DEQ-CFW_00019703

..............
This SOP provided by the Classifications and Standards Unit, DWQ-,--i I/ Y),
11100
�`TT' a
standards and establishment of new groundwater standards. :-
Ad istrative Code Rule
In accordance with "Classifications and Water Quality Standards Applicable to the Groundwaters of North
Carolina" (I 5A NCAC 02L .0202 (d)), the groundwater quality standards shall be established as the least of:
I . Systemic threshold concentration calculated as follows: [Reference Dose (mg/kg/day) x 70 kg (adult
body weight) x Relative Source Contribution (0.10 for inorganics; 0.20 for organics)]/[21iters/day
(avg. water consumption)];
2. Concentration which corresponds to an incremental lifetime cancer risk of I x 10-6;
3. Taste threshold limit value;
4. Odor threshold limit value;
5. Maximum contaminant level; or
6. National secondary drinking water standard.
The rule further states that, "The following references, in order of preference, shall be used in establishing
concentrations of substances which correspond to levels described in Paragraph (d) of this Rule":
1. Integrated Risk Information System (U.S. EPA)
2. Health Advisories (U.S. EPA Office of Drinking Water)
3. Other health risk assessment data published by the U.S. EPA
4. Other appropriate, published health risk assessment data, and scientifically valid peer -reviewed
published toxicological data.
Procedure
I . Calculate systemic threshold concentration following the equation in the 2L rule: [Reference Dose
(RfD) (mg/kg/day) x 70 kg (adult body weight) x Relative Source Contribution (0. 10 for inorganics;
0.20 for organics)]/[21iters/day (avg. water consumption)]. Obtain the RfD from the following sources
listed in priority ord , (for more infori-nation on these sources of information, see section below
"References for Toxicity Values"):
1. EPA Integrated Risk Information System (IRIS)
2. EPA Health Advisories
3. Other health risk assessment data published by the U.S. EPA, such as, but not limited to:
i. EPA Regional Table Toxicity Values (Regional Screening Levels for Chemical
Contaminants at Superfund Sites)
ii. EPA Provisional Peer Reviewed Toxicity Values (PPRTVs)
iii. EPA Health Effects Assessment Summary Tables (HEAST, 1997)
4. Other appropriate, published health risk assessment data, and scientifically valid peer -
reviewed published toxicological data.
i. Agency for Toxic Substances and Disease Registry (ATSDR) Chronic oral minimal risk
levels (MRLs)
ii. California EPA (CalEPA) Public Health Goals (PHGs)
iii. Other published relevant toxicological data.
DEQ-CFW-00019703

r77=7r#.MT!A'T, 721,77 M.71W,
Page 2 of 5
2. Calculate the concentration which corresponds to an incremental lifetime cancer risk of I X 10-6.
•b the cancer risk level or oral cancer slo-pe factor
When using a cancer risk level, calculate I X 10-6 risk using the following equation:
I X 10-6 risk level (mg/L) = I X 10-4 risk level (mg/L) x 0.01
When usin�_.a._CSF, a I X 10-6 risk level is calculated assuming a 70 Kg body weight and a 2 Liter per
day drinking water consumption rate. This narrative, is represented by the • equation:
I X 10-6 Risk x I x 70 Kg x I day = X mg/L
CSF (Risk/mg/Kg-day) 2L
below in priority order:
1. EPA Integrated Risk Information System (IRIS):
2. EPA Health Advisories: (Cancer risk levels for I X 10-4 risk for oral exposure sometimes
provided).
3. Other health risk assessment data published by the U.S. EPA
i. EPA Regional Table Toxicity Values
ii. EPA Provisional Peer Reviewed Toxicity Values (PPRTVs)
iii. EPA HEAST
4. Other appropriate, published health risk assessment data, and scientifically valid peer -reviewed
published toxicological data (e.g., ATSDR, CalEPA, other).
-3. Check the following reference for taste threshold values:
i. Young, W.F., Horth, H., Crane, R., Ogden, T. and Amott, M. 1996. Taste and Odour Threshold
Concentrations of Potential Potable Water Contaminants. Water Research, 30:2, pp.331-340.
* Record the "geometric mean taste threshold concentration".
ii. Other appropriate, scientifically valid peer -reviewed published data for taste threshold values.
4. Check the following references for ••• threshold values:
i. Young, W.F., Horth, H., Crane, R., Ogden, T. and Amott, M. 1996. Taste and Odour Thresho
Concentrations of Potential Potable Water Contaminants. Water Research, 30:2, pp.331-340
0 Record the +-• mean ••'t threshold concentration".
ii. Amoore, J.E. and Hautala, E. 1983. Odor as an Aid to Chemical Safety; Odor Thresholds
Compared with Threshold Limit Values and Volatilities for 214 Industrial Chemicals in Air
• Water Dilution. Journal ofApplied Toxicology, • 3, No. 6,1983.
Record the "water odor threshold" but •• • record the value if it is listed in
parentheses (these values are considered to be very uncertain).
iii. Other appropriate, scientifically valid peer -reviewed published data for odor threshold values.1
*** Note: If taste or odor threshold values are provided in more than one reference, record all
but use the lower of the values for determining the revised 2L.
DEQ-CFW-00019704

