San Diego Region - Loma Alta Slough TMDL Phosphorus

The San Diego Water Board adopted Resolution No. R9-2014-0020 to reduce eutrophic conditions and restore Loma Alta Slough on June 26, 2014. The TMDL investigation indicated that non-storm water discharges from the local watershed and the storm water conveyance system are the primary sources of phosphorus. The Regional MS4 Permit regulates storm and non-storm water discharges. The necessary actions to reduce phosphorus loading and restore beneficial uses can be tracked through reporting requirements of the Regional MS4 Permit. Therefore, this alternative restoration plan to use the existing permit was implemented instead of adopting the TMDL as a Basin Plan amendment.

Adopted Resolution and TMDL Report

The following documents are available for review at the San Diego Water Board Office. To request a file review please contact the Regional Board receptionist at (619) 516-1990, or email rb9_records@waterboards.ca.gov.

Questions and comments regarding the Loma Alta Slough Phosphorus TMDL Project may be directed to Ms. Jody Ebsen at 619-521-3965, or by email at Jody.Ebsen@waterboards.ca.gov

  • Resolution No. R9-2014-0020
  • Phosphorus TMDL Report
  • Appendix 1 - Modeling Report

Background

Excessive eutrophic conditions within the Loma Alta Slough (Slough) restrict the ability of its water to support the beneficial uses designated in the Water Quality Control Plan for the San Diego Basin (9). As a result, the Slough was placed on the 1996 Clean Water Act section 303(d) list (CWA 303(d) list) of impaired water bodies. Eutrophication is caused by excessive nutrients (phosphorus and nitrogen) in waterbodies that stimulate excessive plant and algae growth. This intense growth depletes oxygen and can lead to stresses on aquatic life and impairment of beneficial uses. The impairment is limited to the summer-dry weather season when natural and anthropogenic activity restricts the mixing of freshwater and saltwater/ocean water, non-storm water and illicit discharges adds nutrients to the Slough, and weather conditions foster excessive algal growth. The primary pollutant driver for the eutrophic conditions in the Slough is phosphorus. Sources of phosphorus into the Slough include non-storm water discharges and groundwater.

An investigation was carried out in accordance with the Clean Water Act section 303(d) and State Water Board Resolution 2005-0050, “Water Quality Control Policy for Addressing Impaired Waters: Regulatory Structure and Options.” The San Diego Water Board in conjunction with the United States Environmental Protection Agency (USEPA), and local stakeholders investigated the conditions, sources of pollutants, loading capacity, and existing control requirements affecting the eutrophic conditions. This information was used to develop the Total Maximum Daily Load (TMDL) for the pollutants affecting the eutrophic conditions in the Slough and to develop an implementation plan to achieve the TMDL.

On June 26, 2014 the San Diego Water Board adopted Resolution No. R9-2014-0020 - Resolution of Commitment to an Alternative Process for Achieving Water Quality Objectives for Biostimulatory Substances in Loma Alta Slough which sets the path forward to eliminate the excessive algal growth in Loma Alta Slough in Oceanside by using an existing regional stormwater permit designed to provide safe, cleaner water for the region. With this action, the San Diego Water Board chose a practical, measureable, and timely approach for directing actions to remedy the Slough through a productive collaboration with the community to address an important water quality challenge.

How to Receive Updates on the Loma Alta Slough Phosphorus TMDL

The San Diego Water Board would like to keep interested persons fully informed during the development and approval process for the Loma Alta Slough Phosphorus TMDL. Updates on the TMDL will only be sent to persons that specifically request this information. To receive updates from the San Diego Water Board, you must either: 1) subscribe to our electronic mailing list; or 2) send an email request to the contact person listed below to have information sent to you via U. S. Mail. You may also obtain information from our website or by appointment at the San Diego Water Board office.

Public Documents

The following documents are available for review at the San Diego Water Board Office. To request a file review please contact the Regional Board receptionist at (619) 516-1990, or email rb9_records@waterboards.ca.gov.

Questions and comments regarding the Loma Alta Slough Phosphorus TMDL Project may be directed to Ms. Jody Ebsen at 619-521-3965, or by email at Jody.Ebsen@waterboards.ca.gov

Resolution No. R9-2014-0020, Resolution of Commitment to an Alternative Process for Achieving Water Quality Objectives for Biostimulatory Substances in Loma Alta Slough

  • Resolution No. R9-2014-0020
  • Attachment to Resolution R9-2014-0020 - Phosphorus Total Daily Maximum Load for Loma Alta Slough, Oceanside, California (Draft TMDL Report)
  • Appendix 1 to Draft TMDL Report - Watershed Loading, Hydrodynamic and Water Quality Modeling in Support of the Loma Alta Slough Bacteria and Nutrient TMDL

Scientific Studies and Reports

Technical Approach to Develop Nutrient Numeric Endpoints for California Estuaries, prepared by the Southern California Coastal Water Research Project, dated March 2007

  • Technical Approach to Develop Nutrient Numeric Endpoints for California Estuaries

San Diego Lagoons Phase 1 Report San Diego Regional Lagoon TMDLs, Phase I - Data Compilation and Model Configuration, prepared by Tetra Tech, Inc., dated June 2008

  • SD Lagoons Phase 1 Report

Carlsbad Hydrologic Lagoon Monitoring Report, prepared by MACTEC Engineering and Consulting, Inc., dated June 2009

  • Carlsbad Hydrologic Lagoon Monitoring Report
  • Appendix A – Continuous Hydrologic Data
  • Appendix B – Agua Hedionda Continuous Water Quality Data
  • Appendix C – Summary of Analytical Results
  • Appendix D – Constituent Loading Summary
  • Appendix E – Concentration Pollutographs
  • Appendix F – First Flush Ratio Figures
  • Appendix G – Load Pollutographs
  • Appendix H – Load Duration Curves
  • Appendix I - Instantaneous Dissolved Oxygen (DO) Distribution Figures
  • Appendix J - Ocean Inlet Land Elevation Surveys
  • Certification Sheets

Eutrophication and Nutrient Cycling in Loma Alta Slough, Oceanside, California, prepared by Southern California Coastal Water Research Project, dated December 2011

  • Loma Alta Slough Eutrophication and Nutrient Cycling

Watershed Loading, Hydrodynamic, and Water Quality Modeling in Support of the Loma Alta Slough Bacteria and Nutrient TMDL, prepared by Coastal Monitoring Associated, LLC and Southern California Coastal Water Research Project, dated April 2013

  • Loma Alta Slough Modeling Report

For More Information

Any questions or comments regarding the Loma Alta Slough Phosphorus TMDL Project may be directed to Ms. Jody Ebsen at 619-521-3965, or by email at Jody.Ebsen@waterboards.ca.gov.