APPENDIX A: RECOMMENDED MATERIALS FOR CONSTRUCTING A MESL
branes or plastic sheets sold in hardware stores
are not of acceptable quality. If the subgrade soil
Construction of a MESL with the following
has sharp rocks, a slightly thicker membrane,
materials requires care and good planning. Plac-
such as Reef's Ply X-150, should be used.
ing the membranes should not be attempted in
windy weather because they can act as large sails
and become extremely difficult or even impossi-
The top membrane should be at least 0.51 mm
ble to hold down.
(20 mil) thick, such as Raven's RUFCO 2010 or
The top layer of the fill soil should not contain
Reef's Ply X-210.
any sharp soil particles or rocks that can punc-
ture the membrane from below. All seams should
be placed so water drains away from them and
Three layers of a 271-g/m2 (8-oz/yd2) non-
does not pond on or near them. Extreme care
woven geotextile should be used. If the gravel is
must be taken when placing the gravel for the
extremely angular, if the traffic volume will be
very high, or if the gravel cover is less than
Traffic should be controlled on the sections.
152 mm (6 in.), four layers of geotextile should
No hard starting, stopping, or turning should be
be used. If the gravel is rounded and the design
life is short, it may be possible to use only two
The bottom membrane should be at least 0.152
A heavy tape that is forgiving and that works
mm (6 mil) thick. A quality membrane (such as
well in windy conditions (for example, Fab tape)
Raven's RUFCO 610) should be used. The mem-
is easiest to work with.