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J <br /> -r Working To Restore Nature <br /> } The expected concentration of TPHd in groundwater at the site can now be estimated using the <br /> average concentration of TPHd remaining in the soil by the equation: <br /> t=f <br /> Cw = Cs/Kd = 55 ppm/940 = 0.059 ppm = 59 ppb <br /> f <br /> This value is essentially the same as the detection limit of 50 ppb for TPHd in water. <br /> By the same method soil distribution coefficients were calculated for the residual BTEX <br /> constituents. Potential groundwater concentrations were determined using the maximum <br /> remaining soil concentrations: <br /> B: Kd = 17 Csmax = 0.05 ppm Cwmax = 3 ppb <br /> T: Kd = 38 Csmax = 0.34 ppm Cwmax = 9 ppb <br /> E: Kd = 86 Csmax = 1.30 ppm Cwmax = 15 ppb <br /> X: Kd = 86 Csmax = 0.93 ppm Cwmax = 11 ppb <br /> With the exception of benzene all the calculated values are below their respective primary and <br /> secondary MCLs. The benzene calculation was based on the single detection from the five soil <br /> samples collected within the area of residual soil contamination and therefore greatly <br /> overestimates the potential impact. Benzene has not been detected in groundwater at the site <br /> since the anomalous sample collected from MW4 in May, 1990. According to the above, <br /> rr; residual soil contamination at the site should not be capable of impacting groundwater to a <br /> significant extent. <br /> FFr� <br /> 5.3 Site Specific Information Summary <br /> O Municipal, industrial and agricultural wells within a one half mile radius of the site are <br /> identified on Figure 5. <br /> 7 OW01951REPORTSICL012594.FNL 11 <br /> j <br /> �i� <br />