Sewer Replacement in British Columbia: PW Trenchless Provides Pipe Bursting Proficiency
50 year old, RCP sewer main was subject to surcharge
during wet conditions and suffered from deterioration
and massive tree root intrusion.
With heavy traffic
flow and anticipated growth and development, the Corporation
of Delta, British Colombia began upgrade work two years
ago to its River Road corridor. The corridor serves as a
main trucking artery and sees heavy amounts of traffic.
Upgrades to the corridor include the construction of new
sidewalks, traffic flow measures at several intersections,
increasing lane widths to safely accommodate bicycle traffic,
as well as general road repair and rebuilding.
In addition to surface improvements, the project includes
the replacement of an aging sanitary sewer system. The location
of the sewer main, the heavy traffic flow and existing utilities
precluded the use of conventional open cut methods. A trenchless
solution was needed. PW Trenchless, Surrey, BC was contracted
to provided that solution, trenchless pipe bursting with
the Grundocrack pneumatic pipe bursting system from TT Technologies,
PW Trenchless President David OSullivan said, "This
project posed many challenges. Not only did we have to
contend with underground utilities, a healthy upsize and
traffic control, the project falls within an area designated
as archeologically sensitive. This meant everything would
be under a great deal of scrutiny."
Trenchless crews began work with a 14-inch diameter
straight barrel reversible Grundocrack Koloss pipe
bursting tool. They eventually switched to rear expander
configured Koloss to achieve higher rates of production.
Native people of Canada or First Nations people actively
promote environmental awareness and work to protect historical
sites and even sacred areas throughout Canada. Because of
the location of the River Road project, a registered archeologist
as well as a local First Nations representative were required
to supervise all excavations on the project.
OSullivan said, "Working with the First Nations
people required that all of the excavation we did for launch
and exit pits be raked and sifted for artifacts. If they
saw something of interest while we were digging, we would
remove the soil and take it to another location where it
could be examined by the archeologist and First Nations
According to OSullivan while artifacts like arrowheads
were discovered on their portion of the project, human remains
were discovered during the road construction portion of
the project. He said, "Road construction crews discovered
two sets of human remains in a burial site. This caused
work to stop as the design of the project was revised to
allow the remains to be left undisturbed. Those instances
are taken quite seriously up here.
"As it relates to pipe bursting and trenchless construction
however, I think its something that engineers and
owners could take to the Native peoples and show them how
we propose to replace the sewer line. Show them the methodology
we intend to use in order to mitigate any damage to sensitive
sites. Its very positive and worked well for the
River Road Project."
along the River Road corridor was extremely tight,
making trenchless pipe bursting an ideal choice for
the project. The PW Trenchless crews worked behind
concrete barriers and moved the road to the shoulder
to maintain traffic flow.
sewer work, in terms of the total scope of the project,
is taking place about one year before the road improvements
are made. OSullivan explained, "The road improvement
portion of the project is proceeding in sections. The first
two sections of the road did not have any sewer work underneath
it. The section of bursting we recently completed is now
undergoing roadwork. Then, the sewer work we hope to do
this year will undergo roadwork next year. Its being
done that way to manage traffic flow and to allow any excavation
that we do to settle before road improvements are done."
The existing 375 mm (15-in.) diameter reinforced concrete
(RCP) sewer was installed over 50 years ago and handles
approximately 50 percent of the flow from the northern half
of the city (approximately 25,000 residents). Subject to
surcharging during wet conditions, the trunk was suffering
from numerous areas of structural deterioration as well
as massive tree root intrusion.
to TT Technologies Pipe Bursting Specialist Mike Schwager,
several factors made pipe bursting an ideal choice for
this project. He said, "This is really a project
where all the benefits of pipe bursting are evident.
