EP 1110-2-11
30 Nov 94
Chapter 5
Ice Jam Mitigation Case Studies
5-1. Kankakee River, IL - Thermal Control
a. The upstream end of the backwater from the Dresden Island Lock and Dam on the Illinois River extends to about
River Mile 3.5 on the Kankakee River near Wilmington, IL. Frazil ice floes form a stable ice cover on the pool, which
thickens as frazil ice then deposits beneath the ice cover. The thick frazil ice deposit requires more force to break up
than the thinner upstream ice and provides an obstruction to the passage of upstream river ice, which breaks up prior to
this thick ice deposit. An ice jam often forms at the upper end of the deposit and progresses upstream, flooding the city
of Wilmington and surrounding areas. The ice jam flood in 1982, which caused more than million in damages, was
followed by other ice jam events in 1984 (0K) and 1985 (
||content||
M). Several alternative ice jam mitigation measures were
considered. Because of the proximity of the cooling pond for the Dresden nuclear power plant, thermal ice control
appeared feasible. The intent of the thermal control was to thin or melt the thick frazil deposits that resist breakup, thus
allowing the fragmented ice from upstream to pass unobstructed.
b. In a demonstration project, 20 C (68 oF) water from the cooling ponds adjacent to the Kankakee River near Wil-
mington was siphoned in three 0.76-m-diam (30-in.-diam) pipes into the river upstream of the ice cover for 2 weeks prior
to the anticipated breakup in 1988 (Figure 5-1). The maximum siphon flow is 4.25 cu m/s (150 cfs) compared with the
expected river flow of approximately 113.2 cu m/s (4,000 cfs). The measured rise in water temperature was less than 1o.
The warm water input melted the existing ice so that ice floes passed unhindered during the natural breakup period and
flooding was averted (Figure 5-2).
c. This 0,000 system worked successfully for 2 consecutive years. There were no reported negative environmen-
tal impacts.
5-2. Hardwick, VT - Improved Natural Storage, Ice Retention, Mechanical Removal
a. Relatively frequent breakup ice jams have caused serious damage in this small Vermont town. A combination of
techniques is used to reduce flooding impacts.
b. To slow the movement of broken ice, two booms were constructed (Figure 5-3). The vertically oriented tire
booms, which are suspended from shore, collect broken ice during breakup, some of which is stored on the overbanks.
The booms delay the downstream passage of ice while ice removal is performed in town. Since the winter of l983-84,
these booms have been placed upstream from town annually. Although the booms occasionally fail, they do provide ice
retention.
c. An ice storage area downstream of the town accommodates some of the ice that jams and thereby provides added
protection. In addition, when local officials first begin to notice serious ice jams developing, the town road crew mechan-
ically breaks up and removes the ice to keep the river open.
5-3. Oil City, PA - Floating Ice Boom, Revised Operational Procedures, Ice Control Dam
a. Oil City is located in northwestern Pennsylvania. The city suffered chronic ice jam flooding from the mid-1880s
to the mid-1980s. In February 1982, ice jam flooding caused more than million in damages in downtown Oil City.
b. Research indicates that the ice jam flooding was caused in part by a massive deposit of frazil ice naturally occur-
ring in a long, deep pool in the Allegheny River downstream of Oil City and extending upstream past the confluence with
Oil Creek. Large quantities of frazil generated in the creek were also deposited in the river and backwater at the mouth
of the creek. The ice on Oil Creek typically broke up and moved downstream before the ice cover on the Allegheny
River. The tributary ice ran unimpeded to the river until it met the stable ice at the confluence with the Allegheny River
and formed an ice jam.
5-1
Previous Page
