Orange County Basin - Metropolitan Water District of Southern ...

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Chapter IV – Groundwater Basin Reports Orange County Basins Water Factory 21 was decommissioned in 2004 and is being replaced with the GWR System, which will include 12 new wells and increase the injection capacity to 40 MGD. The GWR System will produce a total of 72,000 AFY of new water supplies. Up to half of the water will be annually injected into the Talbert Barrier. The remaining supplies will be pumped to OCWD’s spreading facilities in Anaheim for recharge in the Forebay area (OCWD, 2004). The GWR System is expected to be constructed and fully on line by September 2007. Table 10-5 Summary of Seawater Intrusion Barriers in the Orange County Basin Seawater Barrier Number of wells Injection capacity (AFY) Talbert Barrier 38 40,000 Alamitos Barrier Project 43 11,000 Source water Recycled Groundwater Imported Recycled Imported Owner OCWD LACDPW OCWD Total 69 53,000 -- -- Direct Groundwater Recharge (AFY) 450,000 400,000 350,000 300,000 250,000 200,000 150,000 100,000 Figure 10-7 Historical Groundwater Recharge in the Orange County Basin 50,000 0 1985/86 1986/87 Injection - Other Injection - Recycled Injection - Imported Spreading - Runoff Spreading - Imported 1987/88 1988/89 1989/90 1990/91 1991/92 1992/93 FINAL IV-10-14 September 2007 1993/94 1994/95 1995/96 1996/97 Fiscal Year Average spreading = 217,200 AFY Average injection = 11,500 AFY 1997/98 1998/99 1999/00 2000/01 2001/02 2002/03 2003/04 2004/05
Chapter IV – Groundwater Basin Reports Orange County Basin The Alamitos Barrier Project consists of 43 wells with a combined injection capacity of 15 cfs and 4 extraction wells in the Alamitos Gap in Long Beach and Seal Beach (DWR, 2005;WRD, 2006d). The barrier straddles the political boundary between the Central and Orange County basins and is operated by LACDPW in cooperation with OCWD and Water Replenishment District of Southern California (WRD). Up to 11,000 AFY could be injected. The barrier utilizes imported water purchased from the City of Long Beach or recycled water from WRD’s Leo J. Vander Lans Advanced Water Treatment Facility. Prior to 2005, recycled water was not injected in the Alamitos Barrier Project. WRD began delivering recycled water for injection in water year 2005/06. Desalters The Irvine Desalter is a joint groundwater quality restoration project by the Irvine Ranch Water District (IRWD), OCWD, MWDOC, Metropolitan, and the United States Navy to employ two water purification plants to address a shallow plume of VOCs that exists beneath the former El Toro Marine Corp Air Station, which is moving toward the Main Orange County Basin. One plant removes TDS and VOCs from the contaminated groundwater and the treated water is used for irrigation and recycled water purposes (OCWD, 2004). The second plant removes TDS and nitrate from the shallow groundwater aquifer outside the former El Toro Marine Corps Air Station plume to provide a new drinking water source (OCWD, 2004). The Tustin Seventeenth Street Desalter is operated to reduce primarily shallow groundwater with high nitrate and TDS levels produced from the Seventeenth Street Wells Nos. 2, 4 and Tustin’s Newport Well. The treated water is blended back with produced native water producing up to 3,000 AFY of potable water (OCWD, 2004). GROUNDWATER LEVELS Historically, groundwater flow in the Orange County Basin has been from the recharge areas in the north toward the Pacific Ocean. As shown in Figure 10-8, in November 2005, Orange County Basin water levels ranged from a high of about 300 feet above mean sea level (MSL) in the north portion of the basin upgradient of the spreading grounds to a low of about 80 feet below MSL in the coastal areas. Historical water levels in key wells in various locations in the basin are summarized in Figures 10-9 and 10-10. The locations of the wells plotted are shown in Figure 10-1. These data show that water levels in the Forebay area where the aquifers are merged generally experience higher water levels and are relatively stable with annual variations on the order of 50 feet. In the Pressure area, water levels in the underlying aquifers are generally below sea level. Water levels generally correlate with the change in storage discussed above. Seasonal variations in water level in the Pressure area are as much as 100 feet. Water levels in the key well in south-central pressure area decreased up to 70 feet between 1985 and 2004. Water levels in other key wells are essentially unchanged in this same period. Land subsidence due to groundwater withdrawal is common in groundwater basins. Slight subsidence has been observed in Santa Ana, which may be due to groundwater withdrawal, and FINAL IV-10-15 September 2007
Page 1 and 2: Chapter IV - Groundwater Basin Repo
Page 7 and 8: GROUNDWATER MANAGEMENT Chapter IV -
Page 9 and 10: BPP (%) 85% 80% 75% 70% 65% 60% Cha
Page 11 and 12: Category Non-Irrigation Wells (larg
Page 13: Chapter IV - Groundwater Basin Repo
Page 17 and 18: Water Level (feet MSL) 200 150 100
Page 19 and 20: TDS Chapter IV - Groundwater Basin
Page 23 and 24: Groundwater Treatment Chapter IV -
Page 25 and 26: In-lieu Storage (AFY) 90,000 80,000

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