Using Your Hydraulic Model for the ISO Audit

May 11, 2018

By Stefanie Farrell

Fire department employees around the nation are very cognizant of what “ISO ratings” can mean to a community.  As they know, these ratings come from the Insurance Services Office (ISO), and classify a community’s ability to suppress fires through a grade or “rating” of 1 to 10.

The ISO uses several criteria in determining the classification/rating; the water component criteria accounts for approximately 40% of that. Therefore, in August 2017, Maryville Fire Department Administrative Captain Mike Caylor approached the city’s Assistant Environmental Engineer Jessica Cooper about a new calibrated hydraulic model about which he had heard. Captain Caylor was hopeful that the fire department might be able to use the model to improve their ISO rating.

LDA Engineering had worked with the Maryville Water and Sewer Department earlier that summer to develop the model to insure the water distribution system has the capacity to meet both current and future water needs.  Maryville is a fast-growing city with growing demands on water capacity; city engineers recognized the importance of insuring that water needs are met so that city continues to thrive as a strong community and developed the model with that in mind.

Caylor and Cooper worked together to develop a plan for using the model to improve the ISO ratings.  By taking this action, the city gained an additional benefit beyond monitoring current water needs and planning for the future. When actual field flow tests were used in comparison with the model’s projections, they were within the 20% (of the model projection) as required by the ISO. Therefore, the results of the well-calibrated model can be used in lieu of an actual field flow test.  The fire and water departments will continue working together to determine which field tests can be avoided, saving both water and time in the future.

Ultimately, the City of Maryville earned 90% of the maximum points possible for the water supply portion of the classification.  The new classification, which went into effect on March 1, 2018, reflected a rating of Class 2, the second highest classification rating.  This new rating should provide residents and businesses with additional peace of mind about fire suppression; in addition, the new rating also has the added benefit of potentially lowering insurance rates for property owners.

The calibrated hydraulic model developed by the City of Maryville has been useful for not only insuring water stability for today and for the future, but also providing continuing potential for saving water and money and improving fire safety through utilization during the ISO Audit process. As was the experience of City of Maryville, when water and fire departments work together to support a reliable water distribution system, the impact on the community is significant.

If you are a water professional and would like to learn more about this project, you can hear LDA engineers Stefanie Farrell and Will Witcher talk about the experience at the upcoming 2018 Water Professionals Conference taking place in Nashville in July.