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27.
of fifteen feet above the bottom of thei reservoir, this height being deemed sufficient to clear any deposits of silt that many accumulate in the reservoir bed. The Culvert. should have its foundation
on the solid rock, which must be opened out and if necessary roughly tabled, and all its fissures eleaned and closed with liquid cement.
Tot -avert the possibility of leakage along the
point between the rock bed and concrete foundation, it will be desirable at. intervals of every six or eight feet to eut- small rectangular cross trenches into the rock floor along the uvais of the Culvert, us to form offects in the under bed of the Concrete, which will greatly tend to arrest.
seam or
any creep of water.
When the concrete bed
has been laid it must be covered with a two inch layer of rich cement mortar to
a bed for the ashlar flooring
form
of the Culvert. The latter will be
or invert
four
foot opening with vertical sides of Granite ashlar and a semicircular arch of three rings of Canton red bricks
The outer
surface of the arch should receive ap layer of Cement Concrete to receive the
superincumbent rubble Masonry of the
dam.
The Dry Subway ov
or Outlet Culvert. This Subway leading from the dry compartment of the valve well out into the Gauge basin will be similar design and construction to the inlet Culvert just described the only difference being