During a street replacement project, the City of Annandale, Minnesota's
Public Works Department encountered several problems - seventeen
of them to be exact. Infiltration and Inflow caused by 17 leaking
manholes was delaying the project. The manholes had been leaking
for over 25 years, currently at a rate of 20-30 gallons of water
per minute. City officials needed a solution fast, so they called
on Key Contracting, Inc. of Fargo, North Dakota to rehabilitate
the leaking manholes.
Key Contracting Project Superintendent, Randy Berggren II, accepted
the job. Having used Prime-Flex Hydro Gel SX for several years
in many manhole rehabilitation projects, Berggren assured city
officials that this rehabilitation project could be done using
Prime Resins chemical grout. “I really like the Hydro Gel,”
Berggren said. “It’s a super easy material to work
with. We’ve used it for so many different repairs.”
Assuming that he would use Prime-Flex Hydro Gel SX for this repair,
Berggren called Prime Resins’ Adam Goldstone to place his
order. Upon hearing the nature of the repair, Goldstone advised
Berggren to use Prime-Flex 920 for this rehabilitation project
instead of Hydro Gel SX. “In this kind of situation, I’d
recommend Prime-Flex 920 because of its ability to shut down high-flow
leaks,” Goldstone said. “It also has a high expansion
rate, enabling it to fill any voids created by the high volume
of water flowing behind the walls of the manhole.”
The first thing Berggren did in order to begin the repair was
to verify what areas were leaking in each manhole. “The
manholes were all leaking at the joints,” he said. “We
needed to inject the joints first before we could skin the manholes.”
As Berggren drilled the first hole into a joint of a 29-foot deep
manhole, the force of the water leaking through the joint surprised
him. “It was a bad one down there,” he said. “The
water literally pushed the drill out of my hands and into the
wall on the other side.” Berggren persevered, however, and
injected the leaking joints of each manhole. The injection of
17 manholes required a total of about 50 gallons of Prime-Flex
920.
Berggren checked back a few days later and only had to treat
two low-volume remedial leaks with Hydro Gel SX before “skinning”
the manholes - a process where the inside of a manhole is sprayed
with a protective epoxy lining.
