25F - AGMT - DELHI DIVERSION PROJECT

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Preliminary Design Report Addendum No.2 2.0 DIVERSION FACILITY PROCESS DESIGN CRITERIA 2.1 INTRODUCTION This section presents design requirements for the proposed diversion facility. The proposed diversion facility will operate as a preliminary treatment facility for the removal of trash and debris. The diversion facility will be operated based on both dry and wet weather conditions. 2.2 BASIS OF DESIGN FLOWS AND OPERATIONS 2.2.1 Normal Dry- weather Flow Based on the original PDR (July 2012), it is estimated that the dry- weather flow in the Delhi Channel is 0.4 cfs, therefore, an estimated dry- weather flow of 260,000 gallon per day will be collected and treated by the proposed facility. Disposal scenarios of the diverted and treated flows have been developed that analyze the feasibility of using a portion of the diverted flows for irrigation purposes and/or providing for a direct connection to the existing Orange County Sanitation District trunk sewer facilities for further treatment at the regional water reclamation plant. The following discussion provides for an overview of the two alternative scenarios. Two sanitary sewer pumping scenarios have been developed for this analysis that include using the capacity within the existing Costa Mesa Sanitary District Newport Avenue Pump Station, using the proposed pumping facilities associated with the diversion treatment facilities, and making new connections to the Orange County Sanitation District Mainline located along Fairview Road and MarcArther Blvd in the City of Costa Mesa. Dry- weather Flow Diversion Alternative 1 - Alternative 1 is based on providing irrigation supplies to the Newport Beach Golf Club. The Newport Beach golf course has an estimated demand of approximately 200,000 gallon per day in winter months and 292,000 gallon per day in summer months for irrigation; therefore in theory, 77% to 100% of non- stormwater flow collected at the Diversion Facility can be used by the golf course for irrigation purposes. During winter months, excess flow needs to be discharged to the sewer collection system. Operationally, the system would divert flow away from the Santa Ana Delhi Channel and provide for an initial treatment through the gross- solids clarifier chambers and ultimately discharged into the underground storage cisterns. When irrigation demands of the golf course warrant supplemental supply, water stored in the cisterns would be pumped into the existing irrigation system on a daily basis. The remainder of the stored water within the cisterns would then be pumped into the sanitary sewer system for further treatment and disposal by the Sanitation District. Using the existing stormwater flows for irrigation purposes affords an opportunity to use portions of the existing sanitary sewer system owned and operated by the City of Costa Mesa based on specific operational parameters (discussed below). There is an existing Costa Mesa Sanitary District sanitary sewer lift station (Irvine Station) at the intersection of Irvine Boulevard and Mesa Drive which discharges to the Orange County Sewer Trunk Main located at the intersection of Fair Drive and Mesa Drive. The current pumping capacity of the Irvine Station is approximately 300 gallons per minute which discharges into the suction side of the Elden lift station located near the intersection of Santa Ana Avenue and Mesa Drive. The combined system has a total pumping capacity of 300 gallons per minute (gpm), providing for a total of discharge volume of 432,000 gallons in a 24 hour period. Discussions with the Costa Mesa Sanitation District indicated that URS 3 25F -135