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System uses go beyond stormwater to include water and sanitary sewer. By Mark Kollitz, Sean Martin, and John Hannel
Maps have historic significance for the City of St. Charles, MO. This city on the banks of the Missouri River was the 1804 launching point for the Lewis and Clark expedition and mapping of the American West and Northwest. In 2004, that moment in history celebrated its bicentennial. The city’s Public Works Department is having its own celebration of sorts: the recent launch of a geographic information system (GIS) of the city’s water, sanitary sewer, and stormwater systems. More than just a pretty map, GIS is helping the city meet National Pollutant Discharge Elimination System (NPDES) Phase II requirements. Indeed, NPDES jump-started St. Charles’s quest to inventory stormwater infrastructure and build GIS. City leaders decided it would be cost-effective to do the same simultaneously for the water and sanitary sewer systems. As a result, the city’s GIS uses go beyond NPDES requirements and into the realm of better infrastructure management, modeling, and planning for all three utility systems. To build the water-sewer-storm GIS, project activities included:
Approximately 20,000 structures were inventoried among the water, sewer, and stormwater systems. The city now has an accurate record of not only where structures are located, but also sizes of structures, top and flow-line elevations, and other data. Eventually, the city will connect the data to a computerized maintenance management system. Here’s how GIS was built. Getting Started The City of St. Charles—on the edge of metropolitan St. Louis but really a city unto itself—has seen tremendous growth in recent years. Today, the population is more than 62,000 over a land area of 26.5 square miles. The city is drained by two main creeks, Sandfort Creek and Cole Creek, which convey stormwater generally north to the Mississippi River, and three unnamed tributaries that convey stormwater generally east to the Missouri River. The terrain ranges from hilly in some areas to bottom lands that are prone to flooding: Many will remember the Great Flood of 1993, when the Mississippi and Missouri rivers surged to levels not seen in more than 150 years. With population growth and development, the city has faced the challenge of maintaining records for its water-sewer-storm infrastructure. The city had limited mapping of these systems, some of which were decades old. The City of St. Charles selected Woolpert LLP, a civil engineering firm with headquarters in Dayton, OH, and an office in St. Louis, to assist with bringing the city’s water, sewer, and stormwater maps into the twenty-first century. The project started in January 2003 with Woolpert recommending the HM project, which would use GPS surveying system technology to capture both horizontal and vertical controls. The city was the first in Missouri to use GPS to develop the vertical component of monuments using National Geodetic Survey HM specifications. The project provided the city with a geodetic control network—something the city did not have—in half the time of conventional leveling. The method saved the city between $50,000 and $75,000 over conventional leveling. St. Charles now has consistent control citywide. The data are available for public and governmental use. In addition, the city now requires any new development be tied to the control network to allow for easier inclusion in GIS. Next, Woolpert took black-and-white aerial photos in February 2003 and March 2003 to take advantage of optimum visibility. The resulting orthophotos serve as coverages (a backdrop) for GIS, enabling better addressing of properties, and also provide a better overall picture of the city in terms of developed and undeveloped areas, which aids in designing and planning. An additional aerial survey was performed using LiDAR to collect the vertical component of water and stormwater structures at an accuracy level of plus or minus 6 inches. Using the LiDAR data, Woolpert later populated the GIS’s water and stormwater point data with the z-elevation (vertical) attribution. The LiDAR data in GIS enabled creation of planimetric maps consisting of hydrology features with direction of flow. From these maps, digital terrain models (DTMs) can be created for hydraulic and hydrologic modeling. Finally, before field data collection, Woolpert scanned source material and city-supplied land-base files—including subdivision maps, vintage maps (maps from the original section of town, circa 1800s), street maps, and existing water-sewer-storm system maps—to digitize the utility systems’ known structures. The converted data were delivered to the survey team in shapefiles and then imported into SmartSurveyor, a mobile mapping system that enables GPS crews to map water-sewer-storm systems and apply attributes in the field in a single sweep. These data gave surveyors a starting point as they began to locate structures. Conducting the Field Survey and Building the GIS
Field data collection began with a 0.5-square-mile pilot area in March 2003 before going citywide in April 2003 to 26.5 square miles. Woolpert surveyed the city’s infrastructure using the SmartSurveyor software on rugged pen-based field computers integrated with Trimble’s real-time kinematic (RTK) and real-time differential (RTD) GPS technology. RTD was chosen for the water and stormwater systems because it would provide the x and y coordinates at meter-level accuracy, which was accurate enough for the city’s purposes and more cost-effective than the sub-meter-level accuracy of RTK. Additionally, the vertical component for water and stormwater had been obtained via the earlier LiDAR mission. However, Woolpert used RTK for sanitary structures, obtaining x, y, and z coordinates at centimeter-level accuracy to achieve highly accurate data. The city intends to use the sanitary system data for an ongoing wastewater study, which will involve hydraulic modeling.
