Upload
vuongtuong
View
219
Download
2
Embed Size (px)
Citation preview
Comparison of Empirical Attenuation Factors to Modeled Attenuation Factors
StudyArea
Site BackgroundSite BackgroundSite LocationSite Location Background on Vapor Migration
Pathway and Sampling ApproachBackground on Vapor Migration
Pathway and Sampling Approach
Ü Co-located indoor air, ambient air, groundwater and soil gas samples (sub-slab and at depth) were collected from 26 commercial and residential building locations in the Study Area between August 2002 and July 2004.
Ü Samples were analyzed for the chemicals of potential concern (COPCs) identified in the Draft Human Health Risk Assessment (Target VOCs).
Ü Chlorinated and petroleum hydrocarbons were detected in groundwater, soil gas, indoor air, and ambient air.
Ü Indoor air sampling results for Target VOCs were adjusted for contributions from background by subtracting the chemical concentration detected in ambient air, likely to have infiltrated the building
Ü Depth to groundwater is 8 to 10 feet below ground surface (bgs)Ü 17 geotechnical samples were collected throughout the area. Soil type is
generally sandy loam/loamy sand with interbeds of silt loam. Ü Building types range from residential construction with basements or crawl
spaces to commercial office or commercial warehouses with slab-on-grade construction.
Statistics for Target VOCsStatistics for Target VOCs
Ü Conducted a thorough building evaluation prior to developing theSampling Plan to identify any potential sources of indoor air contamination.
Ü Collected groundwater samples, soil gas samples, and ambient airsamples with every indoor air sample to assist in determining the source of chemicals found in indoor air.
Ü Subtracted ambient air concentrations from indoor air concentrations to account for background. *The Regulatory Agency would not allow correction due to national indoor air background values.
Ü Used soil gas data qualitatively as in indicator of whether chemicals detected in indoor air are coming from the groundwater or from an indoor air source. *The Regulatory Agency would not allow the soil gas data to be used quantitatively.
Efforts Taken to Minimize or Quantify Background Contributions
Efforts Taken to Minimize or Quantify Background Contributions
Sample Collection
InformationGroundwater Soil Gas Indoor Air Ambient Air
Sample Duration
20-30 min via low-flow 24 hours 24 hours 24 hours
Direct push, in-situ
MW - Low-flow (purge at <300 ml/min, sample at <100 ml/min)
Analytical Method
SW 846-8260 SIM to meet RL goals of Inhalation Pathway Interim Measure Action Levels (IPIMALs)
TO-14A w/SIM to meet RL goals of ALs
TO-14A w/SIM to meet RL goals of IPIMALs
TO-14A w/SIM to meet RL goals of IPIMALs
Number of co-located samples
40 32 51 24
Field Sample Method
GIVF Sampling - direct push soil gas sampling or permanent soil gas port soil gas sampling (purge then sample). Tier 3 Sampling - Sub-slab soil gas, purge then sample. All methods utilized 6L Summa Canisters.
6L Summa Canisters
6L Summa Canisters
Sampling InformationSampling Information
Summary of Multi-Media Sampling ResultsSummary of Multi-Media Sampling Results
Ü There is a large range of AFs across the site and no consistent relationship with elevated groundwater and indoor air.
Ü The strongest correlation exhibited by the data is the relationship between ambient air and indoor air concentrations.
Ü The data show an inverse correlation between groundwater concentrations and measured AFs, indicating that background indoor air/ambient air concentrations are often not related to changes in groundwater (source vapor) concentrations, especially at low (sub-ppb) concentrations.
Ü Ambient air concentrations have a significant impact on measured AF and mask measured AFs.
Ü At sites with variable subsurface, building construction, and urban ambient air concentrations, it may be difficult to verify that JEM is a reliable predictor of indoor air concentrations. ØThis is especially true at sites with low groundwater
concentrations and significant background concentrations in ambient and/or indoor air.
Ü Co-located and co-collected indoor air, ambient air, sub-slab soil gas, and groundwater samples should be collected in order to determine if the indoor air concentrations are associated with VI or background.
Lessons LearnedLessons Learned
Chris Waldron & Kim Prestbo
PIONEER Technologies Corporation
360.570.1700
Amy Sidell
Philip Services Corporation
[email protected] [email protected]
Collecting groundwater samples from temporary wells using direct pushtechnology.
