36C26318Q0548-005.pdf

TIER 1 GUIDANCE

Site Assessment of

Leaking Underground Storage Tanks (LUST) Using

Risk-Based Corrective Action (RBCA)

Underground Storage Tank Section

Land Quality Bureau

Iowa Department of Natural Resources

502 East Ninth Street

Des Moines, IA 50319-0034

(515) 725-8200 www.iowadnr.gov/ust

January 2018 http://www.iowadnr.gov/ust

Table of Contents

RISK-BASED CORRECTIVE ACTION OVERVIEW

General Information

Tier 1 Site Assessment

Two Classification Levels for Tier 1 Assessment: Pathway(s) Complete or No Action Required . 5

Tier 2 Site Cleanup Report

Tier 3 Assessment

No Action Required Site Classification

No Further Action Certificate

Conditions Requiring a Tier 2 Site Cleanup Report

Tier 1 Flowchart

GENERAL INFORMATION

Statutory Authority

Financial Responsibility

Iowa Comprehensive Petroleum Underground Storage Tank Fund Program

Budget Approvals

Tier 1 Report Form

Tier 1 Software

Report Preparation

Review Process

Report Submittal

Report Submittal Extensions

Chemicals of Concern

OA1 and OA2 Total Extractable Hydrocarbons Methyl-tertiary butyl ether (MtBE) Other Chemicals of Concern Soil Gas Analysis Certified Laboratory Required Laboratory Data Sheets Quality Control/Quality Assurance Procedures Iowa Tier 1 Level Look-Up Table Soil Gas Target Levels

TIER 1 PATHWAY EVALUATION

General Tier 1 Procedure

Pathway Assessment

Receptor Evaluation

Source

Pathway Clearance

Corrective Action Response

TIER 1 PATHWAY-SPECIFIC GUIDANCE

Groundwater Ingestion Pathway

Soil Leaching to Groundwater Pathway

Groundwater Vapor to Enclosed Space Pathway

Soil Vapor to Enclosed Space Pathway

Groundwater to Water Line Pathway

Soil to Water Line Pathway

Surface Water Pathway

SUMMARY PAGES

Cover Page

Site Data Summary

Pathway Evaluation Summary

Corrective Action Documentation – optional

SITE CHRONOLOGY AND CURRENT CONDITIONS

Site Chronology

Current Site Conditions

SAMPLING REQUIREMENTS

General Information

Where to Sample

Monitoring Well Placement Soil Sample Collection Possible Sample Location(s) Possible Sampling Scenarios

Drilling and Well Construction

Exploratory Methods Monitoring Well Construction Design Monitoring Well Construction Permit Boring Depth for Sampling Boring Depth for Screening Soil Gas Sampling (Optional) Collecting a Soil Gas Sample Checking the Static Water Levels

Field Screening

Classification of Soils

Elevation Measurements

Groundwater

Sampling Hydraulic Conductivity Protected Groundwater Source Groundwater Flow Direction Total Dissolved Solids

RECEPTOR SURVEY

Wells

Well Search

Enclosed Spaces and Conduits

Explosive Vapor Survey

Explosive Vapor Survey Procedures

Surface Waterbody

TIER 1 CORRECTIVE ACTION RESPONSE

No Action Required Site Classification

No Further Action Certificate

Compliance Monitoring and Confirmation Sampling

Institutional Controls

City and County Ordinances

Environmental Covenant

Modification or Termination of Institutional Controls

Replacement or Relocation of Water Lines

Soil Excavation as Corrective Action

Excavation Reporting

Expedited Corrective Action

REQUIREMENTS FOR REPORT MAPS AND APPENDICES

APPENDICES

Appendix A – Quick Links

Appendix B – Abbreviations

Appendix C – UST Section Staff Contact Information

Appendix D – Field Office Contact Information

Appendix E – Map of Iowa Depth to Bedrock 50’ Foot

Appendix F – Blank Forms

Appendix G – Flowcharts

What To Do When Contamination is Suspected Groundwater Ingestion Pathway Soil Leaching Pathway Groundwater Vapor to Enclosed Space Pathway Soil Vapor to Enclosed Space Pathway Groundwater to Water Line Pathway Soil to Water Line Pathway Surface Water Pathway

Appendix H – Revision Dates

RISK-BASED CORRECTIVE ACTION OVERVIEW

General Information The Iowa Department of Natural Resources (DNR) Underground Storage Tank (UST)

Section utilizes the Risk-Based corrective action (RBCA), which assesses the risk(s) posed by petroleum contamination using site-specific conditions and a tiered approach to protect human health and the environment. Based on the results of the tiered assessment, corrective action can then be used to minimize or remove risk(s). Corrective action options can include: reducing contamination through active or passive methods, using technological or institutional controls, or monitoring.

Tier 1 Site Assessment A Tier 1 Site Assessment (Tier 1) uses limited site data to determine whether a site poses an unreasonable risk to public health, safety, and the environment. A Tier 1 assessment generally includes: conducting a field investigation to determine the maximum concentrations of chemicals of concern in soil and groundwater associated with the petroleum release, surveying the surrounding area for receptors and comparing maximum contaminant concentrations to the Tier 1 Look-up Table to determine which pathways are complete. The Tier 1 levels are derived from models using conservative assumptions to predict contaminant movement and exposure to receptors.

A Tier 1 Assessment assumes the worst-case scenario, by evaluating whether actual or potential receptors could be exposed to chemicals of concern through soil and groundwater pathways. The location with the maximum concentrations is assumed to be the point of exposure, i.e., the source.

Additional assessment after the Tier 1 assessment is complete depends on maximum concentrations identified. For example, if the maximum concentrations do not exceed the

Tier 1 levels for a pathway, further assessment of that pathway may not be required. If a maximum concentration does exceed a Tier 1 level, additional assessment or corrective action may be required, including but not limited to conducting a Tier 2, performing soil excavation, or implementing an institutional or technical control.

