Guardian Environmental Services Co.

Scope Of Work

The Gorst Creek Landfill is located in a creek ravine approximately 800 feet long and 60¬80 feet deep. The landfill was created by channeling the creek through a 24 inch culvert at the base of the ravine and dumping waste on top of the culvert. The amount of waste in the landfill is unknown but estimated at 150,000 cubic yards.

The weight of the landfill has crushed the creek culvert in at least two locations. The crushed culvert restricts water flow and when it rains the creek impounds upstream of the landfill, at times reaching depths of 40 to 60 feet. Impounded water seeps through the landfill and occasionally flows over its surface, causing erosion and failure of the landfill slope. Slope failures have uprooted trees, altered the course of the creek, increased sedimentation, and distributed waste material up to 1/4 mile downstream.

The landfill also presents a threat to State Highway 3 located approximately 100 yards downstream. Waste from previous landfill slides has blocked the culvert beneath the highway, requiring the Washington Department of Transportation to clear the culvert to prevent highway flooding and erosion of the highway embankment.

The creek is habitat for threatened Chinook salmon and steelhead, as well as coastal cutthroat trout, a state priority species. Landfill slides degrade downstream water quality and habitat, and the crushed culvert blocks fish passage to upstream habitat. The Suquamish Tribe operates a
Chinook hatchery 2.5 miles downstream and is concerned about impacts on fish and habitat. The Tribe has raised treaty rights as an issue.
The landfill is an ongoing source of contaminants to the downstream environment. PCBs, pesticides (DDE/DDT) and metals (lead, arsenic, mercury, copper, and zinc) have been detected at concentrations exceeding screening levels. Detected concentrations mostly present an ecological risk with limited human health concern, but the landfill is continuing to leach contaminants and future concentrations may exceed the concentrations that EPA has detected in limited sampling events.
Areas targeted for excavation will include removal of landfill waste. Landfill waste will be removed to the depth of the 24-inch corrugated metal pipe. Volume of waste has been estimated at 150,000 cubic yards. This entire volume of material is anticipated to be excavated from the site and segregated for transportation to recycling or disposal facilities.

GES has been tasked with providing support facilities, manpower and equipment in order to complete the excavation of this landfill. During the construction period GES will have to divert Gorst creek around the area and protect it with erosion controls to prevent hazardous materials from entering the waterway. The landfill waste will be placed in staging areas, and sorted for transportation to designated recycling or hazardous waste disposal facilities. Estimated quantities of specified waste include 46,875 tons of municipal and general waste (nonhazardous), 7,500 tons of automobile waste (car bodies), 37,500 tons of waste soil (contaminated but nonhazardous), 100,000 tons of construction waste that includes asbestos-containing material, 100,000 tires, and 18,538 tons of soil contaminated with lead and other heavy metals.

The final phase of construction for this task order is to grade and stabilize the Gorst Creek Ravine, also the construction of normal flow and overflow channels utilizing fish passage criteria is required, and revegetation of the creek ravine to prevent erosion.