The City of Kent recently completed one of the eleven projects funded in part by the DNRP Wastewater Treatment Division 2016 WaterWorks Grant Program. In addition to remediating the soil of the Leber Homestead, which is where this grant was used, the purpose of the project was to provide rearing and refuge habitat for salmon, especially for juvenile Chinook salmon, which are a threatened species in the Puget Sound.

“The Kent project is a win for the environment and also for public health,” said King County Councilmember Dave Upthegrove. During the project, high levels of arsenic were discovered in the soil. Arsenic occurs naturally, and was also introduced by pesticides used in the orchard area of the homestead. “Removing arsenic from the Leber Homestead site provides a direct benefit for both people and wildlife in the immediate area, as well as downriver,” added Councilmember Upthegrove. Arsenic is a top chemical of concern to fish, as well as to people and the Puget Sound. The contamination at the Leber Homestead site would have negatively affected the project goals, especially the goal of protecting salmon.

“This project is a great example of what WaterWorks can do for water quality,” said Elizabeth Loudon, WaterWorks Grant Administrator with DNRP’s Wastewater Treatment Division. “Removing those contaminated soils means that arsenic won’t impact salmon and other wildlife that use this site, and the cleanup prevents downriver pollution.”

After hatching and emerging from gravel riverbeds in February and March, Chinook fry begin heading toward the Puget Sound. Fry that don’t get swept away in rushing spring water find rearing and refuge habitat along the way and are able to feed and grow larger. These salmon migrate to the Sound in June instead of March, and have a marine survival rate almost ten times better than that of their earlier-outmigrating counterparts.

The Leber Homestead WaterWorks project created a floodplain wetland just up from the mouth of Mill Creek, which feeds into the Green River. Whenever flows are elevated above the average annual flow, additional off-channel refuge habitat will now be available for salmon. At ordinary high-water levels, an additional 1.6 acres of off-channel habitat – and nearly 50 acre-feet of additional flood storage – will be available during salmon outmigration at the Leber project site.

According to Matt Knox, Environmental Ecologist for the City of Kent, the additional storage helps decrease the potential impacts from floods that affect property and roadways in surrounding agricultural and urban areas. “During the last century, the Green River has been re-plumbed, dammed and leveed, leaving the floodplain more than 20 feet higher than the average water level. Reconnecting this perched floodplain with the current river was difficult and expensive, but was also crucial for salmon recovery,” said Matt.

This project, combined with others identified in the Green River Salmon Habitat Plan (2005), is expected to contribute to more than a mile of new off-channel habitat in the near future.

King County Wastewater Treatment Division’s mission is to protect public health and enhance the environment by collecting and treating wastewater while recycling valuable resources for the Puget Sound region. Wastewater Treatment funds are used to support projects that improve water quality and invest in community partnerships. Funds are awarded through the WaterWorks Grant Program. The KC WTD blog also covered this project, as did KC Council News. For more information, contact Elizabeth at 206-477-4297 or water.grants@kingcounty.gov.

For more information about this and other Kent projects, visit Kent’s Capital Projects site.