KS Associates takes 3D scanner underground to help abate CSOs

Elyria, Ohio — Civil engineering and surveying firm KS Associates, Inc. completed surveying and 3D laser scanning services for a complex Northeast Ohio Regional Sewer District (NEORSD) project. The NWI Edgewater Park Gate Project is part of the district’s ongoing investment in infrastructure improvements aimed at improving the quality of Northeast Ohio waterways.

The goal of this project was to replace a fatigued inflatable dam in the 96-inch sewer that collects combined sewer flow from northwest Cleveland. The inflatable dam is an important mechanism that stores upstream combined sewer flow, reducing CSO discharges in the collection system before the flow is transported to a nearby wastewater treatment plant. NEORSD decided to remove the inflatable dam and replace it with a more efficient hydraulic sluice gate. NEORSD hired URS Corporation to perform design services.

URS contracted with KS Associates to perform an internal survey of the chamber. According to Alan T. Stadler, P.E., URS Corporation’s Northern Ohio Civil Infrastructure Program Manager, “KS and URS have collaborated on numerous projects in the past. We were aware of KS’s surveying capabilities and trusted that they would provide comprehensive, reliable data.” URS needed detailed information regarding the chamber geometry for design of the new sluice gate and to provide construction contractors with detailed specifications. After gaining an understanding of the project goals and challenges, KS Associates recommended the utilization of its 3D laser scanning technology.

Laser scanning offered several benefits over conventional surveying methods. According to Mark A. Yeager, P.S., KS Associates Director of Surveying Services, “For safety reasons, surveyors could only enter the sewer during dry weather flows. Once we had our window of opportunity, accessing an active sewer five stories below ground posed safety challenges and required specialized confined-space procedures. Our priority was to measure the entire junction chamber and obtain the geometry that URS needed in as little time as possible. Using 3D laser scanning, we successfully gathered all the data and more — in one trip. Manually obtaining these details would have required more time at the project site and would have been more physically challenging.”

KS Associates created a 3D CAD drawing from the 66.5 million scan points captured during the survey, which provided details on the characteristics of the chamber. The drawing included the location and dimensions of the inflatable dam, the chamber’s sloped bottom, and a channel that drops steeply within the chamber. According to Yeager, “Depicting this information with conventional two-dimensional sketches, field notes, and survey data would have presented limitations for map preparation. With laser scanning, KS Associates extracted the data in a virtual 3D environment greatly improving, the reliability of the deliverable.”

Laser scanning also offers data re-mining benefits. A point cloud containing details of the entire junction chamber eliminates the potential need to re-mobilize surveyors should additional data be needed by the design team. Laser scanning also enhanced the bidding process. NEORSD utilized 3D point cloud imagery in bid presentation materials, showing vantage points of the project site that would have otherwise been unavailable or too costly to produce via multiple plan views.