The Springfield Water and Sewer Commission in Springfield, Mass. hastaken a proactive approach to managing its aging wastewater collectionsystem. As part of the development of a Long Term Control Plan (LTCP)for Combined Sewer Overflows (CSOs), the agency is rebuilding itsGeographic Information Systems (GIS) to facilitate the operation andmaintenance of its assets.
The goal of the overall asset management program is to proactively manage the Commission?s aging infrastructure, while balancing its obligations related to CSO control and other Clean Water Act obligations. A critical part of the rebuilt GIS is the use of advanced functionality to improve the accuracy of sewer mapping and recordkeeping that shapes the foundation of the agency?s new asset management and maintenance initiative.
Inventory Connectivity
Springfield?s sewer collection system consists of approximately 460 miles of sanitary, combined and interceptor sewers ranging in diameter from 6 in. to 108 in.; 12,000 manholes; and 30 sewer and flood control pumping stations. The Springfield utility network includes more than 50,000 asset features and crews perform more than 10,000 asset inspection observations annually.
In an effort to proactively address failures in the system?s aging infrastructure and respond to EPA regulations and Clean Water Act obligations, the commission contracted Kleinfelder and MWH Americas, Inc. to develop its LTCP. In addition to the benefits to the LTCP development, a comprehensive and detailed asset management program that uses GIS as a data management resource will provide a solid foundation for maintenance. After an assessment of Springfield?s existing collection system and business processes, the project team identified GIS and asset management as critical tools in the development of the LTCP.
Springfield?s GIS (ArcGIS from Esri) is currently used as an asset inventory and mapping tool. However, the GIS inventory had some connectivity and flow direction inconsistencies. In addition, the more than 27,000 catalogued paper record plans, and more 30,000 catalogued service tie cards, were only searchable via a text search. Springfield also had a large volume of defect and service locations from historical CCTV operations available.
As part of the LTCP development, the project team set out to update the existing GIS asset foundation to reflect current conditions, such as new construction or system upgrades, develop an electronic library of records and tie-cards that could be searched using the map interface and leverage the pipeline assessment data for more than just targeted repairs and maintenance. Once the updated asset inventory is added to the GIS, the possibilities for system analysis are virtually limitless.
Spatial Connections
For utilities, one of most valuable tools in the ArcGIS toolset is the ability to create geometric networks. Geometric networks are a way to model distribution systems such as sanitary collection system networks and then create what-if scenarios and maintenance plans based on realistic system operations.
In this case, the Springfield geodatabase includes spatially-connected points, lines and polygons that depict the sanitary collection system network. A geometric network represents how the sanitary collection system actually operates. Key assets in the collection system include gravity mains, force mains, inline junctions, manholes, laterals, siphons and pump stations.?
The classes in the feature dataset are used as the data sources for geometric network elements, called junctions and edges. Junctions might be manholes or inline junctions while edges are sewer mains and siphons. Edges and junctions in a network are topologically connected to each other ? edges must connect to other edges at junctions. Once the edges and junctions are established, the GIS data manager can establish rules that define how resources flow through the geometric network. Using the geometric network tools, the team verified the accuracy of the existing GIS and developed sewer catchment areas for the entire network.
Once set up, geometric networks provide system analysts with a powerful tool to visualize network responses to common scenarios including upstream and downstream isolation tracing. With the tracing tools, system engineers can see the entire upstream network and understand what pipes collect sewer service flows and runoff from which areas, which is critical in understanding the hydraulics of the entire system.
Geometric networking can also be used for planning for emergency management scenarios. For instance, a tracing analysis of the geometric network was recently used to determine the number of customers that could potentially be affected by a power outage at a pump station. The subsequent results helped the commission prioritize emergency generator backup improvements within the existing pump station infrastructure.?
Another example of how geometric networking can be used is to track the flow path and travel time of a slug of hazardous materials that may have entered into the sewer system so that maintenance crews can intercept the material before it reaches the treatment facility.
