The King County Industrial Waste (KCIW) Program gives the EnvirOvation Award to companies and facilities with industrial wastewater discharge approvals within the King County sewer service area that are leaders in environmental protection. The award provides an incentive to area facilities to voluntarily go beyond regulatory obligations to manage operations in ways that help support regional efforts to help protect public health and enhance the environment.
EnvirOvation Award application (due Nov. 1)
Seattle's Seawall Project wins 2016 EnvirOvation Award
Setting the scene: rebuilding the Elliott Bay Seawall
The City of Seattle Office of the Waterfront is replacing the seawall along Seattle's waterfront. The new seawall will protect critical infrastructure and utilities and serve as the foundation for projects transforming Seattle's future waterfront.
The complication: how do you build a wall that is mostly submerged underwater?
Part of the project that lies between Stewart and Columbia Streets along Alaskan Way in downtown Seattle involved excavating a hole 40 feet wide and 15 feet deep. As you may imagine, this makes for some unique conditions because there are a several sources of water that enter the site – with Elliott Bay to the west, groundwater flowing from downtown Seattle, and rain/snow from above. In sum, there is an overwhelming amount of water that could potentially enter and exit the excavation.
During a construction project, groundwater or stormwater is often pumped away from the site to keep the work area dry. This process is called dewatering. Typically, the water removed from a construction site is treated and sent to a surface water body, either directly or through a storm drain. If the treated water does not meet water quality criteria or if direct or indirect discharge is not available, the construction company can get permission to send it to the sanitary sewer.
The plot thickens: what happens when you have millions of gallons of water to remove from your site?
The SDOT project engineers were faced with a difficult problem and serious implications. How to control the large amount of water? Pumping the groundwater out would require treatment, a very expensive process. It could also create seismic issues and put stress on the viaduct structure.
King County's wastewater system is also affected by a project of this nature. When a company requests to send
large quantities of water to our system, we need to be able to process it. This requires capacity and resources. If the flow is too high, it could result in combined sewer overflows.
Creative solution: instead of removing the water, keep it from entering the site in the first place.
SDOT opted for an innovative approach: groundwater freezing. They buried pipes 35 feet into the ground. They then circulated a chilled salt water solution, which has a lower freezing point than fresh water, through the pipes to freeze the groundwater in place, keeping the work zone dry. Large chillers keep the salt water running and the pipes cool throughout the summer months. This technology reduced the amount of groundwater entering the work zone eliminating most of the need to dewater.
An innovative approach, saved money & capacity saved; potential combined sewer overflows prevented.
On this project, groundwater freezing prevented the discharge of more than 28 million gallons of wastewater to the sewer. A true win-win for the County, the City, the environment and our ratepayers.
King County Green Globe Awards
KCIW's EnvirOvation Award winners are eligible to be nominated for the King County Green Globe Leader in Industrial Waste Reduction Award. Green Globe Awards are presented by King County every two years.