Los Angeles Sanitation and the Los Angeles Department of Water and Power are committed to a sustainable water future that relies more on local water supplies than costly and unreliable purchased imported water. The plan to increase local water resources includes groundwater replenishment using purified recycled water (purified water). The Los Angeles Groundwater Replenishment (GWR) Project is an important infrastructure investment that will help develop a local, safe and reliable water supply for a sustainable Los Angeles.

The Los Angeles Groundwater Replenishment (GWR) Project will provide up to 9.78 billion gallons (30,000 acre- feet) of purified water, per year, from the Donald C. Tillman Water Reclamation Plant in Van Nuys to the Hansen and Pacoima Spreading Grounds in the eastern San Fernando Valley. The water will be infiltrated into the groundwater basin where it can eventually be pumped and supplied to homes for drinking and non-drinking uses. This project will provide enough water to supply 90,000 single family homes in Los Angeles per year.

The GWR Project supports the Mayor’s goals to be more drought-resilient and less dependent on purchased imported water. The goals are also consistent with LADWP’s 2010 Urban Water Management Plan that includes efforts to increase the supply of recycled water in Los Angeles to 19.2 billion gallons of water (59,000 acre- feet) by 2035.

Groundwater Replenishment: How it’s done

Hansen Spreading Grounds in the eastern San Fernando Valley



One acre-foot is 326,000 gallons of water and is enough to serve three single family homes in L.A. for one year.

Groundwater replenishment is the process of refilling and recharging groundwater aquifers with a water source that can eventually be pumped and supplied to homes for drinking.

Spreading grounds can be likened to football field-sized bowls with layers of natural permeable materials that allow water to percolate underground to reach natural aquifers, or groundwater basins, that serve as large-capacity storage. Currently, the San Fernando Groundwater Basin
is replenished primarily by stormwater. The GWR Project will augment stormwater capture with purified water for infiltration.

The City has four water reclamation plants that collectively receive up to 350 million gallons of water per day (or 392,000 acre-feet per year). Approximately 75,000 acre-feet of this water is currently used for non-drinking uses such as irrigation, commercial and industrial uses, seawater intrusion injection, and environmental benefits such as maintaining Lake Balboa, Wildlife Lake and the Japanese Garden in Van Nuys. The City is aggressively pursuing projects, including the GWR Project, to optimize the use of recycled water in the City.

Donald C. Tillman Water Reclamation Plant Improvements

The GWR Project will include the construction of advanced water purification facilities at Donald C. Tillman Water Reclamation Plant to treat the recycled water and half a mile of 24-inch pipeline for brine discharge.

Currently, recycled water for non-drinking uses is produced through a multi-step process that includes breaking down debris and organic matter as well as chlorine disinfection. This process ensures the recycled water meets regulations for irrigation as well as for commercial/industrial and environmental uses

[refer to above image].

In order to comply with State Groundwater Regulations for recharging the spreading grounds with recycled water under the GWR Project, water from the Donald C. Tillman Water Reclamation Plant will be further purified using advanced treatment processes. LA Sanitation is currently pilot testing the advanced treated recycled water processes to determine the best way to purify water for this project. The City is currently considering several processes including ozonation, biologically activated carbon, microfiltration, reverse osmosis and advanced oxidation. At the conclusion of the pilot, the City will determine the treatment methods that will meet all groundwater recharge regulations while optimizing project cost.

Conveying Recycled Water to the Spreading Grounds

Once purified, the water will be conveyed via an existing 10-mile, 54-inch diameter recycled water pipeline to
the Hansen Spreading Grounds. LADWP will build a new recycled water pipeline to convey the water to the Pacoima Spreading Grounds. This new pipeline will be approximately two miles in length and 42-inches in diameter and will begin on Branford Street, run along Arleta Avenue, and connect the existing 54-inch line to the Pacoima Spreading Grounds.


The project will cost approximately $450 million with an annual operational and maintenance cost of $22 million.
LADWP and LA Sanitation will pursue local, state and federal funding sources for this project.

For more information: www.ladwp.com/GWR

The water will percolate and replenish the groundwater at both locations and remain as part of our natural underground reserves for several years prior to pumping and distribution. Construction at the spreading grounds will also include new outlet structures as well as other modifications.


Trash and grit screened out


Solids settle to bottom or float to the top


AWPF Treatment Process

Beneficial microbes feed on solids & organic matter


Future Advanced Purification Options include:

Reverse Osmosis Ozone

Advanced Oxidation Process

Spreading grounds

Existing Treatment at Donald C. Tillman Water Reclamation Plant for Non-Potable Reuse


Draft environmental impact report (EIR): Spring 2016 Final EIR: Fall 2016
Pilot testing and project development: 2016-2019 Construction: 2019-2022

Testing: 2022 (6 months)
Spreading operations commence: mid-2023