Geosynthetics October/November 2020 - 25

were suspended in a soil matrix. They did
not damage the exhumed geotextile with
the specified installation procedures.

importance so that full-scale construction
is consistent with the methods and criteria
used for the test pad construction.
References

2020 update
More than 16 acres (6.5 ha) of the final
cover system have been constructed at this
site to date using these materials and procedures. No apparent issues have occurred
during the installation of the final cover
system. In addition, no issues with the
installed final cover system have been
identified since the end of construction.

Overall conclusions/
limitations

Balsamo, N. J.; Massey-Norton, J.; Klamut, J.; Queen,
T.; Straley, C.; and Lehner, M. (2019). "CCR landfill final
cover test pad." Proc., The World of Coal Ash Conference
2019, University of Kentucky, Center for Applied
Energy Research, Ash Library. http://www.flyash.
info/2019/072-paper.pdf (Accessed 5/29/2020).
Code of Federal Regulations (CFR). (2015). 40 CFR Part
257.102, "Criteria for conducting the closure or retrofit of
coal combustion residual (CCR) units," April 17 (EPA rule).
Geosynthetic Research Institute (GRI). (2012). GRI
Guide GS11, "Standard guide for constructing test
pads to assess protection materials intended to avoid
geomembrane puncture," Oct. 19. https://geosyntheticinstitute.org/grispecs/gs11.pdf (Accessed 5/29/2020). G

FIGURE 7 The sharp rock from beneath the ruptured geomembrane in Subarea F protruded more
than 1 inch (2.5 cm) (shown with 6-inch ruler)

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The construction of test pads in general accordance with the Geosynthetic
Research Institute (GRI) Guide GS11
may be used to demonstrate that typical
stone/protrusion size requirements may
be modified to allow for less conservative requirements for the construction of
final cover systems. For the soils and rock
types present at the subject site, subgrade
protrusions up to 1 inch (2.5 cm) (but not
sharp objects) were acceptable and rocks
up to 9 inches (22.9 cm) in the cover soils
were also acceptable. The use of test pads
to evaluate site-specific soils and liner
configuration can provide significant cost
savings by reducing screening and handpicking of rocks from subsoils and cover
soils. The method should be employed
on a case-by-case basis, as results may
vary depending on the subgrade material,
geosynthetic materials, soil type and borrow sources.
In addition, the potential for long-term
stress cracking may not be readily observed
during test pad construction/observation
but should be considered in final design
recommendations based on site-specific
conditions. Last, a robust construction
quality assurance and construction quality control program is of the utmost
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Geosynthetics October/November 2020

Table of Contents for the Digital Edition of Geosynthetics October/November 2020