Two Classification Levels for Tier 1 Assessment: Pathway(s) Complete or No Action Required

A pathway(s) is a transport mechanism by which chemicals of concern exceeding a Tier 1 level may reach a receptor or a location of a potential receptor. A single pathway may have multiple classifications based on actual or potential receptor evaluations. Separate classification criteria may apply to actual and potential receptors for any pathway. Based on the DNR’s review, a site can complete a pathway or obtain a No Action Required classification.

The DNR has 90 days to review a report for accuracy and completeness. Incomplete reports, including reports not submitted in the format required by the DNR, will be rejected.

Tier 2 Site Cleanup Report A Tier 2 Site Cleanup Report (Tier 2) is conducted on a site not classified No Action

Required at Tier 1 or if a pathway(s) and chemical group(s) does not meet the no action required requirements. The objective of a Tier 2 site assessment is to collect site-specific data and, with the use of Tier 2 modeling, to determine which actual or potential receptor(s) could be impacted by chemical(s) of concern and what concentration(s) at the source are predicted to achieve protection of the receptor(s). If a Tier 2 site assessment is conducted without doing a Tier 1 assessment first, Tier 1 requirements must be included in the Tier 2.

Further, a Tier 2 must be completed when free product is identified on-site.

Tier 3 Assessment The purpose of Tier 3 Assessment (Tier 3) is to assess the risk of exposure to the chemicals of concern using other chemical fate and transport models or alternative assessment methods. A Tier 3 assessment may provide additional risk assessment data beyond a Tier 2. See Tier 2 Guidance for additional information.

No Action Required Site Classification To obtain a no action required classification, all pathways at a site must meet the individual pathway criteria or not exceed Tier 1 levels for any pathway. If pathway conditions present an unreasonable risk to human health, safety, or the environment, the pathway shall be further assessed consistent with the risk-based corrective action provisions. However, if a pathway meets the criteria for actual and potential receptors for the pathway, then it will be classified No Action Required.

If a Tier 1 level is exceeded for any pathway, a no action required site classification may be obtained if acceptable corrective actions are implemented. Corrective Action Response options permitted for pathways failing the Tier 1 analysis are identified within this guidance.

If the corrective actions cannot be implemented, a Tier 2 must be completed to evaluate those pathways not cleared at Tier 1.

If a Tier 1 level(s) is not exceeded for an individual pathway, the corresponding part of the

Tier 3 is not depicted.

receptor survey specific to that pathway does not need to be conducted. For example, if the maximum concentrations of chemicals of concern in groundwater and soil are below the most restrictive Tier 1 levels for the groundwater to water line pathway and soil to water line pathway, then a survey for water lines within 200 feet of the source is not required. Certain parts of the receptor survey must be conducted in accordance with instructions in the

Receptor Survey regardless of the actual contaminant concentrations.

A no action required site classification may be proposed upon completion of Tier 1 if all the criteria for pathway clearance have been met for every pathway. Note, all corrective actions necessary to satisfy the criteria for pathway clearance must be conducted prior to submittal of a Tier 1 report recommending a no action required site classification. The DNR must be informed if these corrective actions require more than 90 days to complete. All documentation which supports the corrective actions must be submitted as attachments to the Tier 1 report. If the corrective actions cannot be implemented, a Tier 2 must be completed to evaluate those pathways not cleared at Tier 1.

No Further Action Certificate When the no action required site classification has been accepted for a Tier 1 Report, the

DNR will issue a no further action (NFA) certificate. The DNR will issue a NFA certificate to an owner or operator of a site from which the release has occurred, the current property owner, or other responsible party who has taken corrective action warranting classification of the site as no action required.

To obtain an NFA certificate, the DNR may request any of the following:

• Completed well plugging forms – All abandoned wells and borings with access to groundwater must be plugged according to 567—39 using DNR Form 542-1226.

Contact the DNR’s Water Supply Section for additional information.

• Proof of institutional controls (for example, but not limited to filed and stamped deed restrictions, certification letters, and environmental covenants)

• Copies of local ordinances or regulations which prevent placement of wells or use of groundwater

• Copies of notices to the DNR's Water Supply Section

• Copies of notices to county authorities which issue private water supply construction permits

• Report of soil excavation activities

• Report of water line replacement or relocation

• Copies of notices to utility companies which supply water to the area of concern

Conditions Requiring a Tier 2 Site Cleanup Report

1. Pathway Complete

If a pathway is complete at Tier 1, a Tier 2 must be conducted.

2. Free Product

If free phase product is encountered on-site, the DNR must be notified within 24 hours.

https://www.legis.iowa.gov/DOCS/ACO/IAC/LINC/05-01-2013.Chapter.567.39.pdf http://www.iowadnr.gov/portals/idnr/uploads/forms/5421226.pdf http://www.iowadnr.gov/InsideDNR/RegulatoryWater/WaterSupplyEngineering.aspx

The UST and Field Office staff assigned to each region of the state and their direct phone numbers are provided in Appendix A. Free product removal must be conducted in accordance with 567—135.7(5) and reported to the DNR on the attached IDNR Forms

542-1424 and 542-1425. If free product is present, the Tier 1 guidance document is no longer applicable for site evaluation. A Tier 2 SCR must be completed in accordance with the requirements in the Tier 2 SCR guidance document.

3. Explosive Vapor Levels

If potentially explosive levels (10% LEL) are detected when conducting the explosive vapor survey, contact local emergency services and report to the appropriate DNR Field Office. The groundwater professional must notify the responsible party or party contracting the site investigation to report the contamination to the DNR in accordance with IAC 567—131. The appropriate party must begin immediate response and abatement procedures in accordance with IAC 567—135.7 and IAC 567—133, proceed with the Tier 2 assessment, and evaluate the enclosed space as an actual receptor.

