SWAC examines scenarios for Coffin Butte landfill capacity and longevity

Benton County SWAC members reviewed a draft section on landfill size and life Feb. 8 that outlines possible scenarios affecting Coffin Butte's remaining capacity and urged the work group and county to hire experts to test key assumptions.

The A1 subcommittee's draft separates technical questions into size, capacity and longevity and lists factors that could lengthen or shorten landfill life, such as population growth, recycling and diversion policies, fires or economic cycles. The draft includes scenario graphs intended to show how different futures (baseline operations, cap removal, approved expansion, increased diversion) would affect landfill life year-to-year.

Members noted limitations in available proprietary data. "Their projection saying that they're going to be able to maintain that high rate of intake ... we can't really examine the assumptions," one member said of Republic Services' projections. Members suggested the county request or require more detailed intake and contract data where possible and to commission experts (economists, geologists, engineers) to evaluate scenarios, noting that scale-ticket data and hauler contracts could inform modeled inflows.

Members also discussed differences in terminology: an operator may report a cell as "closed" while DEQ records show a cell is not yet closed from a regulatory standpoint. The group agreed that expert analysis should address closure definitions, settlement and technical factors that influence usable airspace.

Ending

SWAC members recommended the work group incorporate expert analysis and clearer sourcing into the landfill-size section, and they urged members to submit written, page-referenced comments to inform hiring and scope for consultants.