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Vol. 9  No. 2



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Soil/Water Partitioning Calculator

Determining the partitioning of contaminants between soil and water at a site is an important part of any assessment.  The following calculator uses the EPA soil/water partition equation for organic contaminants (Soil Screening Guidance Technical Support Document, EPA, 1996). This equation is used to relate the contaminant concentrations in soil moisture to the total concentration detected in a soil sample.

Where:           Ct = soil concentration (mg/kg)

                     Cw = aqueous concentration (mg/L)

                     koc = soil organic carbon/water partition coeffiecient (L/kg)

                    foc = fraction organic carbon (kg/kg)

                     Pw = water-filled soil porosity

                     Pa = air filled soil porosity

                     Pb = dry soil bulk density (kg/L)

                     Hd = dimensionless Henry’s Law












This equation can be used for several regulatory purposes, including RBCA in several states.  The newly released RBCA Tool Kit for Chemical Releases v2.0 makes calculations and report writing for RBCA regulations significantly easier.



EPA, 1996. Soil Screening Guidance Technical Support Document.



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**NEW** RBCA Tool Kit for Chemical Releases v 2.0

The RBCA Tool Kit for Chemical Releases is a comprehensive modeling and risk characterization software package designed to meet the requirements of the ASTM Standard Guide for Risk-Based Corrective Action (E-2081) for Tier 1 and Tier 2 RBCA evaluations for chemical release sites in addition to traditional risk assessment calculations. The software combines contaminant transport models and risk assessment tools to calculate baseline risk levels and derive risk-based cleanup standards for a full array of soil, groundwater, surface water, and air exposure pathways. The ease-of-use features and streamlined graphical interface features of this software make it an essential tool for handling RBCA and generic risk assessment calculations for both simple and sophisticated problems.

Features:So What's New?


Exposure Pathway Evaluation:   Risk-based evaluation of groundwater, surface water, surface soil, outdoor air and indoor air exposure pathways, for residential, commercial, and user-defined receptors:

· Groundwater ingestion
· Surface water recreational contact and fish consumption
· Combined direct contact with surface soils (incidental ingestion, dermal absorption, inhalation of vapors and particulates, and consumption of homegrown vegetables)
· Outdoor and indoor inhalation of vapors emanating from soil or groundwater sources.


Fate and Transport Models:   Fate and transport models for all exposure pathways address a wide array of chemicals, including petroleum hydrocarbons (including TPH), metals, chlorinated solvents, pesticides, and more.  Multiple points of exposure (POEs) allow analysis of actual vs potential points of exposure in the same run. An array of default transport parameters provided for various soil types. F&T models include:

· Soil and groundwater source depletion
· ASTM and USEPA (SSG) outdoor air volatilization
· Johnson & Ettinger and Groundwater Mass Flux indoor air models
· ASTM soil leaching model, with decay options
· Dual-equilibrium desorption
· Point-source air dispersion
· Domenico groundwater solute transport, with decay options


Transient Modeling Options:   In addition to steady-state air, soil, and groundwater exposure models, the RBCA Tool Kit allows transient groundwater modeling analysis to help estimate not only how high but how soon exposure could occur.

Chem/Tox Database:   Contains over 600 of chemicals, including organic solvents, petroleum hydrocarbons (including TPH fractions), pesticides, metals, and more.  The user selects the chemical of concern and the key data loads automatically.  Multiple database files can be customized and maintained by the user for location or project-specific values.


User-friendly Interface:   Streamlined graphical interface guides the user through the RBCA evaluation process.  Features include convenient unit selection and conversions, importing and exporting, and report printing options.

Reports:   Produces report-quality output tables of baseline risk and cleanup standards and report-ready summary for each chemical.

For more info click here:  RBCA Tool Kit for Chemical Releases
To purchase click here: Order Online

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