Can you dig it?
When a pipe breaks and the wastewater utility is unable to quickly locate its underground assets, then time becomes the enemy. Many communities, though, are updating their maps by sending employees armed with mobile geographic information systems (GIS) — complete with computerized maps and global positioning systems (GPS) — into the field to collect information and upload it into the permanent database at the office.
Until about two years ago, mapping underground utilities required survey-grade GPS equipment, which was expensive to purchase and operate. Now, less expensive and easy-to-use mobile GIS equipment with sub-foot accuracy is helping utilities keep track of their assets. “The primary return on investment comes from savings in staff time,” says David Larson, assistant county manager for York County, S.C., which bought integrated GPS/GIS equipment specifically for utility mapping. “Our crews can pinpoint infrastructure locations in minutes instead of hours.”
Bob Heien, Sioux City, Iowa, GIS manager, agrees that map accuracy saves time and money, saying that when crews are confident that underground pipes are located where the GIS maps indicate, they can start a repair as soon as they arrive on site. However, most water and wastewater utilities use mobile GIS to help them keep pace with growth. Hamilton Township, N.J.; Sioux City; and York County, S.C.; use GIS to plan construction of new subdivisions and office parks. York County and Sioux City are creating their first water and wastewater GIS maps, while Hamilton Township is updating older, less accurate digital maps.
Making new maps
In York County, responsibility for the water and wastewater systems is split between the engineering and public works departments. Engineering designs new installations and expansions, while public works repairs and maintains the infrastructure. Before GIS was available, if a pipe ruptured in the middle of the night, a public works technician had to drive to the county office, pick up a paper map of the area and then travel to the site for repairs. “If public works redlined their schematic, it didn’t take long for their maps to get out of sync with the engineering maps,” says Bryan Townsend, GIS administrator for the York County Management of Information Systems office. “Plus, it was inefficient for technicians to drive back and forth looking for a paper map in the middle of the night.”
When York County decided to build a countywide GIS a few years ago, public works and engineering both agreed to participate. Although the county water/wastewater system is relatively small — serving about 6,000 people — the two departments were having trouble keeping up with the pace of development that had spilled across the North Carolina border from nearby Charlotte. The departments agreed to work together to map the water and sanitary sewer networks. “By accurately mapping the utility infrastructure, [county officials] could make better decisions about how to plan for and accommodate future development,” Townsend says.
York County began by mapping the fresh water distribution network using handheld mobile GIS devices. In 2005, public works crews began collecting data on any exposed manhole covers, sewer grates or sanitary pipes that they saw during their daily activities. When the features are loaded into the GIS, technicians reference hardcopy maps and computer-aided design (CAD) drawings to fill in the details of pipe sizes, flow direction and underground line locations.
Converting from paper to digital
In creating its first water/wastewater GIS, Sioux City has applied similar techniques. City officials fear losing valuable infrastructure details stored only on paper or in the heads of its utility staffers, some of who will retire in the next decade. The city began converting paper maps and schematics into digital versions in 2002, and mobile GIS is being used to check the accuracy of the conversions. “GIS is the only way to preserve the files that were deteriorating, and mobile GIS is the only way to keep them updated,” says Ron Simmons, Sioux City Utilities project coordinator.
In 2006, the city upgraded from backpack-mounted GPS receivers with separate data collection units to integrated hand-held devices. The pace and the accuracy of fieldwork improved as a result. “The hand-held units are much smaller and easier to use, and they hold a lot more [GIS] data that can be checked and updated in the field,” Simmons says. City staff now can map sanitary lines and water features while they are onsite for other reasons, such as to repair or install new pipes.
To assist with the mapping, Sioux City contracted with Lincoln, Neb.-based GIS Workshop to scan existing schematics, digitize features from orthophotographs, convert data from CAD files, and update files using mobile GIS. Project participants have mapped 2,000 features since late 2005 with eight- to 12-inch accuracy.
As the location information is loaded into the GIS, technicians use the coordinates to correct the locations of the sewer lines that were digitized from paper maps or converted from CAD drawings into GIS layers. Working in the GIS, the technicians align the sewer pipes with the manhole covers and will document all 320 miles of sanitary lines to an accuracy of about one foot.
Once the water and wastewater networks have been mapped in their entirety, which should be accomplished this year, Simmons expects the mobile GIS devices will stay in the field with various city crews. Sioux City plans to keep its GIS current by using the devices to record whenever a valve is replaced or a new pipe is installed. The city’s GIS group also has developed an intranet-accessible system that allows key offices — especially engineering, public works and inspections — to view and update the same pipeline network maps.
Updating existing GIS data
The building boom in Atlantic City, N.J., compelled nearby Hamilton Township Municipal Utilities Authority (HTMUA) to upgrade its GIS in 2004. The existing system was sufficient for basic mapping functions but could not handle hydraulic modeling and other applications the HTMUA needs to help plan for increasing growth. The utility contracted with the local office of San Bernardino, Calif.-based Nobel Systems to overhaul its GIS.
The contractor created a data model for a geodatabase that defines the assets and their connectivity. In addition, it collected new feature and attribute information for assets that were installed since the original digital map was created. Similar files were developed for the county sewer facilities located within the HTMUA service area and for a small public water and sewer system adjacent to it. Fortunately, the utility had as-built drawings, county parcel maps and recent aerial photos from which data could be extracted, but the contractor also spot checked the information using mobile GIS units, and technicians recorded additional field information on the mobile device when applicable. Back at the office, the data was edited before it was added to the geodatabase. Features mapped with the mobile GIS device scored an average accuracy of 10 to 14 inches.
Nearly all of the township’s 60 miles of sewer lines and related assets have been mapped now, and HTMUA is ready to move ahead with the hydraulic modeling of the water and sewer systems for use in planning future capital projects. “Most of the developers who build new subdivisions are using AutoCAD to create digital as-builts of the water and sewer lines they install,” says Steve Blankenship, HTMUA executive director. “With the new geodatabase, Nobel is helping us devise standardized data layers so that feature and attribute information can be migrated directly from the digital as-built files into our GIS based asset management system.”
Ready for the future
Utility representatives agree that highly accurate maps of water and wastewater networks are crucial for locating buried pipelines when repairs are needed or crews are excavating land. And, as pipelines are extended to accommodate growth, utility crews need accurate horizontal and vertical location data so they can precisely plan extensions and make sure everything keeps flowing downhill.
Kevin Corbley is the principal of Corbley Communications based in Winchester, Va.