4. Shallow Bedrock

Prior to drilling and to assist in planning, the groundwater professional should determine the potential to encounter bedrock before groundwater. These potential areas could include (1) areas where karst features or outcrops exist within one mile of the site and

(2) areas where bedrock is less than 50 feet from the surface as illustrated in Appendix

B. The purpose of this determination is to prevent drilling through contaminated subsurface areas and creating a preferential pathway to a bedrock aquifer.

If the first encountered groundwater is above the bedrock with sufficient separation and aquifer characteristics to establish that it acts as a granular aquifer as provided in 567—

135.10(3)“a”, a Tier 1 assessment must be conducted as provided in this guidance.

If bedrock is encountered before groundwater, a Tier 2 SCR must be completed in accordance with the requirements in the Tier 2 SCR guidance document and special bedrock procedures in 567—135.10(3).

If the first encountered groundwater is above bedrock but near the bedrock surface, or fluctuates above and below bedrock, the groundwater professional should evaluate the sub-surface geology and aquifer characteristics to determine the potential for creating a preferential pathway. If it is determined the aquifer shows extraordinary variations or inconsistencies in groundwater flow, groundwater elevations across the site, hydraulic conductivities, or total dissolved solid concentrations among monitoring wells, a Tier 2 using special bedrock procedures must be conducted.

https://www.legis.iowa.gov/DOCS/ACO/IAC/LINC/11-27-2013.Chapter.567.135.pdf http://www.iowadnr.gov/portals/idnr/uploads/forms/5421424.pdf?amp%3Btabid=688 http://www.iowadnr.gov/Portals/idnr/uploads/forms/5421425.pdf http://www.iowadnr.gov/InsideDNR/DNRStaffOffices/EnvironmentalFieldOffices.aspx https://www.legis.iowa.gov/DOCS/ACO/IAC/LINC/05-01-2013.Chapter.567.131.pdf https://www.legis.iowa.gov/docs/ACO/chapter/567.135.pdf https://www.legis.iowa.gov/DOCS/ACO/IAC/LINC/05-01-2013.Chapter.567.133.pdf https://www.legis.iowa.gov/DOCS/ACO/IAC/LINC/11-27-2013.Chapter.567.135.pdf

Tier 1 Flowchart

GENERAL INFORMATION

Statutory Authority The Iowa Code chapter 455B and Iowa Administrative Code chapters 134, 135 authorize the DNR to regulate underground storage tanks.

Financial Responsibility Owners and operators of active underground storage tank systems are required to maintain financial responsibility, or insurance. Owners and operators should contact their insurance carrier to begin the claim process when a release has been identified.

Iowa Comprehensive Petroleum Underground Storage Tank Fund Program Several funding mechanisms exist under the Iowa Comprehensive Petroleum Storage Tank

Fund Program to assist eligible responsible party(s) and property owner(s) with assessment and corrective action activities. Eligibility is determined on a site-specific, fund- specific basis. The DNR does not manage this program nor determine fund eligibility.

Please contact the Fund Administrator at AON Risk Services for additional information.

Budget Approvals An UST owner and operator eligible to receive state funds covering site investigation expenses must submit the Tier 1 preparation budget prior to initiating work. Failure to receive budget approval from the Fund Administrator prior to starting work at the site may result in a loss of state benefit eligibility.

http://search.legis.state.ia.us/nxt/gateway.dll/ic?f=templates&fn=default.htm https://www.legis.iowa.gov/IowaLaw/AdminCode/agencyDocs.aspx

Send budget proposals to:

AON Risk Services

2700 Westown Pkwy Ste 320

West Des Moines IA 50266

(515) 225-9263

Or

(515) 440-7016

Tier 1 Report Form When a Tier 1 assessment is conducted, findings must be reported in the Tier 1 Report form. A blank copy of the report can be found at the DNR UST webpage.

Tier 1 Software The Tier 1 software is useful for identify whether a pathway has passed or failed and what actions are required or options available at each pathway. It is not required to complete a

Tier 1 assessment; yet, the software may help determine the required action(s) for a receptor in a pathway or corrective action options.

The RBCA software can be obtained at the DNR UST webpage.

A copy of the Tier 1 Software Guidance is available at the DNR UST webpage.

Report Preparation The Tier 1 report cover page must be signed by the responsible party and a certified groundwater professional. It is the responsibility of the owner or operator to ensure the groundwater professional prepares a report appropriate for the conditions at the site. All groundwater and soil data obtained during the Tier 1 field assessment must be collected by or under the supervision of an Iowa certified groundwater professional. A list of certified

Iowa groundwater professionals can be found at the DNR UST webpage.

To the extent practicable, during the preparation of the Tier 1 report, use generally available hydrologic, geologic, topographic, and geographic information to minimize site-specific testing. In many instances, a space is provided in the Tier 1 report form to record a response. A response must be provided for all questions unless directed otherwise in the instructions. Please try to limit the response to the space provided. Yet, if extra space is required, reference it as an attachment.

The Tier 1 Report must contain all the information requested; see Requirements for Report

Maps and Appendices. A checklist of Tier 1 report components is included to assist with compilation. Items labeled “optional” may not be necessary. The groundwater professional is responsible for determining what site-specific information must be included to produce a complete report.

