Winter operations, 1970-1971 / John C. Ayers, Norbert W. O'Hara, William L. Yocum.

Along the east shore of Lake Michigan we have found two ridges to be the rule.
These ridges are solidly grounded on the beach and just off the beach and are
usually laden with sand incorporated into the ice. Outside (lakeward) of these
ridges for a distance of a few tens of feet ice floes have amalagamated into an
ice sheet. This is the "lagoon" referred to by Marshall. Outside the lagoon
there forms a heavier grounded outer ice ridge, the "outer barrier" of Marshall.
This complex of two inshore ridges, a frozen lagoon, and an outer barrier has
been surprisingly consistent along the eastern shore of Lake Michigan during the
two winters of observation.
It is to the integrity of this complex of three ice ridges and a frozen
lagoon, in the presence of thermal discharges, that this report addresses
itself.
Our efforts in this connection during the winter of 1970-71 have not been
completely successful; in the far northern part of the lake solid ice was found,
but the small plants there were having little melting effect. In the southern
three-quarters of the lake, broken ice was the rule on the days when we had
overflights or shore expeditions to outfalls of operating plants. Perhaps our
greatest success has been to obtain, this winter, pictures of the effects of
the only two submerged outfalls that we know of to date: the Traverse City
generating station and that of the DuPont Chemical Company at Montague, Michigan.
Dr. O'Hara overflew the Michigan shore from Big Rock to Grand Haven on 18
February before bad weather forced the abortion of the flight; on 24 February
he flew over the Cook, Palisades, and Campbell plant sites; on 17 March he overflew the southern end of the lake from Bailly Station in Indiana to Manistee,
Michigan; and on 10 March W. L. Yocum made a shore expedition to the outfalls
of the Campbell and Michigan City generating stations.
Despite our efforts, the results of our 1970-71 investigations of the effects

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