A3+-+NDRBCA+Technical+Guidance.pdf

North Dakota Department of Environmental Quality

NORTH DAKOTA RISK-BASED

CORRECTIVE ACTION (NDRBCA)

TECHNICAL GUIDANCE

January 2023

NDRBCA Guidance Document January 2023 i

TABLE OF CONTENTS

1.0 BACKGROUND AND OBJECTIVE 1-1

1.1 INTRODUCTION 1-1

1.2 NDDEQ AUTHORITY 1-1

1.3 SITE CLEANUP AND REMEDIATION PROGRAMS 1-2

1.3.1 Brownfields Program 1-2

1.3.2 Voluntary Response Action 1-2

1.3.3 Leaking &Underground Storage Tank Program 1-3

1.3.4 Hazardous Waste and PCB Program 1-3

1.3.5 Groundwater Protection Program 1-3

1.3.6 Spill Investigation Program 1-3

2.0 OVERVIEW OF NDRBCA PROCESS 2-1

2.1 INTRODUCTION 2-1

2.2 RISK-BASED CORRECTIVE ACTION PROCESS 2-2

2.2.1 Site Discovery 2-2

2.2.2 Determination and Abatement of Imminent Threat(s) 2-2

2.2.3 Initial Site Characterization and Development of Conceptual Site Model 2-3

2.2.4 Tier 1 Evaluation 2-4

2.2.5 Tier 2 Evaluation 2-4

2.2.6 Tier 3 Evaluation 2-5

2.2.7 Development and Implementation of Risk Management Plan

(RMP) 2-5

2.3 RISK-BASED TARGET LEVELS WITHIN THE NDRBCA

PROCESS 2-6

2.4 RATIONALE AND CHARACTERISTICS OF TIERED

APPROACH 2-7

2.5 DOCUMENTATION OF THE NDRBCA PROCESS 2-7

3.0 SITE DISCOVERY AND MANAGEMENT OF IMMINENT THREATS 3-1

3.1 SITE DISCOVERY 3-1

3.2 REPORTING A RELEASE 3-1

4.0 DATA NEEDS FOR TIERED RISK EVALUATION 4-1

4.1 INTRODUCTION 4-1

4.2 SITE INFORMATION 4-2

4.2.1 Site Location Map 4-2

4.2.2 Site Map 4-3

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4.2.3 Ground Surface Conditions 4-3

