John F. Hartwell, Ph.D., PE., CHMM, and Senior Consultant at SCS Engineers recently successfully defended his dissertation and earned his Ph.D. An abstract of Dr. Hartwell’s dissertation follows:
METHODOLOGY FOR ASSESSING MUNICIPAL SOLID WASTE USING A LARGE-DIAMETER BOREHOLE
LTC John F. Hartwell, Ph.D., P.E.
University of Nebraska, 2015
Municipal solid waste (MSW) landfills are permanent repositories of society’s non-hazardous wastes. Landfill facilities are becoming harder to site, resulting in increasing pressure to maximize the use of available airspace. Increasingly, this results in developing additional airspace by way of vertical expansion. This expansion imparts greater stress on the landfill mass and the containment infrastructure.
The engineer’s understanding of the geotechnical properties of MSW has been limited to sampling of relatively shallow test pits and reconstitution of disturbed MSW samples in the laboratory. Deeper assessment using small diameter borings is difficult and produces poor low volume samples for ex-situ testing. Some researchers have synthesized MSW with obvious limitations. Landfill failures have provided opportunities for back calculation of MSW properties including shear strength, but these estimates are based on limited understanding of unit weight and moisture content with depth.
The recent trend for the harvesting of methane produced by the anaerobic degradation of MSW has resulted in the need for nearly full-depth, large-diameter, landfill gas collection wells. Prior to completion, these boreholes provide excellent opportunities for directly observing and measuring the condition of MSW in its buried, variably degraded state at depths that are far greater than previously accessible.
The large diameter MSW gas well borehole assessment methodology presented in this paper is shown to be an efficient and valuable means for characterizing MSW. This means that the cost of the assessment is relatively low as the drilling costs are negligible and therefore limited to the cost of labor to sample and perform field observation and laboratory testing. The assessment methodology, which includes scaled full coverage photography and videography, allows precise analysis of a number of geotechnical properties such as wet and dry unit weight, moisture content, specific gravity, void ratio, % saturation of MSW and buried soil layers throughout the depth of the borehole. Further, MSW constituents and biologic degradation can be measured. The orientation / alignment of tensile reinforcement within the waste mass is readily observable. Zones of perched leachate and the effects of mechanical creep on borehole diameter can also be measured.
Learn more about MSW Landfill Services from SCS.