A presentation at the 2015 Midwest Environmental Compliance Conference, May 13-14, 2015, Overland Park, KS

1. Importance of
Understanding Potential
Background Sources in VI
Evaluations
Gina Plantz
Rich Rago

2. Collecting Field Data- you may only get one shot
• Take opportunity to collect as much information as possible
• Document procedures and keep records
• Include shut-in tests for soil gas sampling
• Collect pressure differential data and review with concurrent
data for barometric pressure
• Make careful observations of building slabs, especially when
locating sub-slab samples
• Do thorough building surveys
• Take lots of photographs

3. Data Reduction and Multiple Lines of Evidence
(MLE)
• Simple comparison of data to screening levels may result in
complicated matters and incorrect decision-making
• Consider the Conceptual Site Model for VI in planning
investigations
• Consider MLEs
• Contaminant ratios
• Modeled concentrations
• Building pressure differentials and meteorological data
• Contaminant trends
• Background sources identified

4. EPA Region 9 Guidelines, Item #1
(30 June 2014 Clarification)
“[T]he health protective risk range for both accelerated response
actions and long-term exposures become truncated to:
• 0.5 – 2 µg/m3 for residential exposures and
• 3 – 8 µg/m3 for 8-hour/day commercial/industrial exposures.”

5. Implementation of Interim Measures to Mitigate
TCE Short-term Exposure
• Increasing building pressurization and/or ventilation
• Sealing potential conduits where vapors may be entering the
building
• Treating indoor air (carbon filtration, air purifiers)
• Installing and operating engineered exposure controls (sub-
slab/crawlspace, depressurization systems)
• Temporarily relocating occupants

6. Indoor Air Background
• “One of the most difficult facets of investigating VI is the interpretation of the available
information and the subsequent conclusions reached on the completeness of the pathway. This
task is complicated by the impact of background contaminant sources on the overall indoor air
quality.”
• “…..the most critical point is in the assessment of indoor air data as it relates to
background contamination.” - NJDEP 2012

7. Relevance of Indoor Air Background
• Potential overlap of site contaminants from subsurface sources and personal,
indoor, and ambient sources
• Requires careful consideration in VI assessments
• VOCs are very common to personal, indoor air (Gordon, et al, 1999; Clayton,
et al, 1999; Kinney, et al, 2002; Sexton, et al, 2004; Bradley, et al, 2004,
RIOPA, 2005, Rago, et al, 2007; EPRI, 2007; MT DEQ, 2012), and ambient
sources (EPA, 1988; EPA, 2000)
• USEPA has developed a database and technical paper on national
indoor air background levels.
• For more information:
• “The Inside Story: A Guide to Indoor Air Quality”
http://www.epa.gov/iaq/pubs/insidest.html
• Background paper, Dawson et al, June 2011
• Summaries of recent studies

8. Relevance of Indoor Air Background (continued)
• Common VOCs identified in new (finished and operational, but
unoccupied) pre-fabricated and site-built houses (Hodgson, et
al, 2000)
• Higher background levels of VOCs have been observed in homes
with attached garages (Kurtz, 2004; Graham, et al, 2004;
McCafferty, 2006)
• VOCs are also commonly encountered in commercial buildings
(Daisey, et al, 1994; Girman, et al, 1999) and schools (Adgate, et
al, 2004)

9. Limitations of Existing Literature Data for Non-
residential Buildings
• Older data sets
• Inconsistent sampling and analytical methods
• Higher detection limits
• Varying objectives, methodologies, geographies, statistics
• Consumer products and ambient air quality have changed over
time (e.g., 1,2-dichloroethane)
• No data on petroleum “hydrocarbon ranges”

10. Importance of New Study
• Information on indoor air background is critical in VI
investigations
• Little recent literature data exists on office buildings and schools
• Practitioners and Regulators may default to residential criteria
which may or may not be appropriate
• Compare TO-15 and TO-17 data for canisters and passive
samplers

11. Summary of Selected VOCs (µg/m3)
Preliminary data; N=60
Compound
Frequency of
Detection
Minimum
(ug/m3)
Maximum
(ug/m3)
1,2-Dichloroethane 70% 0.081 0.498
Trichloroethene 15% 0.107 115
Tetrachloroethene 75% 0.136 9.02
Benzene 90% 0.319 24.8
Toluene 98% 1.01 242
Ethylbenzene 98% 0.109 45.6
p/m-Xylene 98% 0.243 157
o-Xylene 98% 0.104 51.3
C5-C8 Aliphatics 95% 2 3000
C9-C12 Aliphatics 85% 14 990
C9-C10 Aromatics 12% 10 120

12. Trichloroethylene
N=100Preliminary data; N=37

13. Some Observations of Preliminary Results
• Tetrachloroethylene detected in 75% of office/school samples
• Concentrations ranging from 0.136 ug/m3 to 9.02 ug/m3
• Benzene detected in 90% of office/school samples
• Concentrations ranging from 0.319 ug/m3 to 24.8 ug/m3
• Trichloroethylene detected in 9 office samples
• Ranging to 115 ug/m3
• 1,2-dichloroethane detected in 70% of office samples and 60%
of school samples
• Concentrations ranging from 0.081 ug/m3 to 0.498 ug/m3

14. Summary
• Indoor air background is building-specific and commercial
product formulations can and do change
• Carefully review background studies for focus, relationships, and
ranges
• Understanding background data can be of strategic importance
in vapor intrusion data review, focusing investigations, mitigation
decision making, and risk communication