Q2 Z2,(Q2) Z2(Q2) - Institute for Water Resources - U.S. Army

i.e., 90 percent of all loaded tows make a return trip empty. This
statement is not strictly true, for undoubtedly many tows contained
both loaded and empty barges. This does not change the analysis, how-
ever; and it is easier to speak of empty and full tows rather than
tows some of whose barges may be full and others empty. Therefore,
X* is approximately 3,000 tows per year or 0.34 tows per hour.
The average service times per tow for each of the five locks are
available from the Corps study. Thus the waiting times, T L and T Lq
may be calculated. These quantities are presented in Table 4.5 along
with the actual values of these variables for 1949.
Lock
Table 4.5
AVERAGE LOCKING TINE PER TOW FOR FIVE LOCKS
ON THE ILLINOIS WATERWAY, 1949
Predicted Reported .Predicted Reported
Total Total Time in
Waiting Time Waiting Time Queue
(min.) (min.) (min.)
- r
i
Time in
Queue
Lockport
Brandon Road
Dresden Is. .
Marseilles '
Starved Rock . _.. .
75.9
89.5
57.7
. 70.6
47.6
I
68.4
75.8 .
55.5
64.2
50.1
22.8 '
30.2
14.3
20.1
10.1
15.3
16.5
12.1
13.7
12.6
SOURCE: Interim Survey Report: Duplicate Locks ) Illinois
Waterway.
For 1950 the average tow size seemed about the same as for 1949,
but the average tonnage per loaded barge was larger at about 1200.
,
Therefore, C is 5,000 for 1950. Total tonnage on the waterway was
also larger in 1950, averaging 10,457,127 through the five locks.
Therefore, 0 is approximated as 10,500,000 tons, and X becomes 1,750
-
trips peryear.. It appears that empty hauls were 85 percent of
93