Mission Trails Flow Regulatory Structure II Project





Trail closure map for trail users
Some trails in Mission Trails Regional Park are closed due to construction activities in the park. Click this map to open an interactive map and view trail closures.

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Hot Off the Press

Construction Begins

The Water Authority is building a new flow regulatory structure to upgrade the untreated water system in the northwest area of Mission Trails Regional Park. When complete, the project will upgrade the untreated water system that delivers water to treatment plants that serve the central and southern areas of San Diego County. 

Standard construction hours are Monday through Friday, 7 a.m. to 7 p.m. with occasional 24-hour and weekend work. As a result, portions of trails in the western portion of the park are closed to public access. Trail closure signs and park maps showing alternate trails are posted to help park users navigate the trails.

Water Authority staff share project and trail closure information with park users
Project outreach staff share project and trail closure information with trail users prior to construction starting.

About This Project

The San Diego County Water Authority maintains regional water pipelines beneath portions of Mission Trails Regional Park in the city of San Diego. The Water Authority is upgrading its untreated water system in the northwest area of the park to more reliably deliver water to treatment plants that serve the central and south sections of San Diego County.

The project currently underway will construct a new 5-million-gallon underground covered reservoir, a flow control facility and pipeline interconnections. The reservoir will be covered with soil and vegetation, except for several access hatches and vents that allow for air movement inside the reservoir.

This work is part of a suite of projects called the Mission Trails Project located in the western portion of the park. In 2010, a new pipeline tunnel, removal of existing blue vent stacks and a new all-weather crossing of the San Diego River was completed. Construction of the flow regulatory structure portion of the project was planned to begin soon after but was delayed by the Water Authority’s Board of Directors in early 2011, citing increasing water rates due to lower water demands.

For more information about the Mission Trails Project, click here.

Current Major Elements Scheduled (March 2020 through Early 2022):

  • Construction of a new underground flow regulatory structure
  • Construction of a new flow control facility
  • North and south connection points

Completed Elements in 2010:

  • Construction of a pipeline tunnel and associated pipeline interconnections
  • Construction of a stabilized river crossing at the San Diego River
  • Demolition of existing above-ground vent stacks in the park

Flow Regulatory Structure II

FRS II Access Structure
Cross-section of the new underground Flow Regulatory Structure II 

A new underground flow regulatory structure, or covered reservoir, is being constructed to help regulate the water system’s flow of untreated water. It will be capable of holding up to five million gallons of untreated water. The facility will be covered with soil and vegetation, with the exception of access hatches and above-ground vents to allow for air movement in and out of the reservoir.


Truck Traffic
Nearby residents will see an increase in construction traffic on Clairemont Mesa Boulevard, Calle de Vida, Portobelo Drive and Antigua Boulevard as well as in and near the western portion of Mission Trails Regional Park. Construction vehicles will use park trails to access work areas. Truck drives will be required to follow appropriate traffic rules as well as weight and speed limits.


School Information

Street Smart School Poster
Street Smart School Poster

Trucks will travel near certain Tierrasanta schools to access the western part of the park. Safety is the Water Authority's first priority, and we want to help keep kids safe. During construction, please talk to your child about street safety. "Street Smart" posters providing street safety tips will be provided to schools near the access routes.


Trail Closures in the Park
Public safety is of the utmost importance during construction. To help keep trail users safe, certain trails in the western portion of the park are closed during construction hours, Monday through Friday, 7 a.m. to 7 p.m. Active construction sites are fenced and at these locations trail access is closed 24 hours a day, seven days a week through the duration of construction. Trail detour and closure signs with a trail map are installed on the trails to help hikers and bicyclists navigate the area. Closed trails will be reopened after construction.

Trail map showing trail closures
Trail Closure Map









Helpful Links
Mission Trails Regional Park - http://mtrp.org
City of San Diego Water Department - http://www.sandiego.gov/water/
Tierrasanta Community Council - http://www.tierrasantacc.org/
San Diego Mountain Biking Association - http://www.sdmba.com/

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FRS II construction begins March 2020
FRS II construction ends Early 2022

*Dates are approximate and subject to change.

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Mission Trails FRS II Location Map
Project location map for FRS II project.

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Trail closure map
Trail closure map.

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Project Presentations:


Information Updates:

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All components of the FRS II project werre fully evaluated for environmental impacts in the Environmental Impact Report for the Mission Trails FRS II, Pipeline Tunnel and Vent Demotion Project (SCH# 2005041025). The reduced FRS II amounts to minor changes that will not result in new impacts nor increase the severity of previously identified impacts. Because these project changes do not constitute "substantial changes... which will require major revisions of the previous EIR," the Water Authority determined that an addendum to the EIR is the appropriate CEQA dcoument to address the project changes pursuant to Section 15162 of the California Government Code (CEQA Guidelines). 

Click here to view the Final Environmental Impact Report and other environmental documents for the Mission Trails Project.


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For more information, please call the 24-hour toll-free project information line at (877) 682-9283, ext. 7004 or email CIPinfo@sdcwa.org. A representative from the project team will return your inquiry within one business day.


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