SITE INFORMATION AND CORRESPONDENCE_FILE 2

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Harold and Dena Knowles Page 2 of 3 Former Roek Construction 23 February 2009 102 S. Wilson Way impacted by MTBE from the Top Filling or Arco sites; MW-1 along the west property margin was impacted by contaminants from the Top Filling site. The EHD concurs with many, but not all, of the interpretations put forward by GZA. It does appear that the Arco plume is primarily an MTBE plume, though it locally contains TPH-g (MW-6) and that the subject site plume includes TPH-g, BTEX and 1,2-DCA, but does not include MTBE. The Top Filling site plume includes all these chemicals of concern. Ethylene dibromide (EDB) occurs locally on the Top Filling site an on the subject site, but does not appear to have migrated at concentrations exceeding the analytical method detection limits. The plume along the south margin of the subject property appears to be a commingling of the Top Filling and Arco plumes based on the chemical composition, the plume along the down-gradient, eastern margin appears to be related to the Top Filling and/or Arco plumes, but the EHD believes that the subject site plume contributes to it based on the 1,2-DCA content. The 1,2-DCA concentrations in monitoring wells MW-15B and MW-150 appear to be rising, indicating a migrating, unstable plume. The EHD believes that the 1,2-DCA in these wells and in MW-12 most likely originated from the release on the subject site. The EHD considers your site to be sufficiently characterized to justify preparation of a corrective action plan (CAP) to move toward remediation. The EHD has previously directed: • Preparation of a CAP or feasibility study (directed by EHD letter dated October 26, 2006, due January 3, 2007); • Preparation of a schedule to reinitiate operation of the soil vapor extraction (SVE) system on your site (directed by EHD letter dated October 26, 2006, due November 15, 2006); and • Preparation of a work plan to initiate interim groundwater remediation (directed by EHD letter dated August 31, 2005, due January 3, 2006). To date, none of these documents have been submitted to the EHD. The data for your site shows that the concentrations of dissolved contaminants in groundwater on your site is unlikely to decline below levels of concern within a reasonable timeframe and that active remediation will be needed to move your site toward closure, therefore the EHD directs submission of a CAP no later than 15 June 2009. The EHD has reviewed the sampling requirements for your site and will approve the following schedule: • Semi-annual sampling — MW-1, MW-2, MW-5, MW-12, MW-1313, MW-15B and VW-1; • Annual sampling — MW-6, MW-8, MW-9, MW-10, MW-11, MW-15A, MW-15C, MW-17C, VW-2, VW-3, VW-4, VW-5 and VW-6. Comment and Directive Letter 0209