The sandhogs are mining a new water channel, City Water Tunnel #3, to meet the growing demands of the metropolis, and to prevent any catastrophic water shortages in the future.

Earlier generations of sandhogs in the early 1900s built the city's first two water tunnels, which originate upstate at the Croton and Delaware reservoirs and provide the city with most of the 1.3 billion gallons of water used daily. Those tunnels are now leaking heavily in many areas, quite vulnerable to cave-ins, and other technical failures. In order to inspect and repair the older tunnels, which would be a first-time maintenance since they were activated, and to guarantee fresh water supply to the city, Water Tunnel #3 must be completed.

The tunnel is the largest capital project in New York's history, designed and operated by the Department of Environmental Protection. The "hogs" began construction on Tunnel #3 in 1969, and it will not be finished until 2012. Originating at Kensico Reservoir in the Catskills, once finished the new tunnel will be sixty miles long and deliver one billion gallons of water a day to the city.