Difficult concrete repair problems often call for
creative repair solutions. In October 2003, The City of Ironton,
Ohio discovered a serious leak in the city’s clear well.
The city had used Prime Resins chemical grout products to stop
some minor leaks in concrete structures previously with good results
and called Phil Jameson, Territory Manager for Prime Resins for
advice. After learning the specifics of the job, Phil contacted
Pro Diving Services, Inc. (Akron, AL), a contractor specializing
in underwater concrete repairs.
The clear well in this project was built in 1912
and is 400’ long by 100’ wide by 15’ deep. The
city was losing between 300 and 400 gallons of water per minute
thru some crack systems that had been discovered during a previous
inspection. An attempt had been made to repair one major crack
system by driving rubber “O” ring stock into the crack.
This met with some initial success, but the repair eventually
failed and the water loss resumed at the previous rate. Traditional
repair methods were not an option as the tank is installed below
grade with 24 inches of earth over the top. The only access to
the cracks would be from inside the tank. As the cracks were in
the floor of the tank, the only options for repair were either
to drain the tank or to use divers to perform the repair from
the inside of the tank while it was in service. Draining the tank
was not an option as this is the only clear well with the capacity
to supply the city, so the town decided to use divers for the
repair.
Tom Long from Pro Diving Service made two trips
to Ironton to meet with the mayor, the city council, the city
engineer and the system manager to discuss the repair. The results
of these meetings were a negotiated contract between the city
and Pro Diving Service, Inc. in January of 2004.
The inspection of the inside of the tank did not
reveal any obvious leaks other than the main crack at the south
end of the tank. There were numerous small cracks and some construction
joints but these didn’t seem to be leaking. The major crack
to be repaired ran from one side of the tank to a construction
joint near the opposite side of the tank then picked up again
20 feet down the other side of the joint. The total crack length
was in excess of 120’ long and about ¼” wide.
One problem that complicated the repair was the
extremely cold water temperature (between 37-40º F). This
presented two problems, the most obvious being loss of body heat
for the diver. To combat the cold, a hot water diving system circulated
hot water thru the divers suit. The water supply for the hot water
system came from the water in the tank. For sanitation purposes
the diver and all equipment were sprayed with a chlorine solution
prior to entering the tank. The other problem was that most epoxies
or resins would not react and cure below 40º F.
The initial plan was to clean the crack and then
apply a trowel grade epoxy. The crack would then be injected with
Prime Resins Prime-Flex 900LVSF. The project
hit a snag when the Pro Diving crew found that the trowel epoxy
specified for the project would not react below 40º F. At
this point, Tom Long decided to use only the Prime Resins product
as he had been assured by Prime Resins technical support that
the Prime-Flex 900LVSF would react in this extreme environment.
Following is the procedure used for the
repair:
- The crack system was cleaned with a 3,500 psi pressure washer.
- Holes were drilled in the concrete with pneumatic drills for
the installation of injection ports. In some cases, a 3/8 inch
hole was drilled straight into the crack, in other cases, a ½
inch hole was drilled from the side of the crack at an angle to
intersect the crack within the wall. The spacing of these holes
was approximately every 12 inches. The holes were then flushed
with either hot water or air. Both methods worked equally well.
- Next, injection ports were installed in the drilled holes. Prime
Resins “Bang-in” ports were installed in the 3/8-inch
holes and mechanical packers were installed in the ½ inch
holes.
- The ports were pumped starting on one side of the tank proceeding
across the tank to the other side. This worked very well in all
but (3) six-foot sections where the water flow was too great.
In theses three areas, the diver packed the crack with oil-free
oakum then applied Prime Resins 900LVSF over the oakum. After
the activated oakum cured, the ports in that area were pumped
again.
- During the final inspection, any areas where the resins had
not expanded out of the crack were located and the diver applied
additional 900 LVSF.
The final inspection revealed that the entire crack
was covered with cured resin and there were no detectable leaks.
Some additional steps were used to aid in
application:
- The resin was kept in a cooler of 100º F circulated water.
A long section of the pump hose was also coiled in the cooler.
- The diver had difficulty installing the zerk fittings into the
injection ports while wearing heavy gloves. To overcome the problem,
the fittings were installed before sending them to the diver.
The diver then placed a deep well socket over the fitting to place
the port. The metal packers were also expanded slightly before
sending them to the diver so that the diver had to lightly tap
them in. This made tightening the packers easier for the diver.
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