-------
With the remainder of the stations, the highest takes occurred on the
edge of the test site. This led to the conclusion that rats preferred
the peripheral area of the site more than they preferred either milled or
unprocessed refuse cells.
In the next phase, the bait stations were moved to new locations. If
the stations did not draw rat activity with them, it would indicate that
the previous areas of activity were so desirable that rats would not leave
them to seek out a bait station. If the new stations did draw activity,
it would be important to note which cell type — milled or unprocessed ~
had the greater increase. Since the stations were identical, the rats
would base their choice of a new site on considerations other than the
presence of a bait station.
Nearly all of the original stations were removed and nine stations
were established in the central area, where previously there had been
negligible activity.
The results showed that rat activity was drawn readily for distances
up to 100 feet. This migration led to much test drilling, resulting
eventually in 18 new burrows. Of these, 12 were on the two unprocessed
covered cells while six were on one of the four uncovered cells. Thus,
it appears that the unprocessed covered cells provided better drilling
and living conditions than did the milled cells (minimum of 6 inches
compacted cover).
The fact that rats were drawn by the bait in the second phase does
not negate results from the first phase, since the rats were undoubtedly
dependent on the bait after 70 days of the first phase.
The final phase of the rat field tests involved adding poison
to the bait and observing the rate of kill. To assure a thorough
kill, the bait stations were returned to their original locations
and were replenished with nonpoisoned bait. This was continued
for 3 weeks prior to poisoning to foster dependency by the rats
on the bait stations. Three to nine days after the addition of
5-percent-by-weight anticoagulant rodenticide to the bait, the
kill was essentially complete. The rate of decrease of bait take
was higher on the milled cells than on the unprocessed cells. This
may or may not properly suggest that rats frequenting the milled cells
were more dependent on the bait for food than were rats associated
with unprocessed refuse.
It was noted during these tests that any irregularity in the
surface of a cell, whether milled or unprocessed, was likely to lead
to test drilling or a burrow. Erosion of cover material, for example,
produces irregularities which may lead to test drilling. In milled
uncovered cells a break in the surface is not as likely to occur, and
if it does occur it is not as likely to result in burrows. This is
because the interior of milled cells offers only more of the same material
as is found on the surface. Many signs of test-drilling without burrow
development were found on milled cells.
93
-------
The field studies suggested that milled refuse without cover
was less attractive to rats, especially for burrow development, than
was unprocessed refuse covered with soil. It remained to be shown,
however, whether milled refuse by itself would attract rodents..
To determine this, several tons of milled refuse were placed in a
remote location within a Madison residential area. A snow fence
was set up to enclose the refuse and discourage spreading by children.
The site was checked periodically for signs of rodent activity.
No activity was observed at any time and after 12 months, the test
was terminated.
The above test could not be considered conclusive, since there
was no assurance that rats were living in the area, nor was there
reason to expect that any rats nearby would leave their previous
surroundings in favor of milled refuse. Consequently, a similar
pile of milled refuse was placed in a remote location at the 01 in
Avenue landfill where rats were known to be present. After several
months, no signs of activity were noticed, and the test was ended.
It is felt that the combination of field tests on rats and
refuse provides rather conclusive evidence that milled refuse as
processed at Madison will not result in rat infestation at a land-
fill. The fact that no rats have been sighted in the landfill in
over four years since the rats were poisoned, and that a mother duck
has felt sufficiently secure to develop a nest, lay, and hatch eggs
near the center of the site, supports the findings of the study.
Since the conclusions of the field test were strictly applicable
only to Madison, cage tests were performed in which rats were forced
to depend solely on milled refuse for sustenance. It was felt that
the results of these supplementary tests would have wide applicability
since they would show that rats either can or cannot survive on milled
refuse.
The tests were conducted at the Purdue University Rodent Test Center
at Lafayette, Indiania (Figure 48). The facility is maintained jointly
by the school's Rodent Control Fund and the United States Department of
Interior for testing baits and poisons. Some 750 Norway rats (Rattus
norvegicus) are kept in two large areas where they can live under nearly
normal conditions until they are trapped for test purposes.
Prime Norway rats, each weighing over 200 grams, were used for
the tests. Five males and five females were placed in each test cage.
The metal cages were 3 x 7 x 2 ft. high (Figure 49).
Three test series were run. For the first series, the test
cages were kept inside at 70 degrees F and in total darkness. For the
other two series, the tanks were kept outdoors under mild summer
conditions; these tanks were covered to maintain darkness. All
tests were conducted to a logical conclusion or over a 15-day
period, whichever came first.
-------
Figure 48. Rodent Test Center for Norway rats at Purdue University,
Lafayette, Indiana.
Figure 49. Typical cage used in studies conducted at Purdue University,
95
-------
The first series was run in 1969, when fresh milled refuse
with about 15 percent (wet-weight basis) garbage content and two-
year-old milled refuse of approximately similar garbage content
were used. All refuse samples were sent to Purdue from Madison.
Some 30 Ibs. of each type of refuse were placed in separate test
tanks, replenished as necessary to assure the availability of over
three times the minimum daily nutritional requirements of the rats
at all times. For purposes of calculation, only the food wastes or
garbage content of the refuse was considered to be edible by and
nutritious for the rats.
In the tank with aged"mi lied refuse, the rats dug holes and
scattered the heavy, compact material in search of food. All
animals showed weight loss by the end of the fourth day. During
the fifth night, one animal was cannibalized. All but one animal
had been eaten by the end of the test, and the survivor died the
next day. The results were virtually identical when the test was
repeated.
Although there appeared to be more available food in the
freshly milled refuse than in the aged, it was not sufficient to
sustain the rats. During the first test, two animals were cannibalized
on the eleventh night. Only three animals survived the 15-day test,
and they were so weak that they had to be killed. Again, similar
results were obtained during a replication of this test.
The conclusion of this series of tests is that freshly milled or
aged milled refuse, as received from Madison, cannot sustain a rat
population.
In the next test series conducted in 1972, freshly milled refuse
samples with various fractions of garbage were used. The four levels
of garbage content tested were 17, 32, 47, and 59 percent wet garbage
on a wet-weight basis. No animals died as a result of starvation
or cannibalism during this series of tests. It was quite obvious,
however, that the samples sent to Purdue had been poorly milled, or
perhaps were not milled as a result of procedural problems during
sample preparation at Madison. Thus, large chunks of putrescrible
matter which could be used as food were available to the rats, and they
survived. Obviously, then, particle size is of special importance in
determining the suitability of milled refuse to sustain rats.
The third series, conducted later in 1972, was designed to
correct the problems encountered in the previous test series.
Special care was taken to obtain a representative milled product
for the two samples, which contained approximately 10 and 20 per-
cent wet garbage on a wet-weight basis.
In the 20 percent cage, all the rats died within 10 days, in
the 10 percent cage, five animals survived the full 15 days and one
dominant male seemed to thrive quite well, although the others were
very weak. Although these results are not quite as conclusive as
other tests had been, the results of this final series still leads
to the conclusion that rats cannot survive indefinitely on a diet
96
-------
consisting only of milled refuse containing up to 20 percent garbage
on a wet-weight basis. Based on this fact, there is very little
possibility of rat infestation and survival in a milled refuse
landfill.
Since the fall of 1966, when the rats at the 01 in Avenue test
site were poisoned, only two or three rats have been observed on the
landfill or the vicinity. Many City and University personnel regu-
larly inspect the Olin Avenue site but since 1968 have observed no
burrows that can be attributed to rats.
It has been necessary to institute a rodent-control program at
the milling plant, however. Rats and mice are continually transported
to the plant in refuse packer trucks and must be poisoned on a regular
basis. No migration from the mill building to the landfill has been
observed.
Flies:
Field studies at the Olin Avenue test site as well as laboratory
studies were conducted in the summers of 1968 and 1969 to evaluate fly
problems which might arise from not covering milled refuse in a landfill.
A comparison of the relative numbers of flies on or near each of
the two cell types at the Olin Avenue landfill was made by direct count.
The testing was done using a Scudder Grille to attract the flies for
counting (Figure 50). This is a standard test procedure to evaluate fly
populations in barns, etc. The results indicted no marked differences
in the number of flies on milled uncovered or unprocessed covered refuse
cells.
Another study was designed to determine the relative numbers of
flies emerging from comparable amounts of milled and unprocessed refuse
(Figure 51). Screened cages were placed over similar piles of each kind
of refuse, about 1000 pounds of refuse in each case, and the files in
each cage were counted periodically over the 1 month duration of the test
(Table 15). The cage over the unprocessed refuse (without cover) reached
a population of some 4000 flies while the greatest number observed in the
cage over milled refuse was 15.
To determine whether the lack of flies emerging from milled refuse
was due to lack of viable maggots or to the inability of milled refuse
to support flies, 1200 flies and 2000 maggots were introduced into the
cage over a second pile of milled refuse. In this case, the flies
survived for about a week, but the maggots were unable to complete their
life cycle and thus did not produce more flies.
97
-------
O)
in
3
4-
OJ
s_
I/I
o;
o
o
Q.
-a
T3
-o
rs
u
oo
o
LD
QJ
S_
3
cn
la-
98
-------
f.
CTi
CO
CTi
to
O)
4J
.0
(O
s_
3
CO
>>
«*I
cn
•r-
S-
3
T3
•O
Ol
CO
3
CO
O
O
o>
c
OJ
CD
S-
o
CO
Lf)
O
i-
3
cn
99
-------
TABLE 15
RESULTS OF FLY CAGE TESTS (1969)
Days
0
1
6
12
15
20
21-30
Cage 1
Unprocessed, Compacted
More flies than cages 2 or 3
Approximately 1000 flies
Approximately 1000 flies
Approximately 4000 flies
Remaining at large number
Remaining at large number
Number beginning to decline
Cage 2
Milled
-
10 flies
none
1200 adult flies and
2000 maggots introduced
Approximately 100 flies
2 flies**
none
Cage 3
Milled
-
15 flies
none
none
* none
none
none
* Indicates most adult flies survived.
**Indicates maggots were unable to complete life cycle and that initial
1200 adult flies had died.
100
-------
Continuing this line of investigation, samples of fresh and
6-month-old milled refuse were used for laboratory studies to determine
whether this material can support flies. Approximately 1000 fly eggs
were introduced into separate cartons containing fresh and aged refuse.
Similar cartons had no eggs added. The refuse was kept moist and humid
(40 to 70 percent relative humidity) and warm (80 degrees F) for 3 weeks.
These conditions are commonly cited by entomologists as "optimal" for
growing flies.
With the freshly milled refuse to which no eggs were added, no flies
emerged throughout the test. In the carton of fresh refuse to which 1000
eggs had been added, approximately 1000 flies emerged at the end of 3 weeks.
Thus, when fresh milled refuse is subjected to optimal environmental
conditions, it is capable of supporting the growth of flies.
With the 6-month-old refuse to which no eggs were added, a few flies
did emerge, but these were not houseflies. They probably arose from eggs
or maggots picked up by the refuse while it was in the landfill. The
aged refuse was not able to support the life cycle of the added eggs, for
approximately the same number of flies emerged as compared to the carton
of aged refuse to which no eggs were added.
Thus, under "optimal" conditions, including controlled refuse moisture
content and proper temperature and humidity, fresh milled refuse can
support the fly life cycle. Aged milled refuse, however, is a poor medium
for housefly development even under optimal laboratory conditions.
It remained to show whether maggots are killed during passage through
a hammermill. On two occasions, the Gondard mill was cleared by stopping
the feed conveyor. In the first trial, 6000 mature housefly maggots were
scattered on about 100 Ibs. of refuse on the conveyor. This refuse was
then run through the mill. The second trial was identical, except 12,000
maggots were used. The emerging refuse was examined for living maggots.
The milled refuse was then exposed to ideal environmental conditions in
the laboratory to insure that any viable maggots which were overlooked
would emerge as flies. In refuse from the first trial, no flies emerged;
in the second 84 flies were counted.
It is possible that some maggots were lost in the mill, although care
was taken to avoid this. The most likely explanation for the large
decrease in viable maggots is that most of them were macerated during the
milling process.
The fly studies showed that there are several mechanisms which would
lead to reduced fly populations at landfills with milled refuse without
cover. First, the milling process itself destroys the great majority of
maggots. Second, freshly millled refuse can support the fly life cycle
only under optimal environmental conditions that are not normally found
in a landfill. Finally, when refuse has aged for several months, even this
ability under optimal conditions is destroyed.
N«t one of the tests described above provides absolute proof that no
fly problems will ever exist with milled refuse. Taken togetner, however,
the evidence from these tests becomes quite conclusive. Five years of
experience at the landfill support the conclusions of this study, for
there have been few flies reported on the milled refuse at the site.
101
-------
Vegetation
Trees:
A study was initiated at the 01 in Avenue site in 1969 to determine
the ability of milled refuse to support tree and shrub growth. The type
and thickness of cover soil as well as tree and shrub species were
varied to determine which combinations gave the best growth. Experimental
plots were established on both milled and unprocessed refuse to determine
if there were any differences in growth due to the composition of the
underlying refuse. Additional plots were established to determine the
effects of fertilizer on the growth of tress on the landfill. Ten species
of trees and shrubs were planted.
Growth measurements were made on all ten species planted, but only
white ash, jack pine, red pine and buffaloberry were selected for
representative analyses (Table 16).
Soil type was found to be a significant factor in producing growth
differences in a single year. Most of the species other than jack pine
increased in height and diameter more on topsoil than on subsoil. This
is reasonable because the low fertility of the subsoil was probably
adequate for the low-demanding jack pine.
Many trees (19 percent) died the first year of the study. The much
greater initial mortality on the unprocessed site as compared to the
milled site is attributed to differences in the condition of the
planting stock and soil at the time of planting. Greater initial
mortality occurred on the unprocessed topsoil block than on the unprocessed
subsoil block; this difference can be partially explained by the greater
weed competition on topsoil than subsoil.
