Procedures for Determining Needed Action for Point Source Pollution Occurrences From Petroleum Releases Using Risk-Based Corrective Action (RBCA)
If not already known, the Department will identify, if possible, the source(s) of contamination and the responsible party (or parties). The Department will notify the responsible party after the determination has been made. A responsible party is to complete the following protocol in accordance with Chapter 6, 002.
Part I. IMMEDIATE ACTION
Step 1. Initial Review
1) Perform an initial review to determine whether immediate action is needed to eliminate the existence or likelihood of an imminent and substantial threat to the public health and welfare or the environment or to mitigate the significantly increasing difficulty of cleanup if action is delayed, and if so, what actions are required. Base the review on as many of the items addressed in Step 6 as possible.
a) imminent - a short time span (i.e., less than 90 days) 2) If the need for immediate action is apparent or if the need cannot be readily determined, proceed to Step 2 and work in conjunction with Department.
b) substantial - a significant impact on the public or environment (e.g., human illness or death, serious financial loss, severe ecological damage)
c) significant - if action delayed, cleanup costs increase by one or two orders of magnitude
d) Immediate actions - may include cleanup to at least an initial level, stabilization or containment, monitoring, shutdown/termination of facility/activity, or any combination of measures. These actions are carried out by the responsible party.
3) If no immediate action is necessary (e.g., due to the nature of the pollution event developing over many years or moving slowly), proceed to Step 4.
Step 2. Implementation of Immediate Actions
1) Implement the immediate actions identified as required by Step 1 or as determined necessary in consultation with the Department.
Proceed to Step 3 when the immediate actions have been completed.
Step 3. Evaluation of Immediate Actions
1) Determine if immediate action has been successfully eliminated the imminent and substantial threat to the public health and welfare and the environment or successfully mitigated any significant increase in difficulty of cleanup associated with delayed action.
2) If the immediate action was unsuccessful, return to Steps 1 and 2.
3) If requirements were met, proceed to Step 4.
Step 4. No Immediate Threat Present
Immediate action is not now needed, but additional measures for complete and permanent resolution of the problem may be required. Further assessment is necessary to determine the need for any final remedial action.
Proceed to Part II, Step 5.
Part II. FINAL REMEDIAL ACTION
If at any time during the Part II assessment an immediate threat is identified, return to Step 1 (Part I).
Step 5. Preliminary Assessment
1) Complete a preliminary assessment to evaluate the possible threat of contamination to soils and ground water and threat to public health and welfare. This assessment involves a review of existing information and require the collection of minimal or no field data. If it can be determined by the Department from this preliminary assessment that there is limited soil contamination and no threat of ground water contamination or threat to human health and welfare, proceed to Step 12. If soil contamination is extensive or its extent is unknown or ground water contamination is possible or likely, proceed to Step 6.
Step 6. RBCA Tier 1 Site Assessment
1) Before this or any subsequent assessments are started, contact the Department to establish what information must be collected. The Department will specify sampling and analysis requirements.
2) Collect all information, including any site assessment data, as directed by the Department. The required site assessment data will include, but not be limited to, the following types of information:
1. historical information;
2. site information;
3. contamination characteristics;
4. aquifer characteristics.
3) Investigate the following potential exposure pathways for chemicals of concern designated by the Department:
1. Dermal contact with and ingestion of chemicals of concern from contaminated surface soils;Individual chemicals of concern are designated based on the petroleum product(s) released at the site and include, but are not limited to, the following:
2. Enclosed space inhalation of chemicals of concern from contaminated subsurface soils;
3. Leaching of chemicals of concern from contaminated surface and subsurface soils to ground water;
4. Enclosed space inhalation of chemicals of concern from contaminated, shallow ground water; and,
5. Ingestion of chemicals of concern from contaminated ground water.
|Light Distillates (e.g., gasoline, JP-4)
Methyl tertiary-Butyl Ether (MTBE)
|Middle Distillates (e.g., diesel fuel, kerosene)
*To be determined on a case-by-case basis as directed by the Department. The Department will provide investigative and sampling requirements for these chemicals as needed.
