Ice control for hydropower

Rapid ice cover progression depends on flow re-

wind-driven lake ice overriding the Lake St.

ductions during the 7- to 14-day formation peri-

Francis boom, as is the case with the Lake Erie

od. Since flow reduction is costly in terms of lost

boom.*

hydropower production, the operators closely

A similar but smaller timber boom is located on

monitor water temperatures and weather to

the St. Marys River, south of the locks at Sault Ste.

decide when to form the cover. As with the Lake

Marie, Michigan (Fig. 6). Since its first installation

St. Francis boom, central gaps in the upstream

in the winter of 1975-76, the boom has performed

booms allow some frazil and floes to move

well, with only minor modifications (Perham

through to the downstream booms, speeding the

1977, 1978, 1984, 1985). The boom's centrally locat-

upstream progression of the ice cover. The two

ed navigation opening allows the passage of

booms nearest the forebay are constructed of

double circular steel pontoons as shown in Fig-

ure 6. The four upstream booms within the

canal, originally timbers, have been replaced in

recent years by rectangular steel pontoons, re-

ducing maintenance costs. Once the ice cover

forms in the canal, flow increases smooth the

cover's underside, decreasing hydropower head

losses. Flow is again decreased for a short period

at breakup to reduce the ice forces on the booms.

Strain links on three of the anchor lines of the

forebay boom provide valuable force data,

which guide operators on when to reduce or in-

crease the flow. Ice management at Beauharnois

is estimated to increase winter production by an

Figure 6. Boom on Beauharnois Canal, constructed of

average of 200 MW (Perham and Raciot 1975,

double steel pontoons.

Perham 1975*).

Ice control is equally important to hydro-

downbound vessels while limiting the ice vol-

power production in the International Section of

ume entering the constricted channel at the Lit-

the St. Lawrence. The New York Power Author-

tle Rapids Cut. For the same purpose, a four-

ity and Ontario Hydro annually install six tim-

span timber boom with a navigation opening

ber booms with a total length of roughly 15,000

was installed in 1976 at the Copeland Cut on the

ft in the 8-mile-long reach from Galop Island to

WileyDondero Canal near Massena, New York.

Ogdensburg (Fig. 7a and b). The booms are part

The boom performed well during its first season

of an extensive ice management program,

of use (Uzuner et al. 1977), but no recent infor-

designed to maximize winter power production

mation on the boom's performance has been

at the Moses Saunders Dam at Massena, New

obtained.

York, 40 miles downstream. The booms form an

ice cover upstream of Lake St. Lawrence, the

Ice control for hydropower

dam's pool, reducing the production of frazil.

Upstream of Montreal the focus of the ice

Before the booms were installed in the fall of

control efforts shifts from navigation and ice jam

1959, severe hanging dams formed at the up-

prevention to hydroelectric production. The

stream edge of Lake St. Lawrence, resulting in

Lake Erie and Lake St. Francis booms could be

placed in this group, since they are both located

significant production losses at the hydro sta-

upstream of hydrostations and their failure to

tions at Massena. The booms have performed

perform results in production losses.

well, with only minor modifications, since their

Downstream of the Lake St. Francis boom, a

first deployment 34 years ago. Careful flow

series of six steel pontoon booms on the Beau-

manipulation at the dam at Massena and the

harnois Canal promote the rapid formation of an

Iroquois control structure (Fig. 7c), airborne sur-

ice cover, upstream of the power station (Fig. 4).

veillance and field measurement of ice thickness

and water temperature are all critical compo-

* Personal communication with Gilles Maisoneuve, Hydro

nents of the overall ice management scheme on

Quebec, Centrale Beauharnois, April 1994.