X-/EPA United States Environmental Protection Agency Municipal Environmental Research Laboratory Cincinnati OH 45268 Research and Development EPA-600/S2-81-018 Mar. 1981 Project Summary Particle Size Variation Effects on Landfilled Solid Waste: Cold Climate Studies John V. Klingshirn An investigation was conducted to determine the effects of milled refuse particle size on landfilled solid waste. Four experimental test plots were constructed using four different particle size distributions. Each pit containing a specified milled refuse particle size was evaluated in an attempt to correlate particle size with several variables: Wind displacement of milled refuse, differential settlement of compacted milled refuse, and attraction of vectors, rodents , birds, and wildlife to the milled refuse. Data were collected over a period of 20 months. Particle size distribution curves were developed for the milled refuse used. Four breakdowns "of the composition of the raw solid waste before milling were included. Moisture content and field density were determined, and the variables correlated with particle size were studied. This Project Summary was devel- oped by EPA's Municipal Environ- mental Research Laboratory, Cin- cinnati, OH, to announce key findings of the research project that is fully documented in a separate report of the same title (see Project Report ordering information at the back). Introduction To establish appropriate criteria for design and regulation of milled refuse disposal facilities, detailed data were required to correlate the effects of particle size on operational and aesthetic variables. The purpose of this project was to evaluate the effects of particle size on the following variables: 1. Wind displacement of milled refuse. 2. Differential settlement and deterioration of compacted milled refuse. 3. Presence of vectors, rodents, birds, and wildlife at a milled refuse disposal site. Facility Design and Construction The site selected for excavation of four test cells was on a hillside in the vicinity of the City of Great Falls, Montana, landfill. The site offered a wide, unobstructed wind path and proximity to the city-owned shredding facility. Following excavation of the pits, plywood form walls were constructed inside to prevent collapse of the heavy native clay as it dried. Dimensions of each subsurface cell were 20 ft wide by 35 ft long by 6 ft deep. Eight feet of undisturbed soil separated adjacent test cells. Municipal refuse of typical composition for waste collected in the autumn throughout the Great Fallsarea was hauled to the shredding facility. The ------- solid waste shredding plant is equipped with two Heil grinding mills with vertical shafts and capacities of 15 and 20 tons/hr. Since the primary objective of this project was to evaluate various parameters according to particle size, a sieve unit was designed and fabricated to separate milled refuse particle sizes accurately. The sieve consisted of two circular trommel units mounted on a support frame. Each of the two cylindri- cal units contained three different screens. Milled refuse placed in the raised, open end tumbled down through three successively smaller screens as the trommel was turned by hand. Refuse of each particle size was collected below the corresponding sieves, loaded into 65 yd3 transfer trailers, and transported to the test site. One composite sieve sample was collected, and moisture content was determine for each load. Hammermills such as those employed at the Great Falls facility wear on a day-to-day basis, resulting in gradually increasing particle size. Special care was therefore required to ensure a reasonably consistent particle size for the surface lift of each test cell where wind displacement would occur. The shredded refuse was spread in lifts approximately 18 in. deep and compacted to maintain an in-place wet density averaging 1,000 Ib/yd3. A wide range of particle sizes occurred in the lower lifts of the test cells as a result of hammer wear, zthe sizes of milled refuse particles are given as the screen size through which 70% of the refuse passes. The particle size ranges in the lowere lifts were as follows: Test cell: inches No. 1 3Y4 to 4V2 No. 2 2%to41/4 No. 4 4 to 51/2 During placement of the refuse, test cell No. 3 was destroyed by fire when cinders were blown from a fire at the nearby landfill. After approximately 4 to 5 ft of refuse had been placed, steel plates 2 ft in diameter were installed to measure settlement in the lower portions of the test cells. The top lift on each test cell was placed over the plates and consisted of particles sized as follows (70% passing screen sizes): Test cell inches No. 1 21/2 No. 2. .41/2 No. 4 6 On completion of the refuse placement, holes were drilled back down to the plate surfaces, and a 4-in.-diameter pipe was installed above each to allow for measuring settlement. Following placement of the refuse, fencing of Vz-in. galvanized mesh was erected around each test cell. A 3-ft buffer area was allowed on the sides, and a 4-ft area was left on the ends of each test cell to collect refuse displaced by the wind. The U.S. Weather Bureau Station at Great Falls recorded the fastest observed 1 -min. sustained wind, the precipitation, and the temperature data. Displaced refuse was collected, weighed, and recorded. To permit access to birds, no top closure was provided on the test cells. Observations of bird activity at the site were made while other data were being collected. Two small holes were cut in the fencing on opposite corners of each test cell area to allow access to ground animals. Snap traps and box traps were placed to record activity of mice and rodents in the enclosed areas. A Scudder grille was employed to count fly population. Site Monitoring On November 29, 1978, when construction of the test cells and installation of the fencing had been completed, a 20-month monitoring period began. Shortly after monitoring began, snow covered the test cells and remained until mid-March. The extremely harsh winter (1978-1979) had a detrimental effect on the variables that were being monitored during this time. Heavy snow cover and frost eliminated any displacement of the refuse by the wind. Little settlement appeared to be taking place within the test cells because of the frozen ground conditions. Except for the presence of several mice, no bird, fly, or rodent activity occurred. Early spring brought considerable precipitation, which also affected the field variables. By mid-June, it was decided that if any wind displacement of the refuse was to be observed, action should be taken to loosen the bondini layer that had formed a crust on thi surface. A rototiller was used to scarif the surface of the test cells. Thi elevy'ion of the reference points on th( surface of each test cell was thei redetermined and again monitored fo settlement. Monitoring of the othe variables continued withou interruption. Weed growth, a variable not originalh monitored, was initially observed on th< test cells in May 1980. Weed growth continued throughout the summer t< the point where refuse displacement b\ wind was negligible. Most of the growth occurred in test cell No. 1 and the leas in test cell No. 4. Based on data analysis of the monitored variables, it was concludec that the particle size of milled refuse becomes important only if winds exceec 10 mph on a regular basis (the speec reported by the U.S. Weather Bureai Service as the fastest observed 1-min sustained wind). In such a case, largei particles will be displaced in greatei quantities than the smaller particles Settlement and deterioration of millec refuse compacted to a density of 1 ,OOC Ib/yd3 does not proceed rapidly during the initial 18 months. No difference appears to exist in the settling and deterioration rates between large and small refuse particle sizes, nor does there appear to be any correlation between particle size and the attraction of flies, mice, or birds. The quick formation of a surface bonding layer most likely accounts for the lack of wind displacement, vectors, rodents, and birds. Compaction to achieve a relatively high density may account for the absence of rapid deterioration and negligible settlement of the milled refuse. The full report, submitted in fulfill- ment of Grant No. R805012, by Thomas, Dean and Hoskins, Inc., Great Falls, Montana, under sponsorship of the U.S. Environmental Protection Agency, was authored by L David Heckler. ------- John V. Klingshirn was an Engineering Technician with the U.S. Environmental Protection Agency, Cincinnati, OH 45268. Richard A. Carnes was the EPA Project Officer. The complete report, entitled "Particle Size Variation Effects on Landfijjed Solid Waste: Cold Climate Studies," (Order No. PB 81-152 050; Cost: $6.50, subject change) will be available only from: National Technical Information Service 5285 Port Royal Road Springfield, VA 22161 Telephone: 703-487-4650 Stephen C. 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