REBUILDING THE "EL"

by Mike Fernandez

Philadelphia, PA. 4/2003 - The Market Street Elevated Train System that has served the people of Philadelphia since 1912 is currently in the first phase of reconstruction. The "EL", as it is referred to by locals, is being refitted with new structure foundations, piers, duct banks, and other utilities that will support the newly designed guideway superstructure. The Southeastern Pennsylvania Transportation Authority (SEPTA) awarded a $41 million State and Federally funded contract for the first phase of the project to Driscoll Construction, Inc., of Springhouse, PA in January of 2002. The project, designed by DMJM & Harris Consulting Engineers and Gannett-Fleming of Philadelphia, consists of installing 147 foundations and piers along a 2 mile Market St. corridor from 44^th St. to 63^rd St.

Driscoll Construction is relying on its 60+ years of experience in tunneling, sewer construction, pile driving, highway work, as well as bridge and foundation work to deal with the many challenges that this project presents. One of the main challenges indicated by Jim Driscoll, VP and Project Superintendent, is that overhead clearance for machinery and shoring equipment is very limited due to having to work directly under the existing train guideway. Other challenges include working around existing underground utilities, relocating utilities, and keeping construction vibration to a minimum to avoid potential damage to surrounding homes and businesses. Driscoll’s crews also have to maintain access for the high volume of Market Street traffic traveling on both sides of the "EL" during construction.

Since driving "H" Piles for the installation of conventional wood lagging is prohibited and pre-drilling for "H" piles is not considered to be cost effective, Driscoll has chosen a shoring alternative that fits the requirements necessary to shore the excavations, construct the pier foundations, and install the piers.

Driscoll called on Jay Kerrigan and Dave Martosella of Trenchtech Inc., based in Conshohocken, Pa., to recommend a shoring system that could be installed within the confined areas, work around the existing utilities, adjust to the differing dimensions of existing support columns, and be installed and removed quickly with minimal vibration. Kerrigan demonstrated an Efficiency Production, Inc. Shore-Trak^tm cross trench utility shoring system, explained Jim Driscoll, "We looked at the setup in Trenchtech’s yard and it started the ball rolling!"

To meet Driscoll’s shoring criteria, Kerrigan contacted Mike West, Director of Engineering at Efficiency Production, Inc. of Mason, Michigan, who quickly designed a modification to Efficiency’s Shore-Trak^tm that would allow it to be adjusted to shore the various support column pits that ranged in size from 13x16 ft. to 16x32 ft. wide. This was accomplished by fabricating special one, two, and three-foot long bolt-on extensions to attach to the Shore-Trak^tm guide frames. The adjustable guide frames were also made to receive overlapping sheeting instead of fabricated Shore-Trak^tm panels.

These solutions that made it possible to install the system in the extremely difficult locations convinced Driscoll to purchase sixteen sets of Efficiency’s Shore-Trak^tm guide frames to allow work to be performed in up to eight different pier locations simultaneously!

This system which is designed to be compatible with Efficiency’s Universal Slide Rail System includes the following components: 16 sets of Shore-Trak^tm guide frames 4’ high by 13’ and 16’ feet in length, specially designed 4’ Slide Rail / Shore-Trak^tm corner posts and linear posts for connecting frames, parallel beams and spreaders. The guide frames are used, in this case, with overlapping KZ 750 sheeting.

Using Efficiency’s system will be more cost-effective than conventional beams and wood lagging. "Since we were not allowed to drive the beams we would’ve had to pre-drill and set the beams in a rock socket," stated Driscoll. "It would have been costly, time consuming, and more labor intensive doing it the conventional way." He added, "We would’ve had to fabricate the wale rings, set them and remove them, and run the beams and lagging." Andrew Bolduc, Driscoll’s crew foreman, confirmed, "Years ago we used to just put wood in, but it’s a lot easier and faster with this system!"

The pier construction sequence consists of excavating and shoring each pit at the specified pier location, drilling and pouring the pier foundation, then forming and pouring the pier. It took the crews about one day to learn how the shoring system worked. Once the short learning curve was bridged the crews were able to excavate and install the system within an average of one day per pit. Driscoll’s Chief Field Project Engineer, Wayne Spang, noted, "One thing that is very helpful is that the crews can continue to work on multiple piers…after pouring the footings they can retrieve the guide frames immediately and use it on the next pier excavation."

Driscoll is using a Samsumg model SE 210 L excavator to dig and install the shoring system in the confined areas. They also have a small rubber-tired Gradall, two Terex Stinger model BT4700 boom trucks, specialized foundation drilling equipment, a Case 580 tractor backhoe, and many smaller support pieces on site.

Efficiency’s system is fulfilling the priority that Driscoll placed on jobsite safety and it also provides the added value of increased production with the system’s versatile and "easy-to-use" design. Jay Kerrigan stated, "The ability to adapt to conditions with the system’s extensions and the resiliency of the frames are tremendous assets!" Bolduc echoed the remark, "No deflection on the sheets...we’ve been banging on them pretty good but they’re holding up well!"

Troy Simms, Driscoll’s Safety Director, commented, "SEPTA is pleased and everyone likes the [shoring system]." He added, "It’s worked great! It’s easy to work with and once the system is in place it’s secure and we don’t have to worry about it!"

The project is currently on schedule and slated for completion in Nov. 2004.

Efficiency’s special shoring system installed in confined area under guideway superstructure.		"EL" guideway runs through congested Market St. area where vibrations could cause damage to surrounding structures.
New guideway foundation and pier.
		Trenchtech’s Kerrigan and Martosella (in blue), and Jim Driscoll inspect shoring system.