Figure 25. Test section after 30
passes with a 5-ton dump truck.
OBSERVATIONS
made excavating the soil and providing smooth
Following are observations that were made
surfaces difficult. Not providing a smooth bottom
surface will increase the likelihood of the mem-
during the project. Many minor problems com-
brane being punctured.
pounded one another. Some of these could be
Membranes. The membranes performed well
solved by using different equipment or more
overall with a few minor difficulties. They quickly
skilled operators. Other problems, including the
became covered with a fine film of dust that had to
weather, the type of native soil available, and
be removed before the tape was applied. Water or
membrane folds, are difficult or impossible to
rubbing alcohol effectively removed the dust. It
control in the field.
was important to replace the wiping towel as soon
as it became dirty.
MESL demonstration observations
The membranes come folded from the manufac-
These observations are from the construction
turer. As the thickness increases, the folds take
of the MESL and the puncture test. Both had
longer to flatten. This would also be affected by
numerous problems that primarily involved
temperature, with colder temperatures increasing
equipment availability and operation.
the time. The membranes also were factory-
seamed to form larger sheets. Sealing across the
MESL test
seams could be difficult and a source of potential
The MESL test was much more time-consum-
leaks.
ing than planned. It was originally scheduled to
Placing membranes. The membranes were easy
be finished in three to four days and took nine
to place when there was no wind, but because
days. Most of the delays were due to the lack of
they are very large, a strong wind can make it diffi-
equipment and operators.
cult or impossible to place them (Fig. 26). The
Weather. The weather is critical to the success
membranes also needed to be held down if the
of the project. Construction cannot take place
wind increased after they were placed.
during rainy periods. Rain could also turn the
Several troops were required to place the mem-
excavated, unfinished MESL into a large pool.
branes. As the size increased, the number of troops
Wind is also a factor. It can make placing the
required also increased. Four to six troops worked
membranes difficult. If the area is very dry, the
well for the membranes (10.7 36.6 m [35 ft 120
construction process can generate a large amount
ft]) used in this project.
of dust, making the membranes dusty.
Tape. The tapes worked very well. Fab tape was
Excavation of native soil. Excavating the
preferred because it was easier to use. It is more
native soil can be done with a variety of equip-
robust, has more tension strength, is not blown
ment. During the demonstration project the
around by the wind as easily, and can be adjusted
troops were limited to pans and a D-7 dozer. This
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