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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. Los Laureles Canyon. Tijuana.
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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
Los Laureles Canyon Tijuana Tijuana River Estuary Source: Wildcoast.net Human health effects; Environmental degradation; Social, political & economic impacts Tijuana River Plume (Pacific Ocean) Imperial Beach Transborder Pollution Source: phfactor.net
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 Pathogens Refuse/Debris Sediment Source: N. Virgilio, May 2007
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 Federal U.S. EPA NOAA Federal National Water Commission (CNA) International Boundary Water Commission (IBWC) State State Public Services of Tijuana (CESPT) Tijuana Water Authority State California SWRCB SDRWQCB Local County of San Diego City of Imperial Beach Local City of Tijuana
Approach Recommendat ions Survey Research BMPs: *Structural *Community-based Sewage management Treatment: *Septic *Sewering Watershed model Site visits Pathogens Literature review Stormwater management Sediment Refuse/Debris Stakeholder meetings
Sewage ManagementSelecting a Modeling Approach • Limited Los Laureles Canyon water quality data • Extensive geospatial resources (SDSU) • Meteorological and hydrologic data Goal for modeling: • Establish magnitude of pathogen problem • Understand the implications of different sewage management scenarios in Los Laureles Canyon
Sewage ManagementWatershed Model (WARMF) • WARMF simulates: • Physical processes affecting streamflow • Loading of pollutants from landuses • Routes waters and contaminants through watershed • Simulates different sewage management scenarios Source: WARMF, W. Lewis 2008
Sewage ManagementModeling Scenarios • Sewering San Bernardo • Septic systems in Los Laureles Canyon • Sewering in Los Laureles Canyon
Sewage Management Modeling Discussion • Sewering San Bernardo • Slight reduction in fecal coliform concentrations • Contributions from other basins not addressed • Need for basin-scale actions • Septic system effectiveness limitations • Slope and soils not conducive • Require subsidy from government • Sanitary sewering may be viable
Stormwater Management Challenges • Unstable soils, high erosion • High volume of refuse • Flashy hydrology • Minimal infrastructure Selection Criteria • Low maintenance • Self-contained • Tamper resistant • Low cost • Potential for multi-use
Stormwater Management BMP Options RFCITY.ORG NZWERF.ORG CHEMTEXINC.COM
Stormwater Management Stabilization Options: Tire retaining walls Source: Civil Engineering Department, Clemson University, 1999
Stormwater Management Stabilization Options: Terracing Source: R. Keane-Dengel, May 2007 Source: Oregon Department of Environmental Quality, 2005
Stormwater Management Channel Stabilization Options Source: Woodlot Alternatives, Inc, 2007 Riprap Schematic Source: Urbonas, 2003 Source: John McCullah, 1994
Stormwater Management • Capability to remove • Sediments • Bacteria • Nutrients • Trash • Metals BMPs: Detention and infiltration basins Source: Bill Southard, DES Architects and Engineers • Cultural Adaptation • Discourage settlement • Multi-use Source: North Carolina State University, 2005
Stormwater Management BMPs: Vegetated swales Source: King County Surface Water Design Manuel, 2005 • Intended to treat dry weather flow and small storm events Source: City of Sandy, 2008
Stormwater Management Detention and Infiltration Basins Channel Stabilization Vegetated Swales Erosion Control
Community-Based Actions Community Actions • Replicate permeable pavement program • Rainwater collection workshop • Residential erosion control • Tire retaining wall workshop Source: J. Phillips, 2007
Key Recommendations Coupled strategies to address sewage and stormwater • Encourage community-based actions • Implement multiple stormwater technologies • Provide sanitary sewer service Watershed management approach vital • “End of pipe” measures often ineffective • Los Laureles Canyon should be part of larger landscape approach • 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