,00 Sr UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

REGION VIII

999

18th STREET - SUITE 500

DENVER, COLORADO 80202-2466

April 27, 2004

Ref: 8EPR-PS

MEMO.RANDUM

Subject: Rocky Mountain Arsenal, Off-Post Area Vapor Intrusion Assessment.

From: Helen Dawson, Ph.D., Hydrogeologist, Superfund Program Support

Dawson.Helen(a-)el2a.gov; (303) 312-7841

Bob Benson, Ph.D., Toxicologist ...... (303) 312

Denson.Bob@e a. ov -7070

To: Laura Williams, Team Leader

Rocky Mountain Arsenal Federal Facility Site

SUMMARY OF FINDINGS

Concentrations of volatile organic compounds (VOCs) present in groundwater north of Rocky

Mountain Arsenal (RMA) were evaluated using the Johnson and Ettinger Model (GW-SCREEN)

as implemented by EPA (US EPA, March 14, 2003). Estimated indoor air concentrations and

potential cancer and non-cancer risks were calculated for theoretical inhalation exposure to

groundwater vapors in a residential setting. An initial evaluation yielded estimated cancer risk

values slightly above the 1. 0 x 10'5 screening level for four chemicals (carbon tetrachloride,

chloroform, tetrachloroethene, and trichloroethene). Non-cancer risks were below the acceptable

screening level of 1.0 for all chemicals. When site-specific information about the subsurface is

incorporated into the model, estimated potential cancer risks are reduced to 3.5 x 10 6 or less for

all chemicals in the off-post area. As the refined site-specific estimated cancer and non-cancer

risks are below their respective screening levels, no further evaluation of the vapor intrusion

pathway is warranted at this time. Consequently, there is no need to require vapor intrusion

controls in buildings overlying the contaminant plumes in the off-site area.

Potential vapor intrusion-related risks were calculated for each chemical detected above its

reporting limit in each off-post well. The site-specific information input to the model included

groundwater concentrations, soil type, and depth to groundwater. The most recent groundwater

concentrations for analytes detected in each of the off-post wells were used to predict potential

future indoor air concentrations and the associated human health risks due to vapor intrusion.

These predictions assume constant groundwater concentrations over 30 years. This approach is

conservative as concentrations are expected to continue to decrease due to the ongoing

_00033830 11452-2
groundwater treatment required for the RMA site. Three different soil types were used in this

evaluation-loaMY sand, sandy loam and silt loarn-to evaluate the range of soil types observed

in the vadose zone in the off-post area. The coarsest grained soil provides the most conservative

predicted indoor air concentrations and associated inhalation risks. The average depth to

groundwater in each well was used as input to the model. The future residential scenarios

assumed either basement or slab-on-grade foundation structures, depending on the depth to

groundwater. The toxicological factors used in the analysis are those listed in Appendix D of

EPA's Draft Vapor Intrusion Guidance WS EPA, November 2002), except as noted in the text

below. Because Inhalation Unit Risk Factors are not yet published in IRIS for tetrachloroethene

and trichloroethenc, a range of values was evaluated. The remainder of the'madel input

parameters used were the default values described in Appendix G of EPA's Draft Vapor

Intrusion Guidance (US EPA, November 2003). The assumptions used in this assessment are

conservative and therefore provide conservative estimates of the potential indoor air

concentrations and the associated cancer and non-cancer risks due to vapor intrusion.

DATA EVALUATIED

The following data were reviewed for this assessment:

1. A map showing the location of off-post monitoring wells and the interpreted extent of

contaminant plumes (US Army, December 1, 2003. Estimated Areas Exceeding

Containment System Remediation Goals for Water Year 2002).

2. Groundwater concentrations from the 2002 and 2003 rounds of sampling in the off-post

area. Table I presents the most recent analytical data for the wells in which VOCs and

other compounds of concern for vapor intrusion were detected above reporting limits.

3. Historical concentrations of VOCs in the off-post wells in Sections 11, 12, 13, and 14.

4. Bore logs of off-post wells in which VOCs and other compounds of concern for vapor

intrusion were detected above reporting limits.

