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
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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.
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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. James is the EPA contact and can be reached at:
Municipal Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
* U.aaOVBINilINTMWITINOOFnO«:1«»1-757-012/7024
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Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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