Work continues to progress on the 29th Street Bridge over the C&O Canal, the third of the $6 million Three Bridges Project to since work began in August 2009. Unlike its counterparts, the 30th Street Bridge and Thomas Jefferson Street Bridge, the third phase is complicated and will require the full time estimate, through July 2012.
Work on the 30th Street bridge lasted about 11 months and took a mere eight months.
"I think a lot of people in the community were very optimistic that we could finish the project early," said Mike Gales, the project engineer for RK&K.
"We were hoping, but I don't think that will happen...it's gotta be done in phases," said Gales about this, the third bridge.
"It’s really too bad...they had put a lot of time in the bank and it looked like they were going to deliver earlier than expected," said Mark Clabaugh the DDOT project manager.
But the delays are just part of the process,"you never know what you're going to find," added Clabaugh.
The first two bridges could be completely demolished at once and then rebuilt, but the 29th Street bridge has to be done one half at a time because of the various utility lines that run beneath the bridge.
It runs over a gas line, a water line, PEPCO lines and various telecommunication lines, all of which need to be accommodated during construction.
Gales said the project team has had meetings with the utility companies starting in 2009 and then again when work commenced on 29th Street in February.
Washington Gas had to relocate a gas line to a temporary line. Then there's the fact that DC Water's infrastructure in the area is old and has caused issues with turning off water valves in the area.
Much of the timing depends on the utlitiy companies, "we're going to be at their mercy," joked Gales.
On the positive side, added Clabaugh, since the other two parts of the project were ahead of schedule, the delays encountered by the 29th Street bridge should not prevent the project from wrapping up by July 2012.
In addition to coordinating the construction with utility companies, the construction project is also technically difficult.
Currently the contractors are performing a process called "jet grouting."
"It's like taking a big blender underground" that mixes in water and cement to relieve the canal walls from soil pressure, explains Gales.
The walls are slowly collapsing at an inward angle from the top, where they measure 14 feet apart from one another; they are 15 feet apart at the bottom.
The jet grouting helps remove soil pressure from the walls, ultimately extending the life of the walls. The bridges date back to the 1920s and the canal and the walls date back to the 1820s.
The next step is drilling foundations and inserting micro piles instead of driving a pile into the ground; this helps protect the foundations of nearby homes and businesses. The sixteen micro piles will line the north and south end of the bridge in an east to west direction. The drilled foundation work should begin later this week, estimated Gales.
Once the micro piles are in place, the contractor will pour a cement "footer" foundation. Then comes the bridge deck, which is a concrete base on the 30th Street and Thomas Jefferson Street bridge.
"This bridge is different in another respect; it's a fiberglass bridge deck...this will be the District's first," said Gales.
The fiber-reinforced polymer (FRP) bridge deck is an experiment, funded with Federal Highway Administration monies, to see how the material handles wear and tear compared to other bridge decks. Gales explained that one of the assumptions is that it will not have issues with corrosion since there is no steel involved, unlike concrete which uses reinforcing steel.
The FRP would then be covered in pavement, appearing just like the other two bridge from the surface.
Is the project on budget?
"We've had some change orders...they're within reason. We don't have massive cost overruns," said Gales.
"At this stage in the projects it’s hard to forecast where we’re going to end up, but it’s fair to say we’re close to budget," said Clabaugh.