New Decant Facility Helps Nation’s Greenest Utility Protect Environment, Reduce Costs

A vactor truck delivers water pumped from underground vaults to City Light’s new decant facility.

A new facility in South Seattle is helping Seattle City Light protect the environment, streamline operations and reduce costs for our customer-owners.

City Light recently completed construction of a $1.5 million carbon filtration decant facility at our South Service Center on 4th Avenue S. The facility pretreats storm water and solids that utility crews collect from electrical vaults and slurry from pole excavation activities so it can be disposed of in a cost-effective manner while meeting all federal, state, and local environmental regulations.

“We’ve been having to haul liquids and solids from vaults all the way to Fife,” General Manager and CEO Jorge Carrasco said during a ribbon-cutting ceremony May 15. “It’s very expensive to do that,” he said. “Just as important, we’ve always wanted to do the right thing environmentally.”

Some of this water comes from underground vaults that crews must empty before they can perform maintenance work. City Light also collects the water we use when crews dig holes with hydro excavators for many utility poles. Instead of a metal augur, hydro excavators use high-pressure water jets and suction hoses to remove soil, reducing the risk of damaging other underground equipment like gas, water, communications and sewer lines that might be in the area.

Before the new decant facility opened, a treatment plant in Fife was the closest option for City Light to properly dispose of the water we collected. Operating our own facility will save the utility at least $125,000 per year in operating costs and reduce the amount of time employees spend hauling large quantities of storm water to Fife. It also will cut down on the amount of greenhouse gas emissions created by our trucks, which helps us remain carbon neutral because we’ll have less to offset.

Those efficiencies will help City Light continue to provide some of the lowest cost electricity in the nation to our customers in an environmentally responsible manner. That’s one more reason we call ourselves the nation’s greenest utility.

The facility now operates at the southwest corner of the South Service Center grounds. It was designed by Gray & Osborne and built by McClure and Sons Construction.