4.2.4 Location of On and Adjacent Utilities 4-3

4.2.5 On-Site Groundwater Use 4-4

4.2.6 Local Hydrogeology and Aquifer Characteristics 4-5

4.3 DESCRIPTION OF THE SOURCE AND COCs 4-5

4.3.1 History of Activities at the Site 4-6

4.3.2 Location and Date of Spill or Release 4-6

4.3.3 Quantity of Spill and Release 4-7

4.3.4 Product(s) or Chemical(s) Released 4-7

4.4 ADJACENT LAND USE AND RECEPTOR INFORMATION 4-7

4.4.1 Current Land Use 4-8

4.4.2 Future Land Use 4-8

4.4.3 Off-site Groundwater Use 4-8

4.4.4 Ecological Receptor Survey 4-9

4.5 ANALYSIS OF CURRENT AND FUTURE GROUNDWATER USE 4-9

4.5.1 Current Groundwater Use 4-9

4.5.2 Future Groundwater Use 4-10

4.6 VADOSE ZONE 4-11

4.6.1 Vadose Zone and Depth to Groundwater 4-11

4.6.2 Vadose Zone Characteristics 4-11

4.7 SATURATED ZONES 4-12

4.7.1 Characteristics of Saturation Zone 4-12

4.7.1.1 Hydraulic Conductivity 4-13

4.7.1.2 Hydraulic Gradient 4-13

4.7.1.3 Saturated Zone Soil Geotechnical Parameters 4-13

4.7.2 Occurrence and Rate of Natural Attenuation 4-14

4.8 SURFACE WATER BODY 4-15

4.9 DELINEATION OF IMPACTS 4-16

4.9.1 Delineation of Impacts in Soil and Groundwater 4-16

4.9.2 Delineation of Impacts in Other Media 4-18

4.10 ECOLOGICAL RISK EVALUATION 4-18

4.10.1 Level 1 Ecological Risk Evaluation 4-19

4.10.2 Level 2 Ecological Risk Evaluation 4-19

4.10.3 Level 3 Ecological Risk Evaluation 4-20

4.11 DISTRIBUTION OF CHEMICALS OF CONCERN IN SOIL 4-20

4.11.1 Logging of Soil and Groundwater Monitoring Well Boreholes 4-21

4.12 DISTRIBUTION OF CHEMICALS OF CONCERN IN

GROUNDWATER 4-21

4.12.1 Delineation of Groundwater Impacts 4-21

4.12.2 Determination of Plume Stability 4-22

4.12.3 Groundwater Sampling 4-22

4.13 DISTRIBUTION OF CHEMICALS OF CONCERN IN THE VAPOR

MIGRATION TO INDOOR AIR PATHWAY 4-23

4.14 DISTRIBUTION OF CHEMICALS OF CONCERN IN SEDIMENTS

AND SURFACE WATER BODIES 4-23

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4.15 COLLECTION AND ANALYSES OF ENVIRONMENTAL

SAMPLES 4-24

4.16 INFORMATION SOURCES FOR DATA COLLECTION 4-24

5.0 GENERAL CONSIDERATIONS FOR RISK EVALUATION 5-1

5.1 DEVELOPMENT OF AN EXPOSURE MODEL 5-1

5.1.1 Land Use 5-2

5.1.1.1 Determine Current Land Use 5-2

5.1.1.2 Determine Most Likely Future Land Use 5-2

5.1.2 Human Receptors 5-3

5.1.3 Human Exposure Pathways and Routes of Exposure 5-3

5.1.3.1 Pathways for Inhalation 5-4

5.1.3.2 Pathways for Surficial Soils (0 - 2 feet bgs) 5-4

5.1.3.3 Pathways for Subsurface Soils

(>2 feet bgs to the water table) 5-4

5.1.3.4 Pathways for Groundwater 5-5

5.1.3.5 Protection for Surface Water and Sediments 5-5

5.1.3.6 Other Pathways 5-5

5.1.4 Exposure Domain 5-5

5.1.5 Documentation of the Exposure Model 5-6

5.2 CALCULATION OF RISK BASED TARGET LEVELS 5-6

5.3 EVALUATION OF GROUNDWATER USE 5-6

5.3.1 Current Conditions 5-6

5.3.2 Future Conditions 5-7

5.3.3 Evaluation of Complete Pathway 5-8

5.4 SURFACE WATER PROTECTION 5-9

5.5 ESTIMATION OF REPRESENTATIVE CONCENTRATIONS 5-10

5.6 EVALUATION OF LIGHT NON-AQUEOUS PHASE LIQUID

(LNAPL) 5-10

5.6.1 Protection against Explosive Risk 5-11

5.6.2 LNAPL Plume Shall be Fully Delineated 5-11

5.6.3 LNAPL Tiered Risk Evaluation 5-11

5.6.4 LNAPL Plume Stability 5-12

5.6.5 Practicability of LNAPL Removal 5-12

5.7 CONSIDERATION OF TOTAL PETROLEUM HYDROCARBONS

(TPH) 5-12

6.0 TIER 1 EVALUATION 6-1

6.1 STEP 1: COMPILATION OF DATA AND IDENTIFICATION OF

DATA GAPS 6-1

6.2 STEP 2: DEVELOPMENT OF CONCEPTUAL SITE MODEL 6-2

6.3 STEP 3: COLLECTION OF DATA TO FILL DATA GAPS, IF ANY 6-2

6.4 STEP 4: CALCULATION OF EXPOSURE PATHWAY-SPECIFIC

REPRESENTATIVE CONCENTRATIONS 6-2

6.5 STEP 5: SELECTION OF TIER 1 RBSLs AND COMPARISON WITH

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MAXIMUM CONCENTRATIONS 6-3

6.6 STEP 4: RECOMMENDATIONS FOR THE NEXT COURSE OF

ACTION 6-3

6.7 STEP 7: DOCUMENTATION OF TIER 1 EVALUATION 6-4

7.0 TIER 2 EVALUATION 7-1

7.1 STEP 1: COMPILATION OF SITE-SPECIFIC FATE AND

TRANSPORT PARAMETERS 7-1

7.1.1 Soil Parameters 7-2

7.1.1 Groundwater Parameters 7-5

7.2 STEP 2: COMPILATION OF SITE-SPECIFIC EXPOSURE

FACTORS 7-7

7.3 STEP 3: CALCULATION OF TIER 2 SSTLs 7-7

7.4 STEP 4: CALULATION OF REPRESENTATIVE CONCENTRATION

7.5 STEP 5: COMPARISION OF TIER 2 SSTLs WITH

REPRESENTATIVE CONCENTRATIONS 7-8

7.6 STEP 6: RECOMMENDATION FOR THE NEXT COURSE OF

ACTION 7-8

7.7 STEP 7: DOCUMENTATION OF TIER 2 EVALUATION AND

RECOMMENDATIONS 7-10

8.0 TIER 3 RISK ASSESSMENT 8-1

8.1 STEP 1: DEVELOP TIER 3 WORK PLAN 8-1

8.2 STEP 2: COLLECT ADDITIONAL DATA, IF NECESSARY 8-2

8.3 STEP 3: CALCULATION OF TIER 3 SSTLs AND

REPRESENTATIVE CONCENTRATIONS 8-3

8.4 STEP 4: DEVELOPMENT AND IMPLEMENTATION OF RISK

MANAGEMENT PLAN 8-3

8.5 STEP 5: DOCUMENTATION OF TIER 3 EVALUATON 8-4

9.0 RISK MANAGEMENT PLAN 9-1

9.1 NEED FOR A RISK MANAGEMENT PLAN 9-1

9.2 RISK MANAGEMENT PLAN 9-1

9.3 COMPLETION OF RISK MANAGEMENT ACTIVITIES 9-2

9.4 PROCEDURE FOR LETTER OF CLOSURE 9-2

10.0 REFERENCES 10-1

LIST OF TABLES

Table 2-1 Comparison of Risk Assessment Options for Various Tiers Table 5-1 Vapor Concentrations Protective of Explosive Hazards Table 5-2 Weight Percent for COCs in Different Products v

Table 5-3 Constituent Fraction of TPH Groups Table 6-1(a) Tier 1 Risk Based Screening Levels for Resident Table 6-1(b) Tier 1 Risk Based Screening Levels for Commercial/Industrial Worker

LIST OF FIGURES

Figure 2-1 Primary Activities Conducted under the NDRBCA Process Figure 2-2 NDRBCA Process Flowchart Figure 7-1 Schematic Description of Domenico’s Groundwater Model

LIST OF APPENDICES

Appendix A Calculation of Risk Based Target Levels (RBTLs) Appendix B NDRBCA Report Forms Appendix C Ecological Risk Evaluation Checklists Appendix D Geotechnical Parameters Appendix E Estimation of Representative Soil and Groundwater Concentrations Appendix F Equations included in the NDRBCA Software Appendix G Protection of Utilities

ABBREVIATIONS

AST Aboveground Storage Tank ASTM American Society for Testing and Materials COC Chemical of Concern CI Confidence Interval CSM Conceptual Site Model DRO Diesel Range Organics ED Exposure Domain EM Exposure Model ET Ecotox Thresholds EP Exposure Pathway ERE Ecological Risk Evaluation GRO Gasoline Range Organics GWPP Groundwater Protection Program GWSDAT Ground Water Spatio-Temporal Data Analysis Tool HH&E Human Health & Environment HWP Hazardous Waste & PCB Program LUST Leaking Underground Storage Tank MCL Maximum Contaminant Level NAPL Light Non-Aqueous Phase Liquid NDAC North Dakota Administrative Code NDCC North Dakota Century Code NDDEQ North Dakota Department of Environmental Quality NDPTRCF North Dakota Petroleum Tank Release Compensation Fund NDRBCA North Dakota Risk Based Corrective Action vi