Studies of plant growth on spoil banks have indicated that most tree
mortality occurs the first year after planting, with very small increases
in mortality occurring in later years. The results of this study disagree
with this finding. Little additional mortality occurred on either site
until the fall and winter of 1971-72 when a rapid upsurge in mortality
(65 percent in total) occurred; this later mortality was attributed to
a lack of adequate soil aeration. One reason for this hypothesis is that
all species survivied better as of 1972 on topsoil on the milled site
while all species did better on subsoil on the unprocessed site. The
better survival on topsoil on the milled site is probably because the
topsoil had 15 cm. more soil cover than the subsoil. This extra soil
acted as a buffer between the tree roots and gases produced by the
decomposing refuse. Since the trees also had better survival on the
unprocessed than the milled site, it was suspected that gas production
by milled refuse was greater than for unprocessed refuse, as discussed
earlier in this report.
102
-------
TABLE 16
EFFECT OF PLANTING CONDITIONS ON TREE GROWTH (PERCENT)
(November 1970 to September 1971)
Plot*
Milled (A)
(B)
(C)
(D)
(E)
(F)
Unprocessed (A)
(B)
(C)
(D)
(E)
(F)
White Ash
Hts. Diam.
(D
43.0
23.5
53.7
48.4
50.5
27.6
61.7
93.8
71.1
41.7
19.7
(D
51.3
28.4
61.5
47.6
70.4
15.1
38.2
54.9
69.2
71.4
24.6
Red Pine
Ht. Diam.
2.8
2.8
1.6
11.1
14.8
18.9
9.9
10.1
11.2
13.0
(2)
(2)
8.0
3.5
10.6
19.6
18.6
20.6
5.5
13.0
8.8
27.2
38.0
9.0
Jack
Ht.
29.3
41.6
12.8
(3)
19.0
25.8
6.6
11.1
12.914
29.1
24.6
17.3
Pine
Diam.
19.7
34.2
9.4
(3)
4.7
17.8
7.6
18.8
.6
10.6
16.7
15.1
Buff
Diam.
32.6
27.5
6.7
30.2
33.5
35.7
57.6
55.6
67.8
39.2
87.7
12.3
* Plot A - 15 cm. subsoil
B - 30 cm. subsoil
C - 45 cm. subsoil
D - 45 cm. subsoil
E - 30 cm. subsoil beneath 15 cm. topsoil
F - 15 cm. subsoil beneath 15 cm. topsoil
Notes 1. No measurements taken
2. Tops of trees were damaged, limiting growth,
3. All trees had died by September 1971.
103
-------
Compaction caused by grading operations on the study sites greatly
influenced the moisture, aeration, and strength characteristics of the
soils, and thereby reduced growth and efficiency of the root system.
Greater tap root and overall root penetration occurred on the unprocessed
than on the milled site. However, the amount of top growth did not
always correspond to the size and vigor of the respective root system.
Because of compaction, the soils had both low total water
capacity and low available water capacity. The compaction also
caused the formation of a crust which intensified dry soil conditions
by causing much rainfall to run off. Large amounts of rainfall were
sufficient to completely saturate the soil pores, but the low hydraulic
conductivity and high moisture retention then caused the pores to
drain very slowly, greatly intensifying soil aeration problems.
Soil aeration on the site is very poor. The production of
carbon dioxide and methane by the refuse, in conjunction with the
low amounts of gas-filled pore space, provides a great obstacle for
growing trees. Thus, it can be seen that the high mortality in the
fall and winter of 1971-72 was probably due in part to insufficient
oxygen present in the rooting zone.
Measurements indicated that the refuse had no detectable effect
on the soil temperature and that the fertility status of the landfill
soils is generally adequate for tree growth. It appears that the factors
limiting tree growth are more likely physical than chemical.
Because root systems were limited in extent and function by
deficient moisture, deficient oxygen5 or high soil strength, fertilizers
were apparently not utilized by the trees in sufficient quantities to
cause measurable growth changes.
Recommendations concerning site preparation, tree planting, and
cultrual practices to maintain trees on landfill sites, will depend upon
the proposed use of the landfill, the composition and preparation of the
refuse, the kinds of soil materials available, and the characteristics of
the site. Choice of a species depends upon use since trees grown for
aesthetic reasons should be chosen primarily on the basis of survival
and appearance while overall growth is more important for economic pur-
poses. The refuse composition and preparation will also influence
these choices since the type and amount of gas production is determined
by the refuse and may contribute significantly to deterioration and
death of trees.
A medium texture, we'll-structured soil material should be applied
to the refuse using a method which limits compaction as much as possible
around the base of the planted tree. The depth of soil material should
be as great as is economically feasible, providing adequate soil volume
for root expansion and a buffer between root system, and gases produced
by the refuse. Species to be planted should have the ability to develop
lateral root systems with diffuse branching; white ash and crab developed
such roots in this study. Relatively small seedlings should be planted
in planting holes which have mulch material cinci fertilizer packets added.
104
-------
Small seedlings can more easily adapt their root systems to the
environment in which they are planted. In cases where the planting
of larger trees is more desirable, planting holes should be back-
filled with topsoil and a mulch material to provide a good initial
root environment.
Other Vegetation:
Unless an uncovered cell of milled refuse is continually worked,
volunteer vegetation will develop within one or two years after placement.
During the summer of 1968, a diverse plant community, ranging from
weeds to garden vegetables to trees, became established spontaneously
on all the milled uncovered cells at the 01 in Avenue site. This growth
may have been due in part to seeds in the refuse itself. Heavy plant
growth has continued on the milled cells in subsequent years. In fact,
the vegetation of the milled refuse cell is so dense that it is difficult
for an observer standing on an old milled refuse cell to see that he is
indeed on refuse and not on soil (Figure 52).
Also in 1968, a slimy growth was noted on many of the milled uncovered
cells. It persisted throughout the summer and reappeared the next year.
It was identified as a slime mold, Fuligo septica, which is commonly found
in heavily wooded areas. It grows on material of high cellulose content.
This slime mold is not a threat to public health.
Fires
In August 1969, the Madison Fire Department evaluated fire hazards
on uncovered milled refuse. A freshly constructed cell and one that was
over a year old were used for the tests at the 01 in Avenue site. The
older cell had a cover of vegetation which was bulldozed off prior to
the tests. Moisture levels in the cells were lower than average as a
result of prolonged dry weather.
Attempts were made to ignite the cells by several methods which
simulated potential fire sources in actual landfill situations. Surface
fires were started by igniting oil which had been poured on the cells
and by igniting dry hay placed over the refuse. In all cases the
refuse smoldered but did not support flames once the oil or hay had
burned completely. Even though fans were used to create a 8-mph
wind during the hay tests on the aged refuse cell, combustion spread
only 25 feet after one hour. With fresh refuse, surface propagation
did take place, although no flames were evident. The smoldering re-
mained on the surface in all cases and was easily extinguished by water
spray or soil cover (Figure 53).
A fire starting from flying embers was simulated by placing hot
charcoal briquettes on the surface of the two cells. The charcoal had
virtually no effect on the aged cell. On the freshly milled cell,
however, combustion began slowly and spread, eventually encompassing the
entire cell surface. In this case the combustion was also limited to the
cell surface where it could easily be controlled.
105
-------
1 "* Hi "•«•'• •''--sdy%
rfe* "' Rr ~ *T; -&; £• -J » -r r.'^SfeiW "• **<'
"Jttr "!(*" '* *w ''' "
,-**r^A ^ -v|^* **' " '^ '» - . > ^
f»? " '" ' f •' J" • ^
Figure 52. Heavy vegetation growing on a test cell of milled refuse.
106
-------
01
o
3
CO
~, X
i— >>
rtS i—
I- •<-
O> to
JD (O
•r- QJ
0) to
-o to
Ol
J- -a
•r- C
ro
tn
cu
S-
cr>
107
-------
To simulate spontaneous internal combustion, a 1,200-watt electric
heating element was buried 3 feet deep in each cell. The element pro-
duced a temperature of 1,500 degrees F for 20 hours. In both cases,
refuse within an inch or two of the element was charred, but no com-
bustion occurred.
In summary, flame!ess combustion was supported by aged milled
refuse, but the combustion did not spread. A slowly spreading fire
was produced on the surface of the freshly milled cell. In both
cases the combustion could be arrested with water or soil.
The results of the fire tests were supported by an experience during
a dry spell in the spring of 1970, when a fire, apparently begun by
a lighted cigarette, began on a milled refuse cell. The fire burned on
the surface but did not penetrate to the interior of the cell. It was
extinguished by surface compaction with a front-end loader.
It is believed that the combination of a lack of voids and the
ready venting of flammable methane to the atmosphere is primarily
responsible for the lack of fire potential in piles of uncovered milled
refuse.
Odor and Esthetics
The 01 in Avenue landfill is bounded by a playfield on one side,
residential areas on two sides, and the Dane County Coliseum on the
other The Coliseum is a 10,000-seat facility. Thus, there was a
large "audience" available to make known their complaints if any odor
problems developed. Fortunately, no such problems have occurred.
The lack of unpleasant smells is one of the most notable features
mentioned by visitors to the milled refuse landfill areas. Project
personnel theorize that ready access to air and the accompanying drying
of the surface of the milled refuse cells produce an aerobic buffer zone
which treats or modifies odors produced deeper in the cells. In
support of this theory, it is noted that by digging 3 to 6 inches into
a cell, one begins to detect odor typical of decaying refuse. Upon
digging a foot or more, a most disagreeable odor is produced.
Some minor odor problems have developed during unusually wet
periods when, due to improper drainage of depressions between the
test cells, ponds of water formed. These problems have been readily
solved by filling the low areas or by providing drainage channels.
As noted earlier, milled refuse is relatively homogeneous and
looks like oversized confetti. Viewed from a distance, milled refuse
is nondescript and unobnoxious since it contains no large recognizable
items. Of the thousands of lay people who have viewed the 011n Avenue
landfill, no one has objected to the sight of uncovered milled refuse.
An independent evaluation of the public acceptability of the 01 in
Avenue reduction plant and landfill was published in Compost Science
in the January-February 1973 issue.
108
-------
Use of Cover
Cover soil 1s generally prescribed for a sanitary landfill to h1d«
the refuse, to reduce odors, to control blowing paper, to lessen the
danger of fire, to discourage vectors, and to limit leachate and gas
production. As we have seen in preceding sections of this report, most
of the problems solved by covering unprocessed refuse are similarly
reduced or eliminated by landfill1ng milled refuse without cover. In
other words, the Initial European claims for milled refuse have been
substantially borne out during the Madison demonstration project.
Except for possible considerations of groundwater contamination
due to rapid initial pollution loads 1n leachate from milled cells,
it appears that no daily cover 1s necessary. And, in fact, the question
of groundwater contamination is more dependent on local hydrogeological
considerations at the landfill site than on differences between milled
and unprocessed refuse. Thus, 1t 1s possible that in a multilayer milled
refuse landfill, the exposed layer may remain uncovered until the next
layer is placed on top of 1t. This sequence could be followed until
the landfill reaches final grade. (Some Intermediate cover may be re-
quired 1f final grade is not reached in a reasonable period, such as 6
to 12 months, or if local conditions dictate such procedure.) Once
final grade 1s achieved, the milled refuse should be covered to pre-
pare and reclaim the landfill site for other uses.
During construction of the 01 in Avenue test cells, 1t was the
practice to cover the top and sides of the unprocessed refuse cells but
not the daily working face. This amounted to what 1s commonly called
intermediate cover. The corresponding milled refuse cells were normally
not covered; however, special tests were conducted to estimate cover
soil requirements after a milled refuse landfill has been brought to
final grade. Based on these tests, 1t 1s felt that a practical depth of
dirt to cover milled refuse completely and smoothly is 6 Inches. In
comparison, a practical depth of cover dirt on unprocessed refuse was
found to be 14 inches on the top and 18 inches on the side of a cell
using the same equipment as with the milled cells. This amount of
cover provides a uniformly smooth and refuse-free surface of the same
quality as did the 6 inches of cover on the milled refuse. Although
some landfill operators will disagree with these figures, the ratio of
the cover required for equal quality of the finished surface for milled
and unprocessed refuse 1s felt to be valid.
This difference in cover requirements for the two cell types is
due to the more even surface that can be obtained with milled refuse.
Spreading, compacting, and filling unprocessed refuse 1s more difficult
than for milled refuse due to the extremely variable compactabll1ty of
the hetrogeneous unprocessed refuse which results in problems in obtain-
ing a level surface. The differences 1n compactabllity result in the
bulldozer leaving an uneven surface for unprocessed refuse which is
more difficult to cover completely. Milled refuse, on the other hand,
is easy to spread evenly without local depressions or rises because of
its smaller and more homogeneous particles. Also, the smaller particles
of milled refuse are not as readily pulled up by billdozer tracks during
compaction or pulled up through the soil during covering operations.
109
-------
To give an Indication of the monetary savings in cover soil between
milled and unprocessed refuse, two Madison landfills were compared.
The first was the 01 in Avenue site which was completely converted to a
milled refuse landfill in mid-1971 and thus did not use daily cover.
The other site was the Truax landfill for unprocessed refuse. The
Truax site operates under strict sanitary landfill procedures and
therefore uses considerable amounts of cover material. For this com-
parison it was assumed that the cover material used at Truax is obtained
at no cost for the material, although this is not always the case. Costs
for excavating and hauling the cover are included, however. The truax
operation handled about twice the volume of material as the Olin Avenue
site during the period of record, January through June 1972 (Table 17).
The table reveals that Madison expended three times the amount of
money, on a per-ton baiis, to operate an unprocessed refuse landfill as
it spends to operate a milled refuse landfill. This substantially higher
cost of a conventional landfill operation as experienced in Madison is
partly due to the handling of cover materials.
THE ECONOMICS OF MILLING
Landfill ing
In the preceding section, it was stated that the operating cost of
landfilling milled refuse amounted to $0.988 per ton for the period of
January through June 1972. During this period, Madison spent $23,043
while landfilling 23,317 tons of milled refuse at the Olin Avenue site.
This does not Include charges fdr land, site preparation or final covering.
