From In the Field to In the Office: Northern Kentucky Puts Stormwater Structures at Users Fingertips
The district contracted with the Covington, KY, project office of Woolpert LLP, a Dayton, OH-based civil engineering firm, to perform an inventory and condition assessment of the region’s open and closed stormwater drainage systems. After the data were collected, they would be loaded into a geographic information system (GIS). The GIS would contain information to do the following:Assist in developing a Stormwater Management Plan (SWMP) for the district’s National Pollutant Discharge Elimination System (NPDES)/Kentucky Pollutant Discharge Elimination System (KPDES) Phase II permitHelp the district know the extent and condition of the stormwater drainage system in northern Kentucky as the district assumed management responsibilitiesHelp the district with future operations and maintenance and master planningIn all, 63,000 features and 2,600 mi. of open channels were surveyed between 1999 and 2003. Today, Sanitation District No. 1 has a continuous stormwater drainage system in an ArcInfo Workstation GIS. The database includes the attribution information collected in the field at each structure. The GIS is being linked to a computerized maintenance management system (CMMS). Here’s how this huge inventory and condition assessment project happened – on budget and on schedule.Growing Area Goes for RegionalizationUnderstanding northern Kentucky’s need for such information begins with understanding how the region – and Sanitation District No. 1 – evolved over the years. Northern Kentucky’s Boone, Campbell, and Kenton Counties are just across the river from Cincinnati, OH. As Cincinnati has grown, so too has northern Kentucky – in part because of Cincinnati but also in its own right. Boone County is home to Cincinnati/Northern Kentucky International Airport. The county is bisected by Interstate 75, a major transportation artery that runs from the top of Michigan to the southernmost tip of Florida. All three counties are bisected by Interstate 275. For many years, the sanitation district had served northern Kentucky solely as operator of the region’s wastewater treatment plant and pumping stations. Then around 1994 the State of Kentucky created legislation that allowed the district to assume responsibilities for operating the wastewater collection systems for the communities. Today, the sanitation district owns, operates, and maintains more than 1,200 mi. of combined and separated sewers, one major wastewater treatment plant, nine small treatment plants, 135 pumping stations, and 15 flood-pump stations. As the district assumed responsibility for sewage collection, it also brought sanitary-sewer GIS efforts “in-house,” building on a GIS that had been initiated by the Northern Kentucky Area Planning Commission (NKAPC). Officials from Boone, Campbell, and Kenton Counties determined that they needed a regional SWMP, and because regionalization of sanitary-sewer services had proved a success, they determined that the district would be the best entity to handle such a program. A regional SWMP would benefit the area as follows:By providing equitable, cost-effective management of stormwater problems spread among the 34 communitiesBy helping enhance water quality in local streamsBy helping ensure NPDES/KPDES complianceThus, in 1998, the State of Kentucky created legislation that allowed the district to assume from the communities responsibility for all stormwater systems and activities over the next several years. Base mapping of each community’s stormwater system, however, was even more limited than what had been available for each sanitary-sewer system. A few of the communities’ public works departments had paper maps. Some smoke and dye testing data and limited stormwater attribution information existed in a layer of the district’s sanitary-/combined-sewer GIS. In 1999, the district, NKAPC, and the Boone County Planning Commission (BCPC) used aerial photography to create planimetric, topographic, and digital orthophoto base-mapping datasets; this information was used to generate ArcInfo coverages of the stormwater drainage system. These photos and datasets became outdated, however, as the inventory project progressed, and in areas covered by trees or heavy brush, the aerial photos provided little support. As a result, project staff had to have a solid understanding of stormwater systems.Basically the district had to start from scratch to obtain the location, attribution, connectivity, and condition information on many features:ManholesInlets and catch basinsPipes (12 in. or greater in diameter)Pipe inletsPipe outletsCulvertsRetention/detention pondsDitches and open channelsThe district again contracted with Woolpert to survey the region’s stormwater channels and structures and from this information create a comprehensive GIS.Determining Necessary Information, Establishing ProtocolsWoolpert started the process by meeting with district personnel – specifically engineering, maintenance, and field crews – to learn what kinds of attribution information would be used on a regular basis and needed for future uses. The project team discussed how attribution information would aid in preventive maintenance, modeling, a CMMS, illicit discharge determination and elimination, and asset transfer and management. Only truly necessary attribution would be included in the inventory project.Ultimately district staff determined that the following stormwater attributes needed to be collected:Location (horizontal coordinates at meter-level accuracy)ConnectivityMaterialDepth (e.g., pipe inverts, structures)Size (e.g., pipes, culverts)Flow characterization (turbidity)Digital photographs In addition, the condition of structures would be assessed for debris and cleaning and for rehabilitation and repair. Woolpert and the district worked to develop the initial field procedures for collecting objective attribution (i.e., pipe size, depth, and material) and subjective attribution (i.e., physical structure conditions and flow characterization). The inventory of the stormwater drainage system would be conducted using a ruggedized, pen-based field computer system with the real-time differential (RTD) global positioning system (GPS) survey method. RTD was chosen instead of real-time kinematic (RTK) GPS because RTD would provide the x and y (horizontal) coordinates at meter-level accuracy, which was precise enough for the district’s purposes and more cost-effective than the x, y, and z (vertical) sub-meter-level accuracy of RTK. The region’s hilly topology had a hand in this decision: Because of the slope in the area, adequate flow is not a problem, and therefore the district did not plan to do high-end hydraulic modeling, which would have required sub-meter-level accuracy. It was decided that top-of-structure elevations would be derived through an interpolation process using an existing digital terrain model provided by NKAPC and BCPC. Next came the logistics of surveying such a huge land area. Woolpert recommended breaking the 245-mi.2 service area into manageable basins initially based on United