Mission Trails Flow Regulatory Structure II Project




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Looking south, toward Cowles Mountain, from within Mission Trails Regional Park. The blue vent stacks, seen in the distance, have since been removed as part of the Mission Trails Project.

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Project design resumes

Design of a new underground reservoir in Mission Trails Regional Park has resumed. The new facility was part of a suite of projects called the Mission Trails Project to be constructed in the western portion of the park. The projects include the new flow regulatory structure, a new pipeline tunnel, removal of existing blue vent stacks, and a new Arizona crossing of the San Diego River. Each component, except the flow regulatory structure, was constructed by late 2010. Construction was delayed by the Water Authority’s Board of Directors in early 2011, who cited increasing water rates due to lowered short-term water demand forecasts as reasons for delaying the project.

While this webpage contains details about this project, more information about the others that composed the Mission Trails Project can be found here.


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 deliver more water to treatment plants that serve the central and south sections of San Diego County.

Major Elements:

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

Completed Elements:

  • 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, will be constructed to help regulate the water system’s flow of untreated water. It will be capable of holding up to 5 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 hte reservoir. Construction is anticipated to begin in early 2020 and last approximately 18 months.



School Information

Street Smart School Poster
Street Smart School Poster

During construction of the pipeline and tunnel portion of the project, Tierrasanta area roads experienced an increase in the number of large construction trucks. The truck activity is expected to be similar when construction of the new flow regulatory structure begins in early 2020.

Construction requires large trucks to travel near certain Tierrasanta schools to access the western part of the park. The major roads that will be used include Clairemont Mesa Boulevard, Santo Road, Via Valarta, Antigua Boulevard, and Portobelo Drive. Truck drivers will be required to follow appropriate traffic rules, as well as weight and speed limits.

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. Please look for these posters at your local Tierrasanta school.


Trail Closures in the Park
When construction of the new flow regulatory structure begins in early 2020, trail safety will continue to be, as it was during the pipeline tunnel project, an important aspect of the project. Also important is maintaining recreational access to trails at the park during construction, whenever possible. To keep trail users safe when construction resumes, certain trails in the western portion of the park will be closed. During construction hours from Monday through Friday, 7 a.m. to 7 p.m., closed trails will be off-limits to recreational access. However, trails will be accessible outside of these construction hours and on Saturdays and Sundays.

Any closed trails will be reopened after construction. 

Helpful Links
Mission Trails Regional Park - http://mtrp.org/index.asp
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 Early 2020
FRS II construction ends Mid 2021

*Dates are approximate and subject to change.

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Mission Trails FRS II Location Map
Project location map for FRS II project. A new trail closure map will be created in advance of construction.

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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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