A complete list of all programs within the Department of Environment, Great Lakes, and Energy (EGLE)
Community involvement and public participation are an essential part of EGLE’s mission, vision, and values.
Resources and information on utilizing RRD's data exchange and the Inventory of Facilities.
An interactive map displaying contaminated sites throughout Michigan regulated under Parts 213, 201, and 211.
EGLE's interactive calendar is designed to provide timely information on decisions before the Director, proposed settlements of contested cases, administrative rules promulgation, public hearings, meetings and comment deadlines, and environmental conferences, workshops and training programs.
The Michigan Freedom of Information Act (FOIA) provides all persons (except persons incarcerated in correctional facilities) with access to public records of public bodies. Requests to inspect or receive public records from EGLE must be in writing and describe the requested records with enough detail to enable the department to identify and locate the requested records. Some records are exempt from disclosure under the FOIA or another statute and thus will not be provided. A fee may be charged to process your request. Please note that many records are available that do not require a formal FOIA request.
Search is currently unavailable. Please try again later.
The web Browser you are currently using is unsupported, and some features of this site may not work as intended. Please update to a modern browser such as Chrome, Firefox or Edge to experience all features Michigan.gov has to offer.
Volume 4: Investigative approach for petroleum VIAP
Under Part 201, NAPL, the presence of shallow groundwater, and certain foundation types prevent the use of the generic groundwater volatilization to indoor air inhalation criteria and soil volatilization to indoor air inhalation criteria for the evaluation of the VIAP. Therefore, the location where any one of these conditions exist, the determination of the extent of a vapor source requires the development of site-specific criteria and are referred to as the VIAC. Once the criteria have been established, the extent of the vapor source should be defined using appropriate sampling methodology.
For petroleum releases, the vapor source is limited to where the NAPL is located (i.e., residual, mobile, and migrating) above the zone of saturation and the location where the dissolved phase groundwater contamination above the applicable unrestricted residential VIAC is present at the top of the aquifer. The extent of the NAPL body will be determined using multiple lines of evidence as discussed in EGLE’s June 2023 Non-Aqueous Phase Liquid – Petroleum Releases Characterization, Remediation, and Management Guidance, which will likely include the chemical analysis of soil samples.
NOTE: If an evaluation is made in accordance with Rule 299.14(5) using more representative data such as soil gas, it is possible to show compliance with the groundwater criteria or screening levels, which can aid in the delineation of the vapor source. Soil gas data may also be used to show that the NAPL does not represent a vapor intrusion risk for a current structure or future structure. The need for land or use restrictions will be highly dependent on-site conditions, how or where the soil gas samples were collected in relation to the vapor source, and if future structures can be evaluated with the soil gas samples. See Attachment D.4 for more details.
Investigation methods are further described in Section 5 and Volume 2 – Investigation Methods for the Volatilization to the Indoor Air Pathway (VIAP).
For NAPL and dissolved-phase petroleum sources in the groundwater, understanding the NAPL body and groundwater plume stability is a key factor in establishing the extent of the vapor source. This document is not intended to fully address how stability is established; however, in general stability is determined by:
Additional considerations for the vapor source delineation are provided below.
The chemicals selected for analysis at a potential PVI facility depend on the petroleum product released and type of contamination, as well as the objectives of the investigation. A list of the recommended parameters for petroleum products can be found in Appendix B of the Application of Target Detection Limits and Designated Analytical Methods RRD Resource Materials, 2016.
If vapor samples are collected, an assessment of biodegradation should be conducted and include the analysis of O2, CO2, and methane. After O2 is depleted, methanogenic bacteria convert petroleum hydrocarbons to methane and carbon dioxide. If methane is above 1% by volume, then conditions are anaerobic and is indicative that the sampling is likely near a petroleum NAPL source. Additionally, nitrogen may be collected as an indicator as to whether there is replenishment of atmospheric air or an advective flow of soil gas that flushes out the air. If nitrogen is displaced (much less than 79% by volume), then either the bulk soil gas is migrating, or the sample was collected under a vacuum. (ITRC, 2014).
Geologic and hydrogeologic information should be collected throughout the investigative process and incorporated into the CSM until there is an adequate understanding of the facility conditions and where the vapor source is located. The processes, methodology, and sampling density necessary to understand a facility is not discussed as part of this document. Each of these items is highly dependent upon the actual facility conditions, the variability that is present within the geology and hydrogeology in the area where the petroleum release occurred, and the potential risks being evaluated. The key for evaluating the VIAP is utilizing the data that is collected and evaluating how that data changes the CSM, impacts the need for additional information or evaluation, or may impact the way vapors from a vapor source migrate into a structure, as well as evaluating what potential risks may be present currently or in the future.
Groundwater or NAPL, as a subsurface vapor source, will be influenced by the vertical distribution of contaminant concentrations in the upper reaches of the water table and by seasonal fluctuations in the groundwater table (McAlary et al., 2011; ITRC’s PVI-1, 2014; and USEPA, 2015a and 2015b). Vapor sources that are beneath the water table at depths greater than 5 feet below the seasonal low-water elevation (10 feet may be assumed if the water table variation is unknown) do not need further evaluation for the VIAP. Seasonal evaluations will need to be made for NAPL bodies that are beneath the groundwater and could be exposed to the vadose zone with elevational changes to the groundwater surface. The need for a land or use restriction may be applicable if land use changes could result in an unacceptable exposure or an evaluation cannot be made for future land uses. This is further discussed in Volume 5 – Response Activity.
The utilities and utility corridor must intersect the vapor source for there to be alterations in migration routes of the vapor source or direct transport. For the utility corridors, it is important when defining the vapor source to identify utility corridors that may have more porous and permeable material than the adjacent native soil as well as a vapor source that can migrate (e.g., mobile NAPL and dissolved phase). For the utilities, it is important to identify the utilities where the vapor source of mobile NAPL can directly enter, and the utility then may serve as a conduit to directly transport vapors into a structure.
NOTE: Utilities that are pressurized (e.g., water and gas lines), or that are documented to not connect to structures (e.g., dedicated storm sewers), are not necessary to evaluate beyond supplying supporting documentation. Supporting documentation should include the type and location of the utility.
Consideration of the backfill material as a preferential pathway for the vapor source is limited to facilities that have site soils that consist of finer grain soil materials (e.g., silts and clays) that were backfilled during the installation of the utility with coarser grain materials (e.g., gravels and sands). For the backfill to act as a preferential pathway, the NAPL or groundwater vapor source must be able to enter the backfill material and then migrate along the utility corridor.
NOTE: Backfill in a utility corridor that is similar in grain size and permeability to the native material is not necessary to evaluate beyond supplying supporting documentation commonly obtained through standard soil sampling techniques and documentation.
