Geosynthetics June/July 2023 - 22

Hugo, Colo., wastewater treatment system improvements
FIGURE 2 Viaflex fabrication facility. Photo
courtesy of Viaflex
FIGURE 3 Viaflex 8,000 pounds panel winder.
Photo courtesy of Viaflex
Contracting
In March 2021, the project accepted bids,
and HPM Contracting was awarded the
prime contract in April. HPM chose
Simbeck and Associates as the most
competitive installer. Submittals were
approved in May, and purchase orders
were released for materials to deliver in
July for an August 2 start date. However,
one year into the pandemic-and with
the global supply chain stressed-polypropylene
(also used to make N95
face masks and hospital gowns) was in
short supply. Liner manufacturers were
placed under restrictive allocations for
both resin and additives to make fPPR,
greatly reducing their production
capabilities. The selected and approved
manufacturer and fabricator could no
longer meet the scheduled delivery date
or price, nor could they guarantee delivery
of all materials. Multiple alternate
manufacturers and suppliers were sought,
but with shortages across the industry,
none were able to produce and fabricate
the 1.6 million square feet (148,645
m2) needed to meet the project schedule.
To make things worse, the specified
GEOMEMBRANE SELECTION
What is " RCG " ?
Reinforced Composite Geomembrane-also known as " RCPE " or
" Woven Coated " -Where the base reinforcement fabric is a woven
tape product (also called slit film or split film) polyethylene textile
which is then polyethylene coated on both sides. See GRI GM-30
What is " fPP-R " ?
Reinforced Flexible Polypropylene-Also known as " RPP " -Where
two layers of flexible polypropylene sheets are laminated over a 9x9
polyester weft scrim reinforcement. See GRI GM-18
What is " LLDPE-R " ?
Reinforced Linear Low Density Polyethylene-Also known as " RPE " -
Where two layers of low density polyethylene are laminated over a
9x9 polyester weft scrim reinforcement. See GRI GM-25
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Geosynthetics | June July 2023
alternate RCG material was rejected as
an option by the design team and the
Colorado Department of Public Health
and Environment (CDPHE).
Solution
After exhausting alternative suppliers
for the primary fPP-R (and RCG no
longer an option), Simbeck proposed
using a 45-mil (1.1-mm) reinforced linear
low-density polyethylene (LLDPE-R), a
product currently used for wastewater
containment in California, Wisconsin
and many other states. Similar to PVC
and polypropylene geomembranes, it
fabricates nicely into large panels that
are shipped to the site for installation.
With good carbon black additives, the
LLDPE-R withstands UV exposure and
offers 15-to-20-year material warranties.
Viaflex (formally Raven Industries), a
leading manufacturer and fabricator of
LLDPE-R, was able to commit to producing
for shipment the large quantity
of material in a short amount of time to
meet the project schedule. Viaflex worked
with Element Engineering LLC and the
CDPHE to demonstrate the suitability
of N45B for use at the Hugo project and
any future wastewater cells in Colorado.
Once CDPHE approved use of
LLDPE-R, revised submittals and panel
layouts were promptly approved by
Element. Fabrication of panels began
within a few days. The first of seven
truckloads arrived on-site just 14 days
after submittal approval-in time to
begin installation as scheduled. In all, 126
panels were prefabricated to the dimensions
shown in the table below.
45 MIL LLDPR-R PANEL SIZES
PANEL QUANTITY WIDTH
A
B
C
D
78
39
6
3
72
72
84
84
LENGTH WEIGHT
2646
2722
3087
3175
175
180
175
180
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