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Landfill Temporary Cap Project

Jun 16, 2015

By Sara Verrillo

ACUA is installing a temporary cap to cover approximately 30 acres of landfill space.

The temporary cap will prevent gas from escaping the sides of the landfill and direct it towards the existing gas collection systems. It will also keep water from infiltrating the landfill, which will reduce the overall production of gas as well as prevent the accumulation of leachate along the side slopes – all actions that will decrease odors.

The project will take roughly 3 months to complete and will cost approximately $2 million.

How It Will Work

The temporary cap is a reinforced LLDPE laminate liner that will cover several of the open landfill cells that are no longer in use.

Currently, without a cap on the landfill, rain enters the cells and creates leachate, which is water that’s been contaminated after seeping through trash.

The rain also makes the trash break down at a faster rate than when the landfill is dry. As the trash breaks down, it creates odorous gases like methane. The faster the trash breaks down, the faster these gases are created.

At the same time, large amounts of rainwater also overwhelm the landfill gas collection system.

With an increase in gas production and a decrease in collection, odor becomes an issue.


Examples of a temporary cap at the Cumberland County Improvement Authority Landfill 

By installing the cap, the rain will not penetrate the landfill, therefore (1) reducing leachate and the costs generated from treating and collecting it; (2) reducing landfill gas; and (3) reducing odors.

Each time there is a major rain event, landfill crews spend many hours fixing the landfill side slopes that are washed away by water. Between materials and man hours, the expense of maintenance adds up.

The temporary cap will cover the side slopes of the landfill that are the most prone to erosion from rainfall, which will decrease maintenance costs.

The cap will also lead to increased efficiency in gas collection. Currently, gas can escape through the exposed sides and the collection system since collection wells are located and tuned so they do not suck in too much fresh air. By covering the side slope, the gas has nowhere to escape, and the gas collection system can collect with a greater vacuum since fresh air cannot be sucked in.

The cover will prevent landfill gas from escaping and increase the efficiency of collection.

Construction Status

Construction of the temporary cap began the week of June 15 and is scheduled to be completed by September. Stay tuned for updates as the project progresses.


Preconstruction work on ACUA landfill's side slopes in preparation for the cap.



UPDATE: August 2015 - Temporary cap is almost complete



UPDATE:  September 2015 - Temporary cap is complete. As you can see from the image above, the rain that would normally infiltrate the landfill cell or wash away the side slopes now runs cleanly off the temporary cap instead.