NFA No Further Action NGVD National Geodetic Vertical Datum NOAA National Oceanic and Atmospheric Administration ORO Oil Range Organics PAH Polynuclear Aromatic Hydrocarbon PCB Polychlorinated Biphenyl PCE Tetrachloroethylene PID Photoionization Detector POE Point of Exposure PVC Polyvinyl chloride RA Risk Assessment RAP Remedial Action Plan RBSL Risk Based Screening Level RBTLS Risk Based Target Level RC Representative Concentration RCRA Resource Conservation Recovery Act RM Risk Management RMP Risk Management Plan ROE Route of Exposure RP Responsible Party RL Reporting Limit RSL Regional Screening Level SC Site Characterization SSTL Site Specific Target Level TDS Total Dissolved Solids TCE Trichloroethylene TPH Total Petroleum Hydrocarbons TSDF Treatment, Storage, and Disposal Facility USEPA United States Environmental Protection Agency USDA United States Dryland Agriculture USGS United States Geological Survey UST Underground Storage Tank VRA Voluntary Response Action XRF X-Ray Fluorescence

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NDRBCA Guidance Document Page 1-1 January 2023

1.0

BACKGROUND AND OBJECTIVE

1.1 INTRODUCTION

The intent of this guidance is to outline key procedures for implementing consistent and successful contaminant assessment and risk-based remediation strategies across applicable North Dakota Department of Environmental Quality (NDDEQ) programs. The NDDEQ has authority to use a risk-based decision-making process at contaminated sites and has previously applied a risk-based process. The process described in this document is termed North Dakota Risk Based Corrective Action (NDRBCA). It is consistent with the RBCA standard developed by the American Society for Testing and Materials (ASTM E1739- 95(2015)).

This guidance applies to contaminated, or potentially contaminated, sites and will guide the user through the development of Risk-Based Target Levels (RBTLs) that are protective of current and future human health and environment (HH&E).

This guidance will be applicable to newly identified release sites, on-going projects as appropriate, newly discovered incidents/contamination at previously closed sites, and other projects, as required by the NDDEQ. The NDDEQ will not seek to re-open or reevaluate previously closed sites unless there has been a significant change in site conditions or planned site use that may impact HH&E. New requests, such as for the issuance of a certificate of completion as described in North Dakota Century Code (NDCC) 23.1-10-15, for sites previously granted letters of No Further Action may result in re-assessment through this process.

This guidance illustrates the type and format of information that should be collected and presented in a Remedial Action Plan (RAP) to demonstrate that a risk-based strategy is appropriate for the protection of human health and the environment. This guidance provides a technically defensible procedure for establishing RBTLs at impacted sites (Refer Section 2.3 and Appendix A).

This guidance is intended for use by environmental professionals with knowledge of environmental risk evaluation principles. Prior experience and/or training will be necessary for an individual to correctly implement the NDRBCA process.

1.2 NDDEQ AUTHORITY

The NDDEQ is established as the primary state environmental agency under NDCC Article

23.1. The duties of the NDDEQ include implementation of environmental rules and regulations, including oversight of environmental remediation or reclamation projects.

The following NDDEQ programs manage remediation projects:

1. Brownfields Program

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2. Voluntary Response Action Program

3. Leaking & Underground Storage Tank Programs

4. Hazardous Waste and PCB Program

5. Groundwater Protection Program

6. Spill Investigation Program

All work conducted as part of the NDRBCA process must operate in accordance with all applicable rules and regulations. Nothing in this document overrules or supplants existing rules or regulations. This document is not intended to be used as an initial response to an active spill. To report an active spill or discovery of contamination, please call the North Dakota State Radio 24 Hour Hotline at 1.833.99SPILL (1.833.997.7455) or report online to the North Dakota Unified Spill Reporting System at https://www.spill.nd.gov/.

A brief description of each of the programs under which site characterization (SC), risk evaluation (RE) and risk management (RM) activities are conducted in North Dakota are discussed below.

1.3 SITE CLEANUP AND REMEDIATION PROGRAMS

1.3.1 Brownfields Program

The Brownfields Program is a non-regulatory program operated by the Hazardous Waste & PCB Program. The goal of the Brownfields Program is to return contaminated properties to an economically viable state by addressing contamination at the property. This means the Brownfields Program will use the NDRBCA process to make management decisions such as remedy selection, remediation targets, institutional control decisions, and others related to the direct management of a site.

1.3.2 Voluntary Response Action Program

The Voluntary Response Action (VRA) program provides a roadmap for developers, landowners, financial institutions, and technical experts to conduct contaminated site cleanups in a consistent manner. The goal of the VRA program is to manage sites where contamination has been fully delineated, risks have been assessed, and those risks have been mitigated and documented. VRA differs from the NDDEQ required responses (such as an environmental incident or spill) in that the NDDEQ has not required remediation or corrective action. Sites under an NDDEQ directive may not receive liability protection until the directive has been resolved. VRA projects must adhere to the requirements of NDCC §23.1-10-15: Voluntary response actions – Liability protection – Procedures.

The NDDEQ will utilize the procedures outlined in this document for VRA projects. All requirements outlined in NDCC §23.1-10-15 have been identified and are discussed in relation to this document in the NDRBCA & Voluntary Response Actions guidance document. Note that nothing in this document overrules or supersedes the requirements of NDCC §23.1-10-15. For more information about VRA and liability protection, please contact the NDDEQ directly.

https://www.spill.nd.gov/

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1.3.3 Leaking & Underground Storage Tank Programs

The Underground Storage Tank (UST) Program works with owners and operators of underground storage tanks to ensure that compliance, leak detection, new installations, upgrades, and tank closures are completed in accordance with North Dakota's UST Rules.

