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California Water Science Center

Installation of two multiple-well monitoring sites near a proposed supplemental recharge well project, Central Basin, Los Angeles County, Federal Fiscal Year 2016


map of the Central groundwater basin in Los Angeles depicting the site of the monitoring wells

Map showing the location of a planned advanced water treatment facility and three supplemental injection wells (GRIP), in the Central Basin, Los Angeles County, California.

The Water Replenishment District of Southern California (WRD) is planning to construct an advanced water treatment facility and three supplemental injection wells in a recharge area in the coastal plain of Los Angeles County. When the nearby spreading basins are unavailable for recycled water recharge or do not have sufficient capacity to hold local storm water during wet periods, up to 5 million gallons per day of treated water would be directed to the injection wells. There is a short-term need to estimate time of travel to a nearby production well and identify the potential for undesirable trace elements (i.e., arsenic) to mobilize into solution, as well as a long-term need to monitor the quality of injected water in the aquifers.

The study objective is to characterize the geologic, hydrologic, and chemical characteristics of the aquifer system beneath a critical managed aquifer recharge area of the Los Angeles coastal plain, to better inform the design and construction of a supplemental recharge well project.


photo of a USGS Research Drilling rig at the Los Angeles study site

A crew and equipment from the USGS Research Drilling Program will bore to a depth of ~800 feet and install four wells at targeted depths, to construct two multiple-well monitoring sites.

USGS proposes to install two multiple-well monitoring sites (MW1 and MW2), and collect geologic, hydraulic, and water chemistry data needed for the final design and operation of the supplemental recharge well project. Core samples will be collected for the purpose of understanding potential sources of trace elements within the aquifer sediments. Sequence stratigraphic methods will be used to identify sequence boundaries and correlate strata between the monitoring sites. Slug tests will be conducted in each well to estimate the hydraulic properties of the local aquifers. Water samples for the analysis of inorganic constituents, dissolved gases, dissolved organic carbon and optical properties, stable and radiogenic isotopes will be collected to assess the quality of water and characterize the source, movement, and relative age of water between the monitoring sites prior to any injection.

This project will contribute to the USGS' ability to ensure adequate quantity and quality of water to meet human and ecological needs in the face of growing competition among domestic, industrial-commercial, agricultural, and environmental uses. The project aligns with the Water science mission to define and better protect the quality of the Nation's water resources by producing infrastructure and data to better inform the design and construction of a new recharge well project, critical for supplementing existing sources of recharge to the local groundwater basin.


photo of a USGS Research Drilling rig at the Los Angeles study site

Drill rig cuttings organized on the science table at the MW1 site.