4) Report the required information to the Department in the format specified by the Department.
Step 7. Evaluation of RBCA Tier 1 Investigation Results
In evaluating the RBCA Tier 1 investigation results, the contamination levels found during the site investigation will be compared to risk-based screening levels (RBSLs) which will be established by the Department using the following criteria:
1. Remedial Action Classifications.
A remedial action class (RAC) is defined for pollution events in three types of ground water (or overlying soils) depending on the degree (or potential) of use of the ground water as drinking water. The extent of remedial action recommended will differ depending on the RAC of the contaminated (or likely to be contaminated) ground water. The RAC assigned will be determined from the condition of the ground water prior to the pollution event. The Department will assign the RAC based on information submitted by the responsible party in the RBCA Tier 1 site assessment and other available information.
RAC-1. This category includes ground waters of Class GA and the portion of Class GB in a 500-foot radius (or greater, if determined necessary by the Department) around all private drinking water supply wells. RAC-1 is automatically assigned anytime a public or private drinking water supply well has been polluted.
RAC-2. This category includes ground waters of Class GB (except for the portion of Class GB placed in RAC-1) and Class GC(R).
RAC-3. This category includes, but is not limited to, ground waters of Class GC (except for Class GC(R) which was placed in RAC-2).
The RAC categories are not intended to represent a ground water classification system but rather a pollution event ranking scheme. It gives the Department a method to determine the importance of remedial action based on the use of the ground water. For instance RAC-1 is the category of highest rank; it represents that ground water actually being used for drinking water and that ground water intended to be used in a public drinking water supply. Therefore, RAC-1 events will normally receive the most extensive remedial action measures.
RAC-2 events involve ground water not now directly used as drinking water but having a reasonable potential to be used in the future. The potential for use exists if the ground water is located in a highly populated area or is part of a regional, high-yielding aquifer or if otherwise justified. The RAC-2 category also includes ground water with prior contamination that may be easily or cost-effectively treated to drinking water quality.
Pollution events will be of lowest importance, RAC-3, if the ground water involved is not used, or likely to be used, as drinking water. Generally remedial action measures will be least extensive for this category since the future use of ground water for drinking is improbable. Justification for assigning events to RAC-3 will be based on a combination of several different reasons. One reason for unusability is poor natural quality which makes the ground water unfit for human consumption. Insufficient yield is another reason the ground water may not be used for drinking. A third reason is historical contamination that occurred prior to the pollution event currently being investigated (see NRS § 81-1505(2)(d)). This past contamination may have rendered ground water unsuitable for drinking and uneconomical to treat. Past and present intensive land use is also a reason why ground water could be unusable as drinking water. This includes areas of concentrated industrial development or densely populated areas where ground water is likely to be contaminated or will not be used as drinking water.
The ranking of some events as RAC-3 does not mean there will be places in the State where wholesale contamination of ground water will be allowed. Departmental authority through its various programs to control practices or discharges that may contaminate ground water will still be in effect. RAC-3 occurrences, in general, will be given a lower priority and less staff effort by the Department than RAC-1 or RAC-2 occurrences; however, cleanup of a RAC-3 event may be required due to concerns about enclosed space inhalation exposure pathways and vapors threatening public health and welfare.
RACs were developed primarily for use with the principal aquifer--the ground water commonly used for drinking. They will also be adapted for use with both deeper and perched ground water. When doing so, interconnections with overlying or underlying ground water of different quality will be considered.
Some contamination threats may occur in which the use potential of the ground water would be RAC-1 or RAC-2, but the soil, geology, and other site-specific characteristics are such that ground water contamination is virtually impossible. After an appropriate assessment, the event may be downgraded to RAC-3.