Review Process Upon receipt of the Tier 1 report, the DNR will review the report for completeness, http://www.iowadnr.gov/InsideDNR/RegulatoryLand/UndergroundStorageTanks/LeakingUndergroundTanks/LUSTSiteAssessment/Tier1.aspx http://www.iowadnr.gov/InsideDNR/RegulatoryLand/UndergroundStorageTanks/LeakingUndergroundTanks/LUSTSiteAssessment.aspx http://www.iowadnr.gov/Portals/idnr/uploads/ust/tier1softwareusersmanual.pdf http://www.iowadnr.gov/portals/idnr/uploads/ust/gwplistname.pdf?amp%3Btabid=670 accuracy, and compliance with the DNR’s rules. Incomplete Tier 1 reports and Tier 1 reports not submitted in the format required by this guidance and 567—135.9(11) will be rejected.

The Tier 1 report and the groundwater professional’s proposed risk classification for the site shall be considered accepted unless with 90 days of receipt of the report, the DNR identifies material information in the report that is inaccurate or incomplete in accordance with 567—135.9(11).

If during the course of the Tier 1 report phase the groundwater professional determines a

Tier 2 report rather than a Tier 1 report is necessary, a separate Tier 1 report should not be submitted and will not be reviewed; rather, the Tier 1 findings should be incorporated into the Tier 2 report.

Report Submittal A hard copy of the Tier 1 report must be submitted to the DNR within 90 calendar days from the date the petroleum release was confirmed and related Tier 1 software analysis should be sent via email.

Send a copy of the completed Tier 1 report to:

Iowa Department of Natural Resources

LUST Coordinator

502 E 9th St

Des Moines IA 50319

Send Tier 1 Software analysis: UST.RBCAsoftwareMTBE@dnr.iowa.gov

If the Underground Storage Tank Fund is involved, send a copy to:

AON Risk Services

2700 Westown Pkwy Ste 320

West Des Moines IA 50266

The six-character LUST number needs to be included in all report submittals and correspondence regarding a Leaking Underground Storage Tank (LUST).

If a Tier 2 is prepared instead of a Tier 1 report, the DNR must be notified in writing prior to the expiration of the Tier 1 report submission deadline.

Report Submittal Extensions Timing for submittal of the report starts when the letter requesting the Tier 1 evaluation is received by the responsible party. If, during the Tier 1 evaluation phase of the project, the

Tier 1 will not be submitted within the allotted timeframe or it is determined a Tier 2 evaluation is more appropriate, then the owner or operator or certified groundwater professional must request a schedule extension, in writing in the report submittal schedule before the Tier 1 is due.

mailto:UST.RBCAsoftwareMTBE@dnr.iowa.gov

Schedule extension requests must be signed or co-signed by the responsible party. The request must include a reason for the time extension. The DNR will respond to the schedule request. Except under very extreme situations, only one schedule extension request will be accepted for a site. If additional schedule extensions are necessary, the certified groundwater professional may submit a letter signed or co-signed by the RP, explaining in detail the reason why the report cannot be submitted as scheduled.

Subsequent requests may not be granted. The DNR may use this information to evaluate whether to take legal or other actions. All correspondence regarding time request extensions will be made part of the site file.

Chemicals of Concern

OA1 and OA2 A soil and groundwater sample(s) collected from a release(s) of a petroleum-regulated substance(s) must be analyzed for volatile petroleum hydrocarbons—benzene, toluene, ethylbenzene, and xylenes—also known as Iowa Method OA-1.

Total Extractable Hydrocarbons If the release is suspected to include any petroleum-regulated substance other than gasoline or gasoline blends, or if the source of the release is unknown, a soil and groundwater sample(s) must also be tested for semi-volatile petroleum compounds—all grades of diesel fuel, fuel oil, kerosene oil, and mineral spirits—known as Total Extractable

Hydrocarbons (TEH) or Iowa Method OA-2. A copy of Iowa Method OA-1 and OA-2 are available from DNR UST webpage.

Methyl-tertiary butyl ether (MtBE) A soil or groundwater sample(s) collected during any phase of the RBCA evaluation process must be tested for methyl-tertiary butyl ether (MtBE) pursuant to 567—135.19. The

MtBE analyses must be performed regardless of what type of petroleum release (i.e., gasoline, diesel, fuel oil, waste oil, motor oil, hydraulic fluid, jet fuel, kerosene, and mineral spirits) is under investigation.

MtBE analysis does not need to be conducted on samples collected in association with tank closures or site checks unless the site check samples are used in Tier 1 or Tier 2 evaluations.

To assure reliable and accurate analytical results, MtBE analysis will be conducted by Gas

Chromatography/Mass Spectrometry (GC/MS) using the GC/MS version of OA-1, "Method for Determination of Volatile Petroleum Hydrocarbons (gasoline)," revision 7/27/93, or US

Environmental Protection Agency Method 8260B, SW-846, "Test Methods for Evaluating

Solid waste," Third Edition. Using gas chromatography as the sole analytical method will likely result in a false positive (or negative) and should be reported to the DNR.

Laboratories analyzing for MtBE must be able to meet a detection level of 15 g/L (ppb) for http://www.iowadnr.gov/Environmental-Protection/Land-Quality/Underground-Storage-Tanks/Leaking-Underground-Tanks/Certified-Labs-Methods water samples and 15 g/kg (ppm) for soil samples. MtBE is considered not present if reported as < 15 ppb. MtBE is considered present if 1) the lab reports it as a positive quantified level below 15 ppb (e.g., 12 ppb) by using a detection level below 15 ppb, or 2) if the laboratory is reporting at a higher detection level (e.g.<16 ppb, <50 ppb, <200 ppb).

Under these conditions, continued monitoring/ testing for MtBE is required.

Laboratories performing the analyses must run standards for MtBE on a routine basis, and standards for other possible compounds like ethyl tertiary-butyl ether (ETBE), tertiary-amyl methyl ether (TAME), diisopropyl ether (DIPE), and tertiary-butyl alcohol (TBA) to be certain of their identification should they be detected.

