Presentation_InfoItem_GWStandards_Shelton

North Carolina 15A NCAC 02L .0202 Groundwater Quality Standards
Bridget Shelton
Division of Water Resources, Classifications and Standards/Rules Review Branch
January 2023 GWWMC Information Item
NC Groundwater Quality Standards
Federal Requirement No
North Carolina Rule 15A NCAC 02L .0202
Population Human Adults
Target use Ingestion
Household use
Standard endpoints
Noncancer
Cancer
Aqueous taste and odor
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North Carolina Groundwater Quality Standards
•Maximum allowable concentrations which may be tolerated without creating a threat to human health or which would otherwise render the groundwater unsuitable for its intended best usage
•Best Usage: existing or potential source of drinking water supply for humans
•Protect groundwaters of the state as a resource for human consumption
•Implemented in various programs including site clean-ups, risk assessments, health evaluations, etc.
Groundwater Quality Standards Rule
Title 15A NCAC Subchapter 02L –Groundwater Classifications and Standards
Section .0100: General Considerations
Section .0200: Classifications and Groundwater Quality Standards
.0201 Groundwater Classifications
.0202 Groundwater Quality Standards
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•Substances which are not naturally occurring and for which no
standard is specified shall not be permitted in concentrations at or
above the practical quantitation limit (PQL).
•Where the standard for a substance is less than the PQL, the
detection of that substance at or above the PQL constitutes a violation
of the standard.
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Groundwater Quality Standards Rule Language
15A NCAC 02L .0202 (b) and (c)
•Where two or more substances exist in combination, the Director shall
consider the effects of chemical interactions.
•Where naturally occurring substances exceed the established
standard, the standard shall be the naturally occurring concentration
as determined by the Director.
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Groundwater Quality Standards Rule Language cont.
15A NCAC 02L .0202 (b)
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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Developing Groundwater Quality Standards
15A NCAC 02L .0202 (d)
Using the following references 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)
Developing Groundwater Quality Standards cont.
Groundwater Standards Calculation
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Water consumption
Noncancer
𝐺𝐺𝐺𝐺𝐺𝐺𝐺𝐺=𝑅𝑅𝑅𝑅𝑅𝑅× 𝐵𝐵𝐺𝐺× 𝑅𝑅𝐺𝐺𝑅𝑅𝐺𝐺𝑅𝑅𝑅𝑅
Cancer 𝐺𝐺𝐺𝐺𝐺𝐺𝐺𝐺=𝑅𝑅𝑅𝑅× 𝐵𝐵𝐺𝐺𝑅𝑅𝐶𝐶𝐶𝐶× 𝐺𝐺𝑅𝑅𝑅𝑅
Toxicity benchmarks
RfD = Oral Reference Dose
CPF = Carcinogen Potency Factor
or Cancer Slope Factor (CSF)
Exposure estimates
RSC = Relative Source Contribution
(0.1 for inorganics; 0.2 for organics)
BW = Body Weight = 70 kg (adult)
WCR = Water Consumption Rate =
2 L/day (adults)
RL = Risk Level = 1x10-6
GW standard based on noncancer endpoint
7.00E-02 mg/kg/day
70 kg
0.2 unitless value
WI = average daily human adult water intake3 2 L/day
1000 = conversion factor 1000 µg/mg
Calculated GW Standard using noncancer endpoint 490 µg/L
GW Standard based on cancer endpoint
RL = risk level 1.00E-06
70 kg
q1* = carcinogenic potency factor (slope factor)4 0.029 (mg/kg /day) -1
WI = average daily human adult water intake3 2 L/day
1000 = conversion factor 1000 µg/mg
Calculated GW Standard using cancer endpoint 1.2 µg/L
RfD = reference dose1
WT = average adult human body weight2
GWQS = [(RL x WT) / (q1* x WI)] * 1000
GWQS = [(RfD x WT x RSC) / WI] * 1000
RSC= relative source contribution
WT = average adult human body weight2
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Groundwater Standard Methodology
How are chemicals chosen to receive IMACs?
Any person may request the Division of Water Resources Director to establish an IMAC for a substance for which a groundwater standard has not been established.
How are IMACs developed?
Following the guidelines in 15A NCAC 02L .0202(c) and the calculations and references in 15A NCAC 02L .0202(d) and (e).
Who establishes IMACs?
The Director of DWR.
Are IMACs legally enforceable?
Yes, per 15A NCAC 02L .0202.