The North Dakota UST Program is also in charge of ensuring that leaking underground storage tank (LUST) sites are reviewed and managed. The UST Program may require work to investigate, monitor or remediate the LUST sites. If the owner/operator is unable or unwilling to pay for these activities or if there is no responsible party (RP), the UST Program may write a contract that uses federal LUST Trust monies to fund this work. The funds used in LUST contracts are cost recoverable. If the RP performs the work and is eligible for funding, the North Dakota Petroleum Tank Release Compensation Fund (NDPTRCF) may be used as a funding source for the work.

1.3.4 Hazardous Waste and PCB Program

The Hazardous Waste and PCB Program (HWP) primarily oversees projects involving the release of hazardous wastes and/or hazardous constituents from regulated hazardous waste generators, or permitted transport, disposal, or treatment facilities (TSDFs). The NDRBCA process will be used in these cases for making regulatory decisions related to the release of contaminants regulated under the North Dakota Hazardous Waste Management Rules (NDAC §33.1-24). These decisions will include the selection of remediation targets, the need for institutional controls, and for determining if no further action is required at a site.

Note that PCB releases are a joint management effort between the HWP and the United States Environmental Protection Agency (USEPA), with many of the remediation targets being defined in federal regulations, and the NDRBCA process will not likely be utilized for PCB sites.

1.3.5 Groundwater Protection Program

The Groundwater Protection Program provides general technical oversight for activities related to contaminant releases/discharges under the authority of NDCC §23.1-11, including data interpretation and evaluations of site-specific conditions, contaminant levels, and associated potential health risks, and appropriate remedial alternatives, and processing requests for site closure and releases of liability.

1.3.6 Spill Investigation Program

The Spill Investigation Program oversees multiple types of releases throughout North Dakota. Any spill or discharge of liquid or solid (not gaseous) waste which may cause pollution of waters of the state must be reported immediately under North Dakota Administrative Code 33-16-02.1. The Spills Investigation Program reviews incidences reported to the North Dakota Unified Reporting System and assigns cases to the appropriate oversight program.

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The Spills Investigation Program has oversight for oil and gas releases that migrate off well pads, pipeline releases, and trucking accidents. This includes contaminates like natural gas condensates, production water, emulsion, crude oil, and formation water.

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2.0

OVERVIEW OF NDRBCA PROCESS

2.1 INTRODUCTION

The NDRBCA process begins when a contaminated site is identified. The process includes all subsequent activities required to ensure that the site does not pose an unacceptable risk to HH&E due to residual chemicals at the site. The NDRBCA process consists of the following three primary activities:

• Site characterization (SC): the collection of data to delineate the impacts in soil, groundwater, soil vapor, surface water, sediments, outdoor air, and indoor air, to protect HH&E. Additionally, information related to current and future land use;

characteristics of the impacted media; and current and future receptors shall be collected. Information collected during SC is used to develop a conceptual site model (CSM) that includes an exposure model (EM).

• Risk Assessment (RA): the calculation of risk-based target levels (RBTLs) as discussed in the Section 2.3 and Appendix A, under current and reasonable future land use scenarios. A RA requires identifying the impacted media, chemical of concern (COC), receptors, exposure pathways, and routes of exposure (ROE). An exposure pathway is the course chemicals travel from a source to the receptor and the route of exposure is the way the COC enters the receptor. A receptor is an entity that must be protected. The results of the RA are used to determine and implement the nature and scope of risk management activities.

• Risk Management (RM): the selection of cleanup levels for the various media and comparison with environmental media (media) specific representative concentrations (RCs), selection of risk management activities, and their implementation to ensure that the residual chemicals at the site are protective of HH&E under current and reasonably anticipated future conditions. RM activities include remediation activities and/or institutional controls.

Figure 2-1 illustrates these primary activities. The activities are fundamentally technical and rely on a variety of scientific disciplines such as geology, hydrology, engineering, chemistry, toxicology, ecology, and land use planning. Due to the inherent variability and uncertainty regarding several factors that affect SC, RA, and RM, multiple assumptions are necessary. These assumptions must be consistent with state and federal laws and regulations.

The implementation of the above activities involves numerous stakeholders. These include, but are not limited to, (i) the RP who is typically responsible to pay for and implement all the activities, (ii) service providers hired by the RP who implement the activities, and (iii) regulators who ensure that the activities are conducted in accordance with state and federal guidelines. Additional stakeholders include, but are not limited to, the public, proximate landowners, future landowners, insurance companies, and financial institutions.

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2.2 RISK-BASED CORRECTIVE ACTION PROCESS

The NDRBCA decision-making process is illustrated in Figure 2-2 and discussed below.

2.2.1 Site Discovery

The stakeholders may learn about a contaminated site under a variety of circumstances that include but are not limited to:

• Citizen complaints,

• Investigations conducted as a part of real estate transactions,

• Investigations conducted in anticipation of land development,

• Environmental impacts observed in surface water bodies, and

• Accidents and spills that occur as a part of exploration, manufacturing, and transportation activities.

NDRBCA does not change any of the responsibilities or obligations for a RP, instead it provides a consistent streamlined process to manage the contaminated or potentially contaminated sites.

The process of site discovery and notification is further discussed in Section 3.0.

2.2.2 Determination and Abatement of Imminent Threat(s)

Upon discovery of contamination, the North Dakota Unified Spill Reporting System should be notified by calling 1-833-99SPILL (1.833.997.7455) or reported online at https://www.spill.nd.gov/.

If there is an imminent threat to HH&E, the RP will be required to take actions necessary to end the hazardous substance emergency, stop the release of chemicals to the environment and ensure the safety of HH&E. After the completion of such activities, a written report must be submitted to the NDDEQ to document the activities implemented and confirm that all imminent threats have been abated. The RP may also be requested to include recommendations for any additional work necessary for the continued protection of HH&E. Typically, these activities will include site characterization and the development of a conceptual site model (CSM).

