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KLE[NFELDER <br /> 5 CONCLUSIONS AND RECOMMENDATIONS <br /> Three monitoring wells were installed, developed and sampled to assess ground water - <br /> potentially affected with petroleum hydrocarbons beneath the Nomellini Construction site. <br /> The wells were sampled on February 21,and June 26, 1991.,. a:the'6e&ttd date;a product2 <br /> lave1r,1.approxhratelyj,5 feet thick was flaming on,the water surl4 JF-E:No product <br /> ~~ layer was observed in ei ither of the other two wells,nor was it observed in MW-1 during the <br /> first sampling event. hue to presence of the product layer, a water sample was not <br /> - collected from MW-1 on June 26, 1991. <br /> Concentrations of gasoline and its cornpo�ier,ts were detected in water samples collected <br /> from MW-1, MW-2 and MW-3. The highest concentrations of gasoline (38,000 ug/1) and <br /> benzene (13,000 ug/1),a toxic constituent of gasoline, v ere detected in MW-2 on June 26, <br /> 1991, approximately 70 feet north of the tank excavation. The concentrations detected ori <br /> the second date had increased signiticantly,which is consistent with the presence of product <br /> in MW-1. <br /> Depth-to-ground ware; measured on four dates between February 21 to June 26, 1991, <br /> indicate that ground water beneath the site flou�s,gerJerailymto the,'east bai;flucfrtates lr&h: ! <br /> y east;tortheast tc►xast_sottttiea.�t, Additionally, the hydraulic gradient fluctuates from 0.36 <br /> to 1.38 percent. Based on the ground water gradient direction,MW-1,downgradient of the <br /> excavation, should have had the greatest concentrations of petroleum hydrocarbons <br /> ' detected on February 21, 1991;however, the highest concentrations were detected in ij"W- <br /> nnha'v .;acted as,/ttstwionp2. 3At, <br /> :� coi c vttS""fdaf" a+oral``friigratiar:'"af Ahe`gusglinc' tilts',that area :,,Alternatively, a second <br /> petroleum hydrocarbon source may exist upgradiznt of MW-2. <br /> ., The product layer observed on June 26, 157191, appears to be more consistent with the <br /> estimated ground water flow direction for that date. Its unexpecte';a;=pearance may <br /> indicate that a mass of floating product may be present in the area and is migrating based <br /> on the gradient direction at the tame. Tidal.;fnfluerces;:from,"th.d.port:and pumping.o <br /> domestic'arid"inr ustrtat'we�l iria'�li fin{usa lit SrgXin water gradient direction;.and <br /> therefore,the,position at the product mass# <br /> F18-91-62 10 <br /> Copyright: 1991 Kleinfelder, Inc. <br /> f <br />