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Point Source Calculator Version 1.05 (PSC v1.05)

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OPPT uses aquatic models to estimate chemical concentrations in fish tissue, surface water, porewater and sediment. These estimated concentrations are used to assess exposure to aquatic organisms, humans, and the environment. One of the models that OPPT uses to estimate chemical concentrations in water column, porewater, and sediment from point sources is the Point Source Calculator Version 1.05 (PSC v1.05).

PSC v1.05 is a user interface that processes input and output for the Variable Volume Water Model (VVWM). PSC was named to reflect that it will mainly be used to assess releases from an effluent pipe of a waste water treatment plant or direct industrial discharger (point source). PSC assesses partitioning and degradation in the modeled environment to estimate water column, porewater and sediment concentrations of the chemical.  PSC v1.05 requires physicochemical parameters of the chemical of concern (sorption coefficient or Koc), mass releases per day of the chemical of concern and characterization of the receiving water body (flow rate and weather data). The model generates an output file with water, porewater and sediment concentrations of the chemical each day in the modeled environment as well as average values over different time periods to compare to hazard values.

Download and Install PSC v1.05

Download the PSC v1.05 model:  PSC v1.05.msi(984 K)

Weather files:

The PSC v1.05 Manual and User Guide provides additional information on surface water, porewater and sediment modeling, modeling inputs, and approaches used to develop PSC v1.05.

Download PSC v1.05 User Guide

The PSC v1.05 user guide contains information on the equations and defaults used in the model. Refer to this PSC v1.05 Manual and User Guide for instructions on how to use PSC v1.05.

Terms and conditions of use

  • Permission is granted for individuals to download and use the software on their personal and business computers. Users may not alter, modify, merge, adapt, or prepare derivative works from the software.
  • Professional judgment is needed to determine adequacy and applicability of the models and methods provided in PSC v1.05.

How should I send comments to EPA about PSC v1.05?

EPA is interested in your feedback from both a scientific and a computer user perspective. Please use this contact form or e-mail one of the points of contact listed below.

Dirk F. Young, U.S. EPA
U.S. Environmental Protection Agency
Office of Pesticides Program
Environmental and Fate Effects Division

David Tobias, U.S. EPA
U.S. Environmental Protection Agency
Office of Pollution Prevention and Toxics
Risk Assessment Division

Frequently Asked Questions

Questions and answers for how to download, access, and operate PSC v1.05

What Type of Hardware and Software Requirements are required for PSC v.1.05?

PSC v.1.05 is a stand-alone executable file programmed with Visual Basic and Fortran, and it is compatible with Windows 10 versions of Microsoft.

Has PSC v.1.05 been peer reviewed?

An external (i.e., by scientists outside of EPA) peer review of VVWM was conducted by FIFRA Scientific Advisory Panel in 2004. PSC v1.05 is an extension of this model using the same principles.

What are differences between PSC v1.05 and E-FAST v2.0?

PSC v1.05, based on VVWM, adds another surface water model to OPPT’s toolbox for use in estimating exposures. Depending on the specific chemical and exposure scenario being assessed, OPPT may use PDM (within E-FAST), PSC v1.05, or other Agency surface water models to estimate exposures. PSC v1.05 evaluates the partitioning of the chemical between air, water and solids whereas E-FAST v2.0 calculates a water concentration by dividing the mass release by the stream flow and does not consider partitioning. PSC v1.05 also incorporates degradation half-lives for the water and sediment compartments but E-FAST v2.0 does not consider any degradation. PSC v1.05 models environmental concentrations based on daily mass releases and stream flows; however, E-FAST v2.0 performs a statistical evaluation of one value for mass loading compared against the statistical characterization of the receiving water body. See the documentation for PSC and E-FAST for a fuller explanation of model calculations.

What Built-in Features (media and model parameters) are available for PSC v1.05 and E-FAST v2.0?

The table below contains a summary of PSC v1.05 and E-FAST v2.0.

BUILT-IN FEATURES FOR EACH MODEL Point Source Calculator Version 1.05 E-FAST Version 2.0
Water column
Includes partitioning  
Includes degradation, photolysis, hydrolysis, and volatization  
Requires Koc for calculation  
Calculates doses for general population and consumers  
Shows ratio of the total number of days exceeding the CoC to the total number of days of release
Uses 1Q10 (acute SWC), 7Q10 (chronic SWC), and harmonic mean (non-carcinogenic and carcinogenic human health SWC) to calculate chemical concentrations for one site and many sites  
Uses upper 90th ranked peak (acute values) or average (chronic, 4-day, 7-day, etc.) to calculate chemical concentrations for one site only  
Time-series, weather-based mode  

When to consider using PSC v1.05

PSC v1.05 is a higher tier model that requires more inputs for performing an exposure assessment. The model allows for estimation of sediment exposures and could be used in risk assessment for benthic organisms. The PSC v1.05 model also may be useful for evaluating chemicals that partition strongly to air or sediment when the E-FAST’s assumption that all of the chemical remains in the water is simplistic for the exposure assessments.