calculation of soil remedial action objective … · f1~~cti01~ organic carpon in soil (unitless)...

From: File: Date:

.Subject:

Memo:

MEMO TO FILE

Birgit Land~ject Manager, NMED-Superfund Oversight Section Fruit Avenue Plume, CERCLIS ID# NMD98666891 l March 15~ 2001

Calculation of Soil Remedial Action Objective Concentrations

This Memo to File documents the data and calculations used to develop concentrations of tetrachloroethene (PCE) and trichloroethene (TCE) in soil that would pose a risk to ground water if left untreated. These site-specific calculated soil concentrations were used as the soil Remedial Action Objective (RAO) for the Fruit Avenue Plume site (Site), as referenced in th~ Feasibility Study, and used in the Proposed Plan of Action for the Site.

Laboratory data show that Site soils contain PCE concentrations up to 3 miligrams per kilogram (mg/Kg), and TCE concentrations up to 0.5 mg/Kg. There are no regulatory maximum contaminant levels for soil, and no chemical-specific applicable or relevant and appropriate requirements (ARA.Rs) were identified for the Site soil contaminants. Consequemtly, remediation goals for the Site soils were selected based on guidance outlining scientific methods to determine protective goals, according to NCP procedure.

The Site soil concentrations were below EPA pre-screening levels for direct risk from soil to humans through ingestion, inhalation, or dermal contact. However, the soil concentrations were high enough to contaminate ground water above MCLs, thus posing a risk to human health through the ground water pathway. To protect ground water from being impacted above MCLs from contaminated soils, NMED calculated a site-specific remediation goal (the soil RAO) for the soil to be 0.027 mg/Kg of PCE, or less, and 0.024 mg/Kg ofTCE, or less. The soil remediation goal was calculated using the EPA' s Soil Screening Guidance: Users Guide, EPA Publication 9355.4-23, July 1996, as described below.

Equation 10: Soil Screening Level Partioning Equation for Migration to Ground Water, was used to calculate the screening level of PCE and TCE in soil. This equation is as follows:

Screening Level in Soil (mg/Kg) = Cw .[Kd + filw + 8afilJ

Pb

where

145302

Cw= Target soil leachate concentration (mg/L) ~ = soil-water partition coefficient (L/kg), also K00 X f00

K00

= soil organic carbon/water partition coefficient (L/kg)

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foe= :fraction organic carbon in soil (gig) ew =water-filled soil porosity (L water/L soil} ea= air-filled soil porosity (L air/L soil), also n-ew n = soil porosity (L pore/L soil), also 1- (pb/ Ps) Pb= dry soil bulk density (kg/L) Ps = soil particle density {kg/L) H' = Henry's law constant

NMED used the EPA website http://risk.lsd.ornl.gov/cgi-bin/epa/ssll.cgi to access this equation and run it automatically. Method 1 was selected to run the equation. This website automatically assigns chemical-specific values for~, K0 c, and H' into the equation. The dilution factor assigned to Cw was 20, the default factor used by EPA. The EPA default values for Pb at 1.5, and ps at 2.65, were also used. Site-specific values for foe, and 8w were calculated as follows:

