The natural navigation of the Ottawa River from the head of the Island
of Montreal to Ottawa City--a distance of nearly a hundred miles--is
interrupted between the villages of Carillon and Grenville which are
thirteen miles apart by three rapids, known as the Carillon, Chûte à
Blondeau, and Longue Sault Rapids, which are in that order from east to
west. The Carillon Rapid is two miles long and has, or had, a fall of 10
feet the Chûte à Blondeau a quarter of a mile with a fall of 4 feet and
the Longue Sault six miles and a fall of 46 feet. Between the Carillon
and Chûte à Blondeau there is or was a slack water reach of three and a
half miles, and between the latter and the foot of the Longue Sault a
similar reach of one and a quarter miles.
Small canals limited in capacity to the smaller locks on them which were
only 109 feet long 19 feet wide, and 5 to 6 feet of water on the sills,
were built by the Imperial Government as a military work around each of
the rapids. They were begun in 1819 and completed about 1832. They were
transferred to the Canadian Government in 1856. They are built on the
north shore of the river, and each canal is about the length of the
rapid it surmounts.
[Illustration: THE GREAT DAM ACROSS THE OTTAWA RIVER, AT CARILLON.]
The Grenville Canal (around the Longue Sault) with seven locks, and the
Chûte à Blondeau with one lock, are fed directly from Ottawa. But with
the Carillon that method was not followed as the nature of the banks
there would have in doing so, entailed an immense amount of rock
excavation--a serious matter in those days. The difficulty was overcome
by locking up at the upper or western end 13 feet and down 23 at lower
end, supplying the summit by a 'feeder from a small stream called the
North River, which empties into the Ottawa three or four miles below
Carillon, but is close to the main river opposite the canal.
In 1870-71 the Government of Canada determined to enlarge these canals
to admit of the passage of boats requiring locks 200 feet long, 45 feet
wide, and not less than 9 feet of water on the sills at the lowest
water. In the case of the Grenville Canal this was and is being done by
widening and deepening the old channel and building new locks along
side of the old ones. But to do that with the Carillon was found to be
inexpedient. The rapidly increasing traffic required more water than the
North River could supply in any case, and the clearing up of the country
to the north had materially reduced its waters in summer and fall, when
most needed. To deepen the old canal so as to enable it to take its
supply from the Ottawa would have caused the excavation of at least
1,250,000 cubic yards of rock, besides necessitating the enlargement of
the Chûte à Blondeau also.
It was therefore decided to adopt a modification of the plan proposed
by Mr. T.C. Clarke, of the present firm of Clarke Reeves & Co, several
years before when he made the preliminary surveys for the then proposed
"Ottawa Ship Canal," namely to build a dam across the river in the
Carillon Rapid but of a sufficient height to drown out the Chûte à
Blondeau, and also to give the required depth of water there.
During the summer and fall of 1872 the writer made the necessary surveys
of the river with that end in view. By gauging the river carefully in
high and low water, and making use of the records which had been kept by
the lock masters for twenty years back, it was found that the flow of
the river was in extreme low water 26,000 cubic feet per second, and
in highest water 190,000 cubic feet per second, in average years about
30,000 and 150,000 cubic feet respectively. The average flow in each
year would be nearly a mean between those quantities, namely, about
90,000 cubic feet per second. It was decided to locate the dam where it
is now built, namely, about the center of Carillon Rapid, and a mile
above the village of that name and to make it of a height sufficient to
raise the reach between the head of Carillon and Chûte à Blondeau about
six feet, and that above the latter two feet in ordinary water. At the
site chosen the river is 1,800 feet wide, the bed is solid limestone,
and more level or flat than is generally found in such places--the banks
high enough and also composed of limestone. It was also determined to
build a slide for the passage of timber near the south shore (see map),
and to locate the new canal on the north side.
Contracts for the whole works were given out in the spring of 1873, but
as the water remained high all the summer of that year very little could
be done in it at the dam. In 1874 a large portion of the foundation,
especially in the shallow water, was put in. 1875 and 1876 proved
unfavorable and not much could be done, when the works were stopped.
They were resumed in 1879, and the dam as also the slide successfully
completed, with the exception of graveling of the dam in the fall of
1881. The water was lower that summer than it had been for thirty five
years before. The canal was completed and opened for navigation the
following spring.