2019-113 - Mainplace Mall Mixed-Use Project

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City of Santa Ana MainPlace Mall Transformation Water Supply Assessment as a result of the benefit provided to the OC Basin by removing poor -quality groundwater and treating it for beneficial use. Annual groundwater basin overdraft, as defined in OCWD's Act, is the quantity by which production of groundwater supplies exceeds natural replenishment of groundwater supplies during a water year. This difference between extraction and replenishment can be estimated by determining the change in volume of groundwater in storage that would have occurred had supplemental water not been used for any groundwater recharge purpose, including seawater intrusion protection, advanced water reclamation, and the in -Lieu Program. The annual analysis of basin storage change and accumulated overdraft for water year 2013-14 has been completed. Based on the three -layer methodology, an accumulated overdraft of 342,000 AF was calculated for the water year ending June 30, 2014. The accumulated overdraft for the water year ending June 30, 2013 was 242,000 AF, which was also calculated using the three -layer storage method. Therefore, an annual decrease of 100,000 AF in stored groundwater was calculated as the difference between the June 2013 and June 2014 accumulated overdrafts. Several groundwater replenishment mechanisms are used in the OC Basin. Active recharge of groundwater began in 1949, in response to increasing drawdown of the OC Basin and consequently the threat of seawater intrusion. Section 3.3.3 of the UWMP outlines various groundwater recharge facilities. Section 3.3.4 of the UWMP describes an MWD program whereby MWD sells additional water to OCWD when excess surface water is available. This reduces the OC Basin pumping requirements. Section 3.3.5 of the UWMP describes an agreement for MWD to store its water in the OC Basin up to 66,000 AF. 4.4 Reliability of Water Sources Water supply reliability includes the pumped groundwater from the OC Basin, the availability of water purchased through MWD and the equipment that makes up the City's distribution system. Both City's potable water sources (OC Basin and MWD) are considered to be of high quality and reliable.° The OC Basin, the City's primary water source, is an actively, managed water source with significant recharge infrastructure and conservation programs in place. The City's secondary, alternative source is MWD. MWD's 2015 UWMP finds that MWD is able to meet, full -service demands of its member agencies starting 2020 through 2040 during normal years, single dry year, and multiple dry years. MWD's 2015 Integrated Water Resources Plan update describes the core water resources that will be used to meet full -service demands at the retail level under all foreseeable hydrologic conditions from 2020 through 2040. The foundation of MWD's resource strategy for achieving regional water supply reliability has been to develop and implement water resources programs and activities through its Integrated Water Resources Plan preferred resource mix. This preferred resource mix includes ° Water Code §10910(f)(5) KimleyoHorn 55C-23 Page 115