Famosa Slough Eutrophication Monitoring and Algae Removal Project

Famosa Slough Eutrophication Monitoring and Algae Removal Project

The proposed Famosa Slough Eutrophication Monitoring and Algae Removal Project involves the recurring inspection and maintenance of the southern central basin of Famosa Slough, an impaired water body on the Clean Water Act Section 303(d) list for eutrophication, which has been caused by excessive nutrients (total nitrogen and total phosphorus). The City has been directed by the San Diego Regional Water Quality Control to develop and implement a Total Maximum Daily Load Alternative to address eutrophication in the Famosa Slough. One of the activities the City is required to conduct to address eutrophication in the Slough is to remove floating algal mats from the southern central basin portion of the Slough to improve water quality and enhance wetland habitat. DESCRIPTION OF-NATURE AND PURPOSE OF THE PROJECT: The proposed Famosa Slough Eutrophication Monitoring and Algae Removal Project will allow for the removal of eutrophic algae blooms m the southern central basin (basin) of Famosa Slough caused by excessive nutrient loading from urban runoff and trash/debris which will reduce negative impacts to water quality, and biological and recreational resources In the Slough area. Eutrophication or hypertroph1cat1on Is when a body of water becomes overly enriched with minerals and nutrients which induce excessive growth of algae. The Famosa Slough and Channel are hydrologically affected by three d1st1nct systems. The tidal circulation of seawater Is the primary parameter which created and maintains the coastal wetland ecosystem. Runoff from the local watershed and freshwater flow from the San Diego River Flood Control Channel are the other two sources which provide various amounts of input on a seasonal basis. Famosa Slough Is on the Clean Water Action Section 303(d) 11st of water quality l1m1ted segments for eutrophication, with nutrients as the pollutant category (State Water Resources Control Board, 2024), and the 2024 California Integrated Water Quality Report and 303(d) List. The proposed Project involves the recurring Inspection and maintenance of an 1mpa1red water body on the Clean Water Act Section 303(d) list for eutroph1catlon, which has been caused by excessive nutrients (total nitrogen and total phosphorus). The City has been directed by the San Diego Regional Water Quality Control (San Diego Water Board) to develop and implement a total maximum daily load (TMDL) alternative to address eutroph1cat1on m the Famosa Slough. One of the act1v1t1es the City 1s required to conduct to address eutroph1cat1on 1n the Slough 1s to remove floating algal mats from the southern central basin portion of the Slough under specific circumstances. Under the Alternative TMDL, algal mat removal would be required 1f algae within the basin reaches the combined regulatory action triggers of 50 percent or greater cover and a measured algal biomass of 80 grams per square meter. Algal monitoring 1s conducted at the locations and frequency described In the Famosa Slough Eutrophication Monitoring Plan and Quality Assurance Project Plan (QAPP) (City 2023), The proposed Project does not involve permanent development. All work would be performed and/or overseen by the City Stormwater Department staff. Algae removal regulatory action triggers are most likely to be met during the summer months when algal cover 1s greatest. If algal removal 1s required, a crew of two to four City staff and a qualified biologist will remove algae by skimming algae mats from the surface of the water. Hand tools will be used to perform this work; no mechanized equipment will be used to remove the algae from the Slough waterbody. Staff will work from the open water, wearing waders, to remove excess algae mats by hand with one or more of the following: rakes, nets, kayaks, canoes, and/or stand-up paddleboards. All work will be conducted by City staff and pre algae removal and removal act1V1t1es will be monitored by a qualified biologist. Smee algal mats are floating, algal removal will not require excavation or soil disturbance. No other vegetation will be removed or Indirectly Impacted as part of the Project. The Project will not include permanent development or mod1flcat1ons within the Slough. Algae removal will occur as needed to maintain the algal biomass and percent cover below the required thresholds as established by the QAPP. No Grading would occur in the Slough or surrounding v1cm1ty. Access to the basin will be provided via an existing City Park and Recreation maintained hard-packed access trail that leads from Famosa Boulevard to a disturbed and unvegetated area adjacent to the basin. The unvegetated area 1s roped off from the surrounding vegetation and will be used as the landing and staging area for the Project. Once removed, algae would be brought to the staging area onshore and manually placed within a temporary containment basin to allow the algae to dry out. Once dry, City crews will use a Vactor Truck to remove the algae from the temporary containment. The Vactor Truck will be parked on Famosa Boulevard and has a vacuum boom long enough to reach the staging area without disturbing existing vegetation. It Is anticipated that the Vactor Truck will be able to vacuum out the algae from the temporary containment In approximately 5 to 10 minutes. Algae will be disposed at a landfill. The Project does not involve any permanent development or associated construction and would not negatively Impact storm water flow; as such, the Project would not require the preparation or use of construction storm water Best Management Practices (BMPs) or a Storm Water Quality Management Plan. Conversely, the Project would serve as a BMP by Improving water quality m the Famosa Slough. Therefore, 1t Is not necessary to develop a Storm Water Pollution Prevention Plan or Water Pollution Control Plan. The proposed Project does not have the potential to Impact potentially significant cultural resources because: 1) no grading or landform modification would occur on upland landforms that have the potential to have supported preh1stonc occupation. The proposed Project staging area was previously disturbed and would not be modified further; 2) proposed algae removal would be undertaken with hand tools such that no mechanical equipment would be placed on upland landforms where the potential for prehistoric occupation 1s greatest; 3) proposed algae transport from staging area to the Vactor Truck parked on Famosa Boulevard would be undertaken by extending a vacuum boom from the City's Right-of-Way to the staging area. Famosa Boulevard 1s situated approximately 5-1 0 feet above the staging area and the Vactor Truck's vacuum boom can extend above the ground surface and existing vegetation to reach the temporary containment basin, such that there Is no mechanical equipment placed on upland landforms where the potential for preh1stonc occupation Is greatest; and 4) the removed algae material would be placed within a temporary containment basin In the previously graded staging areas, and then transported to a licensed landfill or solid waste facility for disposal, such that there would be no potential for unknown archaeological resources to be indirectly Impacted by placement of the organic materials.

San Diego

San Diego

Citywide

San Diego