Recent developments in the sophistication of GIS application programming interfaces (API) combined with advances in the science of atmospheric dispersion modeling, communications, and computer hardware have provided the platform for development of an atmospheric modeling system for emergency response. The Regional Atmospheric Response Center (Denver, Colorado) has developed an advanced system for predicting the path and impacts from toxic chemical emergencies. The Computer Assisted Protective Action Recommendations System (CAPARS) reflects the latest in integration between GIS, inter-application communication, and atmospheric dispersion modeling.

The Terrain Responsive Atmospheric Code (TRAC) model provides plume and health impact predictions within CAPARS. The TRAC model simulates realistic plume paths for releases and spills in the most complex terrain. In particular, CAPARS and TRAC are operational in one of the world's most demanding environments: emergency response at the U.S. Department of Energy's Rocky Flats Research Facility, a former nuclear weapons and plutonium manufacturing plant in the mountainous terrain of Colorado.

The integration of sophisticated atmospheric dispersion modeling, TRAC, with GIS technology is a major innovation within CAPARS. Utilizing ArcInfo as the foundation for spatial data management, CAPARS affords timely and accurate predictions and recommendations to emergency scenarios.

This paper summarizes the integration of sophisticated atmospheric modeling technology with a Geographic Information System (GIS), namely ArcInfo, to conduct rapid response assessments of health impacts following hazardous materials emergencies. The Regional Atmospheric Response Center is introduced. An upgraded atmospheric modeling system used at the Center, termed the Computer-Assisted Protective Action Recommendation System, is discussed. This paper reviews the design and implementation of CAPARS with a particular reference to issues of GIS application development and functional capabilities.

Meeting the challenges of planning, compliance, and emergency response to accidental airborne releases of hazardous materials is difficult and expensive, but they must be met for the protection of our workers, the public, the community, and the businesses that are essential to our economic strength. The answer lies in the recognition that the challenges discussed above are shared throughout the community. It is not necessary that each organization attack these problems alone, as is now the case. In fact, this is inefficient, wasting scarce resources and funds. The best solution is a common effort to address a common problem...

The mission of the Regional Atmospheric Response Center is to answer four critical questions associated with a hazardous materials emergency:

The Regional Atmospheric Response Center rapidly answers these questions and communicates the answers to response teams...fast enough to help protect people and the environment from a hazardous materials emergency at any time and anywhere along the Front Range Urban Corridor of Colorado.

To accomplish its mission, the Regional Atmospheric Response Center operates 24 hours a day, 365 days per year, maintaining an around-the-clock readiness for urgent response. A central facility, located in suburban Denver, Colorado houses the specialized equipment and staff needed to develop accurate plume predictions and communicate them rapidly to emergency responders.

In addition to its direct emergency response role, the Regional Atmospheric Response Center applies its advanced modeling technology and staff expertise to the related activities of emergency planning, emergency readiness, emergency drills, exercises and training, hazards assessments, risk assessments, and community risk communication.

The technological hub of the Regional Atmospheric Response Center is an advanced atmospheric modeling capability developed during more than ten years of research and application along the Colorado Front Range. The Computer-Assisted Protective Action Recommendation System (CAPARS) provides a variety of plume, weather, hazard, and related products with the accuracy and speed needed to support all levels of emergency response including first response teams. CAPARS is the technical backbone of the Regional Atmospheric Response Center.

Combining recent advances in the sciences of atmospheric dispersion modeling, geographical information management, communications, and computer hardware, CAPARS is more than a sophisticated atmospheric dispersion model-it is a truly integrated system. Seventeen major subsystems work together to form the overall functionality. The programs are organized in five primary subsystems:

Each primary subsystem contains one or more secondary subsystem swhich perform related functions. The following diagram presents the conceptual design of CAPARS.

The CAPARS capability includes a full featured Graphical User Interface (GUI) that serves as the primary communication link between the system user and CAPARS applications. The GUI uses point-and-click cursor position, multiple windows, pull-down menus, default data entries, extensive help facilities, and other state-of-the-art interface technology to ensure rapid, effective, and accurate transfer of information from the user to the system.

Data entry sessions available through the GUI include:

Rapid and reliable real-time information flow is one of the most important and critical functions of the Regional Atmospheric Response Center. CAPARS includes a communication subsystem designed to manage the multiple communications channels which acquire automated meteorological, source, and air quality data. The communication subsystem also manages the streams of output data driving displays, printers, and plotters, often at remote locations. Highly specialized communications such as computer-generated public address announcements, automated fax transmissions, and voice-activated commands may also be managed by this subsystem. The distribution of output data, maps, reports and recommendations, is defined in the Output Management subsystem. Direct user interaction is achieved through the GUI.

Atmospheric dispersion modeling is essential to predicting the path and danger from an atmospheric plume of hazardous materials. Atmospheric dispersion models are computer simulation programs which combine information about the source of a release and observations of wind and weather conditions with theories of atmospheric behavior to predict the spread and travel of a toxic release.

