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Fort Collins Utilities Reservoir Improvements
In
1995, the City of Fort Collins, Colorado contracted with Bates Engineering
to review all of their system reservoirs to determine necessary
improvements. The reservoir system at that time consisted of two concrete
15 MG "hopper bottom" reservoirs at the Water Treatment Facility
constructed in the 1960's and a two-cell rectangular concrete 4 MG
reservoir near the Colorado State University stadium constructed in the
1980's. Bates Engineering made observations both from a raft and the dry
reservoirs and provided the City with reports including repair and
improvement recommendations. Bates prepared bid documents to carry out
these recommendations.
Completed
access house at the
City of Fort Collins 4 MG Reservoir.
In 1996, the City approached Lillard and Clark
construction about providing construction services in the City's
modified design/build process for $600,000. Work was carried out
from 1996 to 1998. Work included:
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Site access improvements
including regarding, placement of base course and new concrete
stairways
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Doubling the size of one
access house to provide a disinfection clean room
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Providing new doors,
recoating of steel surfaces, halogen lighting and a fall
protection system in all access houses
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Valve vault improvements
including an enlarged hatch, lighting and heating
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Installing 10 new 5'x 8'
aluminum hatches on concrete risers through the roofs for
light, ventilation and access
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Installing one-half mile of
4-inch PVC washdown piping to facilitate annual cleaning of
the reservoirs
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Various concrete repairs
including polyurethane injection of leaking joints and sealant
replacement. Due to the difficult floor geometry, roof repairs
were made by the contractor from a floating platform inside
the tank
At this time, Bates Engineering
was also asked to make a recommendation for coating the 4 MG
Reservoir roof which has experienced significant structural
cracking.
Bates researched 17 coating products
for the City and evaluated each product based on nine weighted
criteria which were believed to be important to the success of the
project including constructibility, serviceability, durability and
cost. Three of these products were selected for
further evaluation. Bates arranged with three coating contractors
to apply test sections to the reservoir roof. After one year in
place, Bates evaluated the coatings and made a final coating
selection. In 2000, Bates prepared bid documents to complete this
work.
In 1997
the City asked Bates Engineering to perform a
hydraulic model study. The study conducted at the Bureau of
Reclamation Hydraulics Laboratories in Denver developed efficient
baffle systems to increase contact time in the two
short-circuiting 15 MG Reservoirs. Bates designed Hypalon baffles
that were installed by Lillard and Clark Construction in 1998. The
City's subsequent fluoride tracer tests verified the efficacy of
the baffle systems. This study was included in an AWWA Research
Foundation study report and won the American Consulting Engineers
Council of Colorado
Excellence Award for Studies in 2000.
Baffle details in
the City of Fort Collins, Colorado 15 MG Reservoirs
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City of Longmont 6 MG Steel Reservoir
In 1997 the
City of Longmont, Colorado asked Bates Engineering to evaluate two of
their reservoirs including their 6 MG steel reservoir. Bates performed
both a floating and a dry review. Bates Engineering contracted with a
nondestructive testing service to evaluate steel thickness in the
floor and roof and a tank testing service to perform magnetic flux
testing of the floor. Bates had the interior and exterior coatings
tested for lead, chromium and cadmium. Significant levels of lead were
found both in the interior and exterior coating systems. A complete
report with photographs was presented to the City making repair and
improvement recommendations.
Rafter replacement
in the City of Longmont 6 MG Tank
Bates
prepared bid documents for the work which included the following items:
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Site grading and access improvements
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Replacement of three 36-inch butterfly valves in the valve vault
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Recoating the reservoir including removal or overcoating of
lead-based paints
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Removing and replacing 30 corroded roof rafters
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Lowering the height of the overflow piping to avoid wetting of
the roof rafters
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Providing safety rails around the inlet pipe and floor drain
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Designing a new caged exterior ladder with locking cover and
landing
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Providing two new 5' x 8' roof access hatches with safety
railing
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Adding a new 30-inch-diameter manhole including a concrete
washdown pad outside the tank and reinforcing the steel floor
inside the tank to protect from traffic damage
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Verifying the results of the magnetic flux testing by cutting
and repairing coupons from the tank floor plate
Bates
provided regular field observation during the construction and
provided construction administration services to the City.
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