cepts that were demonstrated at the Soo Locks
wall would slightly decrease the effective width
during the Demonstration Program. Additional
of the lock and be subject to damage by impact
information on ice control at locks can be found
from ship hulls and shear forces transmitted
in Hanamoto (1977) and USACE (1982).
through any attached ice. With ice tightly packed
between a ship hull and the lock wall, lock op-
eration could impose a vertical shearing force on
Minimizing ice adhesion
the order of 100 lbf per foot of wall length in crit-
to lock walls
Ice can form on lock walls either by direct freez-
ical sections.
ing of water or by the adhesion of broken ice that
is crushed and smeared against a wall by ships.
Surface coatings
The most significant accumulations of ice occur
There is a long history of study on adhesion
in a several-foot-thick collar extending down from
reduction coatings for a variety of applications,
the water surface at the upper pool elevation. A
but chemical coatings that shed ice reliably and
number of techniques were investigated to try to
repeatedly have not yet emerged for commercial
either minimize the formation of such ice depos-
use. The only chemical treatment that has been
its or reduce the strength of ice adhesion to the
used successfully on a large scale is repeated ap-
lock walls.
plication of chemicals that depress the freezing
point of water. As far as horizontal concrete sur-
Modification of operating procedures
faces are concerned, the classic treatment for ice
Since the surface of a lock wall must be cooled
removal is application of sodium chloride or cal-
below 32F before significant ice can form on or
cium chloride.
adhere to a lock wall, it is unlikely that a sub-
An ice collar control method using a chemical
merged portion of a wall will undergo the neces-
coating to reduce the adhesive force between the
sary cooling. Thus, there is a strong incentive to
coated surface and the ice that forms on it was
hold the lock at the highest feasible water level
tested at the Soo Locks during the Demonstra-
during the long intervals between ship passages,
tion Program (Frankenstein et al. 1976). The ba-
preventing ice accumulation on the lower por-
sic material is a long-chain copolymer compound
tions of the wall.
of polycarbonates and polysiloxanes. The mate-
rial is produced on order by the General Electric
Built-in wall heaters
Co. in Pittsfield, Massachusetts, with a trade name
Ice adhesion can be prevented by maintain-
of LR 5630 (new designation GR 5530). The com-
ing the wall temperature above 32F, or ice col-
pound comes in coarse powder form.
lars can be shed by raising the wall temperature
A solution of the compound, silicone oil and
above freezing periodically. Possible arrangements
toluene leaves a thin coat of the copolymer and
include embedded electrical heating cables, con-
silicone on the surface of the lock wall. The sur-
ductive surface materials and internal piping or
face to be coated must be clean and dry. For con-
ducts for warm fluids. No special merits have been
crete and metal surfaces, steam cleaning is suffi-
found for a hot fluid system compared to an elec-
cient. A detergent was added to the steam cleaner
trical system for heating lock walls.
water supply in one case where the walls were
Pavement heating systems designed to melt
heavily coated with oil and algae. Once the sur-
snow and ice usually use a power density of 30
face is clean and dry, the solution can be sprayed
on using an airless spray gun. A single pass will
horizontally at 5-in. centers, with a burial depth
deposit a coat 12 mils thick. Three coats are rec-
of 3 in., full heating coverage for a 5-ft depth of
ommended for a coating thickness of about 5 mils.
bonded ice collar is achieved. At a power density
Tests were also conducted to examine the merits
of 30 W/ft2, the cable has to dissipate 15 W/ft. If
of an undercoating for the copolymer on concrete
the system is amortized over 20 years, the average
surfaces that are worn and rough. An epoxy-type
annual cost for amortization plus direct operating
coating was employed, acting as a filler over the
cost is approximately ,000 at 3 cents/kW-hr.
rough concrete, and it resulted in a surface to which
Conductive panels have also been considered,
the copolymer adhered better. While sprayed-on
but they would find their best application where
coatings of copolymer can reduce the strength of
the conductive material can be recessed so as to
adhesive bonds, it appears that a subsidiary me-
maintain a flush face on the lock wall. Conduc-
chanical system is need to actually dislodge the
tive panels attached directly to an existing lock
ice that accumulates. Periodic renewal of the coat-
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