With more accurate and advanced asset data, the commission now has a more accurate hydraulic model which was used to refine the LTCP so that it was structured to be the most beneficial for long term hydraulic improvements to the system. A second task in the asset management system was to develop an electronic library of the more than 27,000 paper record and 30,000 service tie-cards that could be searched using the GIS interface.?
Instant access to record documents via the GIS mapping interface will streamline Springfield?s daily research and dig-safe activities. Further, the digital library can be used to track the historical progression of the infrastructure at a single location.
Establishing Trends and Priorities
A third and invaluable tool for Springfield asset managers is the ArcGIS linear referencing tool, which allows users to store geographic locations by using relative positions along a measured linear feature, such as a pipe. As part of the GIS update, Kleinfelder and MWH Americas used linear referencing to leverage the data that was collected during CCTV activities on the location and severity of defects as well as location of service taps along a pipe.
Springfield?s CCTV work includes the capture of data, photos and videos along 460 miles of sewer pipes within the entire system in a five-year period. The GIS team will in turn update the risk model with the structural and operations and maintenance conditions of the infrastructure and re-prioritize the capital improvement plan based on the new information.
Using the linear referencing functionality, the GIS analysts are able to visualize the tabular inspection observations data and clearly see points and discontinuities along each assessed pipe segment. The linear referenced data is used for quickly analyzing defect trends, establishing priority areas and preparing rehabilitation work orders.
For example, in database format, it may be difficult to see that an entire neighborhood is having issues with a similar type of defect (i.e. grease buildup within the pipe). With the mapping interface, Springfield will be able to identify the issue trends and then prioritize improvements or ongoing maintenance activities in specified areas.?
Linear referencing can also serve as a tool to link the defect images directly to the location that they are occurring along the pipe, and can be made available via a web-based interface.
Progress To-Date
Thus far, Springfield is in the third year of the five-year program to develop its asset management program. The Kleinfelder/MWH Americas team has mapped and collected appropriate asset data ? such as size, material and age of pipes ? and performed condition assessments on about 50 percent of Springfield?s pipes, manholes, pumps stations and the wastewater treatment facility assets. They have linked more than 25,000 record documents to the correct assets and built a risk model that evaluates relative risk of all assets in the collection system based on probability and consequence of failure.
Perhaps most importantly, the team has developed a comprehensive Risk Model tool that has been used to prioritize the overall Capital Improvement Plan. The Risk Model combines CCTV condition data and the GIS to determine the probabilities of failure as related to the structural condition, operations and maintenance conditions and the consequences of failure.
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Within the tool, the risk of failure is determined by the probability of a failure times the consequence of that failure. Each asset?s consequence of failure is scored for a variety of consequences including environmental impact, high cost of repair, public health and safety and public relations. An example of an environmental impact might be the asset?s proximity to a wetland, river or sensitive environment. The high cost of repair could be the location of pipes under railroads, buildings or rivers, which are far more difficult to repair or replace than those in the street. Public health and safety is a concern particularly when assets are located within proximity to schools, daycares, retirement facilities and hospitals.?
The risk score allows Springfield to compare risk across various types of assets (pipes, manholes, pump stations, portions of the treatment facility, etc.) and build logical capital projects. The overall project risk is then used along with a benefits analysis to prioritize the Capital Improvement projects and develop a plan that addresses capital, operation and maintenance, and continued diagnostics of Springfield?s collection system.
Thomas J. Ritchie III, is a senior project manager at Kleinfelder, and a senior project manager and program director for the Springfield Water and Sewer Commission?s CSO and Collection System Improvements Program.
Jason Lavoie is a senior engineer with Kleinfelder and is the program engineer for the Springfield Water and Sewer Commission?s CSO and Collection System Improvements Program.
Berkley Myers is a senior GIS analyst at Kleinfelder.?
