State transportation officials and engineers are gearing up for a series of bridge repairs in the Selbyville area, slated to start in the fall of 2009. The three planned projects involve the replacement of corrugated metal pipes that have supported the roadways for more than 20 years and that are now increasingly at risk of failure due to corrosion — putting the roadways themselves at risk of collapse.
Delaware Department of Transportation (DelDOT) officials and engineers gathered at Selbyville Town Hall on Tuesday, Oct. 7, for a public workshop to introduce interested members of the public to the three proposed bridge replacement projects — all of which will involve at least two months of detours for motorists who usually use the affected roadways.
The existing corrugated pipes supporting the bridges were installed around 1970 and are now rusting out, threatening a roadway collapse if the bridges are not replaced. DelDOT now plans to install, in place of the metal pipes, concrete culverts that have an estimated lifespan of 75 years — nearly triple the proven lifespan of the metal support pipes.
Engineers said Tuesday that the failure of the metal pipes had proven particularly fast in the area of local tax ditches — perhaps as a result of chemical interaction with the fertilizers and other chemicals applied to nearby farm fields.
Regardless of the cause, the new concrete structures are expected to well exceed the metal structures’ lifespans and thus put off further replacement needs for nearly as long as an average human lifespan.
The projects are also planned to take place well ahead of the point when the pipes might collapse in an advanced state of corrosion. That could help avoid the kind of extended emergency closure that is currently in place on Beaver Dam Road near Ocean View and that happened earlier this year on Route 17 near Roxana.
In both those cases, the roadways’ metal support pipes gave way before repairs were ready to begin, causing the roadway to buckle and creating a dangerous situation for drivers.
Barry Benton, a supervising engineer for bridge design with DelDOT, said Tuesday that the Beaver Dam pipe had effectively “clamshelled,” forcing DelDOT to close the bridge area over the associated creek with no advance notice.
With permitting issues due to protected wetlands in that area, DelDOT officials initially feared it might take a year or more for the Beaver Dam bridge to be repaired. But they now say construction should be completed by the end of spring next year.
In contrast to those emergency closures, the three Selbyville-area bridge replacements are being planned well in advance — slated to begin a year or more from now — and the public invited to get all the information available at this week’s workshop.
As of July 2008, DelDOT had identified 40 of its bridges statewide that were considered “structurally deficient.” (DelDOT officials emphasize that the term “structurally deficient” is simply an engineering term that means there is a component on a bridge that needs attention.)
All 40 structurally-deficient bridges were either being worked on in July or were planned to be worked on. Of the 40 deficient bridges, 17 were roads over pipes or culverts.
Road improvements, detours planned
The first of the three Selbyville-area bridge replacement projects unveiled this Tuesday is set at Pepper Road, over Polly Branch. There, not only will the bridge be replaced and the support structure improved to the concrete culvert, but the roadway itself improved — widened by about 3 feet, from 10- and 11- foot lanes to a 12-foot travel lane with a 1-foot offset.
Engineers said the decision to widen the road was made due to the amount of traffic it is seeing now – a strong increase over the amount it carried when originally designed. Engineers also plan to give the location a “clean” design, offering grassy shoulders instead of a metal guardrail.
“You really won’t know the bridge is there,” the bridge’s designer said Tuesday. The project is expected to cost around $340,000.
As with the other two projects, DelDOT is keeping the environment in mind as well, meeting requirements for the environmentally sensitive areas by using permeable materials at the stream bottoms. Rip-rap will be used at the outlets and inlets of the streams under the bridges, to shore them up without impeding natural water flow.
At Pepper Road, an extensive detour will be necessary, but engineers said Tuesday that the exact route of the detour had yet to be determined, with construction start not expected until the spring of 2010. Significantly, that route is expected, Benton noted, to send motorists onto Route 113 at one point or another.
Along with the bridge and roadway improvements, the Pepper Road project includes entrance improvements for the three properties in the immediate area. Each of the properties will have those entrances from Pepper Road completely closed during the three- to four-month estimated construction period. But all three properties also have an alternate entrance from other area roads, engineers noted, limiting the inconvenience for their owners.
The other two projects that engineers introduced on Tuesday are smaller and simpler, limiting their construction period to an estimated 60 to 90 days, as well as the length of their associated detours.
On Baker Road (also called Gumboro Road outside the project area) where it runs over Sandy Branch, engineers said they usually only see about 56 cars per day, so the kind of extensive road improvements planned for the Pepper Road area aren’t planned there.
Instead, the existing two corrugated metal pipes that support the roadway over Sandy Branch will simply be replaced with a preformed concrete box culvert with the rip-rap at both ends, retaining the existing 10-foot land width on the roadway.
The detour for the project — slated to start in the fall of 2009 and take about 60 days for construction — will take drivers on Road 378 and Cypress Road, returning them to Gumboro Road. The project’s estimated cost is $410,000.
The third of the three planned projects will replace the bridge on Bearhole Road over Bear Hole Ditch, again using a concrete culvert to replace two corrugated metal pipes, under same 20-foot-wide roadway. The $410,000 project is expected to start between the fall of 2009 and the spring of 2010 and to run about 60 to 90 days in construction.
During that time, motorists will be detoured around the closed segment of roadway via Hudson, Dear Run, Zion Church and Johnson (Route 54A) roads.