Date: Fri 24-Nov-1995
Date: Fri 24-Nov-1995
Publication: Bee
Author: ANDYG
Quick Words:
sewers-Main-St-trees-WPCA
Full Text:
Sewer Drilling Alternative May Help Spare Main St Trees
B Y A NDREW G OROSKO
Water Pollution Control Authority (WPCA) members plan to conduct a public
informational session on the possibility of using innovative directional
drilling instead of conventional open-pit trenching to install sewers on the
east side of Main Street to protect the mature trees lining that side of the
thoroughfare.
Hemlock Directional Boring of Torrington, a company which uses the directional
drilling technique to install various types of public utilities, explained the
sewer installtion technique to WPCA members at a November 16 session.
After hearing the presentation, WPCA members decided to have the firm explain
the drilling technique to Main Street residents and the Borough Board of
Burgesses at an upcoming WPCA session. The WPCA is considering directional
drilling as one of several ways to install sewers on the east side of the
street.
In early 1993, WPCA members had expected that sewer lines would be installed
beneath Main Street. But after learning of the complexities of installing
sewers beneath the concrete-based, utility-laden street, the WPCA opted to
place the sewers in front of the houses there. The Burgesses, however,
objected to that placement, saying that sewer trenching there would damage
tree roots and cause the premature death of specimen trees. In response to
those concerns, WPCA members then decided to have sewers installed in
backyards.
Some Main Street residents, however, objected to that sewer route last summer,
resulting in WPCA members then opting not to place sewers in backyards.
In recent weeks, WPCA members have been considering using various construction
methods and locations for sewers in front of the houses. These include using
conventional open-pit trenching to: install sewers beneath Main Street;
beneath front yards; or beneath some combination of Main Street and
frontyards; and possibly using directional drilling to install sewers beneath
frontyards, where applicable.
In directional drilling, the bore holes into which sewer lines would be
inserted would lie below the root systems of trees to avoid damaging those
trees.
Mapping
Peter Grose, sewering project director for Fuss and O'Neill, Inc, the town's
consulting civil engineers, showed WPCA members some basic mapping which the
engineers had prepared indicating land segments on the east side of Main
Street where directional drilling for sewer line installtion might be used.
Kenneth Traub of Hemlock Directional Boring explained to WPCA members that
such drilling work involves the excavation of an entry pit and an exit pit
between which sewer pipe would be installed.
A pilot hole is drilled to start the process. The drill head contains a radio
transmitter to inform the drillers of the drill head's location and whether it
is on course. The pitch of the pipe section can be regulated but the piping's
lateral alignment may vary slightly.
After a pilot hole is drilled, the drillers use a reaming tool to widen the
bore hole. The hole which is drilled is approximately 20 percent larger in
diameter than the pipe being installed.
The drillers can drill through bedrock if it's encountered while the bore hole
is being made, Mr Traub said. As soon as the bore hole is created, sewer
piping is inserted into it, preventing the bore hole from collapsing, he said.
Mr Grose said a continuous length of polethylene plastic sewer piping would be
installed instead of individually-jointed sections of polyvinyl chloride pipe.
So far, polyvinyl chloride pipe has been used in the sewering project.
Polyethylene pipe is more flexible than polyvinyl chloride pipe and lends
itself better to bore hole installations.
Mr Traub explained that the directional drilling technique, which was
pioneered to extract the maximum amount of petroleum from oilfields, is used
in sewering work in areas where there are restrictions on excavation work to
prevent site damage.
Mr Grose said that natural gas and public water supply lines along Main Street
are buried much closer to the ground's surface than the sewer lines will be.
Alagna
WPCA Chairman Peter Alagna noted that while Main Street residents have
expressed concerns about the damage that sewer main installation could do to
tree roots along the street, the installation of sewer hookup lines between
sewer mains and houses is as critical, if not more so, than sewer main
installation.
Mr Grose observed there are more areas on the east side of Main Street between
Church Hill Road and Glover Avenue where directional drilling would be useful
than between Schoolhouse Hill Road and Church Hill Road.
WPCA member Alan Shepard said directional drilling appears to be the sewer
installtion technique to use, where applicable, to limit disruption to the
landscape in selected areas.
Mr Alagna said installing sewers via directional drilling appears to be less
costly than installing an equal length of sewers beneath Main Street.
Mr Grose suggested that the town pursue directional drilling, where
applicable, through a direct contract with a drilling firm instead of using a
drilling firm as a subcontractor. Any direct contract with a directional
drilling company would be subject to a competitive bidding process.
Directional drilling can be used to span points as far as 1,500 feet apart.
Besides using the technique to install some gravity-powered sewers, it can be
used for: force main sanitary sewers, storm sewers, cable television lines,
natural gas piping, elctrical cables, water pipes, fiber optic cables, and
telephone ducts and cables. The drilling technique is used at sites including
road crossings, rail crossings, street and parking lot lighting, residential
frontyards and backyards, rivers, wetlands, wooded areas, landmarks and
unsurmountable walls and fences. The drilling method's advantages include the
elimination or reduction of: shored trenching, restoration work, and negative
environmental effects.
Hemlock Directional Boring has installed some gravity-powered sewers in
Litchfield, Mr Traub said.
