25C - AGMT - OCWD CENTENNIAL PARK

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Section 5 Long Term Surface Water Management As part of the Proposed Project, water quality requirements (MS4 Permit and local ordinances) must be taken into account. To evaluate the Proposed Project from a water quality perspective, the Proposed Project has been divided into off - site improvements and on-site improvements. Off -Site Improvements (Edinger Avenue) The off-site improvements include the installation of a water line within Edinger Avenue. Installation of utility lines (excluding storm drain) within an existing impervious area are considered exempt from storm water treatment requirements as long as the facility (street, parking lot, etc) receiving the utility is returned back to existing line and grade of the original facility and the original purpose of the facility is maintained. For example, if a water line is added to an existing street, it requires removal of the existing pavement and base layers. Once the water line is installed, the street is repaired to the original line and grade and can serve its original purpose. The Proposed Project would include approximately 6,000 square feet of trenching within Edinger Avenue to accommodate the proposed water supply pipeline. The water supply pipeline improvements would not be subject to water quality treatment requirements based on the requirements noted above. On-Site improvements (within Centennial Park) Within Centennial Park, an additional 45,000 square feet of trenching would occur to Install the water line and electrical conduit. In addition, four injection well vaults would be buried within the existing parking lot totaling 2,200 square feet. The surface of the vaults would be returned back to parking lot surfaces at the original line, grade and purpose. However, the vaults would require approximately 12 surface vault hatches totaling approximately 260 square feet which represents a different surface and purpose than the existing parking lot. Therefore, for conservative purposes, the Surfaces would be incorporated into the impervious surfaces that would count towards the Priority Project WQMP category of "significant redevelopment ". The following improvements for the Centennial Park Mid-Basin Injection Well Project are considered impervious surfaces that would count towards the Priority Project WQMP category of "significant redevelopment": • Shared RecreationYCommunication Structure 1 including rooffine and perimeter sidewalk— 1,731 SF • Shared Recreation/Communication Structure 2 including roofline and perimeter sidewalk - 1, 186 SF • Injection Well Vault Hatches in Parking Lots -260 SF Mid Basin Centennial Park A062A6 Project Final EIR 5-129