Work on the northern end of the park began in 1989.[221] A $51 million campaign, announced in 1993,[222] resulted in the restoration of bridle trails,[223] the Mall,[224] the Harlem Meer,[225] and the North Woods,[221] and the construction of the Dana Discovery Center on the Harlem Meer.[225] This was followed by the Conservancy's overhaul of the 55 acres (22 ha) near the Great Lawn and Turtle Pond, which was completed in 1997.[226] The Upper Reservoir was decommissioned as a part of the city's water supply system in 1993,[227][228] and was renamed after former U.S. first lady Jacqueline Kennedy Onassis the next year.[227][229] During the mid-1990s, the Conservancy hired additional volunteers and implemented a zone-based system of management throughout the park.[8] The Conservancy assumed much of the park's operations in early 1998.[23]