Determination and abatement of imminent threat(s) are discussed in Section 3.0.

2.2.3 Initial Site Characterization and Development of Conceptual Site Model

Site characterization includes identification of the source, determination of the COCs, collection of data for all media affected by the release, current and reasonable future land use and utilities. This step focuses on fieldwork (drilling of soil borings; installation of

NDRBCA Guidance Document Page 2-3 January 2023 soil vapor ports and groundwater monitoring wells; collection of soil, soil vapor, and groundwater samples; etc.) to identify the maximum concentrations of COCs in the affected media and the extent of impacts in each media. The level of effort (number of sampling points, location, and frequency of sampling) necessary for an adequate characterization is dependent upon site-specific conditions combined with professional judgement.

Impacts should be delineated to levels necessary to protect the receptors from a complete route of exposure. For example, at a commercial/industrial site with acceptable land use restrictions, the delineation criteria will be the commercial/industrial Tier 1 Risk-Based Screening Levels (RBSLs). Additionally, if an ecological threat exists, delineation must be to the levels protective of both the ecological and human receptors. To the extent possible, the laboratory reporting limits for all COCs must be lower than the corresponding delineation levels i.e., the applicable Risk-Based Screening Levels. Refer to Appendix E for discussion of reporting limits.

A CSM qualitatively and to a limited extent quantitatively describes all the relevant site-specific factors that determine the risk to HH&E and is the framework for management of risk at a site. The CSM should be documented using narrative descriptions, diagrams, and flow charts, as appropriate. It may include attachments such as boring logs, monitoring well construction details, and laboratory reports. The CSM should be updated as new site-specific information is collected and integrated into the understanding of the site.

Key elements of the CSM include:

1. The chemical release scenario, source(s), and COCs,

2. Spatial and temporal distribution of COCs in the various impacted media,

3. Current and future on-site/off-site land use, groundwater use, and characteristics of surface water bodies that may potentially be affected by site COCs,

4. Description of any known existing or proposed land or water use restrictions,

5. Description of media potentially impacted by the COCs (vadose zone soil, groundwater, surface water, indoor, etc.)

6. Remedial activities conducted to date, if any, and

7. An EM that identifies the receptors, exposure pathways, and routes of exposure under current and reasonable future land use conditions.

The extent of contamination and complete evaluation of routes of exposure, not the property boundaries, affect the extent of SC activities. The amount of data collected must allow the development and validation of the CSM.

Data required to develop a CSM and EM are discussed in Sections 4.0 and 5.0.

2.2.4 Tier 1 Evaluation

If the site concentrations exceed the relevant Tier 1 RBSLs (refer Section 2.6), the RP may choose to complete a Tier 2 risk evaluation or to select the Tier 1 RBSLs as the cleanup

NDRBCA Guidance Document Page 2-4 January 2023 levels. Tier 1 RBSLs specific to the COC, media, exposure pathway, and receptor are tabulated in Table 6-1. If a COC is not listed on the Tier 1 RBSLs, refer to USEPA soil screening levels or USEPA maximum contaminant levels for groundwater or consult with the NDDEQ.

A Tier 1 risk evaluation involves:

1. Determination of site COCs,

2. Selection of the maximum concentrations (RCs) in each media,

3. Selection of relevant Tier 1 RBSLs from Table 6-1, and

4. Comparison of the selected Tier 1 RBSLs with the RCs.

Based on the comparison of RCs with Tier 1 RBSL, the RP can select one of the following options:

1. If the COC concentrations are less than the Tier 1 RBSLs, and other conditions discussed in Section 6.6 are satisfied, request NDDEQ to issue site closure,

2. If the representative COC concentrations exceed the RBSLs, then:

• Adopt Tier 1 RBSLs as the cleanup levels and submit a Risk Management Plan (RMP) to meet the cleanup levels, or

• Perform a Tier 2 evaluation.

Upon completion of the Tier 1 evaluation, the RP must provide a Tier 1 Report to the NDDEQ. If the RP chooses to immediately perform a Tier 2 evaluation, both evaluations may be combined into a single report and submitted to the NDDEQ.

The Tier 1 risk evaluation is further discussed in Section 6.0.

2.2.5 Tier 2 Evaluation

A Tier 2 evaluation allows for the use of site-specific exposure and fate and transport parameters to calculate Tier 2 site-specific target levels (SSTLs).

In preparation for a Tier 2 evaluation, additional data may have to be collected and the EM revised as needed. Tier 2 SSTLs are calculated concentrations, based on site-specific data, such as the physical characteristics of the impacted media.

After the Tier 2 SSTLs have been calculated, they must be compared with representative COC concentrations for each complete exposure pathway. Depending on the comparison, the RP can make one of the following options:

1. If the RCs for each complete route of exposure are below the respective Tier 2 SSTLs, and other conditions discussed in Section 7.6 are satisfied, request site closure from the NDDEQ,

2. If the RCs for each complete ROE exceed the respective Tier 2 SSTLs, then:

NDRBCA Guidance Document Page 2-5 January 2023

• Adopt the Tier 2 SSTLs as cleanup levels and develop a RMP to manage these levels, or

• Develop a work plan for a Tier 3 evaluation.

Upon completion of the Tier 2 evaluation, the RP must provide a Tier 2 evaluation report to the NDDEQ. Note Tier 1 and Tier 2 evaluation may be included in the same report.

The Tier 2 risk evaluation is further discussed in Section 7.0.

2.2.6 Tier 3 Evaluation

A Tier 3 evaluation allows considerable flexibility in managing risk at a contaminated site.

Due to the many options available to the RP for the implementation of a Tier 3 evaluation, the NDDEQ requires that a work plan be submitted and approved prior to the implementation of a Tier 3 evaluation.

