Section 620.250  Groundwater Management Zone

a)         Within any class of groundwater, a groundwater management zone (GMZ) may be established as a three-dimensional region containing groundwater being managed to mitigate impairment caused by the release of one or more contaminants that is subject to a corrective action process approved by the Agency.

b)         Before a GMZ may be established, the owner or operator of a site at which there has been a release of one or more contaminants to groundwater must submit to the Agency a GMZ application.  The application must contain the information required by Section 620.Appendix D, Parts I, II, and III, as well as any other information requested in writing by the Agency that is relevant to its review under subsection (c). 

1)         If the GMZ would extend off-site, the GMZ application must include each off-site property owner's written permission to the establishment of the GMZ on its property.  If effectively implementing the off-site portion of the GMZ requires accessing an off-site property, the GMZ application must also include the off-site property owner's written permission for that access.  If the applicable written permission or permissions from an off-site property owner are not obtained – whether permission to establish the GMZ off-site, access the off-site property, or both – the GMZ will not include that off-site property.

2)         Nothing in this subsection (b) precludes the owner or operator from including additional information in its GMZ application. 

3)         Nothing in this subsection (b) requires that a GMZ application be in the form specified in Section 620.Appendix D, Parts I, II, and III. 

c)         The Agency must review each GMZ application submitted under subsection (b) and issue a written determination approving or rejecting the GMZ. 

1)         In determining whether to approve a GMZ, the Agency must consider the substantive information provided in support of the GMZ, the technical sufficiency of the GMZ, the likelihood that the GMZ will protect public health and the environment, and the likelihood that the GMZ's corrective action process will, in a timely manner, result in compliance with the applicable standards specified in Section 620.410, 620.420, 620.430, or 620.440 or otherwise minimize exceedances to restore beneficial use as appropriate for the class or classes of groundwater.  If the Agency rejects a GMZ, the Agency must, in its written determination, specify the reasons for the rejection.

2)         A GMZ is established when the Agency issues a written determination approving the GMZ, including its corrective action process.  Once a GMZ is established and before the corrective action is complete, the Agency may, as new information warrants and subject to the standards of subsection (c)(1), issue written determinations amending any part of the GMZ, including its size, the contaminants that are subject to it, and its corrective action process, as provided in this subsection (c)(2).  A GMZ is amended when the Agency issues a written determination amending the GMZ.  If the Agency rejects a submittal of the site owner or operator to amend the GMZ under subsection (c)(2)(i) or (c)(2)(ii), the Agency must do so in a written determination that specifies the reasons for the rejection.

i)          The Agency may issue a written determination directing that the site owner or operator submit to the Agency a written proposal to amend the GMZ, consistent with subsection (b).  The Agency's determination must identify the amendment to be proposed and specify the reasons why the amendment is necessary.  If the owner or operator fails to submit a proposal or the Agency rejects the proposal, the Agency may terminate the GMZ under subsection (f) either on its own initiative or at the written request of the owner or operator.

ii)         If it wishes to have the Agency amend the GMZ, the site owner or operator must submit to the Agency a written proposal to amend the GMZ, consistent with subsection (b).  If the Agency rejects the proposal, the Agency may terminate the GMZ under subsection (f) either on its own initiative or at the written request of the owner or operator.

d)         When it completes the corrective action under subsection (c)(2), the site owner or operator must submit to the Agency a written demonstration that complies with subsection (d)(1) or (d)(2) and contains the information required by the completion certification specified in Section 620.Appendix D, Part IV.  The Agency must review this demonstration and issue a written determination approving or rejecting the demonstration.  Nothing in this subsection (d) requires the owner or operator to make the demonstration using any specific type of documentation or precludes the owner or operator from including additional information in the demonstration.

1)         The owner or operator must demonstrate that it has completed the corrective action under subsection (c)(2) and the applicable standards of Subpart D, as specified in Section 620.450(a)(4)(A), have been attained in groundwater within the GMZ.  If the Agency approves this demonstration, the Agency must issue a written determination to that effect in which the Agency terminates the GMZ.  The termination takes effect when the Agency issues this determination.  If the Agency rejects this demonstration, the Agency must, in its written determination, specify the reasons for the rejection, which may include the Agency's basis for amending the GMZ to require additional corrective action under subsection (c)(2).

