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.

FRS II will help balance regional water flows

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.

Contruction closure information

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