After the Tier 3 SSTLs are calculated, they must be compared to representative COC concentrations for each complete exposure pathway. Depending on the comparison, the RP can select either of the following two options:

1. If the RCs for each complete route of exposure are below the respective Tier 3 SSTLs, and other conditions discussed in Section 8.4 are satisfied, request site closure from the NDDEQ,

2. If the RCs for any complete ROE exceed the respective Tier 3 SSTLs, then adopt the Tier 3 SSTLs as cleanup levels and develop a RMP to meet these levels.

Upon completion of the Tier 3 evaluation, the RP must provide a Tier 3 risk evaluation report to the NDDEQ.

The Tier 3 risk evaluation is further discussed in Section 8.0.

2.2.7 Development and Implementation of Risk Management Plan (RMP)

The objective of all RMPs is to protect HH&E under current and reasonable future land use conditions. Typically, a RMP will be developed after the NDDEQ has approved media-specific cleanup levels under a Tier 1, Tier 2, or Tier 3 evaluation. The RMP must include details of the proposed remedial options, including environmental covenants, and the way the remedial options will be implemented and monitored. To the extent needed to protect HH&E, the plan may include:

1. Selection of remedial methods,

2. Proposed environmental covenants and justification for their use,

3. Estimate of the time needed to implement the RMP,

4. Monitoring plan to verify the effectiveness of the RMP,

5. Conditions that may require re-evaluation of the RMP, and

6. Steps that will be taken if the RMP is not effective.

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The RMP must then be implemented as written and approved. The data collected and the evaluation must be submitted to the NDDEQ. If the RMP is not progressing as planned and changes are needed, a proposal for modifying the plan must be submitted to the NDDEQ for approval.

RMP activities must continue until the NDDEQ determines that, based on site-specific data, cleanup goals have been met, specified land use restrictions are in place, and the residual impacts are stable or decreasing. The RMP must include a commitment to maintain the environmental covenant for as long as is necessary to ensure protection of HH&E, i.e., until residual concentrations exceed unrestricted use levels (RBTLs). NDDEQ will issue a site closure, based on the information available to NDDEQ at the time, that conditions at the site are protective of HH&E.

In the future, additional information may become available that may lead to the conclusion that the site poses an unacceptable risk to HH&E or that the land use has changed and is no longer compatible with the RMP that was implemented. In either of these or similar cases, the NDDEQ may rescind the site closure and require further action at the site.

Risk Management Plan is further discussed in Section 9.0.

2.3 RISK-BASED TARGET LEVELS WITHIN THE NDRBCA PROCESS

Under the NDRBCA process, any of the following risk-based levels may be selected as the cleanup levels.

1. Tier 1 RBSLs are a combination of (i) the Regional Screening Levels presented in USEPA (2022b) and (ii) concentrations developed by NDDEQ using conservative default exposure and fate and transport parameters that depend on the receptor, media, pathway, route of exposure, and domestic use or likely use of impacted or threatened groundwater. Refer to Appendix A for further details of the RBSLs. The use of Tier 1 RBSLs as clean up levels may require environmental covenants be placed on the site.

2. Tier 2 SSTLs are concentrations calculated using site-specific exposure and fate and transport parameters and the guidelines in this document. Tier 2 SSTLs differ from Tier 1 RBSLs in that the Tier 2 SSTLs are based on site-specific values, whereas the Tier 1 RBSLs use default fate and transport parameters. Typically, but not always, Tier 2 SSTLs will be higher than the corresponding Tier 1 RBSLs. Use of Tier 2 SSTLs as clean up levels may also require environmental covenants.

3. Tier 3 SSTLs are concentrations that are calculated using data collected at the site (i.e., site-specific exposure factors and fate and transport parameters) and the guidelines in this document. However, compared with Tier 2 SSTLs, Tier 3 SSTLs may be based on the application of fate and transport models and exposure

NDRBCA Guidance Document Page 2-7 January 2023 scenarios other than those used to calculate the Tier 1 RBSLs and Tier 2 SSTLs.

Use of Tier 3 SSTLs as cleanup levels may also require environmental covenants.

Table 2-1 compares the different tiers within the NDRBCA framework. However, as the analysis moves through the tiers, and if the target cleanup levels become lower, the RP does not have the option of using higher levels from the previous tier. The higher tier target levels are based on site-specific information and hence are expected to be more accurate representation of potential risks at the site. For large sites (several acres) different sections of the site may be managed using different cleanup levels and different land use restrictions.

2.4 RATIONALE AND CHARACTERISTICS OF TIERED APPROACH

Despite the differences among the three tiers, there is one very significant similarity: each tier will result in cleanup target levels that provide an acceptable level of protection to HH&E. Thus, the process provides considerable flexibility and a variety of options to manage site-specific risks. The RP working with the NDDEQ can thus select the optimal strategy.

As a site moves through the tiered process, the following can be anticipated:

• Higher tiers will require the collection of more site-specific data, which will increase data collection, data analysis, and labor costs.

• In general, the calculated Tier 2 SSTLs will be higher than the Tier 1 RBSLs and Tier 3 SSTLs will be higher than Tier 2 SSTLs. This is because lower tier target levels are calculated using more conservative assumptions than higher tier target levels. Thus, the cost of risk management activities at higher tiers should generally be lower.

• The need for, and the extent of, regulatory oversight and review will increase as the site moves from Tier 1 to Tier 2 and then to Tier 3.

• The level of uncertainty and conservatism will decrease as the evaluation progresses from Tier 1 to Tier 3 due to the availability of more site-specific data.

2.5 DOCUMENTATION OF THE NDRBCA PROCESS

To make decisions that protect HH&E, the NDRBCA process requires the collection and analysis of a considerable amount of data. In addition, a variety of stakeholders may be interested in the outcome of the NDRBCA process. Therefore, the process by which data is collected, analyzed, and documented and the way in which decisions are made must be as transparent and consistent across different sites as possible.

The method and format by which the RP reports data must be consistent across the state and unambiguous so that stakeholders can readily understand the:

• Data collected to quantify and analyze the problem,

• Nature and extent of the problem at a site, NDRBCA Guidance Document Page 2-8 January 2023

• Process used to collect the necessary data,

• Chronology of relevant environmental activities, and

• Demonstration that the actions taken are protective of HH&E under current and reasonably anticipated future use conditions.

