Soil Vapor Intrusion Approach â Wisconsin Site
Soil Vapor Intrusion Results of Field Investigations at Two MGP Sites Jim Lingle Senior Project Manager MGP 2012 Fourth International Symposium and Exhibition on the Redevelopment of Manufactured Gas Plant Sites March 28, 2012
Approach – Wisconsin Site • Description: Previously remediated vacant lot • Passive Survey using Gore Modules™ • Capacitance-type continuous reading soil moisture sensors • Soil and groundwater samples • PCR testing for gene marker evaluation of soil microbes • High resolution vertical soil vapor profiles (4 levels) • Comparison of TO-15 (Summa cans), TO-17 (adsorption tubes), and 8260 (250 ml canisters) © 2012 Electric Power Research Institute, Inc. All rights reserved.
• Soil gas forensics using PIANO groupings (paraffins, isoparaffins, aromatics, naphthenes & olefins)
• One year temporary cap to monitor soil gas over time • Modeling soil gas concentrations
2
1
Approach – Connecticut Site • Description: Active office/garage over former MGP site • Soil and groundwater samples • Indoor and outdoor air measurements • Subsurface soil gas measurements • Differential building pressure monitoring • Fingerprinting using PIANO compounds
© 2012 Electric Power Research Institute, Inc. All rights reserved.
3
Observations from SVI Investigations - WI • Deep near-source soil vapor is more stable than shallow soil vapor • PIANO forensics showed MGP hydrocarbons are primarily aromatic • Aromatic hydrocarbons showed greater attenuation (easier to degrade) than aliphatic compounds • BTEX concentrations were highest, trimethylbenzene moderate, and naphthalene compounds low
• Soil gas concentrations were reduced three orders of magnitude a few feet above the residual source Water Level Transducer in Well
Moisture Probes
Soil Gas Wells Groundwater Well
High Resolution Soil Gas Monitoring © 2012 Electric Power Research Institute, Inc. All rights reserved.
4
2
Observations from SVI Investigations - WI 50’ by 50’ LDPE liner with 6” soil above
• Capping study showed O2 levels were less than 1% after several months, but benzene increased only slightly • An oxygen shadow occurred following placement of the temporary cap. However, no O2 recharge occurred from wind over the flat geomembrane • Methane concentration built up under cap. The source was uncertain (organic river bottom, high pressure gas lines, or anaerobic degradation of NAPL)
G3A1
GW
Moisture1
Study Area
Moisture2 GW
H2A1
5
© 2012 Electric Power Research Institute, Inc. All rights reserved.
Observations from SVI Investigations - CT • Infiltrating rainwater can result in significant variation in soil gas • Building differential pressure was generally negative • Forensic analysis of PIANO compounds showed fresh gasoline was being pushed in to the subslab vapor High Values
Low Values
0.025 0.015 0.005 -0.005 -0.015 -0.025 -0.035
/14
/12
0:0
0
:36 12
/12
21
:12 /13 12
/13
/12
19
:48 16 12
/13 12
Time
/12
14 /12 /13 12
12
/13
/13
/12
/12
12
:24
:00
6 9:3
2 7:1 12
/13 12
/12
© 2012 Electric Power Research Institute, Inc. All rights reserved.
/12
4:4
4
/13 12
/13
/12
2:2
0:0 12
/12 /13 12
8
-0.045 0
Differential Pressure ("H20)
Building Differential Pressure - 5 Minute Intervals
6
3
Conclusions from SVI Investigations - WI • Gore Modules™ were effective in screening shallow (3 foot) soil gas hot spots • High resolution vertical soil gas wells were effective in identifying vapor biodegradation and attenuation • Ancillary tests (headspace vapor tests, soil organic carbon, soil physical properties, etc.) are important in developing a conceptual site model • Capacitance soil moisture sensors provide useful waterfilled porosity data © 2012 Electric Power Research Institute, Inc. All rights reserved.
BTEX mass
• Real-time PCR testing for microbial genes capable of aerobic biodegradation are useful and relatively low cost (consider backfill material) 7
Conclusions from SVI Investigations - WI • TO-15 and TO-17 soil vapor tests were generally comparable during most sample events • Method 8260 is lower cost but has higher detection limits and was less consistent than TO-15 or TO-17. It may be suitable for screening work • TO-17 is more challenging to use in the field than TO-15
© 2012 Electric Power Research Institute, Inc. All rights reserved.
8
4
Conclusions from SVI Investigations - WI • Elevated CO2 and sharply reduced O2 indicated aerobic biodegradation • Good agreement between model predictions and measured soil gas concentrations • Soil gas modeling should include biodegradation demand from methane
© 2012 Electric Power Research Institute, Inc. All rights reserved.
