Francis turbine Units 19, 20, and 21, installed at the Grand Coulee Dam on the Columbia River, are very large [55]. Each runner is \(32.6 \mathrm{ft}\) in diameter and contains 550 tons of cast steel. At rated conditions, each turbine develops \(820,000 \mathrm{hp}\) at \(72 \mathrm{rpm}\) under \(285 \mathrm{ft}\) of head. Efficiency is nearly 95 percent at rated conditions. The turbines operate at heads from 220 to \(355 \mathrm{ft}\). Calculate the specific speed at rated operating conditions. Estimate the maximum water flow rate through each turbine.