Owner/Client
Huron County
Location
Willard, OH
CEC Services
- Groundwater Monitoring and Assessment
- NPDES Permitting Support
- Stormwater Sampling and Permitting
- Environmental Monitoring/Compliance
- Hydrogeologic Site Investigations
- Landfill Gas Management
- O & M of Control Systems
- Construction Services
Owner Objective
Huron County, Ohio operates a municipal solid waste transfer station and maintains a landfill that closed in the early 2000s. While the location of the landfill is remote, explosive gas monitoring is required due to the adjacent transfer station operations and several nearby residential properties.
The existing gas extraction system has been in operation for nearly 30 years, but the effectiveness of the system has decreased over time. Explosive gas monitoring probes around the landfill perimeter routinely detected methane. An Ohio EPA comment letter, noting several deficiencies to be addressed, initiated an assessment of the existing gas extraction system.
CEC Approach
CEC conducted a thorough assessment of the existing gas extraction system and migration potential near monitoring probes that historically detected methane. CEC found a number of extraction wells were silted in, which was likely due to over-applying vacuum during seasonally wet conditions.
CEC recommended reinstalling select extraction wells with an improved filter screen design to minimize clogging potential, adding wellheads at all extraction wells to better regulate vacuum, and making system adjustments to balance pressures. Several existing vent and probe locations were also enhanced with passive turbines affixed to the vertical risers. Additional/replacement explosive gas monitoring probes were also installed for more thorough monitoring of occupied structures adjacent to the limits of waste.
Throughout the project, CEC worked closely with the Ohio EPA to maintain compliance and keep the site out of assessment, avoiding additional investigations and gas extraction system expansion.
Since the completion of the improvements, perimeter gas probes have essentially been non-detect. A comprehensive revision of the Explosive Gas Monitoring Plan was completed and approved by the Ohio EPA, resulting in a reduced monitoring frequency from weekly to quarterly.
