ILLINOIS POLLUTION CONTROL BOARD

July 10, 1997

IN THE MATTER OF:

TIERED APPROACH TO CORRECTIVE

ACTION OBJECTIVES (TACO): 35 ILL.

ADM. CODE PART 742.105, 742.200,

742.505, 742.805 and 742.915

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R97-12(B)

(Rulemaking - Land)

Proposed Rule. First Notice.

OPINION AND ORDER OF THE BOARD (by M. McFawn and J. Yi)

On April 17, 1997, the Board opened Docket B: Tiered Approach to Corrective Action

Objectives, also known as TACO. That same day, the Board adopted for second notice the

majority of the TACO rules under Docket A.

1

At second notice and at final notice during

Docket A, the Board adopted limited rules concerning the effect of similar-acting chemicals on

the same target organ (mixture rule) at the recommendation of the Agency. The TACO

program establishes a three tiered approach for establishing corrective action objectives, i.e.,

remediation objectives based on risks to human health and the environment, allowing for

consideration of the proposed land use at a subject site. The purpose of bifurcating the

rulemaking was twofold. Under Docket A, the Board could proceed to adopt the TACO

program as final at new Part 742 in tandem with R97-11:

The Site Remediation Program and

Groundwater Quality Standards

(June 5, 1997), which had a statutory adoption deadline of

June 16, 1997, and under Docket B the Board could conduct this rulemaking to consider a

single, outstanding issue. That issue now before the Board in this docket is how the effect of

similar-acting chemicals on the same target organ is to be taken into account when determining

remediation objectives under TACO. The need for a mixture rule originates at Section 58.5(c)

of the Illinois Environmental Protection Act (Act) (415 ILCS 5/58.5(c) (1996)) and from the

Board’s groundwater regulations at 35 Ill. Adm. Code 620.

As explained in our opinion of April 17, 1997, the Agency’s initial proposal addressed

mixtures of similar-acting chemicals under Tier 2. However, the Agency advocated expanding

the applicability of the initially proposed mixture rule in a series of filings subsequent to the

five public hearings held prior to that date. The justification offered by the Agency for

expanding the rule’s applicability was minimal. In fact, several commentators objected to

1

On June 5, 1997, the Board adopted the opinion and order in Docket A as final rules which

were published in the

Illinois Register

on June 27, 1997 at 21 Ill. Reg. 7942, with an effective

date of July 1, 1997.

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these proposed amendments suggested by the Agency as unsupported by the record developed

over the course of those hearings. Docket A PC 3,8,20, and 21.

2

While we found the record

before the Board insufficient to adopt the entire mixture rule ultimately requested by the

Agency prior to April 17, 1997, the justification provided by the Agency in support of

expanding the rule’s applicability did indicate that absent such a rule, remediation objectives

determined using TACO may not be protective of human health at sites with multiple, similar-

acting chemicals. Accordingly, a limited mixture rule was adopted under Docket A for second

notice on April 17, 1997 and as final on June 5, 1997. Docket B was opened to facilitate the

review of the mixture rule necessary to protect human health.

3

Under Docket A, the limited mixture rule at Tiers 1 and 2 applies only to similar-acting

noncarcinogenic

chemicals. Under Tier 1, the cumulative effect of similar-acting

noncarcinogenic chemicals must be evaluated for groundwater only, while under Tier 2 it must

be evaluated for soil and groundwater. 35 Ill. Adm. Code 742.505(b)(3), 720, 805(c)

(effective July 1, 1997.) These adopted rules, as well as the entire mixture rule subsequently

proposed by the Agency, have been evaluated under this Docket B.

Today we propose for first notice a mixture rule in each of the three tiers. The rules

proposed today are different from the limited mixture rules adopted in Docket A and those

proposed on April 17, 1997 in Docket B. Briefly, the mixture rule under Tier 1 requires that

the cumulative effects of both similar-acting carcinogenic and noncarcinogenic chemicals be

evaluated when determining groundwater remediation objectives. Accordingly, the current

rule at Section 742.505(b) that similar-acting noncarcinogenic chemicals be evaluated under

Tier 1 for groundwater is retained, but amended to include the same requirement for similar-

acting carcinogenic chemicals when the Tier 1 remediation objectives are exceeded or when

similar-acting carcinogenic chemicals have remediation objectives set at risk levels higher than

1 in 1,000,000. Similarly, the mixture rule proposed under Tier 2 which applies to similar-

acting noncarcinogenic chemicals is also retained, but amended to require that the cumulative

effect of similar-acting carcinogenic chemicals be evaluated when developing groundwater

remediation objectives. However, the Tier 2 mixture rule for soil remediation objectives

remains unchanged, applicable only to similar-acting noncarcinogenic chemicals. Finally, a

new requirement is added under Tier 3 which requires that both similar-acting noncarcinogenic

2

Docket A public comments and exhibits will be referred to as Docket A PC at __ and Docket

A Exh. at __, respectively; Docket B public comments and exhibits will be referred to as PC

at __ and Exh. at __; the Agency’s prefiled testimony will be hereinafter referred to as Exh. 2;

the May 21, 1997 hearing will be hereinafter referred to as Tr.1 at __; the May 29, 1997

hearing will be hereinafter referred to as Tr.2 at __.

3

On April 17, 1997, the Board adopted for first notice an order in Docket B which contained

proposed mixture rules. Because the Secretary of State had informed the Board that we could

not propose those rules for first notice until the rules in Docket A were finalized, on May 1,

1997 we vacated that first notice order. In its place, we adopted the same order and directed

the proposed amendments to hearing pursuant to our rulemaking authority under Sections 27

and 28 of the Act.

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and carcinogenic chemicals be evaluated for both groundwater and soil as part of the Tier 3

site-specific analysis.

The Agency has also proposed, in its prefiled testimony, that the Board adopt language

that the “requirements of 35 Ill. Adm. Code 620.615 regarding mixtures of similar-acting

chemicals shall be considered met for Class I groundwater at the point of human exposure” if

certain requirements under Tier 1 and Tier 2, respectively, are achieved. Exh. 2 at 4-5. Those

requirements are (1) that the level of the contaminant of concern does not exceed the Tier 1

remediation objective, and (2) that the remediation objective is based on a risk level of 1 in

1,000,000. Because we are adopting a mixture rule for both similar-acting carcinogenic and

noncarcinogenic chemicals under all three tiers, the Board accepts the Agency’s premise, but

modifies the language it proposed with the amendments adopted today for first notice.

The reasons for the mixture rule proposed today and the changes from the former

versions are explained in detail below. To familiarize the reader with the TACO approach, we

will begin with a brief summary of the TACO program adopted under Docket A, followed by

an explanation of the mixture rule and how it evolved over the course of Dockets A and B.

Next, the rationale for the mixture rule proposed today at Tiers 1, 2, and 3 is provided in

detail. Finally, the text of the amendments necessary to the new Part 742 to provide a mixture

rule is set forth in our order for first notice.

SUMMARY OF THE TACO PROGRAM

Again, the TACO process codified at new Part 742 provides a three tiered approach for

establishing remediation objectives based upon human health and the environment, allowing

for consideration of the proposed land use at the subject site. While Part 742 contains rules,

the TACO process set forth therein is not independent. It must be used in conjunction with

remediation programs, most specifically those found at Part 740: Site Remediation Program;

Part 732: Underground Storage Tank rules; and the closure requirements under the Resource

Conservation and Recovery program at Parts 724 and 725.

A Tier 1 analysis requires the remediation applicant to compare contamination levels of

constituents of concern at the remediation site to predetermined objectives. The predetermined

remediation objectives are set forth in look-up tables in the rules in Appendix B. If any

contaminant of concern at a remediation site are found to exceed the predetermined levels, the

remediation applicant is required to remediate the contamination until the corrective action

objectives are achieved, or alternatively, to develop site-specific remediation objectives using a

Tier 2 or Tier 3 analysis.

A Tier 2 analysis uses equations set forth in the rules to develop alternate remediation

objectives for constituents of concern, using site-specific information. The equations used to

develop site-specific remediation objectives are from the Soil Screening Level (SSL) and the

Risk Based Corrective Action (RBCA) approaches, and they are listed in the rules in Appendix

C. If any contaminants of concern are found to exceed the remediation objectives developed

using the Tier 2 equations, the remediation applicant is required to remediate the

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contamination until the objectives are achieved, remediate to the Tier 1 objectives, or to

develop alternate objectives using a Tier 3 analysis.

A Tier 3 analysis allows a remediation applicant to develop remediation objectives

using alternative parameters not found in Tier 1 or Tier 2. It allows a remediation applicant to

use modified parameters, provided the remediation applicant provides justification for the

modification, and the technical and mathematical basis for the modification. Additionally, a

Tier 3 analysis allows a remediation applicant to use alternative models if certain information

is provided, including a licensed copy of the model, the mathematical and technical basis for

the model, and a demonstration that the model was correctly applied. If any contaminants of

concern are found to exceed the remediation objectives developed using the Tier 3 analysis, the

remediation applicant is required to remediate the contamination until the objectives are

achieved.

EVOLUTION OF THE MIXTURE RULE

The statutory premise for the mixture rules is found at Section 58.5(c) of the Act. 415

ILCS 58.5(c) (1996). Section 58.5(c) provides in pertinent part that the regulations

establishing remediation objectives shall address “the presence of multiple substances of

concern and multiple exposure pathways.” 415 ILCS 5/58.5(c) (1996). Initially, the Agency

only proposed a mixture rule under Tier 2. However, over the course of Dockets A and B in

this rulemaking, the Agency has changed its position several times concerning the type of

mixture rule needed at each of the three tiers. The Agency’s various proposals and testimony

are summarized below, as are the mixture rules adopted today for first notice. The evidence

on the record supporting the rules proposed today and the Board’s consideration of the same

are set forth in greater detail in this opinion under “Analysis of Proposal and Testimony.”

Under the authority of Section 58.5(c) of the Act, the Agency, in its original proposal

under Docket A, recommended that TACO take into account mixtures of similar-acting

chemicals with regard to soil remediation objectives. In this regard, the Agency also stated

that the USEPA cautioned the users of the SSL to account for cumulative effects of chemicals

that affect the same target organ. Docket A Exh. 5 at 28-29. In Errata Sheet Number 3 filed

near the close of Docket A, the Agency recommended that this rulemaking also address

mixtures of similar-acting chemicals in groundwater, citing 35 Ill. Adm. Code 620 as its

authority. Specifically, Section 620.615 provides that mixtures of similar-acting chemicals in

groundwater should be addressed when determining remediation objectives. Finally, during

Docket B, the Agency recommended revising the Tier 1 mixture rule to be applicable only to

similar-acting carcinogenic chemicals, and only to those similar-acting carcinogenic chemicals

that exceed their Tier 1 remediation objectives, and for those whose remediation objectives

that are set at risk levels higher than 1 in 1,000,000.

