Biosolids Removal and Reuse
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Client—City of Longview, Washington
The West Longview Lagoon Wastewater Treatment Plant (Lagoons) consisted of four Facultative Sludge Lagoon cells with a total water surface area of 46 acres. Active use of the Lagoons as a wastewater treatment facility was terminated by the City.
The closure plan for the Lagoon treatment facility included removal of the biosolids that had accumulated in the lagoons over the past 30 plus years. Gibbs & Olson was hired by the City to prepare a biosolids survey and sampling plan. The plan included estimating the volume of biosolids in the lagoons and determining if the biosolids met Class B requirements for beneficial reuse.
Sampling and lab testing determined the biosolids did meet Class B requirements and could be beneficially reused on permitted agricultural land. Based on the survey work performed, the volume of biosolids was estimated to be 4,700 dry tons.
Gibbs & Olson worked with the City to prepare a Request for Proposals (RFP) for removal, screening, dewatering, transport, and land application of the biosolids. The selection criteria in the RFP was based on price, relevant experience, proposed work plan, and the ability to remove all biosolids within a specific timeline.
The Engineer’s Estimate was $2.5 million and the City received six proposals from firms from across the United States. The proposal with the lowest price was $1.8 million and the average of the six proposals was $2.6 million.
The contractor completed all removal work within the needed timeframe and 4,520 dry tons of biosolids were removed and land applied. Gibbs & Olson worked with the City and contractor to document that the biosolids were adequately removed such that Ecology terminated the City’s biosolids permit.
The final project cost was 72 percent of what the City anticipated for the project and the amount of biosolids removed was 95 percent of the volume estimated from Gibbs & Olson’s survey work.