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Mr. Nathan Crum - 2 - 20 January 2011 <br /> Valley Pacific Petroleum Services <br /> 1.26% and 4.1% measured in monitoring wells MW-6R and MW-8 at distances of 51 <br /> feet and 15 feet from VEW-1, respectively. Laboratory analytical results of influent vapor <br /> samples collected from VEW1-D contained the highest petroleum vapor concentrations. <br /> During the 24-hour testing period, Valley Pacific estimates that the SVE system removed <br /> about 260 pounds of gasoline hydrocarbons from VEW1-D. A considerably smaller <br /> hydrocarbon mass was removed from VEW1-1 and VEW1-S, where induced vacuums <br /> were considerably higher. Based on these results, Valley Pacific proposed to prepare a <br /> CAP using the SVE system, which has been inactive since the pilot test was completed. <br /> The 29 December 2010 CAP proposes to perform site remediation using the VEW well <br /> cluster, and then to evaluate supplementing the system with air sparging (AS) if SVE <br /> influent levels become asymptotic. Page 14 of the CAP presents a schedule for <br /> implementing the remedy following Central Valley Water Board staff concurrence with <br /> the CAP. Along with other San Joaquin Valley Air Pollution Control District regulatory <br /> obligations, the schedule allows two months for a public comment period because the <br /> site is located within 1 ,000 feet of a public school. Based on an 18 January 2011 phone <br /> conversation, GZA anticipates that SVE will be implemented in 10 months and may be <br /> operated as such for about two years. <br /> The CAP proposes that after influent SVE concentrations have declined and become <br /> asymptotic, Valley Pacific will prepare a report recommending the advancement of <br /> confirmation borings and, if appropriate, the removal the extraction system and case <br /> closure. Valley Pacific anticipates developing soil cleanup levels consistent with San <br /> Francisco Bay Water Board environmental screening levels (ESLs). Valley Pacific will <br /> propose that active cleanup be considered complete when groundwater monitoring <br /> confirms that natural attenuation will achieve cleanup within a reasonable timeframe and <br /> significant threats to human health and the environment do not exist. <br /> Our comments are presented below. <br /> 1 . Section 4.0 of the CAP states that air sparging will be evaluated and implemented <br /> following the operation of SVE for a period of time, when influent vapor levels have <br /> become asymptotic. This statement appears to contradict the proposed cleanup <br /> strategy described in Sections 5.5 and 5.6, which states that Valley Pacific will <br /> recommend removal of the SVE system and case closure when vapor concentration <br /> decline becomes asymptotic. <br /> Valley Pacific selected air sparge/soil vapor extraction (AS/SVE) to remediate the <br /> COCs in the groundwater and vadose zone based on the rationale that AS/SVE would <br /> likely enhance the biodegradation potential at the Site by increasing the dissolved <br /> oxygen levels in groundwater. Valley Pacific supported this stance based on <br /> Monitored Natural Attenuation monitoring conducted between 2008 and 2009, when <br /> they concluded that microbial activity is occurring within the plume. Thus, we will <br /> require Valley Pacific to adhere to the cleanup plan that includes incorporation of AS <br /> into the SVE system before SVE treatment is discontinued. <br /> 2. Cleanup goals for soil and groundwater will be formulated in accordance with the <br /> State Water Resources Control Board's Resolution No. 92-49, which requires <br />