Water: we drink it, bathe in it, flush the toilet with it, maintain our landscapes, fight fires. Humanity depends upon it, but most people take it for granted. You open the faucet and water appears, every time, all you want, for less than a penny per gallon. This does not happen through magic. It happens because of sound planning and engineering.
Over the past twenty years, the Manhasset-Lakeville Water District has developed, implemented and updated an ongoing capital improvement program for your supply system. This work has included new wells, elevated tank maintenance, rehabilitating pumping stations, hydrant replacements, and miles of water main replacements and extensions. This year our improvement program includes the replacement of our elevated storage tank located in Munsey Park.
Our elevated storage tanks are critical to our ability to provide water service. Have you ever lost electric power? What about cable TV or phone service? Now, try to recall the last time you lost your water service. Through winter storms, through Hurricane Sandy, through the great black-out of August 2003, your water service was uninterrupted. Imagine not being able to flush your toilet for ten days during Sandy!
What makes our system withstand power outages is our elevated storage tanks. When power is lost, our pumps turn off. But the water in the elevated tanks then falls by gravity into the distribution system to supply water, while we work to bring our back-up power supplies on line, until regular power is finally restored.
The elevated tanks are also critical for fire protection and for sanitary concerns. When there is a fire or a main break, large quantities of water must be available instantaneously. If the elevated tanks were not available, the pressure drop during a main break or fire fighting could be so dramatic that negative pressure could develop in the water mains, which could suck tainted water into the distribution system and threaten the safety of our supply.
Elevated storage also regulates pressure throughout the entire distribution system. The water levels in our elevated tanks rise and fall with system demand. During peak demand when so many sprinklers are on, water from the elevated tanks falls into the system. As the sprinklers turn off, the water rises back into the tank. During this cycle our large pumps turn on to meet the demand and then off as the demand eases. The tanks cushion the effects of the pumps coming on and off, preventing large pressure fluctuations.
None of those benefits of elevated storage can be replicated as effectively with ground storage and booster pumps. Replacing elevated storage with booster pumps/ground storage will result in additional power costs for double pumping water, once into the tank and once out. The water supplied by the pumps will not be instantaneous. There are multiple points of failure in a booster station: pumps break, electrical and computer controls, power supply, backup power supply. And once again, booster pumps cannot provide the equivalent operational storage and pressure control function.
We understand that elimination of the tank would provide obvious aesthetic improvement for our neighbors, however, our elevated storage provides foolproof instantaneous emergency and operational storage through the use of gravity, without any power or operational costs. While technological advances in many areas have radically changed our lives for the better, we have yet to improve upon gravity in the context of water supply. The community is now weighing the benefits of elevated storage against its visual impact. I say beauty is in the eye of the beholder.
Paul J. Schrader, P.E.