5. Current and historical water level data for off-post wells in Sections 11, 12, 13, and 14.

ASSUMPTIONS AND METHODOLOGY

The model applied in this assessment of the vapor intrusion pathway is the Johnson and Ettinger

Model (GWSCREEN) as implemented by EPA (US EPA, March 14, 2003), which incorporates

default parameters as described in Appendix G of EPA's Draft Guidance for Evaluating the

Vapor Intrusion to Indoor Air Pathway from Groundwater and Soil (November, 2002).

The site-specific information used as input to the model included groundwater concentrations,

soil type, and depth to groundwater (Tables I and 2).

2

Printed on Recycled Paper
The most recent groundwater concentrations for analytes detected in each of the off-post wells

(Table 1) were used to predict indoor air concentrations and the associated human health risks

due to vapor intrUsion. Historical trends indicate that VOC concentrations in the off-post wells

are decreasing. Therefore, the most recent groundwater concentrations can be used as a

conservative estimate of potential future concentrations. The predicted indoor air concentrations

and associated risks assume constant groundwater concentrations over 30 years. In fact,

concentrations are expected to continue to decrease due to the ongoing groundwater treatment

required for the RMA site. For compounds that were below detection in the off-post wells, onehalf the detection limit was used as the groundwater concentration (Table 2).

The vadose zone lithology observed in the off-post wells includes sands, silty sands, sandy silt,

sandy clay, and silty clay. To evaluate this range of lithologies and because the model is very

sensitive to soil type, three different soil types were evaluated with the model: loamy sand, sandy

loam and silt loani. The model's default values for the soil specific properties - bulk density,

moisture content, and porosity - were used for each soil type. The values used for Qr,ýjj in this

evaluation were those calculated by the model for each soil type. The resulting values are lower

than the default value of 5 L/min recommended by EPA's vapor intrusion guidance. This was

done in order to compensate for the conservative assumption that groundwater concentrations

remain at the sarne level for 30 years. The impact of soil type can be seen in the range of

predicted indoor air concentrations and associated inhalation risks shown in Table 1. The

coarsest grained soil-loarny sand-provides the most conservative predicted indoor air

concentrations and associated inhalation risks.

Historical water levels suggest the depths to groundwater for most wells fluctuate about a mean

level with no significant increasing or decreasing trend over the 10+ years on record.

Consequently, average depth to groundwater in each well was used as input to the model. Vapor

intrusion-related risks were calculated using the available data for each well, because depth to

groundwater as well as groundwater concentrations varied from well to well. Depending on the

depth to groundwater, either a basement or slab-on-grade foundation was assumed, as EPA's

vapor intrusion guidance recommends a minimum vadose zone thickness of 5 feet between the

groundwater and the base of the foundation for model applications. Thus, for off-post wells with

depths to groundwater greater than 11 feet, the future residential scenario assumed the residences

would be constructed with basements. For wells with depths to groundwater less than 11 feet,

slab on grade foundations were assumed.

The remainder of the model input parameters used in this evaluation were the default values

described in Appendix G of EPA's Draft Vapor Intrusion Guidance (US EPA, November 2002).

These default parameters incorporate conservative assumptions for building- and soil-related

parameters.

The toxicological factors used in this analysis are listed in Table 3. Except as noted below the

toxicological factors used in the analysis were those in Table D- I of EPA's Draft Vapor Intrusion

Guidance (US EPA, November 2002). An RfC for benzene of 3E-02 Mg/M3 was added to the

IRIS file in April 2002 and is used in this analysis. A new IRIS file dated February 2003

3 FWnted on Recycled Paper
established the RX for all xylene isomers at I E-0 I mg/141'. The Inhalation Unit Risk on IRIS for

chloroform is currently under review and likely will be replaced by an RfC that will protect for

both cancer and non-cancer endpoints. The final value that likely will be established for the RfC

for chloroform and that will be used to calculate the Hazard Index will result in much higher

screening level concentrations than those calculated using the value shown in Table 3. However,

since the review has not been completed, this evaluation calculated the risks using the existing

Inhalation Unit Risk on IRIS. For tetrachloroethene there is no Inhalation Unit Risk on IRIS. The

