Although the city of Bozeman, Montana’s stormwater system has been silently producing front-page news for decades, it has typically only flowed into the spotlight because of an incident or an emergency. That all changed when the Montana Department of Environmental Quality (DEQ) audited the department and determined that the lack of a comprehensive stormwater system map was a violation of its federally-issued MS4 (Municipal Separate Storm Sewer System) permit. As serious as the infringement was, it also helped launch a long overdue mapping project in 2012 that would bring the underground workhorse to light.
Nearly two years later, Bozeman’s GIS department has not only inventoried and mapped 95 percent of its entire stormwater network. It has also created a detailed knowledge base to readily understand the "what and where" of any given asset at any time. And the new data-driven framework has enabled the city to transform stormwater from obscurity to a $1.2-million utility.
The objective of the $200,000 stormwater mapping project was to collect detailed, spatial-based data that could inform business decisions and be readily integrated into operations. Resources were tight — the GIS department had a project team of two and just one year to achieve the goal. Given the schedule, data requirements and safety elements, the City acquired two Trimble GeoExplorer® 6000 series GNSS handheld units. The handhelds would allow them to be highly mobile, efficiently collect centimeter-accuracy data and readily integrate the location data with their GIS system.
Field of Discovery
In January 2013, Kyle Mehrens, a GIS technician in the public works department, prepared for the field work scheduled for that spring. After months of research, Mehrens developed a set of 13 unique stormwater data layers such as manholes, pipes and inlets. Each layer included its own set of critical attributes such as the size of a manhole’s cover, its depth and its width. He then created a customized data dictionary in the Geo 6000’s software, which would prompt the user to record objects’ unique attributes.
Each morning a two-person field crew would consult a combination of in-house aerial photos and paper maps to determine which area of the city they would survey. Once on site, one person would ready the Geo 6000, set the unit on each stormwater feature and record the point, while the other would drive to the next mapping section. While the positioning data was being logged, the technician would also record critical attributes pertinent to the asset as well as environmental surroundings such as the presence of a curb and its type. After all feature data was collected, the mapper would move to the next set of objects and repeat the process. Typically the field crew could map about 200 features in an 8-hour day.
Using data from a nearby Trimble NetR9™ GNSS base station and Trimble GPS Pathfinder Office software, Mehrens would process the Geo 6000 data within one hour of receiving it from the field. Once processed and checked, he exported the data into the Esri database and assigned unique facilities IDs to
each feature collected. Because of the software development he did previously, some of the stormwater layers in the GIS were automatically populated with the GPS data attributes, creating an efficient workflow. Mehrens and his team mapped more than 10,000 features in just four months. They captured about 95 percent of the existing infrastructure including 93 miles (150 km) of pipe, 1,276 manholes and 3,059 inlets.
That detailed data led the way to their ArcGIS-based interactive stormwater map that offers a dynamic, layered blueprint of Bozeman’s entire stormwater network, down to the individual inlet or manhole. Publicly available online, users can access the map, click on any asset feature and view its associated attributes. Having such an accurate, digital and visual record of the stormwater system has been a great productivity boon and communication tool for the whole public works department. For example, Bozeman’s TV crews — the teams that use remote controlled video cameras to assess the structural integrity of the underground pipelines — proactively use the map to determine pipe sizes before going on site. Knowing pipe sizes in advance ensures they have the proper camera wheel sets to fit inside each pipe, saving valuable time in the field. The map enables Bozeman’s contracting community to identify where they need to erect stormwater control measures around their construction sites. Emergency responders can consult the map to track and monitor the path of a pollution event and prevent it from reaching waterways. Planners use the map in their consultations with developers to ensure stormwater practices are implemented. And citizens can use the map to report an event or to talk intelligently about stormwater concerns they have. Stormwater can now be integrated with the city’s asset management system. This integration enables crews to plan, track and update maintenance and repair work on any given piece of the network. And it also provides the ability to achieve further permit compliance because they have the data and tools to produce detailed maintenance reports, a major component to comply with regulations.
Perhaps most significantly, the mapping project has provided the factual platform to drive the expansion of the stormwater program. With a complete inventory of the infrastructure and its condition, Mehrens and colleagues were able to successfully propose a 15-year, $1.2-million, multi-faceted improvement plan designed to regain the system’s health. With their new comprehensive stormwater dataset, public works personnel also have the tools and knowledge to determine if “no news” is truly “good news.”