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[GreenYes] Re: Question about grinding of C&D Waste for landfill cover



Debra, this question was asked on our MSWlf list serve in 2005 and here
are the responses:


One of the landfills in Minnesota has proposed to use shredded
construction and demolition debris as an alternative daily cover. In
order to respond to this request, I am trying to gather some
information on the use of ground construction and demolition debris
used as alternative daily cover at lined landfills in other states.
Are there any states that have allowed shredded construction and
demolition debris to be used as an alternative daily cover? If yes,
what restrictions were placed on the use of this material as an
alternative daily cover? What types of restrictions were placed on its
contents? What types of experiences did you have? If it has been
proposed and was not authorized, what were some of your reasons for not
approving this use? Thanks in advance for your assistance. 2-4-05

Geoffrey D. Strack, Graduate Engineer 2
Minnesota Pollution Control Agency Municipal Division Solid Waste
Section
(651) 296-7716 (phone) (651) 282-6247 (fax)

Indiana allows the following construction/demolition material: rocks,
bricks, concrete and road demolition material to be used as ADC. The
standards for ADC are set in 329 IAC 10-20-14.1 I'm including a web
side link: http://www.in.gov/legislative/iac/T03290/A00100.PDF
Other materials than those listed in our regulations can be approved on
a case by case basis. I don't recall that we have approved in the past
mixed construction/demolition waste as ADC that would include dry wall.


Mr. Strack: Be careful in approving this use as to the proportion of
wallboard in the daily cover. We had one landfill I am aware of
provisionally approved for this in Virginia. The gypsum contains
calcium sulfate, and anaerobic bacteria produce hydrogen sulfide from
it, when it is wet and other food is present. The concentrations were
high enough that the HazMat team controlled access to the site for a
time, and an EPA OSC came to investigate. It was a very difficult
problem to resolve, using FML cover, negative pressure gas capture,
and flaring. Citizens' suit followed. This has been some years ago
now (1996-1997). There was a study done on a captive landfill
associated with a gypsum wallboard manufacturer in the northwest, but
I do not have it now.

Geoffrey, In Florida C&D recycling has been growing steadily over the
last 8 years or so and one of the recovered materials from these C&D
recycling operations has been the fines or Arecovered screen material@
(RSM) is the term we use. While not being shredded C&D, the RSM is
what falls out of the screening/picking lines and is soil-like in
nature. We have approved RSM as alternative daily cover at lined
landfills. Some other uses have been approved based on a
characterization of the RSM and comparison with specific criteria. The
protocol for characterizing RSM and the criteria for reuse is included
in a guidance document entitled AGuidelines for the Management of
Recovered Screen Material from C&D Recycling Facilities in Florida@
which is posted on our website at
http://www.dep.state.fl.us/waste/categories/solid_waste/pages/beneficialuse.htm
.


In Maryland we did an extensive study about 10 years ago when one of
our auto shredders wanted to branch out into this. They even patented
it under the trade name Recovermat. We had them add the material to
the shredder in accordance with different formulas of "heavy" vs.
"light" fraction of C&D (heavy = concrete, bricks, drywall, etc., while
light = wood, packaging, plastic, etc.), determined by eye. They also
had a lab do visual classification of the product for awhile, checking
for asbestos and the rough percentages of flammable vs. non-flammable
particles, although after awhile we found it really didn't make much
difference to the performance so we just let them grind up what cam
down the shoot, and they could use it for cover as long as it met some
minimum standards for non-flammable constituency.

In brief, we found that:
- it is generally adequate for most uses of cover - keeps the litter
down, stops birds and vermin from feeding, compacts nicely, etc.

- it is however porous - it readily lets rain in, and odor (and
landfill gas) out.

- due to the potential for fire, and to improve it's performance in
other ways, we require that a layer of intermediate cover, in this
state 1' of soil that is put over the waste after the completion of
each lift, be placed on more frequently, like every week or two
depending on the amount of waste the using landfill gets (a bigger
landfill is weekly, smaller biweekly).


- Use of the material at several landfills indicated that it generally
performs acceptably. HOWEVER, we did have a problem at two sites with
a link to the formation of hydrogen sulfide odors. One, in particular,
had a very nasty problem that developed. What happened was this - they
are a site located in the Coastal Plan that has extremely clay-rich
soil for daily cover. Unfortunately, in the rain the stuff gets really
slippery, so in addition to using the shredded C&D for daily cover,
they were putting some down as temporary access roads inside the cell,
to give better vehicular traction. They did this for a couple of
years, no problem. Then, a month or two after they received 12.5" of
rain in 24 hours during a tropical storm (live shots of the flooding of
Northeast, Md., which the landfill is just east of, made CNN) we
started getting complaints about a strong sulfury odor from the town.
It got worse - I personally measured over 100 PPM H2S at belt level
downwind of a couple of methane vents, before they put flares on 'em.
(I couldn't smell anything at all for 6 months after that little
adventure).

What had happened was that the water soaked into the fill, and then
perched on top of layers of that nice clayey cover - in the layer of
gypsum-containing shredded C&D. Since it had soaked thru a layer of
trash and was now leachate, you had exactly the right conditions needed
to manufacture hydrogen sulfide from gypsum - calcium sulfate, lots of
water, organic carbon, and an anaerobic atmosphere. They fixed it with
really good cover and an awful lot of flares. The problem occurred at
one or two of the other sites that used it too, but not nearly so
noticeably and it was quickly suppressed.

- So, what we do is, we still approve the stuff, but we do it with
conditions, and a warning that this can happen - and that they will be
required to jump on the odor problem if it develops.

- The one landfill quit using it but a few still do. We do have
ongoing slight odor problems at a couple of those sites, but I think it
is more related to the porosity of the cover than the H2S content - the
odors we are getting now are more a classic garbage smell than the
pronounced sulfur odor we had before. (After awhile it's just like
wine-tasting: "Ah, let's see...not too sweet, yet not too dry...a
subtle piquancy of sludge, with the heady flavor of
petroleum-contaminated soil...some crisp tannins from the wood and
cardboard...just a touch of industrial solvents and undertones of
incinerator ash...This is from Baltimore City garbage, buried about
August, 1983, before the fall rains...").

- I note that some (Massachusetts?) have banned gypsum from their
landfills, and it may be of interest to those in wet climates to
consider minimizing wallboard and plaster content in a C&D-derived
ADCM. We are not at that point, however.
If you need more on this please give me a call.



Kansas has not received any requests to use shredded C&D waste as
alternative daily cover material. This could be because soil is
readily available at most landfills, and other alternative cover
materials (tarps, low-level contaminated soil, spray-on slurry) are
probably more cost-effective than shredding C&D waste.


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