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a-.. ad"' �+ " - PMM ' �W, i rn � �� KcEI�FFI []EIt 5 CONCLUSIONS AND RECOMMENDATIONS Three monitoring wells were installed, developed and sampled to assess ground water potentially affected with petroleum hydrocarbons beneath the Nomellini Construction site. The wells were sampled on February 21, and June 26, 1991. On;the second'date;a product, layer;approxunately-l,S.feet thick was flowing on the water surfq�c, nWl No product layer was observed in either of the other two wells,nor was it observed in MW-? +!wring the first sampling event. Due to presence of the product layer, a water sample was not collected from MW-1 on June 26, 1991. Concentrations of gasoline and its components were detected in water samples collected from MW-1, MW-2 and MW-3. The highest concentrations of gasoline (38,000 ug/1) and benzene (13,000 ug/1), a toxic constituent of gasoline, were detected in MW-2 on June 26, 1991, approximately 70 feet north of the tank excavation. The concentrations detected on the second date had increased significantly,which is consistent with the presence of product in MW-1. `lY-w Depth-to-ground water measured on four dates between February 11 to June 26, 1991, indicate that ground water beneath the site flows.generally to the east hutfiuctuates from.;,; east-noriheast•to, cast-southeast; Additionally, the hydraulic gradient fluctuates from 0,36 ...Y.Ik.+..... .. Vis..i .._...i �_ <... .. to 1.38 percent. Based on the ground water gradient direction, MW-I,downgradient of the excavation, should have had the greatest concentrations of petroleum hydrocarbons detected on February 21, 1991; however, the highest concentrations were detected in MW- 2, Uttls+:y;line's' showm=1Plaie� ran nb tl±.;of,the-excavation and.;may;haveacted as% conduits far laterttl m gratron"of A e,"gasoline into that area. -Alternatively, a second petroleum hydrocarbon source may exist upgradient of MW-2. The product layer observed on June 26, 1991, appears to be more consistent with the estimated ground water flow direction for that date, its unexpected appearance may indicate that a mass of floating product may be present in the area and is migrating based oti the gradient direction at the time. Tidall fluences from the port and pumping of domestic and` ndustrtal wells may ben,.€ uectg,tkground water gradient direction;-a-HA ; therefore,the',ppsition'at.the product massl FI8-91.62 1[) Copyright 1991 Kleinfelder, Inc,