Miscalculations and unforeseen snags will cost Alpharetta an extra $151,000 for its Big Creek Greenway Extension project.
The new construction extends the trail 800 feet east from its current end point, then crosses under Webb Bridge Road. From there, it spans Big Creek over a 121-foot bridge. Total cost of the extension was bid at $1.26 million, but the overruns will raise the cost 12 percent to $1.41 million.
Officials said this week that work crews discovered uncharted water and sewer lines while installing the walk-through culvert under Webb Bridge Road last summer. Modifications required $69,000 of additional work. Workers also discovered additional areas of soft subgrade along the path that required reinforcement at a cost of $30,000.
The city faced another $52,000 in added expenses when crews discovered estimates for materials fell short of the supply needed to construct the bridge over Big Creek and the elevated boardwalk.
Pete Sewczwicz, public works director, said construction snags due to utility lines are not uncommon. In this case, the survey failed to note a 30-inch Fulton County water main, he said. Moreover, sewer lines had to be reconfigured to accommodate new construction nearby.
The real concern, Sewczwicz said, is the miscalculations on the bridge and boardwalk. Those measurements should not have been off, he said.
"You're relying on the structural engineering firm you hired to ensure the quantities are accurate," he said. "That is more frustrating for me than anything on the change order because they controlled it."
The city is currently updating its pool of engineering and surveying firms it will use for future projects.
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