Flexibility in relation to waterworks practice means the ability to maintain the supply with one unit out of service. As applied to the Hemlock Lake system there is at present a single 5-foot diameter pipe 1,550 feet long extending from Gatehouse No. 2, at Hemlock Lake, into the lake. All the water used from Hemlock Lake must under present conditions pass through this pipe. Also there is a single 6-foot diameter brick tunnel, extending from Gatehouse No. 2, at Hemlock Lake dam, to Overflow No. 1, through which the entire supply must at present pass. The intake pipe and tunnel were constructed in 1893 and have been in continuous service since that date. There is no practicable way to examine the interior of either the pip or tunnel or to make repairs excepting by wholly or at least partially shutting off the draft of water from Hemlock Lake during the period of examination or repair, using water from Rush Reservoir and the distributing reservoirs or from other sources. This does not provide desirable flexibility.
With the new project in operation it would be possible to entirely shut off the flow through either the intake pipe in Hemlock Lake or the tunnel extending from the lake to Overflow No. 1 for a period of several months at a time, to make examination or repairs. In either case the flexibility of the system would be greatly increased since water could be drawn at any time by either route, i.e., through the present tunnel or from the new dam and gatehouse and the new conduit leading therefrom to Overflow No. 1.
Much more attention will probably be paid to flexibility and alternative methods of drawing and routing water in connection with supply systems in the future than in the past. The writer is not sufficiently optimistic to believe that the menace of aerial bombardment will and forever end forever with the termination of the present war. Furthermore, with the possibility of aircraft becoming as numerous as gnats, malicious injury to a water supply system will be much more readily possible than at present unless aerial policing is developed far beyond its present stage.
As at present operated, the supply, whether originating in Hemlock or Canadice Lakes, must be drawn directly from Hemlock Lake. With this project in operation the entire supply from Canadice Lake Outlet would pass into the lower basin of the new Hemlock Reservoir. Hemlock Lake proper could be shut off entirely and the entire supply drawn from Canadice Lake through the Lower Basin for a period of several weeks or even months.
In addition to providing greatly increased flexibility of operation the new project fits in well with the increase of conduit capacity for delivery or water to the City of Rochester. In addition to the construction of a new mains supply conduit from Hemlock Reservoir to overflow No. 1, provision will be made for additional conduits in the future. An additional supply conduit to Rochester when built can be extended through to the new Hemlock Lake dam, so that in the event that the use of the present brick tunnel from Gatehouse No. 2 to Overflow No. 1 is ultimately abandoned, there will still be two main supply lines leading out of the new Hemlock Lake Reservoir.