Soil gas sample collection from a permanent soil gas port designed like a miniature monitoring well
with sand pack and screen.
Sample Collection
Sample Collection
Ü Chemicals have been detected in soil at the PSC facility.Ü Dense non-aqueous phase liquid (DNAPL), which is primarily
comprised of chlorinated solvents, is likely to be present in groundwater at the property adjacent to the west of the site.
Ü Chemicals in groundwater appear to have migrated beyond the boundary of the facility towards the southwest.
Chemicals associated with releases of chlorinated solvents and petroleum products have been detected in groundwater at Philip Services Corporation’s (PSC’s) former TSD facility and in the surrounding area, a mixed industrial and residential neighborhood in South Seattle. These chemicals are thought to have been released to groundwater from past operations on the PSC property dating back to the 1950’s, including storage of chemical products in underground storage tanks and processing and storage of chemical products in above ground containers without containment prior to environmental regulation. The results of numerous environmental investigations indicate that:
PSC is currently implementing an interim measure to protect the health of residents and workers potentially exposed to chemicals migrating from shallow groundwater into indoor air.
Freq. Min Max Freq. Min Max Freq. Min Max Freq. Min Max1,1,1-Trichloroethane 6/32 5.44 82.4 24/32 0.41 480.0 27/32 0.20 14.0 18/32 0.18 0.56
1,1-Dichloroethane 20/32 1.8 265.0 8/32 0.63 610.0 1/32 0.22 0.22 4/32 0.15 0.42
1,1-Dichloroethylene 11/32 0.05 4.46 6/32 0.11 0.59 1/32 0.22 0.22 0/32 -- --
1,2,4-Trimethylbenzene 4/32 2.68 48.6 25/32 0.18 28.0 32/32 0.76 190.0 32/32 0.35 6.0
1,2-Dichloroethane 7/32 0.1 1.92 1/32 8.1 8.1 13/32 0.14 2.2 2/32 1.3 1.4
1,3,5-Trimethylbenzene 3/32 1.52 10.3 21/32 0.21 3.6 32/32 0.24 89.0 26/32 0.18 1.8
2-Hexanone 0/32 -- -- 14/32 0.67 19.0 4/32 0.8 8.6 11/32 1.2 3.2
Benzene 11/32 0.76 13.35 25/32 0.42 6.6 32/32 1.2 12.0 32/32 0.95 6.7
Chloroethane 5/32 67.3 552.0 8/32 0.28 17.0 2/32 0.28 0.38 2/32 0.48 0.55
Chloroform 1/32 1.76 1.76 15/32 0.13 20.0 24/32 0.2 4.6 4/32 0.2 0.98
cis-1,2-Dichloroethylene 21/32 1.1 265.0 4/32 0.63 460.0 1/32 0.13 0.13 0/32 -- --
Cumene 0/27 -- -- 0/27 -- -- 1/27 20.0 20.0 1/27 20.0 20.0
Ethylbenzene 4/32 2.18 2930.0 23/32 0.28 130.0 32/32 0.56 26.0 32/32 0.49 9.7
Naphthalene 3/32 9.87 20.8 0/32 -- -- 0/32 -- -- 0/32 -- --
Propylbenzene 3/32 1.46 16.30 0/32 -- -- 1/32 48.0 48.0 0/32 -- --
sec-Butylbenzene 2/32 1.42 2.48 0/32 -- -- 0/32 -- -- 0/32 -- --
Tetrachloroethene 13/32 0.05 2.69 25/32 1.1 280.0 27/32 0.23 3.6 17/32 0.2 12.0
Toluene 4/32 1.06 119.0 30/32 0.54 110.0 32/32 5.1 300.0 32/32 3.3 28.0
trans-1,2-Dichloroethylene 7/32 1.06 7.21 0/32 -- -- 0/32 -- -- 0/32 -- --
Trichloroethene 26/32 0.03 400.0 18/32 0.26 370.0 28/32 0.19 27.0 28/32 0.3 29.0
Vinyl Chloride 25/32 0.02 176.0 11/32 0.1 3.9 4/32 0.04 0.1 18/32 0.081 0.68
Ambient Air (ug/m3)Analyte
Groundwater (ug/L) Soil Gas (ug/m3) Indoor Air (ug/m3)
Note – Frequency is based on number of co-located stations. In cases where more than one media sample were collected, maximum at each station was used for statistics.