'•

~~~-~~-foe: The foe value used for the Fruit Site was 6.94 x 10-5, which is the average :fraction of

organic carbon measured in soil samples analyzed :from the North Railraod A venue Plume (NRAP) Site. The reason that the NRAP foe values were used for the Fruit A venue Plume Site is because both sites have similar geology, are located in the floodplain of the Rio Grande, and because no laboratory results for foe were available for the Fruit Site.

8w: The ew value used for Fruit Avenue Plume was 0.27. This value was calculated as follows: ew = n (i/Ks)" l/(2b+3)

Where: n =soil porosity (L pore/L soil), also 1- (pb/p5)

i =infiltration rate (rnlyr) Ks= saturated hydraulic conductivity (m/yr) b =soil-specific exponential parameter (unitless)

n = 0.43, which is the arithmetic mean for a fine sand, Table 2-1 Ground Water Hydrology and Hydraulics, by D. McWhorter and D.K. Sunada, 1977

i = 0.22 m/yr, assumed to be the average annual precipitation of 8.71 inches of rain per year (see page 14, Remedial Investigation Report, Fruit Avenue Plume)

Ks= 1.42 x 10-4 mis, which is the Site-specific value calculated :from the pump test conducted in monitor well DM-1, Remedial Investigation Report, Appendix J, Fruit A venue Plume

1/(2b+3) = 0.09 unitless, Table A-2; sand, EPA Soil Screening Guidance, 1996

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od Screening Levels

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Equation Values for Soil to Ground Water

Partitioning Equation J>aramcter

Dilution factor (unitless) F1~~cti01~ organic carpon in soil (unitless)

Water-filled soil porosity (Lwate!LsoiJ)

Dry soil bulk density (kg1"'L) Soil particl~ density (kg/L)

Value

20 6.94e-5

0.27

1.5 2.65

Soil Screening Levels for Soil to Ground Water (mg/kg) ·---. -.. -

Cas Ground \Vater Ground Water Soil Screening Analyte Concentration * Concentration Number

(mg/L) Source Level

Tetrachloroethylene 127184 l.OE-01 MCL 2.7E-02

*Ground Water Concentration=Ground Water Concentration Source x Dilution Factor

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03/12/2001 10:27 AM

001738

Jil Scn:tening Levels h'tp://nsk:.lsd.13ml.gov/cgi-binlepa/ssl2.cgi

Equation Values for Soil to Ground Water ------------.··-·--

Partitioning Equation Parameter

Dilutiop factor (unitless) Fraction organic carbon in soil (unitless)

Water-filled soil porosity (Lwate/LsoiJ)

Dry soil bulk density (kg/t) Soil paiticle. density (kg/L)

Value

20

6.94e-5

0.27 1.5 2.65

Soil Screening Levels for Soil to Ground Water (mg/kg)

·-:--··---·

Analyte Cas Number

Trichloroethylene 79016

Ground Water Concentration*

(mg/L).

l.OE-01

Ground Water Concentration

Source

MCL

Soil Screening Level

2.4E-02

*Grow1d Water Concentration=Ground Water Concentration Source X Dilution Factor

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Site maintained by: Office of Emergency and Remedial Response [email protected]

03/12/2001 10:1 l AM

001739

f2

..... EA~Un~edStates c;·· -sunP'~·· u1rd ·~ Errvironrncnt:J! Protection · . • 'f':.""" ' · ~ .. .. Agenc-1 Risk '.As ess:ment

SELECTION:

Your Analytes are: Tetrachloroethylene

Your Pathwavs are - Soil to Groundwater Default Parameters

.cg1

Each pathway you hav~ selected is given below al9ng with the applicable Equations and its associated Default Parameters. For each equation, the default values will be used unless you enter a different value. ·

~

Soil to Ground Water ; Soil Screening Level - METHOD 2 • Mass-Limit Equation for Migration to Ground i Water '

Soil Screening Level - METHOD 1 Partitioning Equation for Migration to '

Ground Water with:

i,i.., _2_0 _ __,I dilution factor (used to calcualte !cw)

; J 6. 94e-~ foe (fraction organic carbon in soil) gig

: ; ..-tt o.2fl e w (water-filled soil porosity)

l Lwate!Lsoil

, f 1. !' I Pb (dry soil bulk density) kg/L

! ! 2. 65 I Ps (soil particle density) kg/L

The dilution factor defaults to 20 for a 0.5-acre source. If you have all of the parameters needed to calculate a dilution factor, you may use method 2.

I l I

cilltion ·factor = 1 +Kid IL

where:

[ ! o .18 ] I (Infiltration Rate) rn/yr j rr:s:Jpb (dry soil bulk density) kg/L I . j I 7 o I ED (Exposure Duration) yr j f O I d5 (depth of source) m - site-specific ii..-----. j J I K (aquifer hydraulic conductivity) m/yr l r--]i (hydraulic gradient) m/m

j l = IL (source length parallel to ground l water flow) m ~ r .. 1 da (aquifer thickness) m - site-specific , i i j I

Do not us·e this method unless you have values for all of the parameters.

Soil to Grourid Water Notes

12/20/00 2:29 PM

._ 001740

http://risk.lsd.ornl.gov/cgi-bin/epa/ssl l .cgi

Soil to Ground ·water Notes

