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r 4 J <br /> 61 05,June 1998 z <br /> AGE-NC Project No 96-0232 <br /> Page 4 of 4 » ' <br /> I <br /> f � <br /> ' Utilizing EPA methods 8020 'and 8260, concentrations of MTBE were detecte d at <br /> concentrations greater than the State of California Ac <br /> tion Limit of 35 ppb In'gi-'Ound water <br /> , <br /> samples collected from MW-I and MW-2 The MTBE was encountered in ground water <br /> samples at concentrations ranging as high as 400 pp (MW-1, EPA Method 8260) <br /> • The ground water surface at the site is above the slotted screened intervals in well MW-4 <br /> ` Therefore, samples collected from this well may not be representative of dissolved petroleum ✓ <br /> hydrocarbon concentrations in shallow ground water The screen ed`intervals are not known <br /> for wells MW-I and MW-2, however based on current ground water elevation, it is likel <br /> that these screened intervals are also submerged y <br /> • From May 1997 to February 1998, a substantial increase of MTBE was Observe, <br /> MW-2, concenfrations of MTBE remained relatively constant from wells MW-1 and MW-4' - <br /> Thegreatest concentrations of dissolved hydrocarbons and MTBE continues to be in the area >r <br /> of well MW-I <br /> r t z aIt <br /> I <br /> I ! I <br /> I <br /> 5 0. RECOMMENDATIONS' `I <br /> I <br /> Based upon'data collected from the site, AGE recommends <br /> • Installation of at least three additional monitonng wells at the Site Further assessment south <br /> southeast and northwest of MW-I will be necessary to determine the lateral and vertical <br /> extent of dissolved MTBE in ground water and to <br /> monitor possible spieadiiig pflthe plume <br /> as a result of ground water migration y - - <br />�, Dual-complete the well(s) to l <br /> help delineate'vertical extent o <br /> • <br /> _ (MTBE <br /> • Continued monitoring and sampling is recommended as an annual event <br /> , <br /> f <br /> I ' <br /> � ` f <br /> 6.4• LIMITATIONS ` <br /> I , <br /> Our professional serviceswere performed using that de ree of car <br /> e and skill` environmental consultants practicin <br /> analytical results provided' g in this or'simila localities The fiitdings ,eve� based upon rt <br /> by an independent laboratory Evaluations of the geologic/hydro eolo is f <br /> conditions at the sitI for the purpose bf this investigation are made from a limited number of i <br /> " available data'points(i a monitoring wells), and subsurface conditions may vary aw <br />' data points No other warranty, r expressed or Implied, is made as to the ayfrom these <br /> me <br /> recommendations contained in this report _ professional <br /> 1 I r <br /> RdrQneed CeoEnvirontnentai.Inc ` <br /> {I y 4 f <br />