General Guidelines for S/S of Wastes - Stabilization and Solidification of Hazardous, Radioactive, and Mixed Wastes - page 20

such as excavation and landfilling. Of this total, about 40 to 50% goes to the cost
of the reagents used. 27

2.5 EVALUATION OF S/S FORMULATIONS

TCLP is the regulatory testing procedure in several countries and is sometimes used
as the only test for delisting hazardous wastes. However, the TCLP test has been
criticized for a long time, since the maximum amount of acid for the test is two
equivalents of acetic acid per dry gram of waste material. People can easily add
some alkaline materials to the waste based on the neutralization capacity to obtain
a leachate with a pH around 10, where most regulated heavy metals have the lowest
solubility. Although such treated wastes or remediated sites are regarded as environ-
mentally acceptable, they may still release contaminants into fresh water at a con-
centration higher than the concentration limits for TCLP testing. 28,29 The Science
Advisory Board of USEPA reviewed the leaching evaluation framework employed
by the agency in 1991 and 1999. 30,31 In the 1999 review, the Science Advisory Board
stated:

“The current state of the science supports, even encourages, the development and use
of different leach tests for different applications. To be most scientifically supportable,
a leaching protocol should be both accurate and reasonably related to conditions
governing leachability under actual waste disposal conditions.”

and:

“The multiple uses of TCLP may require the development of multiple leaching tests.
The result may be a more flexible, case-specific, tiered testing scheme or a suite of
related tests incorporating the most important parameters affecting leaching. Applying
the improved procedure(s) to the worst-case scenario likely to be encountered in the
field could ameliorate many problems associated with current procedures. Although
the Committee recognizes that these modifications may be more cumbersome to imple-
ment, this type of protocol would better predict leachability.”

The Science Advisory Board also criticized the TCLP protocol on the basis of
several technical considerations, including the test's consideration of leaching kinet-
ics, liquid-to-solid ratio, pH, potential for colloid formation, particle size reduction,
aging, volatile losses, and commingling of the tested material with other wastes (i.e.,
co-disposal).
On March 23, 2000, the USEPA published a guidance document on delisting,
entitled EPA RCRA Delisting Program Guidance Manual for the Petitioner . 32 Section
6.2.2 of the manual provides guidelines for stabilized wastes. If the petitioned waste is
generated from the chemical stabilization of a listed waste, then leachable metal con-
centrations should be tested using the Multiple Extraction Procedure (MEP), SW-846
Method 1320, as well as by TCLP analyses to assess the long-term stability of the waste.
The purpose of S/S is to maximize the containment of environmental contami-
nants by both physical and chemical means and to convert hazardous waste into an