By far the greatest cost of the 01 in Avenue landfill operation was
labor. The site is manned by one full-time compactor operator who works
a 7:30 a.m. to 4:00 p.m. shift. The operator averages 6 hours on the
fill and 2 hours on maintenance of landfill equipment.
During the 6 month evaluation period, no difficulties were encountered
handling the average daily load of 180 tons. It is believed, 1n fact,
that an average of 500 tons per day could be handled routinely with no
increase in men or machinery at the landfill.
Another labor expenditure was for cleanup of the area. Cleanup
consists of picking up paper, cutting grass, etc. This chore averaged
184 man-hours per month, with another 2 hours per day for supervision.
An auxiliary operator spent 32 hours on the site during the entire
6 months on read repair.
Permanent equipment at the Olin Avenue site consisted of a Steel
Wheel Compactor, which was operated between 5 and 7 hours per day. The
city garage sets an hourly rate of $6.25 per hour for use of the equip-
ment including amortization.
Stone and oil are used on access roads to the site. The stone
allows good wet weather operation. The road oil keeps dust down in
the summer dry periods.
Tabi* 18 presents the actual costs of operating the Olin Avenue
site during the first six months of 1972.
110
-------
Table 17
Cost Incurred in Landfill ing Milled and Unprocessed Refuse
(January 1 - June 30, 1972)
Cost Item
01 in $/ton**
Milled Refuse
Truax $/ton***
Unprocessed Refuse
WAGES*
Compaction
Supervision
Caretakers
Paper pickup
Loading (cover)
Hauling (cover)
Road repair
Scale operator
SUBTOTAL
EQUIPMENT
Compaction
Loading (cover)
Hauling (cover)
Paper pickup
Road repair
Misc. maintenance
Amortization
SUBTOTAL
MATERIALS - AREA IMPROVEMENT
Stone
Road oil
SUBTOTAL
TOTAL
0.310
0.090
0.270
none
none
none
0.010
none
0.680
0.206
none
none
0.020
0.010
none
0.035
0.271
0.019
0.018
0.037
0.988
0.449
0.229
0.374
0.222
0.182
0.335
0.010
0.121
1.922
0.449
0.209
0.211
0.015
0.008
0.076
0.105
1.073
none
none
0.000
2.995
*Includes all fringe benefits
**23,317 tons
***48,660 tons landfill
111
-------
TABLE 18
Landfill Costs Using Milled Uncovered Refuse
(January 1 - June 30, 1972)
Cost
WAGES*
Compaction $ 7,112
Supervision 2,413
Cleanup 6,518
Auxiliary Operator 221
SUBTOTAL $15,994
EQUIPMENT
Operation (Landfill Compactor Only) $ 3,859
Auxiliary (Road Repair) 310
Amortization (Landfill Compactor Only) 2,025
SUBTOTAL $ 6,194
MATERIALS - AREA IMPROVEMENT
Stone $ 435
Road Oil 429
SUBTOTAL $ 855
TOTAL $23,043
*Includes all fringe benefits
112
-------
'i 11 lug Costs
At Madison, there has been a considerable savings in landfill costs
by using milled refuse without daily cover; however, the additional costs
of the milling process itself must obviously be added to the landfilling
cost to indicate the total cost of refuse disposal by the milling method.
The following sections will investigate these costs and conclude with
cost-per-ton projections which are reasonable for operations like the
one at Madison.
Gondard System:
Cost data for the Gondard system are for the third year of the
demonstration project, from June 1968 through May 1969, by which time
the Gondard operations were refined. Although it is proper to report
the costs incurred in the Madison plant, one must be cautioned about
applying these costs to other installations because this project
began as a pilot plant demonstration whose operation is probably more
sxpensive than that of future plants. More importantly, one must recognize
cho regional variations in labor, power costs, heating costs, and
depreciation methods. Inflation during the years since this study was
undertaken must also be considered.
Furthermore, the unit costs in Table 19 is higher than would be the
case for a larger and differently designed plant because:
1) Refuse was not conveyed to the mill as fast as the mill could
grind;
2) A similar plant without extensive foundations and extra
conveyors would be less costly;
3) Adaptation and improvements can still be made in haul-away
operation.
As in other sections of this report, land costs are not included,
because in most instances they are a negligible part of the total cost
and vary too greatly from area to area to be meaningful. As an example,
the Olin Avenue site was purchased at $1,000 per acre; similar land in
the area is now selling for $5,000 to $10,000 per acre.
The costs per ton are calculated by dividing the annual cost by the
annual tonnage. The annual tonnage figures are projected by using the
overall Gondard production rate, the average number of working hours
per day, and the number of working hours per week.
Table 19 lists the cost per ton for each of the major cost categories
and for three grate sizes.
113
-------
TABLE 19
UNADJUSTED COST DATA FOR GONDARD MILL
(JUNE 1968 THROUGH MAY 1969)
Cost Item
Labor
Amortization
Power
Lighting
Water
Gas-heat
Hammer Wear
Mill Maintenance
Small Equipment
General Supplies
Front End Loader
Operation
Transportation
to Landfill*
Other
TOTAL
Annual Cost
$39,800
$32,200
variable
$ 2,300
$ 200
$ 1,200
$1,600-1,710
$850-950
$ 800
$ 1,100
$ 500
$ 3,250
$ 1,700
3-1/2 Inch
10,750
$3.70
$2.99
.34
.21
.02
.11
.16
.08
.07
.10
.05
.30
.16
$8.29
ton
Grate Size
5 Inch
Annual Tonnage
11,500
$3.46
$2.80
.30
.20
.02
.10
.15
.08
.07
.10
.04
.28
.15
$7.75
ton
6-1/4 Inch
12,050
$3.30
$2.67
.30
.19
.02
.10
.14
.00
.07
.09
.04
.27
.14
$7.41
ton
*Based on round trip of less than 1/2 mile
114
-------
The average hourly wage for the three plant workers together during
the evaluation period was $19.15, including all fringe benefits and over-
time. Yearly labor cost is obtained by multiplying $19.15 by the
number of working hours in a year (2080). This yields $39,830 per year for
labor costs. To get labor cost per ton, this figure was divided by
projected annual tonnage of 11,500 tons.
The annual cost of amortization was calculated by assuming machinery
life and interest rates depending on source of funds. Table 20 lists data
used to arrive at the annual amortization figure of $32,100.
The experimental periods did not exactly coincide with the utility
companies' billing periods. It was therefore necessary to project
power consumption to a monthly basis in order to determine equivalent
monthly costs. The costs of power ranging from $0.34 to $0.30 per ton
are the weighted averages during the times that the three grate sizes
were used.
Computation of other costs was straightforward and needs no further
explanation.
Tollemache System:
Two experimental runs using only the Tollemache mill were undertaken
in the summer of 1970 and winter of 1971. During both of these runs,
extensive cost data were collected on labor, power, repairs, replacements,
etc. Thus, a comparison is possible between summer and winter operations
of the same plant and equipment. To make the comparison equitable, changes
in wages and other increases in cost between the two runs must be
considered. Therefore, actual and adjusted costs will be presented for
Lhe data obtained during 1970, with adjusted cost being computed using
the wages and prices in effect during the 1971 test.
Cost of the milling operation (excluding landfilling) is best
presented in two general categories: that of milling, including
conveyance of the unprocessed and milled material; and that of
transportation to the final disposal site, including the stationary
packer and hauling equipment.
Table 21 contains an extensive breakdown of the costs incurred
during the two test periods on a per-ton basis. Affecting these figures
are such uncontrollable factors as the average moisture content of the
refuse being processed. Therefore the costs stated here can be viewed
only as an indicator of what was experienced at one installation and
as such they cannot be expected to be generally applicable to other
locations.
An analysis of Table 21 indicates that on an adjusted basis the
cost per ton for period 1, summer 1970, is about $0.43 less than period
2, winter 1971. There are two prime factors contributing to this.
First is the fact that on the average fewer tons were milled per day
during period 2; thus, relatively stable or fixed costs such as amortiza-
tion increased on a per-ton basis. The decrease in average milled tons
per day is due to seasonal variations in refuse quantities and moisture
content. Also during period 2 gas and lighting costs increased due to
changed weather conditions.
115
-------
TABLE 20
DATA USED FOR COMPUTING AMORTIZATION OF ORIGINAL GONDARD INSTALLATION
Cost Item
Building
Grinder and
Conveyors
Scale
Front End
Loader
Packer
Trucks (2)
Original
Cost
$133,100
126,700
6,900
15,400
38,000
Total
Estimated
Life-Years
20
15
20
8
10
Annual Cost - Amorti
Interest
Rate
5.8
5.8
7.0
7.0
7.0
zation
Salvage
Value
$4,000
4,000
1,000
3,000
3,000
Annual
Cost
$11,300
12,700
600
2,300
5,200
$32,100
116
-------
TABLE 21
TOLLEMACHE MILLING COSTS
Labor***
Amortization
Hammers & Shafts
Power
Welding Rod
Plant Supplies
Front End Loader Maintenance
Gas - Heat
Lighting
Water & Sewer
Contracted Repairs
Replacement Parts
TOTAL
Test
Period
$/Ton
$2.395
1.134
0.137
0.245
0.033
0.029
0.055
0.000
0.052
0.001
0.011
0.038
$4.130
#1*
Adjusted
$/Ton
$2.758
1.134
0.137
0.284
0.033
0.029
0.068
0.000
0.059
0.002
0.013
0.045
$4.562
Test
Period #2*
$/Ton
$2.577
1.327
0.206
0.351
0.031
0.042
0.079
0.154
0.105
0.006
0.040
0.074
$4.992
* 14 wks. - July 6 - October 9, 1970, 5318 tons milled, average - 77
tons/day and 5.3 hrs. machine time/day
** B wks. - February 4 - March 31, 1971, 2624 tons milled, average -
66 tons/day and 5.1 hrs. machine time/day
*** Includes all fringe benefits
117
-------
The average overall adjusted cost per ton of approximately $4.80
can be misleading. It must be remembered that this figure has been
derived from experimental runs. At the time of the tests the plant
was only operating at three-fourths of its rated capacity. At full
capacity the plant could average 90 to 100 tons/day as compared to the
65 to 75 experienced during the tests. This would mean that fixed
costs, labor and amortization, would be reduced by nearly 27 percent
over the tabulated cost per ton, and the overall cost would be reduced
by 23 percent to an average of $3.70/ton.
Table 22 contains the detailed breakdown of costs for the sta-
tionary packer and transportation to the landfill on a per-ton basis for
test periods 1 and 2. The actual cost as well as the adjusted cost per
ton are presented for period 1 as in Table 21. Again, it is felt
that transportation costs experienced at Madison during this evaluation
are not indicative of transportation costs that would be expected at
other localities under different conditions. Thus, these costs are
presented separately to stress tht they apply to Madison's operation
only.
The computations of costs during the Tollemache evaluation were
made similarly to those in the Gondard economics section. However,
several differences should be noted. First, the average total hourly
wage, including fringe benefits and overtime, for the three plant
personnel had risen from $19.15 to $20.39. Also, amortization figures
were somewhat different, as shown in Tables 23 and 24.
Two-Mill, Two-Shift Operation:
Extensive cost data on all plant functions were collected during
the first 6 months of 1972. As with the Tollemache system, these data
will be presented in two parts - costs of milling and costs of compaction
and final transportation.
Again, it is important to stress that the figures presented here are
strictly applicable only to Madison's operation. This qualification is
especially important in this section, in which two vastly different mills
are being discussed.
The total cost of the 6-month run will be reported first. Table 25
gives a detailed breakdown of expenditures and costs per ton for the period
of record. Total tons milled during that period were 23,317.
The total 6-month expenditure for mill operation was $91,000, or
$3.90 per ton. Ilotice that labor and depreciation account for $2.75
per ton, or 71 percent of that total. Thus it is imperative for ef-
ficient operation that the maximum tonnage of refuse be milled during
the 16-hour working day. If plant production could be increased from
the current rate of 46,000 tons per year to a feasible 60,000 tons per
year, the per-ton cost of milling could be reduced 15 percent to approxi-
mately $3.29 per ton.
118
-------
TABLE 22
STATIONARY PACKER AND HAUL COSTS
DURING TOLLEMACHE EVALUATION
Test
Period
$/Ton
Amortization $0.448
Labor (Driver)*** 0.120
Power 0.016
Tractor & Trailer Maintenance 0.018
Packer Maintenance 0.010
TOTAL $0.612
#1*
Adjusted
$/Ton
$0.448
0.137
0.019
0.027
0.012
$0.643
Test
Period #2**
$/Ton
$0.524
0.147
0.023
0.017
OiPJL2.
$0.723
* 14 wks. in length - July 6 - October 9, 1970, 5318 tons milled,
average - 77 tons/day and 5.3 hrs. machine
time/day
** 8 wks. in length - February 4 - March 31, 1971, 2624 tons milled,
average - 66 tons/day and 5.1 hrs. machine
time/day
*** Includes all fringe benefits
-------
87,600
5,916
15,400
15
20
12
5.9%
6.5%
6.5%
4,000
1,000
3,000
8,640
660
1,700
TABLE 23
AMORTIZATION DATA FOR TOLLEMACHE MILLING SYSTEM
Original Effective Interest Salvage Annual
Item Cost Life (Yrs.) Rate Value Cost
Building and
Foundation $133,188 20 5.9% $4,000 $11,390
Tollemache Mill
And Conveyors
Scale
Front-End Loader
TOTAL $22,390*
* The total annual amortization cost of $22,390 can be proportioned to the
14 week and 8 week evaluation periods on a straight line basis. Amortiza-
tion for the 14 week evaluation is 14/52 ($22,390) = $6,034 and for the 8
week period 8/52 ($22,390) = $3,448
TABLE 24
AMORTIZATION DATA FOR STATIONARY COMPACTOR AND
FINAL TRANSPORTATION SYSTEM
Item
Stationary Compactor
and Hopper
Two Trailers
One Tractor
Building Addition
TOTAL $8,850
Original
Cost
$ 19,150
33,000
13,625
16,801
Effective
Life (Yrs.)
