Emergency Relocation of 20 Inch Sewer Force Main (HDD)

The Miami International Airport (MIA) sanitary system discharges into the Miami-Dade Water and Sewer system, via an existing 20" C.I. Force Main located on NW 21st Street, which was built in 1964. On January 25th, 2010, this main trunk line failed and sewage started to surface on the MIA access ramps. In an emergency meeting between the MIA and M-D WASD, it was agreed to replace the existing force main with a new 20" HDPE Pipe that would be installed as an emergency via Horizontal Directional Drilling (HDD) to avoid complications and possible MIA down time. Challenges faced by this project include calculating the proper alignment, radius of curvature, and entrance and exit angles of the new pipeline to provide sufficient vertical and horizontal clearances from high mast light poles, overhead electric poles, drainage structures and existing utilities, in addition to facilitating a clear path for directional drilling below the foundations of Ramps K, I, and L servicing the Miami Intermodal Center. The well executed design in close coordination with the Contractor of the emergency operation allowed construction to take place within a week's time, with no major setbacks. The scope of this project was the design and construction of a 20-in force main (800 LF) using High Density Polyethylene Pipe (HDEP) that was installed by Horizontal Directional Drilling (HDD) to replace a failed section of an existing 20-inch diameter force main that serves the Miami International Airport (MIA). The HDD process begins with boring a small, horizontal hole (pilot hole) under the crossing obstacle (i.e. a highway) with a continuous string of steel drill rod. When the bore head and rod emerge on the opposite side of the crossing, a special cutter, called a back reamer, is attached and pulled back through the pilot hole. The reamer bores out the pilot hole so that the pipe can be pulled through. The pipe is usually pulled through from the side of the crossing opposite the drill rig. Proper selection of pipe involves consideration not only of installation design factors such as pull-back force limits and collapse resistance, but also of the long-term performance of the pipe once installed in the bore-hole.