GIS Tech News (#51)

4 Feb, 2008

Collaboration Yields Cleaner Water p>

With the help of GIS tools, the city of Denver is keeping urban contamination out of rivers and streams.

By Andrew Roe

Groundbreaking collaboration between engineers and GIS professionals is helping the city of Denver clean up key waterways at a faster pace than anticipated. By using GIS tools to identify where sanitary sewer pipes intersect storm drainage systems, the city has undertaken aggressive efforts to prevent untreated sewage from reaching streams and rivers.

The major impetus to the effort began in 2004 when the mayor's office directed several city departments to improve water quality in the South Platte River, which drains in a northerly direction along the entire length of the city. In addition to collecting urban stormwater runoff and other pollutants associated with developed urban environments, the river and its tributaries convey traces of unwanted bacteria from sewage that apparently migrates from sanitary sewers into storm sewers and ultimately into the river. The challenge: identifying potential cross-contamination points in the city's 1,500 miles of sanitary sewers and 550 miles of storm sewers.

Tapping into Data Sources
As the city's Department of Public Works began evaluating how to pinpoint the potential pipe conflicts, they contacted the DenverGIS group in the city's Technology Services Department to explore a database solution. The city had scanned and manually entered data from hundreds of sewer maps and other sources in the 1990s and built a sewer geodatabase with more than one million features. The data included x, y, z coordinates at key nodes in the sanitary and storm sewer systems. Hydraulic models of the systems had also been built as part of master planning efforts.

The DenverGIS group produced a draft map showing potential conflicts within a day and a list of more than 5,000 intersection points within 45 days, according to Darren Mollendor, project engineer with the Wastewater Operation Section of the Department of Public Works. "It would have taken four full-time employees nine months to do this manually," he said.

Because the city had built such a comprehensive database of its sanitary and storm sewer systems, the task presented a good opportunity for the city to apply its ESRI ArcGIS-based resources. "It fit to a 'T' what you can do with GIS," said Paul Tessar, GIS data administrator of DenverGIS. "Often, in the life cycles of GIS projects, you spend years building a database and only use it for mapping and simple analysis. When presented with the opportunity to develop such an exciting analytical model, who wouldn't jump at the chance?"

With assistance from a local consultant, Matrix Design Group, the DenverGIS group developed a two-stage methodology to identify conflict points. First, geoprocessing algorithms were developed and applied to identify sanitary sewers crossing above, through, and below storm sewers. Next, postprocessing queries helped eliminate duplicate data points and prioritize data. ArcMap was used to convert data points into event classes. Read more »

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Cadalyst contributing editor Andrew G. Roe is a licensed civil engineer and president of AGR Associates. He is also the author of Using Visual Basic with AutoCAD, published by Autodesk Press. E-mail him at


CAD Clinic: Civil 3D Tutorial

More on Civil 3D Labels

By Phillip Zimmerman

A few months ago, I began to define a Pin and Parcel Area label. The initial steps of defining a label occur in the Label Style Composer dialog box. This dialog box contains the Information, General, Layout, Dragged State, and Summary tabs. I also looked at the Layout tab and described its settings in detail. In September's column, I reviewed a label's dragged state settings and the Parcel's display order for line work. This month's "CAD Clinic: Civil 3D" installment concentrates on exploring label styles, labeling multiple occurrences, and discussing pipe network structure labels and label sets.

Pipe Network Text for Each
A Pipe Network Structure label has a special Layout component type called Text for Each. Text For Each creates a label entry for each structure's incoming and outgoing network pipe. The label's component name identifies the label's text contents as incoming and outgoing pipes. Read more »


Mark Your Calendar: GIS Events

GIS Manager's Workshop

February 25, 2008
Kissimmee, Florida
Geographic Technologies Group (GTG) will sponsor the GIS Manager's Workshop for all GIS managers and IT directors. Topics will cover Managing GIS, The Governance of GIS, The Enterprise Implementation of GIS, and The Business Case for GIS. This workshop is also scheduled for other cities in March. Read more »

AWRA GIS Conference
March 17-19, 2008
San Mateo, California
Among the offerings at the American Water Resources Association's GIS Specialty Conference will be a field trip, workshops, and presentations covering a broad range of subjects on integrative geospatial hydrologic technologies. Water resource and geospatial specialists, managers, scientists, practitioners, programmers, hydrologists, engineers, and ecologists, among others, should attend. Read more »

Cadalyst's complete list of upcoming events is always available on our Web site. Cadalyst's sister publication, Geospatial Solutions, also offers a full calendar of GIS-related events.