GZA was retained by the Town of Hamburg to evaluate the Town’s existing closed landfill and develop a remedial design for the 11-acre landfill. The landfill was identified by the New York State Department of Environmental Conservation (NYSDEC) to have waste protruding through the existing cap, leachate outbreaks, and have flat top slopes inhibiting stormwater runoff from the landfill.
GZA subcontracted with another consultant to do the following:
- Conduct a topographic and planimetric survey of the landfill area to measure pre-construction conditions for determining excavation quantities for the proposed work, and locate existing drainage structures and trees.
- Located delineated wetland areas around the landfill perimeter.
- Located test pit explorations done by GZA.
GZA coordinated and monitored a test pit exploration program to define the areal limits and depth of waste in the landfill, and characterize and quantify the miscellaneous fill soils placed atop the landfill subsequent to closing of the landfill in the 1980’s. Characterizing these fill soils allowed GZA to incorporate the soils for backfill in constructing perimeter drainage channels and achieve final grades. The test pits also helped quantify the amount of available topsoil for re-use.
From the wetland delineation, GZA filed a United States Army Corps of Engineers (USACOE) Wetland Permit Application for this Project. The permit application identified that wetland mitigation for the area disturbed would require construction of a wetland area equal to the area of wetland lost due to the project.
The remedial design required relocating waste and the miscellaneous fill soils to achieve minimum 4% and maximum 33% slopes to provide proper drainage off the landfill cap. GZA developed an excavation and grading plan to maximize use of the on-site soils and minimize the amount of imported soils required. The grading plan also minimized relocation of waste to the extent possible. The design also incorporated a perimeter drainage channel to direct surface water drainage to one discharge point draining to an existing stormwater drainage channel.
GZA also evaluated a borrow source owned by the Town for possible use as low permeability soil cover. We approximated the volume of available soils and performed geotechnical laboratory tests in our laboratory including measuring the soil’s plasticity, gradation, Proctor values (for determining compaction criteria) and permeability. The laboratory test data indicated that the soil was acceptable for use as low permeability soil for the final cover system.
GZA developed design drawings, technical specifications, Quality Assurance/Quality Control Plan and contract documents for obtaining competitive contractor bids for the remedial construction and provided quality assurance oversight of the construction. The project was successfully constructed in 2008.