States Geological Survey 14-digit Hydrologic Unit Code (HUC) watersheds; these areas were further broken into sub-basins. As crews got into the process, they sometimes found a storm sewer flowing into another watershed, so sub-basins were modified as needed to reflect drainage patterns of the field. In all, 256 urban and rural sub-basins, each approximately 1 mi.2 in size, would be surveyed. Each sub-basin was assigned a field manager; two field staff members, who comprised a crew; and a GIS analyst. If any problems arose and the sub-basin needed to be revisited – whether in person or “virtually” via the GIS – the original personnel assigned to the sub-basin would handle the problem. This method made the entire project flow smoothly, from personnel management to data collection and processing to deliverables.Additionally, separate protocols for surveying sub-basins in urban and rural areas were established:For urban areas,crews would walk the entire open-channel system (including tributaries) until it intersected with a closed storm system or transitioned from overland flow in the upstream regions. Crews then would inventory the closed system.For rural areas, field managers and crews would first examine aerial photography to get a visual on whether stormwater structures even existed in the sub-basin and then choose which areas to walk. But, in some cases, entire subdivisions in rural areas (and urban ones) were not on the aerial photography because it had been flown in 1999 and new developments had been built since then. So crews also would drive the public roads of some rural areas for evidence of stormwater structures. Road culverts and open channels within the road right of way would be inventoried, as would closed sewer systems that existed within the road right of way, which could be seen from the road. If a closed system crossed the road right of way but was not contained completely within it, field staff would track and collect attribution data until the termination points of the system in each direction were reached. Fieldwork BeginsWoolpert began with a 6.1-mi.2 pilot area in Boone and Kenton Counties in 1999, which helped determine the appropriate methods and level of accuracy necessary for development of the districtwide stormwater GIS. Actual surveying began in 2000, with crews starting in Kenton County (the central county) and working west toward Boone County and east toward Campbell County.Two-person survey crews would start at the low end of each sub-basin and work their way up. As they came across channels and structures, they would “GPS” the locations and collect the applicable connectivity, attribution, and condition assessment information on pen-based computers loaded with Woolpert’s SmartSurveyor software (see sidebar). Each structure would receive a unique ID number based on the HUC basin, the sub-basin, and a feature identifier.In addition to surveying channels and structures, if crews saw something of interest, they would note it on their field computer. For example, crews noted illegal dumping in and along creeks, septic systems discharging into stormwater channels, broken laterals, and broken sanitary-sewer pipes. Basically anything that impacted stormwater quality was noted in preparation for NPDES/KPDES Phase II permitting requirements. Also, applicable communities’ public works departments were notified of any deficiencies found in their systems because transfer of responsibilities to the district still was to occur.If a public health or safety problem was found, such as sewage in catch basins and open channels or a missing manhole cover, crews immediately reported the problem to district dispatch. If it was a sanitary-sewer problem, the district would send personnel; if the problem was related to stormwater, because the district had yet to assume management responsibilities, it would notify the applicable community, which would respond with personnel. Woolpert crews did not leave the site until community or district personnel arrived. During the inventory and condition assessment portion of the project, crews encountered a number of challenges:Lack of access to buried structures. Crews used a probing rod or a metal detector to verify a buried structure’s existence and used a TV camera if an internal view of a pipe was needed. On occasion, crews exposed structures, but for the most part the ground was left undisturbed. Working in SmartSurveyor, crews coded the structure to note that it was buried. This notation also appeared in the GIS. Blocked GPS signals. For structures located in heavily wooded areas or urbanized areas where the GPS signal was blocked, rendering the RTD GPS inaccurate, locations were made by digitizing the obscured structure into the pen-based field computer using the NKAPC and BCPC planimetric mapping as a reference.City of Florence, KY. The City of Florence has its own stormwater system and program and, as such, was not a part of the district’s stormwater project. Portions of Florence’s stormwater system, however, flow into the district’s system, and vice versa. Crews worked around the city (which is located in Boone County near the Kenton County border) to obtain survey information and then, in SmartSurveyor, used inferred lines or segments to create map connectivity. Inferred lines were noted as such and coded in a separate color in the GIS. The result is a seamless and continuous system.Cincinnati/Northern Kentucky International Airport. Similarly, crews worked up to the boundaries of the 7,000-ac. airport, which maintains its own private stormwater system, and used inferred segments to create a seamless system.Other sites with private stormwater systems. If a public sewer collected runoff from a private site, crews would collect information until the structure was on private property. If a public sewer (main trunk lines only) ran through a private site, crews would inventory the structure through the private site.Highways. Woolpert worked with the Kentucky Department of Highways to obtain records drawings. Crews collected information up to the right of way along an interstate but, for safety reasons, did not enter the roadway. They used the records drawings to know where to start picking up information on the other side of the road. Inferred segments were used to create a seamless system.Other gaps in the stormwater drainage system. Woolpert and district staff attempted to resolve other connectivity issues in the field, such as with dye testing or the use of TV cameras in pipes, to discern why a gap existed. Crews also tried to obtain information from applicable communities’ public works departments. Sometimes the conclusion was to defer further investigation until the district assumed management of the entire system. If connectivity was not achievable, inferred segments were used to create a seamless system.Unique structures and situations. Unique structures and situations were flagged and photos were taken as necessary for review by district staff. Photos and reports were submitted to the district upon completion of each sub-basin so district personnel could conduct further investigation.
