SITE INFORMATION AND CORRESPONDENCE

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Bert E. Van Voris - 3 - 25 February 2005 Supervising Engineer obtain infrastructure permits. Musco anticipates initiation of treatment within approximately 24 months following issuance of tentative waste discharge requirements (WDRs). Musco intends to significantly decrease volumes applied onsite and initiate offsite discharge as soon as the treatment system is operational,the conveyance infrastructure is complete, and offsite use areas become available. The addendum indicates a three-to five-year timeframe may be necessary to identify and negotiate agreements with owners of additional potential use areas to obtain agreements for the acreage necessary to discharge all of the effluent offsite. The addendum states, "Musco intends to shift as much of the reclaimed water as possible to offsite agricultural irrigation use within the first year following implementation of treatment. Therefore the mass loading to the land application areas is expected to be limited."' Reservoir Impacts The addendum states that the construction and use of the reservoir was approved by the Regional Board and by San Joaquin County. It indicates that use of the reservoir as a treatment reactor is "critical to the continued operation of Musco's Tracy facility."Z The addendum states that the 17 September 2004 Regional Board letter and 28 April 2004 Notice of Violation (a) does not provide definitive evidence that water from Musco's process wastewater storage reservoir is impacting groundwater and(b) simply assumes the changes in MW-16 are attributable to impacts from the reservoir. The addendum states the increases could be due to the rising groundwater and subsequent dissolution of formation materials that have recently come into contact with the rising groundwater. The addendum states that,based on the results of the Background Groundwater Quality Report, the "organic constituents are not directly impacting the groundwater underlying the site from the storage reservoir and ...impounded water stored in the reservoir is unlikely to dissolve significant amounts of inorganic solids in the formation material underlying the site."3 The addendum also states, "aeration in the reservoir not only reduces the BOD of the wastewater(typically to below 100 mg/L), it also strips much of the carbon dioxide formed during biodegradation, resulting in water that is relatively non- aggressive to the aquifer formation materials."4 To demonstrate the reservoir's lack of impact on groundwater, the addendum compares the impounded wastewater characteristics with those in MW-16,which was installed downgradient from the reservoir just prior to impoundment of process wastewater. The addendum states, "Patterns of constituent concentration change observed in groundwater samples collected from monitoring well MW-16 are not consistent with those anticipated from direct mixing of impounded wastewater with the native groundwater.s5 The addendum cites nitrogen and sulfate as examples. With respect to nitrogen, the addendum indicates that nitrogen present in impounded wastewater is not present in MW-16. Comments: The addendum's statement that the Regional Board approved reservoir construction and use is misleading. The Regional Board authorized Musco to impound Pages 1-3 to 1-4 2 Page 5-1 'Page 1-2 4 Page 5-2 5 Page 5-2