Tijuana River Watershed Group Project

Mitigation of Impaired Stormwater Quality in Los Laureles Canyon, Tijuana, Mexico April 2, 2008 K. Heyn, R. Keane-Dengel, W. Lewis, J. Phillips, N. Virgilio

Tijuana River Watershed Source Data: SDSU TRW, 1996

Transborder Pollution Source: Wildcoast.net Human health effects; Environmental degradation; Social, political & economic impacts Source: phfactor.net Plume (Pacific Ocean) Tijuana River Estuary Los Laureles Canyon Tijuana River Imperial Beach Tijuana

Los Laureles Canyon Source: N. Virgilio, May 2007

Los Laureles Canyon Source: N. Virgilio, May 2007

Los Laureles Canyon Source: R. Keane-Dengel, May 2007

Los Laureles Canyon Source: J. Phillips, Oct. 2007

Coastal Zone on U.S. Side Source: N. Virgilio, May 2007

Pollutants of Concern Source: N. Virgilio, May 2007 Pathogens Sediment Refuse/Debris

Research Questions What is the magnitude of the transborder pollution problem in Los Laureles Canyon? How can stakeholders reduce the transport of pathogens, sediments, and refuse through the canyon?

Client and Stakeholders International Boundary Water Commission (IBWC) State California SWRCB SDRWQCB Local County of San Diego City of Imperial Beach Federal U.S. EPA NOAA Federal National Water Commission (CNA) State State Public Services of Tijuana (CESPT) Tijuana Water Authority Local City of Tijuana

Approach Pathogens Sediment Refuse/Debris Literature review Stakeholder meetings Site visits Watershed model Sewage management Treatment: *Septic *Sewering BMPs: * Structural *Community- based Stormwater management Survey Research RecommendationsRecommendations

Sewage Management Selecting a Modeling Approach Limited Los Laureles Canyon water quality data Limited Los Laureles Canyon water quality data Extensive geospatial resources (SDSU) Extensive geospatial resources (SDSU) Meteorological and hydrologic data Meteorological and hydrologic data Goal for modeling: Establish magnitude of pathogen problem Establish magnitude of pathogen problem Understand the implications of different sewage management scenarios in Los Laureles Canyon Understand the implications of different sewage management scenarios in Los Laureles Canyon

Sewage Management Watershed Model (WARMF) WARMF simulates: WARMF simulates: Physical processes affecting streamflow Physical processes affecting streamflow Loading of pollutants from landuses Loading of pollutants from landuses Routes waters and contaminants through watershed Routes waters and contaminants through watershed Simulates different sewage management scenarios Simulates different sewage management scenarios Source: WARMF, W. Lewis 2008

Los Laureles Hydrology

Fecal Coliform Loading

Sewage Management WARMF Results

Sewering San Bernardo Sewering San Bernardo Septic systems in Los Laureles Canyon Septic systems in Los Laureles Canyon Sewering in Los Laureles Canyon Sewering in Los Laureles Canyon Sewage Management Modeling Scenarios

Sewage Management WARMF Results

Sewage Management Modeling Discussion Sewering San Bernardo Sewering San Bernardo Slight reduction in fecal coliform concentrations Slight reduction in fecal coliform concentrations Contributions from other basins not addressed Contributions from other basins not addressed Need for basin-scale actions Need for basin-scale actions Septic system effectiveness limitations Septic system effectiveness limitations Slope and soils not conducive Slope and soils not conducive Require subsidy from government Require subsidy from government Sanitary sewering may be viable Sanitary sewering may be viable

Stormwater Management Challenges Unstable soils, high erosion Unstable soils, high erosion High volume of refuse High volume of refuse Flashy hydrology Flashy hydrology Minimal infrastructure Minimal infrastructure Selection Criteria Low maintenance Low maintenance Self-contained Self-contained Tamper resistant Tamper resistant Low cost Low cost Potential for multi-use Potential for multi-use

Stormwater Management BMP Options NZWERF.ORG RFCITY.ORG CHEMTEXINC.COM

Stabilization Options: Tire retaining walls Stormwater Management Source: Civil Engineering Department, Clemson University, 1999

Source: Oregon Department of Environmental Quality, 2005 Source: R. Keane-Dengel, May 2007 Stabilization Options: Terracing Stormwater Management

Source: Woodlot Alternatives, Inc, 2007 Source: Urbonas, 2003Source: John McCullah, 1994 Riprap Schematic Channel Stabilization Options Stormwater Management

BMPs: Detention and infiltration basins Stormwater Management Source: North Carolina State University, 2005 Source: Bill Southard, DES Architects and Engineers Capability to remove Sediments Sediments Bacteria Bacteria Nutrients Nutrients Trash Trash Metals Metals Cultural Adaptation Discourage settlement Discourage settlement Multi-use Multi-use

Stormwater Management BMPs: Vegetated swales Intended to treat dry weather flow and small storm events Intended to treat dry weather flow and small storm events Source: King County Surface Water Design Manuel, 2005 Source: City of Sandy, 2008

Stormwater Management Erosion Control Channel StabilizationDetention and Infiltration Basins Vegetated Swales

Community-Based Actions Community Actions Replicate permeable pavement program Replicate permeable pavement program Rainwater collection workshop Rainwater collection workshop Residential erosion control Residential erosion control Tire retaining wall workshop Tire retaining wall workshop Source: J. Phillips, 2007

Key Recommendations Coupled strategies to address sewage and stormwater Encourage community-based actions Encourage community-based actions Implement multiple stormwater technologies Implement multiple stormwater technologies Provide sanitary sewer service Provide sanitary sewer service Watershed management approach vital “End of pipe” measures often ineffective “End of pipe” measures often ineffective Los Laureles Canyon should be part of larger landscape approach Los Laureles Canyon should be part of larger landscape approach Advocate transborder cooperation and collaboration Advocate transborder cooperation and collaboration

Acknowledgements Dr. Robert Wilkinson, Project Advisor Dr. Arturo A. Keller, Project Advisor Oscar Romo, NOAA Coastal Training Program Coordinator Bart Christensen, SWRCB Border Division Mayda Winter, City of Imperial Beach Laura Peters, SWRCB Clean Beaches Program Douglas Liden, U.S. EPA Region 9 Border Division Harry Johnson and SDSU TRW Program Source: N. Virgilio, 2007

Stormwater Management Infiltration Basin Estimated Costs

Stormwater Management Dry Detention Basin Estimated Costs

Stormwater Management Vegetated Swales Estimated Costs