The San Diego County Water Authority’s Mission Trails FRS II water project is now more than halfway complete.
The project will upgrade the Water Authority’s untreated water system in Mission Trails Regional Park. When finished in 2022, the upgrades will provide more reliable water delivery to treatment plants that serve the central and south sections of San Diego County.
The Mission Trails Flow Regulatory Structure II Project, or FRS II, will be an underground concrete water tank in Mission Trails Regional Park that will store slightly less than five million gallons of water and be used to balance flows in the aqueduct system. FRS II will be the second underground water tank in the park – both work to efficiently move water through the region. Construction is underway and expected to be completed in 2022.
The Mission Trails Flow Regulatory Structure II Project, or FRS II, will be an underground concrete water tank in Mission Trails Regional Park that will store slightly less than five million gallons of water and be used to balance flows in the aqueduct system. FRS II will be the second underground water tank in the park – both work to efficiently move water through the region. Construction is underway and expected to be completed in 2022.
Improving the region’s water infrastructure ensures that San Diego County residents are getting a clean, safe, and reliable supply. The FRS II project is another example of the successful long-term strategy by the Water Authority and its 24 member agencies to diversify its water resources, make major upgrades in the regional water delivery and storage system, and improve water-use efficiency.
The underground reservoir is being constructed within the park to improve the Water Authority’s untreated water system in the northwest area of the park. The upgrade will increase reliable water delivery to treatment plants that serve the central and south sections of San Diego County.
In 2013, the Water Authority finalized the Regional Water Facilities Optimization and Master Plan Update, the agency’s roadmap for infrastructure investments through 2035. This updated plan focuses on optimizing the Water Authority’s existing infrastructure while maintaining the flexibility to adjust to a range of future water supply needs.
Once complete, the dirt hill will be leveled to its previous contours and revegetated with native plants – many seeded from plants within the park itself. The reservoir will be completely underground – out of sight – but within the control of the San Diego County Water Authority.
“The San Diego County Water Authority is building a massive 5-million-gallon concrete water storage tank, called a flow regulatory structure. You will never see it once it’s completed.” — Joe Little, Reporter, NBC 7, April 9, 2021.
The @SDCWA brought a little of Ancient Rome to #MissionTrails. It’s good for water, but temporarily annoying for hikers. @nbcsandiego at 4:30 and 6:00. pic.twitter.com/s0mud7MGim
— Joe Little🎥🏀 (@LittleJoeTV) April 9, 2021
[Editor’s note: This feature, the Value of Water, focuses on the projects, operations and maintenance by the San Diego County Water Authority and its 24 member agencies that increase the value, reliability, and safety of water for ratepayers in San Diego County.]
San Diego hiking enthusiasts might have to share part of their favorite trail with a cement mixer for the next year. The San Diego County Water Authority is building a massive 5-million-gallon concrete water storage tank, called a flow regulatory structure. You will never see it once it’s completed.
One of the hiking trails in the northwest corner of Mission Trails Regional Park is closed and there are trail detours on other parts.
When looking from the right vantage point towards Mission Trails Regional Park, a brown hill can be seen. This is the San Diego County Water Authority’s Mission Trails Flow Regulatory Structure II Project, or FRS II, under construction. Once complete, the dirt hill will be leveled to its previous contours and revegetated with native plants – many seeded from plants within the park itself.
An underground reservoir is being constructed within the park to improve the Water Authority’s untreated water system in the northwest area of the park. The upgrade will increase reliable water delivery to treatment plants that serve the central and south sections of San Diego County.
From a vantage point on a trail in Mission Trails Regional Park, construction equipment can be seen working on the underground water tank that will help balance regional water flows. Photo: Jim Madaffer
Work efforts on the new FRS II are beginning to take shape with many of the wall sections installed.
The FRS II will be an underground concrete water tank that will store slightly less than five million gallons of water and be used to balance flows in the aqueduct system. FRS II will be the second underground water tank in the park – both work to efficiently move water through the region. Construction is also underway on a new flow control facility, which is part of the project.
Crews captured an aerial view of part of the project site using a drone, which helps to visualize project areas that are not easily accessible. Photo: San Diego County Water Authority
Some trails in the northwest area of the park are closed during FRS II construction hours (Monday through Friday from 7 a.m. to 7 p.m.), with portions closed 24 hours a day, 7 days a week.
The Water Authority created an interactive map showing the location of the closed trails. Visit www.sdcwa.org/mission-trails-FRS to view the map and learn more information about the project. For questions about the project call a toll-free project information line at (877) 682-9283, ext. 7004, or email
