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1 <br /> F <br /> F <br /> F ' I <br /> 17 August 2006 <br /> AGE-NC Project No. 01-0827 <br /> Page 2 of 5 <br /> monitoring reports. The operation of the IAS system has produced only minor volatilization of the <br /> dissolved hydrocarbons in the deep ground water.well samples at the site(VW-21)),but has reduced <br /> the dissolved hydrocarbon concentration in the shallow well samples (MW-1 and VW-1), as well <br /> as the concentrations of hydrocarbons in the SVE influent, below detection levels. <br /> f <br /> An EHD letter, dated 03 January 2003,requested procedures for evaluating the effectiveness of the <br /> operation of the IAS system with a low-flow ozone generator. AGE proposed to augment the IAS <br /> system with a low-flow ozone generator in Ozone Sparging and Additional Monitoring Well <br /> Installation Work Plan, dated 07 October 2002. Operation of the ozone injection system has been <br /> ongoing since July 2003, resulting in a general downward concentration trend with an increase in <br /> dissolved concentrations after installation of additional sparge-diffuser OZ-1. <br /> i Site Conceptual Model, dated 25 February 2005, was prepared by AGE at the verbal request of the <br /> ` EHD during a meeting on 20 January 2005. The lateral extent of dissolved hydrocarbons north and <br /> northeast of the former UST release area may not be fully defined and requires additional shallow <br /> assessment of the impacted soil and impacted ground water limits. <br /> 2.1. GROUND WATER DEPTH AND GRADIENT <br /> III Based upon ground water monitoring well information obtained from the site (100 feet northwest <br /> of the southern UST area), ground water flow direction is northeasterly to easterly and currently <br /> j occurs at a depth of approximately 20 feet,below surface grade (bsg) within ground water wells. <br /> Ground water occurs in a generally sandy layer extending from approximately 20 feet to 30 feet bsg. <br /> Based on cross sections on-file with the EHD, the sedimentary units are thought to be relatively <br /> horizontal and continuous over the area. <br /> 3.0. SCOPE OF WORK <br /> Based on site assessment data collected, both the dissolved concentrations and the SVE <br /> concentration of petroleum hydrocarbons have declined and confirmation of the remediation is <br /> required. AGE proposes to perform confirmation soil sampling at the site and to evaluate the <br /> potential for risk to human health and the environment. <br /> AGE proposes to drill four soil probe borings for soil sampling at the site to characterize the <br /> remaining hydrocarbon mass. The scope of work will consist of the following tasks: <br /> { <br /> • Pre-field work activities; <br /> • Soil boring advancement; <br /> Advanced GeoEnvironmental,Inc. <br /> I <br />