VI Investigations in North Carolina What We ve Learned. Delonda Alexander NC Dry-Cleaning Solvent Cleanup Act Program

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1 VI Investigations in North Carolina What We ve Learned Delonda Alexander NC Dry-Cleaning Solvent Cleanup Act Program

2 Background Approximately 200 sites in program - VI sampling at over 90% of sites - over 500 crawl space/indoor air samples? Near-slab or crawl space collected first if possible - then sub-slab and indoor air samples collected concurrently Exterior soil gas discouraged unreliable predictor only for future use or when access not obtainable

3 Attenuation Factors Commercial exposure EPA database lacking data Large commercial buildings have higher air exchange rates, more competent slabs Looked at Oregon VI Guidance Appendix A and McDonald & Wertz paper (

4 DSCA plotted 330 estimated AFs, 199 derived from the EPA database and 131 from DSCA sampling data (looked at PCE only) Potential use of AFs of 10, 100, and 1,000 were evaluated

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6 If AF of 10 used, 99% of sites would be protected If AF of 100 used, 95% of sites would be protected If AF of 1000 used, 90% of sites would be protected Proposing AF of 100 for commercial exposure (AF of 10 for residential)

7 McDonald & Wertz suggests AF is between 100 and 1000 for buildings with basements or concrete slabs Oregon uses AF of 200 for residential and 1000 for commercial exposures DSCA confirms that appropriate AF between crawl space and indoor air is 1

8 Winter vs. Summer Sampling Worst case conditions winter? EPA data mostly from colder climates Started winter vs. summer sampling to determine if summer in warmer climates might be worst case conditions with house closed up, HVAC running

9 Summer Winter Not enough data yet to make a finding just something to think about Need multiple years of seasonal sampling to see trends and cycles

10 Passive Samplers Use Radiello passive samplers for most crawl space, indoor and outdoor air sampling Sampling device is small, unobtrusive, easy to deploy, cost-effective, can be used for various sampling times up to 30 days, can be placed in tight spaces

11 Contaminants migrate through the diffusive barrier and collect in the absorbent material inside the sampler sampling/uptake rates are known

12 Several studies have been done that show fairly good correlation between Radiellos and Summa canisters analyzed w/ TO-15 DSCA Program starts off with 1 st VI sampling event using Summa and Radiello side-by-side to make sure there is good correlation

13 PCE TCE 24-Hour Summa EPA TO15 (SIM) ug/m Hour Radiello GC/MS Application #48 ug/m Hour Ultra III EPA TO-17 ug/m3 >260S hour Summa TO-15 (SIM) ug/m J 8 hour Radiello ATL-48 ug/m3 35 <3 24 hour Summa TO-15 ug/m J 24 hour Radiello ATL-48 ug/m3 27 <1 24 hour Summa EPA TO15 (SIM) ug/m hour Radiello ATL GC App #48 ug/m3 2.2 < hour Summa EPA TO15 (SIM) ug/m hour Radiello ATL GC App #48 ug/m3 4.5 <1.0

14 Recent presentation given at AEHS, San Diego, 20 March 2012 by Todd McAlary (Geosyntec) et. al. showed comparisons between different passive samplers ( 12%20compressed_rev1.pdf) Looked at ATD tubes, Radiello, SKC Ultra II, 3M OVM 3500 and Waterloo Membrane sampler

15 3M OVM 3500 ATD tubes 3 M O V M Waterloo Membrane Sampler TM

16 Study findings: Use of passive samplers cuts costs about 50% over using Summas Strong correlation with Summas Can be sensitive to wind, rain, temp. Simpler protocols less operator error Some compounds challenging Different samplers have pros and cons

17 Use of Radon for Attenuation DSCA Program using measurement of radon as a useful tool in determining attenuation factors and demonstrating indoor sources vs. VI Collect radon gas concentrations concurrently in sub-slab and indoor air

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19 Active Perc dry-cleaner 2 adjacent tenant spaces affected - indoor air sampled in tenant spaces and DC: 6/10/10 8 hr Radiello while DC machines in operation 6/13/10 8 hr Radiello while DC machines and facility not in operation 10/4-10/8/10 5 day Radiello while DC machines in operation

20 Atlantic Realty Dairy Queen Dry-Cleaners Sub-slab gas ,000 6/10/10 (operating) 6/13/10 (not operating) 10/4-10/8/10 (operating) Results for PCE ug/m 3

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22 Radon in sub-slab (pci/l) Radon in indoor air (pci/l) AF using radon AF using subslab/indoor air Atlantic Realty Dairy Queen

23 To show that operating dry-cleaner was affecting indoor air in adjacent spaces, pressurization tests and infrared thermographic survey conducted Pressurization tests determine amount of air leakage between the dry-cleaner and adjacent spaces Infrared survey identifies points of air leakage between spaces

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25 Where s the source? Former perc dry-cleaner now empty - impacted adjacent tenant Ogden Optical Indoor air sampling in Ogden Optical risk exceeds 10E-04 mitigation necessary Installed sub-slab depressurization system risk still too high install second extraction point risk still too high

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27 Must be another source area subslab depressurization system pulling vapors Conducted Modified Active Gas Survey (MAGS) in former dry-cleaner Vacuum pressure is induced in test wells magnehelic gauges collect measurements used to determine radius of influence for each well

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29 Borings used to characterize and confirm potential source area 60 tons of contaminated soil removed SVE system installed in former dry-cleaner to pull remaining vapors away from Ogden Optical With both systems running in Ogden Optical and former dry-cleaner risk is within acceptable range

30 Drop-off/pick-up Site Perc cleaner stopped operating in 1998 and became drop-off/pick-up store Indoor air in adjacent tenant space exceeds acceptable risk Soil gas to indoor air attenuation factor in adjacent space ranges from 1.3 to indicating indoor source

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32 Garments removed air in both spaces flushed with fans then closed up until next morning 3 indoor air samples collected from dry cleaner and adjacent space 8-hr 1 st hour of the 8-hr sample Last hour of the 8-hr sample

33 Before garments removed, PCE results In the drop-off/pick-up store 560 ug/m 3 In the adjacent space 48 ug/m 3 After garments removed, PCE results in the drop-off/pick-up store 8-hr : 0.7 ug/m 3 1st hr : 0.6 ug/m 3 Last hr : 0.83 ug/m 3 In the adjacent space all results BDL

34 QUESTIONS?