15
12
15
20
Interest
Rate
6.5%
6.5%
6.5%
6.5%
Salvage
Value
$1 ,000
1,500
1,500
1,000
Annual
Cost
$2,000
3,960
1,390
1,500
120
-------
TABLE 25
MILLING COSTS FOR TWO-MILL,
TWO-SHIFT OPERATION (JANUARY THROUGH JUNE 1972)
Total Cost Cost/Ton*
Labor $44,684 $1.912
Amortization 19,570 0.838
Replacement Parts 8,097 0.346
Power 4,382 0.188
Hammers and Shafts 3,786 0.162
Heat - Gas 2,391 0.102
Supplies 2,196 0.094
Lighting 2,023 0.087
Front-End Loader Maintenance 1,653 0.071
Welding Rod 1,128 0.048
Contracted Repairs 1,047 0.045
Water and Sewer 44 0.002
TOTALS $91,001 $3.895
* Based on 23,317 tons milled
121
-------
The final figure of $3.90 per ton as presented in Table 25
represents a sizable reduction from the earlier stated costs for
experimental runs of both the Gondard and Tollemache Systems separately.
The figure is 48 percent lower than that actually experienced during
the Gondard evaluations of 1968 and 1969. It is also 19 percent lower
than the average figure obtained during the Tollemache evaluations of
1970 and 1971. The reduction is the result of better supervision and
the 125 percent average daily increase in tonnages milled over that
of the single-shift operations.
Total milling labor costs as charged to the plant during the 6
month of record are shown in Table 26.
The average total hourly wage for the three regular plant personnel
needed for each shift is now $20.98. The plant supervisor's hourly wage
is $6.25. Labor rates are based on job classification and length of
service with the city.
A breakdown of labor costs into three main categories is given in
Table 27. No differentiation is made between times devoted to the
Gondard or Tollemache system individually.
The data indicate that nearly 73 percent of the total labor cost,
not including supervision, is a result of mill operations, while only
15 percent and 12 percent is the result of repair and hammer maintenance,
respectively.
Based on data from the Gondard and Tollemache systems, separately,
the total amortization for the 6-month period was $19,570. On a per-ton
basis the figure is $0.838.
Power costs for the two mills combined are presented in Table 28.
Table 29 contains power cost data for the mill accessories.
In both tables the demand cost is constant each month, and in
the case of the mills themselves, the demand charge is more than the
energy used. This is an important factor in the overall power cost,
as an increase in tonnage milled will decrease the total cost per
ton. For example, during the Tollemache runs, power averaged $0.24
per ton at an average rate of 70 tons of refuse milled per day.
Power costs for the Gondard runs averaged about $0.28 per ton back
in 1968, at much lower rates, for an average of 46 tons of refuse milled
per day. During 1972 the combined mill operation consumed power at
the cost of $0.168 per ton, which represents a 53 percent reduction
over the single-mill operation. The reason for the decrease is that
187 tons of refuse were processed per day in 1972.
Lighting and other small services are supplied by 220-volt service.
Table 30 contains monthly 220-volt service costs and the amounts of
electricity used.
The plant is heated by radiant natural gas heaters. Table 31
contains a monthly breakdown of heating costs. The total expenditure
reflects 3 months of winter heating bills and 3 months of much lower
spring bills. Past experience has shown that heating costs have gone
almost to zero from June through September.
122
-------
TABLE 26
LABOR COSTS - TWO-MILL, TWO-SHIFT OPERATION
(JANUARY THROUGH JUNE 1972)
Plant Personnel
Supervision
TOTAL
* Includes all fringe benefits
** Based on 23,317 tons milled
Actual Man Hours
5456
1040
6500
Cost*
$38,180
6,504
$44,684
Cost/Ton**
$1.634
0.278
$1.912
TABLE 27
BREAKDOWN OF LABOR COSTS - TWO-MILL, TWO-SHIFT OPERATION
(JANUARY THROUGH JUNE 1972)
Han-Hours
Hill Operation
Repair Maintenance
Hammer Maintenance
SUBTOTAL
Supervision
TOTAL
* Includes all fringe benefits
** Based on 23,317 tons milled
Total
3969
850
641
5460
1040
6500
Per Week
152.8
32.7
24.7
210.0
40.0
250.0
Cost*
$27,754
5,944
4,482
$38,180
6,504
$44,684
Cost/Ton**
$1.188
0.254
0.192
$1 ,634
0.278
$1.912
123
-------
TABLE 28
POWER COSTS, MILLS, TWO-MILL, TWO-SHIFT OPERATION
(JANUARY THROUGH JUNE 1972)
January
February
March
April
May
June
OVERALL
* Based on 23
POWER COSTS,
January
February
March
April
May
June
OVERALL
Demand
Cost
$341
341
341
341
341
341
$2046
Energy
Cost
$257
311
332
329
330
321
$1880
Total
Cost
$598
652
673
670
671
662
$3926
Cost/Ton*
$0.225
0.195
0.196
0.158
0.131
0.146
$0.168
,317 tons milled
TABLE 29
MILL ACCESSORIES, TWO-MILL, TWO-SHIFT
(JANUARY THROUGH JUNE 1972)
Demand
Cost
$ 19
19
19
19
19
19
$114
Energy
Cost
$ 47
56
60
60
61
58
$342
Total
Cost
$ 66
75
79
79
80
77
$456
OPERATION
Cost/Ton*
$0.025
0.023
0.023
0.019
0.015
0.017
$0.020
* Based on 23,317 tons milled
124
-------
TABLE 30
LIGHTING COSTS, TWO-MILL, TWO-SHIFT OPERATION
(JANUARY THROUGH JUNE 1972)
January
February
March
April
May
June
OVERALL
Demand
(kw)
38.6
40.0
40.0
40.0
40.0
40.0
Energy
(KWH)
18,788
17,088
19,286
14,734
12,772
13,294
Demand
Cost
$ 58
61
61
61
61
61
$363
Energy
Cost
$ 319
293
326
258
228
236
$1660
Total
Cost Cost/Ton*
$ 377 $0.14
354 0.106
387 0.113
319 0.075
289 0.056
297 0.066
$2023 $0.087
* Based on 23,317 tons milled
TABLE 31
PLANT HEATING COSTS, TWO-MILL, TWO-SHIFT OPERATION
(JANUARY THROUGH JUNE 1972)
Usage
January
February
March
April
May
June
OVERALL
100 Cu. Ft. Gas
8,679
8,297
5,124
1,983
618
540
Cost
$ 823
788
468
194
63
55
$2391
Cost/Ton*
$0.309
0.262
0.136
0.046
0.012
0.012
$0.102
* Based on 23,317 tons milled
125
-------
Total water usage equaled 6510 cu. ft. The cost of this water
equaled $21.00. Sewer charges are 140 percent of the total water cost.
Thus the water and sewer bill for 6 months equalled $44.45, or $0.002
per ton.
Items such as hammers, hammer shafts, and welding rods constitute
supplies used in the hammer maintenance program. Table 32 contains
all pertinent data in respect to the numbers of each item used and the
resultant expenditure. Hammer maintenance supplies constitute the
fourth largest expense in plant operations.
As seen in Table 25, the cost of replacement parts was over $8,000
and is therefore the third most expensive item on the list of plant
expenses. Parts replaced during the period of record were mill grates
(Gondard) and wear plates (Tollemache) as well as conveyor belting - all
of which are very expensive items. A set of Tollemache liners, which lasts
approximately 6 months, costs nearly $1,300. Gondard grates, also lasting
6 months, cost nearly $800 per set. Other parts such as small motors,
conveyor slats, and bearings, make up the remainder of the expenditure in
this area.
Other expenses included miscellaneous supplies, contracted repairs,
and front-end loader maintenance. Supplies consisted of janitorial
requirements, office materials, grease and oils, etc. The total expendi-
tures for sunplies, $2,196, is almost $0.10 per ton. Contracted repairs
include all labor and material charges for repairs made by outside agen-
cies. The total cost, $1,047, is less than $0.05 per ton. Front-end
loader maintenance is dependent on the hours of vehicle use. The city
garage charges $4.27 per hour of use to cover vehicle maintenance such
as oil, minor repairs, grease, etc.
Expenses for compaction and hauling include labor, depreciation,
power, and equipment maintenance. Not included are minor expenses
due to heat, lighting, and water which are grouped under milling
costs. Table 33 gives a complete listing of all expenses attributed
to final handling of the milled material, excluding landfilling costs.
Labor expenses, as was the case with milling costs, constitute
the largest expenditure for compaction and hauling. A total of 780
hours, or 30 man hours per week, was spent in transporting milled
material to the landfill (round trip is less than 1/2 mile). Vehicle
maintenance is computed on a per-mile charge. Tractors are charged at
a rate of $0.20 per mile and transfer trailers at the rate of $0.25
per mile. The charges cover all fuel, oils, grease, and minor repairs.
Table 33 indicates that the total power cost is almost insigni-
ficant at $0.014 per ton. The stationary compactor maintenance at
$0.032 per ton consists of labor and parts for all repairs to the com-
pactor. As the figures show, the compactor is not prone to breakdowns.
126
-------
Used
1000
43
600
Unit
Cost
$ 3.27
12.00
1.88
Total
Cost
$3,270
516
1,128
Cost/Ton*
$0.140
0.022
0.048
TABLE 32
SUPPLY COSTS, HAMMER MAINTENANCE, TWO-MILL, TWO-SHIFT OPERATION
(JANUARY THROUGH JUNE 1972)
Hammers
Shafts
Welding Rod (Ibs.)
OVERALL $4,914 $0.210
*Based on 23,317 tons milled
TABLE 33
STATIONARY COMPACTION AND HAUL COSTS, TWO-MILL, TWO-SHIFT OPERATION
(JANUARY THROUGH JUNE 1972)
Cost Cost/Ton*
Labor $ 5,216 $0.223
Amortization 4,380 0.188
Compactor Maintenance 753 0.032
Haul-Vehicle Maintenance 597 0.025
Power 334 0.014
OVERALL $11,280 $0.482
*Based on 23,317 tons milled
127
-------
Cost Projections^
Based on the extensive cost data on operations at the 'Edison
Refuse Reduction plant, several projections have been meule on tht>
costs of various milling systems employing the Toller.tache mill.
The estimates take into account one through four mills operated
either one or two milling shifts per day and an additional shift
for maintenance.
It is important to realize that, while the projections are thought
to be accurate, they apply strictly only to Madison. Wage rates,
power and utility rates, depreciation, etc. are all based on mid-1972
costs as experienced in Madison, Wisconsin. To arrive at projected
costs for similar operations at other localities, it will be necessary
to make an economic study using appropriate base rates.
It was assumed in these projections that each Tollemache mill will
operate an average of 7 hours per shift at a rate of 14 tons per hour.
It was also assumed that the plant will operate 245 days (or 49 weeks)
per year, with 3 weeks for repairs. Each plant will include a minimum
of one mill, one feed conveyor, two transfer trailers, and one tractor.
Two mill plants will have two mills and feed conveyors, but will
otherwise be similar to a one mill installation. Plants with three or
four mills will have two discharge conveyors, two stationary compactors,
four or five trailers, and two tractors. In addition to the one or two
milling shifts is an additional maintenance shift. The maintenance
shift duties involve mill maintenance, plant clean up and maintenance,
and machine repair work.
Under these conditions, each mill will produce approximately 100
tons per day, or 24,500 tons per year. Daily and annual tonnages for
combinations of mills and shifts are tabulated in Table 34.
A cost analysis of the various plant sizes on a one and two shift
milling operation resulted in projected milling, transfer, and land-
filling costs per ton as shown in Table 35. A detailed cost analysis
is provided in Appendix A of this report.
Thus, if a municipality generates 196,000 tons of mi 11 able
refuse per year, this refuse could be milled and landfilled for a cost
of $2.75 per ton using four Tollemache mills for two shifts per day.
This corresponds to Madison's present costs of $4.88 per ton for milling
and landfilling refuse and $3.00 per ton for landfilling unprocessed
refuse.
It is to be stressed that milling is but an alternative method
which can be used in conjunction with landfill. It is not meant as a
replacement for landfill. Instead, its characteristics may enable a
higher set of operational standards to be followed at similar or slightly
higher costs than standard sanitary landfilling.
128
-------
TABLE 34
Production Estimates
(For one and two shifts, and one to four mills)
(Number of Mills
_J 2 3 4
One Shift
Daily tons 100 200 300 400
Annual tons 24,500 49,000 73,500 98,000
Two Shifts
Daily tons 200 400 600 800
Annual tons 49,000 98,000 147,000 196,000
129
-------
TABLE; 35
Annual Average Costs per Ton for [-1111 ing, Hauling, and Landfill ing Refuse
Number of Hills
1234
One Shift
Annual tonnage
'Tilling, stationary
compactor, and haul
costs/ton*
'"illfilling costs/ton
TOTAL costs/ton
Two Shifts
Annual tonnage
ili 11 ing, stationary
compactor, and haul
24,500 49,000
5.27
1.43
C.34
3.74
0.75
4.59
49,000 98,000
73,500
3.48
0.73
4.21
93,000
3.33
0.57
3.90
147,000 19C,090
costs/ton*
Mill fill ing costs/ton
TOTAL costs/ton
3.75
0.75
4.50
2.70
0.50
3.20
2.52
0.57
3.09
2.30
0.45
2.75
*Cost includes amortization, labor, operation, and milled refuse haul to
landfill less than ^ mile av;ay. Land cost excluded.
130
-------
TRENDS AND DEVELOPMENTS
Before the Madison milling project began in 1967, the only milling
of solid waste in the United States was for the production of compost.
Since Madison's project was initiated, most of these composting
facilities have been closed down for one reason or another, but a number
of other milling facilities have been constructed and many more are in
the planning or construction stages. The facilities that have been
constructed or that are being planned are for the purposes of:
1. Hilling refuse for baling in a continuous baler - San Diego,
California.
2. Hilling refuse for energy recovery by burning it in a conven-
tional coal or gas fired power plant - St. Louis, flissouri.