"old ORD" Inhalation Unit Risk for tetrachloroethene was 5.8 E-07 (gg/M3),l . The Superfund

Technical Support Center as of June 2003 is recommending for tetrachloroethene an Inhalation

Unit Risk of 5.9 E-06 (gg/M3),l . Both values are used to compute tetrachloroethene risks in this

analysis. Likewise, there is no Inhalation Unit Risk on IRIS for trichloroethene and,

consequently, this analysis uses both the "old ORD" Inhalation Unit Risk of 1.7E-06 (gg/rn 3)-l

and the new provisional value of 1. 1 E-04 (gg/M3)-' recommended in EPA's draft 2001

reassessment. The calculated tetrachloroethene and trichloroethene risks shown in Tables I and 2

are based on the most conservative cancer risk factors; the impact of using the lower cancer risk

factors is described in the table notes and below in the Results section.

The cancer risk and hazard index were calculated using the residential'scenario described in

Appendix D of EPA's draft vapor intrusion guidance (US EPA 2002). The residential scenario

assumes that an individual will be in a residence 24 hours/day, 350 days/year, for 30 years. The

averaging time for carcinogens is 24 hours/day, 365 days/year, for 70 years; the averaging time

for non-carcinogens is 24 hours/day, 365 days/year, for 30 years.

RiEsuLTs

The calculated indoor air concentrations and potential cancer and non-cancer risks are

summarized in Table I for the off-post wells in which compounds of concern for vapor intrusion

were detected above reporting limits. This table shows that, when site-specific information is

incorporated into the model, the maximum estimated potential cancer risk for any individual

detected chemical in any individual off-post well is 3.5 x 10-6 for trichloroethene in well 37391

assuming loamy sand for the vadose zone, 1.3 x 10-6 assuming sandy loam, and 6.7 x 10-7

assuming silt loam. If cumulative risks are calculated for each well, the total estimated maximum

potential inhalation risk for any individual well is 6.7 x 10-6 assuming loamy sand, 2.5 x 10-6

assuming sandy loam, and 1.3 x 10-6 assuming silt loam. Thus, for any individual well the

estimated site-specific cancer risks fall below the 1.0 X jo-5 screening level. Non-cancer risks are

below a hazard index of 1.0 for all chemicals and all wells.

As stated above, the estimated risks for tetracholorethene and trichloroethene risks were

calculated using the most conservative Inhalation Unit Risk values. If instead the less

conservative Inhalation Unit Risk values are used, the estimated risks for these compounds

decrease by approximately an order of magnitude. In that case, the maximum risk corresponding

to any individual chemical in a well is 3.1 x 10-6 (for chloroform in well 37095 assuming loamy

sand for the vadose zone). Excluding chloroform, the maximum risk corresponding to any

4 40W_

PtInted on Recycled Paper
individual cheynical in a well is 2.3 x 10'6 (for carbon tetrachloride in well 3 7094 assuming

loamy sand for the vadose zone).

Table 2 shows the indoor air concentrations and potential inhalation risks associated with nondetected compounds, assuming their actual concentrations are represented by a level one-half

their respective reporting limits. The maximum contribution to cancer risk in each well from

analytes with concentrations below their reporting limits is 5.5 x 10,7 or less assuming loamy

sand, 1.9 X 10-7 or less assuming sandy loam, and 9.8 x 10-8 or less assuming silt loam.

CONCLUSIONS

These results of this assessment indicate that no further evaluation of the vapor intrusion pathway

is warranted at this time and there is no need to implement vapor intrusion controls in buildings

overlying the contaminant plumes in the off-site area.

REFERENCES

US EPA, "Draft Guidance for Evaluating the Vapor Intrusion to Indoor Air Pathway from

Groundwater and Soils," November, 2002.

US EPA, "User's Guide for Evaluating Subsurface Vapor Intrusion Into Buildings," March 14,

2003.

5 Pdnted on Rwycled Paper
Table 1

Vapor Pathway Analysis

Off-Post Wells with Analytes Detected Above Reporting Limits

Well and Chemical Name Model I put Mod Output Mode Output Mode Output

Most

Recent Avg. Cale. Cale. Cale.