The following chart best summarizes the changes in the mixture rule subsequent to the

Agency’s original proposal. Summaries about the Agency’s reasons for its various positions

concerning the need for mixture rules, responses by other participants and the Board’s actions

are included in the following, more detailed discussion. To understand the chart below and the

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more detailed discussion, two questions must be asked and answered initially: (1) is the rule

being applied to determine groundwater or soil remediation objectives; and (2) are the similar-

acting contaminants of concern carcinogenic or noncarcinogenic chemicals?

Mixture Rule

Agency Errata

Board Docket

Agency Docket

B

Board 1

Notice Docket

Tier 1

Groundwater

both

noncarc

carc

both

Soil

----

----

----

----

Tier 2

Groundwater

both

noncarc

both

both

Soil

noncarc

noncarc

noncarc

noncarc

Tier 3

Groundwater

----

----

both

both

Soil

----

----

both

both

noncarc = noncarcinogenic chemicals

carc = carcinogenic chemicals

both = noncarcinogenic and carcinogenic chemicals

ANALYSIS OF PROPOSAL AND TESTIMONY

The Board’s inquiry now considers whether it should adopt the changes proposed by

the Agency to the mixture rule adopted in Docket A or otherwise modify the mixture rule

applicable under TACO. First, the Board addresses general issues of concern under one or

more of the three tiers. Second, we address whether a mixture rule should be adopted for soil

remediation objectives under Tier 1. Third, the Board examines whether a mixture rule should

be adopted for carcinogenic contaminants of concern as well as noncarcinogenic contaminants

of concern for groundwater under both Tiers 1 and 2. Finally, the Board addresses whether a

mixture rule should be adopted under Tier 3.

Dr. Thomas C. Hornshaw provided testimony in support of the Agency’s proposed

amendments to the mixture rule. In addition to his prefiled testimony, Dr. Hornshaw and

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other Agency personnel provided testimony in response to questions asked of them at hearing.

Two public hearings were held: the first on May 21, 1997 in Chicago, and the second on May

29, 1997 in Springfield. Participants other than the Agency also testified or asked questions at

hearings, including, Harry Walton on behalf of the Site Remediation Advisory Committee

(SRAC), the Illinois Environmental Regulatory Group (IERG) and Illinois Power Company;

David Reiser of Ross & Hardies on behalf of the Illinois Petroleum Council and the Illinois

Steel Group; and Whitney Wagner Rosen on behalf of the IERG.

Two exhibits and three public comments were filed in the Docket B proceeding. The

first exhibit offered at hearing was the prefiled testimony of Dr. Thomas C. Hornshaw on

behalf of the Agency; the second exhibit which was prepared by the Board, was a draft of the

amendatory language proposed by Dr. Hornshaw in his testimony. The first public comment

was the Agency’s Posthearing Comments filed on June 13, 1997 (PC 1); the second was the

Posthearing Comments of SRAC filed on June 13, 1997 (PC 2). The third public comment

(PC 3) was filed on July 8, 1997 when the SRAC filed its Supplemental Posthearing

Comments. Due to the late submission of this filing, the Board will postpone consideration of

this public comment until it proceeds to second notice.

General Issues

Definition of Similar-Acting Chemical

In response to public testimony, the Board today proposes to adopt at Section 742.200 a

definition of similar-acting chemicals. There was no such definition in the final rules adopted

under Docket A because the term was defined within Sections 742.710 and 742.805(c). As

part of its revised proposal under Docket B, the Agency proposed to strike that relevant

language. Therefore, at hearing Mr. Rieser questioned Dr. Hornshaw on whether language

may be added to 742.805(c) to provide a definition of “similar-acting chemicals”. Tr.1 at 37-

38. Specifically, Mr. Reiser proposed replacing “similar-acting chemicals” with “mixtures of

chemicals which affect the same target organ/organ system or similar mode of action.” Tr.1

at 38. Dr. Hornshaw agreed with Mr. Reiser that his suggestion was an appropriate

clarification. Tr.1 at 38. In turn, the Board questioned Dr. Hornshaw whether a similar

definition of “similar-acting chemicals” could be inserted at Section 742.200 entitled

“Definitions.” Tr.2 at 21-21. Dr. Hornshaw agreed with the Board’s suggestion. Tr.2 at 21.

While the Board agrees with Mr. Reiser that a definition of “similar-acting chemicals”

should be included in Part 742, it finds that this definition is most appropriately placed at

Section 742.200 to provide overall clarity to the remediation applicant. Accordingly, the

Board proposes that, at Section 742.200, the following definition of “similar-acting chemicals”

be inserted:

“Similar-Acting Chemicals” are chemical substances that have toxic or harmful

physiological effect on the same specific organ or organ system. (See Appendix

A.Tables E and F, for a list of similar-acting chemicals with noncarcinogenic and

carcinogenic effects.)

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This definition parallels the description of similar-acting chemicals found at 35 Ill. Adm. Code

620.615. Since the mixture rule originates from that rule, the Board finds that its description

of similar-acting chemicals is most appropriate for defining the same under TACO.

Appendix A.Table H: Carcinogens with Groundwater Remediation Objectives in Excess of a

1 in 1,000,000 Cancer Risk Concentration

In its prefiled testimony under Docket B, the Agency proposed that a new Table H be

added to Part 742 in Appendix A. Exh. 1 at 10. Table H lists those chemicals whose Tier 1

Class I groundwater remediation objectives exceed the 1 in 1,000,000 cancer risk

concentrations. The Agency proposes that Table H identifies those similar-acting carcinogenic

chemicals which must undergo either the Tier 2 or Tier 3 procedure for evaluating the mixture

effect of similar-acting chemicals. For example, if more than one similar-acting carcinogenic

chemical listed in Table H is detected at a site, whether the remediation applicant is proceeding

under Tier 1, 2, or 3, then the remediation applicant must apply the methodologies in either

Tier 2 or 3 to determine their additive effect and adjust the remediation objective as necessary.

The Board agrees that the new Appendix A.Table H will assist the remediation applicant to

more readily determine whether the similar-acting carcinogenic chemicals detected are subject

to the mixture rule found under Tier 2 or 3.

Satisfaction of Section 620.615 of the Board’s Groundwater Regulations

Initially, the Agency assumed that the requirements of Section 35 Ill. Adm. Code

620.615 concerning mixtures of similar-acting chemicals would govern the development of site

remediation objectives at any site where such chemicals were detected. However, during the

course of Docket A, the Agency applied that rule for similar-acting chemicals detected in Class

I groundwater at a particular site then being studied for remediation, and its applicability was

challenged. The Agency had applied the groundwater rule because the Act requires that

TACO address multiple chemicals of concern, as does Section 620.615. Tr.1 at 16-17.

Section 620.615 requires that the Agency determine “the need for additional health advice

appropriate to site-specific conditions” when similar-acting chemicals are detected. The

Agency is required to use the procedures for evaluating the mixture of such substances

specified in Appendices A, B and C of Part 620. 35 Ill. Adm. Code 620.

To resolve any ambiguity, the Agency realized that Section 620.615 must be “cross-

referenced” or an alternative procedure to Section 620.615 must be provided within the TACO

regulations. The Agency maintains that if Section 620.615 is not cross-referenced in Part 742,

“the door remains open for future debate” over the appropriate remediation objectives when

similar-acting chemicals are detected in Class I groundwater. Tr.1 at 17. Moreover, the

Agency foresees the possibility of a remediation applicant expecting to receive a no further

remediation determination from the Agency by virtue of achieving all Class I groundwater

objectives, only to be informed that further remediation would be necessary because the

requirements of Section 620.615 have not been met. Tr.1 at 17-18. Finally, the Agency

suggests that, because Part 742 is silent about the requirements for mixtures of similar-acting

chemicals in Class I groundwater, a No Further Remediation Letter might be issued under the

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Site Remediation Program and subsequently challenged on the grounds that the requirements of

Section 620.615 were not satisfied. Tr.1 at 17-18. With these concerns in mind, the Agency

proposed that language be added cross-referencing the requirements of Part 620.615 in Tiers 1

and 2 of Part 742.

Specifically, the Agency proposes that the Board adopt the following language at

Section 742.805(b)(3) for Tier 1 and at Section 742.805(c) for Tier 2.

The requirements of 35 Ill. Adm. Code 620.615 regarding mixtures of similar-acting

chemicals shall be considered met for Class I groundwater at the point of human

exposure if the following requirements are achieved. Exh. 2.

The language proposed by the Agency means that the mixture rule mandated by the Act

and Section 620.615 of the Board’s rules would be considered satisfied if the remediation

objectives set forth under Tier 1 and those developed under Tier 2 are met. We note that the

Agency would not require a mixture rule for similar-acting noncarcinogenic chemicals under

Tier 1; satisfaction of the applicable remediation objective listed thereunder would be

sufficient. Exh. 2. As proposed, the specific requirements of the TACO mixture rule (versus

that under Section 620.615) are found under Tier 2 at Section 742.805 and under Tier 3 at

Section 742.915(h).

We have examined whether satisfaction of the remediation objectives under the TACO

rules should be deemed satisfaction of the evaluations required under the Section 620.615. We

agree with the Agency that either a cross-reference to the mixture rule at Section 620.615 or

an alternative mixture is necessary to assure the remediation applicant that compliance with the

TACO rules is considered comparable to the groundwater protection afforded by Section

620.615. However, we do not agree with the Agency that the Act and Section 620.615 can be

deemed satisfied unless the cumulative affect of similar-acting chemicals is evaluated in all

cases. Clearly the two would not be comparable if similar-acting noncarcinogenic chemicals in

groundwater are not subject to the mixture rule under Tier 1. Our discussion on that point

supra, is found under Tier 1 Groundwater.

To insure that each of the three tiers provides a mixture rule comparable to that found

at Section 620.615, the cumulative effect of similar-acting chemicals, both similar-acting

carcinogenic and noncarcinogenic chemicals, must be evaluated under each tier. Since the

rules proposed today for first notice require just that, we will adopt the cross-reference

requested by the Agency. Accordingly, the language proposed for first notice at both Tiers 1

and 2 will provide that the evaluation required under Section.620.615 to be considered

satisfied, subject to two exceptions. First, under all three tiers if more than one similar-acting

noncarcinogenic chemical is detected at the site, the mixture rule set out at Section 742.805(c)

or that developed under Tier 3 must be applied. Second, if a similar-acting carcinogenic

chemical listed on Appendix A.Table H is detected (whether or not this carcinogen is listed on

Table H) plus any other similar- acting carcinogen is detected at the site, the mixture rule at

Section 742.805(d) or that developed under Tier 3 must be applied. Compliance with one of

the applicable mixture rule under TACO serves to satisfy the statutory requirement that

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multiple substances be addressed, and the mixture rule serves as an appropriate alternative

procedure to that set out at Section 620.615. Therefore, the remediation applicant knows what

procedures to undertake to obtain a no further remediation determination. Furthermore, this

approach eliminates any challenge on the grounds that the requirements of the Act or the

Board’s groundwater regulations concerning multiple similar-acting chemicals were not met.

