6.1 Mitigation
Mitigation can be broken into four distinct phases:
- Phase 1: Design (see Section 6.1.1)
- Phase 2: Installation and Commissioning (see Section 6.1.2)
- Phase 3: Operation, Maintenance, and Monitoring (see Section 6.1.3)
- Phase 4: Exit Strategy including Decommissioning (see Section 6.1.4)
EGLE has developed a Table of Contents (TOC) for Active and Passive Mitigation Systems that, when followed, will provide the necessary information for Design; Installation and Commissioning; and OM&M submittals. These can be found in Attachment A.5 for Active Mitigation Systems and B.5 for Passive Mitigation Systems. Though EGLE has not developed a TOC for other response activities, the TOC provides an outline that that can be followed to provide information to complete the review process if requested.
Each phase and the information that should be considered is described in further detail below. A TOC for the decommission and exit strategy for a vapor mitigation system (VMS) was not developed as each site would need to be able to demonstrate that unacceptable risk through the VIAP is no longer present. At some sites, it may require that the vapor source for which the mitigation system was installed has been effectively addressed to below applicable criterion (can be demonstrated with representative soil gas sampling) and often requires a site-specific approach to make an effective demonstration. Additional information on the information necessary to provide is included in Section 6.1.4.
6.1.1 Design
The design process should begin with a consideration of the site elements applicable to mitigation and the mitigation objectives that will lead to the design basis (i.e., an explanation of how the selected approach and technologies will meet the mitigation objectives at the site). Once sufficient information is available for design, the next consideration is the design itself— the area that requires mitigation along with the system components, installation details, and specifications. The TOC for the Design that will be submitted to EGLE can be found in Attachment A.5 for Active Mitigation Systems and B.5 for Passive Mitigation Systems.
Note: The approval of a mitigation system design from EGLE will be to ensure that the system has a reasonable likelihood of success and will be on a performance basis. It will be the obligation of the submitter to verify that the design performance metrics are being met and that the unacceptable risks from the VIAP are being mitigated.
Other design considerations include installation and operating permitting requirements; stakeholder requirements and communications; and the need for construction quality control, demonstration of system effectiveness and reliability, and OM&M plans, including an exit or closure strategy. Table 1-1 of ITRC’s Design Consideration Fact Sheet identifies the design considerations and are discussed in more detail in ITRC’s (2020) Design Considerations Fact Sheet. The importance of any factor can vary depending on site- and building-specific conditions and regulatory requirements.
6.1.2 Installation and commissioning
Planning, preparation, and oversight conducted during installation are as important as post-installation VMS confirmation. Attention to these items will greatly improve the post-installation evaluation and provide for a more successful implementation. The formality of planning and construction quality assurance (CQA) during installation will depend on the size and complexity of the building and the mitigation system to be constructed. When submitting a document for EGLE review and approval, that documents the installation and commissioning of the vapor mitigation system, a TOC was developed for Active and Passive Mitigation Systems that, when followed, will identify and provide the necessary information and provides a format that will allow EGLE to complete a timely review. The TOC for the Installation and commissioning can be found in Attachment A.5 for Active Mitigation Systems and B.5 for Passive Mitigation Systems.
Prior to the actual construction, plan the post-installation evaluations and documentation requirements, and communicate them to the installer and CQA representative(s). During construction, pay attention to ensuring quality construction. Certain post-installation testing should occur during construction (while the installer is still present) to allow for rapid system adjustments. Other post-installation testing will likely occur days or weeks after the system is installed and operating.
After the installation of the mitigation strategy is complete, post-installation verification and testing are performed to confirm achievement of the design and operating parameters. During this time the mitigation system is confirmed to be operating and meeting performance specifications. Table 3-1 of ITRC’s Fact Sheet identifies the Pos- Installation considerations that are discussed in more detail in ITRC’s (2020) Post Installation Fact Sheet. The importance of any factor can vary depending on site- and building-specific conditions and regulatory requirements.
6.1.3 Operation, maintenance, and monitoring (OM&M)
The OM&M provides instructions for operation and upkeep necessary to ensure the VMS remains effective and is prepared for each installed VMS. The goal of OM&M is to verify performance of the VMS during operation as compared to performance during system commissioning, and to inspect and repair any system malfunction (i.e., VMS not operating to meet performance objectives or due to system equipment life expectancy). In cases where testing shows the VMS is not working and no defects in the system components have been identified, it is recommended to re-evaluate the site data presented in the CSM to determine the presence or contribution of additional VOC sources or factors that may be influencing the system’s operation.
When submitting a document for EGLE review and approval of that supports Operation, Maintenance, and Monitoring of the vapor mitigation system, a TOC was developed for Active and Passive Mitigation Systems that when followed that identifies the necessary information and provides a format that will allow EGLE to complete a timely review. The TOC for the OM&M can be found in Attachment B.5 for Active Mitigation Systems and C.5 for Passive Mitigation Systems.
ITRC (2020) developed key OM&M considerations and identifies their typical importance for active systems and for passive systems (see Passive Mitigation Fact Sheet). Rapid response activities may or may not have an OM&M component as they are not intended to be operated long term and should only be used temporarily until replaced by a permanent VIMS. Table 2-1 in ITRC’s Fact Sheet identifies key considerations for OM&M and further information on each of these is provided in ITRC’s (2020) Operation, Maintenance, and Monitoring/Exit Strategy Fact Sheet.
6.1.4 Exit strategy
Where possible, the preferred response to address VI is to eliminate or reduce the level of volatile chemical contamination in the source (e.g., groundwater, NAPL, and subsurface soil) to levels that eliminate the need to mitigate or monitor. If subsurface remediation activities are being conducted at the site, termination of these activities will be contingent on demonstrating that the chemical-specific cleanup levels for the subsurface media have been attained or compliance is shown with representative soil gas sampling.
Typically, monitoring and mitigation will continue until the source(s) are remediated to cleanup levels that eliminate the need to mitigate VI at the point of exposure. As appropriate, the exit strategy may provide criteria for phased remediation, resulting in a termination evaluation as source cleanup levels are achieved in parts of the contaminated area. If the subsurface vapor source(s) is not remediated, it is anticipated that remediation (and monitoring and any building mitigation) will continue.
6.2 Submittals
An outline of the various submittals and forms for Part 201 is contained in Attachment C.5.