MtBE monitoring results must be reported to the DNR on the MtBE Sampling Results (DNR

Form 542-1394).

Other Chemicals of Concern If other chemicals of concern are identified, please contact DNR to determine whether additional sampling or assessment is necessary.

Soil Gas Analysis The National Institute for Occupational Safety and Health (NIOSH) Method 1501, or a DNR-approved equivalent method, shall be used for the analysis of soil gas for benzene and toluene vapors. NIOSH Method 1501 is published in the NIOSH Manual of Analytical

Methods, 1994.

If an alternative soil gas analytical method is to be used, a proposal must be submitted to the DNR prior to its use. The proposal must contain a justification for the use of an alternative method and a copy of the method including information on sample preparation, calibration, quality control, equipment, and materials used in sample extraction and analysis and calculations used to determine concentrations of chemicals of concern.

As of September 1, 1998, soil gas samples from LUST sites must be analyzed by a laboratory which has met the certification criteria for soil gas analysis through the State

Hygienic Laboratory (SHL).

Certified Laboratory Required To analyze a soil and water sample(s) related to a release of a petroleum-regulated substance a laboratory must be certified pursuant to 567—83, 135.16. A list of certified laboratories may be obtained from the DNR UST webpage.

Laboratory Data Sheets Provide a copy of all laboratory data sheets, including those for Total Dissolved Solids analyses (if applicable.), Chain of Custody forms, chromatograms, and associated quantitative reports for the waste oil, diesel, and gasoline standards used by the laboratory.

The laboratory analytical report must state whether the sample tested matches the laboratory standard for waste oil, diesel, or gasoline. Additionally, chromatograms for soil http://www.iowadnr.gov/Portals/idnr/uploads/forms/5421394.pdf http://www.iowadnr.gov/Portals/idnr/uploads/forms/5421394.pdf http://www.iowadnr.gov/Portals/idnr/uploads/forms/5421394.pdf http://www.shl.uiowa.edu/labcert/idnr/index.xml http://www.shl.uiowa.edu/labcert/idnr/index.xml http://www.shl.uiowa.edu/labcert/idnr/index.xml https://www.legis.iowa.gov/DOCS/ACO/IAC/LINC/05-01-2013.Chapter.567.83.pdf http://www.shl.uiowa.edu/labcert/idnr/index.xml and groundwater samples with the maximum concentrations of BTEX and TEH—D, —WO must be submitted. Chromatograms for all other sample analyses should be maintained by the laboratory and available upon request by the DNR.

Quality Control/Quality Assurance Procedures The quality control/quality assurance (QC/QA) procedures used during the site investigation must be at least as stringent as those contained in DNR's LUST Quality Assurance Plan. A copy of the DNR's LUST Quality Assurance Plan may be found at the DNR UST webpage.

See also the DNR wide QC/QA procedures as an additional resource. The groundwater professional must provide DNR a copy of the QC/QA plan designed for the site, field notes, and chain of custody forms on request.

http://www.iowadnr.gov/portals/idnr/uploads/ust/qaqcplan.pdf https://intranet.iowadnr.gov/filemgmt_data/content/qualmgtpract.pdf

Iowa Tier 1 Level Look-Up Table

Exposure Pathway

Receptor

Group 1 Group 2

Benzene Toluene Ethylbenzene Xylenes Diesel* Waste

Oil

Groundwater

(g/L)

Groundwater Ingestion

Actual 5 1,000 700 10,000 1,200 400

Potential 290 7,300 3,700 73,000 75,000 40,000

Groundwater Vapor to Enclosed

Space

All 1,540 20,190 46,000 NA 2,200,00

NA

Groundwater to Water Line

PVC or Gasketed

Mains 7,500 6,250 40,000 48,000 75,000 40,000

PVC or Gasketed Service Lines

3,750 3,120 20,000 24,000 75,000 40,000

PE/PB/AC

Mains or Service Lines

200 3,120 3,400 19,000 75,000 40,000

Surface Water

All 290 1,000 3,700 73,000 75,000 40,000

Soil (mg/kg)

Soil Leaching to

Groundwater All 0.54 42 15 NA 3,800 NA

Soil Vapor to Enclosed

Space All 1.16 48 79 NA 47,500 NA

Soil to Water Line

All 2.0 3.2 45 52 10,500 NA

NA: Not applicable. There are no limits for the chemical for the pathway, because for groundwater pathways the concentration for the designated risk would be greater than the solubility of the pure chemical in water, and for soil pathways the concentration for the designated risk would be greater than the soil concentration if pure chemical were present in the soil.

TEH: Total Extractable Hydrocarbons. The TEH value is based on risks from naphthalene, benzo(a)pyrene, benz(a)anthracene, and chrysene.

Diesel*: Standards in the Diesel column apply to all low volatile petroleum hydrocarbons except waste oil.

Assumptions Used for Iowa Tier 1 Look-Up Table Generation:

1. Groundwater ingestion pathway. The maximum contaminant levels (MCLs) were used for Group 1 chemicals. The target risk for carcinogens for actual receptors is 10-6 and for potential receptors is 10-4. A hazard quotient of one, and residential exposure and building parameters are assumed.

2. Groundwater vapor to enclosed space pathway. Residential exposure and residential building parameters are assumed; no inhalation reference dose is used for benzene; the capillary fringe is assumed to be the source of groundwater vapor; and the hazard quotient is 1 and target risk for carcinogens is 1x10-4.

3. Groundwater to water line. This pathway uses the same assumptions as the groundwater ingestion pathway for potential receptors, including a target risk for carcinogens of 10-4.

4. Surface water. This pathway uses the same assumptions as the groundwater ingestion pathway for potential receptors, including a target risk for carcinogens of 10-4, except for toluene which has a chronic level for aquatic life of 1,000 as in the definition for surface water criteria in 567—135.2(455B).

