87 Times a Year

Eighty-seven times a year, Seattle's sewer system dumps raw, untreated sewage directly into Puget Sound, the Duwamish River, and Lake Washington. Not stormwater. Not greywater. Human waste mixed with everything that goes down every drain in the city.

This is not a secret. It is, in fact, exactly how the system was designed.

What a CSO Is

CSO stands for Combined Sewer Overflow. In older cities like Seattle, a single pipe carries both sewage from homes and businesses and rainwater from streets and roofs. When it rains hard, the pipe fills up. When the pipe fills up, the system has two options: back sewage into basements, or open a valve and dump the overflow into the nearest body of water.

Seattle chose the valve. There are dozens of these outfall points scattered along the city's waterways. Each one is a concrete pipe that opens directly into the water. When it rains, the pipes open. The sewage flows out.

This is legal. It is permitted under a federal consent decree between Seattle and the U.S. Environmental Protection Agency. The city has been operating under this consent decree for decades, and the agreement gives the EPA direct authority over how Seattle manages its sewer infrastructure.

Most people in Seattle do not know this. The federal government has direct legal authority over the city's sewer system right now, backed by a court order, enforced by the EPA, and financed by $706 million in federal loans that start coming due in July 2026. Nobody at City Hall is talking about it.

The Consent Decree

A consent decree is a legally binding agreement between a government agency and a party that has been found in violation of federal law. In Seattle's case, the city's combined sewer system violates the Clean Water Act by discharging raw sewage into Puget Sound, the Duwamish River, and Lake Washington during rainstorms.

The consent decree between Seattle and the EPA requires the city to reduce these overflows on a specific timeline. If the city fails to comply, the EPA can impose fines, mandate specific infrastructure projects, or take the city to federal court. This is not a suggestion. It is a court order.

The practical effect: the EPA has veto power over how Seattle builds and maintains its sewer infrastructure. Every major capital project in the drainage system must satisfy the terms of the consent decree.

The WIFIA Loans

To pay for the required infrastructure upgrades, Seattle borrowed $706 million through the Water Infrastructure Finance and Innovation Act (WIFIA) program. WIFIA is a federal loan program administered by the EPA. The loans carry below-market interest rates, but they also carry compliance covenants.

Those covenants give the EPA additional leverage beyond the consent decree itself. If Seattle falls out of compliance, the WIFIA loan terms can be renegotiated or accelerated. The federal government is both the regulator and the lender.

The Cost Overruns

The centerpiece of Seattle's compliance strategy is the Ship Canal Water Quality Project, a deep-bore tunnel designed to capture sewer overflows along the Lake Washington Ship Canal. The project was originally budgeted at $423 million. It is now projected to cost approximately $710 million, a 68% cost overrun.

Seattle is paying roughly nine times what Chicago paid per mile of comparable deep-bore sewer tunnel. The city has not published a detailed cost comparison or audit of the overrun.

Meanwhile, Seattle residents pay $62.31 per month in drainage fees. Portland pays $25. Tacoma pays $35. Seattle's rates are the highest in the Pacific Northwest, and they are still not enough to cover the cost of the tunnel without federal loans.

The Green Alternative

Not every city solves its CSO problem with a multi-billion-dollar tunnel. Green infrastructure, which uses natural systems like rain gardens, bioswales, permeable pavement, and restored wetlands to absorb stormwater before it enters the sewer, has been proven effective in multiple cities and in Seattle itself.

Thornton Creek Watershed. A restored urban creek system in northeast Seattle that manages stormwater through natural infiltration. The project cost a fraction of the Ship Canal tunnel and handles significant stormwater volume.

Barton CSO Rain Gardens. A neighborhood-scale green infrastructure project in West Seattle that was specifically designed to reduce combined sewer overflows. It works. SPU's own data shows the Barton project reduced overflow volumes in its target area.

Green infrastructure is not a complete replacement for the tunnel. But it can reduce the scale and cost of hard infrastructure required, and it provides co-benefits: cleaner waterways, healthier neighborhoods, habitat restoration, and reduced urban heat.

The question is why the city committed to a $710 million tunnel before fully exploring the green alternative. The consent decree does not mandate a tunnel. It mandates overflow reduction. How the city achieves that is, within limits, up to the city.

We Mapped Every Outfall

Burnham Civic identified and mapped every active CSO outfall location in the city of Seattle. The map shows where each pipe is located, which waterway it discharges into, and what neighborhoods are affected.

The outfalls are concentrated along the Ship Canal, the Duwamish River, and the Lake Union shoreline. Some are in residential neighborhoods. Some are near parks where children play. Some discharge within sight of restaurants and marinas.

The data is public. The locations are published by Seattle Public Utilities. But nobody has put it all in one place and said: this is what your $62.31 a month buys you.

What TBC Is Doing

Burnham Civic has mapped every outfall and is now actively engaging the EPA on consent decree compliance. We are monitoring the city's adherence to every milestone in the decree and every covenant in the $706 million WIFIA loan agreement. Principal repayment begins in July 2026.

If Seattle falls out of compliance, the consequences are real. WIFIA loans carry federal default provisions. A default finding would give the EPA grounds to assert effective control over the infrastructure projects themselves. Burnham Civic is building the case file to support that intervention if the city's performance warrants it.

We have filed public records requests with Seattle Public Utilities and are pursuing specific questions about project cost allocation, contractor selection, change order history, and the city's internal compliance assessments. These requests are in progress.

The objective is straightforward: these projects can be delivered at a fraction of their current cost. Chicago built a comparable tunnel for $28 million per mile. Seattle is paying $263 million. Green infrastructure alternatives, including the Thornton Creek watershed restoration and the Barton CSO rain gardens in West Seattle, have proven effective at lower cost and with broader community benefit. Under federal oversight, the city would be compelled to pursue them.