Finally, we note that we have modified the Agency’s proposed language. Those

principle modifications include substituting (1) “the requirements of Section 620.615” with the

term “evaluations” and (2) “shall be considered met” with the term “satisfied”. The Board

believes these substitutions more accurately reflect the appropriate cross-reference and

relationship between the two rules.

Tier 1

In Docket A on June 5, 1997, we adopted as final some of the language proposed by

the Agency at Section 742.505(b). The mixture rule adopted was applicable only to the

groundwater remediation objectives under Tier 1, but for similar-acting noncarcinogenic

chemicals only and regardless of whether the Tier 1 remediation objectives were exceeded.

The Board found that a mixture rule for similar-acting noncarcinogenic chemicals necessary to

protect human health. The example relied upon by the Board was a hypothetical site where

BETX are present at levels equal to their respective Tier 1 remediation objectives. The

acronym BETX stands for the carcinogen, benzene, and the similar-acting noncarcinogenic

chemicals, ethylbenzene and toluene, which both affect the kidney and liver.

4

The cumulative

effect of these two similar-acting noncarcinogenic chemicals could result in a hazard quotient

greater than one, and therefore their presence in the groundwater could pose a risk to human

health. Tiered Approach to Corrective Action Objectives: 35 Ill. Adm. Code 742 (June 5,

1997) R97-12(A), slip. op. at 46-50. The adoption of a mixture rule applicable to this

scenario requires that the remediation objectives be corrected to levels where the hazard

quotient is less than or equal to one.

After meeting with some of the participants after the adoption of Docket A, the Agency

concluded that, for the protection of human health, the mixture rule need only apply to

similar-acting carcinogenic chemicals in the context of groundwater remediation objectives and

only when the applicable Tier 1 remediation objectives are exceeded or if the remediation

objective was based on a risk factor of greater than 1 in 1,000,000.

Based on the evidence presented to the Board by the Agency in Docket A and as

summarized below in this Docket B, the Board finds (1) that a mixture rule is not necessary

for either carcinogenic or noncarcinogenic chemicals when developing soil remediation

objectives under Tier 1 and (2) that a mixture rule is necessary for similar-acting carcinogenic

and noncarcinogenic chemicals when developing groundwater remediation objectives under

Tier 1.

4

The “X” in BETX stands for xylene, a chemical not part of this discussion.

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Soil

With regard to Tier 1 soil remediation objectives, Dr. Hornshaw testified that the

inherent protection built into the process of developing the Tier 1 soil remediation objectives,

for similar-acting carcinogenic and noncarcinogen, made consideration of the additivity of

effects of similar-acting chemicals unnecessary in Tier 1. Tr.1 at 14, 19. Because these levels

are premised upon the SSL, they are sufficiently conservative to obviate the need to evaluate

the cumulative effect of similar-acting chemicals on the same target organ. Therefore, the

remediation objectives set forth in Appendix A.Tables E and F are protective of human health

in the context of soil remediation objectives.

Groundwater

Dr. Hornshaw testified that, initially, the Agency assumed that the requirements of 35

Ill. Adm. Code 620.615 regarding mixtures of similar-acting chemicals would govern the

development of remediation objectives at a site. Tr.1 at 16. Therefore, the Agency and the

SRAC agreed that it was not necessary to address mixtures of similar-acting carcinogenic and

noncarcinogenic chemicals in groundwater in any tier. Tr.1 at 16. After some discussion,

however, the Agency decided that a mixture rule for similar-acting carcinogenic and

noncarcinogenic chemicals in Class I groundwater is necessary and appropriate because it is

required by 35 Ill. Adm. Code 620.615. Tr.1 at 17.

Regarding similar-acting chemicals in groundwater at Tier 1, the Agency believes that

the consideration of similar-acting chemicals is required by both Title XVII of the Act and 35

Ill. Adm. Code 620 of the Board’s regulations. Tr.1 at 21. Dr. Hornshaw further testified

that the Agency and the SRAC agreed that the original version of Part 742 was unclear

regarding the requirements for remediation objectives for similar-acting chemicals in

groundwater. Tr.1 at 20. Finally, the Agency reiterated its belief that Title XVII mandates

that the remediation objectives in Tier 1 consist only of look-up tables. PC 1 at 2.

The Agency maintains that, unlike the Tier 1 soil remediation objectives, there is not

necessarily the same degree of protection built into the groundwater remediation objectives.

Tr.1 at 21. In support of its argument, Dr. Hornshaw suggested that an additional layer of

protection is built into the soil remediation objectives, due to the assumptions made regarding

transport in soil. Tr.1 at 21-22. Whereas for the groundwater component of the groundwater

ingestion exposure route, Dr. Hornshaw argued that the only conservatisms built into

development of the remediation objectives are assumptions regarding the toxicity and the

actual intake of the chemical. Tr.1 at 21-22.

Further, Dr. Hornshaw maintained that, for certain similar-acting carcinogenic

chemicals whose Tier 1 groundwater remediation objective are based on the chemical’s

drinking water standard, the groundwater remediation objectives do not have the same degree

of conservatism as the corresponding soil remediation objectives. Tr.1 at 22. The Agency

explained that this difference is because USEPA considered factors other than risk when it

established the drinking water standards; factors such as natural occurrence, detection limits,

or risk/benefit analysis. Tr.1 at 22.

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Nevertheless, the Agency concluded that for the most part, “there is an appropriate

degree of conservatism in the Tier 1 groundwater remediation objectives such that

consideration of similar-acting carcinogenic and noncarcinogenic chemicals is not necessary in

Tier 1.” Tr.1 at 23-24. However, the Agency requested that the mixture rule include two

caveats. The Agency requests that the potential for cumulative effects of mixtures of some

similar-acting chemicals must be addressed in a Tier 2 evaluation (1) if any contaminant of

concern, (carcinogen or noncarcinogen), exceeds its respective Tier 1 groundwater remediation

objective, or (2) if a carcinogen whose Tier 1 groundwater objective is not based on a 1 in

1,000,000 cancer risk is detected in groundwater. Tr.1 at 24. Utilizing the look-up table in

the newly proposed Appendix A.Table H, the Agency maintains that the applicant can

determine with finality whether any chemicals at a site exceed their Tier 1 objectives. Tr.2 at

36-37.

The Board questioned whether the Agency’s proposed mixture rule for Tier 1

groundwater remediation objectives considers similar-acting noncarcinogenic chemicals. Tr.1

at 56. Dr. Hornshaw explained that if any chemical (carcinogen and noncarcinogen) exceeds

the Tier 1 remediation objectives, then that chemical, plus any other chemicals that affect the

same target organ, shall be elevated to a Tier 2 evaluation to confirm that the mixture effect is

addressed properly. Tr.1 at 56-57. In response to further Board questions regarding this

issue, Dr. Hornshaw explained that, a remediation applicant need not address cumulative

effects at the Tier 1 level unless a chemical exceeds its Tier 1 levels. Tr.1 at 57. If a

chemical exceeds its Tier 1 level and there are other chemicals that affect the same target

organ, then those chemicals must be remediated based upon Tier 2 methodologies. Tr.1 at 57.

At hearing in this docket, the Board asked the Agency about its position under Docket

A. The Board recalled that at the close of first notice in Docket A, the Agency had advocated

a mixture rule for both similar-acting carcinogenic and noncarcinogenic chemicals in Class I

groundwater despite the statutory distinction between the two. Section 58.5(d) of the Act

provides a range of acceptable risk levels for similar-acting carcinogenic chemicals; it does not

provide anything comparable for similar-acting noncarcinogenic chemicals. According to its

public comment at that time, the Agency advocated that the mixture rule be applicable to both

similar-acting carcinogenic and noncarcinogenic chemicals because “[t]he Agency has taken

the position that Part 742 should rely on the State’s groundwater standard as closely as

possible.” Docket A, PC 10 at 11; Tr.2 at 26. The Board further noted, using a hypothetical

situation, that it had identified two similar-acting noncarcinogenic contaminants of concern at

levels near their respective remediation objectives where the value of the cumulative weighted

average equation could result in a hazard quotient greater than one. Tr.2 at 27-28. A hazard

quotient, also referred to as a hazard index, is a ratio of the chemical level present at a site and

the acceptable level of each similar-acting chemical. Under the Board’s groundwater rules,

specifically those at Section 620.615, if the hazard index/quotient is greater than one, the

remediation objective must be corrected to levels where the hazard index/quotient is less than

or equal to one.

Next, the Board questioned Dr. Hornshaw why the Agency changed its policy and now

maintains that similar-acting noncarcinogenic chemicals in groundwater need not be addressed

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12

unless one of them exceeds the Tier 1 remediation. Dr. Hornshaw responded that, “we came

to the conclusion that there is enough conservatism built into the Tier 1 objective for the

noncarcinogens that...we don’t think that there is a concern for mixtures.” Tr.2 at 28. He

further stated, however, that if the applicant is performing a Tier 2 evaluation, some of the

conservatism is lost so that the Agency feels it is appropriate in that scenario to address

mixtures of similar-acting chemicals. Tr.2 at 28. In addition, Dr. Hornshaw testified that the

Agency drew upon language from 35 Ill. Adm. Code 620.615 which states that “if two or

more of the chemical substances are similar-acting then the Agency shall consider mixtures of

similar-acting substances.” Tr.2 at 28. Due to the “requirements” set forth in 35 Ill. Adm.

Code 620.615, Dr. Hornshaw explained that the Agency decided it is unnecessary to evaluate

mixtures of noncarcinogenic chemicals at Tier 1, but if an applicant is performing a Tier 2

remediation, mixtures of noncarcinogenic chemicals must be addressed. Tr.2 at 28-29.

Moreover the Board questioned whether the hazard quotient could exceed one at a site.

The Agency responded that the hazard quotient could exceed one if, for example, both

ethylbenzene and toluene are present at a site. PC 1 at 2; See Tr.2 at 33. These two

chemicals are likely to exist, the Agency maintains, at a UST site. PC 1 at 2. Moreover, Dr.

Hornshaw stated that the carcinogen, benzene, is also likely to be at a majority of the UST

sites, and it very likely will exceed the Tier 1 remediation objectives. PC 1 at 2; Tr.2 at 33.

