The Warner Hill Landfill is a closed 50-acre municipal/industrial landfill located in Cuyahoga County, Ohio. A creek located adjacent to the site had undermined portions of the landfill, causing uncontrolled flow of leachate and localized portions of the waste to slough into the creek. If left unattended, it was feared that a massive stability failure of the landfill could occur, completely blocking the creek for nearly half a mile and causing numerous environmental problems. The facility's owner retained Geosyntec to develop and engineer the most economical, yet lasting, solution to prevent further slope failure and to keep leachate from entering the creek.
Geosyntec's Scope of Services
Geosyntec began by performing a fast-track, detailed site investigation and feasibility evaluation of various solutions, with the objective of increasing the stability of the waste slope, decreasing leachate generation, and reducing the potential for leachate migration into the adjacent creek. The selected remedy included the relocation of 200,000 cubic yards of waste to flatten the slopes, and construction of a 25-ft high, 3000-ft long concrete crib wall to buttress the waste and protect it from further undermining by the creek. We chose a crib wall to minimize the amount of waste regrading so close to the creek, and due to very limited access for heavy equipment in the area. As the waste was being relocated, a leachate interceptor drain was installed between the waste and the creek and a new cover system was installed over the entire landfill.
Geosyntec worked closely with the owner to develop a detailed remedial design report for submittal to the Ohio Environmental Protection Agency (OEPA), then coordinated all activities to obtain the necessary permits from the OEPA, Cuyahoga County Board of Health, and Northeast Ohio Regional Sewer District. We also made several presentations to the regulators and local citizens groups to build stakeholder confidence in the proposed remedy. After obtaining regulatory approval, we prepared a construction bid package that included drawings, specifications, and contract documents, and managed the bid evaluation and contractor procurement process.
All construction activities, including waste regrading and cover construction, had to be performed without disturbing an existing active landfill gas extraction system. As such, construction activities required considerable planning of staged construction to ensure stability and contain leachate, while optimizing equipment productivity and material staging/stockpile locations, etc. Geosyntec directed the remedial activities by providing Construction Quality Assurance (CQA), Construction Management (CM), and Resident Engineering services throughout the 2-year construction project. Since completing construction, Geosyntec has performed annual site inspections that focus on monitoring the performance of the crib wall, cover system, and surface water drainage features.
Much of the attractiveness of the selected remedy hinged on being able to discharge millions of gallons of leachate directly into the local POTW sewer system. Geosyntec successfully designed and brokered a permit to do just this, both during and after construction. When compared to other leachate treatment/management options, this resulted in cost savings of $750,000 during construction, with ongoing savings of $250,000 per year during the post-closure period.
Geosyntec's annual site inspections performed in the 10 years since the completion of the closure remedy indicate that our design and the remedial construction have: (i) prevented millions of gallons of leachate from entering the creek; (ii) protected the landfill from undermining by the creek; and (iii) maintained the stability of the waste slopes and integrity of the cover system.