Ground Depth Indoor Indoor Indoor

Water to Air Air Air

Sample Conc. Water Foundation Soil Cone. Cale. Cale. Soil Cone. Cale. Cale. Soil Cone. Cale. Cale.

Well ID Symbol Chemical Name Date (uv/L) (ft b2s) Type I Type fttm.3) Risk In Type (u&Lm3 Risk III Type .(upJm3) Risk HI 1

37039 JCCLA carbon tetrachloride 8/12/2003 0.42 20.8 Basement I LS 5.88E-02 3.62E-071 NA SL 2.11 "2 1,3011-07 NA SIL 1. 11 E-02 6.82E-08 NA

37039 CHCU chloroform 8/12/2003 0.624 20.8 Basement I-S 1.26E-02 1.19E-071 N SL 4.64E-03 4.39FA8 NA SIL 2,27E-03 2.14E-08 - NA

37040 DLDRN dieldrin 7/11/2002 0.122 23.8 Basement IS 1.39E-06 2.63E-0917.64E-06 S L 7.57E-07 1.4311-09 4. 1 SE-06 SIL 4.4213-07 8.3611-10 2,4211-06

37065 12DCLE 1,2-dichloroethane 8/13/2003 3.86 6.8 Slab IS 3.0513-02 3.26E-07 NA SL 1.2513-02 1.34E,07 NA SIL 6.1411-03 6.5611-08 NA

37065 ITCLEE tetrachloroethylene 8/13/2003 5.541 6.8 Slab LS 15.21E-01 1.2613-06 NA SL 1.8311-01 4AM-07 NA SIL 1.0913-01 2.65E-07 NA

37065 TRCLE trichloroethylene 8/13/2003" 0.958 6.8 Slab LS 5.92E-02 2,68E-06 1.4213,031 SL 2.11 E-02 9.53"7 5.0513-04 SIL 1.23E-02 5.56E-07 2.9511-04

37081 DI-DRN dieldrin 7111/2002 0.267 -4.2 (5)_ Slab LS 8.66E-06.1.64E-08 4.75E-05 SL 4-32E-06 8.16E-09 2.36E-05 SIT, 2.3413-06 4.43E-09 1.28E-05

37083 12DCLE I 2-dichloroethane 7/15/2002 1.73 4.7(5) Slab IS 1.4013-02 1.50E-07 NA SL- 5.71 E-03 6. 1013,08 NA SIL 2.79E-03 2.98E-08 NA

37083 TCLEE tetrachloroeLhylene 7/15/2002 4.54 .7 5 Slab IS 4.38E-01 1.0613,06 NA SL 1.52E-01 3.68E-07 NA . SIL 9.09E-02 2.20E-07 NA

37083 TRCLE trichlorocthylene 7/15/2002 0.764 _L_U_ - - - 7.69E-07 4.08E SIL 9.9412,03 4.49E-07 2-38E-04

7J5 IS 4,84E-02 2.1913-06 1.1611-03 SL

37094 CCLA carbon tetrachloride 7/22/2003 2.64 19.3 Basement LS 3.74E-01 2-31E-06 NA SL 1.33"l 8.22E-07 -NA SIL 6."E-02 4.3113-07 NA

37094 CHCU chloroform 7/2212003 1.83 19.3 Basement LS 3.7313-02 3.53E-07 NA SL 1.37E-02 1.2913-07 NA - SIL 6.68E-03 6.31E-08 NA

37095 12DCLE 1.2-dichloroethane 7/22/2003 0.22 19.3 Basement LS 1. 1613-03 1.24&08 NA SL 4.5211-04 4.83E-09 NA SIL 2.07E-04 2.21 E-09 NA

-37095 CHCL3 chloro 712212003 16.0 19.3 Basement LS 3.2611-01 3.08E-06 NA SL 1.20E-01 1.13E-06 NA SIL 5.84E-02 5.5213-07 NA

37095 DBCP d Lhý ý 7/22/2003 0.257 19.3 Basement IS 3-14E-04 8.8511-11 1.50E-03 SL 1.5213-04 4.29E.11 .7.30" SIL 6.86E-05 1.93&11 3.2911-04

IS 8.12E-01 1.97E-06 NA SL 2.92"1 7. E-07 NA SIL 1,53E-01 3.

