Pipe Ramming in the Thin Air: BTrenchless Goes Large Diameter

un-off from the San Juan Mountain Range, through
town of Pagosa Springs and into the San Juan River.
Continuous flow through the culvert has made the
sinkhole a significant problem. The edge of the sinkhole
was only 25 feet from the north shoulder of west bound
US 160 and the portion of the existing culvert under
Highway 160 was so deteriorated that the Colorado
Dept. of Transportation (CDOT) determined that the
pipe needed to be replaced.
with repeated percussive blows. A cutting shoe is often
welded to the front of the lead casing to help reduce
friction and cut through the soil. Bentonite or polymer
lubrication can also be used to help reduce friction
during ramming operations. Ramming tools, in general,
are capable of installing 4- through 147-inch diameter
pipe and steel casings.
Ramming can be used for horizontal, vertical, and even
angled applications. It is often used under roads, like
the Pagosa project, and rail lines because it displaces
the soil without creating voids or slumps.
According to TT Technologies pipe ramming specialist
Rick Melvin that is a key benefit of pipe ramming. He
said, “Some installation methods can jeopardize the
integrity of roads or rail lines because they remove soil
from underneath to allow for the new pipe installation.
Pipe ramming’s ability to install various sized casings
without putting the topside structures in danger makes
it a very attractive option. Also pipe ramming works in
difficult soil conditions. Boulders and rocks, as large as
the casing itself, can be swallowed up as the casing
moves through the soil and can be removed after the
installation is complete.”
During the pipe ramming process, a pneumatic hammer is attached to
the rear of the casing or pipe.
Wellensiek said, “As the main artery between Pagosa
Springs and Durango, Colo, Highway160 is a very busy
two lane highway and CDOT did not want to impact
traffic by open cutting the highway to install a new
culvert. Open cutting was really never an option. We
would have had to perform that type of work late at
night when traffic levels were as low as possible.”
Ultimately, plans were drawn up to ram an 84-inch
diameter steel casing over the deteriorating 60-inch
CMP culvert and encase it. The existing CMP would
then be removed from the steel casing and a new 60-
inch RCP line installed. The BTrenchless crew would
face many challenges in order to make that happen.
Pipe Ramming 101
During the pipe ramming process, a pneumatic
hammer is attached to the rear of the casing or pipe.
The ramming tool, which consists of a piston within a
casing, drives the pipe or casing through the ground
An entire length of pipe can be installed at once or,
for longer runs, one section at a time can be installed.
In that case, the ramming tool is removed after each
section is in place and a new section is welded on to the
end of the newly installed section. The ramming tool is
connected to the new section and ramming continues.
Several methods can be used to remove spoil from the
casing including compressed air, water, an auguring
system or other types of earthmoving equipment.
High and Not So Dry
One of the first challenges Wellensiek and the
BTrenchless crew faced was elevation. Wellensiek said,
“Pagosa Springs sits at an elevation of 7,100 feet above
sea level. That has a direct impact on the capacity of
your air compressor system.”
Another difficult aspect of the project was maintaining
drainage flow through the existing culvert while
ramming. Wellensiek said, “At times there was really
low flow. Twice during this project we were completely
flooded out because of rain and there was no way to
handle that amount of water. So basically we stopped,
and got out of the way. There was nothing else we
could do.”
On the Job
BTrenchless crews excavated a ramming pit on the
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