GENESEE SURVEYS.

24. On the Genesee division, topography surveys have been made of the sites for a dam farther upstream than any heretofore proposed, in order to make certain that a suitable dam could be located entirely above the limits of the Letchworth Park.

A principal object in all my Genesee studies was to so plan a power development as to avoid marring the beautiful scenery of the Letchworth Park, and to determine if flood storage and a profitable amount of power development under public control could be attained and still leave fully as much water flowing over the falls in hours of daylight during the summer season as they now enjoy. The feasibility of a great power development without any serious impairment of the scenic beauty is demonstrated, but the questions of profit to the public from sale of power and of flood control need further study.

Surveys have been made for two alternative power house sites downstream from, and entirely outside of, the Letchworth Park. Topography has also been investigated along a proposed tunnel line, and the relocation of the railroad necessary to accommodate the proposed new dam site has been made.

Maps of the sites described in the preceding paragraph have been prepared on a scale of 100 feet to the inch, and traced on sheets of standard size.

25. Test borings have been made to determine the character of the substrata at various localities in the thinnest portion of the natural rim of the proposed great storage basin above Portage. Samples have been preserved and submitted to experts for classification. A contour map of this debatable ground has been prepared, also a cross section showing the results of the borings and the relation of the clay bank to the proposed water level.

We find that after penetrating a short distance below the present surface and before getting down to the highest water level proposed for the reservoir, the substrata are all of an extremely fine, compact and impervious material, commonly designated by those experienced in test borings as "clay."

`The size of grains in the samples of sand overlying this clay seldom averages more than a few thousandths of an inch in diame

ter, and in nearly all of the deeper strata the grains are so extremely fine as to insure a very high degree of imperviousness.

While additional surveys and many borings would in natural course be made prior to becoming actually committed to the construction of the proposed dam, the surveys and all borings thus far made concur in showing that not the slightest danger of leakage or rupture of this natural embankment is to be feared. At its thinnest point it forms a dam about half a mile in thickness measured at high water level, composed of extremely impervious material.

26. Outline designs for an arched masonry dam at this new Portage site, with a long spillway, have been made, and plans prepared sufficient for demonstrating feasibility and for purpose of a preliminary estimate of cost; and are submitted herewith.

27. Outline designs have been prepared for a power-house with turbines suitable for regularly supplying about sixty-five thousand horse power, working under a maximum head of about five hundred and fifty feet and are submitted herewith.

28. Novel designs for a tall surge tank to be located close to the end of the tunnel, for the purpose of relieving momentum waves, liable to occur in the exceptionally long water column of this tunnel under fluctuations of the power demand, have been worked out, and outline studies of the structures are presented.

29. Time and means have not sufficed for borings along the proposed tunnel line or at the alternative power sites, but the indications of the outcrop are that sound rock, very favorable for tunneling, will be found at the low level proposed; neither has time permitted a balance to be struck between the merits of the two alternative power sites, one having the shorter tunnel, the other the greater fall and power.

In general the best economy is found in concentrating all the fall at a single site and in getting the most out of the opportunity. The State should be as little wasteful as possible of its natural resources; therefore the first attention has been given to the lower site.

30. Following a chance suggestion, said to have been made by Lord Kelvin when he inspected the scenery at the Portage Falls, to which great importance has been attached by some of the Rochester journalists, careful study in the field has been made

concerning the feasibility of building a series of small dams and small reservoirs on the several tributaries of the Genesee above Mount Morris as a substitute for the one great dam and reservoir proposed above Portage.

After a study of the topographic maps and drainage areas a reconnoissance was made at each important tributary, to determine if conditions for dam and reservoir building were favorable, and what was the largest amount of storage that could be obtained. These studies were made under my supervision by an engineer of experience in water power development (Mr. George G. Shedd, see special reports, page 219) and prove beyond all serious doubt or question that the scheme of small reservoirs on tributaries, in place of a large reservoir on the main river, is utterly visionary and impracticable.

31. Outside inspection was made of substantially every building within the district proposed to be flooded by the Portage reservoir, with a view to estimating its probable fair market value.

Estimates of probable fair market value have also been made for all of the land to be overflowed. The figures thus obtained are regarded merely as a basis for a rough preliminary estimate of cost of acquiring the reservoir site. Although these figures are believed to average very closely to the real market value, it is recognized that costs of condemnation and the generous views which prevail in making settlements of this kind tend toward a total expense in the acquisition of real estate for reservoir purposes that is larger than the prior value. The sum total of the figures obtained as above has, therefore, been increased by 50 per cent. to cover legal expenses and other allowances.

32. As previously indicated, a study has been made of all of the long term rainfall records in the vicinity of the upper Genesee, with a view to learning if there were other periods when the rainfall and storage requirements were materially different from those existing during the period of gagings at Mt. Morris from 1903 to 1907.

33. A review of all published gagings of the Genesee river has been made and from these has been computed the probable yield at the Portage site, and the fluctuations in height of water in the

reservoir from month to month under various rates of constant draft has also been worked out, so that the margin of uncertainty is now small in the amount of power that could be produced at Portage and at Rochester from the proposed reservoir.

34. The records of the destructive Genesee floods have been reviewed in connection with a partial study of the restraining effect upon them of a reservoir used chiefly for water power, but to fully work out the Rochester and Genesee flood problem is a far larger task than could be brought within the scope of these studies of 1907.

FULL USE OF THE OPPORTUNITY.

At the outset it was determined to give the surveys and first studies such scope that the natural resources of each situation could be availed of to the greatest possible degree, and if obstacles were encountered as the studies progressed, then retrench in the design so far as economy might require.

A Sacandaga reservoir of greater area than any heretofore proposed was studied, in order that it might be possible to keep the main portion of the reservoir bed entirely covered by water even when drawn to the lowest point that the outlet gates would permit.

Since it appeared probable that by raising the flow line to an elevation some thirty feet higher than heretofore proposed, the artificial lake could be give the semblance of a natural lake with sandy beaches even when at its lowest level, and that it could thus be made a beautiful feature in the landscape at all times, and since with this greater depth it would never be necessary to uncover the present great swamp, risk of the reservoir becoming offensive would be avoided; the first study was directed toward a flow line. at an elevation of 780 feet above sea, but after a fuller reconnoissance on the ground, the lower level of 770 feet was adopted, and so far as the present studies have shown, this high level of 770 feet is feasible, and the reservoir will give all needed storage if drawn only down to 740 in the most severe drought of the half century, being lowered only about ten feet in years of ordinary rainfall. Near some of the villages, on certain of the coves that

might otherwise have their beds uncovered when reservoir is drawn down, low earth dams can be cheaply built for preventing this, if found desirable.

Studies were made for the highest practicable reservoir level and for the lowest tail race level and for developing all upon a single fall because it appeared desirable in a project under State development to utilize to the utmost the water power that could be created, as well as to simplify the problem of future management and number of men required, by concentrating the entire fall for use in a single power-house and utilizing for power the full head of the lake. The higher the lake level the greater the power.