|
1
<br /> 25 October 2001
<br /> AGE-NC Project No 97-0301
<br /> 1 Page 6 of 7
<br /> between 20 and 35 feet bsg, 70 and 80 feet bsg(transition between Second and Third Water
<br /> ' Zones) and between 105 feet and 110 feet bsg(transition between Third and Fourth Water
<br /> Zones) Variable lithology, including silty fine sand and sandy silt,was observed at all other
<br /> ' depths (Figures 3, 4 and 5)
<br /> • Dissolved constituents of concern detected at P-5, P-6, P-7, P-8, P-
<br /> 9 and P-10 were TPH-g,
<br /> TPH-d,BTEX, MTBE and 1,2-DCA(Table 1)and have previously been detected in ground
<br /> ' water samples collected at wells MW-1,MW-2,MW-3, MW-4, MW-5, MW-6 and MW-7
<br /> Constituents of concern detected in First Water Zone,Second Water Zone, Third Water Zone
<br /> and Fourth Water Zone are depicted by informal hydrogeologic units in cross sectional views
<br /> ' D-D', E-E'and F-F'(Figures 6, 7 and 8,respectively)
<br /> • First Water Zone fuel-impact at the site includes TPH-g, TPH-d, BTEX, MTBE, TBA and
<br /> ' 1,2-DCA constituents, the greatest First Water Zone fuel-impact was reported at monitoring
<br /> wells MW-1,MW-7 and soil bonngs P-1,P-4 and P-7 The estimated extent of First Water
<br /> Zone fuel-impact is depicted in Figure 9
<br /> ' Second Water Zone fuel-impact at the site includes TPH-g, TPH-d and BTEX constituents
<br /> in the area of MW-5, P-5,P-7, P-9, and 1,2-DCA constituents in the area of MW-5, P-7 and
<br /> P-8, the greatest Second Water Zone fuel-impact at the site was reported at P-7 The
<br /> estimated extent of Second Water Zone fuel-impact is depicted in Figure 10
<br /> ' Third Water Zone fuel-impact at the site includes TPH-g,benzene and 1,2-DCA constituents
<br /> in the area of P-10 and TPH-d and 1,2-DCA constituents in the area of P-8 The estimated
<br /> extent of Third Water Zone fuel-impact is depicted in Figure 11
<br /> ' Fourth Water Zone fuel-impact at the site includes TPH-g, TPH-d and BTEX constituents
<br /> in the area of P-5 and TPH-d-impact in the area of P-6 and P-8 The estimated extent of
<br /> Fourth Water Zone fuel-impact is depicted in Figure 12
<br /> 1 ,
<br /> ' 4.0. RECOMMENDATIONS
<br /> Based upon the CPT investigation results during the 3rd quarter 2001, AGE recommends
<br /> ' • Continued quarterly ground water monitoring, the next quarterly ground water monitoring
<br /> event is tentatively scheduled for December 2001
<br /> ' • Conduct a ground water extraction test to obtain general aquifer characteristics such as
<br /> hydraulic conductivity, transmissivity, storativity and drawdown at various pumping rates
<br /> ' Results of the ground water extraction test would be utilized to estimate a radius of influence
<br /> for the zone of capture of dissolved petroleum hydrocarbons and to evaluate the feasibility
<br /> of ground water extraction as a remedial option
<br /> Advanced GcoEnvironmental,Inc
<br />
|