Presentation on theme: "2014 Vapor Intrusion Guidance Amendments Discussion Points Waste Site Cleanup Advisory Committee Meeting May 22, 2014."— Presentation transcript:
2014 Vapor Intrusion Guidance Amendments Discussion Points Waste Site Cleanup Advisory Committee Meeting May 22, 2014
2 Vapor Intrusion Guidance Survey Results 125 responders to survey on VI 50 percent of responders LSPs 30 percent environmental professionals 10 percent of responders DEP staff Remaining 10 percent risk assessors and attorneys
3 Vapor Intrusion Guidance Survey Results Most useful parts of Chapter 1 - Flow Chart, Figure 1- 1, and discussion relative to Other Factors to Support Need to Evaluate VI pathway Most useful in Section 2 - Lines of Evidence for VI Pathway, VI screening criteria, data considerations, & Lines of Evidence Tables (2-2 and 2-3)
4 Vapor Intrusion Guidance Survey Results Approximately 90% occasionally or often use Lines of Evidence Tables and find them helpful Vapor Intrusion Mitigation System Monitoring Table 3-1 most useful (57% use occasionally or often). 95% who use say its clear and helpful CEP discussion and Figures 4-2 thru 4-4 are the most helpful 75% said that they used Indoor Air Threshold Values, 25% stated occasional use. Many comments that they are very useful.
5 Vapor Intrusion Guidance Survey Results 45% said that less than 25% of indoor air sampling has led to the need for mitigation, about 30% said between 25-50% of indoor air sampling has led to the need for mitigation and about 25% said that more than 50% of indoor air sampling has led to the need for mitigation Over 90% use the Sub-Slab Screening Values in Appendix II occasionally or often (65%). Most said they were very useful/helpful 50% said that 25-50% of sub-slab soil gas sampling has led to indoor air sampling Sub-slab sampling protocols and survey were cited as most useful of Appendix III
6 Vapor Intrusion Guidance Survey Results Biggest concerns: 65% would like to see considerations re: differences between chlorinated and petroleum VOCs acknowledge that confounding sources is the greatest VI assessment challenge and the difficulty of distinguishing contributions from indoor sources more guidance on how to close a CEP More guidance relative to evaluating future VI at sites with existing buildings and future buildings
Questions for Guidance/ Public Comment 7
8 “New” SRM Reporting Conditions f) releases to the groundwater or to the vadose zone that have resulted or have the potential to result in the discharge of vapors into a School, Daycare or Child Care Center or occupied Residential Dwelling. Conditions that indicate a potential discharge of vapors into a School, Daycare or Child Care Center or occupied Residential Dwelling include, but are not limited to: 1. Soil or soil gas impacted with one or more volatile organic compounds within six feet, measure horizontally from the wall of the structure, and within ten feet measured vertically from the basement floor or foundation at concentrations that are likely to discharge vapors into the structure; If soil concentrations (e.g., tank removal within 6 feet of building trigger SRM, then LRA not allowed). What concentrations in soil trigger SRM?
MassDEP considered differences relative to petroleum-related VOCs when preparing 2011 Draft Document – MassDEP recognizes that petroleum compounds degrade in an oxygenated vadose zone – The GW-2 Standards take into account the greater attenuation of petroleum VOCs – There is no difference in attenuation of petroleum VOCs and chlorinated VOCs from the sub slab (immediately below the slab) 9 VI of Petroleum Compounds
MassDEP considering differences of evaluating petroleum-related VOCs relative to: – Assessing how to address soil contaminated with petroleum-related VOCs adjacent to School, Daycare or Child Care Center or occupied Residential Dwelling (within 6 feet horizontally; 10 feet vertically) – Using a PID to determine if VOCs are “likely” to discharge vapors into the structure Based on typical constituents in fuel oil and the response each would produce on PID 10 VI of Petroleum Compounds
11 Confounding Sources – COC is used in the Building How do you achieve a Permanent Solution if the COC is used in the building? Sample sub-slab soil gas and estimate EPCs through modeling – MassDEP recommends empirically-based modeling (MassDEP’s 70-fold attenuation factor) or other technically justifiable model Since it would be difficult to determine the contribution to the indoor air from the sub-slab soil gas, submit a Temporary Solution Statement?
12 Sampling when Groundwater Elevation is High How do you collect the multiple lines of evidence if the elevation of the groundwater is at or very near the elevation of the slab? Sample indoor air Sample groundwater discharging to the sump – Consider timing of rainfall event (CSM) – Can’t compare concentration of VOCs in sump water to GW-2 Standards to rule out a problem
13 Future Exposure Issues – Changes to Existing Buildings When you have high sub-slab soil gas without current exposure it is difficult to demonstrate what the future EPCs will be. Recommendation - determine future EPCs using empirically- based modeling (MassDEP’s 70-fold attenuation factor) or other technically justifiable model If future EPC developed from model does not support NSR, an AUL would be required to ensure building features preventing/inhibiting vapor intrusion stay the same; preferential pathways are not created
14 Future Exposure Issues – New Construction in GW-2 Areas Does Post-Closure work for new buildings in areas previously not GW-2 require MCP submittals? If the work conducted are “standard construction” activities (water-vapor barrier, passive radon systems, etc.), and does not generate remediation waste, an MCP submittal would not be required – Should sample indoor air to confirm that a condition requiring Notification has not been created (indoor air sampling results need not be submitted unless Notification is required) However….
15 Does Post-Closure work for new buildings in areas previously not GW-2 require MCP submittals? If the activities are designed to achieve NSR, whether passive or active, conduct as an MCP response action (per ) – Submit a RAM Plan for the construction of soil-gas vapor barrier, passive or active venting system, etc. – Indoor air sampling should be conducted following construction to determine whether NSR has been achieved (indoor air sampling results submitted as part of the RAM reporting) – If sampling indicates that system is necessary to maintain NSR, then implement with AUL (if ÆPMM, meet AEPMM requirements, including telemetry) Future Exposure Issues – New Construction in GW-2 Areas
Telemetry provides notification (by , telephone or text) to building owner/operator and MassDEP upon system shutdown 16 Telemetry
17 Telemetry Format/Info Fields RTN Device Type Device Unique ID Number Activity (shut down, restart) Location (building name, floor, room, etc.) Address Submittal date Submittal time Event date Event time Submitter name Submitter tel. number Submitter address for communications to MassDEP (available soon on MassDEP website):