The Chittenden Solid Waste District (the District, CSWD) invites registered engineers or other approved qualified professionals to submit bids for an annual post-closure landfill inspection and evaluation. The location of work is the Closed Landfill located near 1492 Redmond Road, Williston, Vermont 05495 (see Attach 1). The Closed Landfill is comprised of 3 Phases. Phases 1/2 span approximately 6 acres and were constructed and operated by the Town of Williston between 1979 and 1992. Phases 1/2 are not lined but were constructed with a 20-foot sand layer placed over the existing ground layer to achieve separation from the groundwater table. These Phases were capped with a 12 inch sand gas vent layer, 24 inches of silt/clay (minimum 10-5 cm/sec permeability), and a 12 inch vegetative layer. A ‘shallow’ gas vent system passively vents through 18-3 inch PVC wells which are connected by headers in the sand gas vent layer. The 7-acre Phase 3 was constructed and operated by CSWD between 1992 and 1995. Phase 3 was constructed with a liner system comprised of 2-60 mil textured HDPE membranes. The cap includes a 40-mil textured HDPE / VLDPE composite manufactured by National Seal and referred to as “Coex”, overlain by 30 inches of soil. A passive gas vent system extends 4 feet into the refuse layer and includes (15) 4-inch diameter vents connected by a header. All of these vents are capped in order to direct the gas to 3 vents that have passive flares. Phase 3 also contains a gravity fed leachate collection system that drains to a 30,000 gallon underground storage tank. 2.0 SCOPE OF WORK The inspection and evaluation shall cover, at a minimum the integrity of the final cover system, erosion control measures, drainage systems, gas control systems, the complete existing groundwater monitoring well network, and vegetative cover. The inspection should be conducted during the month of May. The evaluation report shall be submitted to the District by June 8 for review and submittal to the Vermont Department of Environmental Conservation by June 15.