Further, Dr. Hornshaw testified that “it is benzene that is going to drive most of the

cleanups.” PC 1 at 3; Tr.2 at 33.

Addressing its change in policy concerning the need for a mixture rule for similar-

acting noncarcinogenic chemicals under Tier 1, Gary King, Manager of the Division of

Remedial Management, testified that “although there is a possibility that for the

noncarcinogens you could exceed a hazard quotient of one, the Agency felt that following the

statutory mandates to have a look-up table that people could rely on was most critical.” PC 1

at 3; See Tr.2 at 37. Finally, he noted that, “one of the things we wanted to do was continue

to have a Tier 1 table that had integrity, so that if you met the Tier 1 numbers, you didn’t have

to jump to Tier 2 or Tier 3.” Tr.2 at 37.

The Agency claims that there is enough built-in protection in the groundwater

remediation objectives for it to conclude that the mixture rule need not apply under Tier 1.

The Agency has not identified the distinction between the tiers which renders the pre-

established remediation objectives under Tier 1 so conservative that the presence of similar-

acting chemicals in excess of the hazard quotient/index of one is protective of human health.

The Agency has only identified a policy change on its part as reason to support its position.

We believe that the mixture rule must apply in all cases if the remediation objectives under all

three tiers are to be equally protective.

At hearing, Harry Walton on behalf of the SRAC, the IERG and Illinois Power Company,

testified that one of the guiding tenets of this rulemaking was to create a look-up table to provide

finality in the remediation process. Tr.2 at 44. Mr. Walton further testified that there is a need to

evaluate those constituents for which the Tier 1 value exceeds the 1 in 1,000,000 cancer risk.

Tr.2 at 44. He argued that, in those situations, those constituents should be evaluated under a

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13

Tier 2 analysis. Tr.2 at 44. In doing so, the integrity of the look-up table is maintained. Tr.2 at

44. Mr. Walton asserted that maintaining the integrity of the look-up table is important because

the regulated community wants certainty in the remediation process. Tr.2 at 47.

Mr. Walton also testified that since Tier 1 is based on the groundwater standards, it

meets the intent of the groundwater protection standards. Tr.2 at 45. He explained that the 35

Ill. Adm. Code 620 numbers were generated in a general use strategy, while the 35 Ill. Adm.

Code 742 numbers are intended to be applied to remedial programs. Tr.2 at 45.

In response to a Board question, Mr. Walton hypothesized that a remediation applicant

could calculate a remediation objective less than the Tier 1 levels when doing a Tier 2

analysis, but he had not been able to identify such a scenario. Tr.2 at 48-49. Mr. Walton

suggested that, because the primary constituent of concern drives the remediation process, if

that objective is satisfied, then typically the other remediation objectives will be satisfied.

Tr.2 at 49. For example, in Mr. Walton’s experience, benzene drives most remediations

because it moves aggressively in the environment. He concluded that remediating benzene

would typically cause the other contaminants to be remediated. Tr.2 at 45 and 49.

We sympathize with the desire by the Agency and the participants for the simplicity of

“look-up tables” under Tier 1. However, the Agency recommends and the participants agree

that under Tier 1 more than a simple look-up table is necessary when determining groundwater

remediation objectives for similar-acting carcinogenic chemicals which exceed the high end of

the statutory risk range of 1 in 1,000,000 cancer risk. Likewise, the evidence does not support

a simple look-up table when the cumulative effect of similar-acting noncarcinogenic chemicals

in groundwater exceeds the hazard quotient/index of one. Furthermore, we believe that the

burden on a remediation applicant to determine the cumulative effect of similar-acting

noncarcinogenic chemicals and to correct the remediation objectives as necessary is not unduly

burdensome. The example most used by the participants is the presence of BETX at a site.

They agree that the cleanup at such a site will be driven by the carcinogen, benzene, and

testified that the similar-acting noncarcinogenic chemicals will be cleaned up to acceptable

levels coincidental to the benzene cleanup. In such a case, then the only additional burden on

the remediation applicant will be to perform the necessary calculations to determine the

cumulative effect and the corrected remediation objectives, and prove that the latter where

achieved as part of the benzene remediation.

Tier 2

Under Docket A, the adopted mixture rule is applicable only for similar-acting

noncarcinogenic chemicals in the context of

both

groundwater and soil remediation objectives.

The Board did not adopt a mixture rule for similar-acting carcinogenic chemicals because the

record did not support the same. Tiered Approach to Corrective Action Objectives: 35 Ill.

Adm. Code 742 (June 5, 1997), R97-12(A) slip. op. at 49-50.

The Agency’s position under Docket B is that a mixture rule for similar-acting

noncarcinogenic chemicals is still necessary for soil and groundwater remediation objectives,

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14

but the only mixture rule necessary for similar-acting carcinogenic chemicals is in the context

of groundwater remediation objectives. Based upon the evidence presented by the Agency, as

summarized below, we agree with the Agency. We note that because a mixture rule for

similar-acting noncarcinogenic chemicals only was adopted under Tier 2 on June 5, 1997, the

Board need only amend the existing Tier 2 rules to include a mixture rule at Section 742.810

for similar-acting carcinogenic chemicals in excess of the groundwater remediation values

determined under Tier 2.

Soil

As for mixtures of similar-acting chemicals in soil under Tier 1 or 2, Dr. Hornshaw

testified that it was only necessary to address mixture effects of similar-acting noncarcinogenic

chemicals because, for similar-acting carcinogenic chemicals, the language of Section 58.5(d)

of the Act specifically provides for the establishment of remediation objectives at an excess

lifetime cancer risk of between 1 in 10,000 and 1 in 1,000,000. Tr.1 at 15. Dr. Hornshaw

further explained that the Agency and the SRAC were in agreement that, “since the statute

provides for an acceptable cancer risk range and since even if there are 10 carcinogens present

at their respective 1 in 1,000,000 remediation objectives (an unusual event), the cumulative

cancer risk of 1 in 100,000 is still within an acceptable range.” Tr.1 at 15. On the other

hand, because the Act does not specify an acceptable risk range for similar-acting

noncarcinogenic chemicals, Dr. Hornshaw concluded that the additive effects of similar-acting

noncarcinogenic chemicals need to be considered and provided for in Tier 2. Tr.1 at 15, 19.

Groundwater

With regard to mixtures of similar-acting carcinogenic chemicals in groundwater under

Tier 2, the Agency maintains that there are similar-acting carcinogenic chemicals whose

groundwater objectives exceed the 1 in 1,000,000 cancer risk level, and which, if present in a

mixture with other similar-acting carcinogenic chemicals, could potentially result in a

cumulative cancer risk exceeding 1 in 10,000. Tr.1 at 24. The Agency argues that, given the

statutory and regulatory requirements to consider mixture effects in groundwater, the mixture

rule should be applied to Tier 2 mixtures of similar-acting carcinogenic chemicals. Tr.1 at 22-

23. Accordingly, the Agency concluded that only similar-acting carcinogenic chemicals whose

Tier 1 groundwater objectives exceed the 1 in 1,000,000 risk level and those similar-acting

carcinogenic chemicals whose Tier 1 groundwater remediation objectives are not based on a 1

in 1,000,000 risk level must be evaluated for mixture effects in Tier 2. Tr.1 at 24. Finally,

the Agency proposes that those similar-acting carcinogenic chemicals whose Tier 1

groundwater remediation objectives exceed the 1 in 1,000,000 risk level will be specifically

identified in a look-up table. Tr.1 at 24; See Exh. 1, Appendix A, Table H.

As for mixtures of similar-acting noncarcinogenic chemicals in groundwater, Dr.

Hornshaw testified that its was generally agreed by the Agency and the SRAC that

consideration of similar-acting noncarcinogenic chemicals in Tier 2 is required. Tr.1 at 20.

At hearing, Mr. Reiser questioned Dr. Hornshaw about how Section 742.805(d) is

supposed to work. Tr.1 at 40. Dr. Hornshaw responded that if a chemical detected at a site

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15

during the site investigation is on the newly proposed Appendix A.Table H, then that chemical

is a carcinogen whose Tier 1 remediation objective exceeds the 1 in 1,000,000 target cancer

risk. In that case, the additive effect of that chemical and all those chemicals detected at the

site which affect the same target organ must be considered in a Tier 2 evaluation. Tr.1 at 40.

Mr. Reiser also questioned whether such a chemical must exceed its Tier 1 level for the

mixture rule to apply. Tr.1 at 43. Dr. Hornshaw responded that such a chemical does not

have to exceed its Tier 1 level, rather it is sufficient that it exceeds its detection level for the

mixture rule to be applicable. Tr.1 at 43.

Finally, Mr. Reiser asked how cumulative risk is determined. Tr.1 at 43-44. Dr.

Hornshaw suggested that cumulative risk can be assessed by several methods. First, Dr.

Hornshaw explained, proposed Appendix A.Table H provides a list of chemicals with a greater

than 1 in 1,000,000 risk level. Tr.1 at 44. A second approach is to use the same kind of

approach in Section 742.805(c)(1) where the applicant would calculate a weighted average

using the concentration detected over an acceptable concentration, i.e., 1 in 10,000 risk level.

Tr.2 at 10. Third, a remediation applicant could pursue a more formal risk assessment and

actually calculate the risk of the entire mixture given exposure assumptions that are either

default in approach or developed as part of a Tier 3 risk assessment. Tr.1 at 44.

Tier 3

Under Docket B, the Agency has again requested the mixture rule apply to both soil

and groundwater remediation objectives for both similar-acting carcinogenic and

noncarcinogenic chemicals. Tr.1 at 19, 27. The Agency proposed the following language

towards that end:

Contaminants of concern which affect the same target organ, organ system or similar

mode of action shall be specifically addressed. At a minimum, the chemical subject to

this requirement are identified in Appendix A, Tables E and F.

In response to a Board Member’s question regarding how similar-acting chemicals will

be addressed in Tier 3, Dr. Hornshaw explained that there are guidance documents provided

by USEPA for conducting risk assessments at Superfund sites. Tr.1 at 60. These guidance

documents provide instructions with quantified results informing the responsible party how to

address mixtures of similar-acting carcinogenic and noncarcinogenic chemicals. Tr.1 at 60-61.

The instructions include an evaluation of exposure through all routes and a comparison against

acceptable exposures to determine whether the situation needs to be evaluated further. Tr.1 at

61.

The Board proposes for first notice the amendments requested under Tier 3 by the

Agency to insure that the cumulative effects of both carcinogenic and noncarcinogenic

chemicals are evaluated under the Tier 3 site-specific approach. That language is found at

Section 742.915(h), and the regulation previously located there is entirely relocated to

subparagraph (i) of the same section.

