Horizontal Direction Drilling for Sewer

PPS has been designing and managing Horizontal Directional Drill (HDD) projects for use in the natural gas industry for years. HDD is a process that helps overcome many issues associated with open-cut trench installation. HDD is well suited for roadways with many existing utilities, or high traffic volumes. It is also perfect for river and railroad crossings. PPS recently designed a HDD for a client that crossed under the Merrimack River and the Pan Am railroad. The HDD design was to connect a proposed sanitary pump station to the Town’s sanitary treatment facility. The project involved a 1,300 ft bore, for two 8” HPDE pipes to be pulled at the same time 30 ft below the Merrimack River. The HDD driller was also required to fill the annular space around the pipes with grout under the zone of influence of the railroad. 

The project required the HDPE pipe to be butt fusion welded. The fusion process creates a bead on the inside and outside of the pipe. Because sanitary pipe requires a smooth wall connection on the inside, a special tool is used to remove the inside bead from the pipe.

There is a lot that goes into the design of an HDD for sanitary systems due to its limited line and grade specifications, but it was the perfect application for the force main.