Alert Route Planning for Xcel Energy Nuclear Power Plants in Minnesota
By Jeff Reinhart, St. Cloud State University
Nuclear power plants are required by FEMA to have an alert system for the area within 10 miles of the plant to alert the public of an incident. Xcel Energy employs an alert system which uses sirens (also used for severe weather warnings) to broadcast an alert tone to all residents within 10 miles of the plant. After hearing the alert from the sirens, residents can then listen to any Emergency Alert System broadcast for further information. There must also be a backup system available to handle any failure of the primary siren alert system.
That backup system is a series of routes that emergency personnel can drive while broadcasting the alert tone from their vehicles. The Spatial Analysis Research Center (SARC) at St. Cloud State University worked with Xcel Energy, and Dakota, Goodhue, Sherburne, Wright, and Pierce (WI) counties to provide alert route maps and directions for the Prairie Island and Monticello nuclear power plants.
Creation of Alert Routes at the Spatial Analysis Research Center
The approximate broadcast range of the emergency vehicle alert tone is 400 feet. Houses outside of the 400 foot buffer from the road network require that the driveway to the house be routed to ensure that the alert tone would reach the house. The first step in the process was to find these houses and digitize the houses and driveways. Using aerial imagery, road networks, and parcel polygons provided by the counties, houses were found by isolating areas not within the 400 foot road network buffer, then using a combination of the aerial imagery and parcel polygons to visually identify the houses in those areas. Once the houses were identified and digitized, their driveways were added to the road network.
The next step in the process was to create routes for each siren. It is a FEMA requirement that the backup system is able to notify residents within 45 minutes of knowledge of a siren failure. Fifteen minutes was subtracted from that 45 minute requirement in order to allow emergency personnel time to access route directions (either through printed maps or onboard computers in the squad car) and to reach the route starting point. Each route was then designed to be able to be driven in less than 30 minutes, thus ensuring the 45 minute requirement is met.
To maximize efficient use of resources, it was desirable to have as few routes as possible for each siren. Test routes were created by SARC and driven by the counties to ascertain the average mph for a particular area (not to exceed 25 mph). Using the average mph for each area, maximum route lengths were determined. Routes were then created that were less than the calculated maximum lengths and that minimized the number of routes per siren.
After creation of the routes was completed, point features were digitized next to intersections to display map labels that correlated with written descriptions of route directions, which were manually typed into the direction point attribute table (see Figure 1
). The attribute tables for the direction points were then exported and copied to Microsoft Word documents to provide accessibility to Xcel and county emergency personnel. Routes and supporting information created by individual analysts were aggregated to a single geodatabase. From that geodatabase, map documents were created and exported to PDFs (see Figure 2
The resulting product for each county is a set of ArcMap documents, supporting base data, and route geodatabases that will allow for future updates to the alert route PDF map set and accompanying Word documents. For SARC, the project was a great opportunity for SCSU students to further develop their GIS skills. For Xcel Energy, it was a cost effective way to diversify their emergency notification system. For the involved counties, it was an assurance that Xcel Energy is working to keep their citizens safe by providing the resource of the new routes in addition to quality siren performance.