A new technology that is emerging in underground infrastructure replacement is A pipe bursting@ . Pipe bursting is an installation method for replacing pipes, in place, with minimal excavation and surface disturbance. Bursting can be done on watermains, sewers and gas lines. Materials such as cast iron, ductile iron, steel, concrete, PVC and vitrified clay pipe can all be A burst@ .

The method uses either a static, pneumatic or hydraulic tool which is pulled through the pipe to be replaced with a winch. The tool exerts outward force on the old pipe causing it to break as the tool is winched forward. A replacement pipe, either polyethylene or PVC is attached to the tool or A head@ and is pulled along as the head bursts the old pipe. In using pipe bursting, equal or larger diameter pipe can be installed because the head can expand the hole as it progresses.

Speed of replacement is much greater than with open cut. Bursting is especially applicable to trunk sewers or water transmission mains where there are few, if any, service connections. It is very beneficial where surface or subsurface obstructions limit space for new construction.

Limitations to bursting include the necessity to remove the old pipe from service during the replacement, individual excavations for re-connection of services, inability to traverse sharp bends and displacement of the ground surface in certain shallow installations.

We are in the midst of completing a sanitary sewer replacement project for the Village of Westfield. The project called for 1655 linear feet of an 8 inch VCP trunk sewer to be replaced in a heavily treed and steep terrain (35%) across Chautauqua Creek. Due to the site conditions, pipe bursting was chosen over parallel construction of a new sewer. Underground Technologies, Inc. of Rochester was the low bidder at approximately $124,000. Once setup on site the bursting and installation of pipe was accomplished at a rate of 3 to 4 hours per 400 foot run. Existing brick manholes were rehabilitated by inserting a fiberglass liner and then grouting between the manhole and the liner. The project will be completed in the spring with pipe testing, televising and minimal surface restoration.

Horizontal directional drilling is a trenchless method of construction for the installation of underground pipes, with minimal disruption to traffic, business activities, and environmentally sensitive areas. This technology evolved through the merging of technologies from the oilfield, utility, and water well industries.

Installation of pipe is conducted from the surface, and commences with the boring of a pilot bore along the path of installation. The pilot bore is launched from the surface at an angle between 5 and 20 degrees, then gradually becomes horizontal when the required depth is reached. The bore can be steered and tracked from the surface using a walk over line locator to direct the bore to the exit location. Once the drill string reaches the surface at the exit location, a back reamer is attached to the drill string and pulled back to the entry point. This process enlarges the borehole for the installation of the product line. To achieve the appropriate bore size it may be necessary to perform several back reaming operations. The pipeline is installed once the borehole is enlarged to the diameter that comfortably accommodates the pipe.