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16

In closing, the Board questions why the proposed language does not parallel more

closely that requested under Tiers 1 and 2. Most specifically, the Board believes that the

mixture rule under Tier 3 should (1) use the term “similar-acting chemical”; (2) provide

minimum requirements for specifically addressing the cumulative effects of similar-acting

chemicals, be they similar-acting carcinogenic or noncarcinogenic chemicals; and (3) that

compliance with those minimum requirements will be deemed protective of Class I

groundwater in terms of human health. The Board asks that the Agency and the participants

consider and comment on these suggested revisions.

CONCLUSION

The Board proposes for first notice a mixture rule for similar-acting chemicals in Class

I groundwater which spans uniformly all three tiers of TACO. The rule proposed is basically

that proposed by the Agency with one exception. That exception is that the Board proposes to

apply the mixture rule under Tier 1 to similar-acting noncarcinogenic chemicals detected in

groundwater at sites. The Agency ultimately proposed that the mixture rule under Tier 1 apply

only to similar-acting carcinogenic chemicals, but that it apply to both similar-acting

noncarcinogenic and carcinogenic chemicals under Tiers 2 and 3.

The Board concludes that a mixture rule for similar-acting noncarcinogenic chemicals

in groundwater is required under Tier 1, as well as under Tiers 2 and 3, because the

remediation objective for similar-acting noncarcinogenic chemicals in groundwater is premised

upon a hazard quotient of one. If that ratio is exceeded, the levels of the similar-acting

noncarcinogenic chemicals at the site exceed acceptable levels, whether or not the remediation

objective is exceeded. The Agency has provided no evidence to the contrary. Again, while

we sympathize with the participants’ desire for simple look-up tables for similar-acting

noncarcinogenic chemicals in groundwater under Tier 1, we find that the evidence instead

supports that protection of human health requires a mixture rule under all three tiers for

similar-acting noncarcinogenic chemicals in groundwater.

Finally, having proposed the mixture rule to be all-inclusive, the Board adopts the

cross-reference to Section 620.615 of the Board’s groundwater rules. Thus, the remediation

applicant and the public are assured that an evaluation of similar-acting chemicals provided

thereunder is also provided under TACO.

ORDER

The Board directs the Clerk to cause the filing of the following proposal for first notice in

the

Illinois Register

:

TITLE 35: ENVIRONMENTAL PROTECTION

SUBTITLE G: WASTE DISPOSAL

CHAPTER I: POLLUTION CONTROL BOARD

SUBCHAPTER f: RISK BASED CLEANUP OBJECTIVES

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17

PART 742

TIERED APPROACH TO CORRECTIVE ACTION OBJECTIVES

SUBPART A: INTRODUCTION

Section

742.100

Intent and Purpose

742.105

Applicability

742.110

Overview of Tiered Approach

742.115

Key Elements

742.120

Site Characterization

SUBPART B: GENERAL

Section

742.200

Definitions

742.205

Severability

742.210

Incorporations by Reference

742.215

Determination of Soil Attenuation Capacity

742.220

Determination of Soil Saturation Limit

742.225

Demonstration of Compliance with Remediation Objectives

742.230

Agency Review and Approval

SUBPART C: EXPOSURE ROUTE EVALUATIONS

Section

742.300

Exclusion of Exposure Route

742.305

Contaminant Source and Free Product Determination

742.310

Inhalation Exposure Route

742.315

Soil Ingestion Exposure Route

742.320

Groundwater Ingestion Exposure Route

SUBPART D: DETERMINING AREA BACKGROUND

Section

742.400

Area Background

742.405

Determination of Area Background for Soil

742.410

Determination of Area Background for Groundwater

742.415

Use of Area Background Concentrations

SUBPART E: TIER 1 EVALUATION

Section

742.500

Tier 1 Evaluation Overview

742.505

Tier 1 Soil and Groundwater Remediation Objectives

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18

742.510

Tier 1 Remediation Objectives

SUBPART F: TIER 2 GENERAL EVALUATION

Section

742.600

Tier 2 Evaluation Overview

742.605

Land Use

742.610

Chemical and Site Properties

SUBPART G: TIER 2 SOIL EVALUATION

Section

742.700

Tier 2 Soil Evaluation Overview

742.705

Parameters for Soil Remediation Objective Equations

742.710

SSL Soil Equations

742.715

RBCA Soil Equations

742.720

Chemicals with Cumulative Noncarcinogenic Effects

SUBPART H: TIER 2 GROUNDWATER EVALUATION

Section

742.800

Tier 2 Groundwater Evaluation Overview

742.805

Tier 2 Groundwater Remediation Objectives

742.810

Calculations to Predict Impacts from Remaining Groundwater Contamination

SUBPART I: TIER 3 EVALUATION

Section

742.900

Tier 3 Evaluation Overview

742.905

Modifications of Parameters

742.910

Alternative Models

742.915

Formal Risk Assessments

742.920

Impractical Remediation

742.925

Exposure Routes

742.930

Derivation of Toxicological Data

SUBPART J: INSTITUTIONAL CONTROLS

Section

742.1000

Institutional Controls

742.1005

No Further Remediation Letters

742.1010

Restrictive Covenants, Deed Restrictions and Negative Easements

742.1015

Ordinances

742.1020

Highway Authority Agreements

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19

SUBPART K: ENGINEERED BARRIERS

Section

742.1100

Engineered Barriers

742.1105

Engineered Barrier Requirements

APPENDIX A

General

ILLUSTRATION A

Developing Soil Remediation Objectives Under the Tiered

Approach

ILLUSTRATION B

Developing Groundwater Remediation Objectives Under the Tiered

Approach

Table A

Soil Saturation Limits (C

sat

) for Chemicals Whose Melting Point is Less

Than 30

0

C

Table B

Tolerance Factor (K)

Table C

Coefficients {A

N-I+1

} for W Test of Normality, for N=2(1)50

Table D

Percentage Points of the W Test for N=3(1)50

Table E

Similar-Acting Noncarcinogenic Chemicals with Noncarcinogenic Toxic

Effects on Specific Target Organs/Organ Systems or Similar Modes of

Action

Table F

Similar-Acting Carcinogenic Chemicals with Carcinogenic Toxic Effects on

Specific Target Organs/Organ Systems or Similar Modes of Action

Table G

Concentrations of Inorganic Chemicals in Background Soils

Table H Chemicals Whose Tier 1 Class I Groundwater Remediation Objective

Exceeds the 1 in 1,000,000 Cancer Risk Concentration

APPENDIX B

Tier 1 Tables and Illustrations

ILLUSTRATION A

Tier 1 Evaluation

Table A

Tier 1 Soil Remediation Objectives for Residential Properties

Table B

Tier 1 Soil Remediation Objectives for Industrial/Commercial Properties

Table C

pH Specific Soil Remediation Objectives for Inorganics and Ionizing

Organics for the Soil Component of the Groundwater Ingestion Route

(Class I Groundwater)

Table D

pH Specific Soil Remediation Objectives for Inorganics and Ionizing

Organics for the Soil Component of the Groundwater Ingestion Route

(Class II Groundwater)

Table E

Tier 1 Groundwater Remediation Objectives for the Groundwater

Component of the Groundwater Ingestion Route

Table F

Values Used to Calculate the Tier 1 Soil Remediation Objectives for the

Soil Component of the Groundwater Ingestion Route

APPENDIX C

Tier 2 Tables and Illustrations

ILLUSTRATION A

Tier 2 Evaluation for Soil

ILLUSTRATION B

Tier 2 Evaluation for Groundwater

ILLUSTRATION C

US Department of Agriculture Soil Texture Classification

Table A

SSL Equations

Table B

SSL Parameters

Table C

RBCA Equations

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20

Table D

RBCA Parameters

Table E

Default Physical and Chemical Parameters

Table F

Methods for Determining Physical Soil Parameters

Table G

Error Function (erf)

Table H

Q/C Values by Source Area

Table I

K

[oc]

Values for Ionizing Organics as a Function of pH (cm(3)/g or L/kg)

Table J

Values to be Substituted for k

s

When Evaluating Inorganics as a Function

of pH (cm(3)[water]/g[soil])

Table K

Parameter Estimates for Calculating Water-Filled Soil Porosity (

θ

w

)

AUTHORITY: Implementing Sections 22.4, 22.12, Title XVI, and Title XVII and authorized by

Sections 27, 57.14, and 58.5 of the Environmental Protection Act [415 ILCS 5/22.4, 22.12, Title

XVI and Title VII] (see P.A. 88-496, effective September 13, 1993 and P.A. 89-0431, effective

December 15, 1995).

MAIN SOURCE: Adopted at 21 Ill. Reg. 7942, effective July 1, 1997, amended at 21 Ill. Reg.

__________________, effective __________________.

NOTE: Capitalization indicates statutory language.

Section 742.105

Applicability

a)

Any person, including a person required to perform an investigation pursuant to

the Illinois Environmental Protection Act (415 ILCS 5/1 et seq.) (Act), may elect

to proceed under this Part to the extent allowed by State or federal law and

regulations and the provisions of this Part. A person proceeding under this Part

may do so to the extent such actions are consistent with the requirements of the

program under which site remediation is being addressed.

b)

This Part is to be used in conjunction with the procedures and requirements

applicable to the following programs:

1)

Leaking Underground Storage Tanks (35 Ill. Adm. Code 731 and 732);

2)

Site Remediation Program (35 Ill. Adm. Code 740); and

3)

RCRA Part B Permits and Closure Plans (35 Ill. Adm. Code 724 and 725).

c)

The procedures in this Part may not be used if their use would delay response

action to address imminent and substantial threats to human health and the

environment. This Part may only be used after actions to address such threats

have been completed.

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21

d)

This Part may be used to develop remediation objectives to protect surface waters,

sediments or ecological concerns, when consistent with the regulations of other

programs, and as approved by the Agency.

e)

A no further remediation determination issued by the Agency prior to July 1, 1997

pursuant to Section 4(y) of the Act or one of the programs listed in subsection (b)

of this Section that approves completion of remedial action relative to a release

shall remain in effect in accordance with the terms of that determination.

f)

Site specific groundwater remediation objectives under this Part for contaminants

of concern may exceed the groundwater quality standards established pursuant to

the rules promulgated under the Illinois Groundwater Protection Act. (415 ILCS

55/1

et seq.

) as long as done in accordance with Sections 742.805(a) and

742.900(c)(9). (415 ILCS 5/58.5(d)(4)

SOURCE: Amended at 21 Ill. Reg. ______________ , effective __________________.

Section 742.200

Definitions

Except as stated in this Section, or unless a different meaning of a word or term is clear

from the context, the definition of words or terms in this Part shall be the same as that applied to

the same words or terms in the Act.

"Act" means the Illinois Environmental Protection Act (415 ILCS 5/1 et seq.).

