The Hemlock Lake water supply system has been in use for 68 years. Originally built to supply 7,5000,000 gallons of water per day, increased conduit capacity and the raising of the Hemlock Lake dam in 1927 has supplied Rochester with adequate and excellent water up to the present time.
The original cost of the system was low, measured in terms of accepted standards, and the City of Rochester has been exceedingly fortunate in having so excellent a water supply available at so low a cost over such a long period of time. This low cost of water has, however, been to some extent subject to the penalty of deferred maintenance and expansion.
Waterworks structures, such as dams and conduits, are relatively permanent, yet they are subject to gradual deterioration. It is impracticable to maintain such structures, particularly those underground, in strictly first-class condition at all times. The alternative is to permit deferred maintenance to occur until some condition arises which either permits or requires major repairs or replacement of structures, the most usual occasion for such repair or replacement being the need for increased supply. One essential feature of this investigation has been to determine the condition of the existing structures and their suitability for continued or future use.
The present Hemlock Lake system as it stands now, with relatively minor repairs, has heretofore been estimated to be capable of yielding a dependable supply of 31 mgd, and with new construction to provide for the complete regulation of Canadice Lake, it has been estimated that a supply of 34.5 mgd can be obtained. There would still be a considerable quantity of water wasted from the drainage basin of Hemlock Lake because the storage in the lake as now developed is inadequate to impound and regulate all of the runoff from the tributary area at the time it occurs.
With the exception of 1890, when a water shortage occurred in Rochester resulting from the fact that the then conduit capacity was less than the demand, the present Hemlock Lake system, with some purchased water, has supplied Rochester with adequate water from 1876 to the present time. There were threatened water shortages in 1930, 1934-1935, and 1941-1942, indicating that the present supply is inadequate to meet either increased demand or more severe droughts than those of recent years.
The water consumption in Rochester during the five pre-war years, 1935-1939 and subsequent years compares as follows, in million gallons per day a), including purchased water, if any.
mgd 1935 ............................................... 27.66 1936 ............................................... 27.82 1937 ............................................... 26.57 1938 ............................................... 25.88 1939 ............................................... 28.84 Average, 1935-1939 ....................... 27.35 1940 ............................................... 30.02 1941 ............................................... 31.40 1942 ............................................... 32.80 1943 (to end of Nov.) ..................... 34.16
The water consumption increased progressively in 1940-1942, and in 1942 it was 5.45 mgd or 20% greater than the 5 year average, 1935-1939.
The average water consumption for the four war years 1940 to 1943 was 32.10 mgd or 2 mgd in excess of the dependable supply from the present sources as now developed, and within 2 mgd of the heretofore estimated dependable supply from the present sources with increased storage in Canadice Lake. Records of the City Water Department show that increased water consumption during the past four years has been chiefly due to increase of industrial use under war conditions.
The question may naturally be asked whether normal conditions will not be restored after the present war and the water consumption then drop back to 28 or 30 mgd, making necessary only the provision of a temporary increase of supply.
Water consumption, unlike most things, tends to go up more easily than it goes down. This is especially true in a city like Rochester, where in the past the per capita water consumption has been below the average in cities of corresponding size, in spite of the high rank of Rochester as an industrial center. Furthermore, water consumption tends to increase as the distribution system grows older. Some increase of normal per capita water consumption in Rochester in the future is therefore to be expected for various reasons.
Rochester industries must be permitted to continue their normal growth after the war. Rochester presents a somewhat unusual situation because of the restriction of its boundaries by adjacent incorporated suburbs and the present highly developed state of its industries. The desideratum of expansion is increased production.
This can be obtained by either enlarging the plants at their present sites when needed or in the same manner as now, i.e., by plant operation with more than one daily shift of labor.
Barring the effect of financial depressions, only a partial rather than a complete return to normal pre-war water consumption can reasonably be presumed for post-war conditions. Some definite, permanent steps to increase the water supply for post-war conditions should be taken, and means provided to meet war demands should as far as practicable fit in with a longer range water supply program.
Some of the structures connected with the present Hemlock water system require either renewal, replacement or repair if they are to continue much longer in service. This results partly from increased water demands and enhanced conditions as compared with those existing when the structures were built, and in part from deferred maintenance.
Additional flexibility is needed to provide alternative methods of operation in case of emergency. This is particularly true of the 6-foot diameter brick supply tunnel, built in 1893, leading from Gatehouse No. 2 at Hemlock Lake to Overflow No. 1, 1 ½ miles to the north, at which point it supplies conduits II and III. Increased storage is also needed to better regulate and more completely utilize the available yield of the tributary drainage areas.
a) Corrected for meter under-registration.