Appendix A Water Quality Memo - Laserfiche WebLink

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10 Surface Water Quality Objectives Surface water quality objectives establish the limits or levels of water quality constituents to protect beneficial uses. Table A lists surface water quality objectives for all inland surface waters from the Basin Plan that are applicable to Reach 1 of the Sana Ana River. No site-specific numeric water quality objectives were identified in the Basin Plan for Santa Ana River Reach 1, as this reach only contains flood flows. Existing Water Quality Reach 1 of the Santa Ana River is not listed as impaired for any constituents on the 2014/2016 303(d) List. In addition, there are no TMDLs applicable to Reach 1 of the Santa Ana River. Areas of Special Biological Significance Areas of Special Biological Significance (ASBS) are a subset of State water quality protection areas and require special protection as determined by the SWRCB pursuant to the California Ocean Plan. There are no ASBS, as defined by the SWRCB, within or downstream of the Project area (SWRCB 2019). 3.2 Floodplains According to the Federal Emergency Management Agency (FEMA) Flood Insurance Rate Map (FIRM) No. 0659C0144J (2009), the Santa Ana River within the Project area is designated Special Flood Hazard Area Zone A, areas subject to inundation by the 1 percent annual chance flood (100-year flood) with no base flood elevations determined. The remainder of the Project area (outside of the Santa Ana River) is designated as Other Areas of Flood Hazard Zone X, areas with reduced flood risk due to levee. 3.3 Groundwater Hydrology The Project area is above the Coastal Plain of Orange County Groundwater Basin, which underlies the Lower Santa Ana River Watershed. The basin is bounded on the north by the Puente and Chino Hills, on the east by the Santa Ana Mountains, on the south by the San Joaquin Hills, on the southwest by the Pacific Ocean, and on the northwest by low topographic divide at approximately the Orange County-Los Angeles County line (DWR 2004). For regulatory purposes, the Santa Ana RWQCB divides the Coastal Plain of Orange County Groundwater Basin into three Groundwater Management Zones. The Project area is within the Orange County Groundwater Management Zone (Santa Ana RWQCB 1995). The Orange County Groundwater Management Zone is bounded to the north by the Chino Hills, to the east by the Santa Ana Mountains, to the southeast by State Route 55, to the south by the Pacific Ocean, and to the northwest by the Orange County-Los Angeles County line. Recharge to the Coastal Plain or to the Orange County Groundwater Basin occurs from percolation of Santa Ana River flow, infiltration of precipitation, and injection into wells (DWR 2004). A portion of the flow from the Santa Ana River directly below Prado Dam is diverted to recharge groundwater (RWQCB 2004). Based on exploratory boreholes drilled in 2003 and 2004, groundwater levels are 25 to 30 feet below ground surface (Earth Mechanics, Inc. 2018).