A formidable 1,200-ft. (365.8 m) long and 200-ft. (61 m) high mountain is just one obstacle that lies in the path of the new section of I-99, now under way.
Travelers, including State College-bound students, currently use Route 220 from the South or Route 322 from the West. These routes intersect at a small town called Port Matilda frequently causing a “bottleneck” effect.
“The new section of I-99 will be a four-lane divided interstate and will run parallel to Route 220,” said Tom McNally, construction manager of The Pennsylvania Department of Transportation (PennDOT). “The existing highway sees 18,000 cars per day. It’s a two-lane highway and just doesn’t have the capacity for current or future traffic demand.”
The new interstate will decrease the number of wrecks and fatalities caused, in part, by the congestion on old Route 220.
Construction of the 18-mi. (29 km) stretch of new highway from Bald Eagle to Port Matilda began in summer 1999, but research for the project dates back to the ’80s.
The project has an estimated completion date of December 2007 and will cost $350 million. Bids were won by four contractors: Trumble, HRI Inc., A&=L Contracting and New Enterprise. The 18 mi. were divided into eight contracts. New Enterprise was awarded four of them. A&L Contracting, Trumble, and HRI received one contract each. The remaining contract is for paving and will be let in spring 2006 for bidding.
During the winter, each job site had approximately 30 to 40 workers, with as many as 60 workers in the summer months. By completion of the project, more than 18 million cu. yds. (13. 8 million cu m) of earth will be moved and 290,080 cu. yds. (221,782 cu m) of concrete will be in place. This new section of I-99 ties into the existing I-99, which runs from Bald Eagle south to the Pennsylvania Turnpike and I-80 to the north.
Most of the interstate is sidehill cut and fill, common to the hilly terrain of Centre County, PA. The roadway progresses through the 200-ft high mountain with sides of 1.5 to 1. The mountain is located at the intersection of Route 350 where it ties in with I-99 just north of Tyrone.
While excavating the mountain, crews uncovered pyrite rock, which caused a new challenge for the operators. When water hits the sulfur inclusions in the rock, sulfuric acid is generated, which can be harmful to plants, animals and the environment. Although the solution is diluted (with a PH only as strong as lemon juice or soda), the pyrite rock must be capsulated and buried in the bottom of surrounding fields to prevent exposure to the elements.
Another natural hurdle contractors are experiencing is sink holes. With sink holes occurring during the construction of a bridge, more rock and concrete is added to level out the ground. There’s more specialized work for the contractors creating sedimentation ponds.
“Any place that water discharges off the work site, a sedimentation pond must be put in,” said James Au, project manager of A&L Contracting.
In the eight-mile section that his company worked on, four ponds were installed to give the sediment a chance to settle on the bottom and provide clean-up water at the top. Once the pond reaches a certain level, the filtered water will travel through a pipe to nearby streams.
“Sink holes and sedimentation ponds are fairly common with the construction of roadways, so neither caused any significant set-backs for us,” said McNally.
PennDOT officials estimated that the surrounding community and college-bound students can expect to decrease their travel times by 10 to 12 minutes with the opening of new I-99 in winter 2007.