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
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
PASSIVE VERSUS ACTIVE INDOOR AIR SAMPLING
Active Sampling Using Summa Canisters Regulators control the flow of air into the evacuated canister Commonly 8-hour nonresidential and 24-hour residential
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
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
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
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
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
1000 Summa vs Radiello Indoor Air Concentrations Radiello Result (µg/m 3 ) 100 10 TCE Benzene Toluene Ethylbenzene Xylenes 1 0.1 0.1 1 10 100 1000 Summa Result (µg/m 3 )
Summa vs Radiello Indoor Air Concentrations Constituent Number of Detections R 2 Value 16 0.964 TCE 1 NA Benzene 3 0.994 Toluene 11 0.990 Ethylbenzene 3 0.999 Xylenes 3 0.999 All 37 0.967
COLLECTION OF SOIL GAS SAMPLES FROM GROUNDWATER MONITORING WELLS
Collection of Soil Gas Samples from Conventional Groundwater Monitoring Wells
Collection of Soil Gas Samples from Conventional Groundwater Monitoring Wells Latest guidance recommends collecting exterior soil gas samples directly above capillary fringe
Collection of Soil Gas Samples from Conventional Groundwater Monitoring Wells
Collection of Soil Gas Samples from Conventional Groundwater Monitoring Wells
Collection of Soil Gas Samples from Conventional Groundwater Monitoring Wells Benefit Less $$$ Average cost of $3,500 for installation of four soil gas points
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?
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
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
Comparative soil gas samples collected from six sets of nested monitoring wells and soil gas monitoring points at three sites
Similar Sampling Depths Targeted Depth In Feet 0 10 20 30 40 50 25-26 32
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
X-axis: Concentration (µg/m 3 ), Y-axis: Depth (feet) Soil gas points in red, monitoring wells in blue Soil Gas Sampling Results 28 30 32 34 35 36 37 TS SGMP-6/MW-15 1 100 10,000 35 37 TS SGMP-6/MW- 15 TCE 1 10 100 35 37 TS SGMP-6/MW-15 cis-1,2-dce 1 100 35 37 39 TS SGMP-5/MW- 16S 1 100 10,000 20 21 22 23 24 25 26 28 R SGMP/MW-3 1 1,000 1,000,000 24.5 25 25.5 26 26.5 TS SGMP-10/MW-4 1 1,000 1,000,000 12 14 16 18 20 22 24 26 28 30 F SGMP-10/MW- 16S 1 10 100 24 25 26 28 30 32 TS SGMP-9/MW-8S 1 100
X-axis: Concentration (µg/m 3 ), Y-axis: Depth (feet) Soil gas points in red, monitoring wells in blue Soil Gas Sampling Results 28 30 32 34 35 36 37 TS SGMP-6/MW-15 : 140 34 : 3,200 1 100 10,000-36 : 1,300 35 37 TS SGMP-6/MW- 15 TCE 1 10 100 35 37 TS SGMP-6/MW-15 cis-1,2-dce 1 100 35 37 39 TS SGMP-5/MW- 16S 1 100 10,000 20 21 22 23 24 25 26 28 R SGMP/MW-3 1 1,000 1,000,000 24.5 25 25.5 26 26.5 TS SGMP-10/MW-4 1 1,000 1,000,000 12 14 16 18 20 22 24 26 28 30 F SGMP-10/MW- 16S 1 10 100 24 25 26 28 30 32 TS SGMP-9/MW-8S 1 100
X-axis: Concentration (µg/m 3 ), Y-axis: Depth (feet) Soil gas points in red, monitoring wells in blue Soil Gas Sampling Results 28 30 32 34 35 36 37 TS SGMP-6/MW-15 1 100 10,000 35 37 TS SGMP-6/MW- 15 TCE 1 10 100 35 37 TS SGMP-6/MW-15 cis-1,2-dce 1 100 35 37 39 TS SGMP-5/MW- 16S 1 100 10,000 20 21 22 23 24 25 26 28 R SGMP/MW-3 1 1,000 1,000,000 24.5 25 25.5 26 26.5 TS SGMP-10/MW-4 1 1,000 1,000,000 12 14 16 18 20 22 24 26 28 30 F SGMP-10/MW- 16S 1 10 100 24 25 26 28 30 32 TS SGMP-9/MW-8S 1 100
