Montour Trail-Letter

by Jack Peth

The construction of the Quicksilver Bridge is a project like none previously undertaken by the Montour Trail Council. To date our bridge work has consisted of the re-decking of existing spans. Quicksilver is a new bridge from the ground up which crosses the busy State Route 980.

The Montour Railroad did have a bridge at this site but with the closing of the rail line, first the bridge deck and then the bridge abutments were removed due to poor vertical clearance and the bad alignment of the road passing under the short span. All that was left, as the Montour Trail came on the scene were the elevated berms stopping short of PA980 and an access ramp to the South Abutment area.

The Trail Council used this ramp and an old spur line at the McDonald Trestle as access points and improved and surfaced the trail between these access points. The locals get a lot of use from this opened section but were isolated from the 11.5 miles of opened trail, to Boggs, by the rework of the old coal prep plant area and most significantly, the missing bridge at Quicksilver.

The Trail Council hired an engineering firm, (Makin Engineering Co.), to design the new bridge and make detail construction drawings. The heart of this bridge is to be a 137 Ft steel thru truss span of tubular construction which has a 7'-6" cross section. The span will clear PA980 by 17'-6."

This steel truss was acquired several years ago when the Montour Trail Council was offered an attractive price due to the use of Canadian steel that was refused by the purchaser, Uncle Sam. The two +/- 70 Ft pieces of the bridge have been delivered to the site. Volunteer labor and donated use of construction equipment by Dennis Frank and his associates got the four main cord splices high strength bolted and the secondary members field welded. Once the span was one piece the MTC/BB (Montour Trail Council Bridge Builders) got to work on the installation of the 2" x 6" treated wood decking. The decking is being attached to the steel with self-tapping screws. Ask someone who worked on the decking how many drill bits & #3 Phillips bits they went through. The decking cannot be completed until all the form work for the abutments is completed as the balance of the 2" x 6" boards are used in the forms. The decking, handrail & fencing will have been completely installed prior to the bridge being set in place. This is the type of work the Council has done on many bridges.

Now, on to what's new & different about this project. The MTC/BB have undertaken to act as the Contractor for the construction of the abutments, (the concrete structure that supports the end of the bridge). There ain't no THEY, there is just US. If it's required, we have to do it.

An excavation contractor, Greg Orient, has offered his time, construction equipment, (a 1CY track mounted backhoe and a 14 wheel dump truck) and the fuel they use. The South Abutment was excavated on April 1. Greg is now scheduled back in June to excavate the North Abutment.

When the machine excavation is complete it is necessary to do hand digging to get to the top of sound rock on which to pour the concrete footer.

Each of the Abutments consists of 5 pours of concrete: non-pay lean fill, footer, bridge support pier, right side wall, and left side wall.

The modular form panels were built from scratch by the MTC/BB. The typical panel has a 3/4" plywood face and 2" x 4" framing. Most panels are 2 Ft x 8 Ft. In wall type construction, steel rods called Snap Ties are used to hold the wall sides together and resist the pressure of the wet concrete.

The method used to connect (tie) reinforcing may be of interest. Will all Local 3 members please move on to the next paragraph. The tie that is used by us is called a "bag tie." It is a 6" length of soft wire with a 3/8" loop formed at each end. After the tie is passed around the intersecting reinforcing, a hooked tool is inserted thru the loops and twisted with a simple wrist motion to tighten the wire around the reinforcing. Do you remember the wire that used to be twisted around a peck sack of potatoes? That's IT. Most of the reinforcing bars are 5/8" diameter.

The concrete, in mixer trucks, is delivered to the site dry and the concrete is mixed while the truck is at the site. Once the concrete placement is completed the excavated earth must be backfilled as layers, and compacted with vibroplate tampers. The MTC loader can do some of the dirt moving but a large amount of hand labor will be required. This is not a high skill job, rather a "Labor of Love."

So, where do we stand? The South Abutment is in the Home Stretch. The lean fill, footer & bridge support pier have been poured & stripped. On Wednesday, June 14, 2000, the fifth and final pour on the South Abutment of the Quicksilver Bridge was placed. We are now looking ahead to the construction of the North Abutment. The North Abutment is now being scheduled for excavation in June. If all goes well we expect the Bridge Truss can be hoisted into position in early August. That's the 'Plan' not a promise!