Appendix A Water Quality Memo - Laserfiche WebLink

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12 Beneficial Uses for Groundwater Basins The existing or potential beneficial uses identified in the Basin Plan for the Orange Groundwater Management Zone are: • MUN: Municipal and Domestic Supply • AGR: Agricultural Supply • IND: Industrial Supply • PROC: Process Water Supply Water Quality Objectives for Groundwater Basins Table B lists the groundwater quality objectives for all groundwater basins from the Basin Plan that are applicable to the Orange Groundwater Management Zone. The site-specific groundwater quality objectives for the Orange Groundwater Management Zone are: • Total Dissolved Solids: 580 milligrams per liter (mg/L) • Nitrate as Nitrogen: 3.4 mg/L Existing Groundwater Quality Water in the Orange Groundwater Management Zone is primarily sodium-calcium bicarbonate-based. Total dissolved solids range from 232 to 661 mg/L and average 475 mg/L. Near the coast, groundwater is impaired from seawater intrusion. Groundwater is impaired by salinity, nitrate, and methyl tert-butyl ether (MTBE) (DWR 2004). 4.0 POTENTIAL IMPACTS TO WATER QUALITY 4.1 Anticipated Changes to the Physical/Chemical Characteristics of the Aquatic Environment Substrate According to the Draft Water Quality Management Plan (WQMP) (Civil Works Engineers 2019b) prepared for the proposed Project, the Project would increase impervious area by approximately 8,500 square feet (approximately 0.2 acre), which would increase runoff to the Santa Ana River. Changes in runoff can affect substrate deposition in the downstream receiving waters. However, because the Santa Ana River is concrete-lined with no substrate, the proposed Project does not have the potential to affect substrate in downstream receiving waters. Current, Circulation, or Drainage Patterns Hydromodification is the alteration of the hydrologic characteristics of water bodies. Increased runoff from increases in impervious areas can alter the volume of water discharged to water bodies that can alter current and circulation patterns. However, the Santa Ana River is a stabilized concrete channel and is not susceptible to hydromodification1 (County of Orange 2012). 1 Hydromodification is the alteration of the hydrologic characteristics of water bodies. Increased stream flows and changes in sediment transport caused by increased impervious areas from urbanization or other land use changes can result in increased stream flows and changes in sediment transport.