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Mr. Benjamin Hall. 4 _ 15 October 2o04 Musco Family Olive Company The memorandum presented a simple chloride-based mass balance calculation that determined up to 57 percent of the blanket drain discharge could be composed of impounded wastewater. The report rejects this analysis as too simplistic for the area's complex hydrogeology. The report indicates chloride concentrations in groundwater underlying the discharge site are naturally variable,uses the results of a similar mass balance calculation based on boron to indicate impounded wastewater is not impacting groundwater, and mentions (but does not cite) studies to suggest that chloride is not necessarily conservative under all conditions. The report does not provide specific technical justification on why chloride is not suitable for use as a conservative tracer in this discharge situation or explain why the apparent natural variability in groundwater boron concentrations would not also preclude its use as a conservative tracer. We acknowledge that boron may be suitable for use as a conservative tracer because of its very low potential for retardation/attenuation by soils/aquifer material, and that its use in the mass balance calculation, as presented in the report, yields results that diverge from that obtained by using chloride. However, we were unable to replicate the values presented in the report's Table 1, Summary of Mass Balance Results for Seepage Contributions. Using the mass balance equation[ with the boron data provided in the table for the reservoir, seepage, MW-3, and MW-14,we derived values for the percent of seepage flow composed of wastewater of —78% (based on MW-3) and 27% (based on MW-14). Therefore, based on the boron data, up to 27% of the seepage is composed of impounded wastewater if the quality of groundwater emerging from the seep is similar to that in MW-14 upgradient from the resgrvoir. Conclusion The report states, "we believe that a significant portion of the liquid captured by the blanket drain is of natural groundwater origin." This belief appears to be based on the erroneous values derived in the report for percent wastewater contribution to seepage based on boron mass balance calculations. Even if the belief is correct, it would not preclude waste constituents in the remaining portion of the liquid causing or contributing to degradation of State and federal waters when exiting the dam's blanket drain and passing through downgradient monitoring wells. Absent conclusive evidence that the elevated constituents discharged from the blanket drain are not from or due to the large adjacent waste management unit, Musco is in violation or threatened violation of WDRs Prohibition A.I. The proposed return system must be constructed and placed in operation forthwith. Further, absent sufficient definitive technical information as to the integrity of the waste management unit, either by better geochemical evidence or more complete evidence of the containment features,Musco will continue to be cited as in violation of Task 16. Tracer Dye or Isotope Study Musco asserts without definitive technical documentation that the reservoir construction precludes leachate of waste constituents and decomposition byproducts in quantities that would degrade groundwater and it thereby meets the objective though not the letter of Task 16. By law Musco has the burden of providing conclusive evidence that its waste management units are protective of State waters. It is not sufficient to cast doubt upon other conclusions to the contrary that data can reasonably support. The evidence concerning reservoir construction, hydrogeology, and geochemistry provided by Musco thus far is at best inconclusive as to protection, and it strongly suggests wastewater is not being effectively contained. The use of the reservoir in Musco's proposed long-term strategy does not diminish [B]wastewater * Vwastewater+ [B]groundwater * Vgroundwater= [B]seepage * Vseepage Setting Vseepage= 1 and expressing Vgronndwa a as 1 -Vwastewater yields the following: Vwastewater= ([B]seepage [B]groundwater) / ([Bllwastewater- [131groundwater)