X-axis: Concentration (µg/m 3 ), Y-axis: Depth (feet) Soil gas points in red, monitoring wells in blue Soil Gas Sampling Results 28 30 32 34 35 36 37 TS SGMP-6/MW-15 1 100 10,000 35 37 TS SGMP-6/MW- 15 TCE 1 10 100 35 37 TS SGMP-6/MW-15 cis-1,2-dce 1 100 35 37 39 TS SGMP-5/MW- 16S 1 100 10,000 20 21 22 23 24 25 26 28 R SGMP/MW-3 1 1,000 1,000,000 24.5 25 25.5 26 26.5 TS SGMP-10/MW-4 1 1,000 1,000,000 12 14 16 18 20 22 24 26 28 30 F SGMP-10/MW- 16S 1 10 100 24 25 26 28 30 32 TS SGMP-9/MW-8S 1 100
X-axis: Concentration (µg/m 3 ), Y-axis: Depth (feet) Soil gas points in red, monitoring wells in blue Soil Gas Sampling Results 28 30 32 34 35 36 37 TS SGMP-6/MW-15 1 100 10,000 35 37 TS SGMP-6/MW- 15 TCE 1 10 100 35 37 TS SGMP-6/MW-15 cis-1,2-dce 1 100 35 37 39 TS SGMP-5/MW- 16S 1 100 10,000 20 21 22 23 24 25 26 28 R SGMP/MW-3 1 1,000 1,000,000 24.5 25 25.5 26 26.5 TS SGMP-10/MW-4 1 1,000 1,000,000 12 14 16 18 20 22 24 26 28 30 F SGMP-10/MW- 16S 1 10 100 24 25 26 28 30 32 TS SGMP-9/MW-8S 1 100
Purge Volume Testing Results Well TS MW-8S Volumes Purged Prior (µg/m 3 ) ppb-rae Result (µg/m 3 ) 1 518 3 534 420 90 5 530 10 12 14 16 18 20 22 24 26 28 30 F MW-16S F SGMP-10/MW-16S 1 10 100 1 306 46 3 2 <6.9 5 245 24 25 26 28 30 32 SGMP-9/MW-8S - RESAMPLING 34 10 100 1,000 Soil gas points in red, initial monitoring well sampling in blue, second monitoring well sampling in green.
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
Soil Gas Sampling Results 10000000 1000000 Monitoring Well (ug/m 3 ) 100000 10000 1000 100 R 2 = 0.9367 TCE cis-1,2-dce 10 1 1 10 100 1000 10000 100000 1000000 10000000 Soil Gas Monitoring Point (µg/m 3 )
Soil Gas Sampling Results 1,000,000 100,000 Concentration (µg/m 3 ) 10,000 1,000 100 NC Non-Residential SL NC Residential SL 10 1 Each vertical line represents a different sampling location
SUMMER VERSUS WINTER TRENDS IN INDOOR AIR CONCENTRATIONS
Weather in the South Don t open the door, you ll let the air out! What season is it?
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)
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 0.1 30 40 50 60 70 80 90 Mean Outside Temperature (⁰F) On-Site #1 On-Site #2 Residence TCE
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 0.1 30 40 50 60 70 80 90 Mean Outside Temperature (⁰F) TCE
Summer vs Winter Indoor Air Concentration Trends Durham, NC Site Concentration (µg/m 3 ) 100 10 1 0.1 0.01 30 40 50 60 70 80 90 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
Concentration (µg/m 3 ) 100 10 1 0.1 Summer vs Winter Indoor Air Concentration Trends Durham, NC Site 0.01 30 40 50 60 70 80 90 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
Summer vs Winter Indoor Air Concentration Trends Denver, NC Site 10.0 Concentration (µg/m 3 ) 1.0 Highest concentration detected at 80⁰F Residence 0.1 30 40 50 60 70 80 90 Mean Outside Temperature (⁰F)
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 0.1 30 40 50 60 70 80 90 Mean Outside Temperature (⁰F) Residence
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)
Summer vs Winter Indoor Air Concentration Trends Comprehensive Data Set 100 Concentration (µg/m 3 ) 10 1 0.1 Ummm 0.01 20 30 40 50 60 70 80 90 Temperature (⁰F)
Summer vs Winter Indoor Air Concentration Trends Comprehensive Data Set 100 Concentration (µg/m 3 ) 10 1 0.1 42 trendlines 76% upward (red) 24% downward (blue) 0.01 30 40 50 60 70 80 90 Mean Outside Temperature (⁰F)
Summer vs Winter Indoor Air Concentration Trends Comprehensive Data Set 100 NC Non-Residential SL 10 NC Residential SL Concentration (µg/m 3 ) 1 0.1 0.01 Each vertical line represents a different sampling location
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.