In every ground water contamination occurrence, certain minimum requirements will be imposed upon the responsible party, depending on the RAC. Cleanup of readily removable contaminants (e.g., free product) will be required. Additional cleanup and/or mitigation may also be required. If additional cleanup is not required, the remaining contaminated ground water will be managed and monitored to prevent any further damage.
In RAC-3, cleanup of readily removable contaminants (e.g., free product) will be required. Additional cleanup of a RAC-3 event may be required due to concerns about enclosed space inhalation exposure pathways and public health and welfare. Monitoring may also be necessary. Because RAC-3 ground water is generally not used for drinking water, the ground water ingestion and soil leaching to ground water pathways are considered to be incomplete in RAC-3 and not subject to this RBCA assessment.
2. Carcinogenic and non-carcinogenic health effects.
A. Carcinogenic effects
Chemical-specific Maximum Contaminant Levels (MCLs) (see Chapter 3) will be used to calculate the appropriate RBSL for a carcinogen for the groundwater ingestion and soil-leaching to groundwater exposure pathways of concern for a RAC-1 release.
An Excess Lifetime Cancer Risk (ELCR) of 1x10-6 will be used in the calculation of the RBSLs for a carcinogen for the dermal contact/soil ingestion exposure pathway and for inhalation pathways in the presence of subsurface structures for all releases.
An ELCR of 1x10-5will be used in the calculation of the RBSLs for a carcinogen for the groundwater ingestion and soil-leaching to groundwater exposure pathways of concern for a RAC-2 release and for the inhalation exposure pathways when no subsurface structures are present for all releases.
B. Non-carcinogenic effects
Chemical-specific MCLs (or a health-based standard where an MCL has not been promulgated for a particular chemical) will be used to calculate the RBSL for a non-carcinogen for the groundwater ingestion and soil-leaching to groundwater exposure pathways of concern for a RAC-1 release.
RBSLs for non-carcinogens for the groundwater ingestion and soil-leaching to groundwater exposure pathways of concern for a RAC-2 release, for the dermal contact/soil ingestion exposure pathway for all releases, and for the enclosed space inhalation pathways for all releases will be established by the Department using the following criteria:
1. exposure pathway;
2. RAC designation;
3. level of exposure based on the ratio of the observed concentration of a chemical of concern to a chemical-specific reference concentration.
For purposes of the RBCA Tier 1 assessment, toluene, ethylbenzene and total xylenes are considered to have additive health effects.
3. Fate and transport models. The Department will select various models and model default values to calculate RBSLs for use in evaluating the RBCA Tier 1 data.
4. Land use.
5. Location of water supply wells.
6. Other criteria as determined by the Department.
Upon comparing the RBSLs to the actual contamination levels found during the site investigation and consideration of other pertinent factors, the Department will determine if additional remedial actions will be required. If additional remedial actions are not required, proceed to Step 11. Otherwise, proceed to Step 8.
Step 8. RBCA Tier 2 Site Assessment
1) Perform a RBCA Tier 2 site assessment for those exposure pathways where actual site contamination levels were greater than the Tier 1 RBSLs under Step 7. This investigation will define the extent of contamination from the release and collect site-specific parameters to use in the Tier 2 evaluation performed under Step 9. The Department will specify what data needs to be collected for the Tier 2 site assessment. Work will be approved by the Department prior to beginning the investigation.
2) Report the results of the Tier 2 site assessment in the format specified by the Department. The Department may, at any time, request additional information.
Step 9. Evaluation of RBCA Tier 2 Investigation Results, Determination of Site-Specific Target Limits, and Review of Proposed Remedial Actions
The site-specific physical and chemical assessment found during the Tier 2 site assessment will be used to establish site-specific target limits (SSTLs) using the same fate and transport models previously used to establish the RBCA Tier 1 RBSLs. The contamination levels found during the investigation will be compared to the SSTLs in a manner similar to that performed for the RBCA Tier 1 evaluation.
