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Mr.`Nathan Esformes - 3 - 18 August 1998 pumping and the model input and calibration data shall be reported; and 4) initial results of the model simulations shall be provided as part of the third quarter 1998 groundwater monitoring report. WDRs No. 96-118 require that the discharge of treated groundwater to the aeration pond disposal area and the apricot orchard spray field shall not cause groundwater underlying the disposal areas to contain waste constituents, except for chloroform, in concentrations statistically greater than background water quality. For the purposes of comparison, the WDRs state that background water quality shall be determined by monitoring wells upgradient of the individual disposal areas when background monitoring provides sufficient data. Monitoring well MW-1 is presumed to be this background well for both the aeration pond and apricot orchard spray field, even though it is downgradient of the spray field. The contamination of well MW-1 by chloroform from either the aeration pond, stormwater pond or the apricot orchard spray field raises the question of whether well MW-1 can still be considered representative of background water quality. My review of the historic general mineral water quality data for well MW-1 finds that there has been a significant increase in the concentration of iron since 1993. The concentration of iron has risen from approximately 25 mg/l before 1993 to as high as 690 mg/l since then. This increase may be due to infiltration from the aeration pond of groundwater extracted from well MW-4A which has a high concentration of iron or may be due to discharges to the stormwater pond or apricot orchard spray field. Thus, the increase in iron and chloroform concentrations in well MW-1 raises the issue of whether this well still is representative of background water quality. An investigation is needed to determine whether the groundwater quality in well MW-1 is representative of background for both the aeration pond and apricot orchard spray field. Monitoring and Reporting Program (MRP)No. 96-118 requires that monitoring of the treatment plant effluent be done weekly for the first month and then quarterly at the beginning of each year's discharge to the apricot orchard spray field. We have been unable to locate the treatment plant effluent monitoring reports in our files. Therefore, Triple E needs to resubmit copies of the treatment plant effluent monitoring report for periods that the treatment plant and apricot orchard spray field operated since May 1996. The groundwater monitoring reports do not report on concentrations for all of the constituents required in MRP No. 96-118. Ammonia, boron, iron, phosphate and silica were not analyzed in the June 1998 annual sampling event. In addition, the required influent flow data was not collected for the groundwater extraction system or the aeration pond, and required effluent flow data are not reported for the treatment plant. The missing chemical constituents shall be sampled as part of the next sampling event, presumably the third quarter 1998 sampling event. Influent and effluent flow data shall be collected and report as required by MRP No. 96-118. By 20 October 1998, please provide a revised work plan for investigating the source of chloroform contamination in well MW-1. This revised work plan shall include information on the volume and duration of reduced discharge to the aeration pond necessary to demonstrate the impact of the groundwater mound, propose a statistical method for comparing changes in chloroform concentration in well MW-1, propose a method for measuring the mound height and water quality of the groundwater beneath the aeration pond, propose a method for evaluating whether well MW-1 is representative of background water quality, propose a method for investigating the impacts of the apricot orchard spray