Water Main Shutdown Application Prevents Costly Mistakes
The main GUI of Main Break is a standard ArcView 8.1 ArcMap interface with a customized toolbar that provides additional functionality such as tracing, valve toggling, and report generation. Most analysis and tracing activity takes place in the main ArcMap window so the application is simple for field crews to use. The customized functionality supplied by Main Break is briefly described in the following section.
SJWC uses the shutdown trace function to determine which valves in the network need to be shut down to isolate one or more water mains or services from the network. This function is performed by placing flags on one or more edge features of the water network that will be removed and executing the trace. After the trace is performed, the valves that need to be shut down are highlighted. Other mains, services, and hydrant pipes that would be affected are also highlighted. Note that the entire main or service is also highlighted because SJWC's network is not split at valves. Consequently, pipe to the outside of a closed valve will still have water flowing through it so the services and other features past the shutdown valve will not be affected by the shutdown.
Disconnected Feature Trace
A disconnected feature trace is the opposite of a shutdown trace. SJWC uses the disconnected feature trace to determine which features of the network are disconnected when specific valves are closed. A disconnected feature trace is performed by toggling one or more valves of the water network open or closed and executing the trace. All features that would be disconnected from the water network are highlighted.
Flag Critical Features
Critical features are specific services or water system features that are important to identify when shutting down water mains. SJWC has three types of critical featurescritical services, critical valves, and critical system features.
Critical services are customers, such as hospitals or schools, that need temporary service installed when the water main that serves them is shut down.
Critical valves control large portions of the water network. Main Break displays each of these services with a different feature color when a trace is performed and designated as critical in the Service List report. These services can be flagged and comments about these services added. Flags can also be removed and comments deleted.
Critical system features are water system features (e.g., supply lines) that should not be indiscriminately shut down. If a critical feature is shut down during tracing, a warning message will appear telling field crews that a crucial system feature has been shut down and the feature will be displayed with a unique color on the screen.
Users can directly designate critical valves and features by selecting them interactively, or by address or assessor's parcel number (APN). Assigned critical feature information is written to the associated feature in the geodatabase and is available for ArcView selection queries and reports.
Using Main Break, SJWC staff can track a history of leaks within the network. Coordinates on the menu are extracted from the position of the flag and all attributes are extracted from a flagged feature. Leak data is stored in a separate dedicated database.
Prior to implementing Main Break, SJWC asked Weston to test an actual scenario that had occurred at the utility when crews had mistakenly shut down a large internal area of the water network. SJWC wanted to see if the application could predict what would happen. Main Break successfully identified the portion of the network that was mistakenly shut down previously by SJWC crews. This section of the water network was difficult to visually analyze using paper maps because the area extends across multiple map pages.
Using an automated system such as Main Break to portray shutdown scenarios prior to effecting a shutdown can help reduce errors and allow crews to more confidently perform maintenance activities. For more information on GIS and water utilities, please contact
Jennifer Coate, Project Manager
Weston Solutions, Inc.