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June 30, 1995 <br /> Page 7 <br /> release which has naturally attenuated, (2) a limited release that was <br /> not of significant enough volume to reach these areas, or(3)the <br /> samples were not collected in the migration pathway of the <br /> hydrocarbon release. The low to non-detectable concentration of <br /> dissolved hydrocarbons which underlay the site indicate that the latter <br /> (3) is likely not the case and that further investigation of this area is <br /> not warranted. <br /> 3. Soils beneath piping at the site have not been investigated and there- <br /> fore are not characterized. <br /> Soil data from the borings for Wells MW-1 and MW-6 help define the <br /> limits of any release that may have been associated with the former <br /> piping. In addition, groundwater results at MW-6 and MW-7 support <br /> that a significant hydrocarbon release is not associated with the former <br /> piping. The assumption that hydrocarbons occur beneath the former <br /> piping appears unfounded somewhat, however, three additional <br /> borings are proposed to investigate these areas. <br /> 4. The first groundwater sample collected from Well MW-2 on 12191 <br /> evidenced contamination likely from an upgradient source. Since a <br /> soil analytical investigation has not been performed at the upgradient <br /> source, the contribution from this source can not be estimated. <br /> As a result, one soil boring is proposed to investigate possible <br /> hydrocarbon impact to soils upgradient from MW-2 (see Figure 4 of <br /> the CAP revision) <br /> 5. EPA Method 602 for BTEX analyses should be performed by EPA <br /> Method 624 to differentiate these compounds from the chlorinated <br /> plume. <br /> The EPA Method 624 that is referenced above has been performed on <br /> groundwater samples collected from site wells on many occasions. <br /> The results of these analyses have confirmed the presence of BTEX <br /> constituents at Well MW-2. However, while the chlorinated plume is <br /> suspected to interfere with BTEX measurements at the other site <br /> wells, the reported concentrations at each well are below the <br /> respective detection limits associated with the EPA Method 624. <br /> 32013 570CAYLET.UOC.doc <br />