Method for Calculating Soil to Goundwater Method 1 ® Method 2 0

iNOTES:

I. Cw(target soil leachate concentration) mg/L =nonzero MCLG. MCL or HBL x dilution factor (which may be calculated or set to a site-specific default)

2. 6 a( air-filled soil porosity) Lai/Lsoi! = n- 0 w

3. H' (dimensionless Henry1s law constant) - chemical specific 4. n (total soil porosity).LporJLsoil = 1-(Pb/ P5) .

5. Kd (soil-water partition coefficient) L/k.g =Koc x t~c (organics) - chemical-specific 6. K 0 c (soil organic carbon/water partition coefficient) L/kg - chemical specific

7. d (mixing zone depth) m - Calcula~ecJ. aud usec! in,.th~ ~iltit,fQU J~s;~oi;: ~quation. ~,,, ,,,,, .. •·····"~"" :!===::::::i::" ===· ::'::;''' ==·=• ===·=' =· ==· =' =·=·:::::::::• '"''::::""'ffi""=:':U.:::::::=J""'h::::'':'"'··=·::::::-::::-~>::::"1:.J=•l,,,="'L" ~· ~::!''M;;;:.=""'="" ·::.::·~::::::·:::::"~::::· =···=·=:•1=,,=::'' '•==" =·:::•••:::::••• =-==""==-:,,,.:;::'~"''""=:::::::::;::=

You must select one of the following output options ® View on Screen 0 Tab delimited file 0 Comma delimited file I RETRlEVE •I.--c""'le_a_r-se""'l-ec_t,...io_n_i

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URL: http:l/risk.lsd.ornl.gov/epa/ssl1.htrn This page was last updated on: May 12, 1999

Site maintained by: Office of Emergency a.nd Remedial Response beaslev.lvnn(@eoa.gov

! 2/20/00 2:29 PM

001741

:::icreemng

SELECTION:

Your Analytes are: Trichloroethylene

Your Pathways are Soil to Groundwater

Default Parameters Each pathway you have selected is given below along with the applicable Equat associated Default Parameters. For each equation, the default values will be use enter a different value. ·

Soil to Ground Water

l I !

I

Soil Screening Level - METHOD 1 Partitioning Equation for Migration to

Ground Water

1

1

, I 20 I dilution factor (used to calcualte Cw)

·I 6. 94e-~ foe (fraction organic carbon in soil) gig I e-:-Ho.2B e w (water-fined sou porosity)

Lwate/Lsoil j 1. 5 I Pb (dry soil bulk density) kg/L 1, ___ ..,.

11 2 • 6 5 I P s (soil particle density) kg/L

The dilution factor defaults to 20 for a 0.5-acre source. If you have all of the parameters needed to calculate a dilution factor, you may use method 2.

Soil Screening Level - TH Mass-Limit Equation for Migratio

Water

where:

I o .18 I I (Infiltration Rate) m/yr j 1. 5 IPb (dry soil bulk density) kg

I 7 o J ED (Exposure Duration) yr I o I d5 (depth of source) m - site

I I K (aquifer hydraulic condu I )i (hydraulic gradient) m/m

I ~ IL (source length parallel to water ow) m l J da (aquifer thickness) m - si

Do not use this method unless have values for all of the parameters.

Soil to Ground Water Notes

1/10/01 5:02 PM

001742

;::,creenmg Leve1s

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http://nsk.lsd.orni.gov/cg1-bm/epa/ssl:l.cg1

AEA~UnftedStates. ..,_w~ ; . . . · Environmcntnt Protection ....... .. . . A .... . ........ , .. -·······

Equation Values for Soil to Ground Water

Partitioning Equation Parameter

Dilution factor (unitless) Fraction organic carbon in soil (unitless) Water-filled soil porosity \Lwater'Lsoil)

Dry soil bulk density (kg/L) Soil particle density (kg/L)

'•

Val

20 6.94

0.!2

.1.5 2.65

Soil Screening Levels for Soil to Ground Water (mg/kg)

Analyte Cas Number

Trichloroethylene 79016

Ground Water Concentration*

(mg/L)

l.OE-01

Ground Water Concentration

Source

MCL

So

*Ground Water Concentration=Ground Water Concentration Source x Dilution Facto

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1/10/01 5:02 PM

001743

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Soil to Ground Water Notes

I NOTES:

I i.

I

Cw( target soil leachate concentration) mg/L = nonzero MCLG, MCL, or HBL factor (which may be calculated or set to a site-specific default)

2. ea( air-filled soil porosity) Lai!Lsoil = n- 0 w

3. H' (dimensionless Henry's law constant) - chemical specific

I

4. n (total soil porosity) LporelLsoil = 1-(Pb/ Ps) 5. Kd (soil-water partition coefficient) L/kg =Koc x f0c (organics) - chemical-:spe 6. K0c (soil organic carbon/water partition coefficient) L/kg - chemical specific

! '·

7. d (mixing zone depth) m - Calculated and used in the dilution factor equation.

You must select one of the following output options ® View on Screen 0 Tab delimited file 0 Comma delimited file I RETRIEVE J-1-c-le-ar_s_e.,...le-ct..,..io_n_

[Risk Assessment Home] [EPA Home I OSWER Home I Superfund Home J

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1/10/01 5:02 P!vf

001744

calculation of soil remedial action objective … · f1~~cti01~ organic carpon in soil (unitless)...

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