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1 <br /> Mr.,Joe Hofbauer - 2 - • 10 July 2007 <br /> Pioneer Americas LLC <br /> suitable for monitoring and sampling of the Lower Horizon. Without a suitable well, it will not <br /> be possible to estimate the groundwater gradient in this horizon. <br /> Pioneer has not provided a work plan requested by the Regional Water Board in the <br /> 2 February 2007 letter accompanying the current MRP. This work plan, overdue to the <br /> Regional Water Board as of 15 March 2007, is to be for design, construction, operation, and <br /> maintenance of a wellhead treatment system for the Pombo domestic well. On <br /> 22 June 2007, Pioneer notified Regional Water Board staff by electronic mail that it plans to <br /> replace the Pombo well rather than install a wellhead treatment system. <br /> Pioneer requested eight changes to the MRP in the 30 April 2007 Revision Request. The <br /> Regional Water Board response to each are presented below. <br /> 1. Annual Analyses of General Constituents. The following parameters have been collected <br /> on a semiannual frequency for two years: chloride, sodium, total organic carbon, total <br /> dissolved solids, nitrate, nitrite, sulfate, sulfite, total iron, dissolved iron, ferrous iron, and <br /> total alkalinity. Pioneer proposes to continue semiannual monitoring of chloride and <br /> sodium, and monitor the remaining parameters annually. The Regional Water Board has <br /> incorporated these changes in the Draft MRP; <br /> 2. Removal of Dissolved Iron from the General Constituents List. Pioneer proposes to drop <br /> the requirement for laboratory testing of dissolved iron because ferrous iron field tests <br /> provide similar data. The Regional Water Board has made this change to the Draft MRP; <br /> 3. Semiannual VOC Analyses of Groundwater Samples from Upper and Middle Horizon <br /> Monitoring Wells. Pioneer points out that the VOC plumes in the Upper and Middle <br /> Horizons have been defined and are stable and proposes to change the frequency of <br /> analyses from quarterly to semiannually. The Regional Water Board has incorporated <br /> this change in the Draft MRP; <br /> 4. Annual Sampling of the Homestead, Reed, and Medina Domestic Wells. Pioneer <br /> indicates that quarterly analyses for VOCs in samples from these wells are not necessary <br /> because the wells are used for non-domestic/residential purposes (i.e. toilet flushing) and <br /> proposes annual analyses. Without more information regarding risk to receptors using <br /> these wells, the Regional Water Board requires continued quarterly analyses. However, <br /> any of these wells in which four consecutive quarters of laboratory analyses have not <br /> detected VOCs may be changed to annual sampling; <br /> 5. Discontinue Sampling of AP-1, Banta #1, and Banta #2. Pioneer believes that water <br /> quality data from these production wells used for industrial purposes at the Facility do not <br /> provide relevant data to environmental investigation and, therefore, annual sampling for <br /> VOCs should be discontinued. However, Regional Water Board staff concludes that the <br /> sampling is needed to monitor for adverse impact to industrial use of groundwater. <br />