Project Overview
Methane gas is a by-product of the decomposition of waste at a landfill. Ordinarily, the gas is collected and contained in wells that the Authority later destroys. However, the Authority determined there was a beneficial reuse of the gas that was possible and entered into a partnership with private developer, Aria Energy. Together, they built a plant at the landfill site that takes the methane gas generated by the landfill waste and converts it into electricity. Our project consisted of the construction of approximately 3,000 linear feet of HDPE piping, valves, and existing tie- ins. The project also included the installation of 22 vertical landfill gas extraction wells with pneumatic pumps and well heads, and the excavation and non-destructive testing of an existing section of landfill liner and repair defects.
CHALLENGE
Our team was tasked with the installation of a 12” gas main without damaging the existing 6” gas main in the same trench. This proved challenging, as our team learned about multiple locations where existing pipes were undocumented on any drawings. An additional challenge came to light when the team located the existing main and found it to be 18”. The project plans had shown the main to be 12”. The project schedule was already constrained and this newly discovered condition presented potential delays to the project to obtain the correct materials.
SOLUTION
During the excavation, our team took extra time and care to ensure we did not destroy the existing 6” HDPE pipe. At every location we knew there was a crossing, which necessitated further investigation to identify all existing pipe in the ground. Our crew determined that hand digging would be a preferable method to uncover all existing pipe. 3,000 linear feet of pipe was installed and tested before making the final tie-in. To solve the issue of materials, our team worked with the Authority, who already had a portion of the piping necessary to complete the project in stock. We were able to supply the remaining materials. The team was able to successfully maintain and meet the aggressive completion date without delay.
RESULT
With landfills, environmental interests are at the forefront of public concern. Landfill gas-to-energy projects have helped the Authority’s commitment to fostering a more environmentally friendly site. Despite the unique and unforeseen site conditions that could have delayed the project, our team successfully completed the project on time. With increased gas collection from the landfill, the Development Authority was able to increase their output of electricity, by 25 percent. The increase in landfill gas collection, made possible by upsizing the collection and transmission pipeline, also made the wellfield balancing much easier and more effective.
