CTEH^® performs atmospheric dispersion modeling (ADM) for emergency and planning situations. ADM is used to estimate temporally- and spatially-resolved atmospheric concentrations of a chemical by using release, meteorological, and topographical information. Release rate estimates are developed by CTEH chemical engineers using state-of-the-science algorithms and estimation tools. Meteorological information is obtained through multiple methods, and topographical information is included where appropriate. This important estimation process helps the toxicology component of CTEH^® to assign areas of risk to a particular event.

Models Used

CTEH^® uses SAFER STAR^TM (SAFER) to help manage an emergency and to provide early warning to those who may risk exposure to a potentially harmful substance. SAFER accurately models the effects of chemical accidents (toxic releases, fires and explosions). The program includes state-of-the-science algorithms for addressing atmospheric dispersion, thermal radiation and blast overpressure modeling. In addition, SAFER provides mapping and topographical databases for the region of interest. Once the release site is identified, SAFER rapidly assembles appropriate maps and topographical data. Meteorology may be obtained from a mobile weather station or by interfacing to remote weather information (obtained from Internet sites or dedicated weather service providers).

Sophisticated Modeling Algorithms: SAFER includes several powerful scientific calculations of Release Rates, Source Dynamics, Vapor Cloud Dispersion, Structural Infiltration, Fires, Explosions, Back Calculation and Special Algorithms for unique situations. These complex equations quickly and accurately calculate the impact of potential fires, imminent explosions, and toxic releases on the surrounding community.

Flexible Interface: SAFER provides the user with the options of working with English or Metric measurements, several different mapping programs, including GIS formats and satellite imagery, and many different languages such as French, Dutch, Portuguese, Spanish, German, and Chinese.

User-Friendly: The familiar Windows XP environment provides menus, list boxes, pull-down lists, notebook tabs, entry fields, push buttons, icons, and status bars to aid in the presentation of data. Data transmission through a network and an extensive on-line help facility are also available.

Additional applications may include: contingency back-up measure; disaster prevention training tool; legal and financial protective hedge; and community and media relations communications mechanism. SAFER allows the user to quickly understand the magnitude and scope of the incident, as well as manage the event from thousands of miles away. This ability greatly reduces business downtime compensation due to evacuation, potentially saving an organization millions of dollars. It is also important to note that SAFER can be used to educate and train employees, thereby greatly reducing the probability of having a major release event.

A carrier of chemicals may be subjected to legal claims as a result of a real or imagined release. Should this happen, appropriate meteorological and chemical data, recorded and saved by SAFER, may be presented as powerful evidence to assist in the litigation or potentially preclude litigation. Properly relating information to the general public is extremely important both before and after an emergency occurs. Used appropriately, SAFER will help allay the fears of local communities through scenario illustrations and software demonstrations. Event simulations may help in enabling a proactive, non-threatening image to the community before an event occurs, and will help maintain the company's credibility in post-event scenarios as well.

CTEH^® employs SAFER TRACE^TM(TRACE), another product of Safer Systems, L.L.C., to perform engineering and planning analyses for projects requiring additional detail. TRACE offers the same modeling platform as SAFER STARTM, and is also a tool for meeting regulatory requirements and industry initiatives such as OSHA PSM, SARA Title III, EPA RMP Rule and more. Also, TRACE includes the capability to model releases of particulate matter. Emergency planning and consequence analysis are the primary functions served by TRACE.

ISCST3 and AERMOD are EPA models which are used to evaluate short-term and long-term releases of neutrally-buoyant chemicals and particles. These models utilize meteorological data and upper-air meteorological information directly from the National Climatic Data Center, and feature a wide range of input and output options, such as volume sources, line sources, flagpole receptors, and fixed or variable grid receptors. CTEH^® has also employed these models for emergency scenarios and short-term releases. Finally, these models feature an interface with the Building Profile Input Program (BPIP). BPIP allows the user to input detailed information about buildings in an industrial complex. The effect of building wakes and wind channeling between buildings on the dispersion of the released chemical is estimated with this state-of-the-science tool.

SLAB is another EPA model which is used to model dense gases. For applications which mandate its use, or to use in comparisons with model results obtained with SAFER STARTM, which also provides specialized modeling for dense gases.

CTEH^® also houses expertise in urban air quality modeling, including related atmospheric chemistry and physics, specializing in ozone formation. CTEH^® staff members have experience with the Comprehensive Air quality Model with eXtensions (CAMx), an urban airshed dispersion model used to assess impacts of chemical emissions on concentrations of chemicals falling under National Ambient Air Quality Standards regulations.