3. Milling refuse for energy recovery in new types of municipal
incinerators in which most of the burning takes place in air
suspension - Hamilton, Ontario, Canada.
4. Milling refuse for landfill disposal - Pompano Beach, Florida;
Mil ford, Connecticut; Vancouver, Washington; etc.
b. Milling refuse for resource recovery - at the oresent time,
March 1973, the City of Madison is one of the few facilities
known to be magnetically separating the ferrous metal from
milled refuse. A number of future plants will magnetically
separate ferrous metal and will also attempt more advanced
schemes of resource recovery.
The original application for the fladison demonstration project was
entitled, "Solid '.laste Reduction/Salvage Plant". It was envisioned
that narketable material could be picked from the solid waste feed bolt
by hand and marketed through local salvage dealers. While time has
shown that this idea was rather naive in terms of recycling, it does
illustrate that the concept of material recovery from solid waste v/as
one of the motivating factors for the Madison project.
Since then, the City of Madison has entered into a separation-at-
the-source newsprint recovery project; a cooperative project with the
Continental Can Company for magnetic separation and marketing of ferrous
rnetal from the milled refuse; and a log recycling project in cooperation
with Urban Hood Fiber, Inc. A cooperative agreement with the Forest
Products Laboratory, U.S. Department of Agriculture, for recycling of
v/ood fiber has resulted in work on wood fiber separation. Following is
a more detailed description of these projects.
131
-------
In 1967, the 'lational Committee for Paper Stock Conservation
approached the City of Madison with a proposal that the Committee and the
City of Madison work together on a project to collect newsprint separated
at the source. Since early contacts with local secondary material dealers
had indicated that any paper that had been in a packer truck would not
meet existing paper specifications, the City of Madison expressed interest
in the recycling project proposed by the Committee, In the fall of 1968,
the City of Madison entered into a pilot project on the east side of the
community which in 1970 was extended to the west side of Madison. The
newspapers are bundled separately by cooperating citizens, placed at
curbside along with the remainder of the solid wastes, and placed by the
collection crews on specially built racks under the packer bodies. In
1972 approximately 2,800 tons of newsprint vie re collected; this amounted
to about 1.5 percent of the total amount of solid waste collected and
brought to City of Madison disposal sites.
A study of the realities of recycling by the City of Madison led
to the conclusion that probably only newsprint meets the criteria for a
successful separation-at-the-source program. Newsprint is easily
identified by the home owner, available in large quantities, and fairly
easily marketable. When the newsprint project was beginning, a new
de-inking mill was going on line at Alsip, Illinois and this created a
new demand in the Midwest for newsprint.
A study of further recovery of wood fiber has led to the conclusion
that mechanical methods are necessary for large-scale recovery. Dialogue
with the Forest Products Laboratory in Madison led to a cooperative
agreement in 1970 between that institution and the City of Madison to
cooperate on fiber recovery. Madison's main role in this project was to
provide working space at the Refuse Reduction Plant and to supply
milled refuse for the Forest Products Laboratory projects.
The pilot separation facility established by the Forest Products
Laboratory at the 01 in Avenue P^efuse Reduction Plant is a flexible
dry-separation system. The system is designed to use air currents to
separate light materials (paper and sheet plastics) from heavy materials
and to separate the paper into several types. Equipment includes two
fans, two cyclone units, an air classifier, a dry screen, and conveyor
and collector bins. All separation equipment in the pilot facility
is available commercially. Specific units were acquired solely on
the basis of availability and their application to the pilot scale.
Other commercial equipment may be equally suitable for the same
purposes.
The first fiber recovery experiments began in the fall of 1971.
Since then, the Forest Products Laboratory has used wood fiber to
make paper and building products out of the material in sufficient
quantity and size to run standard tests on the quality of materials
from urban v/aste. Lfforts are currently underway to obtain large enough
samples of the wood fiber to run production-scale tests of various
products.
132
-------
j:
In September 1971 the City of Madison entered into an agreement
with the Continental Can Company, Inc., which granted that company
5 years of salvage rights of the ferrous metals and alloys removed from
;-iilied refuse. Under terms of the agreement, the Continental Can
Company installed a magnetic separator, provided the trucks to haul
the material away, and developed the markets. They also paid the
City of "ladison 10 percent of any profits. Perfecting the mechanics of
magnetic separation has taken approximately a year and has required
some developmental work. A new magnetic separation unit has been
installed on the basis of the experience gathered with the first unit.
The new unit is obtaining approximately 95 percent of the ferrous metals,
3nd during a run in February 1973, 10 percent by weight was removed as
ferrous metals from approximately 20,000 Ibs. of solid waste.
After lengthy negotiations v/ith Urban Wood Fiber, Inc., the City
of Madison has obtained an outlet for market-sized logs from municipal
and private tree clearing operations in the City of Madison. This
operation was a direct spin-off of attempts to develop a milling system
for trees and logs generated in the City of Madison.
Another study undertaken through the City of Madison milling
.voject has been work by Professor Norman Bra ton of the University of
Hisconsin-Madison Mechanical Engineering Department on developing
techniques for shredding frozen tires. The tires are first frozen in
liquid nitrogen and then dropped into a hammermill. The frozen
rubber is quickly and easily separated from the remainder of the tire
carcass. Professor Braton proposes to develop equipment on a railroad
car which could be shipped from place to place to freeze and fragment
tires, thus producing marketable rubber.
There are over one hundred plants in the United Kingdom and on the
European continent which are milling refuse for landfill disposal without
daily cover. Some of these facilities have been in operation for 20
years. A result of the Madison project has been the construction and
operation of a number of facilities in the continental United States for
milling refuse for landfill disposal. In addition, there are also on the
drawing boards or under construction many more of such facilities.
Uhile only time will determine the ultimate success or failure of the
milling approach, it is felt that milling is definitely assuming a
significant role in the solid waste management field in the United
States.
133
-------
COIiCLUSIONS
Among the conclusions of the demonstration milling oroject in
Madison between 1967 and 1972 are the following:
1. As operated at Madison, the Gondard hammermill has a capacity
of 9 tons per hour with a 5-inch grate, and the Tollemacho hammermill
has a capacity of 14 tons per hour with a 34-hammer pattern. The grate
size and hammer pattern were chosen to grind refuse as coarsely as
possible without producing problems of blowing litter at the landfill
and without leaving food wastes accessible to vectors. (On a dry-weight
basis, between 30 and 90 percent of the particles produced by both mills
pass through a 2-inch screen.) Evaluations of the two mills separately
showed that the Gondard mill uses nearly as much electrical energy as the
Tollemache mill while producing only about 60 percent as much milled
product as the Tollemache.
2. Aside from some minor problems with the mills themselves, most
of the early operational problems were associated with conveying refuse
to the mills and carrying milled refuse to the landfill. The steeply
inclined feed conveyor and the stationary compactor with a 75-cu. yd.
transfer vehicle used with the Tollemache mill have greatly increased
the ability of the Madison plant to handle unprocessed and milled refuse
on a production basis.
3. Residential and light commercial refuse as collected at Madison
can be milled in either type of hammermill without extensive presorting,
with minimal hand-picking of unmillables, and with negligible downtime
due to mill stoppage.
4. Milled refuse has been left in a landfill without cover for
up to 6 years, and no complaints have been received about odors,
unsightliness, blowing litter, rodents, or insects. Public acceptance
of the milling plant and the landfill has been unusually good.
5. experience with milled refuse without daily cover indicates that
the quality of operation at this type of landfill is superior to
sanitary landfill operations at Madison with respect to travel over the
fill and at the face of the fill, dust, tracking of trucks on highways,
appearance during operating hours and maintaining a uniformly high
level of operation during cold and wet weather. Fully loaded trucks
weighing nearly 73,000 Ibs. can drive on milled refuse in inclement
weather. Also, tire problems have not been caused by travel on uncovered
milled refuse.
G. experience and specific testing have shown that there is less fire
hazard with milled than with unprocessed uncovered waste in a fill.
7. Rats are not able to survive on properly milled refuse
containing up to 20 percent wet garbage on a wet-weight basis. Cased
on this finding and on observations of the landfill site, there is very
little likelihood of rat infestation and survival in a properly operated
milled refuse landfill.
8. Under optimum weather and moisture conditions, flies probably
can breed in freshly milled refuse; however, once such refuse has aged
several months, this ability is evidently lost. Tests with the Gondard
mill showed that nearly all fly maggots passing through the mill during
134
-------
normal operation were killed. Fly counts and operating experience
at Madison indicate that there is no fly nuisance problem associated
with mil led refuse.
9. Compaction of cover soil, as v/ell as production of methane
and carbon dioxide by underlying refuse, created poor aeration
conditions for tree roots and thus led to a high mortality of trees
planted on milled and unprocessed refuse cells after 2. years. White
ash and crab were the most successful of the tree varieties planted
in that they developed effective lateral root systems in the densely
compacted cover soil.
10. Actual refuse density of milled refuse on a wet-weiqht basis
v;as found to be approximately 27 percent greater than the actual refuse
density of unprocessed refuse given equal compaction. Under the same
conditions, the effective refuse density of milled refuse was
calculated to be nearly 35 percent greater than that of unprocessed
refuse.
11. Leachate production occurs at a faster rate in milled uncovered
cells than in covered cells, milled or unprocessed. In the absence of
cover, milled refuse develops a relatively mature degradation pattern
and thus lowers the organic pollution load leaving the refuse in
leachate. Before a mature degradation condition develops in milled
refuse, large quantities of organics in particular are leached from
milled refuse.
12. The covered unprocessed refuse cells never produced organics
at as high a rate as did the milled cells during initial stages of
decomposition; however, the unprocessed cells continued to produce
organics at a fairly consistent rate throughout the duration of the
project. Thus, the milled refuse cells could be characterized as
producing more leachate contaminants during initial stages of decompo-
sition but less during later stages of decomposition than the
unprocessed refuse cells.
13. A water budget analysis shows that in Madison, Wisconsin
about 68 percent of incident precipitation on covered refuse in a
landfill evaporates, while the remaining 32 percent is divided almost
equally between runoff and infiltration (leachate). Virtually no
runoff and slightly more evaporation occurs with uncovered milled refuse.
14. In the first evaluation of the Gondard mill with a 5-inch
grate in mid-1968, a per-ton cost of $7.75 - including process and
hauling costs but excluding landfill ing costs - was experienced.
When this figure was adjusted to exclude factors related solely to
the experimental aspects of the operation, a comparable cost of $5.33
per ton emerged as a reasonable estimate for a production facility.
Juring an evaluation of the Tollemache mill in the summer and fall of
1970, a cost of $4.13 per ton for milling and hauling (but not
landfill ing) was calculated. A winter evaluation early in 1971
yielded a cost per ton of $1.99. These two Tollemache figures are based
135
-------
on the weight of refuse as received at the plant and include increased
labor costs incurred during the second evaluation.
15. For a two-mill, two-shift operation during the first 6 months
of 1972, a milling cost of $3.90 per ton was determined, based on 23,317
tons milled; another $0.48 per ton must be added to this figure to cover
compaction and hauling less than 1/2 mile. The operating costs of land-
filling for the first 6 months of 1972 in Madison were $0.99 per ton for
milled refuse and $3.00 per ton for unprocessed refuse, excluding any
land and development costs. During this period, regular sanitary land-
fills in Madison handled about twice as much material as did the milled
refuse landfill.
16. Based on the findings of this study, a cost of $3.11 per ton
of milled refuse was projected for a two-shift, two-Tollemache-mill
operation. This figure includes milling, hauling less than 1/2 mile,
and landfilling and assumes a continuous supply of millable refuse.
The City of Madison will continue milling refuse at the 01 in?Avenue
Milling Plant. In the Summer of 1973, the 01 in Avenue Mil Ifill operation
will be completed. The City has recently acquired another landfill
approximately nine miles from the milling plant. The milling plant will
serve as a central processing and transfer station from which the milled
refuse will be hauled to the new millfill facility.
136
-------
APPENDIX A
COST PROJECTIONS FOR NEW MILLING PLANTS AND LANDFILLS
This segment of the report includes detailed data in respect to
operating requirements and cost projections for a combination of one
through four mills operated either one or two operating shifts with
one maintenance shift. The estimates given in this portion of the
report are based on data collected utilizing the Tollemache vertical
shaft hammer-mill in Madison, Wisconsin. It is important to realize
that the cost projections have been developed on the basis of costs
at Madison. The wage rates, power and utility rates, depreciation, etc.
are all based on 1972 Madison cost data. To arrive at projected costs
for similar operations an economic study following the lines of that pre-
sented below may be made using the appropriate base rates as applied to
the area being studied.
Basic Design Criteria
The following design criteria were used in plant design and eventual
cost projections:
(1) Each mill will operate an average of 7 hours per shift at
a rate of 14 tons per hour.
(2) The plant will operate 245 days or 49 weeks per year. Three
weeks are allowed for repairs and breakdowns.
(3) The milling production day (one or two milling shifts) will
be followed by an eight-hour maintenance shift.
(4) Each plant will have as many feed conveyors as mills. One
and two mill plants will have one discharge conveyor and one
stationary compactor.
(5) Plants containing 3 or 4 mills will have two discharge con-
veyors and two stationary compactors.
(6) Cost projections are primarily based on pilot plant and
two shift studies conducted with the equipment mentioned
in the text.
(7) All pertinent data as to wage rates, utility rates,
depreciation, etc. are based on the evaluation data
from Madison.
Annual Tonnage
Each Tollemache mill operating one shift will have a daily capacity
of 14 tons/hour x 7 hours/day, or approximately 100 tons per day. The
corresponding annual tonnage for one mill shift will be 100 tons/day x
137
-------
245 days/year = 24,500 tons per year. Dally and annual tonnages for
combinations of mills and shifts are listed in Table A-l.
TABLE A-l
Daily and Annual Tonnage Processed for
Combinations of Mills and Shifts
Number of Mills
1234
One Shift
Daily Tonnage 100 200 300 400
Annual Tonnage 24,500 49,000 73,500 98,000
Two Shifts
Daily Tonnage 200 400 600 800
Annual Tonnage 49,000 98,000 147,000 196,000
Size of Plant
Experience has shown refuse quantities to vary throughout the year.