37095 TCLEE tetrachloroeLbyLene 7/2212003 11.4 19.3 Basement -- - 72F-07 ___ý!A

37095 TRCLE trichloroethviene 7/22/2003 0.449 19.3 Basement LS -.2,06 9,30E-07 4.93]3-041ýSl, 7.45E",03 3-3711-07 1.79"4 SIL 3.8413-03 1,7311-07 9.20E-05

LS 

T 

1.

37110 CffC--13 chloroform Slab 9.46E-03 8.94E-08 NA S. 1 3 5522IR-03 3-3313-087 NA

Notes:

The most recent value for each analyte for each well is listed unless a higher reporting limit was used in 2003.

If average depth to groundwater is less than 5 feet, 5 feet was used as input to the model.

Basements am assumed to extend 200 cm below ground surface; slab foundations are assumed to extend 15 cm below ground surface.

The TRCLE risk values shown above am calculated using a URF of 1. 1 E-04 (mg/m3)-l. For a URF of 1.713-6 (mgtm3)-I, the calculated risks are a factor of 1.55E-02 lower.

'Me TCLEE risk values shown above ate calculated using a URF of 5.913-6 (mg1m3)-l. For a URF of 5.8E-7 (m&/m3)-l, the calculated risks are a factor of 9.83E-02 lower.
Table I (Cont'd)

Vapor Pathway Analysis

Off-Post Wells with Analytes Detected Above Reporting Limits

Well and Chemical Name Model I put I Mode 0 u tput Mod Output Mod Output

Most

Recent Avg. Cale. Cale. Cale.

Ground Depth Indoor Indoor Indoor

Water to Air Air Air

Sample Cone. Water Foundation Soil Cone. Cale. Cale. Soil Cone. Cale. Cale. Soil Cone. Cale. Cale.

Well ID symbol Chemical Name Date (uPJL) I (ft has) Type Type (uglm3) Risk HI Type (uZtm3) Risk III Type I (ug/m3) Risk HI

37339 CHCU chloroform 8/26/2003 1.28 15,9 Basement LS 2.68E-02 2.53E.07 NA SL 9.70E-03 9.17E-08 NA SIL 4,73E-03 4.47E-08 NA

I . I ý

37368 12DCLE 1,2-dichloroetharie 7/15/2002 0.301 25.4 Basement LS 11.5113-03 1.6211-08 NA SL 6.03E-04 6.44E-09 NA SIL 2.77E-04 2.96E-09 NA

37369 CHCL3 chloroform 7/15/2002 15.4 25.4 Basement LS 3.OOE-0 I 2.84E-06 NA SL 1.13E-01 1.06E-06 NA SIL 5.5 1 E-02 5.2 1 E-07 NA

37368 DBCP dibromochloropropane 7/15/N02 0.364 25.4 Basement LS 3.9 1 E-04 I.IOE-10 1.88E-03 S L 1.9813-04 5.58E-11 9.48E-04 STI, 9.07E-05 2.56E-11 4.35E-04

37368 TCLEE tetrachloroeklene 7/15/2002 15.5 25.4 Basement LS 1.05E+00 2.54E-06 NA SL 3,86E-01 9.36E-07 NA I SIL 10413-01, 4.94E-07 NA

,1]7 37368 ITRCLE trichloroelftlene 7/15/2002 0.661 25.4 Basement LS 2.87E-0211.30E-06 6.88E-04 S L 1.07E-02 4.82E-07 2.56E-04 SIL 5,5113-03 2.4913-07 1.3213-04

37374 CHCU chloroform 6/24/1999 1.47 11.3 Basement LS 3.1913-02 3.02E-07 NA SL 11.1313-02 1.07E-07 NA_ SIL 15.51E-03 5.21E-08 NA

I ---

37389 CHCU chloroform 7/15/2002 0.283 6.6 Slab LS 8.32E-03 7.86E-08 NA SL 13.05E-03_ 188E-08 NA SIL 1.66E-03 1.57E-08 _NA