1) The Department will determine if additional remedial actions will be required. If additional remedial actions are not required, proceed to Step 11.
2) The Department will set a preliminary cleanup level for any additional cleanup required. The level will normally be set at the appropriate SSTL(s). After receiving notification of the preliminary cleanup level, either agree or propose an alternate level. If a different cleanup level is proposed, it must be based on a technological, risk, or economic analysis. The Department may also propose an alternate level.
a) A technological analysis will determine if technologies exist to clean up the soil and/or ground water to the preliminary cleanup level. If cleanup to the preliminary level is not technologically possible, report what level of cleanup is attainable. As part of this analysis, the technological feasibility of various mitigative actions (e.g., supplying new sources of water and point-of-use treatment) should be investigated.
b) A risk analysis may include other factors, information, or evaluations not previously considered. Other ELCR target levels may be considered if appropriate.
c) For an economic analysis, examine the economics of cleaning up to the preliminary level. If it is impossible to reach the preliminary cleanup level, report what level of cleanup is economically possible. The economic feasibility of mitigation instead of cleanup should also be analyzed.
If cleanup to the preliminary level is not attainable based on one or more of the foregoing analyses, report what portion of the soil and/or ground water will remain contaminated following a lesser degree of cleanup. Given the technological considerations of cleanup, the appropriate calculations should be used in an attempt to define the three-dimensional boundary of the contamination plume under different remedial action scenarios (including no cleanup). The contamination plume, in this case, is defined as soil and/or ground water where the concentrations of identified contaminants exceed their preliminary cleanup levels. For every cleanup scenario assessed, the economic impacts are to be defined. The relationship of the contaminated media (i.e., ground water, soils, soil gas) boundaries to existing users and potential points of exposure must be described.
If submitting an alternative cleanup level, include any supporting justification for an alternate cleanup level, a contamination maintenance program, a mitigation plan, or combination. The Department will consider the information contained in the justification on a case-by-case basis and establish a proposed final cleanup level or action. The level may be the same as the Department's preliminary cleanup level, the same as the proposed alternate cleanup level, or some other level.
The Department's decision on the remedial action necessary, including the proposed final cleanup level, will be placed on public notice. Any person may submit written comments on the proposed action or may request a hearing.
Following the comment period and any hearing the Department will notify the responsible party of Department's final decision (including changes made as a result of a hearing).
3) Develop a workplan and schedule for performance of the final remedial action. The time frame for required action (including cleanup) will be the period of potential exposure to the contamination in the absence of any remedial action or 20 years, whichever is less. On a case-by-case basis, a longer period of time may be allowed if adequately justified by the responsible party. The workplan is subject to the Department's approval.
Step 10. Implementation and Review of Remedial Actions
1) Obtain any other permits from the Department that may be required to implement the workplan (e.g., UIC, NPDES).
2) Implement the remedial actions approved in the workplan.
3) Keep the Department apprised of cleanup efforts, and the Department will periodically review the effectiveness of the remedial actions. If the Department determines the long-term needs of protecting the public health and welfare and the environment have not been, or are not being, satisfied or if additional remedial action is necessary, the Department may require a return to Steps 8 and 9.
4) A request may be made to modify the required final remedial action during the implementation process. Any request must be accompanied by additional justification as described in Step 9. The Department may propose modifications to the required final remedial action. If a change is appropriate, a public notice will be issued.
Step 11. Final Review
A final review will be performed by the Department to determine the need for any ongoing actions. These may include long-term monitoring to ensure cleanup levels are stabilized and maintained, periodic sampling of nearby supply wells, maintenance of installed structures, and annual case review. If established cleanup levels were never reached, ongoing monitoring or maintenance may be necessary to ensure other soil and/or ground water does not become contaminated and/or public health and welfare threats do not exist.
1) Continue any ongoing actions determined to be necessary by the Department until ground water and soil contamination is no longer a concern.
Step 12. Closure
The situation does not pose a threat to ground water quality or public health and welfare.