2)         The owner or operator must demonstrate that it has completed the corrective action under subsection (c)(2) and concentrations of released chemical constituents, as specified in Section 620.450(a)(4)(B), remain in groundwater within the GMZ.  The owner or operator must also demonstrate compliance with Section 620.450(a)(4)(B)(i) and (ii), as well as the on-going adequacy of controls, management, or both, as applicable, to maintain compliance with Section 620.450(a)(4)(B)(i) and (ii).  If the Agency approves this demonstration, the Agency must issue a written determination to that effect in which the Agency states that the GMZ remains in effect.  If the Agency rejects this demonstration, the Agency must, in its written determination, specify the reasons for the rejection, which may include the Agency's basis for amending the GMZ to require additional corrective action under subsection (c)(2).

e)         Within five years after the Agency issues a written determination approving a demonstration under subsection (d)(2), the site owner or operator must submit a report to the Agency demonstrating the on-going adequacy of controls, management, or both, as applicable, to maintain compliance with Section 620.450(a)(4)(B)(i) and (ii).  The Agency must review the report and issue a written determination approving or rejecting the demonstration. 

1)         The submittal of these reports by the owner or operator and the corresponding issuance of these written determinations by the Agency must occur at least every five years while the GMZ remains in effect.  If the Agency rejects a demonstration, the Agency must, in its written determination, specify the reasons for the rejection, which may include the Agency's basis for amending the GMZ to require additional controls or management under this subsection (e).

2)         Any amendment to controls or management under this subsection (e) is subject to the amendment provisions of subsection (c)(2), except that the standard for the Agency’s determination is whether the controls or management, as amended, would be adequate to maintain compliance with Section 620.450(a)(4)(B)(i) and (ii)

f)         Without limiting any other legal authority of the Agency to terminate a GMZ, the Agency may issue a written determination terminating a GMZ based on any of the grounds specified in this subsection (f).  The determination must specify the grounds for terminating the GMZ.  The termination takes effect when the Agency issues this determination.  The Agency may terminate a GMZ if:

1)         The site owner or operator fails to perform or comply with the schedule for any part of the GMZ, including its corrective action under subsection (c)(2) or its controls or management under subsection (d)(2) or (e);

2)         The Agency rejects a proposal to amend the GMZ under subsection (c)(2) or a demonstration under subsection (d) or (e);

3)         The site owner or operator commits fraud or misrepresentation in any submittal under subsection (b), (c)(2), (d), or (e);

4)         The site owner or operator submits to the Agency a written request to terminate the GMZ under subsection (c)(2); or

5)         The Agency, after issuing a written determination approving a demonstration under subsection (d)(2), determines that

i)          The applicable standards specified in Section 620.410, 620.420, 620.430, or 620.440 have been attained in groundwater within the GMZ; or

ii)         Additional corrective action is necessary because controls and management are no longer adequate to maintain compliance with Section 620.450(a)(4)(B)(i) and (ii).

g)         Upon GMZ termination under subsection (f), the groundwater within the three-dimensional region formerly encompassed by the GMZ becomes both designated as one of the four classes of groundwater specified in Section 620.201(a) and subject to the standards for the applicable class of groundwater specified in Section 620.410, 620.420, 620.430, or 620.440.

h)         Regardless of subsections (a) through (c), a "groundwater management zone", as defined in 35 Ill. Adm. Code 740.120, may be established under 35 Ill. Adm. Code 740.530 for sites in the Site Remediation Program (35 Ill. Adm. Code 740).  A GMZ established under 35 Ill. Adm. Code 740.530 remains in effect until any condition of 35 Ill. Adm. Code 740.530(c) is met.

i)          While a GMZ established under 35 Ill. Adm. Code 740.530 is in effect, the otherwise applicable standards of  Subpart D of this Part do not apply to the "contaminants of concern", as defined in 35 Ill. Adm. Code 740.120, for which groundwater remediation objectives have been approved under 35 Ill. Adm. Code 740.

j)          Regardless of subsection (d), that subsection's submittal and review requirements concerning the demonstration when corrective action is complete do not apply to a GMZ under 35 Ill. Adm. Code 740.530.  Regardless of subsection (e), that subsection's submittal and review requirements concerning the on-going adequacy of controls and management do not apply to groundwater within a three-dimensional region formerly encompassed by a GMZ established under 35 Ill. Adm. Code 740.530 while a No Further Remediation Letter issued under 35 Ill. Adm. Code 740 is in effect.

k)         The Agency must develop and maintain a list of all GMZs that have not been terminated.  The list must identify the location of each GMZ. On its website (https://epa.illinois.gov), the Agency must post the list and, at least annually, update it. In addition, at least annually, the Agency must submit the list to the Board for publication in the Environmental Register.

l)          In groundwater regulated under 35 Ill. Adm. Code 845, a GMZ is not available to address any exceedance of a groundwater protection standard specified in 35 Ill. Adm. Code 845.600(a) or (b) (see 35 Ill. Adm. Code 845.600(c)).

(Source:  Amended at 49 Ill. Reg. 4488, effective March 28, 2025)