Alternative Sampling Methods Implemented at North Carolina Dry-Cleaning Solvent Act (DSCA) Program Sites: A Compilation of Noteworthy Data

Transcription

1 Alternative Sampling Methods Implemented at North Carolina Dry-Cleaning Solvent Act (DSCA) Program Sites: A Compilation of Noteworthy Data Genna Olson, P.G., Cardno ATC Delonda Alexander, NCDENR DSCA Program January 23, 2014

2 Topics of Discussion Passive versus active indoor air sampling Collection of soil gas samples from groundwater monitoring wells Summer versus winter trends in indoor air concentrations

3 PASSIVE VERSUS ACTIVE INDOOR AIR SAMPLING

4 Active Sampling Using Summa Canisters Regulators control the flow of air into the evacuated canister Commonly 8-hour nonresidential and 24-hour residential

5 Passive Diffusion Sampling Using Radiello 130 Gaseous molecules adsorbed onto activated charcoal cartridge Compounds recovered through solvent extraction or thermal desorption Chemical uptake rate is key Adsorbent Cartridge Diffusive Body

6 Pros of Radiello Passive Diffusion Samplers Less Expensive Radiello ~$150/sample Summa ~$200 $250/sample Higher shipping costs for Summas Higher replacements costs for Summas

7 Pros of Radiello Passive Diffusion Samplers (continued) Longer sampling timeframes (up to 30 days) Can achieve low detection limits, but takes more time for some compounds (1 day for TCE, 3 days for benzene) No need to worry about maintaining Summa vacuum Compact and unobtrusive

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9 Cons of Radiello Passive Diffusion Samplers Less widely accepted by regulators Less reliable for some chemicals (notably vinyl chloride) May be sensitive to moisture, wind, and/or temperature variations

10 Active Versus Passive Sampling Data Collection Concurrent Summas and Radiellos collected at six sites Same locations and timeframes 16 samples, 37 paired concentrations, majority, also TCE, and BTEX

11 1000 Summa vs Radiello Indoor Air Concentrations Radiello Result (µg/m 3 ) TCE Benzene Toluene Ethylbenzene Xylenes Summa Result (µg/m 3 )

12 Summa vs Radiello Indoor Air Concentrations Constituent Number of Detections R 2 Value TCE 1 NA Benzene Toluene Ethylbenzene Xylenes All

13 COLLECTION OF SOIL GAS SAMPLES FROM GROUNDWATER MONITORING WELLS

14 Collection of Soil Gas Samples from Conventional Groundwater Monitoring Wells

15 Collection of Soil Gas Samples from Conventional Groundwater Monitoring Wells Latest guidance recommends collecting exterior soil gas samples directly above capillary fringe

16 Collection of Soil Gas Samples from Conventional Groundwater Monitoring Wells

17 Collection of Soil Gas Samples from Conventional Groundwater Monitoring Wells

18 Collection of Soil Gas Samples from Conventional Groundwater Monitoring Wells Benefit Less $$$ Average cost of $3,500 for installation of four soil gas points

19 Collection of Soil Gas Samples from Conventional Groundwater Monitoring Wells Property Boundary Benefit Convenient for risk-based closures to define land use controls by property?

20 Comparison of Construction Details Typical Soil Gas Point Typical Monitoring Well ¼ Teflon tubing Bentonite/ grout seal Grout seal 1 or 2 PVC casing 6 stainless steel sampling implant Filter sand Bentonite seal Filter sand 1 or 2 PVC screen

21 Purging Concerns Purging is important, but difficulties with large purge volume Ex. 20 DTW, 2 well, 8 boring, 3 volumes = 70,000 ml, at 200 ml/min = 6 hours Time = money Concerns with migration of soil gas from less impacted areas CA DTSC allows higher purge rate, but pressure 100 H 2 O must be maintained

22 Comparative soil gas samples collected from six sets of nested monitoring wells and soil gas monitoring points at three sites

23 Similar Sampling Depths Targeted Depth In Feet

24 Soil Gas Sampling Procedures For traditional soil gas points, purged 3 volumes at 200 ml/min For monitoring wells, purged 3 volumes at 3,500 ml/min while maintaining pressure 100 H 2 O (per CA guidance) Helium used as leak check compound Samples collected in Summa canisters and analyzed by EPA Method TO-15

25 X-axis: Concentration (µg/m 3 ), Y-axis: Depth (feet) Soil gas points in red, monitoring wells in blue Soil Gas Sampling Results TS SGMP-6/MW , TS SGMP-6/MW- 15 TCE TS SGMP-6/MW-15 cis-1,2-dce TS SGMP-5/MW- 16S , R SGMP/MW-3 1 1,000 1,000, TS SGMP-10/MW-4 1 1,000 1,000, F SGMP-10/MW- 16S TS SGMP-9/MW-8S 1 100

26 X-axis: Concentration (µg/m 3 ), Y-axis: Depth (feet) Soil gas points in red, monitoring wells in blue Soil Gas Sampling Results TS SGMP-6/MW-15 : : 3, , : 1, TS SGMP-6/MW- 15 TCE TS SGMP-6/MW-15 cis-1,2-dce TS SGMP-5/MW- 16S , R SGMP/MW-3 1 1,000 1,000, TS SGMP-10/MW-4 1 1,000 1,000, F SGMP-10/MW- 16S TS SGMP-9/MW-8S 1 100

27 X-axis: Concentration (µg/m 3 ), Y-axis: Depth (feet) Soil gas points in red, monitoring wells in blue Soil Gas Sampling Results TS SGMP-6/MW , TS SGMP-6/MW- 15 TCE TS SGMP-6/MW-15 cis-1,2-dce TS SGMP-5/MW- 16S , R SGMP/MW-3 1 1,000 1,000, TS SGMP-10/MW-4 1 1,000 1,000, F SGMP-10/MW- 16S TS SGMP-9/MW-8S 1 100

