SITE INFORMATION AND CORRESPONDENCE

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Mr. Curt Richards • - 3 - 9 June 2008 Olin Chlor Alkali Products 2. Pioneer proposed to drop the requirement for laboratory testing of dissolved iron because ferrous iron field tests provided similar data. The Regional Water Board incorporated that change into the draft MRP. 3. Pioneer pointed out that the VOC plumes in the Upper and Middle Horizons were defined and stable and proposed to change the frequency of analyses from quarterly to semiannually. The Regional Water Board incorporated those changes into the draft MRP. 4. Pioneer indicated that quarterly analyses for VOCs in samples from the Homestead, Reed, and Medina domestic wells were not necessary because the wells were used for non-domestic/residential purposes (i.e. toilet flushing) and proposed annual analyses. Without more information regarding risk to receptors, the Regional Water Board required continued quarterly analyses. However, any of these wells in which four consecutive quarters of laboratory analyses had not detected VOCs could be changed to annual sampling. 5. Pioneer believed that water quality data from industrial supply wells AP-I, Banta #1, and Banta #2 at the Facility did not provide relevant data to environmental investigation and, therefore, annual sampling for VOCs should be discontinued. However, Regional Water Board staff concluded that the sampling was needed to monitor for adverse impact to industrial use of groundwater. Therefore, annual sampling was to be continued. However, Pioneer could submit the results of annual VOC testing they conduct to meet California Department of Health Services well permit requirements. 6. As discussed above, on 29 May 2007 (amended 6 June 2007) the Regional Water Board approved Pioneer's 16 March 2007 work plan proposing to abandon monitoring wells MW-4, MW-5, and MW-8. 7. Pioneer proposed to reduce the frequency of depth to groundwater measurements in the Upper and Middle Horizon monitoring wells from quarterly to annually. However, the Regional Water Board did not concur because, until cleanup of the VOCs released from the Facility was complete, seasonal evaluation of horizontal and vertical groundwater gradients within and between all three horizons was necessary. 8. Pioneer had proposed to reduce the frequency of reporting from semiannual to annual. Regional Water Board staff must have the opportunity to review data more frequently than annually. However, the draft MRP requirement for the first semiannual report for each year was simplified. Pioneer had also proposed to conduct the semiannual sampling in the second quarter and the annual sampling in the fourth quarters of each year. However, these events must occur in the first and third quarters of each year because this would continue to allow comparison with data collected during the first and second semiannual and annual events conducted during the same quarters by DLA at the Tracy supply depot. These comparisons benefit Pioneer, DLA, and the Regional Water Board. In a letter dated 10 August 2007, Pioneer requested further consideration of items 4, 5, 7, and 8 of the Regional Water Board cover letter to the draft MRP, dated 10 July 2007.