Its construction was commenced in 1858, the puddle trench was probably
taken down to a depth of 40 ft. to 50 ft., a considerable amount of water
being encountered. This trench was 15 ft. to 20 ft. broad at the top, and
of course had to be crossed by the before mentioned line of pipes; and
although the trench was filled with puddle, and the gullet cut in the
rock already mentioned for carrying the pipes under the site of the dam
was "padded" with a layer of 12 in. of puddle, we can imagine that the
effect of the weight of the puddle wall and bank upon this line of pipes
would be very different at the point where they crossed the puddle trench
to what it would be where they were laid in the rock gullet and partially
protected from pressure by the sides of the latter. At the trench
crossing there would be a bed of puddle 50 ft. in thickness beneath the
pipe, in the gullet a bed of 1 ft. in thickness. So much as regards the
laying of the pipes.

The embankment had scarcely been completed when, on March 11, 1864, a
storm of rain came on and nearly filled it up to the by-wash, when the
bank began slowly to subside. The engineer was on the crest at the very
time, and remained until the water was running over his boots; he then
rushed down the other slope and was snatched out of the way as the bank
burst, and the whole body of water, about 250,000,000 gallons, rushed out
through the trench, carrying with it in the course of about twenty
minutes 92,000 cubic yards, or say one fourth of the total mass of
earthwork, causing the death of 250 human beings, not to mention cattle,
and destruction of factories, dwellings, and bridges, denuding the rock
of its surface soil, and, as it were, obliterating all the landmarks in
its course. The greatest depth of the bank from ground level to crest was
95 ft., the top width 12 ft., and the slopes, both on the up stream and
down stream sides, 2½ to 1, and the area of the reservoir 78 acres.