SITE INFORMATION AND CORRESPONDENCE

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Bert E. Van Voris • - 11 - 17 September 2004 Supervising Engineer Contrary to the RWD's contention that a 100-year return period"is not typically used as a basis for design,s'1 the RWD must demonstrate that Musco has sufficient storage and disposal capacity to ensure all its processing wastewater is contained onsite(or permitted use areas) during the wettest years (interpreted as a rainfall year with 100-year recurrence frequency). Industrial discharges may reduce production during very wet years as a trade- off to storage structures and still ensure compliance with permit prohibitions against offsite discharge. To ensure that discharge can be conducted without threatening offsite discharge, waste discharge requirements typically set the maximum effluent flow limitation(daily maximum, monthly daily average, or both) based on the design flow values employed in the 100-year water balance. Maximum average daily flows are typically employed in water balances for municipalities and industries with constant production levels (e.g., milk or cheese processors). Some municipalities specify only dry weather flows and provide estimates of anticipated inflow and infiltration flows during wet weather months. Water balances for seasonal industries often employ maximum average daily flows for each specific processing `season.' The project's Water Balances should provide sufficient technical documentation for all assumptions and calculated values, and contain intermediate columns documenting all input values. For example, references used for crop coefficients should be cited and columns representing evaporation losses from and rainfall contributions to the reservoir should be included. Total annual leaching values should also be expressed as million gallons. Leaching losses attributable to the assumed irrigation efficiency of 80 percent should also be included. Proiected Process Flows. In Section 10.1.1,the RWD proposes maximum totalized flow limits of 45 million gallons (MG) monthly and 292 MG annually, and requests that limitations be expressed in terms of maximum monthly and annual limits, not daily maximum volumes. Elsewhere, the RWD indicates, but does not explain,that process wastewater flows may potentially be less than 182 MG annually.12 Comment: Table 2 should separate process wastewater flows from storm water flows to identify the maximum anticipated discharge flow resulting solely from olive processing; storm water flows should be handled separately in the water balance, and be based on assumptions of storm water flows based on rainfall intensity and catchment area. Daily maximum discharge flow limitations will be necessary to ensure wastewater generation flows do not exceed the hydraulic and treatment capacities of wastewater treatment unit processes and operations. The RWD should identify what these capacities will be. The RWD's Table 2, Estimated Process Wastewater Flow, presents maximum, average, and minimum daily flows (in 1,000 gals/day) for each month from January 2003 through April 2004, and includes storm water "falling in the process areas." The RWD's 100-Year Water Balance (Table 15) uses a maximum annual discharge of 182 MG. Values for monthly wastewater flows in Table 15 employ variable design flows ranging from 13 MG (December through January) to 16 MG(August through November). Comment: Discharge flows in the 100-Year Water Balance should reflect Musco's proposed maximum monthly and annual discharge flows of 45 and 292 MG, respectively.