"ADL" means Acceptable Detection Limit, which is the detectable concentration

of a substance which is equal to the lowest appropriate Practical Quantitation

Limit (PQL) as defined in this Section.

"Agency" means the Illinois Environmental Protection Agency.

"Agricultural Property" means any real property for which its present or post-

remediation use is for growing agricultural crops for food or feed either as

harvested crops, cover crops or as pasture. This definition includes, but is not

limited to, properties used for confinement or grazing of livestock or poultry and

for silviculture operations. Excluded from this definition are farm residences, farm

outbuildings and agrichemical facilities.

"Area Background" means CONCENTRATIONS OF REGULATED

SUBSTANCES THAT ARE CONSISTENTLY PRESENT IN THE

ENVIRONMENT IN THE VICINITY OF A SITE THAT ARE THE RESULT

OF NATURAL CONDITIONS OR HUMAN ACTIVITIES, AND NOT THE

RESULT SOLELY OF RELEASES AT THE SITE. (Section 58.2 of the Act)

"ASTM" means the American Society for Testing and Materials.

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22

"Board" means the Illinois Pollution Control Board.

"Cancer Risk" means a unitless probability of an individual developing cancer from

a defined exposure rate and frequency.

"Cap" means a barrier designed to prevent the infiltration of precipitation or other

surface water, or impede the ingestion or inhalation of contaminants.

"Carcinogen" means A CONTAMINANT THAT IS CLASSIFIED AS A

CATEGORY A1 OR A2 CARCINOGEN BY THE AMERICAN CONFERENCE

OF GOVERNMENTAL INDUSTRIAL HYGIENISTS; A CATEGORY 1 OR

2A/2B CARCINOGEN BY THE WORLD HEALTH ORGANIZATION'S

INTERNATIONAL AGENCY FOR RESEARCH ON CANCER; A "HUMAN

CARCINOGEN" OR "ANTICIPATED HUMAN CARCINOGEN" BY THE

UNITED STATES DEPARTMENT OF HEALTH AND HUMAN SERVICE

NATIONAL TOXICOLOGICAL PROGRAM; OR A CATEGORY A OR B1/B2

CARCINOGEN BY THE UNITED STATES ENVIRONMENTAL

PROTECTION AGENCY IN the INTEGRATED RISK INFORMATION

SYSTEM OR A FINAL RULE ISSUED IN A FEDERAL REGISTER NOTICE

BY THE USEPA. (Section 58.2 of the Act)

"Class I Groundwater" means groundwater that meets the Class I: Potable

Resource Groundwater criteria set forth in 35 Illinois Administrative Code 620.

"Class II Groundwater" means groundwater that meets the Class II: General

Resource Groundwater criteria set forth in 35 Illinois Administrative Code 620.

"Conservation Property" means any real property for which present or post-

remediation use is primarily for wildlife habitat.

"Construction Worker" means a person engaged on a temporary basis to perform

work involving invasive construction activities including, but not limited to,

personnel performing demolition, earth-moving, building, and routine and

emergency utility installation or repair activities.

"Contaminant of Concern" or "Regulated Substance of Concern" means ANY

CONTAMINANT THAT IS EXPECTED TO BE PRESENT AT THE SITE

BASED UPON PAST AND CURRENT LAND USES AND ASSOCIATED

RELEASES THAT ARE KNOWN TO THE person conducting a remediation

BASED UPON REASONABLE INQUIRY. (Section 58.2 of the Act)

"Engineered Barrier" means a barrier designed or verified using engineering

practices that limits exposure to or controls migration of the contaminants of

concern.

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23

"Exposure Route" means the transport mechanism by which a contaminant of

concern reaches a receptor.

"Free Product" means a contaminant that is present as a non-aqueous phase liquid

for chemicals whose melting point is less than 30

o

C (e.g., liquid not dissolved in

water).

"GROUNDWATER" MEANS UNDERGROUND WATER WHICH OCCURS

WITHIN THE SATURATED ZONE AND GEOLOGIC MATERIALS WHERE

THE FLUID PRESSURE IN THE PORE SPACE IS EQUAL TO OR GREATER

THAN ATMOSPHERIC PRESSURE. (Section 3.64 of the Act)

"Groundwater Quality Standards" means the standards for groundwater as set

forth in 35 Illinois Administrative Code 620.

"Hazard Quotient" means the ratio of a single substance exposure level during a

specified time period to a reference dose for that substance derived from a similar

exposure period.

“Highway” means ANY PUBLIC WAY FOR VEHICULAR TRAVEL WHICH

HAS BEEN LAID OUT IN PURSUANCE OF ANY LAW OF THIS STATE, OR

OF THE TERRITORY OF ILLINOIS, OR WHICH HAS BEEN ESTABLISHED

BY DEDICATION, OR USED BY THE PUBLIC AS A HIGHWAY FOR 15

YEARS, OR WHICH HAS BEEN OR MAY BE LAID OUT AND CONNECT A

SUBDIVISION OR PLATTED LAND WITH A PUBLIC HIGHWAY AND

WHICH HAS BEEN DEDICATED FOR THE USE OF THE OWNERS OF THE

LAND INCLUDED IN THE SUBDIVISION OR PLATTED LAND WHERE

THERE HAS BEEN AN ACCEPTANCE AND USE UNDER SUCH

DEDICATION BY SUCH OWNERS, AND WHICH HAS NOT BEEN

VACATED IN PURSUANCE OF LAW. THE TERM “HIGHWAY”

INCLUDES RIGHTS OF WAY, BRIDGES, DRAINAGE STRUCTURES,

SIGNS, GUARD RAILS, PROTECTIVE STRUCTURES AND ALL OTHER

STRUCTURES AND APPURTENANCES NECESSARY OR CONVENIENT

FOR VEHICULAR TRAFFIC. A HIGHWAY IN A RURAL AREA MAY BE

CALLED A “ROAD”, WHILE A HIGHWAY IN A MUNICIPAL AREA MAY

BE CALLED A “STREET”. (Illinois Highway Code [605 ILCS 5/2-202])

“Highway Authority” means THE DEPARTMENT of Transportation WITH

RESPECT TO A STATE HIGHWAY; THE COUNTY BOARD WITH

RESPECT TO A COUNTY HIGHWAY OR A COUNTY UNIT DISTRICT

ROAD IF A DISCRETIONARY FUNCTION IS INVOLVED AND THE

COUNTY SUPERINTENDENT OF HIGHWAYS IF A MINISTERIAL

FUNCTION IS INVOLVED; THE HIGHWAY COMMISSIONER WITH

RESPECT TO A TOWNSHIP OR DISTRICT ROAD NOT IN A COUNTY

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24

UNIT ROAD DISTRICT; OR THE CORPORATE AUTHORITIES OF A

MUNICIPALITY WITH RESPECT TO A MUNICIPAL STREET. (Illinois

Highway Code [605 ILCS 5/2-213])

"Human Exposure Pathway" means a physical condition which may allow for a

risk to human health based on the presence of all of the following: contaminants of

concern; an exposure route; and a receptor activity at the point of exposure that

could result in contaminant of concern intake.

"Industrial/Commercial Property" means any real property that does not meet the

definition of residential property, conservation property or agricultural property.

"Infiltration" means the amount of water entering into the ground as a result of

precipitation.

"Institutional Control" means a legal mechanism for imposing a restriction on land

use, as described in Subpart J.

"Man-Made Pathways" means CONSTRUCTED physical conditions THAT MAY

ALLOW FOR THE TRANSPORT OF REGULATED SUBSTANCES

INCLUDING, BUT NOT LIMITED TO, SEWERS, UTILITY LINES, UTILITY

VAULTS, BUILDING FOUNDATIONS, BASEMENTS, CRAWL SPACES,

DRAINAGE DITCHES, OR PREVIOUSLY EXCAVATED AND FILLED

AREAS. (Section 58.2 of the Act)

"Natural Pathways" means NATURAL physical conditions that may allow FOR

THE TRANSPORT OF REGULATED SUBSTANCES INCLUDING, BUT

NOT LIMITED TO, SOIL, GROUNDWATER, SAND SEAMS AND LENSES,

AND GRAVEL SEAMS AND LENSES. (Section 58.2 of the Act)

"Negative Easement" means a right of the owner of the dominant or benefitted

estate or property to restrict the property rights of the owner of the servient or

burdened estate or property.

"Person" means an INDIVIDUAL, TRUST, FIRM, JOINT STOCK COMPANY,

JOINT VENTURE, CONSORTIUM, COMMERCIAL ENTITY,

CORPORATION (INCLUDING A GOVERNMENT CORPORATION),

PARTNERSHIP, ASSOCIATION, STATE, MUNICIPALITY, COMMISSION,

POLITICAL SUBDIVISION OF A STATE, OR ANY INTERSTATE BODY

INCLUDING THE UNITED STATES GOVERNMENT AND EACH

DEPARTMENT, AGENCY, AND INSTRUMENTALITY OF THE UNITED

STATES. (Section 58.2 of the Act)

"Point of Human Exposure" means the point(s) at which human exposure to a

contaminant of concern may reasonably be expected to occur. The point of human

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25

exposure is at the source, unless an institutional control limiting human exposure

for the applicable exposure route has been or will be in place, in which case the

point of human exposure will be the boundary of the institutional control. Point of

human exposure may be at a different location than the point of compliance.

"PQL" means Practical Quantitation Limit or estimated quantitation limit, which is

the lowest concentration that can be reliably measured within specified limits of

precision and accuracy for a specific laboratory analytical method during routine

laboratory operating conditions in accordance with "Test Methods for Evaluating

Solid Wastes, Physical/Chemical Methods", EPA Publication No. SW-846,

incorporated by reference in Section 742.210. When applied to filtered water

samples, PQL includes the method detection limit or estimated detection limit in

accordance with the applicable method revision in: "Methods for the

Determination of Organic Compounds in Drinking Water", Supplement II", EPA

Publication No. EPA/600/4-88/039; "Methods for the Determination of Organic

Compounds in Drinking Water, Supplement III", EPA Publication No.

EPA/600/R-95/131, all of which are incorporated by reference in Section 742.210.

"RBCA" means Risk Based Corrective Action as defined in ASTM E-1739-95, as

incorporated by reference in Section 742.210.

"RCRA" means the Resource Conservation and Recovery Act of 1976. (42

U.S.C. 6921)

"Reference Concentration (RfC)" means an estimate of a daily exposure, in units of

milligrams of chemical per cubic meter of air (mg/m

3

), to the human population

(including sensitive subgroups) that is likely to be without appreciable risk of

deleterious effects during a portion of a lifetime (up to approximately seven years,

subchronic) or for a lifetime (chronic).

