Trends Spring 2015 - Page 18

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
18│TRENDS
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