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Mr,.*Joe Hofbauer - 3 - 10 July 2007 <br /> Pioneer Americas LLC <br /> Therefore, annual sampling must continue. However, Pioneer may submit the results of <br /> VOC testing they conduct to meet California Department of Health Services well permit <br /> requirements; <br /> 6. Abandonment of Monitoring Wells MW-4 MW-5 and MW-8. On 29 May 2007, Regional <br /> Water Board staff approved Pioneer's 16 March 2007 work plan proposing to abandon <br /> onsite monitoring wells MW-4, MW-5, and MW-8. These wells were no longer needed for <br /> the continued monitoring of the Upper or Middle Horizon groundwater beneath the <br /> Facility. Monitoring wells MW-1, MW-2, and MW-8 will be sufficient for future onsite <br /> monitoring of these horizons; <br /> 7. Semiannual Depth to Groundwater Measurements in Monitoring Wells MW-1 through <br /> MW-13. Pioneer proposes to reduce the frequency of depth to groundwater <br /> measurements in the Upper and Middle Horizon monitoring wells from quarterly to <br /> annually. However, the Regional Water Board does not concur because, until cleanup of <br /> the VOCs released from the Facility is complete, seasonal evaluation of horizontal and <br /> vertical groundwater gradients within and between all three horizons are necessary; and <br /> 8. Reporting Schedule. Pioneer has propoSed to reduce the freq-jency of reporting from <br /> semiannual to annual. Regional Water Board staff must have the opportunity to review <br /> data more frequently than annual. However, the Draft MRP requirement for the first <br /> semiannual report for each year has been simplified. Pioneer has also proposed to <br /> conduct the semiannual sampling in the second quarter and the annual sampling in the <br /> fourth quarters of each year. However, these events must occur in the first and third <br /> quarters of each year because this will continue to allow comparison with data collected <br /> during the first and second semiannual and annual events conducted during the same <br /> quarters by DLA at the Tracy supply depot. These comparisons benefit Pioneer, DLA, <br /> and the Regional Water Board. <br /> Schedule <br /> 1. Pioneer comments on the enclosed Draft MRP are due to the Regional Water Board by <br /> 10 August 2007; <br /> 2. Within 30 days of the date of this letter, Pioneer must submit a work plan to the Regional <br /> Water Board for the design, construction, operation and maintenance of the wellhead <br /> treatment system; <br /> 3. Pioneer must present the status of well AP-2 to the Regional Water Board. If AP-2 has <br /> been converted to a monitoring well, a letter must be submitted that provides <br /> documentation that it will serve as an adequate monitoring well. If the well continues to <br /> be utilized as a water supply well, a work plan must be submitted for construction of an <br />