Lower Tijuana River Indicator Bacteria and Trash Advance Restoration Plan

Background Information and Project Description

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

The San Diego Water Board has identified several “water quality limited segments” in and adjacent to the Tijuana River watershed. These are surface waters on the U.S. side of the border that do not support all their designated beneficial uses due to pollutants that cause impairments. Although the overall water quality in the upper Tijuana River watershed (U.S. side) is considered good, the lower watershed is severely impaired. The 2020-2022 Clean Water Act Section 303(d) List of Water Quality Limited Segments (303(d) List) includes the Tijuana River as well as the downstream Tijuana River Estuary and Pacific Ocean shoreline.

The San Diego Water Board has developed the draft Lower Tijuana River Indicator Bacteria and Trash Advance Restoration Plan for Total Maximum Daily Loads (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 303(d) List until requirements to remove the 303(d) listing are met. 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 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 Oceans. For decades, this stretch of river has not met water quality standards. The significant sources of indicator bacteria and trash causing the impairments are the routine and episodic transboundary flows from Mexico often comprised of untreated domestic and industrial wastewater.

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 draft 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 Melissa Corona 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.

Melissa Corona, project lead
Melissa.Corona@waterboards.ca.gov
(619) 521-8039

Public Workshops and Public Comment Period

The San Diego Water Board is accepting written comments on the draft ARP:

Draft Tijuana River Advance Restoration Plan

All written comments must be received no later than 5:00 p.m. on March 13, 2024.

An in-person public workshop and a separate virtual public workshop are scheduled for February 26 and 28, 2024, respectively. Details on the public workshops and public comment period can be found on the December 28, 2023, public:

Notice of Public Workshops and Public Comment Period

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