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San Diego border sewage plant primary expansion advances, completion set for 2031

San Diego border sewage plant primary expansion advances, completion set for 2031

Built World

$552M phase 1 award to PCL-Stantec; secondary treatment still lacks funding

Today: ENR reports $552M award and 2031 target

Overview

Updated 1 hour ago

Raw sewage from Tijuana has fouled San Diego beaches for two decades. The plant built to stop it just received the biggest contract in its expansion history: $552 million for primary treatment, sized to handle 50 million gallons of raw sewage a day by May 2031.

Federal officials had promised full secondary treatment by December 2027, which would make the water clean enough to discharge. That schedule has slipped: primary treatment now targets 2031, and the secondary treatment phase is not funded at all.

Why it matters

Two decades of Tijuana sewage on San Diego beaches won't fully end before 2031 — primary treatment is funded, secondary is not.

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Key Indicators

$552M
Revised phase 1 contract value
Raised from $106M by October 2026 modification for primary treatment expansion.
50 MGD
Target primary treatment capacity
Phase 1 lifts raw sewage treatment from current 35 MGD to 50 MGD.
May 2031
Substantial completion target
1,643-day construction period from notice to proceed; earlier internal target was 2030.
35 MGD
Current treatment capacity
Reached after fast-tracked 100-day expansion completed August 2025, up from 25 MGD.

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People Involved

Organizations Involved

Timeline

2025 October 2026

8 events Latest: Today
Tap a bar to jump to that date
  1. ENR reports $552M award and 2031 target

    Today Report

    Engineering News-Record publishes details of the revised award, construction schedule, and unfunded secondary treatment phase.

  2. Revised award issued; completion set for May 2031

    Contract

    USIBWC issues revised contract to PCL; substantial completion scheduled for May 2031 after earlier 2030 target.

  3. USIBWC raises phase 1 award to $552.4M

    Contract

    Contract modification adds early work packages and base construction; total revised to $552,372,021.

  4. Parallel Gravity Line completed

    Milestone

    Sewage capture pipeline connecting Tijuana flows to the plant comes online.

  5. IBWC says full expansion slips to 2030

    Disclosure

    Agency tells California water board 50 MGD secondary treatment targets 2030, past the 2027 federal pledge.

  6. Plant reaches 35 MGD capacity

    Milestone

    Interim expansion completed in 100 days, a 40% capacity increase from 25 MGD.

  7. EPA and USIBWC announce 100-day expansion

    Announcement

    Fast-tracked interim work raises South Bay plant capacity from 25 to 35 MGD.

  8. PCL-Stantec wins plant expansion contract

    Contract

    Initial design-build award for the South Bay plant's broader expansion program.

Scenarios

1

Phase 1 primary expansion completes on schedule in May 2031

Possible Resolves by Q2 2031

Discussed by: USIBWC, PCL Construction contract schedule, Engineering News-Record

PCL completes the 1,643-day construction period on target. New headworks, chemical system, primary sedimentation tanks, and sludge thickening facilities come online incrementally, raising primary treatment capacity to 50 MGD. This assumes no major discovery during excavation, shoring, and dewatering that extends the schedule.

2

Secondary treatment funding secured

Unlikely Resolves by Jan 1, 2029

Discussed by: USIBWC spokesman Frank Fisher, EPA quarterly updates

Congress or the administration appropriates funds for the secondary treatment expansion, which adds 10 secondary sedimentation tanks and 7 activated sludge tanks. Without it, the plant can settle solids but cannot fully clean water before discharge, leaving the core goal of the federal commitment unmet.

3

Delays push phase 1 completion past May 2031

Possible Resolves by Q2 2031

Discussed by: Contract's construction allowance increase, Engineering News-Record

Unknown conditions surface during shoring, dewatering, and excavation of the new structures. The construction allowance was raised from $1.78M to $11.59M partly to cover uncertain field conditions, an early signal that surprises are expected. If the allowance proves insufficient or conditions worsen, PCL and USIBWC would revise the substantial completion date.

Historical Context

3 moments from history that rhyme with this story — and how they unfolded.

2000s–present

Tijuana River sewage crisis (early 2000s–present)

Raw sewage from Tijuana has flowed into the Tijuana River and onto San Diego beaches for at least two decades, closing beaches in Imperial Beach and creating health risks in border neighborhoods.

Then

The South Bay plant treated only part of the flow; sewage crossed the border during storms and high flows.

Now

Two binational agreements and multiple infrastructure projects were launched to capture and treat the sewage, including the current plant expansion.

Why this matters now

This is the problem the $552M expansion is meant to solve. It explains why the project exists and why every schedule slip extends the suffering of nearby communities.

May–August 2025

100-day fast-track expansion to 35 MGD (2025)

The Trump administration's EPA and USIBWC announced and completed a 10 MGD interim expansion in 100 days, raising capacity from 25 to 35 MGD. The work was originally estimated to take two years.

Then

Capacity rose 40%, reducing sewage overflows through the following season.

Now

Studies validated the plant can process 50 MGD once upgrades finish, setting up the current phase 1 work.

Why this matters now

Shows how fast a smaller phase can move versus the multi-year, multi-hundred-million-dollar primary expansion now funded.

2025

Original federal commitment of 50 MGD by December 2027 (2025)

With the 100-day expansion complete, the EPA announced plans to reach 50 MGD of full secondary treatment by December 2027 under the amended state discharge permit and binational agreements.

Then

The California water board reissued the plant's discharge permit authorizing the expansion.

Now

By April 2026, USIBWC acknowledged full secondary treatment wouldn't be done until 2030. The phase 1 primary work now targets May 2031, with secondary treatment unfunded.

Why this matters now

The gap between the 2027 political commitment and the 2031 funding-backed schedule is the core tension of this story.

Sources

(6)