Chicago-based Pan-Oceanic Construction is in the midst of upgrading the sanitary sewer system on the city’s Lower West Side along West Cermak Rd. and West 18th St. Pan-Oceanic is adding four new junction chambers to connect 54-in. RCP sewer pipe, plus many other upgrades — all in the effort to relieve the large amount of flow passing through the aging, existing sewer system.
Any type of excavation project in a heavily urban area is fraught with challenges, even more so when dealing with original infrastructure that may be centuries old. In order to install new sewer pipe and structures, a contractor may need to excavate and work around existing utilities that are currently active as well as utilities that may have been inactive for decades.
Adding to the difficulty of the excavating project, contractors must assure that workers in the excavation are kept safe at all times. That means having the proper shoring system in place. However traditional shoring systems, such as trench sloping or trench boxes, may not be possible when the working pit looks like a bowl of spaghetti of crossing pipes and conduits.
Pan-Oceanic needed a non-traditional shoring system for this project, something designed specifically to shore around crossing utilities and existing structures.
Finding the Answer
Through the bidding process, Pan-Oceanic connected with Efficiency Shoring & Supply, one of the leading trench shielding and shoring suppliers in the Chicago area. “It was simple, really,” says Blake Stevens, Efficiency Shoring & Supply’s Shoring Specialist. “There are very few shoring systems that are designed to handle multiple crossing utilities, and we suggested a Shore-Trak Cross-Trench Utility Shoring System, manufactured by Efficiency Production.”
Shore-Trak consists of a series of sheeting guide frames that sit level on the ground or in an excavated pilot hole and connect together in a four-sided configuration typically by sliding the ends of the guide frames into Slide Rail System corner posts; or, as Pan-Oceanic did it, connecting the guide frames with specially designed corner brackets that pin over spreader collars welded onto both ends of the guide frame. In this configuration, Slide Rail posts are not used, which simplified installation.
Next, KD-6 sheeting is stood up and overlapped in the 7-in. slot in the guide frame, and then the individual 18-in. wide sheets are pushed individually to grade which allows the sheeting to closely shore around any crossing pipes, conduits or other utilities.
A Problem Spot
At one particularly difficult excavation location — at the intersection of Cermak Rd. and Hoyne Ave. — Pan-Oceanic needed to dig down 19 ft and expose a 9-ft diameter brick sanitary sewer pipe which has been in use since 1844. Once uncovered, the sewer pipe was cut open horizontally for 30 ft and a new concrete personnel-access junction chamber was poured-in-place over the exposed brick sewer pipe and connecting pipe running into the junction chamber from a 45 degree angle from the northeast.
The entire working pit was 36 by 26 ft, and needed to be dug to 19 ft deep. However, at 15 ft deep, Pan-Oceanic hit bedrock which prevented them from driving the sheets to the complete depth. At that point, Stevens called in assistance from Efficiency Production’s Special Operations Shoring Division who sent out Senior Slide Rail Installer Rod Austin.
“When the contractor hit bedrock we needed to pause and reassess the engineering for the shoring system,” explains Austin. “What we decided to do was weld i-beam walers across the sheeting at about 15 ft — the depth the contractor hit bedrock — which basically prevented the sheeting from kicking in to the open excavation. Then the contractor could chisel out the bedrock to the required depth for them to pour the structure.”
“The system worked perfectly, no problems at all,” says Marty Mele, Pan-Oceanic’s General Superintendent who oversaw the installation of the shoring system. “If it didn’t work great, we wouldn’t use it again,” he insisted. “And we’re using it again.”
James McRay is the Director of Marketing and Media for Efficiency Production Inc. He can be reached at firstname.lastname@example.org.