Because the atmosphere along the Colorado Front Range is complex and changeable, great care, and considerable sophistication, must be used in atmospheric dispersion modeling for the area. Recognizing this difficulty, the Department of Energy (DOE) developed a specialized atmospheric dispersion model for use along the Front Range of the Colorado Rocky Mountains. The Terrain-Responsive Atmospheric Code (TRAC) is the computer simulation model that has been used for emergency plume predictions at the Rocky Flats Site for more than five years. TRAC has been enhanced and redesigned using client/server approaches to satisfy the emergency response needs of the entire region through the Regional Atmospheric Response Center.

The TRAC model is based on a puff approach to modeling, in which small clouds of hazardous materials are tracked through the atmosphere in 3-D. Continuous releases (or plumes) are treated by creating overlapping puffs. The model predicts plume transport by developing wind flow patterns in three dimensions, then transporting puffs along independent, curved trajectories.

The key to this process is a realistic representation of wind flow patterns in complex terrain. TRAC predicts winds for more than 25,000 locations at 15-minute intervals using information on weather conditions, terrain, and surface cover. Puffs are allowed to follow the changing winds, spreading in response to atmospheric turbulence. The model also treats the important effects of building wakes, tornado dispersion, Chinook windstorms, rising plumes, settling of particles, fallout (deposition), surface roughness, and re-suspension of deposited material.

When the TRAC model is finished projecting plume transport, it generates raster arrays reflecting distributions of atmospheric concentration and ground deposition. The model then compares these assessments to health effects criteria (e.g., Protective Action Guidelines for radiological substances and Community Exposure Limits for non-radiological hazardous materials) to identify areas where specific protective actions should be taken. Through its close integration with the GIS subsystem in CAPARS, TRAC can identify target or sensitive populations such as schools, hospitals, and day care centers within the protective action zones.

Once the TRAC model has completed a simulation for a given set of meteorological data the Task Subsystem notifies the GIS server(s) to initiate conversion of the output data arrays into GIS compatible formats. An ArcInfo Data Server generates a series of time stamped output maps, using a combination of raster GRID data and conventional vector libraries. Maps are created based on preferences defined by the Output Management subsystem of the GUI, and distributed accordingly to appropriate devices. Output devices may include Intranet displays, remote devices, and Internet postings.

The display of maps and reports locally within the RARC site is managed independently by a separate ArcInfo Display Server. Additional Inter-Application Communication (IAC) servers are also utilized including a hardcopy plotting/printing server. The use of multiple ArcInfo servers helps to distribute GIS related data tasks in a fashion similar to parallel processing methodologies resulting in the provision of output in a timely fashion. The ArcInfo servers are used continually by TRAC and the Task Subsystem as the model refreshes it's simulations using newly acquired meteorological data every 15 minutes until the duration of the scenario has been satisfied. TRAC runs may also be initiated at any time by modifying input parameters in the GUI.

The integration of atmospheric dispersion modeling with Geographical Information System (GIS) technology is a major innovation previously not implemented with any operational atmospheric dispersion modeling system. A GIS combines the power of spatial database management and high resolution graphics to manage spatially-related information. GIS technology is ideally suited to support data management for the Regional Atmospheric Response Center, because almost all of the information used or produced in the Response Center is spatially-related. ArcInfo operates as a primary subsystem within CAPARS managing four key functional subsystems:

The integration of TRAC and GIS has been made possible, in part, by the advancement of inter-application communication capabilities within ArcInfo. Most applications utilizing GIS functions do so in an interactive fashion. Typically GIS is the central subsystem controlling all processing activities. However, in CAPARS GIS provides several different functions. ArcInfo provides the core spatial data management tools within CAPARS including both real time data conversion and management, as well as more conventional static database management, e.g. vector libraries and relational database capabilities. However, ArcInfo is used most importantly as a background server to support data conversion, data display, and hardcopy plotting and printing. Separate servers are used to support each requirement. In this regard the ArcInfo servers are not interactive. They are controlled directly by the Task Management subsystem, a C daemon running in memory, and operate completely seamless to the user. The ArcInfo servers operate as spatial data processors servicing the needs of an external program. Many would argue that GIS is finally put in its proper place.

The current release of CAPARS is also based on an AML (Arc Macro Language) GUI interface. The GUI has been designed using a desktop approach with a combination of pulldown, popup menus, and dialogue boxes. It is expected that future versions of CAPARS will migrate to more advanced API's using ArcInfo OCX functionality. Some initial scoping has also been done to investigate the use of Intranet - Internet browsers as viewing interfaces for the distribution of model output.

The development of CAPARS, TRAC and the GIS based subsystems is on-going. Since the implementation of the demonstration prototype in mid 1996 development has been on-going to move the system into a declared operational mode. Increasing demands and requirements of the system have extended the timeframe and application of CAPARS to a suite of related emergency response requirements. For example, the Regional Atmospheric Response Center and the Colorado State University are currently conducting a joint development project to improve CAPAR's ability to simulate non-radiological chemical hazards in six fundamental areas:

It is expected that the continued application of CAPARS to address more operational requirements will extend the development and functional capabilities.

