About the MLWD

Manhasset-Lakeville Water District serves about 45,000 customers through over 10,000 individual service connections within a 10.2 square mile service area. The district produces its supply of potable water through the use of eighteen (18) separate wells located at thirteen (13) different sites throughout the Manhasset-Lakeville area.

The District's supply is drawn from underground aquifer systems that underlie our service area. Fourteen wells are set in the Magothy aquifer at depths between 100 and 470 feet while four wells are drilled into the deeper Lloyd aquifer at depths reaching 700 feet. Raw water treatment varies and includes disinfection, pH adjustment, aeration, and adsorption. The District maintains a minimum chlorine residual of 0.2ppm as required by the NYS Dept. of Health.  All distribution water is in strict compliance with the New York State guidelines for potable water.

Currently, nine District wells are being treated for the removal of elevated levels of volatile organic compounds. Packed aeration towers (air strippers) or Granular Activated Carbon (GAC) filters are used to remove these organics. The raw water pH is raised to between 7.5 and 8.0 by the addition of a 25% sodium hydroxide solution (caustic soda).  Since aeration also increases the pH of raw water, District wells, which are aerated, are not treated with sodium hydroxide. Three wells have been removed form service as part of the offsite remediation plan associated with the former Lockheed Martin site in Lake Success. One well has been removed from service for elevated nitrate levels.

The Water District currently maintains four (4) water storage tanks with a total volume of 5.5 million gallons. Two ground tanks hold a combined 4 million gallons while two elevated tanks hold a combined 1.5 million gallons. Five booster pumps are currently available to pump water from the ground tanks into the distribution system.

The District maintains two pressure zones. The high elevation of new communities along the eastern boundary of the District led to the creation of a high service area. Three centrifugal pumps are available to draw water from the distribution system and boost pressure to these communities. During periods of high demand, two variable speed well pumps can also be dedicated to this system. Outside of the high service area, system pressures are directly related to elevated tank levels and are maintained through the use of an integrated operations system consisting of phone lines, electronic monitoring devices, and computer software (SCADA). All stations are checked daily to ensure proper operation by our licensed New York State Water Treatment Plant Operators.