"Reference Dose (RfD)" means an estimate of a daily exposure, in units of

milligrams of chemical per kilogram of body weight per day (mg/kg/d), to the

human population (including sensitive subgroups) that is likely to be without

appreciable risk of deleterious effects during a portion of a lifetime (up to

approximately seven years, subchronic) or for a lifetime (chronic).

"Regulated Substance" means ANY HAZARDOUS SUBSTANCE AS DEFINED

UNDER SECTION 101(14) OF THE COMPREHENSIVE ENVIRONMENTAL

RESPONSE, COMPENSATION, AND LIABILITY ACT OF 1980 (P.L. 96-510)

AND PETROLEUM PRODUCTS INCLUDING CRUDE OIL OR ANY

FRACTION THEREOF, NATURAL GAS, NATURAL GAS LIQUIDS,

LIQUEFIED NATURAL GAS, OR SYNTHETIC GAS USABLE FOR FUEL

(OR MIXTURES OF NATURAL GAS AND SUCH SYNTHETIC GAS).

(Section 58.2 of the Act)

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26

"Residential Property" MEANS ANY REAL PROPERTY THAT IS USED FOR

HABITATION BY INDIVIDUALS, OR where children have the opportunity for

exposure to contaminants through soil ingestion or inhalation at educational

facilities, health care facilities, child care facilities or outdoor recreational areas.

"Restrictive Covenant or Deed Restriction" means a provision placed in a deed

limiting the use of the property and prohibiting certain uses. (Black's Law

Dictionary, 5th Edition)

“Right of Way” means THE LAND, OR INTEREST THEREIN, ACQUIRED

FOR OR DEVOTED TO A HIGHWAY. (Illinois Highway Code [605 ILCS 5/2-

217])

“Similar-Acting Chemicals” are chemical substances that have toxic or harmful

effect on the same specific organ or organ system (see Appendix A.Tables E and F

for a list of similar-acting chemicals with noncarcinogenic and carcinogenic

effects).

"Site" means ANY SINGLE LOCATION, PLACE, TRACT OF LAND OR

PARCEL OF PROPERTY, OR PORTION THEREOF, INCLUDING

CONTIGUOUS PROPERTY SEPARATED BY A PUBLIC RIGHT-OF-WAY.

(Section 58.2 of the Act)

"Slurry Wall" means a man-made barrier made of geologic material which is

constructed to prevent or impede the movement of contamination into a certain

area.

"Soil Saturation Limit (C

sat

)" means the contaminant concentration at which soil

pore air and pore water are saturated with the chemical and the adsorptive limits of

the soil particles have been reached.

"Solubility" means a chemical specific maximum amount of solute that can dissolve

in a specific amount of solvent (groundwater) at a specific temperature.

“SPLP” means Synthetic Precipitation Leaching Procedure (Method 1312) as

published in “Test Methods for Evaluating Solid Waste, Physical/Chemical

Methods”, USEPA Publication No. SW-846, as incorporated by reference in

Section 742.210.

"SSL" means Soil Screening Levels as defined in USEPA's Soil Screening

Guidance: User's Guide and Technical Background Document, as incorporated by

reference in Section 742.210.

"Stratigraphic Unit" means a site-specific geologic unit of native deposited material

and/or bedrock of varying thickness (e.g., sand, gravel, silt, clay, bedrock, etc.). A

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27

change in stratigraphic unit is recognized by a clearly distinct contrast in geologic

material or a change in physical features within a zone of gradation. For the

purposes of this Part, a change in stratigraphic unit is identified by one or a

combination of differences in physical features such as texture, cementation, fabric,

composition, density, and/or permeability of the native material and/or bedrock.

"TCLP" means Toxicity Characteristic Leaching Procedure (Method 1311) as

published in "Test Methods for Evaluating Solid Waste, Physical/Chemical

Methods," USEPA Publication No. SW-846, as incorporated by reference in

Section 742.210.

"Total Petroleum Hydrocarbon (TPH)" means the additive total of all petroleum

hydrocarbons found in an analytical sample.

"Volatile Organic Compounds (VOCs)" means organic chemical analytes identified

as volatiles as published in "Test Methods for Evaluating Solid Waste,

Physical/Chemical Methods,"USEPA Publication No. SW-846 (incorporated by

reference in Section 742.210), method numbers 8010, 8011, 8015, 8020, 8021,

8030, 8031, 8240, 8260, 8315, and 8316. For analytes not listed in any category

in those methods, those analytes which have a boiling point less than 200

0

C and a

vapor pressure greater than 0.1 Torr (mm Hg) at 20

0

C.

SOURCE: Amended at 21 Ill. Reg. ______________ , effective __________________.

Section 742.505

Tier 1 Soil and Groundwater Remediation Objectives

a)

Soil

1)

Inhalation Exposure Route

A)

The Tier 1 soil remediation objectives for this exposure route based

upon residential property use are listed in Appendix B, Table A.

B)

The Tier 1 soil remediation objectives for this exposure route based

upon industrial/commercial property use are listed in Appendix B,

Table B. Soil remediation objective determinations relying on this

table require use of institutional controls in accordance with

Subpart J.

2)

Ingestion Exposure Route

A)

The Tier 1 soil remediation objectives for this exposure route based

upon residential property use are listed in Appendix B, Table A.

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28

B)

The Tier 1 soil remediation objectives for this exposure route based

upon industrial/commercial property use are listed in Appendix B,

Table B. Soil remediation objective determinations relying on this

table require use of institutional controls in accordance with

Subpart J.

3)

Soil Component of the Groundwater Ingestion Route

A)

The Tier 1 soil remediation objectives for this exposure route based

upon residential property use are listed in Appendix B, Table A.

B)

The Tier 1 soil remediation objectives for this exposure route based

upon industrial/commercial property use are listed in Appendix B,

Table B.

C)

The pH-dependent Tier 1 soil remediation objectives for identified

ionizable organics or inorganics for the soil component of the

groundwater ingestion exposure route (based on the total amount

of contaminants present in the soil sample results and groundwater

classification) are provided in Appendix B, Tables C and D.

D)

Values used to calculate the Tier 1 soil remediation objectives for

this exposure route are listed in Appendix B, Table F.

4)

Evaluation of the dermal contact with soil exposure route is not required

under Tier 1.

b)

Groundwater

1)

The Tier 1 groundwater remediation objectives for the groundwater

component of the groundwater ingestion route are listed in Appendix B,

Table E.

2)

The Tier 1 groundwater remediation objectives for this exposure route are

given for Class I and Class II groundwaters, respectively.

3)

The evaluation of 35 Ill. Adm. Code 620.615 regarding mixtures of similar-

acting chemicals shall be considered satisfied for Class I groundwater at the

point of human exposure if: The Class I groundwater remediation

objectives set forth in Appendix B, Table E shall be corrected for

cumulative effect of mixtures of similar-acting noncarcinogenic chemicals

in accordance with the methodoligies set forth in either subsection (A) or

(B), if more than one chemical listed in Appendix A, Table E is detected at

---

29

a site and if such chemicals affect the same target organ (i.e., has the same

critical effect as defined by the RfD)

A)

No more than one similar-acting noncarcinogenic chemical as listed

in Appendix A, Table E is detected in the groundwater at the site;

and Calculate the weighted average using the following equations:

W

ave =

x

CUO

x

CUO

x

CUO

x

CUO

x

x

x

a

x

a

1

2

3

1

2

3

+

+

+

+

K

where:

W

ave

= Weighted Average

x

1

through x

a

= Concentration of each individual contaminant at the

location of concern. Note that, depending on the

target organ/mode of action, the actual number of

contaminants will range from 2 to 14.

CUOx

a

= A Tier 1 remediation objective must be developed

for each x

a

.

ii) If the value of the weighted average calculated in

accordance with the equations above is less than or equal to

1.0, then the remediation objectives are met for those

chemicals.

iii) If the value of the weighted average calculated in

accordance with the equations above is greater than 1.0,

then additional remediation must be carried out until the

level of contaminants remaining in the remediated area have

a weighted average calculated in accordance with the

equation above less than or equal to one;

B)

No carcinogenic contaminant of concern as listed in Appendix A,

Table H is detected in any groundwater sample associated with the

site, using analytical procedures capable of achieving either the 1 in

1,000,000 cancer risk concentration or the ADL, whichever is

greater. Divide each individual chemical's remediation objective by

the number of chemicals in that specific target organ group that

were detected at the site. Each of the contaminant concentrations

at the site is then compared to the remediation objectives that have

been adjusted to account for this potential additivity

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30

4)

If the conditions of subsection (b)(3) are not met, the Class I groundwater

remediation objectives set forth in Appendix B, Table E shall be corrected

for the cumulative effect of mixtures of similar-acting chemicals using the

following methodologies:

A) For noncarcinogenic chemicals, the methodologies set forth at

Section 742.805(c) or Section 742.915(h) shall be used; and

B) For carcinogenic chemicals, the methodologies set forth at Section

742.805(d) or Section 742.915(h) shall be used.

SOURCE: Amended at 21 Ill. Reg. ______________ , effective __________________.

Section 742.805

Tier 2 Groundwater Remediation Objectives

a)

To develop a groundwater remediation objective under this Section that exceeds

the applicable Tier 1 groundwater remediation objective, a person may request

approval from the Agency if the person has performed the following:

1)

Identified the horizontal and vertical extent of groundwater for which the

Tier 2 groundwater remediation objective is sought;

2)

Taken corrective action, to the maximum extent practicable to remove any

free product;

3)

Using Equation R26 in accordance with Section 742.810, demonstrated

that the concentration of any contaminant of concern in groundwater will

meet:

A)

The applicable Tier 1 groundwater remediation objective at the

point of human exposure; or

B)

For any contaminant of concern for which there is no Tier 1

groundwater remediation objective, the Health Advisory

concentration determined according to the procedures specified in

35 Ill. Adm. Code 620, Subpart F at the point of human exposure.

A person may request the Agency to provide these concentrations

or may propose these concentrations under Subpart I;

4)

Using Equation R26 in accordance with Section 742.810, demonstrated

that the concentration of any contaminant of concern in groundwater

within the minimum or designated maximum setback zone of an existing

potable water supply well will meet the applicable Tier 1 groundwater

remediation objective or if there is no Tier 1 groundwater remediation

objective, the Health Advisory concentration;

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31

5)

Using Equation R26 in accordance with Section 742.810, demonstrated

that the concentration of any contaminant of concern in groundwater

discharging into a surface water will meet the applicable water quality

standard under 35 Ill. Adm. Code 302;

6)

Demonstrated that the source of the release is not located within the

minimum or designated maximum setback zone or within a regulated

recharge area of an existing potable water supply well; and

7)

If the selected corrective action includes an engineered barrier as set forth

in Subpart K to minimize migration of contaminant of concern from the soil

to the groundwater, demonstrated that the engineered barrier will remain in

place for post-remediation land use through an institutional control as set

forth in Subpart J.

b)

A groundwater remediation objective that exceeds the water solubility of that

chemical (refer to Appendix C, Table E for solubility values) is not allowed.

c) The contaminants of concern for which a Tier 1 remediation objective has been

developed shall be included in any mixture of similar-acting chemicals under

consideration in Tier 2. The evaluation of 35 Ill. Adm. Code 620.615 regarding

mixtures of similar-acting chemicals shall be considered satisfied for Class I

groundwater at the point of human exposure if either of the following requirements

are achieved:

1) Calculate the weighted average using the following equations:

W

ave =

x

CUO

x

CUO

x

CUO

x

CUO

x

x

x

a

x

a

1

2

3

1

2

3

+

+

+

+

K

where:

W

ave

= Weighted Average

x

1

through x

a

= Concentration of each individual contaminant at the

location of concern. Note that, depending on the

target organ, the actual number of contaminants will

range from 2 to 14.

