25F - AGMT - DELHI DIVERSION PROJECT

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iD.2 Development at a Regional Trash Rerrloval System The Draft Staff Report for Proposed Trash Amendments to the MS4 permit requirements will requite a significant increase in non -point source trash and debris mitigation requirements. The proposed trash amendments identify several potential trash capture solutions inclusive of storm -water catch -basin modifications (filter inserts) and enhanced routine street sweeping maintenance. The proposed amendments also recognize that modifications to an existing MS4 closed conduit drainage system will have potential capacity impacts and, therefore, may not be feasible. As such, the proposed trash amendments also provide the ability to develop a regional treatment facility as described in "Section 5- Reasonably Foreseeable Methods of Compliance ", as published in the above reference, providing for a full capture system and has the ability to remove gross solids larger than 5mm in diameter. Although, the draft proposed trash amendments don't specifically identify a stormwater flow rate associated with the proposed treatment process, URS is making the basic assumption that the current storm water quality flow rate event (approximately the 85th percentile) will be the target flow rate to be passed through the trash removal system during normal operations. The project stakeholders, Cities of Santa Ana, Costa Mesa and Newport Beach, are essentially located in fully developed watersheds with little or no planned future land use changes. All three stakeholders have implemented stotmwatef quality mitigation measures that address gross solids removal at catch basins and other storm drainage inlets. Although, the implemented mitigation measures did provide some success in the reduction of trash and debris entering into the MS4 systems, the mitigations also proved to reduce storm drain capacities and posed potential public safety issues during storm events due to local street flooding. Based on the potential public safety issues and labor intensive maintenance associated with catch basin inlet treatment systems, the project stakeholders are interested and willing to implement a regional treatment system that not only addresses the potential trash amendments, but also has the ability to remove other pollutants of concern and therefore provide for a multi - beneficial project. tD.3 Proposer Project Description The proposed Santa Ana Delhi Diversion project is to be located between Irvine Avenue and Santa Ana Avenue adjacent to the Santa Ana Delhi Channel within the Newport Beach Golf Course. The Santa Ana Delhi Diversion project is intended to capture and divert dry - weather urban water runoff to the sanitary sewer system addressing urban surface water quality, capture trash and debris being transported within the channel drainage system and provide measurable water quality improvements in the downstream receiving waters, primarily in Newport Back Bay. The use of an in- channel trash removal system will enhance the overall treatment process which will be compliant with the proposed MS4 Amendments and address other future TMDL including waste load allocations for MS4 Dischargers into the Upper Newport Bay through the Santa Ana Delhi Channel and its sub - tributaries. The proposed treatment system will remove target pollutants of concern that that either currently include or will include bacteria, metals, nutrients in addition to the trash and debris from the Santa Ana Delhi tributary watershed. URS, through the collaborative efforts of the project stakeholders, have prepared and evaluated a number of design alternatives since the inception of the project, developing several preliminary design reports (PDR) documenting the various alternatives have been prepared. The various iterations and features of each alternative are summarized as follows: 25F -932