Ariz. Admin. Code § R18-13-1005 - Groundwater Monitoring and Corrective Action

A. 40 CFR 257.90 through 40 CFR 257.98, revised as of December 14, 2020 (and no future editions) are incorporated by reference, modified by the following subsections, and on file with ADEQ, with the exception of 40 CFR 257.90(g), "Suspension of groundwater monitoring requirements".

B. 40 CFR 257.94(a) is amended as follows: "(a) The owner or operator of a CCR unit must conduct detection monitoring at all groundwater monitoring wells consistent with this section. At a minimum, a detection monitoring program must include groundwater monitoring for all constituents listed in appendix III to this part. The Director may require monitoring for constituents or pollutants not listed in appendix III based on information that non-CCR waste has been placed in a CCR unit. The owner or operator may propose to the Director that monitoring for non-CCR constituents be based on the facility's most recent aquifer protection permit. Requirements for non-CCR constituents at existing and new CCR units, including alert levels, discharge limitations, compliance schedules, corrective actions and temporary cessation or plans shall be no more stringent than required to satisfy the requirements of A.R.S. Title 49, Chapter 2, Article 3, and 18 A.A.C. 9, Articles 1 and 2."

C. 40 CFR 257.94(e)(2) is amended as follows: "(2) The owner or operator may demonstrate that a source other than the CCR unit caused the statistically significant increase over background levels for a constituent or that the statistically significant increase resulted from error in sampling, analysis, statistical evaluation, or natural variation in groundwater quality. An owner or operator that is investigating whether to submit an alternative source demonstration under this section, shall notify the Director in writing within seven days of that decision. The owner or operator shall complete the written demonstration within 90 days of determining that there is a statistically significant increase over background levels to include obtaining a certification from a qualified professional engineer verifying the accuracy of the information in the report, and submit the demonstration and certification to the Director for approval. If the owner or operator completes a successful demonstration, as supported by a certification from a qualified professional engineer, within the 90-day period, the owner or operator may continue with a detection monitoring program, unless such demonstration is subsequently disapproved by the Director. If a successful demonstration was not completed within the 90-day period or if the Director disapproves the demonstration, the owner or operator shall initiate an assessment monitoring program as required under § 257.95. The owner or operator also shall include the demonstration in the annual groundwater monitoring and corrective action report required by § 257.90(e), in addition to the certification by a qualified professional engineer and Director approval."

D. 40 CFR 257.95(g)(3)(ii) is modified as follows: "(ii) Demonstrate that a source other than the CCR unit caused the contamination, or that the statistically significant increase resulted from error in sampling, analysis, statistical evaluation, or natural variation in groundwater quality. An owner or operator that is investigating whether to submit an alternative source demonstration under this section, shall notify the Director in writing within seven days of that decision. Any such demonstration shall be supported by a report that includes the factual or evidentiary basis for any conclusions, and shall be certified to be accurate by a qualified professional engineer. The demonstration, report and certification shall be submitted to the Director for approval. If a successful demonstration is made, the owner or operator shall continue monitoring in accordance with the assessment monitoring program pursuant to this section, and may return to detection monitoring if the constituents in Appendix III and Appendix IV of this part are at or below background as specified in paragraph (e) of this section, unless such demonstration is subsequently disapproved by the Director. The owner or operator must also include the demonstration in the annual groundwater monitoring and corrective action report required by § 257.90(e), in addition to the certification by a qualified professional engineer and Director approval.

E. 40 CFR 257.95(g)(4) is modified as follows: "(4) If a successful demonstration has not been made at the end of the 90-day period provided by paragraph (g)(3)(ii) of this section, or if the Director disapproves the demonstration, the owner or operator of the CCR unit shall initiate the assessment of corrective measures requirements under § 257.96."

F. 40 CFR 257.95(h) is amended as follows:

"(h) The owner or operator of the CCR unit shall establish a groundwater protection standard for each constituent in appendix IV to this part and each pollutant identified pursuant to subsection (B) detected in the groundwater. The groundwater protection standard shall be:

(1) For constituents for which an Aquifer Water Quality Standard has been established under 18 A.A.C. 11, Article 4, either the Aquifer Water Quality Standard for that constituent, or the maximum contaminant level (MCL) that has been established under §§ 141.62 and 141.66 of this title, whichever is more stringent. For constituents for which no Aquifer Water Quality Standard exists, and for which a maximum contaminant level (MCL) has been established under §§ 141.62 and 141.66 of this title, the MCL for that constituent.

(2) For constituents for which no Aquifer Water Quality Standard exists, and for which a maximum contaminant level (MCL) has not been established under 40 CFR 141.62 and 141.66, the background concentration established from wells in accordance with § 257.91.

(3) For constituents for which the background level is higher than the levels identified under paragraph (h)(1) of this section, the background concentration."

G. 40 CFR 257.97, titled "Selection of remedy", paragraph (a) is amended as follows: "(a) Based on the results of the corrective measures assessment conducted under § 257.96, the owner or operator must, as soon as feasible, select a remedy that, at a minimum, meets the standards listed in paragraph (b) of this section. This requirement applies in addition to, not in place of, any applicable standards under the Occupational Safety and Health Act. The owner or operator must prepare a semiannual report describing the progress in selecting and designing the remedy. Upon selection of a remedy, the owner or operator must prepare a final report describing the selected remedy and how it meets the standards specified in paragraph (b) of this section. The owner or operator shall obtain a certification, from a qualified professional engineer, which shall be submitted to the Director for approval, that the remedy selected meets the requirements of this section. The report has been completed when it is placed in the operating record as required by § 257.105(h)(12). The remedy selected shall be incorporated into the initial CCR facility permit, or added to it as a major permit modification."

H. 40 CFR 257.98, titled "Implementation of the corrective action program" paragraph (e) is amended as follows: "(e) Upon completion of the remedy, the owner or operator must prepare a notification stating that the remedy has been completed. The owner or operator must obtain a certification, from a qualified professional engineer, which shall be submitted to the Director for approval, attesting that the remedy has been completed in compliance with the requirements of paragraph (c) of this section. The notification has been completed when it is placed in the operating record as required by § 257.105(h)(13)."

Notes

Ariz. Admin. Code § R18-13-1005

New section made by final rulemaking at 31 A.A.R. 1363, effective 6/1/2025.