February 3, 1988
SUBJECT: Stabilization of PCB-Contaminated Wastes
FROM: Marcia E. Williams, Director
Office of Solid Waste
Office of Toxic Substances
TO: William J. Muszynski, P.E.
Deputy Regional Administrator
This is in response to your letter of December 24, 1987, concerning
the stabilization and disposal of PCB-contaminated lagoon sludges and metal
hydroxide sludges at the SCA Chemical
Services facility in Model City, New York. Your specific issue concerns whether, under RCRA, a minimum unconfined compressive strength of 50 psi is required before placement of stabilized
bulk liquids in a hazardous waste landfill. The issue arises due to the January 16, 1987 Policy for Managing Leachate at PCB Landfills (pg. 8) referencing the OSWER Policy Directive #9487.00-2A, June 11, 1986.
Briefly, the January 16, 1987 Policy states that any PCB- containing
treatment residue (sludges or slurries) or PCB-containing phrases, which
are not incinerated, be stabilized in accordance with the OSWER guidance
on the "Liquids in Landfills Ban" prior to being placed in chemical waste
landfills. OTS referenced the OSWER Policy Directive as guidance
to the TSCA permit writer on method that can be used to determine whether
material is a non-liquid and, therefore, may be landfilled.
Some history concerning the development of the OSWER 50 psi unconfined compressive strength criterion is in order. Section 3004(c)(1) of HSWA prohibits the direct placement into a landfill of bulk liquids that have been solely treated by the addition of an absorbent (or adsorbent, according to the OSWER policy directive mentioned above.) Therefore, bulk wastes that are treated solely by the addition of an absorbent or adsorbent are prohibited from being placed in a landfill unless further treatment is performed. Bulk wastes to which no absorbents or adsorbents have been added are required to be tested by the Paint Filter Liquids Test (PFLT). If the bulk waste passes the PFLT (i.e., it is a solid) it is allowed to be disposed of in a landfill. If the bulk waste fails, then additional treatment, without the use of absorbents or adsorbents, is necessary before the waste can be landfilled.
The issue of 50 psi arises when further treatment is performed on the
bulk waste. One acceptable form of treatment is chemical solidification/stabilization.
It is acceptable because it is not a treatment technology that solely involves
the addition of an absorbents or adsorbent material. When reviewing
a solidification/stabilization process, if it is not obvious that a chemical
reaction has taken place (i.e., if there are any concerns that stabilization
is occurring primarily due to the addition of sorbents), then it is recommended
samples of the treated waste pass the unconfined compressive strength test with a minimum value of 50 psi.
The policy directive, however, is quite clear that meeting the 50 psi
value is neither a requirement nor a condition that must be applied in
all cases. It should be noted that the guidance states that if an
owner/operator using his/her data demonstrates to the permit writer that
something more than absorption or adsorption is occurring, then this is
acceptable and the 50 psi issue should not arise. One way to demonstrate
a chemical solidification/stabilization process is to demonstrate an increase
in strength over time for the treated waste. This
increase in strength would not have to reach a 50 psi value. For example, a day-one value of 3 psi for the treated waste and a 28-day value for 37 psi would be an acceptable increase in strength over time. In some cases, more data (i.e., various wastes to reagent recipes) may be required in order for the permit writer
to agree that an increase in strength over time has occurred.
In regard to the SCA facility, if a decision is reached that the previous treatment of the leachate did not involve the addition of absorbents or adsorbents, then the wastes (i.e., the salts and sludges) are only required to be tested using the Paint Filter Liquids Test. If they pass, the wastes are allowed to be disposed of in a landfill. If they fail, then additional treatment that does not solely involve the addition of an absorbent or adsorbent is required in order for the sludges to be bulk disposed.
If the decision is reached that previous treatment has solely involved the addition of an absorbent or adsorbent, then further treatment must be performed before the wastes are allowed to be bulk disposed. An acceptable form of treatment is chemical stabilization/solidification, as discussed above.
In order to determine that an "appropriate recipe" has been developed
and followed by the owner or operator for stabilization/solidification,
some data collection would still be necessary. This data collection
would enable the permit writer to determine that the wastes will be "effectively
encapsulated in the stabilized matrix." Data collection is necessary
to determine this "effective encapsulation in the stabilized matrix" because
a sufficient mixture of reagent to waste must be used to achieve an acceptable
increase in strength over time, as
If you should seek help in determining whether any previous treatment solely involved the addition of an absorbent or an adsorbent, then you should talk with the following people who can help make that determination. Carlton Wiles, of EPA ORD in Cincinnati, Ohio at FTS 684-7795 or John Cullinane of the Army Corp of Engineers in Vicksburg, Mississippi at 601/542-3723.
The discussion above relates to the OSWER policy directive mentioned
in the first paragraph. One point to consider is that if the Region's
sole intent is to provide SCA with a draft RCRA Section 3008(h) order,
this type of activity allows the Region to impose any type of response
measures to protect human health and
the environment. If the Region were to decide that the salts and sludges were not subject to the bulk liquids ban (i.e., Section 3004(c)(1) does not apply since no absorbent or adsorbent have been added and the wastes pass the PFLT), additional controls through the Section 3008(h) order could be imposed. If the salts
and sludges pass the Paint Filter Liquids Test, but do not have sufficient strength to support a final cover that would be placed over the landfill, then additional treatment of the salts and sludges could be undertaken to increase their strength so that a final cover will not experience settlement and subsidence.
If you should have any general questions concerning this
memo, please call Paul Cassidy of the Land Disposal Branch at
FTS-382-4682 or Denise Keehner of the Office of Toxic Substances