An exciting research project is underway related to the development of compaction procedures for optimum placement of wastes in municipal solid waste landfills. The investigation is funded under the C3RP (California Central Coast Research Partnership) program and in collaboration with the Municipality of Riverview, Michigan. As compared to soils, for which compaction theories, trends, and methods are well developed, a fundamental understanding of waste compaction processes or widely acceptable guidelines for industry use are currently not available. The field study, which incorporates GPS technology, is being conducted at the Riverview Landfill to identify the baseline parameters and conditions that control compaction of wastes.
Laboratory tests have been conducted at Cal Poly as part of the study to investigate the fundamental influence of moisture addition on compaction characteristics for manufactured wastes. Large-scale compaction molds are being used for the tests and the procedures are similar to the modified Proctor compaction test for soils. Custom-built equipment was constructed by student research assistant Nick Oettle for the test program. Representative waste has been “manufactured” for testing by assembling representative fractions reported by the U.S. EPA. Index compressibility tests are being conducted to correlate stiffness of waste to water content conditions used for compaction. The laboratory tests provide baseline conditions for comparison to the full-scale field compaction tests.
Full-scale field tests are conducted by compacting 100 tons of waste in a controlled test plot that is part of an active landfill cell. Varying amounts of water (up to 8,000 gallons) are added to evaluate the influence of moisture content on waste compaction efficiency. Duration of compaction (number of compactor passes) allows for evaluating influence of compaction effort. A GPS system that is mounted on the waste compactors is used to make the required geometric calculations for determination of as-placed waste densities and compaction efficiency of wastes in the test program. The system provides a continuous topographic map of the compacted waste surface in time. Integration of the GPS system allows for determination of geometric constraints at a scale that has not been previously possible. The landfill operator has contributed significant resources to the study including allocation of the test plot, use of compaction equipment, and field personnel to assist with compaction and data collection. Tests have been conducted in Michigan by Cal Poly researchers (graduate student Shawna VonStockhausen and Professor Jim Hanson) to determine incoming moisture content of wastes, surface temperatures of active zone of waste filling, localized unit weight determinations, and global unit weight determinations using GPS.
The results to date indicate that significant improvement can be gained in compacted unit weights of wastes by modifying compaction conditions (moisture content and compactive effort). This research will be used to develop guidelines for waste compaction that can be used to maximize the amount of waste that can be disposed in a given volume. This research project is separate from, but complements ongoing Cal Poly research at 5 other partner landfill sites in Michigan, New Mexico, Alaska, Canada, and Australia.
For More Information
Dr. Jim Hanson