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• • Bert E. Van Voris - 2 - 25 February 2005 Supervising Engineer Comment: The RWD should identify the fixed EC and pH levels at which wastewater is automatically diverted to the Class II surface impoundments. Treatment The addendum describes Musco's proposal to treat high salinity olive processing wastewater using membrane bioreactor/reverse osmosis technology and to discharge the resulting low salinity effluent to Musco's existing 84-million gallon reservoir. The proposal also includes the discharge to the reservoir of lower salinity processing wastewater characterized by a biochemical oxygen demand(BOD) content of about 650 mg/L. Aerators in the reservoir, as well as a long detention time, will reduce the BOD of the commingled discharges to around 50 to 80 mg/L. Musco proposes to design the treatment system to produce a final discharge with levels of inorganic constituents equal to or below that in groundwater underlying the existing disposal site or offsite reclamation areas. The addendum includes a modeling analysis that compares the impact to groundwater of impounded wastewater of various BOD concentrations. The analysis assumes 67 percent of the soluble BOD in the process wastewater is ionized, and suggests the impoundment of wastewater with a BOD content of 650 mg/L will not cause a significantly greater increase in groundwater IDS than impoundment of wastewater with a BOD content of 120 mg/L or 20 mg/L. The addendum concludes that reducing BOD below 650 mg/L prior to discharge to the reservoir is unnecessary. Comment: The addendum does not provide sufficient technical information to explain the model and its use to justify that the impoundment of high BOD wastewater in the reservoir will not adversely impact groundwater. The modeling analysis is inadequately documented, as it does not provide sample calculations or references and/or technical justification for the model's assumptions. The analysis assumes,without justification, that the organic portion of the wastewater consists of two-thirds acetic acid and one-third generic organics, that generic organics in the wastewater are adequately represented by (CHZO)Z, and that insoluble BOD may be neglected. Appendix E shows chemical equations for aerobic and anaerobic conditions,but does not provide the equilibrium constants to properly estimate concentrations of constituents and does not show the calculations used to derive the increase in total alkalinity associated with the degradation of BOD. It does not consider the potential impacts to groundwater resulting from wastewater leaching through sludge accumulations on the reservoir's bottom. Further, it does not appear to consider the carbon dioxide generated through the decomposition of organic waste constituents in the vadose zone and shallow groundwater. Timeline The addendum indicates that Musco still needs to complete the pilot study to obtain design data, complete the design and construction of the wastewater treatment system, negotiate for easements and/or right-of-way access for the reclaimed water conveyance infrastructure, and complete the design, permitting, and construction of the infrastructure required for conveyance of the reclaimed water to offsite properties. Musco anticipates it will take at least 18 months to design and construct the treatment system, at least four months to design the conveyance infrastructure, and at least several months to