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Section 5 <br />5.8 HYDROLOGY[WATER QUALITY <br />This section provides a discussion of the hydrological conditions and water <br />quality conditions within the project area and potential hydrology and water <br />quality impacts associated with construction and operation of the Mid Basin <br />Centennial Park Injection Well Project, The analysis includes a Phase 1 <br />Environmental Site Assessment prepared by EEI Geotechnical and <br />Environmental Solutions in May of 2015 and a Travel Time and Mounding <br />Analysis prepared by the Orange County Water District in June of 2015. The <br />Travel Time Analysis and the Mounding Analysis is presented in Appendix F. and <br />the Phase 1 Environmental Site Assessment is presented in Appendix F1 <br />5.8.1 Affected Environment <br />The project site is located within the lower Santa Aria River Watershed. The <br />Santa Ana Watershed is the largest watershed in coastal Southern California, <br />consisting of over 2,800 square miles and encompassing parts of Riverside, San <br />Bernardino and Orange Counties, Surface water bodies within the vicinity project <br />area include the Santa Ana River, Greenville Banning Flood Control Channel and <br />Centennial Lake. The project site also overlies the Orange County Groundwater <br />Basin. <br />Santa Ana River <br />The Santa Ana River is the most prominent hydrologic feature within the Santa <br />Ana River Watershed. The Santa Ana River is over 100 miles in length and has <br />over 50 tributaries. The headwaters for the Santa Ana River are in the San <br />Bernardino Mountains to the northeast.. The river extends westerly through the <br />Santa Ana Valley to the Prado Basin where it is joined by several tributaries near <br />Prado Darn. Downstream of Prado Dam, the Santa Ana River flows through the <br />Santa Ana Mountain Canyon into Orange County before discharging into the <br />Pacific Ocean. The flows of the Santa Aria River consist of storm flows and <br />perennial flow (base flow) that increases in the winter and decreases in the <br />summer. The base flow of the Santa Ana River consists primarily of treated <br />wastewater discharged from upstream waste water treatment plants. Since 1933, <br />OCWD has been managing the Orange County Groundwater Basin. The primary <br />source to replenish the groundwater basin is surface water flows from the Santa <br />Ana River. The surface water flows are diverted into a series of recharge basins <br />that are maintained by OCWD. Virtually all of the base flow of the Santa Ana <br />River is captured by OCWD for groundwater recharge and a portion of the total <br />storm flow of the Santa Ana River is captured by OCWD for groundwater <br />recharge. The volume of groundwater recharge from storm flows is a function of <br />precipitation intensity, duration, impervious area arid distribution of sterns over a <br />Mid Basin Centennial Park 2962446 Project Final EIR 5-98 <br />