North Carolina Administrative Code › Title 15A - Environmental Quality › Chapter 02 - Environmental Management › Subchapter L - GROUNDWATER CLASSIFICATION AND STANDARDS › Section .0400 - RISK-BASED ASSESSMENT AND CORRECTIVE ACTION FOR PETROLEUM UNDERGROUND STORAGE TANKS › Section 02L .0411 - ESTABLISHING MAXIMUM SOIL CONTAMINATION CONCENTRATIONS

Current through Register Vol. 39, No. 2, July 15, 2024
The Department shall publish on the Department website and
					 annually revise maximum soil contaminant concentrations to be used as soil
					 cleanup levels for contamination from petroleum underground storage tank
					 systems. The Department shall establish maximum soil contaminant concentrations
					 for residential, industrial/commercial, and soil-to-groundwater exposures as
					 follows:
(1) The following equations
				  and references shall be used in establishing residential maximum soil
				  contaminant concentrations. Equation 1 shall be used for each contaminant with
				  an EPA carcinogenic classification of A, B1, B2, C, D or E. Equation 2 shall be
				  used for each contaminant with an EPA carcinogenic classification of A, B1, B2
				  or C. The maximum soil contaminant concentration shall be the lower of the
				  concentrations derived from Equations 1 and 2.
(a) Equation 1: Non-cancer Risk-based
				  Residential Ingestion Concentration
Soil mg/kg =[0.2 x oral chronic reference dose x body
					 weight, age 1 to 6 x averaging time noncarcinogens] / [exposure frequency x
					 exposure duration, age 1 to 6 x (soil ingestion rate, age 1 to 6 /
					 106 mg/kg)].
(b) Equation 2: Cancer Risk-based Residential
				  Ingestion Concentration
Soil mg/kg =[target cancer risk of
					 10-6 x averaging time carcinogens] / [exposure
					 frequency x (soil ingestion factor, age adjusted /
					 106mg/kg) x oral cancer slope factor]. The age
					 adjusted soil ingestion factor shall be calculated by: [(exposure duration, age
					 1 to 6 x soil ingestion rate, age 1 to 6) /( body weight, age 1 to 6)] +
					 [((exposure duration, total - exposure duration, age 1 to 6) x soil ingestion,
					 adult) / (body weight, adult)].
(c) The exposure factors selected in
				  calculating the residential maximum soil contaminant concentrations shall be
				  within the recommended ranges specified in the following references or the most
				  recent version of these references:
(i) EPA,
				  2011. Exposure Factors Handbook, incorporated by reference including subsequent
				  amendments or editions and may be obtained electronically free of charge from
				  the United States Environmental Protection Agency website at
https://cfpub.epa.gov/ncea/risk/recordisplay.cfm?deid=236252
;
(ii) EPA, 1991. Risk Assessment Guidance for
				  Superfund: Volume I Human Health Evaluation Manual (Part B, Development of Risk
				  Based Preliminary Remediation Goals), incorporated by reference including
				  subsequent amendments or editions and may be obtained electronically free of
				  charge from the United States Environmental Protection Agency website at
https://www.epa.gov/risk/risk-assessment-guidance-superfund-rags-part-b
;
(iii) EPA. Regional Screening Level Generic
				  Tables (RSL) and User's Guide, incorporated by reference including subsequent
				  amendments or editions and may be obtained electronically free of charge from
				  the United States Environmental Protection Agency website at
https://www.epa.gov/risk/regional-screening-levels-rsls
;
				  and
(iv) EPA, 2018. Region 4 Human
				  Health Risk Assessment Supplemental Guidance, incorporated by reference
				  including subsequent amendments or editions and may be obtained electronically
				  free of charge from the United States Environmental Protection Agency website
				  at
https://www.epa.gov/sites/production/files/2018-03/documents/hhra_regional_supplemental_guidance_report-march-2018_update.pdf
.
(d) The following references or
				  the most recent version of these references, in order of preference, shall be
				  used to obtain oral chronic reference doses and oral cancer slope factors:
(i) EPA. Integrated Risk Information System
				  (IRIS) Computer Database, incorporated by reference including subsequent
				  amendments or editions and may be obtained electronically free of charge from
				  the United States Environmental Protection Agency website at
https://www.epa.gov/iris
;
(ii) EPA. Health Effects Assessment Summary
				  Tables (HEAST), incorporated by reference including subsequent amendments or
				  editions and may be obtained electronically free of charge from the United
				  States Environmental Protection Agency website at
https://epa-heast.ornl.gov
;
(iii) EPA. Regional Screening Level Generic
				  Tables (RSL) and User's Guide;
(iv)
				  EPA, 2018. Region 4 Human Health Risk Assessment Supplemental Guidance;
				  and
(v) Other scientifically valid
				  peer-reviewed published health risk assessment data, and scientifically valid
				  peer-reviewed published toxicological data.