Peak tonnage rates are about 1.5 times the average daily tonnage. Good
plant design involves increasing available storage to allow for mill
breakdowns, etc. A factor about 1.5 times the average daily tonnage
through the plant is used to determine storage space. The maximum storage
requirement then becomes 150 percent of the average daily tonnage processed
on a one shift basis and is reduced to 125 percent of the daily tonnage
processed on a two shift basis. The reduction in excess capacity is due
to an increase in scale.
The maximum storage which must be provided is listed in Table A-2.
The values in Table A-2 were determined by multiplying the daily tonnage
in Table A-l by 150 percent for plants operating one shift, and by 125 per-
cent for plants operating two shifts.
TABLE A-2
Maximum Storage Requirements for
Combinations of Mills and Shifts - Tons
Number of Mills
1234
One Shift 150 300 450 600
Two Shifts 250 500 750 1,000
Assuming a density of 400 pounds per cubic yard on the dumping floor,
and an average stacked storage height of 8 feet, 0.53 ton can be stored per
square yard of floor space, or 0.059 tons per square foot of floor space.
The square footage of floor storage is computed by dividing the tonnages
in Table A-2 by 0.059 ton per square foot.
138
-------
TABLE A-3
Square Footage of Floor Storage Space Required
For Combinations of Mills and Shifts
Number of Mills
1234
One Shift 2,500 5,000 7,500 10,000
Two Shifts • 4,300 8,500 12,700 17,000
The total plant size including refuse storage space on the floor, con-
veyors and mills, and office is tabulated below. (A plant with three or
four mills will be considered to be equipped with two discharge conveyors
and two stationary compactors.)
TABLE A-4
Total Plant Size - Square Feet
Number of Mills
1 2 3 4
One Shift
Office & Workshop 1,000 1,000 1,500 1,500
Employee Facilities 300 300 500 500
Conveyor(s), Mill(s)
and Compactor(s) 3,500 5,000 9,000 10,500
Floor Storage-
Refuse 2,500 5.000 7.500 10.000
TOTAL 7,300 11,300 18,500 22,500
Two Shifts
Office & Workshop 1,000 1,000 1,500 1,500
Employee Facilities 500 500 700 700
Conveyor(s), Mill(s)
and Compactor(s) 3,500 5,000 9,000 10,500
Floor Storage-
Refuse 4.300 8.500 12.700 17,000
TOTAL 8,800 15,000 23,900 29,700
139
-------
The cost of foundations and building is computed by multiplying the
total space requirements in Table A-4 by $20 per square foot. The entrance
road and site grading is computed on the basis of 20 percent of the founda-
tions and building construction costs.
TABLE A-5
Cost of Foundations, Buildings, Entrance, Roads, and Grounds
For Combinations of Mills and Shifts
One Shift - Foundations and
Buildings $146,000 $226,000 $370,000 $450,000
- Entrance Roads
and Grounds 29,200 45,200 74,200 90,000
TOTAL $175,200 $271,200 $444,200 $540,000
Two Shift - Foundations and
Buildings $176,000 $300,000 $478,000 $594,000
- Entrance, Roads
and Grounds 35,200 60,000 95,600 11,900
TOTAL $211,200 $360,000 $573,600 $605,900
Labor Requirements and Costs
The number of men needed to man the combination of mills and shifts
under consideration are shown in Table A-6 as are the annual costs of labor.
Past experience at Madison has shown the need for proper supervision at all
levels of plant operation; thus, one supervisor is required for each case
shown. Also included are two maintenance men for one and two mill installa-
tions and three maintenance men for three and four mill installations. These
men will work an 8-hour maintenance shift following each day's milling
operation, whether one or two milling shifts are used.
Mill Maintenance - Annual Cost
(1) Hammers - 1100 tons/set at $106 per set
(2) Shafts - 500 tons/shaft at $l2.00/shaft
(3) Wear Plates - 20,000 tons/set at $1600 per set
(4) General Maintenance:
Mill - replace bearings and rotor once every three years for
one shift operation, $2,500 for each mill operating one
shift, and 80 percent additional for second shift.
Conveyors - $600 for the feed conveyor, and $200 for each dis-
charge conveyor for one mill operating one shift. The
cost for the second shift will be an additional 80 percent.
140
-------
(5) Welding Rods - 34 rods/set at $.50/rod; or $17.00 per set of hammers
50 Ibs./liner set at $1.60/lb.; or $80.00 per set of liners.
(6) Plant Supplies - $1,200 per one mill shift; $500 additional for each
mill; 50 percent additional for second shift.
TABLE A-6
Annual Labor Requirements and Costs
Number of Mills
Hourly Annual
Wage* Wage
One Shift
Supervisor $6.26** $13,000
Reduction Plant
Foreman-Operator $8.02 $16,660
Reduction Plant
Operator $7.21 $14,990
Public Works
Maintenance Man $6.20 $12,890
Scale Man $4.73 $ 9,840
Total
Two Shifts
Supervisor $6.26 $13,000 1111
Reduction Plant
Foreman $8.02 $16,660 2224
Reduction Plant
Operator $7.21 $14,990 2344
Public Works
Maintenance Man $6.20 $12,890 2233
Scale Man $4.73 $ 9,840 - 122
70,430
$ 85,420
$108,150
$139,800
Total $102,080 $126,910 $164,630 $197,950
*lncluding 30 percent fringe benefits and estimated overtime.
**0ther employees salary higher due to longevity pay program in City of Madison.
141
-------
TABLE A-7
Annual Mill Maintenance Costs
Number of Mills
One Shift
(1) Hammers
(2) Shafts
(3) Wear Plates
(4) General Maintenance
Mill(s)
Conveyor(s)
(5) Welding Rods
(6) Plant Supplies
Total
580
370
1,160
1,600 3,860
2,500 5,000
800 1,600
740
1.200 1,700
1,740
5,760
2,800
1,110
2.200
$ 2,330 $ 4,660 $ 6,990 $ 9,320
2,320
7,680
7,500 10,000
4,000
1,480
2,700
$ 8,580 $18,720 $28,100 $37,500
Two Shifts
(1) Hammers
(2) Shafts
(3) Liners
(4) General Maintenance
Mill(s)
Conveyor(s)
(5) Welding Rods
(6) Plant Supplies
Total
$ 4,660 $ 9,320 $13,980 $18,640
1,160 2,320
1,440 2,800
740 1,480
1,800
2,550
5,480
3,868 7,680 11,520
5,040
2,220
3,300
4,640
15,360
4,500 9,000 13,500 18,000
7,200
2,960
4,050
$18,160 $35,150 $53,040 $70,850
142
-------
Power for Mills, Conveyors, and Stationary Compactor
(1) The maximum demand for each mill and conveyor system is 160 kw.
(2) The maximum demand for the compactor is 20 kw.
(3) The power consumption for each mill and conveyor system averages
8.8 KWH/ton.
(4) The power consumption for each compactor is 16 KWH/hour.
The monthly demand charge for one mill and conveyor system is:
$2.00 for the first 10 kw, $2.00 per kw for each of
the next 90 kw, and $1.00 per kw up to the 160 kw
required for a total of $242
The monthly demand charge for each additional mill and conveyor system is:
$1.00 x 160 kw = $160
The monthly demand charge for each compactor is:
$1.00/kw x 20 kw = $20
The power consumption for one mill and conveyor system operating one
shift is 8.8 KWH/ton x 14 tons/hour = 123.2 KWH/hr. The monthly con-
sumption then is 123.2 KWH/hour x 7 hours/day x 5 days/week x 4.0
weeks/month = 17,250 KWH/month. The monthly consumption cost for one
mill operating one shift is: 0.026 x 500 KWH + $0.015 x 1000 KWH
+ $0.011 x 8500 KWH + $0.010 x 7,250 = $194. The monthly consumption
for all additional mill-shifts is $0.010 x 17,250 KWH = $172. The
monthly power consumption for each compactor working each shift is
16 KWH/hr x 7 hrs./shift day x 5 days/week x 4.0 weeks/month = 2,240
KWH/month. The corresponding monthly consumption cost for each com-
pactor shift is $0.080 x 2,240 KWH « $22. The above listed power con
sumption costs are summarized as follows:
The monthly power consumption cost for the first mill-shift
is $194.
The monthly power consumption for all additional mill-shifts
is $172.
The monthly power consumption cost for all compactor-shifts
is $22.
143
-------
TABLE A-8
Annual Power Costs for Mill(s)
Conveyor(s), and Compactors
Number of Mills
Lighting
One Shift
Demand
First Mill $242 $ 242 $ 242 $ 242 $ 242
Each Addnl. Mill 160 - 160 320 480
Each Compactor 20 20 20 40 40
Power Consumption
First Mill-Shift 194 194 194 194 194
Each Addnl. Mill-Shift 172 - 172 344 516
Each Compactor-Shift 22 22 22 44 44
Total Monthly Charge $ 478 $ 810 $ 1,184 $ 1,516
Annual Charge $5,736 $9,720 $14,208 $18,192
Two Shifts
Demand $242 $ 242 $ 242 $ 242 $ 242
Each Addnl. Mill 160 - 160 320 480
Each Compactor 20 20 20 40 40
Power Consumption
First Mill-Shift 194 194 194 194 194
Each Addnl, Mill-Shift 172 172 516 860 1,204
Each Compactor-Shift 22 44 44 88 88
Total Monthly Charge $ 672 $ 1,176 $ 1,744 $ 2,248
Annual Charge $8,064 $14,112 $20,928 $26,976
The consumption is to be proportioned on the basis of:
(1) The actual consumption in the reduction plant for one shift
from July 1970 through December 1970, and for two shifts from
January through June of 1972.
(2) The relative sizes of the buildings.
The original building used for a one-shift operation was 60 ft.
x 100 ft. = 6,000 sq. ft. The expanded building used for the two-shift
operation is approximately 13,000 sq. ft. The ratio of floor space for
144
-------
the projected plants, as listed in Table A-9 to 6,000 sq. ft. or 13,000
sq. ft. where applicable, is the relative size factor. The relative
sizes are:
TABLE A-9
Relative Sizes of Buildings
Number of Mills
One Shift 7,300 = 1.22 11,300 = 1.88 18,500 = 3.08 22,500 = 3.75
6,000 6,000 6,000 6,000
Two Shifts 8,800 - .68 15,000 = 1.15 23,900 - 1.84 29,700 « 2.28
13,000 13,000 13,000 13,000
Table A-10 shows the actual consumption for the existing plant per month
studied, and the proportional usage based on relative building sizes, for one
shift. Table A-11 contains the same information as related to a two-shift operation.
TABLE A-10
Actual and Proportioned Power Consumption (KWH)
For Lighting-One Shift
Actual KWH Number of Mills
Month Consumption 123 4
July 1970 4,414 5,385 8,298 13,595 16,552
August 1970 4,104 5,007 7,715 12,640 15,390
September 1970 4,018 4,902 7,554 12,375 15,068
October 1970 5,860 7,149 11,017 18,048 21,975
November 1970* 5,900 7,198 9,109 18,172 22,125
December 1970* 5,400 6,588 10,152 16,632 20,250
Average 6,038 8,974 15,243 18,560
*Figures adjusted - due to construction
145
-------
TABLE A-11
Actual and Proportional Power Consumption (KWH)
For Lighting-Two Shifts
Actual KWH Number of Mills
Month Consumption 1 23
January 1972 18,788 12,775 21,606 34,570 42,836
February 1972 17,088 11,620 19,651 31,442 38,960
March 1972 19,286 13,114 22,179 35,486 43,972
April 1972 14,734 10,019 16,944 27,110 33,593
May 1972 12,772 8,650 14,687 23,500 29,006
June 1972 13,294 9,040 15,288 24,460 30,310
Average 10,868 18,393 29,590 36,446
Based on the data given in Tables A-10 and A-11 a fairly good monthly average
of lighting power consumption for a one and two-shift operation can be obtained.
Table A-12 contains this average in relation to number of mills.
TABLE A-12
Average Monthly Power Consumption (KWH)
For Lighting One and Two Shifts
Number of Mills
123
One Shift 6,038 8,974 15,243 18,560
Two Shift 10,868 18,393 29,590 36,446
The demand charge would also be proportional to the size of the
building, but would be nearly constant throughout the year because the
charge is based on the high during the preceding 12 months. The maximum
demand for the original one-shift plant was 20 kw and for the two-shift
plant 40 kw. The maximum demand to be expected in any of the projected
plants is calculated by multiplying 20 kw or 40 kw whichever is applicable
by the relative building sizes as listed in Table A-9. The maximum demand
is tabulated below.
146
-------
TABLr. ^
Maximum Demand For Lighting - kw
Number of Mills
1/34
One Shift 24 38 62 75
Two Shifts 27 46 74 91
The annual cost of lighting can be computed using the monthly average
consumption (KWH) and maximum demand as shown in Tables A-12 and A-13 and th
current utility rates. Table A- 14 contains the summary of lighting costs.
TABLE A- 14
Annual Cost of Lighting for Combinations
Of Mills and Shifts
Number of Mills
1 2 3 4
One Shift
Demand $ 120 $ 696 $1,272 $1,584
Consumption 936 1,320 2,148 _ 2,592
Total $1,056 $2,016 $3,420 $4,176
Two Shi
Demand $ 432 $ 888 $1,560 $1,968
Consumption 1,572 2,568 4,044 _ 4,944
Total $2,004 $3,456 $5,604 $6,912
•'^•^PWABMMH^V^^VBM^^Bff'^^M'^^i^M^i^^M^^i^^^^^BIV^'VHlMfeMi^^B^BPVlVHMBBV^BB^HW^VI^^^^b'^VB^hlM'^^^^HmilVfl^B^V^I^^^*
Gas Heat
The gas costs are computed in a similar manner as for lighting costs
because consumption is dependent on building size. The actual consumption
is to be proportioned on the basis of:
(1) the actual consumption in the reduction plant for one shift
from July 1970 through December 1970, and for two shifts from
January through June of 1972, and
(2) the relative sizes of buildings.
