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Water Quality Management Plan (WQMP) <br />Mainplace Mall Specific Plan <br />River Watershed and others drain to the Newport Bay and Anaheim Bay - <br />Huntington Harbor watersheds. A portion of MainPlace Mall is tributary to <br />Santiago Creek (County drain E08), which lies south of the south leg of <br />Mainplace Drive along the Project frontage. Santiago Creek discharges to the <br />Santa Ana River (County drain E01) about one mile west of the Mall. The Santa <br />Ana River drains south to the Pacific Ocean. Approximately 24.7 acres of the <br />site drains to Santiago Creek. See drainage areas C, D, and E on the Existing <br />Hydrology Map m Attachment H. <br />The majority of the Site drains to the Caltrans drainage system associated with <br />the Interstate 5/State Route 22 interchange. The Caltrans drainage system <br />discharges directly to the Santa Ana River (County drain E01) at the <br />interchange. The Santa Ana River drains south to the Pacific Ocean. <br />The Mall lies within Zone X, which is outside the 100-year floodplain. Zone X <br />is achieved in this area through the presence of levees alongside Santiago <br />Creek. A small portion of the south edge of the south leg of Mainplace Drive <br />lies within Zone AE, but the Zone AE designation does not extend to the Mall <br />site. Both Santa Ana River Reach 1 and Santiago Creek are on the State's 303(d) <br />list of impaired water bodies. Both watercourses have category 2 impairments; <br />they can support some, but not all of, their State -defined beneficial uses. Santa <br />Ana River Reach 1 has a fecal coliform impairment and Santiago Creek has an E <br />Coli impairment. Neither watercourse has a Total Maximum Daily Load <br />(TMDL) defined. <br />In the existing condition, the site consists of an approximately 1,130,000 square <br />foot building and three multilevel parking structures. The site is paved and <br />mostly drains to the west. <br />The City has confirmed that any connections to the City system will require <br />City review only. Caltrans and County review of site drainage will not be <br />required as long as site drainage connects directly to City infrastructure. <br />The site is served by an existing storm drain system discharging to five <br />different locations. On site drains range in size form 12" to 30" diameter. <br />Approximately 10.2 acers of the North-east portion of the site drains to a 36' <br />existing storm drain in Main Street at the intersection of Town and Country <br />Road and Main Street. The existing easterly parking structure, approximately <br />4.6 acers, drains to the existing 36' storm drain line in Main Street. These areas, <br />totaling approximately 14.8 acres, are tributary to Santiago Creek. <br />Centennial Section II <br />Conceptual Specific Plan WQMP Page 4 <br />