9
Conclusions from Investigations - CT • Soil gas caused no significant impact to indoor air quality at the CT site • High oxygen levels, wet finegrained soils with high organic content and aerobic biodegradation contributed to low soil gas concentrations • Forensic analysis (PIANO compounds) showed incomplete pathway for SVI • Differential pressure can be a useful low cost secondary line of evidence
© 2012 Electric Power Research Institute, Inc. All rights reserved.
10
5
EPRI SVI Research • “Results of Field-Based Soil Vapor Intrusion (SVI) Research at Two MGP Sites and Implications for SVI Assessment”, (EPRI Report 1021819, December, 2011) • “Residential Indoor Air Background Data: A Comparison of Indoor Air Results from Vapor Intrusion Studies at MGP Sites in New York” (EPRI Report 1012590, March, 2007) • “Assessment of Vapor Intrusion at MGP Sites: Review of Current Knowledge, Practices, and Proposed Field-Based Research Program” (EPRI Report 1014087, March, 2008)
© 2012 Electric Power Research Institute, Inc. All rights reserved.
11
Additional EPRI-peer reviewed SVI Research • “Examination of a Manufactured Gas Plant Site Database for Soil Vapor Intrusion - what the data are telling us,” EPRI MGP Symposium, San Antonio, Texas, January 27-29, 2010, Rago, Richard, Plantz, Gina, Wright-Ng, Kristen, and Lingle, James – IA background greatly influenced the results from the MGP VI investigations – database alphas may be consistent with site alphas • “Comparison of Observed VI Attenuation Factors at Former MGP Sites to the US EPA’s VI Database Attenuation Factors,” MGP 2008 Symposium, Mystic, CT, September 2008, Plantz, Gina, Blazicek, Tracy, and Rago, Richard – Data from multiple MGP sites pooled – Data also examined in consideration of 2,989 paired measurements presented in the EPA VI Database © 2012 Electric Power Research Institute, Inc. All rights reserved.
12
6
Thank you! Contributing Authors and collaborators • Ian Hers, Ed Murphy (Golder Associates) • Frank Dombrowski (We Energies) • Bill Hoynack (Northeast Utilities) • Rich Rago (Haley & Aldrich) Project Funders: • Alliant Energy, Consolidated Edison Co. of New York, Exelon, FirstEnergy, New York State Electric and Gas, NiSource, Northeast Utilities, Public Service Electric and Gas
© 2012 Electric Power Research Institute, Inc. All rights reserved.
13
7
Approach – Wisconsin Site • Description: Previously remediated vacant lot • Passive Survey using Gore Modules™ • Capacitance-type continuous reading soil moisture sensors • Soil and groundwater samples • PCR testing for gene marker evaluation of soil microbes • High resolution vertical soil vapor profiles (4 levels) • Comparison of TO-15 (Summa cans), TO-17 (adsorption tubes), and 8260 (250 ml canisters) © 2012 Electric Power Research Institute, Inc. All rights reserved.
• Soil gas forensics using PIANO groupings (paraffins, isoparaffins, aromatics, naphthenes & olefins)
• One year temporary cap to monitor soil gas over time • Modeling soil gas concentrations
2
1
Approach – Connecticut Site • Description: Active office/garage over former MGP site • Soil and groundwater samples • Indoor and outdoor air measurements • Subsurface soil gas measurements • Differential building pressure monitoring • Fingerprinting using PIANO compounds
© 2012 Electric Power Research Institute, Inc. All rights reserved.
3
Observations from SVI Investigations - WI • Deep near-source soil vapor is more stable than shallow soil vapor • PIANO forensics showed MGP hydrocarbons are primarily aromatic • Aromatic hydrocarbons showed greater attenuation (easier to degrade) than aliphatic compounds • BTEX concentrations were highest, trimethylbenzene moderate, and naphthalene compounds low
• Soil gas concentrations were reduced three orders of magnitude a few feet above the residual source Water Level Transducer in Well
Moisture Probes
Soil Gas Wells Groundwater Well
High Resolution Soil Gas Monitoring © 2012 Electric Power Research Institute, Inc. All rights reserved.
4
2
Observations from SVI Investigations - WI 50’ by 50’ LDPE liner with 6” soil above
• Capping study showed O2 levels were less than 1% after several months, but benzene increased only slightly • An oxygen shadow occurred following placement of the temporary cap. However, no O2 recharge occurred from wind over the flat geomembrane • Methane concentration built up under cap. The source was uncertain (organic river bottom, high pressure gas lines, or anaerobic degradation of NAPL)
G3A1
GW
Moisture1
Study Area
Moisture2 GW
H2A1
5
© 2012 Electric Power Research Institute, Inc. All rights reserved.
