RÉSUMÉ

Before drawing conclusions upon which to base recommendations for future action it will be necessary to determine the effect of restoring the levels of the Lakes by compensating works of some the conservation of the Nation's resources. In character upon Table 6, Part III, the effect of uncompensated diversions was a loss of resources, as represented by water power or capital. Table 10 has been prepared in a form similar to that of Table 6, except that the columns show results of diversions of 5,000, 8,000, and 10,000 cubic feet per second in 1935, 1950, and 1975.

These show that Extracts from Table 10 are found in Table 11. from an economic point of view diversions should be decreased as power developments are made, for the ultimate result is a large economic loss.

The estimated loss in power per cubic foot per second used in Table 10 is based upon the following program for power development:

TABLE 9.-Program for power development

1924. 1935. 1950

1975

This does not include any estimate for power development in the lower Mississippi, for while it may be physically possible to recover some of the power-notably at Thebes-the costs will always be prohibitive.

1

=

TABLE 10.-Comparative statement of economic losses or benefits

120 horse power lost per cubic foot-second.

230 horse power lost per cubic foot-second.

$38 horse power lost per cubic foot-second.

Comparing now the diversion requirements from the points of view of national economy, Chicago's sanitation needs, and the construction and maintenance of barge channels between Chicago and Cairo, Table 12 results:

TABLE 12.-Comparison of diversion requirements

The last column in this table indicates what is believed to be the most reasonable compromise. Such a program will meet the requirements of sanitation, will not aggravate flood conditions on the lower Illinois River, and will provide adequately for any program for the improvement of a through waterway from Chicago to Cairo. Furthermore, past performances of the trustees of the Sanitary District of Chicago indicate that they will take full advantage of any privileges accorded them, unless a strict program is outlined by which their future operations as regards construction of sewagetreatment plants will be guided and results of these operations will not be such as to permit an ultimate reduction in the amount of water diverted without hardship, if not danger, to the community.

It would be well to investigate the effect of this diversion program as regards the improvement of the Illinois River. In this connection it is believed quite proper to assume that ultimately a 9-foot channel will be provided in the river. With the continued development of economical barge transportation, with the growth of industries and commerce in Chicago and vicinity, a volume of commerce will spring up which will demand such an improvement sooner or later. While it is always unsafe to predict the time when such a state of affairs will come to pass, it is more or less necessary to make

some assumption in a study like this, and accordingly it will be supposed that there will be sufficient demand before 1945 to warrant the improvement of the channel to that depth.

When such a condition exists the amount of commerce passing through the locks in the river will find them to be an obstacle. Accordingly, in planning for the future needs of navigation it should. be assumed that the navigation dams will all be removed by that time as the locks are too small to pass commerce such as would require a 9-foot channel, and the cost of rebuilding them would be much greater than the additional dredging necessitated by their removal.

With 8,500 second-feet of flow the State dams are obstacles to navigation, and as the program for diversion permits that amount until 1935 it would be better to have these two dams removed at once and get the benefit of a clean channel in the meantime. The saving effected by having these locks out of commission between 1925 and 1945 amounts to $600,000 (Table 8).

While Table 9 shows it is cheaper to remove the two Federal dams as far as the period from 1925 to 1935 is concerned when it becomes necessary to provide an 8-foot channel with only 6,000, cubic feet per second of water or a 9-foot channel with but 5,000, it is more economical to retain these structures. The savings from 1925 to 1935 by removing them amount to about $275,000. The loss between 1935 and 1945 amounts to about $156,000, so the net result is in favor of their early removal, particularly in view of the fact that a commerce of considerable volume would find the locks to be obstacles.

PART VI

CONCLUSIONS

The Sanitary District of Chicago, a municipality created by the State of Illinois, has constructed a drainage canal with auxiliary channels connecting Lake Michigan with the Des Plaines and Illinois Rivers.

Through these channels it is now diverting from Lake Michigan an average of 8,000 cubic feet per second of water, this being the present method of treating the sewage of the community and preventing its mingling with the water supply.

This diversion has lowered the levels of the Great Lakes and connecting channels to the positive detriment of navigation interests. This diversion permanently decreases the amount of water power available to the nation, not an insignificant loss at the present time, but of large proportions in the future.

This diversion causes damages which have given rise to considerable complaint in the Illinois valley by way of flooding bottom lands and increasing the cost of levees.

The nuisance created along the Illinois and Des Plaines Rivers by the sewage introduced therein is not intolerable. No harm will be done if conditions get no worse.

The added flow to the discharge of the Illinois and Mississippi Rivers is of some benefit to navigation. Ultimately the main channel and the Sag Channel will be of considerable value as parts of a through barge waterway from Chicago to the Mississippi River.

The sanitary district trustees have prepared and adopted a program of sewage treatment by methods other than dilution which precludes the necessity of making any substantial increase in the amount of water diverted notwithstanding the increase in population of the district.

The present consumption of water in the city of Chicago is enormous. It can be reduced from about 275 gallons per capita per day to about 125 by installing a system of universal metering.

The saving in pumping costs effected by metering will finance a complete filtration system for the city. The reduction in water consumption by reducing the amount of sewage will permit a reduction in the cost of sewage-treatment plants of about $20,000,000, and prolong the life of those completed.