Underground Construction - May 2022 - 33

REHABTECHNOLOGY
Manhole Rehab Project -
It's Part of the Plan
Proactive Approach Provides Long-Term Solutions for Idaho Sewer District
Randy Gonzalez
The city of Eagle, Idaho, situated on the banks of the Boise River
in the foothills of western Idaho, is home to nearly 30,000 people.
The area, like much of the greater Boise region, has experienced
significant population growth over the past 10-20 years
(including a 50-percent increase since 2010), and that trend is
expected to continue for years to come.
To keep up with the growth, the Eagle Sewer District - with
a service area of roughly 35 square miles - has a proactive approach
to ongoing maintenance. It includes a comprehensive
program to help ensure its infrastructure will serve existing customers,
as well as new customers well into the future.
Identifying problems
As part of the proactive maintenance plan, the district recognized
the need to address a series of manholes on a neighborhood
boulevard, that had experienced a significant amount of
degradation and corrosion.
These seven manholes, along an 1,800-foot stretch of North
Golden Crown Way, were part of a 24-inch trunk line that
hooked into a nearby lift station. Given the levels of sewage
running through this section of pipeline, the lift station was in
a constant state of cycling on and off, leading to a continuous
surging of sewage levels and bursts of turbulence in the stream.
The turbulence, in turn, caused heightened levels of hydrogen
sulfide (H₂S) gases to be released, relentlessly exposing the
vertical chimneys of the manhole structures to one of the primary
causes of corrosion in any sanitary sewer system.
Like much of the Eagle Sewer District infrastructure, the
manhole structures were built of concrete and put in place about
25 years ago. They had run the course of their anticipated useful
life, especially given the extreme exposure to H₂S during that
time. The district had two options to address the issue - replace
the manhole chimney structures or engage in a rehab project.
Options
Replacing manhole chimney structures is a hugely disruptive
and very costly project for any sewer district. Even though
A corroded manhole in need of rehabilitation.
UCONonline.com | MAY 2022
33
new polymer manholes were promising upwards of a 100-year
life, they were also as much as two-to-three times as expensive
per vertical foot as the cost of a rehabilitation solution. With
the significant improvements of products and materials now
available, and the improved lifespan of these solutions, the
Eagle Sewer District decided to rehab the seven manholes on
North Golden Crown Way.
One of its reliable vendors, Integrity Inspection Solutions
(IIS) of Caldwell, Idaho, won the bid for the project. Familiar
with working for the district and in the city of Eagle, the contractor
contacted city hall to arrange traffic control and began
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