5. Soil leaching to groundwater. This pathway assumes the groundwater will be protected to the same levels as the groundwater ingestion pathway for potential receptors, using residential exposure and a target risk for carcinogens of 10-4.

6. Soil vapor to enclosed space pathway. The target risk for carcinogens is 1x10-4; the hazard quotient is 1; no inhalation reference dose is used for benzene; residential exposure factors are assumed; and the average of the residential and nonresidential building parameters is assumed.

7. Soil to water line pathway. This pathway uses the soil leaching to groundwater model with nonresidential exposure and a target risk for carcinogens of 10-4.

In addition to these assumptions, the equations and parameter values used to generate the Iowa Tier 1 Look-Up Table are described in 567—135 Appendix A.

Soil Gas Target Levels

Exposure

Pathway

Unit of

Equivalents

Chemicals of Concern

Benzene Toluene

Soil Vapor to

Enclosed Space

Soil Gas (g/m3) 600,000 9,250,000

(ppm) 190 2,500

TIER 1 PATHWAY EVALUATION

General Tier 1 Procedure The objective of the Tier 1 field investigation is to identify maximum concentrations of chemicals of concern associated with a release(s) originating on a site. Further, the Tier 1 assessment requires a determination of whether a pathway is complete, an evaluation of actual or potential receptors, a determination of whether conditions are satisfied for obtaining no further action clearance for individual pathways or for obtaining a complete site classification of no action required, and, if necessary, a corrective action response.

Placement and depth of borings and monitoring wells must be sufficient to determine the vertical extent of soil contamination, an adequate description of site stratigraphy, and a reliable determination of groundwater flow direction. At Tier 1, the point of exposure for receptors and the point of compliance is the location of the presumed source of a release.

The presumed source of the release is the location(s) of soil and groundwater showing the maximum concentration(s) of chemicals of concern.

Pathway Assessment A pathway is considered complete if a chemical of concern has a route by which it may reach an actual or potential receptor. The pathways to be evaluated at Tier 1 are:

Groundwater ingestion pathway;

Soil leaching to groundwater pathway;

Groundwater vapor to enclosed space pathway;

Soil vapor to enclosed space pathway;

Groundwater to water line pathway;

Soil to water line pathway;

Surface water pathway.

Receptor Evaluation The receptors of concern for each pathway which must be evaluated are identified in the pathway-specific sections of this guidance. Receptors are divided into two categories – actual and potential.

Actual receptors include drinking and non-drinking water wells, public water systems, enclosed spaces, conduits, and surface waterbodies that, when impacted by chemicals of concern, may result in exposure to humans and aquatic life, explosive conditions, or other adverse effects.

Potential receptors are also considered in the receptor evaluation. Potential receptors are receptors not in existence at the time a Tier 1, Tier 2, or Tier 3 assessment is conducted, but could reasonably be expected to exist within 20 years. A protected groundwater source is also a potential receptor because of its possible future use as drinking water.

Source At Tier 1, “source” refers to the maximum concentrations of chemicals of concern, regardless of the origin of the petroleum release.

Pathway Clearance If the maximum concentrations of chemicals of concern do not exceed the applicable Tier 1 levels in the Tier 1 Look-up Table for a pathway, or if a pathway is incomplete, further assessment of that pathway is not required (the pathway obtains “clearance”). If the maximum concentrations for all chemicals of concern within a designated group of chemicals are below the Tier 1 levels, no further action is required regarding that group of chemicals (see Tier 1 Table for list of Group 1 and Group 2 chemicals).

However, if in the course of conducting further site assessment, data indicates the Tier 1 levels for a cleared pathway is exceeded, the pathway must be reevaluated as part of the

Tier 2 or Tier 3 assessment. Pathways that do not achieve clearance (pathways complete) must then be evaluated under the applicable Tier 2 or Tier 3 assessment procedure. A no action required site classification only applies when all pathways obtain no action required classification.

Corrective Action Response If the maximum concentrations exceed a Tier 1 level, there are four basic corrective action response options conduct a Tier 2, apply institutional controls, sever a pathway by plugging wells or removing water lines, or in limited circumstances, excavate contaminated soil to below the Tier 1 levels. Additionally, the owner or operator may be required to provide notifications of site conditions to authorities, such as the DNR’s Water Supply Section, utility companies supplying water services, and county authorities responsible for issuing private water supply construction permits. Corrective action responses permissible for each pathway are identified in the pathway-specific sections of this guidance. Technological controls are not acceptable at Tier 1.

TIER 1 PATHWAY-SPECIFIC GUIDANCE

The procedures for evaluating the seven pathways of concern are described below. The flow charts in the Appendix G may also be used as guides to evaluate pathways, but should not be used exclusive of this guidance.

Groundwater Ingestion Pathway The groundwater ingestion pathway addresses the potential for human ingestion of petroleum-regulated substances from existing drinking water wells, existing non-drinking water wells, or potential drinking water wells that could access a usable contaminated groundwater source. The term “protected groundwater source” is intended to identify sources of groundwater considered usable as drinking water. (Refer to Sampling

Requirements within this guidance for more information on protected groundwater source.)

Pathway Completeness

This pathway is considered complete if there is a drinking well or non-drinking water well within 1,000 feet of the source or the first encountered groundwater meets the definition of a protected groundwater source.

A drinking water well within 1,000 feet of the source area is considered an actual groundwater ingestion receptor. Tier 1 levels for actual receptors are applied to drinking water wells. A non-drinking water well within 1,000 feet of the source area is considered a potential groundwater ingestion receptor. Tier 1 levels for potential receptors are applied to non-drinking water wells. Potential receptor points of exposure exist for the entire area if the first encountered groundwater is a protected groundwater source. Tier 1 levels for potential receptors apply to protected groundwater sources. Any combination of these receptors may exist and each must be addressed using the applicable Tier 1 level and appropriate corrective action response.