Growth in the area required the diameter of the main
to be increased. Pipe bursting is the only trenchless
method of replacement that allows for the upsizing of
the original line. There were also numerous sub-utilities
in the area, so the fact the new pipe would follow the
path of old pipe was important, as was the reduction
in excavation from the trenchless method. That also came
into play when dealing with the heavy traffic in the
area. Not to mention the archeological factors."
rear expander configured Grundocrack Koloss was used
to replace the existing 375-mm (15-in.) diameter RCP
sewer with 450-mm (18-in.) High-Density Polyethylene
pipe (HDPE). Launch and exits pits were deep, average
between 3 and 5 m (10 and 15 ft.).
the benefits of bursting apparent, OSullivan proceeded to plan
out the project. He said, "We needed to replace approximately
800 m (2,600 ft.) of trunk main and perform some lateral
work as well. We divided the bursting into eight different
sections. Bursting lengths varied from 60 to 120 m (190
to 390 ft.) each. The sections would be upsized to 450
mm (18 in.) with one section upsized to 508 mm (20 in.).
We had everything ready to go and were awaiting the arrival
of Mike Schwager from TT Technologies. It was the second
week of September."
On September 11, 2001, Schwager was preparing to make the
trip north, across the US/Canadian border to provide on-site
technical support for the bursting work about to begin in
Delta. After the tragic events of that morning, all US borders
were closed and the trip never took place.
OSullivan said, "This was the largest diameter
bursting we had ever attempted. We anticipated the need
for technical assistance. Looking back, I wore out the
phone with Mr. Schwager about different aspects of the
project. It was very helpful.
On the Job
began on September 13th. The crew faced tight working conditions
along the River Road corridor, along with launch and exits
pits that averaged 3 to 5 m (10 to 15 ft.) deep. Traffic,
however, was the main concern. OSullivan said, "Traffic
control was easily the most challenging part of the project.
Traffic was horrendous and the manholes were located right
along the white line on edge of the road. We actually moved
the road over about a meter and a half to run traffic on
the shoulder. Then we put up concrete barricades to work
behind. It was very tight."
archeologically sensitive nature of the area required
a registered archeologist and a local First Nations'
(Native people of Canada) representative to be on
hand during all excavation work. Spoil from launch
and exit pits had to be raked and sifted for artifacts.
The PW Trenchless
crew completed the first three runs with a straight barrel
reversible Grundocrack Koloss, but the manholes were too
small to facilitate easy tool removal. The switch was made
to a rear expander configuration for the remaining bursts.
Schwager said, "When we began bursting in the late
1970s and early 1980s, straight barrel tools with front
expanders were commonly used. They can be removed through
manholes or reversed out through the newly installed pipe.
Their effectiveness, however, is somewhat limited by soil
conditions, length of run and host pipe material.
The rear expander configuration provides several key advantages.
First, it allows the use of bentonite in conditions that
warrant it. Second, the rear expander tool configuration
means that a majority of the tool itself is actually in
the pipe. This increases bursting power and assists in
maintaining line and grade."
Bursting with the rear expander configured tool continued
without incident. The 350-mm (14-in.) diameter Koloss was
equipped with a 550-mm (22-in.) diameter rear expander.
The PW Trenchless crew used a 10-ton constant tension Grundowinch
to guide the tool through the host pipe. Bursting times
ranged between 2 and 3 hours for each segment with soil
conditions ranging from running sand to densely packed glacial
runs ranged between 60 and 120 m (190 and 390 ft.).
Soil conditions varied greatly throughout the eight
bursting runs. PW Trenchless crews used a 10-ton constant
tension Grundowinch to guide the bursting tool through
the host pipe.
River Road sewer project marked a new level of pipe bursting
capability for a contractor that already has a substantial
amount of bursting experience. It was their longest bursting
project to date as well as the largest diameter project.
For OSullivan its a progression. He said, "We
started bursting 1998 with a 101-mm (4-in.) diameter tool
for doing laterals and weve worked our way up from
there. We went to a 150-mm (6-in.) tool, then a 200-mm (8-in.)
tool. Now we're working with the 350-mm (14-in.) Koloss
tool with substantial upsizes like the River Road project.
Were definitely growing with the technology."
While the River Road project is a highlight for PW Trenchless
it certainly wont be their last. According to OSullivan,
the company has several bursting projects lined up that
will exceed the River Road project in terms of scope and
complexity. OSullivan said he welcomes the challenge.
River Road Sewer project was one part of a large-scale
corridor improvement program undertaken by the Corporation
of Delta, BC In addition to replacing the concrete
sewer main, road repair, sidewalk improvements and
safety measures were part of the overall project.
Note: pneumatic Grundocrack pipe bursting tool with
HDPE pipe string.
Trenchless Technology International,