HIDDEN VALLEY LANDFILL (THUN FIELD) WASHINGTON EPA ID# WAD980511539

EPA Region 10 Pierce County Puyallup 8th Congressional District Other Names: Thun Field, Pierce County Landfill

Last Update: April, 2010

Site Description

This 92-acre site in Puyallup, Washington, has operated as a landfill and gravel pit since 1967. Until 1985, the landfill accepted liquids, solids, industrial wastes, and heavy metal sludges. Fifty-six acres of the landfill had no ground protection and now this area is closed and covered. All other waste was disposed of in a 30-acre area protected with lining and a system that collects and treats leachate (contaminated liquids that move through the landfill masses and can contaminate groundwater).

In 1998, 12 acres of the lined area were capped and later that same year the landfill stopped accepting waste. From 1999 until 2000, the remaining acres were capped.

The Sunrise housing development is located east of the site and the Gem Heights development is located northwest of the site. A survey of wells conducted in 1985 and 1999 confirms that homes in the vicinity of the landfill receive water from the water purveyors. Within the vicinity of the landfill, most residents receive water from the Fir Grove Water District. The nearest Fir Grove supply wells are approximately 4,000 feet from the landfill. The site overlies the Central Pierce County Aquifer System, a sole source aquifer.

Site Responsibility: This site is being addressed through state and potentially responsible parties.

NPL Listing History	Dates
Proposed Date:	06/10/1986
Removed Date:
Withdrawal Date:
Final Date:	03/31/1989
Deleted Date:

Threats and Contaminants

Media Affected: Groundwater
Groundwater beneath the site and leachate in the landfill are contaminated with metals, volatile organic compounds (VOCs), and nitrates. People who ingest or come into direct contact with contaminated groundwater or leachate may suffer adverse health effects.


Cleanup Progress

Early Actions: In 1989, the gas control system was modified by the landfill owner/operator, as an interim action. Modifications continue as necessary. The landfill gas system was recently modified to convert waste into energy and supply electricity to a compost facility adjacent to the landfill. The landfill has been capped to protect the soil and groundwater.

Long-Term Actions: The Remedial Investigation and Feasibility Study (RI/FS) was completed in 1992 under a Consent Decree agreement between the Washington State Department of Ecology (Ecology) and the landfill owner/operator. In 2000, the final Cleanup Action Plan (CAP) was completed . The remedial action minimized production and movement of leachate.

The CAP ultimately required the landfill to close, monitor for compliance, and implement institutional controls approved by Ecology.

Corrective actions include: covering the waste with an impermeable barrier to control leachate from leaking into the ground; collecting landfill gases to prevent them from escaping the landfill; controlling surface water and soil erosion; limiting human and animal contact with the waste; minimizing the lateral and vertical movement of contaminated groundwater by reducing the production of leachate.

Post-closure requirements include: monitoring landfill gases and groundwater; Operation and Maintenance (O&M) activities will need to be approved by Ecology and formalized in a written manual; access and uses of the land will be restricted to ensure the remedy continues to protect human health and the environment. Any activity that may interfere with the cleanup action is prohibited.


Regional Contacts

SITE MANAGER(S):	Mohsen Kourehdar (state)
E-MAIL ADDRESS:	mkou461@ecy.wa.gov
PHONE NUMBER:	360-407-6256 Tim Brincefield (EPA contact) brincefield.timothy@epa.gov 206-553-2100
COMMUNITY INVOLVEMENT COORDINATOR:	Washington Department of Ecology
E-MAIL ADDRESS
PHONE NUMBER:

Information pertaining to this site is housed at the following location(s):
Washington Department of Ecology (Administrative Record)
Southwest Region, Records Center
300 Desmond Drive SE
Olympia, WA 98504