up to an elevation of 220 feet and abrupt beyond it, it will
be advisable to take this as the minimum or low-water level of our
reservoir. It is generally estimated that 25 per cent of the volume
of the mean annual rain on a given catchment is sufficient
reservoir capacity to fully utilize the flood flows. We have long
series of observations of rainfall at three points, which may be
taken to fairly represent the Passaic catchment. At Newark the mean
annual rainfall is 46.2 inches, at Paterson, 50 inches, and at Lake
Hopatcong, 42. The last being on the Highlands, like most of our
watersheds, is perhaps the safest to use. Now, 25 per cent of 42.5
inches, 10.62 inches, which, on 420 square miles, give a volume of
10,362,000,000 cubic feet, the necessary capacity of reservoir.

By raising our reservoir to 240 feet when full we secure a capacity
of 10,493,000,000 cubic feet, or ample to utilize the heaviest
floods of the watershed. This gives a beautiful sheet of water 21.1
square miles in area, with bold, rocky shores, and a depth at dam
of 72 feet. We secure the above capacity by uncovering but 22 per
cent of the reservoir bottom; and, as we shall presently see, we
shall rarely need more than half this storage, and probably not
oftener than once in ten years will we expose over 10 per cent of
the area. By building side dams to keep certain flats always flowed
this may be reduced to 5 per cent; and this area will be pretty
evenly distributed around 36 miles of uninhabited shore line,
leaving the reservoir open to no valid sanitary objections. On the
contrary, by relieving the remainder of the Passaic Basin of the
flood waters of the Pompton, which now flow large areas of flat
land during wet seasons, the sanitary condition of the valley would
be much improved.

In constructing this reservoir Mr. Vermeule stated that the following
work would be necessary:

The removal of the Delaware, Lackawanna and Western Railroad from
the basin by changing the alignment for 6 miles. It may be done
without increase of length or detriment to the alignment.

Three and one-fourth miles of the Morris Canal must be rebuilt. No
engineering difficulties are involved.

Of the New York and Greenwood Lake Railway, 9 miles would have to
be rebuilt.

The New York, Susqueha