If the pathway is incomplete, no further action is required for this pathway.

If the maximum concentrations of chemicals of concern do not exceed the applicable Tier 1 levels for actual or potential receptors, no further action is required for this pathway. If groundwater is not encountered during the investigation and the requirements for depth of drilling have been met and vulnerable bedrock is not encountered, this pathway cannot be evaluated and no further action is required for this pathway.

If the pathway is complete and the maximum concentrations on site exceed the applicable

Tier 1 levels for either actual or potential receptors a Tier 2 may be completed or an effective institutional control implemented. For example, limiting drinking water well installation is an acceptable form of institutional control.

If the pathway is complete regarding drinking water wells and the maximum concentrations exceed the Tier 1 levels for actual receptors, the pathway can be cleared by plugging all drinking water wells within 1,000 feet.

If the pathway is complete regarding non-drinking water wells and the maximum concentrations exceed the Tier 1 levels for potential receptors, the pathway can be cleared by plugging all non-drinking water wells within 1,000 feet.

If a protected groundwater source exists and the maximum concentrations exceed the Tier

1 levels for potential receptors, the institutional control must prohibit the use of the protected groundwater source within 1,000 feet of the contamination source area. The owner or operator must also provide notification of the site conditions on the appropriate

DNR form to the DNR's Water Supply Section and to the designated county authority responsible for issuing private water supply construction permits as provided in 567—38,

49. If an institutional control is not obtained, a Tier 2 must be conducted for this pathway.

If the receptor type is potential because of an existing protected groundwater source and the maximum concentrations are below the Tier 1 levels for potential receptors but exceed the Tier 1 levels for actual receptors, the owner or operator must provide notification of the site conditions on the appropriate DNR form to the DNR's Water Supply Section and to the designated county authority responsible for issuing private water supply construction permits as provided in 567—38, 49.

Soil Leaching to Groundwater Pathway This pathway addresses the potential for soil contamination to leach to groundwater. At Tier

1, this pathway evaluates risk of human exposure only through the groundwater ingestion pathway.

If the groundwater ingestion pathway is complete, the soil leaching to groundwater pathway is considered complete.

If groundwater is not encountered during the course of the investigation, the requirements for depth to drilling have been met, and bedrock has not been encountered, a survey for actual drinking and non-drinking water wells must be conducted.

If actual wells exist within 1,000 feet of the source, this pathway is complete.

Drinking water wells, non-drinking water wells, and protected groundwater sources are receptors for this pathway; however, only one Tier 1 level for each chemical of concern is applied to all receptor types.

If the pathway is incomplete, no further action is required for this pathway.

If the maximum concentrations of chemicals of concern in soil do not exceed the Tier 1 levels, no further action is required for this pathway.

https://www.legis.iowa.gov/DOCS/ACO/IAC/LINC/05-01-2013.Chapter.567.38.pdf https://www.legis.iowa.gov/docs/ACO/chapter/05-01-2013.567.49.pdf http://www.iowadnr.gov/InsideDNR/RegulatoryWater/WaterSupplyEngineering.aspx https://www.legis.iowa.gov/DOCS/ACO/IAC/LINC/05-01-2013.Chapter.567.38.pdf https://www.legis.iowa.gov/DOCS/ACO/IAC/LINC/05-01-2013.Chapter.567.49.pdf

If the Tier 1 levels are exceeded for this pathway, the options are to conduct a Tier 2, establish institutional controls which satisfy the conditions applicable to the groundwater ingestion pathway as described previously, or excavate contaminated soil for the purpose of removing all soil exceeding the Tier 1 levels in accordance with 567—135.9(7)“h” and the

Corrective Action Response section of this guidance document.

Groundwater Vapor to Enclosed Space Pathway This pathway addresses the potential for vapors from contaminated groundwater to migrate to enclosed spaces where humans could inhale chemicals of concern at unacceptable levels. This pathway evaluation assumes the health-based Tier 1 levels will also adequately protect for any short-term or long-term explosive risks.

If groundwater is encountered, this pathway is always considered complete for purposes of

Tier 1 and must be evaluated. This pathway is incomplete if groundwater is not encountered during the course of the investigation, the requirements for depth of drilling have been met, and bedrock is not encountered before groundwater.

Receptor evaluation

For the purpose of Tier 1, subsurface enclosed spaces are receptors and specifically include buildings with basements, storm and sanitary sewers, and underground utility vaults. Existing subsurface enclosed spaces and potential subsurface enclosed spaces are considered and the same Tier 1 level for each chemical of concern is applied regardless of receptor type. Additionally, an explosive vapor survey of existing enclosed spaces must be conducted in accordance with procedures in Receptor Survey section.

If the maximum concentrations of chemicals of concern do not exceed the Tier 1 levels and there are no explosive levels of vapors in enclosed spaces, no further action is required for this pathway.

Soil gas measurements (taken for the soil vapor to enclosed space pathway evaluation) may NOT be used to obtain clearance for the groundwater vapor to enclosed space

If the maximum concentrations exceed the Tier 1 levels for this pathway, the options are to conduct a Tier 2 or implement an institutional control. The institutional control must effectively eliminate and prohibit the placement of subsurface enclosed spaces within 500 feet of the source.

If potentially explosive levels (10% LEL) are detected when conducting the explosive vapor survey, contact local emergency services and report to the appropriate DNR http://www.iowadnr.gov/InsideDNR/DNRStaffOffices/EnvironmentalFieldOffices.aspx

Field Office. The groundwater professional must notify the responsible party or party contracting the site investigation to report the contamination to the DNR in accordance with IAC 567—131. The appropriate party must begin immediate response and abatement procedures in accordance with IAC 567—135.7 and IAC 567—133, proceed with the Tier 2 assessment, and evaluate the enclosed space as an actual receptor.

