Lower Tijuana River Indicator Bacteria and Trash Advance Restoration Plan

Background Information

The Tijuana River watershed is in the southernmost portion of the San Diego Water Board’s jurisdiction. Divided by the United States-Mexico international border, approximately one-third of the watershed is in the United States and two-thirds is in Mexico. In the lower watershed, the River and several of its tributaries cross from Mexico into the United States; these transboundary flows act as conduits for pollution generated in Mexico, transporting them through the river valley, estuary, and into the Pacific Ocean.

The lower Tijuana River refers to the stretch of the river that crosses the border from Mexico into the U.S., traverses the Tijuana River Valley and the Tijuana River Estuary, and ultimately reaches the Pacific Ocean. For decades, this stretch of river has not met water quality standards due to routine and episodic transboundary flows from Mexico, often comprised of untreated domestic and industrial wastewater.

Project Description

The San Diego Water Board has developed the draft Lower Tijuana River Indicator Bacteria and Trash Advance Restoration Plan for Total Maximum Daily Loads staff report (draft ARP) to address water quality impairments through an implementation plan with actions to restore and maintain water quality standards. Waters with an ARP remain on the Clear Water Act 303(d) List until water quality standards are attained. Board staff developed the draft ARP in response to direction from the San Diego Water Board to identify a plan for water quality restoration to address impairments to human and wildlife beneficial uses of water in and around the lower Tijuana River due to high levels of bacteria and trash.

The draft ARP identifies sources of trash and indicator bacteria pollution, establishes numeric targets to achieve water quality standards in the river, and identifies potential actions for pollution control in an implementation plan. The ARP is centered on the expectation of the San Diego Water Board that the U.S. Section of the International Boundary and Water Commission (USIBWC) will work with the U.S. Environmental Protection Agency (USEPA) to implement the United States-Mexico-Canada Agreement (USMCA) Comprehensive Infrastructure Solution projects to significantly reduce indicator bacteria and trash loads in transboundary flows.

Although the Tijuana River is on the 303(d) List for impairments due to a total of 20 pollutants, control of the sources of indicator bacteria and trash is likely to result in a significant degree of control of the remaining pollutants. Pollutants that are conveyed to the lower Tijuana River by dry weather and wet weather flows are generally intermingled. Reduction of indicator bacteria requires reduction of sewage and polluted urban runoff entering the Tijuana River Valley. Therefore, the loads and concentrations of other pollutants inherent in sewage and polluted urban runoff would also be reduced.

Once the ARP goes into effect, projects in the Tijuana River Valley to meet water quality standards may include:

  • New main channel river diversion
  • New advanced primary treatment facility for main channel flows.
  • Increased treatment capacity of the South Bay International Wastewater Treatment Plant (SBIWTP).
  • Increased diversion of transboundary flows to the SBIWTP via canyon collectors.
  • Installation of trash booms in the main channel and/or cross-border tributaries.
  • Capture and disposal of trash in transboundary flows.
  • Installation of sedimentation basins in the main channel and/or cross-border tributaries.
  • New collection and conveyance infrastructure (collectors, pump stations, etc.).
  • Inspections and maintenance of best management practices/infrastructure.

The ARP, which was initially drafted as a total maximum daily load (TMDL) pollution control plan, underwent external scientific peer review during summer 2023. For a copy of the external scientific peer review report, please send an email to rb9_records@waterboards.ca.gov.

Impact to Disadvantaged Communities or Tribes

Please contact Riley Nolan regarding any concerns related to environmental justice or potential impacts on water quality for disadvantaged communities due to the ARP's future implementation.

Respecting the sovereignty of Tribal Nations, the San Diego Water Board respectfully offers Tribes the opportunity to confer with the San Diego Water Board (Nation to State) on any concerns related to environmental justice or potential impacts of Tribal uses of water due to the ARP's future implementation.

Riley Nolan, project lead
Riley. Nolan@waterboards.ca.gov
(619) 521-3358

Public Workshops and Public Comment Period

The San Diego Water Board held in-person and virtual workshops to solicit public comment on the Draft ARP on February 26 and February 28, 2024. In addition to verbal comments accepted at the workshops, the San Diego Water Board accepted written comments on the Draft ARP through March 13, 2024.

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