RISC WorkBench
Detailed Description

RISC WorkBench

Introduction to RISC WorkBench

RISC WorkBench 4.0 is an easy-to-use software package designed for performing fate and transport modeling and human health risk assessments for contaminated sites. RISC WorkBench follows standard procedures outlined in the US EPA's Risk Assessment Guidance for Superfund (US EPA, 1989) to calculate exposure assessment, toxicity assessment, and risk assessment. RISC WorkBench also includes EnviroBrowser Pro, a completely customizable database for common environmental parameters used when conducting risk assessments. No other RISK package offers all this!

RISC WorkBench Interface

The RISC WorkBench follows a logical menu structure that takes you through the necessary steps to produce your risk analysis or contaminant transport model run. Simply complete the 6 steps outlined in RISC WorkBench to obtain results quickly. If you're not sure of an input parameter, simply launch the chemicals or environmental parameters database for a selection of common 'risk' parameters!

Step 1: Select Chemicals of Concern

RISC WorkBench allows you to select from over 86 common chemicals providing physical, chemical, and toxicity values or add new compounds.
Chemical Parameters Toxicity Parameters
CAS Number
Molecular Weight
Vapor Pressure
Henry's Law
Log Kow
Diffusion in Air
Diffusion in Water
Vegetable Uptake Factor
Degradation (high-end)
Degradation (low-end)
EPA Carcinogenic Classification
Ingestion Slope Factor
Inhalation Slope Factor
Dermal Slope Factor
Oral Reference Dose
Inhalation Reference Dose
Dermal Reference Dose
Oral-Soil Abs. Adjust. Factor
Oral-Water Abs. Adjust. Factor
Dermal-Water Abs. Adjust. Factor
Inhalation Abs. Adjust. Factor
Skin Permeability Coefficient
Maximum Contaminant Level (MCL)

Step 2: Define Exposure Pathways

In Step 2, the user may define the exposure scenario by selecting contaminated media(s), fate and transport models (if any), and associated exposure pathways. RISC WorkBench is set up so that in any single analysis, either human health exposure pathways can be evaluated or ecological/water quality concerns can be evaluated.

Built-in Fate & Transport Models include:

  • Leaching from vadose zone to groundwater
  • Dispersion, advection, retardation and degradation of groundwater as it moves in an aquifer
  • Saturated soil source at the water table impacting groundwater
  • Biodegradation of vapors in soil migrating to indoor/outdoor air
  • Emissions from groundwater to indoor air
  • Surface water mixing and sediment partitioning models that can be linked with groundwater model

Step 3: Determine Receptor Point Concentrations

The third step is to determine receptor point concentrations for the various media of concern specified in Step 2. There are two methods for determining receptor point concentrations; the user can enter receptor point concentrations directly into RISC WorkBench or enter source zone concentrations and then utilize chemical fate and transport models to estimate the receptor point concentrations. The method(s) to be used in Step 3 are determined by the choices made in Step 2

Step 4: Enter Surface Water & Sediment Criteria

In Step 4, the receptor(s) of concern are chosen and the receptor-specific intake parameters are entered. RISC WorkBench contains both deterministic and stochastic (Monte Carlo input) default data on exposure for many different types of receptors. The user is free to use the default data provided or to change the intake parameters to reflect actual site-specific values.

Step 5: Calculate Risk & Cleanup Levels

The potential carcinogenic risk and non-carcinogenic hazard are calculated using equations presented in EPA's Risk Assessment Guidance for Superfund (EPA, 1989a). The following exposure routes are considered in the software:
  • Dermal contact with contaminated soil
  • Ingestion of contaminated soil
  • Ingestion of contaminated groundwater
  • Dermal contact with contaminated groundwater (while showering)
  • Inhalation while showering
  • Inhalation of outdoor air (either from soil or groundwater emissions)
  • Inhalation of indoor air (either from soil or groundwater emissions)
  • Ingestion of surface water (e.g., while swimming)
  • Dermal contact with surface water
  • Ingestion of home-grown vegetables grown in contaminated soil
  • Ingestion of home-grown vegetables irrigated with contaminated groundwater
  • Ingestion of irrigation water (groundwater used outdoors)
  • Dermal contact with irrigation water.
  • Inhalation of irrigation water spray (from sprinklers, etc.)

Pathways 1-3 and 6-7 represent some of the more common exposure pathways for many petroleum contaminated sites (e.g., former gas stations). If surface water bodies are present on the site, exposure pathways 8 and 9 may be important. Pathways 11-14 represent the potential pathways associated with irrigation water and will usually only be of concern if the house has its own well while drinking water used in the house is provided by a municipality.

Step 6: View the Results

When the "Calculate Clean-up Levels" option is chosen from Step 5, RISC WorkBench can be used to "back-calculate" clean-up levels using the models and assumptions selected in the current analysis. In the "forward risk" assessment, risk is calculated from input or estimated receptor point concentrations and receptor input parameters. In the back-calculation, the user specifies target risks or concentrations (e.g., MCLs) and then the software calculates "allowable" source concentrations (clean-up levels). The clean-up levels represent source and/or receptor point concentrations for the chemicals of concern such that the risk levels are not exceeded for the scenario outlined.

There are several options for selecting targets in Step 5. The user may specify a target risk or hazard index either for individual chemicals or for a cumulative scenario where the risks are summed across all chemicals of concern. If groundwater or surface water is a receptor media, the user may enter target concentrations (e.g., MCLs in groundwater) for these media.

RISC WorkBench Output

RISC WorkBench Compared to the RBCA ToolKit

While slightly similar to the RBCA Toolkit, RISC WorkBench is more functional, flexible and user-friendly. The major differences are:

  • RISC WorkBench is developed as a stand-alone program with an intuitive graphical interface that follows a step-by-step procedure. (Microsoft Excel is only required when using the bonus Tier 1 spreadsheet and Surface Water Quality database.)
  • RISC WorkBench allows for pathway, compound, and receptor additivity.
  • The fate and transport models in RISC WorkBench can be used in the presence of phase-separated product.
  • There is a vadose zone model in RISC WorkBench.
  • The groundwater models are transient.
  • Probabilistic (Monte Carlo) exposure capabilities are provided in RISC WorkBench.
  • RISC WorkBench includes a critical pathway - indoor showering - missing in the RBCA Toolkit.
  • RISC WorkBench includes a customizable environmental parameters database with references.

Risk WorkBench Documentation

RISC WorkBench includes a comprehensive user's manual containing three in-depth example problems. Technical support is provided by phone, fax or e-mail.

Risk WorkBench Hardware Requirements

  • IBM 486 or compatible (or a PowerMac)
  • 8 MB RAM
  • 12 MB hard disk space
  • Microsoft Windows 95, 98, 2000 or NT
  • Microsoft Excel 5.0 or 7.0 (for optional spreadsheets only)

RISC WorkBench can be run without Excel, however, this will prevent the user from displaying the bonus RBCA Tier 1 table or accessing the full surface water and sediment criteria databases.