Symbol

Parameter

Units

Source

Parameter Value(s)

AT_c

Averaging Time for Carcinogens

yr

RBCA

70

AT_n

Averaging Time for Noncarcinogens

yr

RBCA

Residential = 30

Industrial/Commercial = 25

Construction Worker = 0.115

BW

Adult Body Weight

kg

RBCA

70

C_source

The greatest potential concentration of the contaminant of concern in the groundwater at the source of the contamination, based on the concentrations of contaminants in groundwater due to the release and the projected concentration of the contaminant migrating from the soil to the groundwater.

mg/L

Field Measurement

Site-Specific

C_(x)

Concentration of Contaminant in Groundwater at Distance X form the source

mg/L

Equation R26 in Appendix C, Table C

Calculated Value

C_(x)/C_source

Steady-State Attenuation Along the Centerline of a Dissolved Plume

unitless

Equation R15 in Appendix C, Table C

Calculated Value

d

Lower Depth of Surficial Soil Zone

cm

Field Measurement

100 or Site-Specific (not to exceed 100)

D^air

Diffusion Coefficient in Air

cm²/s

Appendix C, Table E

Chemical-Specific

D^water

Diffusion Coefficient in Water

cm²/s

Appendix C, Table E

Chemical-Specific

Symbol

Parameter

Units

Source

Parameter Value(s)

D_s^eff

Effective Diffusion Coefficient in Soil Based on Vapor-Phase Concentration

cm²/s

Equation R6 in Appendix C, Table C

Calculated Value

ED

Exposure Duration

yr

RBCA

Residential = 30

Industrial/Commercial = 25

Construction Worker = 1

EF

Exposure Frequency

d/yr

RBCA

Residential = 350

Industrial/Commercial = 250

Construction Worker = 30

erf

Error Function

unitless

Appendix C, Table G

Mathematical Function

f_oc

Organic Carbon Content of Soil

g/g

RBCA or Field Measurement (See Appendix C, Table F)

Surface Soil = 0.006

Subsurface Soil = 0.002 or

Site-Specific

GW_comp

Groundwater Objective at the Compliance Point

mg/L

Appendix B, Table E, 35 IAC 620.Subpart F, or Equation R25 in Appendix C, Table C

Site-Specific

GW_source

Groundwater Concentration at the Source

mg/L

Equation R13 in Appendix C, Table C

Calculated Value

H'

Henry's Law Constant

cm³_water/cm³_air

Appendix C, Table E

Chemical-Specific

i

Hydraulic Gradient

cm/cm (unitless)

Field Measurement (See Appendix C, Table F)

Site-Specific

I

Infiltration Rate

cm/yr

RBCA

30

IR_air

Daily Outdoor Inhalation Rate

m³/d

RBCA

20

IR_soil

Soil Ingestion Rate

mg/d

RBCA

Residential = 100

Industrial/Commercial = 50

Construction Worker = 480

IR_w

Daily Water Ingestion Rate

L/d

RBCA

Residential = 2

Industrial/Commercial = 1

K

Aquifer Hydraulic Conductivity

cm/d for Equations R15, R19 and R26 cm/yr for Equation R24

Field Measurement (See Appendix C, Table F)

Site-Specific

K_oc

Organic Carbon Partition Coefficient

cm³/g or L/kg

Appendix C, Table E or Appendix C, Table I

Chemical-Specific

Symbol

Parameter

Units

Source

Parameter Value(s)

k_s (non-ionizing organics)

Soil Water Sorption Coefficient

cm³_water/g_soil

Equation R20 in Appendix C, Table C

Calculated Value

k_s (ionizing organics)

Soil Water Sorption Coefficient

cm³_water/g_soil

Equation R20 in Appendix C, Table C

Chemical and pH-Specific (See Appendix C, Table I)

k_s (inorganics)

Soil Water Sorption Coefficient

cm³_water/g_soil

Appendix C, Table J

Chemical and pH-Specific

L_s

Depth to Subsurface Soil Sources

cm

RBCA

100

LF_sw

Leaching Factor

(mg/L_water)/ (mg/kg_soil)

Equation R14 in Appendix C, Table C

Calculated Value

M

Soil to Skin Adherence Factor

mg/cm²

RBCA

0.5

Pe

Particulate Emission Rate

g/cm²-s

RBCA

6.9 • 10^-14

RAF_d

Dermal Relative Absorption Factor

unitless

RBCA

0.5

RAF_d (PNAs)

Dermal Relative Absorption Factor

unitless

RBCA

0.05

RAF_d (inorganics)

Dermal Relative Absorption Factor

unitless

RBCA

0

RAF_o

Oral Relative Absorption Factor

unitless

RBCA

1.0

RBSL_air

Carcinogenic Risk-Based Screening Level for Air

μg/m³

Equation R9 in Appendix C, Table C

Chemical-, Media-, and Exposure Route-Specific

RBSL_air

Noncarcinogenic Risk-Based Screening Level for Air

μg/m³

Equations R10 in Appendix C, Table C

Chemical-, Media-, and Exposure Route-Specific

RfD_i

Inhalation Reference Dose

mg/kg-d

IEPA (IRIS/HEAST^a)

