Geosynthetics February/March 2022 - 28

Geosynthetics for solar farm development
260 MW solar facility. The geotechnical
report indicated soils generally consisting
of medium to hard clays, including
expansive soils that can experience large
volume changes. Figure 9 displays the
soft soil conditions that the project team
was faced with. Initially the project team
executed lime stabilization over the soft
areas. However, the stabilized layer began
to degrade almost immediately. Based
on the design criteria in the geotechnical
report, and subgrade strength verified
independently on-site using DCP testing
(on-site DCP reported CBR values
between 1.5% and 3%), several stabilization
options with high-strength geosynthetics
were considered.
The recommended option included
6-8 inches (152-203 mm) of flexible base
over a high-strength woven geotextile.
TenCate Mirafi RS280i was used, which
has the performance and index properties
shown in Table 2.
Figure 10 exhibits a stabilized roadFIGURE
8 Environmental savings
with geotextiles
PROJECT HIGHLIGHTS
IMPACT SOLAR SITE
OWNER
British Petroleum (BP)
LOCATION
Lamar County, Texas
CONTRACTOR
Swinerton Renewable Energy
ENGINEER
Terracon
GEOSYNTHETICS PRODUCT
Mirafi RS280i geotextile
GEOSYNTHETICS MANUFACTURER
TenCate Geosynthetics Americas
28
Geosynthetics | February March 2022
In addition to providing monetary
cost savings, this solution reduced the
environmental footprint by preserving
natural resources and decreasing CO2
emissions from hauling, transporting and
placing materials. Assuming 15 miles (24
km) one-way to a rock quarry, Figure 8
displays the environmental advantages
this solution provided, including a reduction
of the number of estimated trucks for
hauled materials from 382 trucks to 167
trucks, with a corresponding reduction
in CO2 emissions from 44,100 pounds
(20,000 kg) to 19,400 pounds (8,800 kg).
Case study: Impact Solar,
Lamar County, Texas
Located 120 miles (193 km) northeast
of Dallas, the Impact Solar project is a
way with the high-strength geotextile
and 6 inches (152 mm) of aggregate on
this project. Note the excessive rutting
on the adjacent unreinforced section.
Each road section constructed with this
option experienced exceptional performance
and minimal surface rutting, and
provided a significant cost savings for
this project.
Initially the subgrade stabilization
plan included 12 inches (305 mm) of
worked subgrade with 6 inches (152 mm)
of lime stabilization and 6 inches (152
mm) of Flex Base. The lime stabilization
was budgeted at $32 per square yard.
Using the high-strength geotextile above
with up to 8 inches (203 mm) of aggregate
was budgeted at $7 per square yard
(including installation). For the 13 miles
(21 km) of 17 foot (5.2 m) wide roads
on the project, this provided a savings
of more than $3.2 million in subgrade
material. The solution was quick to install
and provided the required stabilization
Geosynthetics February/March 2022

Table of Contents for the Digital Edition of Geosynthetics February/March 2022
