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16 CLEARWATER
<br /> 5 _ G R 0 if P, I ,N C
<br /> 4.2 Groundwater Sample Analytical Results
<br /> ' Low to moderate concentrations of TPHg were detected in samples collected from
<br /> MW-1, MW-3, and MW--5 Lab analysis of the sample collected from MW-2
<br /> indicated the presence of 26,000 ppb TPHg. BTEX compounds were detected in
<br /> ' groundwater samples collected from monitoring wells MW-1, MW-2 and MW-5 A
<br /> summary of groundwater elevations and analytical results is presented on Table 1
<br /> ' Hydrocarbon concentrations are displayed graphically on Figure 4 A copy of the '
<br /> laboratory reports and chain-of-custody forms are attached in Appendix B
<br /> a
<br /> , I
<br /> ' 5.0 RECOMMENDATIONS
<br /> Based on the results of the two quarters of groundwater monitoring that have
<br /> followed the installation of MW-4 and MW-5, it is°apparent that-active remedial
<br /> action may be required 'un order to lower'concentrations of dissolved hydrocarbons
<br /> in groundwater to agency-acceptable levels ' It is also apparent that the
<br /> downgradient extent of hydrocarbon contamination (northwest of MW-5) has not
<br /> been defined
<br /> In order to obtain information required for effective corrective action, it is
<br /> recommended that the following tasks ,be planned and,conducted. , '1) Install a single additional groun,dwater monitoring well do�vngradient from
<br /> MW-5, across Yosemite Street from the subject (site '(as initially recommended in '
<br /> previously submitted workplan) I The well- should ,be constructed line a manner R
<br /> similar to MW-5, aeye
<br /> nd surveyed, sampled and monitored along with,the other'wells '
<br /> during the second quarter of 1995
<br /> 2) Two vapor extraction and two air sparging wells should be installed on site The
<br /> wells should be utilized for the completion of a combined vapor extraction/air
<br /> sparge ,g pilot test ,
<br /> 3) Slug tests,should be completed' using several on site wells The'data collected
<br /> i during the'slug tests should be;utilized,to calculate the physical'characteristics of the
<br /> water bearing zone immediately beneath ,the subject site 1,
<br /> 14) A Problem! Assessment Report (PAR) should be prepared The PAR should
<br /> I i present the�'results`'of�tHe installation and sampling of thea newest well, as,well as at' ;
<br /> I ; rsummaryl`of the investigation to, date,, and r�shoul'd I evaluate !the feasibility of, air I f '
<br /> 1 , , sparging and soil I vapor extraction ias remedial) alternative's' ,Other, reasonable I
<br /> alternatives' should also be comparitively,pr'esente'd m' thel'PAR,f !i,h!
<br /> I ' I ' El i
<br /> 1`With the concurrence of the PHS/EHD, a workplan for, the `installation1 of, the, I'
<br /> recommended^well and the completion ,of pilot testing' activities will be prepared '
<br /> Land submitted
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