A portion of the water delivered by the Hultman Aqueduct replenishes the Norumbega Reservoir from which the MWRA draws water to meet periods of peak demand. The remainder flows through various connecting tunnels to metropolitan Boston customers. [FN6] Water is treated with chlorine as it leaves the Wachusett Reservoir, and again as it leaves the Norumbega Reservoir. The water is also adjusted for pH content at a corrosion control facility in Marlborough. [FN7] In 1991, after reviewing a 1989 consultant's report and testing various treatment alternatives, the MWRA's Board of Directors concluded that the MWRA would be unable to meet the filtration avoidance criteria.