Groundwater Standards SOP
Page 3 of 5
5. Record the Maximum Contaminant Level (MCL) from the EPA Office of Ground Water and Drinkin
Water internet site: littp://www.gpa.gov/safewater/inel.htinl#incls
6. Record the Secondary Maximum Contaminant Level (SMCL) from the EPA Office of Ground Water
and Drinking Water internet site: ht!p://www.epa.gov/safewater/contaminalits/index.html
of significant figures).
References for Toxicity'Talues
EPA Integrated Risk Information System (IRIS) database: EPA database of human health effects that
may result from exposure to various substances found in the environment. IRIS consists of individual
files on over 200 chemicals that contain oral Reference Doses (RfDs), inhalation Reference
Concentrations (RfCs), hazard identification, oral cancer slope factors, and oral and inhalation unit
risks for carcinogenic effects. The information contained in IRIS represents the consensus opinion of
health scientists at the EPA. hLtp://www.gp.a.gov/iris/index.html
0 EPA Health Advisories: EPA Office of Water guidance values for unregulated chemicals found in
drinking water based on noncancer health effects for different durations of exposure (I -day, I 0-day,
and lifetime). Chronic oral reference doses, carcinogenic classification, and drinking water levels
EPA Regional Table Toxicity Values (Screening Levelsfor Chemical Contaminants at Supe�fund
Sites): The EPA Regional Table lists toxicity values that are used by EPA to calculate Screening
Levels for five direct contact exposure pathways (residential soil, industrial soil, residential air,
industrial air, and tap water). The Regional Table lists the source of the toxicity values used: EPA's
IRIS; EPA's PPRTVs; ATSDR; California EPA; PPRTV Appendix Values; and HEAST.
littp://www.qpa.gov/reg3hsed/risk/human/rb-concentration table/
EPA Provisional Peer Reviewed Toxicity Values,,�M: EPA's National Center for
Environinental Assessment, Superfund Health Risk Technical Support Center calculates provisional
toxicity values. These values are for EPA internal use and are also provided to State risk assessors
(upon request). They have not been verified through the EPA's formal review process and are not
available online.
MRLs - estimates of the daily human exposure to a hazardous substance that is likely to be without
appreciable risk of adverse noncancer health effects over a specified duration of exposure. They are
ATSDR's chronic oral minimum risk level may be used as a chronic oral reference dose.
OEQ-CFVV_00019705

MIT K_
consuming the water on a daily basis over a lifetime, are also available
EPA PPRTVs Screening Toxicity Values: These are screening values located in the appendix of
certain PPRTV assessments. EPA has less confidence in a screening toxicity value than in a PPRTV;
however, current EPA methodologies are used to derive them and they also receive external peer
Health Effects Assessment SummM Tables (HEAST): EPA Superfund 1997 table of provisional risk
values. The risk values in this table have generally been replaced by PPRTV values. It is not available
Recoinmendations and Public Input Processes
The DWQ will proceed through rulemaking and public input processes in accordance with North
Carolina General Statute (NCGS) 150B to revise and establish groundwater standards. Public input
opportunities will always be offered, at a minimum, in accordance with the requirements outlined in
Before presenting a groundwater standard proposal to the Groundwater Committee of the EMC to
commence with rulemaking, the DENR DWQ will notify the NC Department of Health and Human
Services Division of Public Health (DPH) and the NC Department of Envirom-nent and Natural
Resources Division of Waste Management (DWM) by a letter that includes enough information to
provide a clear indication of the basis and process used to determine the proposed standard(s). The
supporting information used to develop the proposal will also be included: if a reference is available
on the internet, the link will be provided; if a reference is not available on the internet, the document
will be provided. DWQ will make every effort to send letter notification to DPH and DWM thirty (30)
days prior for single standards and sixty (60) days prior for proposals involving more than one
standard. Information on all proposals received by DPH and DWM will be treated as sensitive,
internal material not to be distributed. The purpose of the written noticeis to request the DPH and
DWM to review and provide comment on 2L standards development to DWQ prior to the initiation of
the rulemaking process and prior to the APA public comment period. Cornment and/or information are
to be provided to DWQ on the specific proposal within the timeframe requested. DWQ Will consider
the provided information prior to the DWQ decision to make a recommendation to the Groundwater
process for revising and establishing groundwater standards. Therefore, there may be, at the judgment
of the DWQ Director or at the agreement of the three agencies, a good reason to move forward to the
Groundwater Comi-nittee of the EMC, or otherwise, with any specific proposal without the additional
thirty -day or sixty-day comment period between the agencies, and the Director of DWQ may deem a
shorter timeframe as appropriate. Nothing in this SOP document binds the DWQ or the Director's
authorities established pursuant to the North Carolina Administrative Code.
OEQ-CFVV_00019706

Page 5 of 5
DENR Science Advisory Board on Toxic Air Poflutants Involvement
The DWQ will consult with the DENR Science Advisory Board on Toxic Air Pollutants (SAB), at t
discretion of the DWQ and the SAB, for professional toxicological input on any potential or existin
groundwater standard.
Interim Maximum Allowable Concentrations (IMACs)
In accordance with 15A NCAC 2L.0202 (c), any person may petition the Director of the Division of
Water Quality to establish an interim maximum allowable concentration for a substance for which a
standard has not been established. The DWQ will review such requests for establishing an IMAC.
All IMACs are temporary numbers. The same procedure for determining an appropriate standard as
described above will be used for determining an INIAC, including the procedure described above for
recommendations and public input processes, prior to submitting the IMAC request to the DWQ
OEQ-CFVV_00019707