If soil gas measurements (taken for the soil vapor to enclosed space pathway evaluation) exceed the soil gas target levels and a Tier 2 is the corrective action selected, both the soil vapor to enclosed space pathway and the groundwater vapor to enclosed space pathway must be evaluated at Tier 2.

Soil Vapor to Enclosed Space Pathway This pathway addresses the potential for vapors from contaminated soils to migrate to enclosed spaces where humans could inhale chemicals of concern at unacceptable levels.

This pathway evaluation assumes the health-based Tier 1 levels will also adequately protect for any short-term or long-term explosive risks.

This pathway is always considered complete for purposes of Tier 1 and must be evaluated.

Receptor evaluation

For the purpose of Tier 1, subsurface enclosed spaces are receptors and specifically include buildings with basements, storm and sanitary sewers, and underground utility vaults. Existing subsurface enclosed spaces and potential subsurface enclosed spaces are considered and the same Tier 1 level for each chemical of concern is applied regardless of receptor type. If a Tier 1 level for soil is exceeded, soil gas samples may be collected in accordance with procedures in the Sampling Requirements section of this guidance document. Soil gas measurements are evaluated against the soil vapor target levels for pathway clearance. Additionally, an explosive vapor survey of existing enclosed spaces must be conducted in accordance with procedures in the Receptor Survey section of this guidance document.

If the maximum concentrations of chemicals of concern in soil do not exceed the Tier 1 levels and no explosive levels of vapors have been identified, no further action is required for this pathway.

If the maximum concentrations in soil exceed the Tier 1 levels, but soil gas measurements and confirmation samples taken at the location of maximum soil concentrations do not exceed the soil gas target levels and no explosive levels of vapors have been identified, no further action is required for this pathway.

The corrective action response options for this pathway are to conduct a Tier 2, establish institutional controls which effectively eliminate and prohibit the placement of subsurface http://www.iowadnr.gov/InsideDNR/DNRStaffOffices/EnvironmentalFieldOffices.aspx https://www.legis.iowa.gov/DOCS/ACO/IAC/LINC/05-01-2013.Chapter.567.131.pdf https://www.legis.iowa.gov/docs/ACO/chapter/567.135.pdf https://www.legis.iowa.gov/DOCS/ACO/IAC/LINC/05-01-2013.Chapter.567.133.pdf enclosed spaces within 500 feet of the source, or excavate contaminated soil for the purpose of removing all soil which exceeds the Tier 1 levels in accordance with 567—

135.9(7)”h” and the Corrective Action Response section.

If the maximum soil concentrations exceed the Tier 1 levels for this pathway and the soil gas measurements exceed the soil gas target levels, or if no soil gas measurements were taken, corrective action is required.

If explosive vapors are detected, even if maximum soil concentrations do not exceed Tier 1 levels, corrective action is required.

If potentially explosive levels (10% LEL) are detected when conducting the explosive vapor survey, contact local emergency services and report to the appropriate DNR Field Office. The groundwater professional must notify the responsible party or party contracting the site investigation to report the contamination to the DNR in accordance with IAC 567—131. The appropriate party must begin immediate response and abatement procedures in accordance with IAC 567—135.7 and IAC 567—133, proceed with the Tier 2 assessment, and evaluate the enclosed space as an actual receptor.

If soil gas measurements exceed the soil gas target levels and a Tier 2 is the corrective action selected, both the soil vapor to enclosed space pathway and the groundwater vapor to enclosed space pathway must be evaluated at Tier 2.

If soil gas measurements exceed the soil gas target levels and excavation is the corrective action selected, soil gas measurements must be taken again after the excavation has been completed. The post-excavation soil gas measurements must be taken outside the excavated area, but near the area expected to exhibit the highest soil gas concentrations.

For example, if the maximum benzene concentration remaining in soil after an excavation is 1.5 mg/kg from a sidewall sample, soil gas measurements should be collected near that sidewall in native soil. If the post-excavation soil gas measurements exceed the soil gas target levels, both the soil vapor to enclosed space pathway and the groundwater vapor to enclosed space pathway must be evaluated at Tier 2.

Groundwater to Water Line Pathway This pathway addresses the potential for creating a drinking water ingestion risk due to chemicals of concern in groundwater contacting susceptible water lines and diffusing into the drinking water.

This pathway is considered complete for actual receptors if there is an existing water line within 200 feet of the source and the first encountered groundwater is less than 20 feet below the ground surface. The pathway is considered complete for potential receptors if the first encountered groundwater is less than 20 feet below the ground surface. All current and any available historical groundwater elevation information must be considered and the https://www.legis.iowa.gov/DOCS/ACO/IAC/LINC/11-27-2013.Chapter.567.135.pdf https://www.legis.iowa.gov/DOCS/ACO/IAC/LINC/11-27-2013.Chapter.567.135.pdf https://www.legis.iowa.gov/DOCS/ACO/IAC/LINC/11-27-2013.Chapter.567.135.pdf http://www.iowadnr.gov/InsideDNR/DNRStaffOffices/EnvironmentalFieldOffices.aspx http://www.iowadnr.gov/InsideDNR/DNRStaffOffices/EnvironmentalFieldOffices.aspx https://www.legis.iowa.gov/DOCS/ACO/IAC/LINC/05-01-2013.Chapter.567.131.pdf https://www.legis.iowa.gov/docs/ACO/chapter/567.135.pdf https://www.legis.iowa.gov/DOCS/ACO/IAC/LINC/05-01-2013.Chapter.567.133.pdf estimated seasonal high level must be used for determining pathway completeness.

For the purposes of Tier 1 assessment, existing water…