37389 TCLEE tetrachloroethylene 7/1512002 5.64 6.6 Slab- LS 5.3 1 E-0 1 1.2913-06 NA S L 1.8611-01 4.52E-07 NA SIL 1.12E-01 2.70E-07 NA

37391 ICHCL3 _ýh_lorofbrm 7/10/2002 0.6 27.5 Basement LS 1.15E-02 I ý09&07. NA ST.- 4 35E-03 I I E-08 NA SIL 2.1313-03 2.02E-08 _NA

37391 ITCLEE teftachlomethylene 7/10/2002 3.83 27.5 Basement LS 2.54"1 6.15E-07 NA' SL 9.46E-02 2,2913-07 NA SIL 4.9913-02 1.21E-07 NA

37391 TRCLE triqN2ýý 7/10/2002 1.79 27.5 Basement LS 7.65E-02 3.46E-06 1,8313-03 SL 2.87E-02 1.30E-06 6.88E-04 SIL 1.48E-02 6.70E 7 3.55E-04

37396 12DCLE 1,2-dichloroethane .235 6.2 slab LS 7F-03 TO-OF,08 _NA SL 7.68E-04 8,20E-09 NA SIL 3,75E-04 4.0113-09 NA

37396 TCLEE tetrachloroethvlene 8/12/2003 0.394 6.2 Slab LS 3.73E-02 9.0513,08 NA SL 1-3013-02 3.1613-08 NA SIL 7.82E-03 1.90"ll NA

37408 CHCU chloroform 7/22/2003 1.04 _Y22_,6 Ba ment LS 2.07E-02 1.95E-07 NA SL 7.68E-03 7.26E-08 NA SIL 3.7613-03 3.55E-08 NA

7/2 1,44E-07 NA SL 2.16E-02 5.2413-08 NA SIL 1.1413-02 2.7613-08 NA

37408 TCLEE tetrachloroethylene 2/2003 0.857 22.6 -Basement Is 5.92E-02 -

37409 CHCU .13E-06 ýSL 4.41E 4,1713-07 NA SIL 2 1513-02 ýL0413.07 NA

chloroform 

7/22/2003 

5.93 20.8 

Basomont 

LS 1.20ýEljl 

I 

NA

-tam 3 some SL NA

Y iE - L 

__17

37409 TCLEE chloroeth lone 17/22/2003 12 20.8 Basement LS :8.:43E-01 2.04E-06 NA SL 3.05E-01 7,40E.07 A L89E

8 2E semot LS S -07 9.3313-05 .u a a 37409 TRUE trichloroethylene 7/271200, , E0.1458 20.8 I Basement LS 2.07F-07 9.36F-07 4.9713-04 SL 7.55E-03 3.4 1 E-07 I.SIE-041 1.76E

Notes:

The most recent value for each analyte for each well is listed unless a higher reporting limit was used in 2003.

If average depth to groundwater is less than 5 feet, 5 feet was used as input to the model.

Basements are assumed to extend 200 cm below ground surface; slab %undations are assumed to extend 15 cm below ground surfkce.

The TRCLE risk values shown above are calculated using a URF of 1. IE-04 (mg/m3)-l. For a URF of 1.7E-6 (mgtm3)- 1, the calculated risks are a factor of 1 .5513-02 lower.

The TCLEE risk values shown above are calculated using a URF of 5.9E-6 (mgtrn3)-l. For a URF of 5.8E-7 (mg/m3)-I, the calculated risks are a factor of9.83E-02 lower.

7 Pff"ted on Rwycled Paper
Table 2

Vapor Pathway Analysis

Analyte Reporting Limits

Model Outpu t Model Output Modd Output

Well and Chemical Name (based on 1/2 RP (based on 112 RPU (based o 112 RPL)

Most

Recent Cale. Cale. Cale.

Ground Indoor Indoor Indoor

Water 1/2 Air Air Air Cale. Calc. Sample RPL RPL Soil Cone. Cale. Calc. Soil Cone. Cale. Cale. SoH Conc.

