Remediation planned for landfill
Alexis Barker
NLJ News Editor
The city of Newcastle is completing an agreement with the Wyoming Department of Environmental Quality for the city’s Landfill Remediation Program, according to city engineer Mike Moore. He said the project, led by the DEQ, will address environmental concerns posed by the landfill.
“These concerns include capturing and treating leachate originating from the landfill and also addressing methane issues,” Moore said.
“Leachate is the fluid percolating through the landfills and is generated from liquids present in the waste and from outside water, including rainwater, percolating through the waste,” according to www.sciencedirect.com.
As previously reported, in 2019, methane in one of the wells near the landfill had reached levels that are considered a health and safety risk. Caroline Brewer, project geologist with Trihydro Corp., reported to the Newcastle City Council on Feb. 4, 2019, that the methane was 100% a lower explosive limit and 21% methane, creating a health and safety risk at the Weston County Sportsman’s Club and shooting range.
Trihydro is a Laramie-based engineering and environmental consulting company hired by the state to work on landfill remediation across the state.
“This was not unanticipated. We recognized the problem in the past,” Brewer had said. “This is a serious concern. The well is way above the limits and is a potential explosive hazard, may introduce methane into a closed structure, and you also have asphyxiation. These are the things you have to think about when you have methane concerns.”
The landfill, which was operated from sometime before 1945 until its closure in 1989, covers 38 acres of land near the sportsman’s club and contains an estimated 700,000 cubic yards of waste.
Trihyrdo’s scope of work at the landfill included methane monitoring, groundwater monitoring, statistical analysis, evolution of remedial
alternative, preliminary design, cost estimates and reporting to the city and state.
Brewer also reported in 2019 that water samples had shown that oxidation reduction is a potential problem, indicating that there is some potential for chemical reactions.
“This is important because we believe there is a problem,” Brewer had said. “The reports are telling them there is a reaction taking place in the water.”
Marge Bedessem, senior environmental engineer with Trihydro at the time, said that most of what was found in the water was solvents and that they were not exceeding groundwater standards.
Based on Trihydro’s studies, the goals presented to the City Council in 2019 to be addressed in the remediation plan were methane control to reduce health and safety risks and addressing the impacted groundwater.
The project to complete the remediation has an estimated cost of
$2.4 million, based on estimates from the Remediation Alternatives Evaluation Report completed by Trihydro. The proposed initial agreement amount is $1.8 million from the Landfill Remediation Program and $600,000, or 25% of the total costs, from the city.
According to Moore, the city does not have to come up with the full $600,000 immediately. He noted that, to date, the DEQ has footed the costs through the remediation program.
“It (the city) initially only needs to provide its 25% share for the studies and design work. An initial budget estimate would be $400,000 for that work, or $300,000 from LRP and $100,000 from the city,” information provided by Moore says.
As the work progresses and the cost estimates are refined, the city would then be responsible for the additional funding before the construction, or other contracts, are entered.
“As the design gets completed, we should get more accurate cost estimates for construction and could adjust the remediation agreement budget, if needed,” Moore said. “Bidding the construction project(s) would be another point at which the budget would be re-evaluated and adjusted, if needed. After the systems are constructed and we evaluate any need for additional evaporation ponds, or other changes, we would adjust the budget to account for those changes and to accommodate additional years of OMM (operation, maintenance and monitoring).”
A breakdown of the projected costs provided by Moore shows that the initial phase of the project, following the studies that have been completed, will cost roughly $1 million. This phase will include the design and construction of the groundwater alternative two, an interceptor trench at the landfill boundary.
“The interceptor trench’s purpose is to capture leachate from landfill 1,” Moore said. “The leachate is groundwater that has picked up soluble matter from the landfill.”
After that, they will move into the design and construction of groundwater management option b, with an estimated cost of $900,000.
“This is estimated down from the report estimate to account for the initial construction of smaller-size ponds. We would construct ponds, likely two, totaling about two-thirds of the total needed pond area, estimated in the report,” information from the DEQ says. “There is much uncertainty in the actual groundwater flow rate, and thus much uncertainty in the needed pond area to store and evaporate it.”
These initial ponds would allow for water to be stored for a year or two while the actual groundwater flow rates and amounts are determined. At this time, if additional pond area is needed, then plans can be made.
“Initially, around 5 acres is to be utilized and adjusted, if needed,” Moore explained. “The purpose of the pond is to evaporate excess groundwater captured in the interceptor trench.”
“The pond works by providing surface area to evaporate groundwater from the interceptor trench,” he continued. “The pond is lined, and given enough time, sediment will build up with contaminants in the bottom, which will need to be removed and properly disposed of.”
He noted that the potential side effects of the evaporation system are odors downwind.
After the pond project is complete, a passive landfill gas (methane) venting system will be designed and constructed with an estimated cost of $100,000.
According to waste360.com, a traditional passive landfill gas venting system is installed to control gas migration at a landfill. The system relies on vertical pipes to collect and channel the gases to vents, which release the landfill gases.
Once the systems are implemented, roughly $400,000 will be spent on additional studies and testing, including nature and extent studies and asbestos-containing materials studies. Of this, $100,000 will go toward the first year of operation, maintenance and monitoring of the site and newly built systems, according to the information provided by Moore.
Once the agreement is complete, a consultant should be selected in the next couple of months and then the project will be designed. The city will be one of three votes in the consultant selection process, Moore said.