Stormwater Engineering Projects

Picture of Pacoima Spreading Grounds

Project Summary

Pacoima Spreading Grounds was built in the 1930s and is one of the major water conservation facilities that provide groundwater recharge for the San Fernando Groundwater Basin. Currently, the spreading grounds' percolation rate is reduced due to a low permeable clay layer underlying the spreading basins. The proposed project will increase the spreading grounds' storage capacity and percolation rate and simplify operations by combining basins and constructing new interbasin structures.

The proposed project will result in increased groundwater recharge in the San Fernando Groundwater Basin. Primary project objectives include:

  • Increasing the percolation rate from 65 to 140 cubic feet per second by removing the underlying clay layers in the spreading basins;
  • Expanding the storage capacity of the spreading basins from 530 to 1,200 acre-feet by combining and deepening the spreading basins;
  • Modifying the intake structure between the channel and the spreading basins to enhance operations;
  • Installing tubular perimeter fencing; and
  • Constructing a new bike path along Pacoima Diversion Channel, between Devonshire Street and Filmore Street to improve neighborhood connectivity.

This project is funded by the State Proposition 84 grant through the Integrated Regional Water Management Plan (IRWMP), the Los Angeles Department of Water and Power, and the Los Angeles County Flood Control District.

Announcements / Construction Updates

Monday, December 20, 2021

  • Hauling operation continues at the Project site, as well as the removal of existing structures.
  • Throughout the duration of the project, continuous air quality monitoring will be conducted. Monthly Air Quality Monitoring Report Summaries can be found in the Resources Section below.

Thursday, September 30, 2021

  • The first Notice to Proceed was issued on May 25, 2021. The contractor completed pre-construction activities (i.e. temporary access road pavement, sound barrier installation, construction fence, and tire wash stations).
  • The second Notice to Proceed was issued on September 21, 2021.
  • The hauling operation is set to begin on Monday, October 4, 2021.
  • Refer to the July 28, 2021 Community Meeting Presentation under the Community Engagement Section for information on the haul routes.
  • Public Works will be conducting air quality monitoring throughout the duration of the of project. The associated reports will be made available in the near future.

Los Angeles County Board of Supervisors adopted the project and its Recirculated Mitigated Negative Declaration on March 9, 2021. Construction of the project is scheduled to begin in August 2021 and last nearly 3 years. Excavated material will be transported to Sunshine Canyon Landfill in Sylmar and Cal-Mat Pit in Sun Valley.

Construction activities will take place from Monday through Friday, between 9 a.m. - 5:30 p.m. Access to residents will not be impacted during construction. Low emission trucks will be used for the transportation of material. LA County will implement measures for noise and dust suppression during construction.

Community Engagement

Past Community Event(s)

Wednesday, July 28, 2021 6:00 PM - 7:30 PM


Construction of the Pacoima Spreading Grounds Basin Enhancement Project is scheduled to begin in August 2021 and last nearly 3 years. The project will enhance stormwater capture for local water supply and include:

  • A new bike path along the Pacoima Diversion Channel, between Devonshire Street and Filmore Street to improve neighborhood connectivity.
  • Installation of tubular perimeter fencing.
  • Reconstruction of the basins to increase water conservation capacity.

During this meeting, we will share an update on the project and construction information as well as answer questions. Spanish translation will be available.




For construction-related questions, please contact

For more information on the project or to be added to the project mailing list, please contact

Updated on: 12/20/2021