§259.350. Equations for Calculating Site-Specific Soil Cleanup Objectives

a)         Site-specific soil cleanup objectives for pesticides are determined by the following equation:

 

Where:

 

SCO	=	soil cleanup objective (mg/kg)
Cw	=	target soil leachate concentration (mg/L)
Koc	=	organic carbon partition coefficient (L/kg)
foc	=	organic carbon content of soil (kg/kg)
Θw	=	water-filled soil porosity (Lwater/Lsoil)
Θa	=	air-filled soil porosity (Lair/Lsoil)
H'	=	Henry's law constant (dimensionless)
Ρb	=	dry soil bulk density (kg/L)

 

References:

 

"Soil Screening Guidance:  User's Guide", p. 29, eq. 10.

 

"Soil Screening Guidance:  Technical Background Document", p. 37, eq. 24.

 

1)         The target soil leachate concentration can be determined by the following equation:

 

 

Where:

 

Cw	=	target soil leachate concentration (mg/L)
DF	=	groundwater dilution factor (dimensionless)
GWobj	=	groundwater cleanup objective (mg/L)

 

2)         The dilution factor can be determined by the following equation:

 

 

Where:

 

DF	=	groundwater dilution factor (unitless)
K	=	aquifer hydraulic conductivity (m/yr)
i	=	hydraulic gradient (m/m)
d	=	mixing zone depth (m)
R	=	groundwater recharge rate (m/yr)
L	=	length of contaminated soil parallel to groundwater flow (m)
W	=	width of contaminated soil perpendicular to groundwater flow (m)

 

b)         Site-specific soil cleanup objectives for nitrate as nitrogen can be determined by the following equation:

 

 

Where:

 

L	=	Liter
Cw	=	Target soil leachate concentration (mg/L)

 

c)         Site-specific soil cleanup objectives for ammonium can be determined by the following empirical equation:

 

 

Where:

 

CEC

=

cation exchange capacity (meq/100g)

 

Reference: 

 

Potential Soil Cleanup Objectives for Nitrogen-Containing Fertilizers at Agrichemical Facilities, Soil and Sediment Contamination.

 

d)         The default values for the equations in subsections (a) and (b) of this Section are:

 

Parameter		Description		Default Value
DF		Groundwater dilution factor		30 (dimensionless)
foc		Organic carbon content of soil		0.008 kg/kg (0.8%) surface or 0.002 kg/kg (0.2%) subsurface
Θa		Air-filled soil porosity		0.2 (20%) Lair/Lsoil
Θw		Water-filled soil porosity		0.2 (20%) Lwater/Lsoil
Ρb		Dry soil bulk density		1.6 kg/L
H'		Henry's law constant		see Appendix E
Koc		Organic carbon partition coefficient		see Appendix E
GWobj		Groundwater cleanup objective		see Appendix D
CEC		Cation exchange capacity		see Appendix F

 

(Source:  Amended at 32 Ill. Reg. 1308, effective January 21, 2008)