Tetra Tech developed a long-term facility master plan for the Sussex County Landfill in New Jersey, including a mechanically stabilized earth (MSE) berm that significantly extends facility life.
When flow control was declared to be unconstitutional, Sussex County Municipal Utilities Authority (SCMUA) drew on its closure/post-closure funding to maintain operations. With closure anticipated for 2021, the facility had inadequate funds to maintain operations for the post-closure period. A prior consultant evaluated expansion alternatives for the site and determined that expansion would be a break-even proposition at best and would not address an estimated $20 million in stranded debt. SCMUA called on Tetra Tech to provide an organized approach to the landfill expansion and to maximize disposal capacity by extending the landfill’s facility life for an additional 40 years.
Received the Association of Environmental Authorities’ Forward Thinking Award
Tetra Tech prepared the engineering design and permit modification application for the landfill expansion. The design hinges significantly on the incorporation of the MSE berm around the perimeter of currently active and future landfill cells. This unique MSE berm, which is the first of its kind constructed in the state of New Jersey, uses internal geosynthetic (geogrid) reinforcement, allowing a berm of significant height be constructed on a compact footprint. This design enables SCMUA to increase disposal capacity over the available footprint, making the expansion viable and offering the added benefit of eliminating the $20 million of stranded debt.
The New Jersey Department of Environmental Protection (NJDEP) approved the MSE berm in 2016. The first stage of construction, which was completed in October 2017, included construction of 2,700 linear feet of MSE berm; reconstruction of two leachate pump houses to eliminate confined space issues; and construction of new stormwater, landfill gas, and leachate controls, as well as roadway, guiderail, and litter fence.
Tetra Tech’s work included an extensive landfill gas collection and control system Master Plan update; detailed cost estimates; emissions reporting and permitting assistance; air compliance regulatory support and liaison; and construction and operations support.
Tetra Tech worked collaboratively with SCMUA staff and bond counsel to review and establish necessary funding parameters for the landfill expansion project. The work included preparing detailed project cost estimates and a projection of when expenditures would be required to match construction effort. The information formed the basis for the funding request submitted to and approved by the New Jersey Department of Environmental Protection for funding through their Environmental Infrastructure Trust. It also was used by the bond counsel for the issuance of project financing bonds.
The MSE berm, which ranges in height from 10 to 50 feet, provides additional air space above the existing landfill footprint. Because of the modest lateral component of the expansion on a unit of capacity basis, the cost for closure and post-closure care do not increase proportionately.
This office would like to commend the Authority, its engineer and construction contractor for bringing this project to a successful conclusion on time, on budget, and to exceptional quality.
Robert M Hopkins, PE, CME, Supervising Engineer, Construction Section, Bureau of Construction, Payments and Administration, New Jersey Department of Environmental Protection.
