The Washington State Department of Ecology (Ecology) is proposing changes to
the Model Toxics Control Act (MTCA) Cleanup Regulation (Chapter 173-340 WAC).
The rule revisions will update the policies and procedures for establishing and
evaluating compliance with cleanup levels and remediation levels for several
types of chemicals.
The Model Toxics Control Act (MTCA) was passed by Washington voters in
November 1988. The law establishes the basic authorities and requirements
for cleaning up contaminated sites. Ecology originally adopted cleanup
standards in February 1991. The Department completed significant changes
to the cleanup standards in February 2001. Under the revised rule, a
person undertaking a cleanup action may use the Environmental Protection
Agency’s toxicity equivalency factor (TEF) values and methodology when assessing
dioxin and furan mixtures. Later that year, Ecology published a guidance
document (Cleanup Levels and Risk Calculations (CLARC) that explains how to use
the TEF methodology when establishing cleanup levels.
In November 2005, the Rayonier Corporation filed a lawsuit challenging Ecology’s
use of the guidance document at the Port Angeles mill site. Rayonier
argued that the MTCA rule requires Ecology to establish cleanup levels for each
dioxin congener using a cancer risk level of one-in-one million (or 10-6 ) (as
opposed to applying 10-6 risk level to the whole mixture). In April
2006, Ecology settled the lawsuit and agreed that Rayonier's approach was also a
plausible interpretation of the current MTCA rule. Ecology agreed to settle the
lawsuit because neither the current MTCA rule nor the federal guidance
referenced in the MTCA rule explicitly require the procedures in the CLARC
Concurrent with the settlement discussions, several environmental organizations
submitted a rulemaking petition to Ecology in March 2006. These groups requested
that Ecology amend the rule to clarify that the policies and procedures
specified in the Ecology guidance should be used when establishing cleanup
levels for dioxins/furans and other similar mixtures. Ecology reviewed the
petition and decided to initiate a rulemaking process to address the issues
raised in the lawsuit and rulemaking petition. Ecology decided that amending the
MTCA rule to explicitly define key policy choices is preferable to repeatedly
resolving those policies on a site-specific basis.
Ecology initiated the rulemaking process on June 7, 2006 by filing the CR-101
with the Office of the Code Reviser. Later that month, Ecology prepared
draft rule language that was distributed to interested parties for review and
comment. Ecology held several meetings to discuss the draft rule
language and key rulemaking issues. Ecology received numerous
comments on the draft rule language. After reviewing those comments,
Ecology modified the draft rule language and incorporated additional revisions
that establish a new default Gastrointestinal Absorption Fraction (AB1) for
soil-bound dioxins and furans. Ecology also held four meetings with the
MTCA Science Advisory Board to discuss key rulemaking issues. Based
on the Board’s review, Ecology made further modifications to the proposed rule
in early 2007.
Summary of the Proposed Rule Changes
Ecology is proposing revisions to the policies and procedures for setting and
evaluating compliance with cleanup levels and remediation levels for certain
chemical mixtures. The changes apply to mixtures of dioxins and furans,
polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs). I
have attached a copy of the proposed rule language to this E-mail message.
The proposed revisions include:
Risk Policies Applicable to Certain Mixtures, Ecology is proposing
- Cleanup levels for dioxin and furan mixtures must be based on a cancer risk of
- Cleanup levels for PAH mixtures must be based on a cancer risk of
- Cleanup levels for PCB mixtures must be based on a cancer risk of
Toxic Equivalency Factors Used to Characterize Mixtures, Ecology is proposing to amend the rule to
incorporate the most recent toxicity equivalency factors (TEFs) for
dioxins/furans and PCBs recommended by the World Health Organization and updated
potency equivalency factors (PEFs) for carcinogenic PAHs adopted by the
California Environmental Protection Agency.
- Default Parameters Used to Calculate Cleanup Levels, Ecology is proposing to revise the default
Gastrointestinal Absorption Fraction used to establish soil cleanup levels for
dioxins and furans.
- Evaluating Cross-Media Impacts,Ecology is proposing to require that cleanup proponents
consider the physical-chemical properties of individual PAH compounds or
dioxin-congeners when evaluating cross-media impacts.
Opportunities for Public Review and Comment
Ecology will be filing the proposed rule with the Code Reviser on April 4,
2007. The public comment period will run from April 4 to May 25, 2007. If
you have comments on the proposed rule, please send them to:
Mr. Pete Kmet
Department of Ecology,
Toxics Cleanup Program
PO Box 47600
Olympia, WA 98504-7600
Ecology has scheduled three public hearings to receive written or oral
comments on the proposed changes to the rule. At each public hearing, an
overview presentation and question/answer period will be held prior to the start
of the official public hearing. Following are the dates, times, and locations of
the public hearings:
For more information or questions, please call (360) 407-7187 or 1-800-826-7716 or view the website at:
May 10, 2007 - 5:30 p.m.
St. Benedict School Auditorium
4811 Wallingford AVE N
May 14, 2007 - 5:30 p.m.
County Commissioners Board Room
Clallam County Courthouse
223 E 4th ST
May 17, 2007 - 5:30 p.m.
Department of Ecology
Eastern Regional Office
N 4601 Monroe ST, STE 100
Second Floor Conference Room
MTCA Rule Amendment
SEPA Determination of Non-Significance
Background Document for the Proposed
Amendments to MTCA
Click here for a consolidation of
all of the above documents.
Cost Benefit Analysis