Utility improvements challenging part of project
People driving, bicycling, or walking along Keystone Road certainly notice the visual appeal of the new corridor – the pavement, improved views, and sidewalks and trail. But it’ s the work that occurred underground that caused the biggest obstacles and required the most decision-making during design and construction.
Relocating or upgrading the major utilities under or above a major thoroughfare reconstruction like Keystone Road always is a challenge, said Brian Symanski, project manager for David Nelson Construction, the project’ s general contractor.
“ The County and City gave us as much data as they could,” he said.“ We found a lot of times that when we got in there, the lines where not where they were shown. They were deeper, shallower, or in a different horizontal alignment. That made things a lot more difficult, a lot trickier. You wonder how they laid it originally.”
The contractor was flexible during construction, and working with Ayres Associates as the designer, the unforeseen circumstances were remedied quickly, said Joseph DeMoss, engineering support services supervisor for Pinellas County.
“ Some of these utilities were constructed back in the 1950s,” DeMoss said.“ We had spotty information, asbuilt plans. We had a lot of problems with that. The SUE( subsurface utility engineering) is only as good as the spots you do the check on. And what ended up happening was that in between the points, the lines would move. You expected to go from point to point, and they didn’ t. They would shift alignments or kept crossing each other.”
The more significant challenge was finding a suitable route to relocate and repair the City of Tarpon Springs’ old 20- inch water line, one of the city’ s main sources of water, said Gary Schurman, engineering projects supervisor. The City’ s goal was no interruption of service, Schurman said,
and Ayres Associates’ custom-designed thrust blocks and anchors allowed this to happen.
Thrust blocks are anchors used to counter the thrust forces that occur at changes in direction, at changes in the crosssectional area, or at the pipeline termination in a pressurized pipe, said Dori Sabeh, Ayres Associates’ lead utility designer for the project. They increase the ability of fittings to resist movement by increasing the bearing area. The custom-designed thrust block secured the live tapping valves and line stops for the shallow connections. The design provided for a pipe layout to allow safe future maintenance around retaining walls and tie-back walls, Sabeh said.
“ In addition to providing a layout to avoid the retaining walls / tie-backs and allow for future maintenance, a major design concern was how to restrain the proposed tapping sleeve and valve as well as the adjacent line stop at the shallow connection point with the 12-foot-spaced, lead joint, existing water main,” Sabeh said.
“ We considered this challenge as a perfect opportunity to practice what we excel at – providing innovative solutions. We custom-designed an encasement for the connection’ s adjacent lead joints, which served as a thrust block for the tapping sleeve and valve as well as a reverse dead man to the line stop.”
In the end, Tarpon Springs residents and businesses saw at most a few minutes of lowered water pressure throughout the entire project, Schurman said, with most never even noticing a change.
“ We wanted no interruption of service. It was something we asked for early on in the project. We didn’ t know how that would be possible,” he said.“ As we worked through it( with Ayres Associates), we were able to come up with a way to do it, to isolate the pipes, so there really was no impact.”
– Eric Widholm
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