Underground Construction - July 2017 - 23

pipe ends be mitered at a 2:1 slope
from the factory. Once installed,
the ditch slope would be graded to
match and a concrete liner poured
for erosion protection."
LNVA considered different
types of pipe material for this
application. Although corrugated
metal and concrete are most commonly used materials for drainage
culverts, engineers reviewed the
life-cycle cost benefit of fiberglass
pipe. Leakage associated with corrugated and concrete drainage culverts are not generally of concern,
but over time they will cause erosion and corrosion. For this particular site where a canal, a drainage
ditch and a road all converged, the
type of pipe material raised concern for LNVA engineers.
"At this diameter, the pricing
was competitive with reinforced
concrete pipe," said Ard. "However, the benefits of fiberglass pipe
outweighed that of a reinforced

concrete pipe in terms of handling
the material and placement during
construction."
While the needed pipe would
measure only 600 linear feet of
48-inch diameter, generally an
amount falling below the dollar
value required for a formal bid process, LNVA nonetheless, publicly
advertised for bids to supply fiberglass reinforced pipe (FRP).

Installation
The LNVA ultimately chose Hobas
centrifugally cast, fiberglass reinforced, polymer mortar (CCFRPM)
pipe because, according to Ard,
"We have a good service history with Hobas and it is installed
in various other locations on our
system. We liked the fact that the
joints came in 20-foot lengths and
would be watertight, the pipe is
lightweight when compared to its
concrete counterparts, and Hobas

would factory miter the pipe ends
to our specifications and install a
headwall ring to be cast into a concrete headwall."
At Hobas, the pipe is easily
customizable for specialty jobs
via a custom-built water jet cutter. Drawings are created in 3D
mechanical CAD software and
transposed into the required code.
The water jet machine is then run
by a computer-controlled program
that produces perfectly cut pipes,
quickly and in a more environmentally friendly manner.
All of these benefits facilitated the LNVA crews being able to
install the pipe relatively easily
with no previous experience installing this type of pipe. LNVA
has several crews and operates a
fleet of its own heavy equipment
to perform day-to-day business.
This allowed LNVA to help control
costs by utilizing internal equip-

ment and manpower to construct
the project.
The installation of the three
160-foot runs in the drainage
ditch took four days, while installation of the three 40-foot runs in
the canal under the roadway was
completed in only one day. Once
the new pipe was installed, LNVA
crews re-graded the drainage ditch
slopes, and reconstructed the canal banks and rock road back to
their pre-existing grades. Because
repairs to the roadway and canal
system were performed in the agricultural off-season, the road was
closed for duration of construction, and no residences or local
traffic were affected.
FOR MORE INFORMATION:
Lower Neches Valley Authority
(409) 892-4011, lnva.dst.tx.us
Hobas Pipe USA, (800) 856-7473
(281) 821-2200, hobaspipe.com

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July 2017 Underground Construction

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Underground Construction - July 2017

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