CUOx

a

= A Tier 1 or Tier 2 remediation objective must be

developed for each x

a

.

If the value of the weighted average calculated in

accordance with the equations above is less than or equal to

---

32

1.0, then the remediation objectives are met for those

chemicals.

If the value of the weighted average calculated in

accordance with the equations above is greater than 1.0,

then additional remediation must be carried out until the

level of contaminants remaining in the remediated area have

a weighted average calculated in accordance with the

equation above less than or equal to one; or

2) Divide each individual chemical’s remediation objective by the number of

chemicals in that specific target organ group that were detected at the site.

Each of the contaminant concentrations at the site is then compared to the

remediation objectives that have been adjusted to account for this potential

addivity.

d) The evaluation of 35 Ill. Adm. Code 620.615 regarding mixtures of similar-acting

chemicals are considered satisfied if the cumulative risk from any contaminant(s) of

concern listed in Appendix A, Table H, plus any other contaminant(s) of concern

detected in groundwater and listed in Appendix A, Table F as affecting the same

target organ/organ system as the contaminant(s) of concern detected from

Appendix A, Table H, does not exceed 1 in 10,000.

SOURCE: Amended at 21 Ill. Reg. ______________ , effective __________________.

Section 742.915

Formal Risk Assessments

A comprehensive site-specific risk assessment shall demonstrate that contaminants of concern at a

site do not pose a significant risk to any human receptor. All site-specific risk assessments shall

be submitted to the Agency for review and approval. A submittal under this Section shall address

the following factors:

a)

Whether the risk assessment procedure used is nationally recognized and accepted

including, but not limited to, those procedures incorporated by reference in Section

742.210;

b)

Whether the site-specific data reflect actual site conditions;

c)

The adequacy of the investigation of present and post-remediation exposure routes

and risks to receptors identified at the site;

d)

The appropriateness of the sampling and analysis;

e)

The adequacy and appropriateness of toxicity information;

---

33

f)

The extent of contamination; and

g)

Whether the calculations were accurately performed;.

h)

Similar-acting chemicals shall be specifically addressed. At a minimum, the

chemicals subject to this requirement are identified in Appendix A, Tables E and F

and; Proposals seeking to modify the target risk consistent with Section

742.900(d) shall address the following factors:

1) the presence of sensitive populations;

2_ the number of receptors potentially impacted;

3) the duration of risk at the differing target levels; and

4) the characteristic of the chemicals of concern.

i) Proposals seeking to modify the target risk consistent with Section 742.900(d)

shall address the following factors:

1) the presence of sensitive populations;

2) the number of receptors potentially impacted;

3) the duration of risk at the differing target levels; and

4) the characteristic of the chemicals of concern.

SOURCE: Amended at 21 Ill. Reg. ______________ , effective __________________.

Section 742.APPENDIX A:

General

Section 742.TABLE E:

Similar-Acting Noncarcinogenic Chemicals with Noncarcinogenic

Toxic Effects on Specific Target Organs/Organ Systems or

Similar Modes of Action

Kidney

Acetone

Cadmium (Ingestion only)

Chlorobenzene

Dalapon

1,1-Dichloroethane

Di-n-octyl phthalate

Endosulfan

Ethylbenzene

Fluoranthene

Nitrobenzene

Pyrene

Toluene

2,4,5-Trichlorophenol

Vinyl acetate

Liver

Acenaphthene

Acetone

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34

Butylbenzyl phthalate

1,1-Dichloroethylene

Chlorobenzene

Di-n-octyl phthalate

Endrin

Ethylbenzene

Fluoranthene

Nitrobenzene

Picloram

Styrene

2,4,5-TP (Silvex)

Toluene

2,4,5-Trichlorophenol

Central Nervous System

Butanol

Cyanide (amenable)

2,4-Dimethylphenol

Endrin

Manganese

2-Methylphenol

Mercury

Styrene

Xylenes

Circulatory System

Antimony

Barium

2,4-D

cis-1,2-Dichloroethylene

Nitrobenzene

trans-1,2-Dichloroethylene

2,4-Dimethylphenol

Fluoranthene

Fluorene

Styrene

Zinc

Gastrointestinal System

Endothall

Hexachlorocyclopentadiene

Methyl bromide

Reproductive System

Barium

Boron

Carbon disulfide

2-Chlorophenol

1,2 Dibromo-3-Chloropropane (Inhalation

only)

Dinoseb

Methoxychlor

Phenol

Cholinesterase Inhibition

Aldicarb

Carbofuran

---

ILLINOIS REGISTER

POLLUTION CONTROL BOARD

NOTICE OF ADOPTED RULES

Decreased Body Weight Gains

and Circulatory System Effects

Atrazine

Simazine

Adrenal Gland

Nitrobenzene

1,2,4-Trichlorobenzene

Respiratory System

1,2-Dichloropropane

Hexachlorocyclopentadiene

Methyl bromide

Vinyl acetate

Immune System

2,4-Dichlorophenol

p-Chloroaniline

SOURCE: Amended at 21 Ill. Reg. ______________ , effective __________________.

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36

Section 742.APPENDIX A: General

Section 742.TABLE F:

Similar-Acting Carcinogenic Chemicals With Carcinogenic Toxic

Effects on Specific Target Organs/Organ Systems or Similar

Modes of Action

Kidney

Bromodichloromethane

Chloroform

1,2-Dibromo-3-chloropropane

2,4-Dinitrotoluene

2,6-Dinitrotoluene

Hexachlorobenzene

Liver

Aldrin

Bis(2-chloroethyl)ether

Bis(2-ethylhexyl)phthalate

Carbazole

Carbon tetrachloride

Chlordane

Chloroform

DDD

DDE

DDT

1,2-Dibromo-3-chloropropane

1,2-Dibromoethane

3,3'-Dichlorobenzidine

1,2-Dichloroethane

1,3-Dichloropropane (Ingestion only)

1,3-Dichloropropylene

Dieldrin

2,4-Dinitrotoluene

2,6-Dinitrotoluene

Heptachlor

Heptachlor epoxide

Hexachlorobenzene

alpha-HCH

gamma-HCH (Lindane)

Methylene chloride

N-Nitrosodiphenylamine

N-Nitrosodi-n-propylamine

Pentachlorophenol

Tetrachloroethylene

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37

Trichloroethylene

2,4,6-Trichlorophenol

Toxaphene

Vinyl chloride

Circulatory System

Benzene

2,4,6-Trichlorophenol

Gastrointestinal System

Benzo(a)anthracene

Benzo(b)fluoranthene

Benzo(k)fluoranthene

Benzo(a)pyrene

Chrysene

Dibenzo(a,h)anthracene

Indeno(1,2,3-c,d)pyrene

Bromodichloromethane

Bromoform

1,2-Dibromo-3-chloropropane

1,2-Dibromoethane

1,3-Dichloropropylene

Lung

Arsenic

Beryllium (Inhalation only)

Cadmium (Inhalation only)

Chromium, hexavalent (Inhalation only)

1,3-Dichloropropylene

Methylene chloride

N-Nitrosodi-n-propylamine

Vinyl chloride

Nasal Cavity

1,2-Dibromo-3-chloropropane

(Inhalation only)

1,2-Dibromoethane (Inhalation only)

N-Nitrosodi-n-propylamine

Bladder

3,3'-Dichlorobenzidine

1,3-Dichloropropylene

N-Nitrosodiphenylamine

SOURCE: Amended at 21 Ill. Reg. ______________ , effective __________________.

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38

Section 742.APPENDIX A: General

TABLE H: Chemicals Whose Tier 1 Class I Groundwater Remediation Objective Exceeds

the 1 in 1,000,000 Cancer Risk Concentration.

Class I Groundwater 1 in 1,000,000 Cancer

Remediation Objective Risk Concentration ADL

Chemical (mg/l) (mg/l) (mg/l)

Aldrin 0.00004 0.000002 0.00004

Benzo(a)pyrene 0.0002 0.000005 0.00023

Bis(2-chloroethyl)ether 0.01 0.00003 0.01

Bis(2-ethylhexyl)phthalate 0.006 0.003 0.0027

Carbon Tetrachloride 0.005 0.0003 0.00003

Chlordane 0.002 0.00003 0.00014

Dibenzo(a,h)anthracene 0.0003 0.000005 0.0003

1,2-Dibromo-3-chloropropane 0.0002 0.00003 0.0002

1,2-Dibromoethane 0.00005 0.0000004 0.00005

3,3'-Dichlorobenzidine 0.02 0.00008 0.02

1,2-Dichloroethane 0.005 0.0004 0.00003

Dieldrin 0.00002 0.000002 0.00002

Heptachlor 0.0004 0.000008 0.00003

Heptachlor epoxide 0.0002 0.000004 0.00032

Hexachlorobenzene 0.00006 0.00002 0.00006

alpha

-HCH 0.00003 0.000006 0.00003

Tetrachloroethylene 0.005 0.0007 0.00001

Toxaphene 0.003 0.00003 0.00086

Vinyl Chloride 0.002 0.000015 0.00006

Ionizable Organics

N

-Nitrosodiphenylamine 0.01 0.007 0.01

N-

Nitrosodi-n-propylamine 0.01 0.000005 0.01

Pentachlorophenol 0.001 0.0003 0.001

2,4,6-Trichlorophenol 0.0064 0.003 0.0064

Inorganics

Arsenic 0.05 0.00002 0.001

Beryllium 0.004 0.0000083 0.004

SOURCE: Adopted at 21 Ill. Reg. ______________ , effective __________________.

IT IS SO ORDERED.

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39

I, Dorothy M. Gunn, Clerk of the Illinois Pollution Control Board, hereby certify that

the above opinion and order was adopted on the10th day of July 1997, by a vote of 6-0.

Dorothy M. Gunn, Clerk

Illinois Pollution Control Board