil contamination the proposed initial <br /> exploratory boring (B-8) east of and immediately adjacent to the former location of UST#3 <br /> as illustrated on Figure 1 will be advanced and sampled to 100 feet bgs. <br /> Phase Two <br /> Phase Two will involve evaluating the physical and analytical data generated by Phase <br /> One to locate and design groundwater remediation wells and plume monitoring wells to be <br /> installed at the Site. Ideally, the remediation wells would be installed along the axis of the <br /> delineated groundwater plume, with monitoring wells located along the flanks, up-gradient, <br /> and down-gradient relative to the groundwater plume. <br /> Page 2 of 5 <br />