If a-single-drop of spring water makes it to the Hansen Dam basin, it becomes part of the Hansen Dam spreading basin aquifer recharge system. Here is how that works, per a 2013 LADWP proposal to inject reclaimed water into the aquifer - the same from where LA gets its drinking water - by the same method. -- empowerla.org/wp-content/uploads/2013/09/LA-Groundwater-Replenishment-Project-Initial-Study.pdf Los Angeles Groundwater Replenishment Project September 2013 Page 1-1 SECTION 1 PROJECT DESCRIPTION 1.1 Overview of the Project To maintain the reliability of the City’s water supply and reduce dependence on imported sources of water, the Los Angeles Department of Water and Power (LADWP) proposes to use up to 30,000 acre-feet per year (AFY) of purified recycled water from the Donald C. Tillman Water Reclamation Plant (DCTWRP) for replenishment of the San Fernando Groundwater Basin (SFB). The Los Angeles Groundwater Replenishment Project (proposed project) consists of: 1) treatment – the construction of new advanced water purification facilities (AWPF) that would perform additional treatment of tertiary effluent (Title 22 treated recycled water) from the existing DCTWRP; 2) conveyance – the use of existing and newly constructed pipelines to transport the purified recycled water from the AWPF to spreading grounds and injection wells; and 3) replenishment – spreading of the purified recycled water at the Hansen Spreading Grounds (HSG) and the Pacoima Spreading Grounds (PSG) for percolation and would include installation of up to 13 new injection wells for direct injection into the SFB to increase groundwater supply by supplementing local potable water supplies. ..... Groundwater recharge into the SFB is primarily achieved through existing spreading grounds in the San Fernando Valley operated by the County of Los Angeles Department of Public Works. The HSG is located in the Sun Valley community of the City of Los Angeles and is bordered by Branford Street to the northwest, Sheldon Street to the southeast, San Fernando Road to the southwest, and Glenoaks Street to the northeast. The PSG is located in the Pacoima community of the City of Los Angeles and is bordered by Arleta Avenue to the northwest, Filmore Street to the southeast, Woodman Avenue to the southwest, and San Jose Street to the northwest. ... The City of Los Angeles has three major sources of groundwater located within the Upper Los Angeles River Area: the SFB, the Sylmar Basin, and the Eagle Rock Basin. The proposed project would replenish groundwater in the SFB. Groundwater recharge into the SFB is currently achieved primarily through existing spreading grounds in the San Fernando Valley. LACDPW owns and operates the HSG and the PSG. They are used, along with the Tujunga, Branford, and Lopez Spreading Grounds, to percolate stormwater into the SFB. The HSG is located along the northwest side of the Tujunga Wash Channel immediately northeast of San Fernando Road. The HSG has 6 shallow spreading basins on 105 wetted acres with an estimated maximum storage volume of 1,420 acre-feet. The facility can receive a total maximum flow of 400 cfs. The average percolation rate is 150 cfs. The sources of water to the HSG are controlled flows from Hansen Dam and Big Tujunga Dam. The HSG is designated as Public Facilities in the City of Los Angeles General Plan. It is located within the Sun Valley-La Tuna Canyon Community Plan area. The zoning designation for the HSG is [Q]PF-1XL (Public Facilities). The Hansen Dam and Hansen Recreation Area are located to the northeast. The HSG is surrounded by open space and light manufacturing uses. The PSG is located on both sides of old Pacoima Wash Channel from Arleta Avenue southwesterly to Woodman Avenue. The PSG has a gross area of 169 acres, of which the spreading basins wetted area occupies 107 acres. It is comprised of 12 shallow basins with a total intake capacity of 600 cfs and a storage volume of 440 acre-feet. The percolation rate is 65 cfs. The PSG receives controlled flows from Pacoima Dam, partially controlled flow from Lopez Flood Control Basin, and uncontrolled flow (storm flow) from East Canyon and Pacoima Wash. The PSG also receives imported water for groundwater replenishment. The PSG is designated as Open Space in the City of Los Angeles General Plan. It is located within the Arleta-Pacoima Community Plan area. The zoning designation for the HSG is OS-1XL-O (Open Space). It abuts Devonwood and Devonshire Arleta Parks and is surrounded by residential uses. Groundwater levels in the area of the SFB vary seasonally and by locality, with the levels along the western sections of the Basin at approximately 50 feet below ground surface (bgs) to between 200 and 500 feet bgs in the eastern portions of the SFB. Groundwater contamination exists throughout the SFB due to improper handling and disposal primarily of solvents widely used since the 1940s. Under a separate initiative, LADWP is studying alternatives for the remediation, containment, removal and cleanup of the contaminants from easterly portions of the SFB where the City’s major well fields are located. ...
Posted on: Wed, 21 Jan 2015 01:18:20 +0000