Calculating Empirical Attenuation Factors
Calculating Empirical Attenuation Factors
Ü Empirical groundwater to indoor air AFs were calculated for Target VOCs detected in both groundwater and indoor air during co-located sampling events as follows:
)/(@_)/(
3
3
mgWTSGMaxmgIA
AFrGroundwate correctedcorrected µ
µ=
ØWhere:vGroundwater AFcorrected = Measured attenuation factor for groundwater to indoor air (corrected for ambient air)vIAcorrected = Measured indoor air concentration corrected for ambient air.vMax_SG@WT = source vapor concentration predicted by Johnson and Ettinger Model (JEM) based on maximum co-located detected groundwater concentration.
Comparison of Measured TCE AFs to EPA VI Guidance Figure 3b Default Values
Comparison of Measured TCE AFs to EPA VI Guidance Figure 3b Default Values
Notes: 1) Default values based on Figure 3b from Draft Guidance for Evaluating Vapor Intrusion to Indoor Air Pathway (EPA, 2002).2) Empirical AF (TCE_AF_C) calculated for TCE detected in groundwater and indoor air (adjusted for ambient air concentrations). 3) Average TCE Predicted by JEM = average of JEM predicted AF at 10 ug/L for basement and slab-on-grade scenario, assuming sand beneath foundation and loamy sand above water table with depth to groundwater of 305 cm.
1.00E-07
1.00E-06
1.00E-05
1.00E-04
1.00E-03
1.00E-02
1.00E-01
1.00E+00
0.01 0.1 1 10 100 1000 10000
Groundwater Concentration ug/L
Measu
red
AF
Chlor inated Compounds Petr oleum Compounds
Correlation of Measured AFs with Groundwater Concentrations
Correlation of Measured AFs with Groundwater Concentrations
Range of Values Measured in Groundwater (Source Vapor), Soil Gas, Indoor Air and Ambient Air
Range of Values Measured in Groundwater (Source Vapor), Soil Gas, Indoor Air and Ambient Air
0.01
0.1
1
10
100
1000
10000
100000
1000000
Vapo
r Con
cent
ratio
n (u
g/m
3)
Max SG @ WT
Soil Gas
Indoor Air
Ambient Air
Corrected IA
ÜNo consistent AFs measured across site. Ø AFs for all target VOCs detected in
groundwater and adjusted indoor air range from 8E-07 to 8E-02.
ÜSite-specific JEM AFs for target VOCs range from 1E-04 (slab-on-grade) to 7E-04 (basement).Ø AFs for about 32% of target VOCs fall
within the range of JEM-predicted AFs for this area (1E-04 to 7E-04).
Ø AFs for about 50% of target VOCs fall above predicted JEM range.
Ø AFs for about 18% of target VOCs fall below predicted JEM range.
ÜTCE and vinyl chloride most consistently measured in groundwater.Ø TCE most consistently detected in both
groundwater and indoor air, but no consistent correlation with elevated indoor air.
Ø Vinyl chloride not detected in indoor air above ambient concentrations at any location.
Vinyl Chloride
0.1
1
10
100
1000
10000
PCE
Vapo
r Con
cent
ratio
n (ug
/m3)
Max SG @ WT
Soil Gas
Indoor Air
Ambient Air
Corrected IA
0.01
0.1
1
10
100
1000
10000
100000
1000000
TCE
Vapo
r Con
cent
ratio
n (u
g/m
3)
Max SG @ WT
Soil Gas
Indoor Air
Ambient Air
Corrected IA
Trichloroethene (TCE)
Note: Measured AF for All TCs detected in groundwater and Indoor Air (Measured AF for All TCs detected in groundwater and Indoor Air (adjusted)adjusted)
Tetrachloroethene (PCE)
1.00E-06
1.00E-05
1.00E-04
1.00E-03
1.00E-02
1.00E-01
0 5 10 15 20 25 30
Depth to Contamination from Foundation
Vap
or
Att
enu
atio
n F
acto
r
Sand
Loamy Sand
Sandy Loam
Loam
TCE_AF_C
Average TCE Predicted by JEM
General ObservationsGeneral Observations