Underground Construction - July 2017 - 22

By Liz Moucka

LNVA Repairs
Jones Crossing
at the Devers Canal

T

The Lower Neches Valley Authority (LNVA) is one of the 23 River
Authorities created by the state
of Texas to develop and manage
the waters of the state. The LNVA
is responsible for fresh water
management in far southeastern
Texas in the entirety of Jefferson,
Hardin and Tyler Counties, and
portions of Liberty and Chambers
Counties. The watersheds of the
Neches River and its tributaries
occupy an area of approximately 10,000 square miles. The area
receives generous amounts of
rainfall, producing stream flows
in the Neches and its tributaries
of around 4,323,000 acre-feet of
water a year at Port Arthur, TX,
where it empties into Sabine Lake
and, ultimately, into the Gulf of
Mexico.
Although water in the Devers
Canal System is pulled from the
Trinity River, the LNVA acquired
the Devers Canal System in 2008.
Known as the Jones Crossing, the site of a potential breach
was approximately 21 canal miles
downstream from LVNA's Devers
first pump station at the Trinity
River. At this particular location
about 20 miles southwest of Beaumont, an aged drainage system
was piped under the Devers Canal
via three parallel 48-inch reinforced concrete pipes. The canal,
in turn, was piped directly under a
farm access road also via three parallel 48-inch reinforced concrete

22

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pipes. All three features converged
at various angles at the Jones
Crossing point.
"We were experiencing problems with the existing reinforced
concrete pipe joints separating
and allowing canal water to leak
into the ditch," said Ryan Ard,
P.E., LNVA engineering manager. "LNVA made several repairs
over time to patch any leaks that
appeared. Over the years, erosion
and weathering had deteriorated
the original timber headwalls in
the drainage ditch. This ongoing
erosion, exacerbated by the heavy
rains in early 2015 and again in
early 2016, eventually infiltrated
and undermined the headwalls,
allowing the banks of the drainage
ditch to creep toward the canal.
Had we allowed the problem to
persist, the canal banks would
have ultimately been breached by
erosion, thereby allowing canal water to spill into the drainage ditch
below."
As originally planned, this project would be designed by LNVA
staff and put out for public bid by
a general contractor in mid to late
2017. Given the circumstances and
the need for urgency, and because
LNVA's canal system is not in operation over the winter months
(Oct. 31 through March 15) due
to the agricultural cycle, LNVA decided to take on the construction
project internally.

Above: Hobas pipe was chosen due to its life cycle cost benefit. It was imperative
that the pipe remain leak-free due to potential erosion of a sensitive area. Below:
Hobas supplied 600 feet of 48-inch pipe to the Lower Neches Valley Authority. LNVA
crews installed the pipe relatively easily with no previous experience installing this
type of pipe.

The approach
The scope of the repair would include excavating and removing the
existing drainage ditch and canal
crossings which both included
three runs of 48-inch reinforced
concrete pipe. The pipe in the ditch
measured approximately 160 feet
and the pipe in the canal was approximately 40 feet long. The total
depth of the drainage ditch was
approximately 12 feet.
LNVA engineers analyzed several alternative repair designs, but
ultimately decided the best option
was to rebuild the crossing in its
original configuration. The layout
was somewhat complicated by the
fact that a private road crosses
both the drainage ditch and the
canal at this location.
Because the hydraulics of both

the canal and the drainage culverts
had been performing satisfactorily
for many years, and also because
of vertical space limitations, LNVA
decided to use the same size pipe
for the reconstruction. The driving
consideration was trying to maximize the depth of the canal while
maintaining the existing flow line
of the drainage ditch.
The original headwalls in the
drainage ditch were constructed
of vertical timbers. "We wanted
to go back with a hard armored
headwall, such as concrete or articulated block," explained Ard.
"We determined a vertical headwall in the drainage ditch would
be more costly to construct and
maintain over the years compared
to a sloped concrete liner. Based
on this decision, we requested the
Underground Construction July 2017
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Underground Construction - July 2017

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