25 Pa. Code § 250.308 - Soil to groundwater pathway numeric values
MSCS = MSCGW ((Koc * foc) + [thgr]w/[rho]b).
where: MSCS (mg/kg) = the generic value for a regulated substance in soil
MSCGW (mg/L) = MSC of a regulated substance in groundwater
Koc (L/kg) = organic carbon partition coefficient for a regulated substance
foc = fraction of organic carbon in soil (default value = 0.0025)
[thgr]w = water-filled porosity of soil (default value = 0.2)
[rho]b (kg/L) = dry bulk density of soil (default value = 1.8 kg/l)
DF = dilution factor (default value = 100)
MSCS = MSCGW (Kd + [thgr]w/[rho]b).
where: MSCS (mg/kg) = the generic value for the inorganic regulated substance in soil
MSCGW (mg/L) = MSC of the inorganic regulated substance in groundwater
Kd (L/kg) = soil to water partition coefficient for the inorganic regulated substance
[thgr]w = water-filled porosity of soil (default value = 0.2)
[rho]b (kg/L) = dry bulk density of soil (default value = 1.8 kg/L)
DF = dilution factor (default value = 100)
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where: Csoil(it) (mg/kg) = concentration of regulated substance in soil at layer i at time increment TI
Csoil(i(t-1)) (mg/kg) = concentration of regulated substance in soil at layer i at time increment immediately preceding TI
Csoil(i+1)(t-1) (mg/kg) = concentration of regulated substance in soil at layer immediately above layer i at time increment immediately preceding TI
R (cm/yr) = recharge rate of water infiltrating soil (default value = 33 cm/yr)
DI (feet) = thickness of each layer i of soil (default value = 1 foot)
[rho]b (kg/L) = dry bulk density of soil (default value = 1.8 kg/L)
360 (month-cm/yr-ft) = conversion factor
TI (months) = time duration of each time increment
[thgr]W = water-filled porosity (default value = 0.2)
Caq(i(t-1)) (mg/L) = concentration of regulated substance in soil pore water at layer i at time increment immediately preceding TI
Caq(i+1)(t-1) (mg/L) = concentration of regulated substance in soil pore water at layer immediately above layer i at time increment immediately preceding TI
Kd (L/kg) = soil to water partition coefficient for the regulated substance where five different contaminant-specific values are used: 2.5, 5, 10, 100 and 1,000.
Kd values of organic regulated substances are based on the following equation:
Kd = (foc)(Koc)
where: foc = fraction of organic carbon in soil (default value = 0.005)
Koc (L/kg) = organic carbon partition coefficient for a regulated substance
Notes
The provisions of this § 250.308 amended under sections 104(a) and 303(a) of the Land Recycling and Environmental Remediation Standards Act (35 P.S. §§ 6026.104(a) and 6026.303(a)); and section 1920-A of The Administrative Code of 1929 (71 P.S. § 510-20).
This section cited in 25 Pa. Code § 250.304 (relating to MSCs for groundwater); 25 Pa. Code § 250.305 (relating to MSCs for soil); 25 Pa. Code § 250.310 (relating to minimum threshold MSCs); 25 Pa. Code § 250.312 (relating to final report); 25 Pa. Code § 250.604 (relating to fate and transport modeling requirements for exposure assessments); and 25 Pa. Code § 271.1 (relating to definitions); and 25 Pa. Code § 287.1 (relating to definitions).
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