28 X-axis: Concentration (µg/m 3 ), Y-axis: Depth (feet) Soil gas points in red, monitoring wells in blue Soil Gas Sampling Results TS SGMP-6/MW , TS SGMP-6/MW- 15 TCE TS SGMP-6/MW-15 cis-1,2-dce TS SGMP-5/MW- 16S , R SGMP/MW-3 1 1,000 1,000, TS SGMP-10/MW-4 1 1,000 1,000, F SGMP-10/MW- 16S TS SGMP-9/MW-8S 1 100

29 X-axis: Concentration (µg/m 3 ), Y-axis: Depth (feet) Soil gas points in red, monitoring wells in blue Soil Gas Sampling Results TS SGMP-6/MW , TS SGMP-6/MW- 15 TCE TS SGMP-6/MW-15 cis-1,2-dce TS SGMP-5/MW- 16S , R SGMP/MW-3 1 1,000 1,000, TS SGMP-10/MW-4 1 1,000 1,000, F SGMP-10/MW- 16S TS SGMP-9/MW-8S 1 100

30 Purge Volume Testing Results Well TS MW-8S Volumes Purged Prior (µg/m 3 ) ppb-rae Result (µg/m 3 ) F MW-16S F SGMP-10/MW-16S < SGMP-9/MW-8S - RESAMPLING ,000 Soil gas points in red, initial monitoring well sampling in blue, second monitoring well sampling in green.

31 Testing for Loss During Tedlar to Summa Transfer Well Sample Collection Method (µg/m 3 ) Straight Summa 46,000 TW MW-4 Tedlar Bag Transferred to Summa 97,000 CA DTSC allows a hold time of 6 hours for Tedlar bags

32 Soil Gas Sampling Results Monitoring Well (ug/m 3 ) R 2 = TCE cis-1,2-dce Soil Gas Monitoring Point (µg/m 3 )

33 Soil Gas Sampling Results 1,000, ,000 Concentration (µg/m 3 ) 10,000 1, NC Non-Residential SL NC Residential SL 10 1 Each vertical line represents a different sampling location

34 SUMMER VERSUS WINTER TRENDS IN INDOOR AIR CONCENTRATIONS

35 Weather in the South Don t open the door, you ll let the air out! What season is it?

36 Summer vs Winter Sampling Data Charlotte, NC Site Summer/winter sampling in 1 residence over 2 years (4 samples) Summer/winter sampling in on-site building over 3 years (2 locations, 7 samples each) Durham, NC Site Periodic sampling in 2 residences over 3 years (6 samples) Denver, NC Site Summer/winter sampling in 1 residence over 3 years (5 samples)

37 Summer vs Winter Indoor Air Concentration Trends Charlotte, NC Site 100 Concentration (µg/m 3 ) 10 1 Highest concentrations detected during summer temps (70-84⁰F) at all locations Mean Outside Temperature (⁰F) On-Site #1 On-Site #2 Residence TCE

38 Summer vs Winter Indoor Air Concentration Trends Charlotte, NC Site 100 Concentration (µg/m 3 ) 10 1 Trend of increasing concentrations with increasing temperature at all locations On-Site #1 On-Site #2 Residence Mean Outside Temperature (⁰F) TCE

39 Summer vs Winter Indoor Air Concentration Trends Durham, NC Site Concentration (µg/m 3 ) Mean Outside Temperature (⁰F) Highest concentrations detected at 54⁰F in one house and at 69⁰F in second house Residence #1 Residence #2 TCE cis-1,2-dce

40 Concentration (µg/m 3 ) Summer vs Winter Indoor Air Concentration Trends Durham, NC Site Mean Outside Temperature (⁰F) Trend of increasing concentrations with increasing temperature for and TCE at both locations Decreasing trend for cis-1,2-dce at one location Residence #1 Residence #2 TCE cis-1,2-dce

41 Summer vs Winter Indoor Air Concentration Trends Denver, NC Site 10.0 Concentration (µg/m 3 ) 1.0 Highest concentration detected at 80⁰F Residence Mean Outside Temperature (⁰F)

42 Summer vs Winter Indoor Air Concentration Trends Denver, NC Site 10.0 Concentration (µg/m 3 ) 1.0 Trend of increasing concentrations with increasing temperature Mean Outside Temperature (⁰F) Residence

43 Summer vs Winter Trends in Indoor Air Concentrations Compiled concentration/temperature data for all DSCA sites sampled by ATC. Filtering to remove sites with active drycleaning, mitigation or remediation, and <2 sampling events. Resulting data set: 12 sites 15 structures 134 concentrations (, TCE, cis-1,2- DCE)

44 Summer vs Winter Indoor Air Concentration Trends Comprehensive Data Set 100 Concentration (µg/m 3 ) Ummm Temperature (⁰F)

45 Summer vs Winter Indoor Air Concentration Trends Comprehensive Data Set 100 Concentration (µg/m 3 ) trendlines 76% upward (red) 24% downward (blue) Mean Outside Temperature (⁰F)

46 Summer vs Winter Indoor Air Concentration Trends Comprehensive Data Set 100 NC Non-Residential SL 10 NC Residential SL Concentration (µg/m 3 ) Each vertical line represents a different sampling location

47 SUMMARY > Radiello passive diffusion sampling data compares well with Summa sampling data, and offers advantages of lower cost, longer sampling timeframes, and unobtrusive appearance. > Collection of soil gas samples from monitoring wells may represent a cost saving alternative to installation of new soil gas points. > Winter may not represent worst-case indoor air concentrations.