Installed over a century ago, the two 36” diameter cast iron sewerage force mains transporting all of the sanitary waste out of Atlantic City, NJ, were quickly becoming a problem for their owner, Atlantic City Sewerage Company (ACSC). The ACSC made the decision to replace both aging force mains and retained Buchart-Horn to prepare the construction documents. Carson & Roberts, successfully won the contract to horizontal directional drill the replacements force main under marsh lands and the Penrose Canal in Atlantic City, NJ.
In March 2011, Carson & Roberts mobilized our million pound rig to the job site and by July 2011, successfully drilled and installed two parallel 42” diameter HDPE DR 11 force mains over 2,200 linear feet each.
Horizontal Directionally Drilling a 2,200 linear foot shot of 42” diameter O.D. is not uncommon these days; however, accomplishing it with over a 71 degrees horizontal bend in it and repeating it within 25’ of the first drill has made it the most complex drill Carson & Roberts has completed to date.
The most challenging aspect of this project was not encroaching on a property corner directly in-line of the ideal drill path. To avoid having the new force mains on someone else’s property, a path and profile was designed with an 800’ compound radius. With Horizontal Technologies providing their steering services, the pilot hole never deviated more than 2’ from the intended plan. From there, we proceeded to pull a 36” reamer down hole, followed by a 60” ream pass. After a few passes with a 48” ball, the entire 2,200 l.f. of 42” O.D. HDPE was pulled into the hole over a 12 hour period. The same process was repeated for the second drill and it was completed within a three week period.
Pushing the envelope for drilling was an understatement according to one of our most experienced drill superintendents. “The most I ever bent a drill was 60 degrees. At 71 degress, we were all walking on egg shells until we saw the pipe come out of the hole. And having to do it all over again is truly a remarkable feat.”
Such an extreme horizontal radius would not have been possible without suitable ground conditions, stated Scott Murray, P.E., Senior Vice President for Carson & Roberts Trenchless Division. At 50’ deep, the organic over burden of the marsh land and channel quickly turned into a cohansey sand layer that provided enough stability to steer the pilot. However, we did install a 12” conductor barrel through the organic layer to serve as bearing support for the drill steel. Fortunately, we had enough room to fuse and stage the entire 2,200 l.f. of product pipe prior to pullback. With the pipe filled with water, the pullback force never exceeded 150,000 pounds!
Owner: Atlantic City Sewerage Company, Atlantic City, NJ
Project: St. James and New York Forcemain Replacements
Location: Atlantic City, Atlantic County, NJ
Prime Contractor: Carson & Roberts, Lafayette, NJ
Engineer/Designer: Buchart-Horn, Inc.
Steering Contractor: Horizontal Technologies, Houston, TX
Pipe Size/Length: 42″ O.D. HDPE DR11
Installation: Horizontal Directional Drill
Bob Carson-VP of Business Developement (201) 230-4686,
[email protected]