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Interim Maximum Allowable Concentrations (IMACs)
15A NCAC 02L .0202(c): substances which are not naturally occurring and for which no standard is
specified shall not be permitted in concentrations at or above the practical quantitation limit (PQL)
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IMAC Establishment Process
15A NCAC 02L .0202(c)(1)-(4)
Any person may request the Director of the Division of Water Resources to establish, update, or remove an Interim Maximum Allowable Concentration (IMAC):
1.The Division reviews the request to determine whether the information submitted is in accordance with 15A NCAC 02L .0202(d) and (e).
2.The Director may request additional information from the requester if information is not in accordance with the rule. The Director returns the request if additional information is not provided.
3.At least 30 days prior to establishing, updating, or removing an IMAC for any substance, the Division shall provide public notice and opportunity for comment that an IMAC has been requested to be established, updated, or removed.
4.The Director shall establish, update, or remove the IMAC or return the request within 180 calendar days of receipt of a request.
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IMAC Establishment Process continued
5.Within 12 months of establishing an IMAC, the Director shall make a recommendation to the Commission whether:
a)a new groundwater standard in place of the IMAC should be established; or
b)the IMAC should expire.
6.An IMAC shall expire either:
a)the date the Commission declines to initiate rulemaking to adopt a new groundwater standard in place of the IMAC;
b)the effective date of the rule adopted by the Commission establishing a new groundwater standard in place of the IMAC; or
c)after initiating rulemaking, the date the Commission declines to adopt a new groundwater standard in place of the IMAC.
7.For any IMAC that expires prior to the adoption by the Commission of a new groundwater standard in place of the IMAC, any person may request an IMAC be established again.
15A NCAC 02L .0202(c)(5)-(9)
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IMAC Establishment Process Reporting
•If the Director establishes or updates an IMAC, the IMAC shall be posted
on DWR's website, and the Commission shall be notified in writing within
30 calendar days and at the next regularly scheduled Commission meeting.
•The Director shall provide an annual update to the Commission on the
status of pending IMAC requests and any IMACs that have been
established, updated or removed during the previous calendar year.
15A NCAC 02L .0202(c)(5)-(9)
Comparison of IMACs and Groundwater Standards
IMACs Groundwater Standards
Time-frame Temporary Permanent
Regulatory Framework 15 NCAC 02L .0202 15 NCAC 02L .0202
Scientific Review Process DPH/DWM secondary review DPH/DWM secondary review
Public Comment No Yes
Public Hearing No Yes
Fiscal Analysis No Yes
Public Notification of Value Yes (NC Register and Website)Yes (NC Register and Rule)
Legally Enforceable Yes Yes
Approval Process Division of Water Resources
Director
Environmental Management
Commission
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More information on IMACs can be found here:Groundwater IMACs
Periodic Review of the Groundwater Standards Rule
•15A NCAC 02L .0202 (g): Groundwater quality standards and interim
maximum allowable concentrations shall be reviewed on a triennial basis.
•DWR staff review the toxicological research and literature in accordance with 15A NCAC 02L .0202.
•DWR staff consider appropriate modifications and prepare reports which are reviewed by internal staff
•DWR submit prepared reports to DWM and DHHS toxicology staff for review and/or further discussion and comment
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Periodic Review of the Groundwater Standards Rule
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Development
•Staff review available guidance & literature and develop Triennial Review package
•Staff present TR to Environmental Commissions (GWWMC/EMC)
•Public notice & hearings
•TR goes to EMC for review/comment/modifications
State Approval
•EMC approves TR to become standards in rule
•RRC reviews TR for language/intent/legality and modifies/approves TR
•Triennial Review codified in NC state law
•15A NCAC 02L .0202 Groundwater Quality Standards rule
most recent review
•EMC approved revisions on March 10, 2022
•Revisions became effective April 1, 2022
•Information on rulemaking can be found here:
•Groundwater Triennial Review and Rulemaking
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Periodic Review of the Groundwater Standards Rule
Remaining IMACs
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•16 remaining IMACs will be included in the upcoming review of the groundwater standards
•They will be presented to the EMC for either removal or for adoption as a groundwater standard
•Prior to the next triennial review, any person may request that an IMAC be updated or removed, following the process in 02L .0202(c)
•More information on IMACs can be found here:Groundwater IMACs
Thank you!
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Bridget Shelton
Groundwater Quality Standards Coordinator
[e-mail]
(919)-707-9022
DWR, Classifications, Standards & Rules Review Branch:
https://deq.nc.gov/about/divisions/water-resources/planning/classification-
standards