PA Vapor Intrusion Guidance Society of Women Environmental Professionals Capital Chapter November 10, 2016 Presented by: Carolyn Fair - Land Recycling Program PA Department of Environmental Protection 1
Vapor Intrusion Guidance Overview of Vapor Intrusion (VI) Update History of the VI Guidance Implementation of new guidance Comparison of the new guidance to the previous version Importance of considering VI Discussion of key components of new guidance 2
History Vapor Intrusion Guidance Previous VI Guidance from 2004 VI Guidance workgroup formed in 2011 Collaboration of PA DEP and Cleanup Standards Scientific Advisory Board (CSSAB) Published November 19, 2016 60-day Implementation period Effective January 18, 2017 3
New Evaluating Vapor Intrusion the VI Pathway Guidance Implementation of New Guidance For projects mid-stream: Reports approved by the Department will not need to be resubmitted 2004 guidance applies if a final report or remedial action completion report has been received by the Department prior to the effective date of the new guidance New guidance applies if RI of SCR will be submitted following the effective date 4
Evaluating 2004 VI the Guidance VI Pathway Limitations Outdated soil and groundwater VI screening values Limited options if data did not screen out VI Modeling guidance is limited No distinction between petroleum and non-petroleum VI Minimal sampling guidance Addressed only existing buildings 5
What Has Changed Changes *Improved method of calculating screening values accurate, more protective, more aligned with EPA *Added discussion of petroleum VI *More screening options sub-slab and near-source soil gas 6
What Has Changed Changes *Added detailed sampling guidance *Explanation of Site Specific process, combination of standards *Added consideration of future inhabited buildings *Added Modeling guidance 7
Evaluating What Has the Changed VI Pathway Addressing Future Buildings * Planned future buildings treated the same as existing buildings VI must be addressed Use near-source soil gas sampling, AULs, and modeling * Unplanned buildings can be addressed with an activity and use limitation (AUL) at the remediator s discretion; is not required 8
Evaluating Vapor Intrusion the VI Overview Pathway Why do we care about Vapor Intrusion? Volatile substances in soil or groundwater can result in vapor phase intrusion of these substances into inhabited buildings, posing a threat to human health. This guidance details how to evaluate the threat under the Statewide Health Standard (SHS) and the Site-Specific Standard (SSS). 9
Evaluating Vapor Intrusion the VI Overview Pathway What is Vapor Intrusion? VI is a pathway between contamination of a volatile substance and a receptor in a building VI is not a medium like soil and groundwater Primarily associated with volatile organic compounds (VOCs) and some semi-volatile organic compounds (SVOCs) 10
Evaluating Vapor Intrusion the VI Overview Pathway 11
Key Terms Hydrogeologic Zones Potential VI Source Acceptable Soil Point of Application (POA) Separate Phase Liquid (SPL) Proximity Distance Preferential Pathway 12
Evaluating the VI Pathway Hydrogeologic Zones 13
Evaluating Potential the VI VI Source Pathway Potential VI Source Identifies the areas of a site where VI should be addressed Can be addressed through Alternative assessment options Remediation Mitigation AUL 14
Evaluating Acceptable the VI Soil Pathway Acceptable Soil or Soil-like Material Unconsolidated material in the vadose zone above a potential VI source that does not exceed the saturated hydraulic conductivity of sand or air-filled porosity of silt Fill material that is soil-like Soils and fill coarser than sand or with airfilled porosity greater than silt may not be acceptable soil 15
Evaluating Acceptable the VI Soil Pathway Why is acceptable soil important? Presence Impacts the: o use of groundwater screening values o use of vertical proximity distances o application of separation distances for preferential pathways 16
POA Evaluating Point of the Application VI Pathway Location in buildings and in the hydrogeologic zones where screening values are applied POAs guide the selection of sampling locations 17
Evaluating the VI Pathway Point of Application SV SOIL SV GW SV IA SV SS SV NS Soil Screening Value (SV) Groundwater SV Indoor Air SV Sub-slab SV Near-source SV 18
Evaluating the VI Pathway Point of Application Purpose of VI intrusion screening: Determine if a Potential VI source is present Screen pathway from source to receptor 19
SPL Evaluating Separate the Phase VI Pathway Liquid o Comprised of non-aqueous phase liquid (NAPL) o Present in the void space in a contaminated medium (soil or bedrock) o Physically separate from the portion of the substances that are adsorbed onto or diffused into soil, bedrock, water or air 20
Separate Phase Liquid The presence of SPL limits the applicability of screening values, and limits modeling. 21
Evaluating Proximity the Distances VI Pathway Proximity Distance Minimum distance between VI source and a building beyond which the source may not pose a potential unacceptable VI risk. o Applies to current and planned future buildings o Cannot be used if a preferential pathway is present 22
Evaluating Proximity the Distances VI Pathway Horizontal: 30 feet for petroleum substances 100 feet for non-petroleum substances Vertical: 5 feet for petroleum adsorbed-phase or dissolved-phase 15 feet for SPL None for non-petroleum substances 23
Use of Proximity Distances 24
Evaluating Preferential the Pathways VI Pathway Preferential Pathway A natural or man-made feature that enhances vapor migration from a VI source to a building The feature must be close to both the contamination and the building and have sufficient volume in order to be a preferential pathway Two types: External Preferential Pathway Significant Foundation Opening 25
Preferential Pathways Evaluating the VI Pathway 26
Statewide Health Standard VI Evaluation Process Start Here Conceptual Site Model Delineate Contamination DELINEATE POTENTIAL VI SOURCES Soil and Groundwater Screening ALTERNATIVE VI ASSESSMENT OPTIONS Near-Source Soil Gas Screening Sub-Slab Soil Gas Screening Indoor Air Screening Vapor Intrusion Modeling MITIGATION Environmental Covenant SCREEN FOR POTENTIAL VI SOURCES Identify Preferential Pathways Apply Proximity Distances Mitigation, Remediation, or Use of the Site-Specific Standard are Permitted at Any Time ADDRESS CH. 250 REQUIREMENTS No further VI analysis is necessary. REMEDIATION Reevaluate the VI Pathway SITE-SPECIFIC STANDARD 27
Evaluating Mitigation the VI Pathway When Can Mitigation be Done? At any time during the evaluation Eliminates the complete pathway between contamination and the receptor Sub-Slab Depressurization System Vapor Barrier 28
Mitigation System Eliminates the complete pathway between contamination and the receptor 29
Evaluating Remediation the VI Pathway When Can Remediation be Done? At any time during the evaluation Remediation should result in resampling and reevaluation 30
Evaluating the VI Pathway Environmental covenants Required for active mitigation (engineering control) Required for institutional controls for future use: prohibiting new buildings or basements requiring a VI evaluation for new construction requiring mitigation for new construction for the ongoing applicability of an OSHA program 31
VI Sampling Sampling Guidance Detailed guidance for collecting nearsource soil gas, sub-slab soil gas, and indoor air samples Sampling Materials Sampling Locations Number of samples 32
VI Sampling Sampling Guidance At least two locations per building At least two rounds, at least 45 days apart For indoor air, the indoor temperature should be at least 15 F greater than the outdoor temperature 33
Questions? 34