Cook Plant preoperational studies 1970 / John C. Ayers ... [et al.].

missed central plume-part might have been. Instead, it appears most likely
that the dilution and cooling processes acting on the plume were not steady,
and that the small lens of warm water at Station 19 owed its existence to
having passed along the plume axis during a temporary slackening of the
dilution and cooling processes, while the length of surface temperatures less
than 12.4~ represented a return to full (or extra) strength of these processes.
On 4 November 1970, under north wind, a second survey of the DuPont plume
was carried out. The wind was from the north at 10-14 mph with a very choppy
seas of 1-2 feet height. Air temperature was 5~C.
This day there was, again, upwelling along the shore of colder subsurface
water and blowing of warmer surface water away from shore.
Surface temperature on this day was measured by a thermistor suspended
from the ship's bowsprit and trailing in undisturbed water ahead of the ship.
The temperature field is given in Figure 14.
The total observable effects of the DuPont plume were two small isolated
"bubbles" of the 11.4~ and 11.1~ surface isotherms. These bubbles of the
11.4~ and 11.1~ isotherms reached downcurrent in the direction shown by a
plastic bag full of outfall water which was released at the outfall and retrieved 35 minutes later. The drift of the bag is shown in Figure 14. The
bubbles of 11.1~ and 11.4~ were isolated between the 10.8~ and 11.1~ isotherms
of the alongshore and slightly offshore current and extended downcurrent only
a small distance (3/8 mile).
Attempts at vertical temperature profiles were inconclusive and lost in
the lake-to-shore gradient of temperature.
Again, the DuPont submerged outfall with diffusers appears to be an
efficient system.

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