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Badly deteriorated
sewers in Jacksonville are again being renewed using HOBAS
centrifugal cast fiberglass reinforced polymer mortar pipes (CCFRPM).
This slipline installation on the 5th Street project utilized over
11,000 feet of 36", 42" and 48" pipes with low
profile bell-spigot joints to rehabilitate the host 42",
48" and 54" (respectively) RCP lines.
Demanding Conditions
Many demanding conditions limited options for
the City and consultant, Reynolds, Smith and Hills. For several
reasons, no routine by-pass pumping of flow was allowed.
Therefore, since the lining had to be installed "live",
only segmented sliplining could be used. Due to the poor condition
of the existing interceptor and cover depths up to 20 feet,
structural reinforcement was needed and only corrosion resistant
pipes would suffice. Additionally, a leak-free system and
excellent hydraulic characteristics were important in order to
maintain the flow capacity after the 6" diameter reduction.
Finally, to safely withstand annulus grouting pressures, a minimum
pipe stiffness of 36 psi was required for all liner pipes. Because
of these criteria, only FRP, CCFRPM and HDPE pipes were specified.
HOBAS Superior
Installer, Westra Construction of Palmetto,
chose HOBAS pipes for a variety of reasons. The solid wall
construction minimized liner flotation during insertion, which
reduced contact pressure with the very fragile host pipe crown.
This was critical on this project to avoid cave-ins (some occurred
anyway). The solid wall feature is also more rugged and permits
much higher push loads, if needed, thereby improving reliability.
Several specials, routinely available from HOBAS, including
elbows, a reducer and closure couplings were needed to complete
the lining. Westra has installed HOBAS pipes for over ten years
and they know its value, particularly in difficult conditions.
Repeat Success
PI’s in the existing lines limited push
distances to 2000 feet maximum. The short insertion distances and
intermediate depths, allowed Westra to use their backhoe to push
the pipes, saving both time and money. With nearly all of the
pipes placed and no performance deficiencies encountered, Westra
will soon begin annulus grouting. As in the past, they plan a
multi-lift placement of a non-foam grout to avoid floating the
liner pipes. A final interior video to confirm the installation
soundness will conclude another successful project. HOBAS
installations in Jacksonville now exceed five miles of pipes
ranging from 36" to 72" diameter.
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