PA Vapor Intrusion Guidance

Size: px

Start display at page:

Download "PA Vapor Intrusion Guidance"

Sheena Hubbard
6 years ago
Views:

1 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

guidance Comparison of the new guidance to the previous version

2 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

3 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, day Implementation period Effective January 18,

4 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

5 Evaluating 2004 VI the Guidance VI Pathway Limitations Outdated soil and groundwater VI screening values Limited options if data did not screen out VI Modeling guidance is limited No distinction between petroleum and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

6 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

7 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

8 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

9 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

10 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

11 Evaluating Vapor Intrusion the VI Overview Pathway 11

12 Key Terms Hydrogeologic Zones Potential VI Source Acceptable Soil Point of Application (POA) Separate Phase Liquid (SPL) Proximity Distance Preferential Pathway 12

13 Evaluating the VI Pathway Hydrogeologic Zones 13

14 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

15 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

16 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

17 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

18 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

19 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

20 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

21 Separate Phase Liquid The presence of SPL limits the applicability of screening values, and limits modeling. 21

22 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

23 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

24 Use of Proximity Distances 24

25 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

26 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

27 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

28 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

29 Mitigation System Eliminates the complete pathway between contamination and the receptor 29

30 Evaluating Remediation the VI Pathway When Can Remediation be Done? At any time during the evaluation Remediation should result in resampling and reevaluation 30

31 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

32 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

apart For indoor air, the indoor temperature should

33 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

34 Questions? 34

August Vapor Intrusion Guidance FAQs

August Vapor Intrusion Guidance FAQs August 2017 2017 Vapor Intrusion Guidance FAQs Topics: A. General B. Effect of New Guidance on In-Process Sites C. Future Use of Site D. Modeling E. Off-Site Properties F. Preferential Pathways G. Proximity