The relative building sizes have been previously computed and are
shown in Table A-9 . The actual gas consumption for the existing plant,
and the proportioned usage based on relative building size are shown in
the following two tables.
147
-------
TABLE A-15
Actual and Proportioned
Gas Consumption (Heat) - One Shift
Month
July 1970
August 1970
September 1970
October 1970
November 1970
December 1970
Average
Actual
Consumption
(Cu.ft.xlOO)
0
0
30
780
3,420
3,600
0
0
37
952
4,173
4,392
1,590
Number of Mills
2 3
0
0
56
1,466
6,430
6,768
2,450
0
0
92
2,402
10,533
11,088
4,020
0
0
112
2,925
12,825
13,500
4,890
The consumption for two shifts is listed in the following table. The
proportioned consumption was obtained by multiplying the relative building
size by actual consumption used in the expanded plant under two-shift operation.
TABLE A-16
Actual and Proportioned
Gas Consumption (Heat) - Two Shifts
Month
January 1972
February 1972
March 1972
April 1972
May 1972
June 1972
Average
Actual
Consumption
(Cu.ft.xlOO)
8,679
8,297
5,124
1,983
618
540
5,900
5,640
3,480
1,350
420
370
2,860
Number of Mills
2 3
9,980
9,540
5,890
2,280
710
620
4,840
15,970
15,270
9,430
3,650
1,140
990
7,740
19,790
18,920
11,680
4,520
1,410
1,230
9,590
148
-------
Since only 6 months of good gas consumption data for a one and two
shift operation at Madison is available, only a rough estimate of gas costs
can be calculated. This estimate is computed by doubling the total cost
figure obtained from the proportioned consumption as presented in Tables A-15
and A-16. The estimate is valid because each six-month's term studied con-
tains equal periods of warm and cold weather in relation to that period not
studied. Table A-17 contains the projected yearly costs for gas as heat, based
on natural gas rates in effect at the time of evaluation*
TABLE A-17
Annual Cost of Gas (Heat)
One and Two Shifts
Number of Mills
1234
One Shift $1,746 $2,580 $4,104 $4,950
Two Shifts $2,976 $4,902 $7,722 $9,516
Water and Sewer
The usage is proportional to the tonnage milled, and has been found
to cost $0.002 per ton. Rather than going through the tedious procedure
used for estimating lighting and gas costs, the water and sewer costs are
estimated by multiplying the annual tonnage by $0.002 per ton. This method
is felt to be valid because the cost per ton was nearly constant throughout
the periods tested, and because the volume consumed is low enough that the
same utility rate applies.
TABLE A-18
Annual Water Costs for Combinations
Of Mills and Shifts
(Based on Cost of $0.002 Per Ton)
Number of Mills
1234
One Shift $49 $ 98 $147 $196
Two Shifts $98 $196 $294 $392
Tractor and Transfer Trailer Requirements
The number of trailers and tractors required is computed below. Based
on actual data a 70-yard trailer loaded with 15 tons of milled refuse would
have a density of 430 Ibs. per cubic yard. Each trailer is limited to
15 tons because of State highway regulations. Past experience has shown
that switching and unloading of each trailer averages 30 minutes when the
plant is located on the fill site. At a mill production of 14 tons per hour
one mill will fill one trailer in 64 minutes. Two mills operating at 14 tons
per hour each will fill one trailer in 32 minutes. Thus a one mill plant
will need a minimum of two trailers. A two mill plant could also function
with only two trailers; but would be advised to have three to minimize pro-
duction down time because of trailer breakdowns or delays in the switching-
unloading process. Both a one mill and two mill plant would require only
one tractor to pull the trailers. The above data would be applicable to a
one shift or two shift operation.
149
-------
As mentioned previously any three or four mill plant should contain
two stationary compactors. Taking this and the above data into considera-
tion > a three mill plant would require four trailers and a four mill plant
five trailers. Each three and four mill plant should be equipped with a
minimum of two tractors. Table A-19 summarizes the above data.
TABLE A-19
»
Tractor and Trailer Requirements
Number of Mills
123
One Shift
Tractors 1123
Trailers 2345
Two Shift
Tractors 1123
Trailers 2345
Annual Tractor and Transfer Trailer Operation and Maintenance Costs
Maintenance on the tractors and trailers is charged on a mileage basis;
$0,20/mi. for tractors and $0.25/mi. for trailers. To compute maintenance
costs it is first necessary to determine the number of loads taken to the
fill site; based on the information given above.
TABLE A-20
Number of Loads Per Day
Number of Mills
1234
One Shift 7 14 21 28
Two Shifts 14 28 42 56
The annual operating cost for the tractors can be computed as follows :
multiply the number of daily trips by round trip distance traveled, 0.5 mile
in Madison, x $0.20/mi. x 245 operating days/year. The computation for the
trailers is the same except $0.25/mi. is used instead of $0.20/mi. The ap-
propriate annual cost for tractor and trailer maintenance is shown in Table A-21.
150
-------
TA8LK A-2\
Annual Operation and Maintenance Cost
For Tractor and Transfer Trailer Operation Per Unit
Number of Mills
1 JL 3 4
One Shift
Tractors
Trailers
Total
Two Shifts
Tractors $344 $ 688 $1,032 $1,376
Trailers 430 860 1,290 1,720
Total $774 $1,548 $2,322 $3,096
$172
215
$387
$
$
•••V^^^v*
344
430
774
$
$1
^^^WPB«
516
645
,161
$
$1,
688
860
548
Annual Stationary Compactor Maintenance Costs
Past studies conducted at the Madison plant have revealed that on the
average, stationary compactor maintenance has cost approximately $0.02/ton,
based on a one shift operation. It would be reasonable to assume that a
50 percent increase in costs would be experienced when the machinery is
operated on a two shift basis. Using these figures as a guide the annual
operating costs for the combination of shifts and mills being studied is
shown in Table A-22. It should be reemphasized that all three and four mill
plants are designed for two compactors.
TABLE A-22
Annual Stationary Compactor Maintenance Costs
Number of Mills
1 2 3 4
One Shift
First Compactor $ 480 $ 960 $ 960 $ 960
Second Compactor _- - 4-80 960
Total $ 480 $ 960 $1,440 $1,920
Second Shift
First Compactor $1,440 $2,880 $2,880 $2,880
Second Compactor _^ - 1,440 2,880
Total $1,440 $2,880 $4,320 $5,760
151
-------
Annual Front End Loader Operation and Maintenance
For one and two mill operations a small end loader would be sufficient
to handle all tonnage processed. For a three and four mill plant, a medium
range end loader would be required. The operation and maintenance of both
pieces of equipment is assumed to cost $4.25/hr. The end loader will operate
5 hours and 10 hours per day for a one mill, one shift and one mill, two shift
operation, respectively. The same piece of machinery will operate 6 hours and
12 hours per day for a two mill, one shift and two mill, two shift operation,
respectively. The end loader will operate 7 and 14 hours for a three mill,
one and two shift operation, and 7 and 14 hours for a four mill, one and two
shift operation, respectively.
TABLE A-23
Annual Operation and Maintenance Costs
For Front End Loader
Number of Mills
1234
One Shift $ 5,205 $ 6,246 $ 7,287 $ 7,287
Two Shifts $10,410 $12,492 $14,575 $14,575
Amortization*
Amortization data and annual costs are listed below for all depreciable
items .
Building
Amortize over 20 years at 4.0 percent interest, salvage estimated at
3.0 percent of original cost as contained in Table A-5.
^Amortization or annual cost is calculated on the basis of the following
equation: **•
A.C. = (P-L) (CRF) - Li
where A.C. = annual cost
P = initial investment
L = salvage value
CRF = capital recovery factor
i% = interest rate
N - rated full life
The interest rate, i%, used in the computations > is a function of the
expenditure involved; i.e., short term notes or long term bonds. The
City of Madison usually funds large expenditures by long term bonds.
The interest rates in effect at the time of writing are 4.0 percent on
long term bonds.
Grant, Eugene L. and Ireson, W. Grant. Principles of Engineering
Economy, Fourth Edition. New York: The Roland Press, 1964.
152
-------
TABLE A- 2 4
Annual Cost o' Voum'..-i( UM\ .itu'
One Shift
Two Shifts
Number of Mills
23
$12,720 $19,690 $32,250 $39,200
$15,330 $26,130 $41,640 $43,980
TABLE A-25
Amortization* Data and Annual Costs
Cost Item
Depre- Int.
Original ciation Rate, Salvage Annual
Cost Rate-Yrs. % Value Cost
Scale
$15,000
20
4.0 $ 1,000 $ 1,076
Front Endloader
Michigan
Case
Trailers (ea)
Tractor (ea)
$32,000
$22,000
Grinder and Conveyor (ea) $140,000
Stationary Compactor (ea) $ 22,000
$ 19,000
$ 15,000
12
12
15
15
12
15
4.0 $ 5,000 $ 3,089
4.0 $ 3,000 $ 2,153
4.0 $ 4,000 $12,400
4.0 $ 1,000 $ 1,930
4.0 $ 750 $ 1,982
4.0 $ 1,500 $ 1,275
Annual Projected Operating and Amortization Costs
For Combinations of Mills and Shifts
Tables A-26 and A-27 summarize all costs of operating the various
sized plants and the amortization rates of each.
*NOTE: This is not a surplus fund for replacement of equipment, but
reflects municipal approaches for amortization.
153
-------
TABLE A-26
Annual Cost for One Through Four Mills - One Shift
Number of Mills
123
Labor
Mill Maintenance
Power - Mills, Conveyors,
and Compactors
Lighting
Gas (Heat)
Water
$ 70,430 $ 85,420 $108,150 $139,800
8,580 18,720 28,100 37,500
5,740
1,060
1,750
9,720 14,210 18,190
50
2,020
2,580
100
3,420
4,100
4,180
4,950
150
200
Tractor and Trailer Operations
and Maintenance 390
Front End Loader Operation
and Maintenance
Compactor Maintenance
5,210
480
770
6,250
960
1,160
7,290
1,440
1,550
7,290
1,920
Subtotal, Operating Costs $ 93.690 $126.540 $167,920 $215.580
Amortization
Building
Scale
Front End Loader
Mill(s) and Conveyors
Stationary Compactor(s)
Trailers
Tractor(s)
$ 12,720 $ 19,690 $ 32,250 $ 39,200
1,080
2,150
1,930
3,960
1,280
1,080
2,150
1,080
4,090
1,930
5,940
1.280
3,860
7,960
2,560
1,080
3,090
12,400 24,800 37,200 49,600
3,860
9.940
3,840
Subtotal, Amortization $ 35.520 $ 56,870 $ 88,000 $110,610
Total Annual Cost
$129.210 $183.410 $255,920 $326,190
154
-------
TABLE A-27
Annual Costs for One Through Four Mills - Two Shifts
Number of Mills
Labor
$102,080 $126,910 $164,630 $197,950
Mill Maintenance
Power - Mills, Conveyors,
and Compactors
Lighting
Gas (Heat)
Water
Tractor and Trailer Operation
and Maintenance
18,160 35,150 53,040
70,850
8,060 14,110 20,930
2,000
2,980
100
3,460
4,900
200
5,610
7,720
290
26,980
6,910
9,520
390
780
1,550
2,320
3,100
Front End Loader Operation
and Maintenance 10,410 12,490 14,580 14,580
Compactor Maintenance
1,440
2,880
4,320
5,760
Subtotal Operating Costs $146,010 $201.650 $273.440 $336.040
Amortization
Building
Scale
Front End Loader
Mill(s) and Conveyors
Compactor(s)
Trailers
Tractor(s)
Subtotal Amortization
Total Annual Cost
$ 15,330 $ 26,130 $ 41,640 $ 43,980
1,080
2,150
1,930
3,960
1,280
1,080
2,150
1,930
5,940
1,280
1,080
3,090
12,400 24,800 37,200
3,860
7,960
2,560
1,080
3,090
49,600
3,860
9,940
3,840
$ 38.130 $ 63.310 $ 97.390 $115.390
$184,140 $264,960 $370,830 $451,430
155
-------
Landfilling Cost Projections
Landfill cost projections will be based on the tonnages processed by
each combination of mills and shifts discussed in the previous section.
Costs will include labor for compaction, machine operation and maintenance,
and equipment amortization. Land costs are excluded. No charges are pro-
jected for cover material since no daily cover is used when landfilling milled
refuse at Madison.
Labor and Equipment Requirements and Costs:
Projections based on data obtained at Madison reveal that one operator
utilizing a steel wheeled compactor can efficiently handle 300 to 360 tons of
milled refuse per day. Based on this projection and the assumption that
landfills adjacent to the projected plant operations will be operated only
one 8-hour shift per day, the following labor and equipment requirements
are made,
TABLE A-28
Daily Landfill Labor and
Equipment Requirements
Number of Mills
1234
One Shift
Tons per day
Man Shifts
Trash Pak(s)
Two Shifts
Tons per day
Man Shifts
Trash Pak(s)
100
1
200
200
400
300
600
400
800
156
-------
TABLE A-2 9
Annual Labor Costs - Landfill Operations
Number of Mills
Annual*
Employee Wage
Operator $13,000 $13,000 $13,000 $13,000 $13,000
Site Control 11,300 5,650 5,650 11,300 11,300
One Shift Supervisor 15,100 3.800 3,800 7,500 7,500
TOTAL $22,450 $22,450 $31,800 $31,800
Operator $13,000 $13,000 $13,000 $26,000 $26,000
Site Control 11,300 5,650 11,300 11,300 11,300
Two Shift Supervisor 15,100 3,800 7,500 15,100 15.100
TOTAL $22,450 $31,800 $52,400 $52,400
^Includes 30% fringe benefits excluding overtime.
To compute equipment operating and maintenance costs it is assumed
that the landfill compactor will operate a minimum of 2 hours per 8 hour
day and a maximum of 6 hours per 8 hour day at the rate of spreading and
compacting 45 to 65 tons of milled refuse per hour. Operation and maintenance
for landfill equipment are charged at the rate of $6.25/hour of operation.
