Protruding Pilings Challenge Power Station Construction

Staff | September 28, 2010

Increasing energy consumption in New York City prompted Con Edison, one of the nation's largest investor-owned energy companies, to build a substation that would help meet the growing demand. Con Edison turned to D'Onofrio General Construction for the expertise and equipment that could easily handle backfilling material on the job site's ever-changing elevation.

Standing where an old Farberware facility once stood in the Mott Haven section of the Bronx, the substation has been in the planning stages for several years. Demolition of the Farberware facility began in January 2005 and construction for the new substation started in July 2005.

"We needed to build a substation to meet New York City's current and future energy needs," notes Brian Yee-Chan, chief construction inspector with Con Edison, the developer of the job.

"One of the first sections of the project we worked on was backfilling a portion of the four-acre site" comments Chris Waddicor, D'Onofrio General Construction's Project Engineer for the Mott Haven Substation. "The logistics of this section of the project did not allow easy accessibility of most machines."

"We drove hundreds and hundreds of large steel pilings into the ground of the job site that would eventually serve as the structure's foundation," says Yee-Chan, "We had to use a large pile driver to drive the piles into the ground. After we drove each pile into the ground, there were portions of the piles sticking out of the ground five to 10 feet high, making the area hard to maneuver around."

"Because of the uneven elevation, and safety being a top priority on the job site, we knew we had to find a concrete pumping company that had a machine that would clear the extreme elevation obstacles this section of the project presented and be able to place the backfill exactly where it needed to be placed," says Waddicor.

"Neither a bucket fill process, an excavator machine nor the smallest skid-steer loader would have gotten this portion of the job done," says Eugene Reed, Operator of the TB 110 on the project with Alexander Wagner Company, Inc. "The TB 110 came to mind immediately when we were approached by D'Onofrio General Construction." Reed and the TB 110 were on the project off and on starting in September 2005 and ending in October 2006.

"With the TB 110's outrigger set up on rough terrain and its 106-foot-1-inch horizontal reach, the belt was able to surpass the hurdles of the ground beneath and place the backfill," notes Reed.

Three main types of backfill were conveyed by the TB 110 on the Mott Haven site. Frequently, the different materials were all placed separately on the same day with the same setup. "The different types of backfill consisted of thermal sand, which was used as a buffer around the electrical conduits; conventional backfill and gravel, which were used to lay under a slab on grade," Yee-Chan notes. "The amount of each type of backfill conveyed by the TB 110 and amount of time it took to place depended on the location of the placement and the application of the backfill.

"About 50 percent of the total backfill needed for the project was placed by the TB 110," says Yee-Chan. The remaining 50 percent of backfill was placed by a conventional front-end loader for the more stable ground sections of the job site. "The TB 110 was, no question, a huge asset to have on the project."

Although Alexander Wagner Company, Inc. was primarily on the job site for backfill, the project also required the Telebelt to convey concrete for slab on grade work. This included a floor in one area of the substation. The slab on grade now supports a water-proofing system that was installed on top of it.

"The mix for the slab on grade was very harsh. It consisted of 1-1/4-inch to 1-1/2-inch jacket stones, which are very sharp and jagged," notes Yee-Chan.

There are currently about 110 workers on the Mott Haven Substation job site. As of early March 2007, most of the civil and structural elements are complete for the project, which was slated for completion in May 2007.

Yee-Chan says there are other Con Edison substation projects similar to the Mott Haven facility occurring in the New York City area to meet energy needs. Con Edison is a subsidiary of Consolidated Edison, Inc., with approximately $12 billion in annual revenues and $27 billion in assets. The utility provides electric, gas and steam service to more than 3 million customers in New York City and Westchester County, New York.