In general, reports that may be required as a part of the NDRBCA process are listed below:

• Determination and Abatement of Imminent Threats,

• Site Characterization Report,

• Tier 1 and 2 Risk Evaluation Report (Tier 1, 2, or both),

• Tier 3 Work Plan,

• Tier 3 Risk Evaluation Report,

• Risk Management Plan, and

• Completion of Risk Management Plan.

To facilitate the documentation of these activities and to ensure consistency across sites, the NDDEQ has developed forms and tables that must be used. These are included in Appendix B.

NDRBCA Guidance Document January 2023 Page 3-1

3.0

SITE DISCOVERY AND MANAGEMENT OF IMMINENT THREATS

3.1 SITE DISCOVERY

The NDRBCA process starts when a contaminated site is discovered and continues until the NDDEQ issues site closure. Several events may trigger site-specific activities that may ultimately lead to the discovery of a contaminated site. These include but are not limited to:

• Observation of a sheen on or near a site, e.g., in utilities, surface water bodies, observation wells, on ground surface, etc.

• Unusual industrial operating conditions, e.g., sudden loss of product in tanks, erratic behavior of product dispensing equipment, etc.,

• Monitoring results from a leak detection system that indicate a leak,

• Underground storage tank removals

• Phase I or phase II property investigations

• Accidental release, e.g., during loading and unloading of chemicals, and

• Citizen complaints

The RP of the facility must first abate any ongoing release of contaminants, abate any imminent threats to HH&E and report to the NDDEQ the suspicion and/or confirmation of release. Upon confirmation of the release, a site characterization will be necessary to collect relevant data to perform a risk-based evaluation (also refer to Section 4.0).

3.2 REPORTING A RELEASE

In accordance with state and federal law, the intentional or unintentional release of hazardous materials must be reported to the state within 24 hours of the incident through the Unified Spill Reporting System online at https://www.spill.nd.gov/ or by calling 1-833-99SPILL (1- 833-997-7455).

Upon completion and documentation of the emergency response activities, additional data may have to be collected to perform a risk-based evaluation.

When a release is confirmed, the RP must take immediate steps to (i) prevent any additional release to the environment, and (ii) mitigate any fire, safety, or other immediate hazards to

HH&E.

NDRBCA Technical Guidance January 2023 Page 4-1

4.0

DATA NEEDS FOR TIERED RISK EVALUATION

4.1 INTRODUCTION

This section discusses the types of data required to implement Tier 1, 2, and 3 evaluations to be consistent with the NDRBCA process. Typically, data at contaminated sites is collected over a long period of time (several years) and often by different individuals, and at times on behalf of different entities. Therefore, it is important to compile the data and document it in a consistent and easy to understand manner (See Appendix B). This section also discusses the documentation of the data. It is not the intent of this section to present the methods and techniques that can be used to collect the data. Such information is readily available in the public domain.

Within the NDRBCA process, the primary objective is to collect data to enable the estimation of RBTLs protective of HH&E and use management to achieve the calculated RBTLs. Specifically, this includes the following categories of data:

• Site information,

• Description of the source and the COCs,

• Adjacent land use, land use restrictions, and receptor information,

• Analysis of current and future groundwater use,

• Characteristics of various media that may potentially be impacted by the release

(unsaturated zone, saturated zone, surface water bodies, sediments, buildings, and the indoor environment). Additionally, characteristics of aquatic and terrestrial organisms that may be potentially exposed to the COCs may be relevant,

• Delineation of impacts,

• Spatial and temporal distribution of COCs in each media impacted by the release,

• Remedial activities conducted at the site, and

• Other pertinent information (such as rainfall, infiltration rate, evapotranspiration, wind speed and direction)

The above data must be collected either using the current state of the practice or specific USEPA or NDDEQ guidance, if available.

The systematic compilation of above data (text, figures, and tables) is often referred to as the Conceptual Site Model (CSM). A CSM presents an overall understanding of the site.

It is best developed at the start of a project and refined/updated as additional data is collected and knowledge of the site increases. A CSM is an important communication tool for regulators, RPs, and other stakeholders.

Inherent to the CSM is the Exposure Model (EM) that identifies all the receptors who maybe exposed to the COC’s under current and reasonable future conditions, and the complete exposure pathways for each receptor. An exposure pathway describes how the COCs move from the source to the receptor, where contact between the COC and the receptor occurs, and types of exposure. Section 5.0 presents a discussion of the EM.

NDRBCA Technical Guidance January 2023 Page 4-2

Environmental data used in the NDRBCA process must be scientifically valid, defensible, and of known and documented quality. This can be achieved by using adequate quality assurance and quality control procedures throughout the entire process, i.e., from initial study planning through data collection and use. To the extent possible, data must be collected using USEPA or NDDEQ procedures.

4.2 SITE INFORMATION

The term “site” refers to the property where the spill or release occurred. Areas beyond the property boundary that may be impacted by the site COCs, must be incorporated in the CSM are referred to as “off-site” areas.

The following information must be included in the CSM:

• A site location map,

• A site map,

• Ground surface conditions,

• Location of utilities on and adjacent to the site,

• Location and characteristics of surface water bodies,

• On-site and adjacent off-site groundwater use, and

• Local hydrogeology and aquifer characteristics.

A brief discussion of each of the above items is presented below.

4.2.1 Site Location Map

A site location map should be prepared using United States Geological Survey (USGS) 7½ minute topographic maps as a base. The site location should be centered and clearly marked on the topographic map. Contour lines on the topographic map must be legible and the map must include a scale bar and the north arrow.

