Environmental Policy & Guidance

Site Conceptual Exposure Model (SCEM) Builder

EPA guidance on the preparation of Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) scoping documents requires the development of a Site Conceptual Exposure Model (SCEM) as a planning tool for public health and ecological risk assessments. RCRA corrective actions also require risk assessments to be conducted to determine the potential impacts to public health and the environment. To streamline this process, the Office of Environmental Policy and Guidance, RCRA/CERCLA Division (EH-413), created the SCEM Builder, a user-friendly computer application, to assist environmental restoration program managers (ERPMs) in preparing SCEMs.

SCEMs are used as a planning tool during the environmental site investigation phase to allocate finite financial and personnel resources to address data gaps, identify sources of contamination, release mechanisms, exposure pathways, and human or ecological receptors. The SCEMs include a visual presentation of site conditions and provide a narrative description of the assumptions used in the model. The ERPMs can use the information in SCEMs to develop risk assessment data quality objectives (DQOs) and prioritize field sampling activities, thereby reducing the uncertainty associated with risk characterization.

The SCEM Builder is a user-friendly computer graphics tool that considerably shortens the time required for the ERPM to generate SCEM diagrams and associated documentation. Once a SCEM has been constructed, the ERPM can quickly modify any of the variables. The SCEM Builder can then generate a range of SCEMs that reflect various "what-if" scenarios and allow for data uncertainties at the site to be bounded by the individual SCEMs.

The SCEM Builder consists of:

• Diagram Builder - The Diagram Builder enables the user to quickly construct or modify the SCEM variables, which include the primary, secondary, or tertiary source of contamination, the receptor, the release mechanism, and the exposure mechanism.
   
• Notes feature - The Notes feature allows the user to document details regarding each diagram element and any assumptions.
   
• Help System - The Help System consists of both Program Help, which relates to operation of the program, and SCEM Help, which relates to technical issues or concerns associated with environmental restoration sites.
   
• Diagram Information Screen - The Diagram Information Screen provides specific information about the diagram, such as title and creation date, and includes a note area.

The SCEM Builder was developed using Microsoft Visual Basic software and runs under either Windows 3.11 or Windows 95 operating systems You may experience difficulty runnung the SCEM Builder on a later version of Windows.

Download SCEM Builder

To download and install the SCEM Builder complete the following:

• Click here to download the self-extracting SCEM Builder archive file (3,068,195 bytes). Select an empty directory for the archive download.
   
• After the archive has been downloaded, exit from your Internet browser.
   
• Use the Windows Explorer or File Manager program to execute the archive self-extractor. (In the Windows Explorer or File Manager Toolbar, highlight the archive file, then select "Run" from the File Menu)
   
• The archive will create a number of files on your computer, including a file called "setup.exe." Execute this file to install the SCEM Builder program on your computer.

SCEM Builder Manual

The SCEM Builder User Manual (260,465 bytes, 47 pp.) is available as a portable document format (PDF) file. In order to view or print PDF files, Adobe Acrobat Reader or a similar viewer must be installed on your system. Please click here for more information on using Acrobat Reader with your Web browser and viewing and printing PDF files.

Feedback

If you have difficulty in downloading or installing the Site Conceptual Exposure Model (SCEM) Builder, contact our Webmaster. If you discover bugs or the program does not operate properly on your PC, please provide us with feedback.