Famosa Slough Nutrient TMDL

Introduction

Excessive loading of nutrients into Famosa Slough promotes excessive algae growth and depletes dissolved oxygen levels. These changes limit the ability of this water body to support its beneficial uses designated in the Water Quality Control Plan for the San Diego Basin (9). Famosa Slough was placed on the Clean Water Act (CWA) section 303(d) list of impaired water bodies in 1990 due to eutrophic conditions identified by excessive algal growth. To address the impairment a draft Total Maximum Daily Load (TMDL) has been developed that assesses conditions and identifies a strategy to improve water quality.

Famosa Slough is an estuary located along the San Diego River in the City of San Diego and is one of the only remnants of a historically large wetland that once encompassed the San Diego River floodplain and Mission Bay. This 37-acre wetland, located within a highly urbanized area, provides habitat to shorebirds and wildlife and offers opportunities for environmental education and public recreation.

Water Quality Restoration

The City of San Diego developed a draft TMDL report to address the eutrophic conditions at Famosa Slough.  The TMDL analysis identifies pollutant sources, pollutant loads, load reductions and necessary actions to restore water quality.  The report shows the primary sources of nutrients affecting Famosa Slough come from non-storm water discharges from the surrounding areas and the City of San Diego's storm water conveyance system. 
The plan for water quality restoration is for the City of San Diego to implement focused actions that include nutrient reductions from storm and non-storm water discharges from the surrounding areas into Famosa Slough and algae harvesting when necessary.  The San Diego Water Board's Regional MS4 Permit regulates storm and non-storm water discharges in the San Diego Region.  Development of Water Quality Improvement Plans is a requirement in the Regional MS4 Permit.  The implemented actions and monitoring results will be documented in future revisions to the Water Quality Improvement Plan for the San Diego River.   
The draft TMDL report is the basis for the actions that the City of San Diego plans to implement.  Relying on the existing Regional MS4 Permit will streamline the water quality restoration process without formally adopting a TMDL as a Basin Plan amendment.  This approach identifies Famosa Slough as a high priority waterbody, and ensures resources are dedicated to water quality restoration efforts in a timely manner.  The Famosa Slough and Channel status on the CWA section 303(d) list has been updated to 5-ALT to indicate that an alternative regulatory approach is being implemented to restore water quality rather than adopting a formal TMDL. 

Meetings and Announcements

December 13, 2017: Public Workshop

February 1, 2016 : CEQA Scoping Meeting

Additional Information

A technical report on Famosa Slough was submitted in response to Investigation Order No. R9-2006-076 issued by the San Diego Water Board. Additional information can be found on the Impaired Lagoons web page.

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