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

425.227.6121asidell@contactpsc.com waldronc@uspioneer.com

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