APPORTIONING SLUDGE VOLUMES DISPOSED IN A LANDFILL
1
Andy Davis, P. DeCurnou, S. Helgen, and J.van Middlesworth
Geomega, 2995 Baseline Road, Suite 202, Boulder, CO 80303; 1Phone: (303) 938-8115; 1E-mail:
andy@geomega.com.
Sludges from a galvanizing operation and a tile manufacturer were sent to a Texas landfill
over a 17-year period. Closure was complicated by the estimated $14m cost, so a two-part solution
was proposed. First a cheaper, less complicated (yet effective) closure plan received regulatory
approval while cost allocation proceeded in parallel. The closure plan was modified (with
regulatory approval) to avoid sludge stabilization because the caustic soda and lime added to both
sludges resulted in immobilization of lead and zinc (the compounds of concern). In addition, the
siliceous nature of the material rendered further compaction prior to closure unnecessary. Waste
apportionment used the end member materials to identify the mineralogic and chemical signatures
of each that were used to develop a three-component (Pb/Zn/Fe) mixing model. The proportions of
the two wastes in 201 samples of mixed sludge in the landfill were computed, the spatial
distribution kriged, and the results summed to apportionment waste volumes between the two
entities. The parties were able to settle when the landfill closure costs were reduced to ~$4m and
the mixing model showed that 93% of the waste was from the tile manufacturer and 7% from the
galvanizing operation.
Key words: sludge, closure plan, waste apportionment