The city determined what attributes to populate in GIS based on budget. For the full conversion project, the features that were converted included: Water System Hydrant attributes were collected in the field, including x and y coordinates, inventory status (found/not found), condition comments, rotation (valve open/close direction), age, and manufacturer. The paper source of hydrants (where original information came from, whether map or as-built) was input in the office. Water main features were not field collected; all attribute information originated from paper source documents, including diameter, material, type, source, condition comments, and rotation. Water fittings’ location and attribute information came from paper source documents. Sanitary Sewer
System Stormwater System Quality Assurance and Quality Control Once data were collected, Woolpert’s GIS analysts performed a combination of manual (visual) and programmatic reviews of the field structure locations, attribution, and system connectivity. The field structure reviews were performed by comparing the structure placement against the newly flown orthophotos and digital structure data placed before field collection to help evaluate whether GPS or digitized (manually placed) field locations were within the permitted tolerance ranges, and also to confirm that no structures had been missed or could not be found in the field. When GIS staff had completed their reviews, reports were forwarded to the applicable field manager. The field managers took GIS-reviewed reports and would
At this stage, field managers also queried the data for connectivity and condition-assessment issues indicated by field crews and worked to resolve these problems. Once the field manager was satisfied with the results of the automated review, the orthophoto review, and connectivity and condition-assessment reviews, the revised data was re-forwarded to the GIS staff. At this point, GIS took “ownership” of the dataset. Any digital revisions to the database were done strictly by GIS staff and required the authorization of the field manager or city project manager. GIS staff would run additional quality-assurance and quality-control checks, including but not limited to:
Putting GIS to Work GIS is being used to meet NPDES Phase II requirements, for better records and infrastructure management, to comply with new state requirements, for Federal Emergency Management Agency (FEMA) purposes, and to streamline a variety of tasks as described below.
Meeting Applicable
Control Measures Set Forth by the NPDES Phase II Mandate Additionally, GIS is being used as a tool in reviewing development plans, including stormwater collection and detention/retention systems. It is also used to map locations of stormwater complaints and sanitary backups. Analyzing the geographic locations aids in identifying capacity or maintenance issues with the collection system. In the future, GIS will be used to create a computer model of the stormwater-collection system to evaluate impacts of proposed developments and identify capacity issues/problems. It will also be used to track the permitting and maintenance of stormwater detention/retention facilities. Enabling Better
Infrastructure and Records Management Enabling Utility-Locate
Services Providing Data
for FEMA’s Use Providing Evidence
in Property Condemnation Cases Developing a Sanitary
Collection System Model Inventorying the
Condition of Public Streets Conclusion NPDES Phase II may have
jump-started the City of St. Charles’ GIS, but its uses go
beyond the mandate’s requirements to meet a variety of needs
across the city’s water-sewer-storm systems. From better records
management and utility maintenance to modeling and planning efforts,
the citizens of St. Charles will be better served by this highly
sophisticated map. SW November/December 2004
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