ARCHIVED REPORTS_XR0005387 - Laserfiche WebLink

Home Browse Search

Beacon Station No.474 August 26, 1997 Stockton California Remedial Testing Report Sstorativity (S) was 0.222. Using an aquifer thickness of 20 feet from the boring log for pumping well MW-2, results in an estimated value of hydraulic conductivity (K) of approximately 88 feet per day. Based upon the above calculations, the hydraulic conductivity (K) values of 29 to 88 feet per day are somewhat higher than expected, as the aquifer materials encountered beneath the site have been described as consisting predominantly of clayey silt (ML) with some fine-grained sand (SP). Conclusions Based upon the above field test data and using time-drawdown calculations, an average value of hydraulic conductivity (K) of 29 feet per day was used to calculate a theoretical steady state capture zone that would be created by pumping from monitoring well MW-2 at a rate of 2.0 gpm. The downgradient stagnation point was estimated to be approximately 20 feet and the maximum width of the capture zone was estimated to be approximately 126 feet. Graphical representations of the average theoretical capture zone at a pumping rate of 2.0 gpm is shown in Figure 4, Theoretical Capture Zone at 2.0 gpm. Sustained, continuous pumping Iikely will result in a larger capture zone, as is suggested by the groundwater levels collected on May 28, 1997. • With 27,210 gallons of groundwater being pumped from well MW-2, approximately 6.3 pounds of TPHg and 1.7 pounds of benzene were removed from the groundwater during the pumping The results of the groundwater pumping tests and capture zone calculations reflect the relatively flat groundwater gradient beneath the site, and the very fine-grained water-bearing materials present beneath the site. The calculated hydraulic conductivity (K) values may indicate the presence of sandy stringers (SM or SC) within the predominantly fine-grained matrix (ML and CL) described in the boring logs. 1474.11-rpt 4 HORIZON ENVIRONMENTAL INC.