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Provided below is a brief description of the proposed drainage,water,wastewater, and roadway systems. See Sections 4.5,4.7, and 4.11 of this Draft EIR("Public Utilities,""Drainage,"and"Transportation,"respectively) _ for further descriptions and analysis. See also the College Park at Mountain House Specific Plan III document that is on file at the SJCCDD. 3.10.1 DRAINAGE The proposed storm drain system(Figure 3-12)would be consistent with that envisioned in the MHMP and detailed in the current Mountain House Drainage Master Plan. Storm drains would collect runoff from the MHMP area,including the College Park site, and discharge this runoff to Mountain House Creek and Old River. The MHCIP,which has recently been completed and will increase the capacity of Mountain House Creek through creek bed and bank improvements that were needed to accommodate runoff from,ievelopment of portions of Mountain House, including College Park. Until the MHCIP is completed,on-site detention of runoff within the western portion of College Park would be required.Detention basins would offer a means of limiting the peak developed runoff flow rate to the level of the peak runoff flow rate assumed for the College Park site in the current Mountain House Drainage Master Plan. _ This peak runoff flow rate is what existing downstream drainage facilities have been planned to accommodate. Therefore,with on-site detention,if required,development within the College Park project could proceed without increasing the existing downstream peak runoff flow rate. It is anticipated that an interim on-site detention basin would be required, and thus one has been proposed in the southern portion of the College Park site between Central Parkway and I-205 on GNK,LLC property(Figure 3-2). Other properties that develop in the College Park area(i.e.,the Pegasus property and Delta College)could — also be required to provide detention on an interim basis until such time as adequate downstream facilities are constructed. The Delta College EIR already identifies a mitigation measure to detain stormwater runoff on an interim basis,if necessary. Should the peak flow from the College Park area under the proposed project exceed the maximum flow rate assumed for the College Park site in the MHC1P,permanent detention basins or other measures would be implemented to limit peak runoff to the capacity of the downstream drainage system and Mountain House Creek under the MHCIP. — Trunk storm drain lines have been recently constructed to just south of Mascot Boulevard, in both Central Parkway and DeAnza Boulevard, associated with Specific Plan I Neighborhood E.Under the proposed College _ Park project,these trunk lines would be extended southward in Central Parkway and DeAnza Boulevard to the College Park site as shown in Figure 3-12. The western portion of the College Park site would be served by the Central Parkway stormwater system. The Central Parkway system would convey stormwater runoff currently entering the College Park site from south of I-205 through the project site and north in storm drains in Central Parkway to Mountain House Creek. The eastern portion of the College Park site would be served by the DeAnza stormwater system.The storm drain in DeAnza Boulevard would convey project(urban)runoff to existing Water Quality Basin No. 1 (WQBI)located near Byron Road and Central Parkway(Figure 3-12)and then discharge to the improved Mountain House Creek and then to Old River.WQB 1 would be expanded,as necessary,to accommodate the runoff from College Park. A new on-site stormwater-quality basin(Figure 3-12)would be developed at the southwest comer of Grant Line _ Road and Central Parkway as part of the Central Parkway system for Neighborhood A,through which project runoff would flow before being discharged to the system and eventually to Mountain House Creek. Such a basin would not be required for Neighborhood B because project runoff would be processed through the existing WQBl.As indicated in Figure 3-12,WQBI along Byron Road would be expanded as necessary to accommodate EDAW College Park at Mountain House Speck Plan III Draft EIR Project Description 3-32 San Joaquin County