Presentation_Actionitem2_IMACs_Nov2024_Shelton

Request Approval to Proceed to the EMC with a Recommendation to Initiate Rulemaking to Establish Groundwater Quality Standards for Bentazon, Boscalid, Fluometuron, and Metolachlor in Place of the Established IMACs
November 2024 Groundwater & Waste Management Committee
Bridget Shelton
Division of Water Resources, Classifications and Standards/Rules Review Branch
Interim Maximum Allowable Concentrations
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•When a groundwater standard has not been established under the
rule for a substance, that substance is not permitted in
concentrations above the practical quantitation limit (PQL)
•Any person may request the Director to modify the above
requirement by establishing an Interim Maximum Allowable
Concentration (IMAC)
•Any person request the DWR Director update or remove an
existing IMAC
•DWR Director has 180 calendar days to establish, update,
or remove an IMAC
15A NCAC 02L .0202 (c)
Guidelines for IMAC Establishment
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•The requestor must submit:
•Relevant toxicological and epidemiological data,
•Study results, and
•Calculations necessary to establish an IMAC in accordance with
Paragraphs (d) and (e) in 02L .0202.
•DWR evaluates the request to determine whether the
information is in accordance with Paragraphs (d) and (e)
•DWR reviews the information and calculates the health-based
protective level(s) for the chemical of concern
15A NCAC 02L .0202 (c)
•Groundwater standard and/or IMAC are established as the least
of the following:
1.Systemic/non-cancer threshold concentration
2.Concentration which corresponds to an incremental lifetime cancer
risk of 1x 10-6
3.Taste threshold limit value
4.Odor threshold limit value
5.Maximum contaminant level
6.National secondary drinking water standard
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Health-Based Levels
15A NCAC 02L .0202 (d)
•The following references shall be used in order of preference:
1.EPA Integrated Risk Information System (IRIS)
2.EPA Drinking Water Health Advisories
3.Other EPA health risk assessment data
4.Other relevant, published health risk assessment data and
scientifically valid peer-reviewed published toxicological data
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15A NCAC 02L .0202 (e)
References Used to Calculate
IMAC Decision
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•DWR Director may establish, update or remove IMAC if they find
the action:
•Will not degrade the quality of groundwaters,
•Will not likely cause or contribute to pollution of waters of the state, and
•Will be protective of public health
•DWR provides public notice and opportunity for comment at least
30 days prior to final action
•DWR provides notice to EMC within 30 days of final action
15A NCAC 02L .0202 (c)
•Within 12 months of establishing an IMAC, the DWR Director shall
make a recommendation to the EMC whether:
•A new groundwater standard in place of the IMAC should be established
•The IMAC should expire
•After the DWR Director’s recommendation, the EMC shall decide
whether to initiate rulemaking
•If the EMC initiates rulemaking, then the IMAC remains in effect until the
standard is adopted or the EMC declines to adopt a new standard
•If the EMC declines to initiate rulemaking, the IMAC expires
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IMACs Replaced by GW Standard or Expire
15A NCAC 02L .0202 (c)(6)
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IMAC Request:
Bentazon, Boscalid, Fluometuron, and Metolachlor
•DWR received a request on August 28, 2023 from ELM Site
Solutions, Inc.
•Establish IMACs in groundwater for Bentazon, Boscalid, Fluometuron,
and Metolachlor
•For an Inactive Hazardous Site project at a formerly operated BASF
Agricultural Test Farm in Holly Springs
•DWR public noticed the Director’s intent to establish these four
IMACs on November 22, 2023
•No comments were received
•The four IMACs were established by the DWR Director on
January 18, 2024
Information about the Four Established IMACs
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•Bentazon
•Herbicide
•IMAC: 200 µg/L
•Based on noncancer threshold concentration
•U.S. EPA Integrated Risk Information System
(IRIS) Assessment
•Boscalid
•Fungicide
•IMAC: 2,000 µg/L
•Based on noncancer threshold concentration
•U.S. EPA Office of Chemical Safety and
Pollution Prevention
The data, calculations, and supporting information for the establishment for these IMACs are available online:
https://www.deq.nc.gov/groundwater-imacs
•Fluometuron
•Herbicide
•IMAC: 90 µg/L
•Based on noncancer threshold concentration
•U.S. EPA Integrated Risk Information System
(IRIS) Assessment
•Metolachlor
•Herbicide
•IMAC: 700 µg/L
•Based on noncancer threshold concentration
•U.S. EPA Office of Water Health Advisory
Director’s Recommendation
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The DWR Director recommends that the
EMC establish groundwater quality
standards for bentazon, boscalid,
fluometuron, and metolachlor in place of
the IMACs during the next groundwater
standards triennial review.
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Action Item Request
The Division of Water Resources requests that the
GWWMC approve to proceed to the EMC with the
recommendation to initiate rulemaking to establish
groundwater quality standards for bentazon,
boscalid, fluometuron, and metolachlor in place of
the established IMACs.
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Thank you
Bridget Shelton
Groundwater Quality Standards Coordinator
Water Planning Section
Division of Water Resources
[e-mail]
[phone]
DWR, Classifications and Standards Branch:
https://deq.nc.gov/about/divisions/water-resources/planning/classification-standards