Compactor amortization is charged at the rate of $5,960 per year for an
initial investment of $45,000 and an 8-year equipment life.
TABLE A-30
Annual Operating and Maintenance Costs -
Landfill Equipment
Number of Mills
1 2 3 4
One Shift
Hours 990 1,225 1,470 1,715
Compactor Cost $6,130 $ 7,660 $ 9,190 $10,720
Misc. Equipment Cost 610 770 920 1,070
Total Cost $6,740 $ 8,430 $10,110 $11,790
Two Shifts
Hours 1,225 1,715 2,940 3,430
Compactor Cost $7,660 $10,720 $18,380 $21,440
Misc. Equipment Cost 770 1,070 1,840 2,140
Total Cost $8,430 $11,790 $20,220 $23,580
157
-------
Total Annual Projected Landfilling Costs:
TABLE A-31
Annual Projected Landfilling Costs
Number of Mills
Landfill 123
One Shift
Labor $22,450 $22,450 $31,800 $31,800
Compaction Equipment -
Operation and
Maint enance 6,740 8,430 10,110 11,790
Subtotal Operating Costs $29,190 $30,880 $41,910 $43,590
Depreciation -
Compaction Equipment $5,960 $ 5,960 $11,920 $11,920
Total Operating Costs $35,150 $36,840 $53,830 $55,510
Two Shifts
Labor $22,450 $31,800 $52,400 $52,400
Compaction Equipment -
Operation and
Maint enance 8,430 11,790 20,220 23,580
Subtotal Operating Costs $30,880 $43,590 $72,620 $75,980
Depreciation -
Compaction Equipment 5,960 5,960 11,920 11,920
Total Operating Costs $36,840 $49,550 $84.540 $87,900
158
-------
Summary of Annual Milling and Landfilline Costs
TABLE A-32
Annual Cost of Milling, Milled Refuse Transfer System and Landfilling
One Shift
Number of Mills
234
Annual Tonnage
24,500 49,000 73,500 98,000
Reduction Plant & Transfer
Operating Costs $ 93,690 $126,540 $167,920 $215,580
Amortization 35,520 56,870 88,000 110,610
Total Reduction Plant
$129,210 $183,410 $255,920 $326,190
Cost Per Ton*
Millfill
Operation Costs
Amortization
Total Landfill
Cost Per Ton**
TOTAL ALL OPERATIONS
COST PER TON
$5.27
$3.74
$3.48
$3,33
$ 29,190 $ 30,880 $ 41,910 $ 43,590
5,960 5,960 11,920 11,920
$ 35,150 $ 36,840 $ 53,830 $ 55,510
$1.43
$0.75
$0.73
$0.57
$164,360 $220,250 $309,750 $381,700
$6.70
$4.49
$4.21
$3.90
*Cost includes amortization, labor, operating, and milled refuse haul to
landfill less than one-half mile round-trip distance. Land cost excluded*
**Millfill cost includes labor and equipment costs with amortization. Land
cost and site preparation costs are excluded.
1
159
-------
TABLE A-33
Annual Cost of Milling, Milled Refuse Transfer System and Landfilling
Two Shifts
Annual Tonnage
Reduction Plant & Transfer
Operating Costs
Amortization
Total Reduction Plant
Cost Per Ton*
Mlllfill
Operating Costs
Amortization
Total Landfill
Cost Per Ton
TOTAL ALL OPERATIONS
COST PER TON**
Number of Mills
234
49,000 98,000 147,000 196,000
$146,010 $201,650 $273,440 $336,040
38.130 63.310 97.390 115,390
$184,140 $264,960 $370,830 $451,430
$3.75
$2.70
$2.52
$2.30
$ 30,880 $ 43,640 $ 72,620 $ 75,980
5,960 5.960 11,920 11,920
$ 36,840 $ 49,600 $ 84,540 $ 87,900
$0.75
$0.50
$0.57
$0.45
$220,980 $314,560 $455,370 $539,330
$4.50
$3.20
$3.09
$2.75
*Cost includes amortization, labor, operating, and milled refuse haul to
landfill less than one-half mile round-trip distance. Land cost excluded
**Millfill cost includes labor and equipment costs with amortization. Land
cost and site preparation costs are excluded.
160
-------
APPENDIX B
POSITION ON LANDFILLING OF MILLED SOLID WASTE *
A. BACKGROUND
The landfilling of milled solid waste without daily soil cover began
in Europe with claims that it was an environmentally acceptable and economic
method of final disposal. In June of 1966, a solid waste demonstration
grant was awarded to Madison, Wisconsin to evaluate the European experience
and to determine the feasibility of landfilling milled solid waste without
daily cover in this country.
In January 1971, the Madison project personnel met with OSWMP personnel,
a consulting engineer, and entomologists from the Bureau of Community
Environmental Management .(USDHEW), to review the progress and findings to
date from the Madison project. OSWMP concluded that the policy governing
soil cover for milled solid wastes should be as stated in Sanitary Landfill
Facts:
"The compacted solid wastes must be covered at
the conclusion of each day, or more frequently
if necessary, with a minimum of six inches of
compacted earth.11
It was also concluded that further investigation at Madison and in
other geographic and climatic areas was needed to fully resolve the
policy issue. In a February 2, 1971 memorandum, Mr. Richard Vaughan
expressed these findings to OSWMP Senior Staff and Regional Representatives.
Additionally, environmental evaluations of landfilling milled solid
waste made at the Madison demonstration site have been augumented by
information from site visits to other facilities. An increased interest
in the procedure is evidenced by the knowledge of six new sites being
planned, ten new sites under construction, and five sites operational.
Some of these sites are constructed and operated with provisional
approvals, some are operated in opposition to local regulations but in
all cases the operations do not adhere to the position stated by the
OSWMP on February 2, 1971.
Recent articles, based on European experience, findings from the
Madison project, and other new sites within the United States, have
appeared in engineering and public work journals. This information,
combined with equipment promotional activities has generated an increased
interest in the process particularly where problems exist in achieving
satisfactory sanitary landfill operations or where milling may compliment
resource recovery.
*This appendix, not a part of the grantee's original report, was prepared
and added by the Office of Solid Waste Management Programs, U.S. Environmental
Protection Agency.
161
-------
B, CURRENT POSITION
Landfilling milled solid wastes can be an environmentally accep-
table method of final disposal. The same sound engineering principles
involved in sanitary landfill sites, including a properly located,
designed, financed, and operated milling facility must be provided to
insure successful operations and to minimize adverse environmental
impacts. Since environmental, economical, and operational conditions
vary from existing sites, the need for cautious planning to meet local
conditions and to determine the feasibility of each new site must be
emphasized.
It must be recognized that this position is based on detailed
investigations at the Madison site augumented by general knowledge
from a few additional sites. The ability to mill, grind, or shred
wastes such that it is environmentally acceptable to landfill them
without daily cover is dependent on the process, its operation, and
local conditions such as the environment and the waste content.
It is, therefore, recommended that conditional approvals be given
by regulatory agencies contingent upon verification that the quality
of operation necessary to minimize environmental hazards is maintained.
Such verification should be supported by operational controls and
monitoring.
Except as modified below, the position statement on sanitary
landfill applies to milled solid waste disposal operation. Comments
relating milled solid waste to sanitary landfill requirements are
listed below in the order presented in the pending "Guidelines for
the Land Disposal of Solid Wastes.!!
1. As an alternative to sanitary landfill, landfilling milled
solid waste without daily soil cover can result in increased surface
water infiltration and accelerated decomposition which in turn can
result in earlier leachate production and temporarily increased
pollutional concentrations. Under the usual situation of landfill
construction over a period of years, peak leachate production and
concentrations occur only in a small part of the fill at any one
time. In areas where rainfall infiltration exceeds evaportrans-
piration and field capacity is reached, the total production of
leachate constituents has been shown to be equivalent to a sanitary
landfill which reaches field capacity and produces leachate.
Therefore, in accordance with the sanitary landfill position, it is
necessary to prevent leachate from entering surface or underground
sources of water supply. This can be accomplished by preventing
leachate production and/or by collecting and treating leachate
should it occur.
162
-------
2. As with sanitary landfill operations, design and operation must
conform to applicable air quality standards; specifically, open burning
of solid waste must be prohibited.
3. As with sanitary landfill cover, compacted, milled, uncovered
landfill surfaces must be left undisturbed to prevent odor. This does
not preclude vehicular traffic but precludes excavation of a finished
surface.
4. Although milling solid waste reduces the tendency for paper
to blow during placement, satisfactory control requires that the waste
be spread to a smooth contour and compacted promptly after placement.
5. A milled, uncovered solid waste landfill is much less
obnoxious than an open dump and to many observers is no more
obnoxious than bare earth,
6. Free venting or loss of gases from milled solid waste,
experienced in test cells, indicates that milled solid waste without
cover is less likely to trap gases in pockets or cause horizontal
gas migration. However, the addition of cover or possible migration
through fissures or broken pipe lines, etc. requires the same
attention to gas control as a sanitary landfill.
7. European experience, verified by tests at Madison, Wisconsin
and Purdue University indicates that:
Rats cannot extract sufficient food to sustain life;
from properly milled combined residential, commercial
solid waste (7-1/2 % organics wet weight in test) nor are
they attracted more readily to an uncovered milled solid
waste landfill than to a sanitary landfill (baiting studies);
the milling process kills nearly 100% of the maggots present
in incoming solid waste virtually eliminating fly emergence
(sampling studies); and flies are not attracted more readily
to an uncovered milled solid waste landfill (Scudder Grill
Study).
8. Undetected hazardous materials in incoming wastes have
been known to explode or ignite during the milling process. Protection
against explosions such as blow-off stacks and personnel shields
must be provided. Equipment to extinguish fires which may exist in
incoming solid waste or which may be ignited during the milling
process, during transport or on the landfill must be provided. No
operation should be located where birds might be a hazard to
aircraft flight operations.
163
-------
9. Site selection on an engineering basis is similar to that
for a sanitary landfill operation except the availability of daily
cover material is not required. The availability of emergency cover
is required (see operational plan requirements below). Final cover
and final use criteria should be the same as for a standard sanitary
landfill.
10. Only properly milled residential and commercial solid wastes
should be accepted in an uncovered milled solid waste landfill.
Items not accepted in a conventional sanitary landfill and volatile,
flammable, explosive or sludge wastes accepted in small quantities
at a conventional sanitary landfill, should not be accepted for
milling. Final disposal of all wastes not suitable for milling
must be in accordance with pending "Guidelines for the Land Disposal
of Solid Wastes."
11. All operations and aspects including lighting, dust control,
and noise levels must meet the requirements of the Occupational
Safety and Health Act of 1970. All solid waste storage areas must
be maintained and cleaned at the end of each day's operations, or
during continuous operation, as necessary, to prevent fly, rodent,
or other vector problems. All equipment must be maintained to
control spillage and to achieve a milled product quality necessary
to prevent environmental hazard.
12. All operational personnel must be specially trained and
instructed on the proper operation, maintenance, and safety
aspects of the facilities and equipment.
13. The operational plan must include provision for removal
and proper disposal of wastes within 24 hours should the mill
facility cease to meet the above conditions because of either a
temporary equipment breakdown or a loss of quality operation.
The operational plan must include provision of a stock pile of
emergency soil cover material and provision to convert the
operation to a sanitary landfill.
Preliminary project planning must include a detailed cost
analysis including means of establishing a sound financing and
revenue system, in order to guarantee that the quality of operation
necessary for environmental acceptability can be sustained. Milling
and landfilling residential and commercial solid wastes is usually
not cost competitive with conventional sanitary landfill disposal.
Cost comparisons to justify milling as an alternative to more
extensive disposal systems including transfer stations or cover
material transport must be evaluated on a local basis. Each
community or private operator must make their own thorough economic
evaluation of the alternative disposal systems. Milling costs
including labor, amortization, utilities, maintenance, and supplies
164
-------
recorded at and relevant only to the Madison project were as high
as $7.07/ton for a single 9 ton/hr. Gondard mill operating 5 to
6 hours a day. Costs for a single 15 ton/hr. Tollemache mill operating
about 5 hours a day have been recorded at $5.10/ton while costs for
a similar operation with "hard to mill" wastes ran as high as
$6.44/ton. Transportation to the adjacent landfill averaged about
$0,40/ton additional. Spreading and compacting costs averaged an
additional $0.50 ton. Cost projections for the. combined operation
of one Gondard mill at 9 ton/hr. and one Tollemache mill at 15 ton/hr.,
milling 280 tons/day or a two shift operation is approximately
$3.50/ton excluding transport and disposal. These costs reflect
local labor rates, union contracts, construction costs, and electrical
costs, etc.
C. REFERENCES
1. Ham, R. K., W. K. Porter, and J. J. Reinhardt. Refuse milling
for landfill disposal. JEn Solid Waste Demonstration Projects;
Proceedings of a Symposium, Cincinnati, May 4-6, 1971. Washington,
U.S. Government Printing Office, 1972. p.37-72.
2. Solid waste reduction/salvage plant; an interim report; City of
Madison pilot plant demonstration project, June 14 to December 31,
1967. Washington, U.S. Government Printing Office, 1968. 25 p.
3. Sanitary landfill guidelines. U.S. Environmental Protection Agency.
(in press.)
\
4. Brunner, D. R., and D. J. Keller. Sanitary landfill design and
operation. Washington, U.S. Government Printing Office, 1972. 59 p.
5. Stirrup, F. L. Public cleansing: refuse disposal. Oxford, Pergamon
Press, 1965. 144 p.
6. [Great Britain]. Bepartment of the Environment. Refuse disposal;
fceport of the Working Party on Refuse Disposal. London, Her Majesty's
Stationary Office, 1971. 199 p.
7. [Great Britain]. Department of the Environment. Report of the
Working Party on Refuse Disposal. Circular 26/71. Apr. 1971. 7 p.
ya555
165
-------