SITE INFORMATION AND CORRESPONDENCE

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�. .moo Ground Water Monitoring Plan Page 2 4.1.2 Well Purging Data recorded since 1990, when Triple E was first required to monitor the ground water beneath its facility, indicates that well MW-3 has been consistently non-detect for chloroform. Well MW-413 has been non-detect except for three occurrences of chloroform at 2.2 µg/L (April 1990), 0.61 µg/L (June 1991, and 0.9 µg/L(September 1994). Purge volume is 27 gallons from MW-3 and 145 gallons from MW-413. Under the Monitoring and Reporting Program (Order No. 96-118) sampling is being done quarterly. Triple E proposes that purge water from MW-3 and MW-413 be discharged to the soil surface unless chloroform is detected in consecutive sampling events. Purge water (approximately 175 gallons) from monitoring wells MW-1, MW- 2, MW-5, MW-6, and MW-7 will be containerized and discharged to the aeration pond as long as chloroform is present above a concentration of 4.5 µg/L (ppb). Wells XW-1 and MW 4-A are pumping continuously as part of the ground water extraction process and this water is piped directly to the aeration pond. Well MW-2 is also piped directly to the pond. No purge water is developed during sampling from these three wells. in regards to purge volumes, we also enclosing a revised Table 2 for the Ground Water Monitoring Plan that specifies an accurate casing capacity in gallons/foot for calculating purge volumes in the field. 4.5 Monitoring For Ground Water Limitations After discussions and meetings with the Regional Board staff, it was understood that the Monitoring Plan provided adequate monitoring of the ground water beneath the apricot orchard spray field and the aeration pond. To (late, Triple E indicates that the apricot orchard spray field has not been used for disposal of the treated extracted ground water. Nonetheless, Triple E has directed Condor to reassess this part of the Monitoring Plan with respect to Section C of the WDRs. A report of this reassessment will be provided to the Board staff prior to any discharge to the apricot orchard spray field. In regards to the request for a method to determine background water quality for waste constituents other than chloroform in the aeration pond, we seek clarification of the term "waste constituents" used in the WDR. it is our understanding that the waste in this case is ground water containing measurable but low concentrations of chloroform. Triple E is adding extracted ground water to the aeration pond, stripping it of chloroform, and allowing the same ground water to infiltrate back into the ground. The vapor pressure of chloroform (160mm Hg) far exceeds that of water (17mm lig) with the expected result that significant chloroform reductions will occur before the concentration of dissolved constituents is seriously impacted by evaporation. 'Triple E believes that a full Article 5 statistical analysis of each constituent in the ground water is not warranted and would be unnecessarily expensive. L J CONDOR