Because each emergency management application is unique, a customized set of output products is designed for each municipality, industrial site, or response organization working with the Regional Atmospheric Response Center. The sections below illustrate the range of output products which are produced by CAPARS.

Airflow Patterns: The real-time wind patterns in the Denver region as analyzed by the TRAC model. The map visualizes airflow by curved lines known as "streamlines". Small arrows spaced along the lines indicate the direction of flow.

Plume Path and Timing: The predicted path and timing for a cloud of hazardous materials moving through the atmosphere. The display represents the "shadow" of the plume, whether the plume is overhead or touching the ground.

Exposure Levels Exceeding Level of Concern: The areas where the TRAC model has predicted that concentrations of or exposures to hazardous materials will exceed applicable levels of concern (guidelines for taking protective action).

Animated Plume Movement: The predicted path of a hazardous material plume can also be represented by an animated series of time stamped maps. MPEG movies can be automatically generated as output using a suite of different parameters to illustrate the plume prediction and path.

Protective Action Zones: The areas where exposures exceed the level of concern are expanded to match pre-planned boundaries (such as sectors or city boundaries) or recognizable geographical features (such as roads and railroads) to facilitate the communication and implementation of protective action recommendations in the field.

Hazardous Materials Inventory: The hazardous materials actually or typically stored at and near the emergency scene, as determined from SARA Title III information, Chemical Inventory databases, or other sources. Provided through the Source Inventory Subsystem within the GIS.

Special Groups Inside Protective Action Zone: Sensitive populations located within the Protective Action Zone. Examples may include day care centers, hospitals, schools, prisons, and rest homes. Provided automatically through the Geographical Base File Subsystem within the GIS.

Material Safety Data Sheets: Standard safety and response information summaries for the substances identified in the Hazardous Materials Inventory. Provided automatically by the GIS from a commercially-available Material Safety Data Sheet database.

Area Weather Information: A summary of current weather conditions at monitoring sites near the emergency scene. Data may include wind direction and speed, temperature, and precipitation. Provided automatically through the Meteorological Data Acquisition Subsystem.

A number of different reports and textual descriptions are generated by CAPARS. They include:

Responder Information: A summary of plume and weather information needed by on-scene responders to effectively mitigate the event. Information may include recommended command post location, immediate exclusion zone recommendation, fire fighter protection, fire and explosion hazards, and symptoms of acute overexposure to the hazardous materials involved in the emergency.

Protective Action Recommendation Summary: A clear, concise description of the Protective Action Recommendations and Protective Action Zone boundaries suitable for voice transmission to on-scene responders.

Notification Forms: Standardized forms for required regulatory and response notification, including automatic entry of available information and completion by the user through the Graphical User Interface.

Incident Weather Forecast: Specialized weather forecasts, automatically transmitted to response personnel.

An example analysis of a hypothetical hazardous materials release is presented below to illustrate the capabilities and products of the CAPARS modeling system.

The hypothetical emergency is a spill of chlorine from a railroad tanker car. In the scenario a freight train is traveling through the Boulder, Colorado area. While stopped at a siding a tanker car containing 30,000 gallons of chlorine is punctured. Approximately 4% of the car's contents quickly spill out onto the ground. Direct aerosolization of some chlorine, combined with vaporization from the spilled pool, results in the release of 4,000 kg of chlorine into the atmosphere over a period of 10 minutes. The hazardous cloud travels toward the southwest and west from the source, changing direction as the complex winds of this region vary.

Figure 8 depicts the predicted path and timing for the chlorine cloud moving through the atmosphere. The display represents the "shadow" of the plume, whether the plume is overhead or touching the ground. The plume path map is derived by merging temporal maps of varying resolutions. Note that areas are defined with a finer resolution shortly after the release (close to the source), compared to coarser area resolution at longer periods after the release (typically farther from the source). The varying resolution of the map automatically depicts the accuracy of the plume path prediction and provides a visual cue to the reliability of the conditions for emergency responders.

The Regional Atmospheric Response Center and the CAPARS represent a significant achievement in the integration of administrative approaches and technical development. In particular, the integration of GIS spatial data processing capabilities with sophisticated atmospheric dispersion modeling has provided an operational platform for rapid response to hazardous materials emergencies. GIS technology provides a critical function as a spatial data processor driven by external simulation models and programs. It is expected that future developments will continue to focus on extending the scientific basis and modeling capabilities of the TRAC model, while integrating new technical capabilities in spatial data processing and information distribution.

This paper was prepared for presentation at the Esri 1997 User Conference, San Diego, CA, July 1997.

CAPARS was developed jointly by AlphaTRAC, Inc. and Innovative GIS Solutions, Inc. under contract to the Regional Atmospheric Response Center. Readers are invited to contact Reed Hodgin at the RARC for more information.