Shelton C Street Landfill

En Español: la hoja informativa.

Ecology finalized the Cleanup Action Plan to address contamination at the site and signed a legal agreement, Agreed Order DE 19541, with the City of Shelton to implement the cleanup plan. The city is the potentially liable person (PLP) responsible for cleaning up the site. Ecology staff is overseeing the project to ensure that human health and the environment are protected during cleanup.

Ecology provided the city with a grant of about $1.98 million to perform the RI/FS, dCAP, and implement the cleanup. 

A fact sheet briefly summarizes information about the cleanup action plan.

Ecology held a public comment period from November 4 to December 7, 2021, and we hosted an informational meeting to present information about the cleanup plan and answer questions on November 18, 2021.

The documents under review during the comment period included:

• Remedial Investigation & Feasibility Study (RI/FS).
• draft Cleanup Action Plan.
• Agreed Order DE 19541 between Ecology and Shelton to implement the Cleanup Action Plan.
• State Environmental Policy Act (SEPA) Determination of Non-Significance.

We received two comments during the comment period. The responsiveness summary provides our response to those comments. We made no changes to the documents based on the comments received during the comment period. 

The site is a 16.7-acre property. Before 1928, the property was mined for sand and gravel. In 1928, the city purchased the property and began using it as a landfill until the mid-1980s. The waste is located in an area of about four acres on the property.

The landfill received mostly residential solid waste. Other waste included research waste and demolition debris. As was a common practice for the era, landfill operators burned waste in the open and in an incinerator at the site.

Sludge from the city’s wastewater treatment plant was brought to the landfill between 1973 and the mid-1980s. From 1976 to 1981, fly ash from the wood-burning power plant at the Simpson Timber Company mill was mixed with the sludge and put in the landfill. The sludge was disposed of in the northwestern part of the landfill.

Contamination sources at the site are the solid waste and wastewater treatment plant sludge.

Contact with hazardous materials at the site may harm people’s health and the environment.

Soil. People and animals at the site could potentially contact contaminants in soil by directly touching contaminated soil or accidently eating it from dirty hands or paws. Contaminants in soil include:

• Dioxins/furans.
• Carcinogenic polycyclic aromatic hydrocarbons.
• Metals (barium, copper, lead, mercury, selenium, silver, zinc, and lead).

Groundwater. Metals (arsenic, iron, and manganese) in groundwater at the site are likely due to decomposition of the waste causing a low oxygen condition in the landfill. The lack of oxygen in the landfill causes metals in the soil to move into the groundwater. 

People will not be in contact with groundwater. The water table is located more than 35 feet below the bottom of the buried waste. Iron and manganese are secondary contaminants  for drinking water under the US Environmental Protection Agency (EPA) standards.  Although they may cause aesthetic or cosmetic effects, iron and magnesium are not considered a risk to human health at the levels found at the site. 

Arsenic concentrations are well below the natural background conditions for groundwater in the area. The natural background condition is the arsenic concentration consistently present in the environment that did not result from activity at the site.

Landfill gases. Gases from breakdown of waste are not building up in the landfill. Landfill gases are not a threat to people and the environment at the site.

The plan describes several actions that include a soil cap, institutional controls, and monitoring.

Low-permeable soil cap constructed to cover all of the landfill waste. The cap prevents contaminants from coming into contact with people and animals.  

The bottom layer of the soil cap is a geotextile barrier covered by at least a 2-foot-thick layer or clean, low permeability material. The top of the cap is a 1-foot thick layer of topsoil covered with grasses and other shallow-rooted vegetation.

The cleanup is based on protecting drinking water down-slope from the site. The cap is sloped and designed to significantly reduce the amount of rainwater entering the landfill.   

Institutional controls keep people from entering the site and prevent future activities from damaging the cap. Institutional controls include fencing, a gate, and signage. An environmental covenant will be recorded with the property deed and prevent any future activity that could expose people and the environment to contaminated soil or landfill waste. 

Monitoring will make sure the cap continues to be effective in preventing exposure to contamination. Groundwater will be monitored regularly to assess the effectiveness of the cap in reducing the metals in groundwater.  

We will review conditions at the landfill every five years. 

For more information about cleanup sites in the neighborhood and throughout Washington, go to:

• What's In My Neighborhood is a map based search tool. Enter an address or zoom into an area to find sites.
• Cleanup and Tank Search is a text-based search tool and lets you filter lists by location, contaminant, cleanup status, and more. 

These tools also show completed cleanups.