4.2.2 Site Map

A detailed map(s) of the site should show:

• Site (property) boundaries,

• Layout of past and current relevant site features such as containment or storage systems; process areas; transportation and delivery distribution systems; waste handling and storage areas, piping runs; sumps; paved and unpaved areas; and buildings,

• Locations of area(s) of release (source area),

• Locations of on-site and off-site monitoring points (soil borings, confirmatory soil sampling locations, soil vapor points, groundwater monitoring wells, etc.),

• Locations of water wells (public and private) within a quarter mile of the source,

• Location of surface water features within at least 1,000 ft of the source,

• Ecological sensitive features within a 1,000 ft of the source,

• Location of soil excavation, if any, and

NDRBCA Technical Guidance January 2023 Page 4-3

• Location of infrastructure associated with any other remedial system (e.g., soil vapor extraction, etc.)

• Source water protection areas

4.2.3 Ground Surface Conditions

The site map should identify the portion of the affected area (on-site and off-site) that is paved, unpaved or landscaped. The type, extent, and general condition of the pavement should also be noted. The unpaved areas (for example, vegetated, gravel, or bare soil) should be described. The direction in which the surface slopes and any relevant topographic features (for example, swales, drainage, or detention ponds) should be noted.

4.2.4 Location of On and Adjacent Off-site Utilities

Knowledge of underground utilities are important because contaminated groundwater and vapors can flow preferentially into and through underground utility lines and conduits, utility workers are potential receptors, and COCs may affect the integrity of the utilities.

Therefore, an assessment of potential and actual migration and impacts of COCs to underground utilities must be performed. Utilities include buried cables, electrical and telephone lines, sanitary and storm sewers, and water and natural gas lines. A combination of site observations, knowledge of buried utilities, and discussions with utility representatives (or use of a one-call system) and the site owner should be used to determine the location of site utilities. The following must be performed:

• Use field instrumentation to measure the vapor concentrations in underground manholes at sites where COCs are volatile. If explosive conditions are suspected or encountered, immediately inform the local fire department and the North Unified Spill Reporting System at 1.833.99SPILL (1.833.997.7455) or reported online at https://www.spill.nd.gov/.

• Locate all underground utility lines and conduits within the area of known or suspected soil and groundwater impact, both on- and off-site, where the release may have migrated or may migrate in the future.

The following information may be useful in the analysis:

• Direction of water flow in utility lines (potable water, storm water, and sewage).

• Location of the utility lines and conduits on a base map that shows the extent and thickness of contamination in soil and groundwater.

• Depth of the utility lines and conduits relative to the depth of groundwater.

Seasonal fluctuations of groundwater levels must be considered. A cross-sectional diagram that illustrates the depth to groundwater, range of fluctuations, and the locations and depths of the various utility lines and conduits is recommended.

• Types of materials used for utility lines and conduits - for example, polyvinyl chloride (PVC), terra cotta, concrete, or steel - and the type of backfill around the utilities (sand, native soil).

• Any historical work completed on any of the utilities and if any contamination-

NDRBCA Technical Guidance January 2023 Page 4-4 related issues were identified at the time the work was performed.

Refer to Appendix G for further information regarding utility line exposure to contaminants of concern.

4.2.5 On-site Groundwater Use

Current and former site owners and operators may be interviewed to determine whether any water use wells were located on site. Such wells maybe identified based on a search of local, state, and federal records and databases and/or windshield or door-to-door surveys, as appropriate.

To the extent that such information is available, well construction details for all wells is useful. Relevant construction details include the total depth of the well, casing depth, screened or open interval, static and/or pumping level, and the use of water from the well.

If available, average well pumping rates and drawdown information also should be compiled.

If a water use well is currently not in use or not likely to be used in the future, it should be closed in accordance with well abandonment guidance.

4.2.6 Local Hydrogeology and Aquifer Characteristics

Local hydrogeology, soil types and aquifer characteristics should be evaluated to determine the type and depth of aquifers in the area and whether they are confined, semi-confined or unconfined. This information can be found in published literature such as USGS resources, United States Department of Agriculture (USDA) soil surveys, North Dakota Department of Water Resources County Groundwater Studies, and reports for any investigations conducted at adjacent or nearby release sites.

The review discussed above should also identify surface water bodies (lakes, rivers streams, wetlands, and springs) located within 1,000 ft of the source that could be affected by a release at the site.

4.3 DESCRIPTION OF THE SOURCE AND COCs

Knowledge about the nature, location and magnitude of a release(s) is necessary to identify the:

• Soil and groundwater source(s) at the site,

• COCs,

• Methods used to analyze the samples,

• Horizontal and vertical extent of soil and groundwater contamination.

The RP must collect as much of the following information as is available for each release that has occurred at the site:

NDRBCA Technical Guidance January 2023 Page 4-5

• History of site activities related to the release,

• Location(s) and date(s) of spill(s) or release(s),

• Quantity of the release(s),

• Product(s) or chemical(s) released, and

• Interim response or corrective action measure(s) taken with respect to each release.

Release-related information can be obtained from a variety of sources, including:

• Review of historical aerial photographs or Sanborn fire insurance maps,

• Review of waste inventory records and products manufactured,

• Interviews with past and current on-site employees,

• Review of the NDDEQ and USEPA files,

• Review of permits, and

• Review of site related administrative or consent orders, if any.

4.3.1 History of Activities at the Site

At many contaminated sites, site investigations, monitoring events, system (such as tanks, pipelines, or lagoons) removal activities, or remediation activities may have taken place over an extended period. Therefore, a key step is to develop a comprehensive chronology of historical events related to chemical impacts. A chronology will help create a complete picture of the site activities and identify COC and data gaps, if any. The chronology should include information such as the dates, descriptions, and results of:

• Installation, removal or upgrade of containment or waste systems,

• Remedial activities such as excavation and disposal of contaminated soil, removal of free product, groundwater, and soil vapor etc.,

• Drilling, sampling, and gauging of monitoring points,

• Collection of environmental media samples,

• Institutional controls, and

• Previous regulatory interactions

Remedial activities may have removed all or part of the COCs released at a site. Soil and groundwater data collected prior to the completion of these activities may not be representative of current conditions and should not be used in the calculation of current exposure and risk.