Valeta St. Treatment Ponds

The maintenance of the stormwater treatment ponds near Valeta Street at Famosa Slough was completed March, 2025. The project was funded by the SANDAG EMP Land Management Grant Program to capture & settle Stormwater from 100 acres South of the Slough.

The Famosa Slough Enhancement Plan (FSEP 1993) suggested treatment ponds be added to improve water quality in the Slough, and they were built in 2000. The ponds accumulate water and material from that portion of the watershed. Everything that flows down the roads near Valeta St. and into the stormwater drains is deposited into the treatment ponds. Accumulated material has to be removed and disposed of periodically. The first renovation was done in 2011, and the second will be starting very soon.

Urban runoff contains pollutants including sediments, nutrients, trace elements, oil and grease, and trash and debris. By design, the water is slowed down in the ponds. Many of the pollutants settle as the water slows. Plants in the ponds use the nutrients and bind pollutants to the roots and soil. These pollutants that would have been discharging into the Slough and San Diego River are now passively captured by the ponds.

How we have Helped

Famosa Slough Water Quality Treatment Wetland – Project Background

The Famosa Slough Water Quality Treatment Wetland (also referred to as a Treatment Basin) was constructed through cooperative efforts of the City of San Diego (City) and Friends of Famosa Slough in 1999-2000. The creation of the Treatment Basin involved converting ruderal wetlands to a three chambered storm water treatment wetland system consisting of Pond 1, 2, and 3 with the intent to capture trash and sediment and to improve water quality prior to discharge into the tidal waters of Famosa Slough. The Pond 1 basin is principally a sediment trap prior to water passing northward to Ponds 2 and 3 and ultimately out to Famosa Slough through a series of standpipe drains/weirs and spillways. The pond bottoms were designed to have very flat slopes within an overall gradual drainage to the north. The Treatment Basin (primarily Pond 1) intercepts flows from three large storm drains as well as surface drainage from Valeta Street, Montalvo Street (i.e., swale with inlet drop structure), and the Point Loma Tennis Club (i.e., sheet flow).

The Treatment Basin makes use of managed wetlands to provide water quality treatment benefits.  Thus, these wetlands are designed to be bulrush-dominated (e.g., Schoenoplectus, Bolboschoenus) freshwater/brackish marsh. The marsh provides several treatment benefits. First it slows water flow through ponds and increases turbulence that promotes sediment deposition. Second, it provides a large surface area to support microbial growth that serves as a bio-filter which effectively consumes, decomposes, or transforms many contaminants to less toxic forms. Finally, the marsh plants themselves take-up some of the contaminants binding such materials as metals in complex molecules stored within plant tissues reducing their biological availability until such time as marsh vegetation dies and decays.  The basin slopes were also planted with native riparian associated plants, with the intent to reduce erosion.

Funding for the construction of the Treatment Basin was provided by the City and Friends of Famosa Slough as well as significant grant support from an U.S. Environmental Protection Agency (EPA) Clean Water Act (CWA) Grant managed by the Regional Water Quality Control Board (RWQCB), Region 9, and the U.S. Fish and Wildlife Service (USFWS) Coastal Wetlands Program. Regulatory approvals for the creation of the Treatment Basin were issued by the U.S. Army Corps of Engineers (USACE; Permit No. 95-20072-TCD), RWQCB, and CDFW (CDFW Streambed Alteration Agreement [SAA] #5-189-99). The SAA approved creation as well as maintenance of the Treatment Basin to maintain its function.  Maintenance of the Treatment Basin is guided by the Operations, Maintenance and Monitoring Plan for the Famosa Slough Treatment Wetland (Merkel & Associates, Inc. 2001). Maintenance was most recently implemented though cooperative efforts of Friends of Famosa Slough and the City in February 2011. Appropriate regulatory notifications and/or approvals were issued by the USACE, RWQCB, and CDFW for the maintenance. Specific to the CDFW, the CDFW provided a letter dated January 19, 2011, verifying the continued applicability of SAA #5-189-99 to the maintenance action.