Toxicological-Specific

RfD_o

Oral Reference Dose

mg/(kg-d)

IEPA (IRIS/HEAST^a)

Toxicological-Specific (Note: for Construction Worker use subchronic reference doses)

SA

Skin Surface Area

cm²/d

RBCA

3,160

Symbol

Parameter

Units

Source

Parameter Value(s)

S_d

Source Width Perpendicular to Groundwater Flow Direction in Vertical Plane

cm

Field Measurement

For Migration to Groundwater Route: Use 200 or Site-Specific

For Groundwater remediation objective: Use Site-Specific

S_w

Source Width Perpendicular to Groundwater Flow Direction in Horizontal Plane

cm

Field Measurement

Site-Specific

SF_i

Inhalation Cancer Slope Factor

(mg/kg-d)^-1

IEPA (IRIS/HEAST^a)

Toxicological-Specific

SF_o

Oral Slope Factor

(mg/kg-d)^-1

IEPA (IRIS/HEAST^a)

Toxicological-Specific

THQ

Target Hazard Quotient

unitless

RBCA

1

TR

Target Cancer Risk

unitless

RBCA

Residential = 10^-6 at the point of human exposure

Industrial/Commercial = 10^-6 at the point of human exposure

Construction Worker = 10^-6 at the point of human exposure

U

Specific Discharge

cm/d

Equation R19 in Appendix C, Table C

Calculated Value

U_air

Average Wind Speed Above Ground Surface in Ambient Mixing zone

cm/s

RBCA

225

Μg_w

Groundwater Darcy Velocity

cm/yr

Equation R24 in Appendix C, Table C

Calculated Value

VF_p

Volatilization Factor for Surficial Soils Regarding Particulates

kg/m³

Equation R5 in Appendix C, Table C

Calculated Value

VF_samb

Volatilization Factor (Subsurface Soils to Ambient Air)

(mg/m³_air)/(mg/kg_soil) or kg/m³

Equation R11 in Appendix C, Table C

Calculated Value

Symbol

Parameter

Units

Source

Parameter Value(s)

VF_ss

Volatilization Factor for Surficial Soils

kg/m³

Use Equations R3 and R4 in Appendix C, Table C

Calculated Value from Equation R3 or R4 (whichever is less)

W

Width of Source Area Parallel to Direction to Wind or Groundwater Movement

cm

Field Measurement

Site-Specific

w

Average Soil Moisture Content

g_water/g_soil

RBCA or Field Measurement (See Appendix C, Table F)

0.1, or

Surface Soil (top 1 meter) = 0.1

Subsurface Soil (below 1 meter) = 0.2, or

Site-Specific

X

Distance along the Centerline of the Groundwater Plume Emanating from a Source. The x direction is the direction of groundwater flow

cm

Field Measurement

Site-Specific

α_x

Longitudinal Dispersivity

cm

Equation R16 in Appendix C, Table C

Calculated Value

α_y

Transverse Dispersivity

cm

Equation R17 in Appendix C, Table C

Calculated Value

α_z

Vertical Dispersivity

cm

Equation R18 in Appendix C, Table C

Calculated Value

δ_air

Ambient Air Mixing Zone Heights

cm

RBCA

200

δ_gw

Groundwater Mixing Zone Thickness

cm

RBCA

200

θ_as

Volumetric Air Content in Vadose Zone Soils

cm³_air/cm³_soil

RBCA or Equation R21 in Appendix C, Table C

Surface Soil (top 1 meter) = 0.28

Subsurface Soil (below 1 meter) = 0.13, o r

Gravel = 0.05

Sand = 0.14

Silt = 0.16

Clay = 0.17, or

Calculate Value

Symbol

Parameter

Units

Source

Parameter Value(s)

θ_ws

Volumetric Water Content in Vadose Zone Soils

cm³_water/cm³_soil

RBCA or Equation R22 in Appendix C, Table C

Surface Soil (top 1 meter) = 0.15

Subsurface Soil (below 1 meter) = 0.30, or

Gravel = 0.20

Sand = 0.18

Silt = 0.16

Clay = 0.17, or

Calculated Value

θ_T

Total Soil Porosity

cm³/cm³soil

RBCA or Equation R23 in Appendix C, Table C

0.43, or

Gravel = 0.25

Sand = 0.32

Silt = 0.40

Clay = 0.36, or

Calculated Value

λ

First Order Degradation Constant

d^-1

Appendix C, Table E

Chemical-Specific

π

pi

3.1416

ρ_s

Soil Bulk Density

g/cm³

RBCA or Field Measurement (See Appendix C, Table F)

1.5, or

Gravel = 2.0

Sand = 1.8

Silt = 1.6

Clay = 1.7, or

Site-Specific

ρ_w

Water Density

g/cm³

RBCA

1

τ

Averaging Time for Vapor Flux

s

RBCA

9.46 • 10⁸