Observations from SVI Investigations - CT • Infiltrating rainwater can result in significant variation in soil gas • Building differential pressure was generally negative • Forensic analysis of PIANO compounds showed fresh gasoline was being pushed in to the subslab vapor High Values
Low Values
0.025 0.015 0.005 -0.005 -0.015 -0.025 -0.035
/14
/12
0:0
0
:36 12
/12
21
:12 /13 12
/13
/12
19
:48 16 12
/13 12
Time
/12
14 /12 /13 12
12
/13
/13
/12
/12
12
:24
:00
6 9:3
2 7:1 12
/13 12
/12
© 2012 Electric Power Research Institute, Inc. All rights reserved.
/12
4:4
4
/13 12
/13
/12
2:2
0:0 12
/12 /13 12
8
-0.045 0
Differential Pressure ("H20)
Building Differential Pressure - 5 Minute Intervals
6
3
Conclusions from SVI Investigations - WI • Gore Modules™ were effective in screening shallow (3 foot) soil gas hot spots • High resolution vertical soil gas wells were effective in identifying vapor biodegradation and attenuation • Ancillary tests (headspace vapor tests, soil organic carbon, soil physical properties, etc.) are important in developing a conceptual site model • Capacitance soil moisture sensors provide useful waterfilled porosity data © 2012 Electric Power Research Institute, Inc. All rights reserved.
BTEX mass
• Real-time PCR testing for microbial genes capable of aerobic biodegradation are useful and relatively low cost (consider backfill material) 7
Conclusions from SVI Investigations - WI • TO-15 and TO-17 soil vapor tests were generally comparable during most sample events • Method 8260 is lower cost but has higher detection limits and was less consistent than TO-15 or TO-17. It may be suitable for screening work • TO-17 is more challenging to use in the field than TO-15
© 2012 Electric Power Research Institute, Inc. All rights reserved.
8
4
Conclusions from SVI Investigations - WI • Elevated CO2 and sharply reduced O2 indicated aerobic biodegradation • Good agreement between model predictions and measured soil gas concentrations • Soil gas modeling should include biodegradation demand from methane
© 2012 Electric Power Research Institute, Inc. All rights reserved.
9
Conclusions from Investigations - CT • Soil gas caused no significant impact to indoor air quality at the CT site • High oxygen levels, wet finegrained soils with high organic content and aerobic biodegradation contributed to low soil gas concentrations • Forensic analysis (PIANO compounds) showed incomplete pathway for SVI • Differential pressure can be a useful low cost secondary line of evidence
© 2012 Electric Power Research Institute, Inc. All rights reserved.
10
5
EPRI SVI Research • “Results of Field-Based Soil Vapor Intrusion (SVI) Research at Two MGP Sites and Implications for SVI Assessment”, (EPRI Report 1021819, December, 2011) • “Residential Indoor Air Background Data: A Comparison of Indoor Air Results from Vapor Intrusion Studies at MGP Sites in New York” (EPRI Report 1012590, March, 2007) • “Assessment of Vapor Intrusion at MGP Sites: Review of Current Knowledge, Practices, and Proposed Field-Based Research Program” (EPRI Report 1014087, March, 2008)
© 2012 Electric Power Research Institute, Inc. All rights reserved.
11
Additional EPRI-peer reviewed SVI Research • “Examination of a Manufactured Gas Plant Site Database for Soil Vapor Intrusion - what the data are telling us,” EPRI MGP Symposium, San Antonio, Texas, January 27-29, 2010, Rago, Richard, Plantz, Gina, Wright-Ng, Kristen, and Lingle, James – IA background greatly influenced the results from the MGP VI investigations – database alphas may be consistent with site alphas • “Comparison of Observed VI Attenuation Factors at Former MGP Sites to the US EPA’s VI Database Attenuation Factors,” MGP 2008 Symposium, Mystic, CT, September 2008, Plantz, Gina, Blazicek, Tracy, and Rago, Richard – Data from multiple MGP sites pooled – Data also examined in consideration of 2,989 paired measurements presented in the EPA VI Database © 2012 Electric Power Research Institute, Inc. All rights reserved.
12
6
Thank you! Contributing Authors and collaborators • Ian Hers, Ed Murphy (Golder Associates) • Frank Dombrowski (We Energies) • Bill Hoynack (Northeast Utilities) • Rich Rago (Haley & Aldrich) Project Funders: • Alliant Energy, Consolidated Edison Co. of New York, Exelon, FirstEnergy, New York State Electric and Gas, NiSource, Northeast Utilities, Public Service Electric and Gas
© 2012 Electric Power Research Institute, Inc. All rights reserved.
13
7
