Supposing the former idea prevails,
then it can be of little moment as to how or of what material the bank on
either side is made up--whether of earth or stone--placed in thin layers
or tipped in banks of 3 ft. or 4 ft. high; but the opinion of the
majority of engineers seems to be in favor of making the banks act not
merely as buttresses to the puddle wall, and throwing the whole onus, as
it may be termed, of stanchness upon that, but also sharing the
responsibility and lessening the chances of rupture thereby. But to
insure this, the material must be of the very best description for the
purpose. Stones, if allowed at all--and in the author's opinion they
should not be--should be small, few, and far between. Let those that are
sifted out be thrown into the tail of the down stream slope. They will do
no harm there, but the layers of earth must not approach 3 ft. in
thickness nor 1 ft.--the maximum should be six in., and this applies also
to the puddle. Let the soil be brought on by say one-horse carts, spread
in six inch layers, and well watered. The traffic of the carts will
consolidate it, and in places where carts cannot traverse it should be
punned. In the Parvy reservoir dam a roller was employed for this
purpose. It comprised a small lorry body holding about a yard and a half
of stone, with two axles, on each of which was keyed a row of five or six
wheels.
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