ARCHIVED REPORTS_HISTORICAL GROUNDWATER ELEVATIONS & ANALYTICAL RESULTS (3)

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i ' Ms. Amy Terrell 31 October 2008 Page 7 iGeochemical Parameters for Expanded Pilot Test Analytical Results The Expanded Pilot Test monitoring program is summarized in Table 4. Results of geochemical parameters measured during the baseline monitoring event and the two monitoring events performed since the injections (including the August 2008 monitoring event) are presented in Table 6 and are summarized below. Baseline samples were collected in August and September 2007 prior to conduction the HRC-X®injections. ' A suite of reactive zone indicator analyses were sampled during the baseline and August 2008 monitoring events. • Groundwater quality indicators of a reactive zone are present: o Redox potential (ORP) decreased in the intergrid and downgradient monitoring wells indicating that conditions amenable to reductive dechlorination are present. The largest decrease was in the on-site intergrid monitoring well MW-6R, which decreased from 175 to -163.4 mV. In the upgradient well MW-4, ORP increased. o Dissolved organic carbon increased significantly from 3.6 to 42 mg/L in the ' intergrid monitoring well MW-6R, indicating that the HRC-X° is slowly degrading and that bioavailable carbon, capable of promoting growth of microorganisms, is present. ' • Terminal electron acceptors were detected in groundwater indicating that conditions in groundwater capable of reductive dechlorination is present. o Dissolved manganese increased slightly from the baseline concentrations at the intergrid and downgradient monitoring wells. ' o Dissolved iron concentrations in MW-2 are near the concentration levels observed following the initial remediation pilot study. In MW-2 the concentration increased to 7.80 mg/L during this monitoring event from a baseline of non-detect and March and May 2007 concentrations of 3.53 and 4.22 mg/L, respectively. • An increase in methane concentrations indicates that reducing conditions are present in groundwater. Methane increased by at least an order of magnitude from the baseline concentrations in all of the intergrid and downgradient monitoring wells. The largest i P:\PRJ2003REM\WFS\VER\VERG\3Q08\Report Text\3Q08 Report WFS-VER.doc engineers I scientists I innovators