- SPECIAL REPORTS
- THE MAGAZINE
Finding the software needle in the GIS haystackNew land development leads to the need for new databases on many utility fronts. Such was the case with Boxelder Sanitation District in Fort Collins, Colo. When it experienced a substantial increase in population over five years, from 6,000 to 11,000 today, it needed a more advanced way to keep track of the elements in the district’s sewer collection system—a compilation of gravity sewer lines, manholes and pipe in the ground with slopes for sewage to flow.
With the great advances in information technology and the difficulty of managing so much infrastructure with paper records, we at Boxelder thought that a digital system would be much more useful. We found it would be great to have a system that could link our point and line data to a map.
We worked with utility plans for new subdivisions but found they were not accurate; they were as-planned not as-built. We needed to locate sewer lines within three feet horizontally and a few hundredths of a foot vertically. The vertical data on a sewer is critical. For solids to flow to the plant, there has to be a minimum of fall in the pipe. If we know the pipe is improperly installed we can change our management plan accordingly.
Having an inaccurate and incomplete map, we setout to create a Geographic Information System (GIS) of our old and new wastewater collection system. After trying traditional surveying methods to map our system, and finding it very slow, we purchased a Trimble Pro XR GPS receiver and a TSC1 data collector (Trimble, Sunnyvale, Calif.). This enabled us to locate all our manholes much faster. Also after post-processing the GPS points, we found we could achieve a positional accuracy of one foot. We wanted to achieve better than five foot accuracy, as it will be easier to find manholes in the future.
After mapping the manholes, workers needed to draw in the sewer lines. This is where we encountered difficulties. Our GIS software would not snap lines between each manhole and develop a line layer. At this point we realized that a more advanced application was needed. The district contracted with Advanced Professional Engineering (APE) of Fort Collins, Colo., to help build our collection system GIS.
APE staff met primarily with me regarding technical aspects and a couple of other district personnel to collate the existing GIS data and recognize all our short- and long-term goals. They looked over our data sources such as GPS manhole points, MapInfo GIS, Excel spreadsheet data, AutoCAD drawings and Shape files, and the software we were using: ArcView, AutoCAD and AutoCAD Map. APE then came up with an exclusive prescription to satisfy district needs. They did a pilot project on a small area of the collection system using this application. After creating and documenting the system they showed district staff how to do the same.
The SolutionThey suggested that we use UMS2000, an application they developed to run in AutoCAD Map to create the linework. After on-screen digitizing the sewer lines, they showed us how to attach attribute data to the lines from Microsoft Access or Excel. Using ArcView, Advanced Professional Engineering’s instructions allowed us to link our manholes and sewer lines to any external database needed to monitor our collection system. The process was essentially seamless, but when I ran into any snags or concerns, I called on Mohamed Worayeth and Hashem Faidi at APE. They usually had an answer as to what the problem was. It turned out to be pretty simple.
This was all done for less than half the cost of other GIS software we looked into, yet we retained the flexibility and power of a database. Having all this information in a database will allow us to link to our customer billing data to the monthly flows for each service. From this we will estimate the flow for each pipe run and collector on down the line. Then we will use this information to monitor infiltration into the sewer system. This will aid in finding the most cost-effective way to reduce this problem.
We also intend to use this system to monitor the cleaning and maintenance of lines and manholes. This will enable us to schedule sewer line cleaning and monitor problem areas with much greater efficiency.
Having an information system that links a database to an accurate map of our collection system is a very useful tool to our district. It will help us manage every aspect of our collection system’s condition and location.