Combined sewer overflow: how stormwater became Puget Sound’s #1 source of pollution

Stormwater runoff is the #1 source of pollution in Puget Sound, threatening human, fish and aquatic life. But how does rain result in pollution? One contributor is in how cities manage their sewage.

Seattle implemented its first centralized sewer system in the early 1900s ahead of a premier world fair. Rather than having separate pipes for sewage and stormwater, Seattle’s chosen system collected both sewage and stormwater through the same pipe. Generally, there was no issue as the combined sewage was treated at water treatment plants.

Graphic detailing the route of sewage under dry conditions.

Sewage is directed to a water treatment plant during dry weather.

However, heavy rain overloaded this system, dumping an overflow of untreated sewage and stormwater into Puget Sound, the Duwamish River and other local waters. The combined sewage included human waste, heavy metals from roads and pollutants accumulated on roofs. The polluted water is highly toxic to salmon, orcas and other aquatic wildlife. Moreover, it is detrimental to people swimming in the waters or fishing in urban rivers.

Graphic detailing the route of combined sewage during heavy storms.

During large storms, stormwater is combined with sewage in the same pipe, and the increased volume overflows straight into nearby waters.

The archaic combined sewer systems still exist today. Construction of new combined sewer systems stopped in the 1950s, but older systems have yet to be completely replaced. And with population growth and urbanization in Puget Sound, combined sewer overflow has only become more polluted.

Green Stormwater Infrastructure (GSI) such as rain gardens and cisterns reduce the amount of stormwater entering the combined sewers. More combined sewage is captured by the sewer system and treated properly, rather than going into Puget Sound waters.

Graphic detailing the route of combined sewage during heavy storms controlled by Green Stormwater Infrastructure (GSI).

Green Stormwater Infrastructure (GSI) manages stormwater so that sewer systems are less likely to overflow.

ECOSS engages multicultural communities to raise awareness about GSI opportunities for property owners so that communities of color can be included in the solutions for clean water and healthier communities. Furthermore, ECOSS recruits and guides multicultural contractors through training to install cisterns and rain gardens. These green career pathways promote small businesses of color and ensure that the benefits of GSI solutions are reaching Puget Sound’s most vulnerable communities.

Read more about stormwater solutions

Thank you King County for source material inspiration of the first two graphics.

ECOSS named a leader in environmental excellence

The Port of Seattle honored ECOSS as an Environmental Excellence Awardee!

Video by Port of Seattle with footage and photos contributed by ECOSS and Sam Le.

ECOSS’ programs are as diverse as the communities and businesses it serves. From clean energy to waste management, outdoor recreation to stormwater education, ECOSS provides access to environmental solutions to small businesses and marginalized communities. By working from within the communities that are most-impacted by climate injustices, ECOSS bridges gaps among industry, government and communities in ways that respect people’s cultures and lifestyles.

The Port of Seattle’s Environmental Excellence Award celebrates “the dedication of local partners to engage in healthier communities for cleaner air and cleaner water and to invest in enhanced energy efficiency.”

The Port of Seattle recently honored ECOSS with an Environmental Excellence Award for achievements in environmental equity! ECOSS envisions sustainable businesses and thriving communities supported by equitable environmental solutions. The award symbolizes that ECOSS is on the right track in addressing environmental injustices.

Learn more about ECOSS’ programs.

ECOSS receiving the Environmental Excellence Award with Port commissioners and staff.

ECOSS joined other environmental leaders, including small businesses recognized for their transition to clean energy and transportation heavyweight Lyft that is greening their rideshare service.

Check out the award and other awardees!

Thank you Port of Seattle for honoring ECOSS with this honor. And thank you SVP for nominating ECOSS for the award.

Green business education achieves new milestones in 2018

Polluted stormwater runoff is the #1 pollution source around Puget Sound. Businesses are helping mitigate that pollution.

Spill kit demonstration. Photo Credit: Enviroissues.

During heavy rainfall, water picks up pollutants from impervious surfaces like roads and parking lots. This water flows directly from storm drains to our waterways, harming the health of communities and aquatic life. Industries and municipalities are major originators of the oils, fuels, metals and other pollutants that ultimately contaminate Puget Sound waters. But some businesses want to change that and ECOSS provides the tools to do so.

In 2018, we visited over 1,400 businesses, delivered nearly 650 spill kits and provided spill training and prevention plans in more than 30 Puget Sound cities and counties. Spill kits help businesses keep spilled materials from reaching storm drains in streets, alleys and parking lots.

Outreach is personalized to each business. Photo Credit: Kelvin Kong / ECOSS.

And our offerings for stormwater management workshops and trainings nearly doubled in 2018. Seven industry-focused workshops reached almost 100 individuals and over 80 companies. And 18 municipal-focused workshops trained 625 municipal staff across 37 jurisdictions, agencies and businesses. These workshops help attendees understand permitting requirements, improve stormwater management practices and protect local waters and watersheds.

Donate to empower more green businesses

Help us expand our business outreach for greener businesses, cleaner waters and healthier communities!