nels in the ice surface, which, if filled with water

material and equipment lined up ahead of time.

and then frozen, tend to further break the ice since

This does not mean actually having the equip-

water expands when frozen. Most dusting in the

ment on hand but being able to mobilize opera-

past has been done much farther north than

tions in a short time. It is imperative to identify

Nebraska, so it is difficult to extrapolate timing

the sites most likely requiring dusting ahead of

since Nebraska warms up quicker and the sun

time, as resources and time are likely to be limit-

angle gets higher sooner. The most critical aspects

ed. Plans for dusting the Platte have been devel-

of timing, though, appear to be adequate sun-

oped twice since 1979. The State of Nebraska re-

shine, near- or above-freezing temperatures and

quested initial technical planning assistance for

lack of snowfall for several days following appli-

dusting operations from the Corps of Engineers

cation. It is best to study past climate data to de-

in 1980 and 1982. Dusting was not carried out in

termine the earliest that dusting can be effective.

either year because weather conditions became

Dust can be applied far in advance of breakup

favorable for natural melting prior to breakup,

if the intent is to weaken a midwinter jam that

although some ice jamming did occur. Table 19

freezes in place. Midwinter jams may not be very

summarizes the sites and materials required for

damaging at the time of formation but can cause

the ice-dusting operation planned in 1982. Even-

great damage at normal breakup if they freeze in

tually shorter or fewer strips were planned to re-

place and block a large portion of the flow chan-

duce the cost of dusting, but dusting was not done.

nel. Dusting can weaken the ice and reduce the

The dusting strips were chosen on the basis of

volume in a midwinter jam enough so that it does

historical ice-jamming problems. The effort that

not pose a problem later. The rate of melting will

went into planning these two proposed ventures

not be as effective as later, but since jams tend to

should serve as a guide for planning future dust-

be several times thicker than the ice blocks com-

ing operations. Other items should be incorporat-

posing it, more time is required to thin the ice.

ed to form an overall plan of action for dusting.

Multiple applications may be necessary because

The following is intended as a checklist in plan-

of the thickness and subsequent snowfalls. The

ning dusting operations, and a chart for estimat-

ice in some rivers may contain sediment that gives

ing the cost of the operation is also included.

it a dirty appearance and will accelerate the melt-

1) Identify sites for dusting. Sites of recurring

ing of this ice in a jam. Dusting to melt normal

historical jamming problems should always be

spring breakup jams has not proven very effec-

identified as possible dusting sites. The need for

tive because it generally takes too long to thin the

dusting these various sites may vary from year to