Symbol lChemical Name Date (uZ/L) I (ug/L) Type (ugJm3) I Risk- III Type (uR/m3) I Risk HI Type (ux/T& Risk HI

12DCLE 1,2-dichlomethane 2003-08-12 0.30 0.15 LS 9.47E-04 9.05E-09 NA SL 3.20E-04 3.4 1 E-09 NA SIL 1.45E-04 1.5513-09 NA

CCU carbon tetrachloride 2003-09-13 0.38 0.19 LS 19013-02 1.7913,07 NA SL 9.9511-03 &OF-08 NA SIL 5.20E.03 3.21E-08_ NA

CHCL3 chloroform 2ý0_3-08-13 _03 -I 30.25 LS 5.44E-03 5.14E-08 SL 1-9313-03 1.83E-08 NA si L -04 9.8713-09 NA

0.18 LS 3.78E-03 NA 1.04 _SL -1.38E-03 _NA -3.77 SIL NA 1.97E-05

C12DCE cis-1,2-dichloroeklene 2003ý08-13 6-37- 0.19 E-04 "5 SIL 6.82E-04

00 LS 1.20E-04 3.3913-11 5.75F-04 SL 5.4113-05 1.5313-11 2.5913-04 SIL 2.3613-05

0.1 

L

dibromochloropropnL 2003ý07-22 0.15 0.08

DBCP - SIL 6.66F-12 1.13E-04

DLDRN rin - 02 0.01 LS 2,19E-07 4.14E-10 1.2013-06 9.09E-09 1.72E-10 419RE-07 SIL 4.26E-( -07

TCLEE itetrachloroothylene 2003-08-12 0.20 LS 7.7012-03 1 ý87&081 NA SL 2.6613-03 6.45E-09 NA

T12DCE Itrans-1,2-dichloroeftlene 2003-08-13 0.31 0.16 LS 1.07E-04 2.76E-03 513.05

n 01 

ILIILSIL

TRCLE itrichlaroethylene 20-1 0.13 LS 6.42E-03 12,9013-0-71 1 eAIP-nA I

Note.

All calculations assumed basement foundations that extend 200 cm below ground surface and depth to water equal to I I feet.

The TRCLE risk value shown above is calculated using a URF of 1. 1 E-04 (mg1m3)-l. For a URF of 1.713-6 (mg1m3)-l, the calculated risk is a factor of 1.5513-02 lower.

The TCLEE risk value shown above is calculated using a URF of 5.913-6 (mgtm3)-l. For a URF of 5.8E-7 (mg/m3)-I, the calculated risk is a factor of 9.83E-02 lower.

Ot 8 Pifnted on Recycled Wer
Table 3

Toxicological Factors

Unit Risk

Factor Reference

URF) Conc.

Chen-deal Symbol (Ag/m)-' (mg/M)

1,2-DichloToethane 12DCLE 2.6E-05 0-013+00

1,3-Dicblorobcnzene 13DCLB O.OE+00 LIE-01

Aldrin ALDRN 4.913-03 LIE-04

Benzene C6116 7.813-06 3.OE-02

Carbon tetrachloride CCL4 1.513-05 0.013+00

Chlordane CLDAN LOE-04 7.OE-04

Chlorobenzene CLC6HS 0.013+00 6.oE-02

Chloroform CHCL3 2.313-05 0.013+00

cis- 1,2-Dicliloroethylene 12DCE O.OE+00 3.5E-02

Dicldrin DLDRN 4.6E-03 I.gE-04

Ethylbenzene ETC6H5 LIE-06 I OE+00

Hexachlorocyclopentadiene CL6CP O.OE+00 2.OE-04

Methylenc chloride CH2CL2 4.713-07 3.013+00

o-Xylene XYLEN 0.013+00 1.013-01

p-Xylene XYLEN 0.013+00 1.013-01

Tetrachloroethene TCLEE 5.913-06 O.OE+00

Tetrachloroethene TCLEE 5.8E-07 0.013+00

Toluene MEC6115 O.OE+00 4.OE-01

trans- 1,2-Dichloroethylene 12DCE 0.013+00 7.OE-02

Trichloroethene TRCLE 1.713-06 4.OE-02

Trichloroethene MCLE 1. 113,04 4.0-02