The U.S. National Whitewater Center (USNWC) is a not-for-profit outdoor recreation and athletic training facility for whitewater rafting, kayaking, canoeing, rock climbing, mountain biking hiking and ice skating which opened to the public on 2006. The Center is located in Charlotte, North Carolina on approximately of land adjacent to the Catawba River, with more than of developed trail. The Center's primary feature is the world's largest and most complex recirculating artificial whitewater river. The river channels were designed by three-time Olympian Scott Shipley. Whitewater channels The Center's recirculating river is filled with 12 million gallons of water, which is cleaned every 24 hours by a filtration and ultraviolet system. The whitewater portion of the river has a total of of channel divided between two channels: the Olympic-standard slalom competition channel and the longer wilderness channel, which splits around an island at the top. The rapids are Class II to IV and can be navigated via canoe, kayak or a guided raft. The different channels are linked by an Upper and Lower Pool which are connected via a moving-belt boat-lift conveyor. The facility is equipped with a total of seven, 620 hp submersible pumps manufactured by Flygt. Each channel is watered by three of the pumps. Six pumps will water both channels simultaneously. The electricity cost of each pump is about US$45 per hour. When only one channel is used, a low pressure, air bag actuated, Obermyer Gate separates the top of either the Wilderness or Competition Channel from the upper pond thus preventing water from entering. Since both channels have the same drop, , the extra length of the Wilderness Channel gives it a gentler slope. Most of the water diverters are natural boulders cemented in place, but there is some use of moveable plastic bollards attached to the bottom. There are five barn door diverters hinged to the channel sides and positioned by hydraulic pistons, two above the M-Wave on the long channel, and three in the slalom competition channel. The M-Wave is designed to replicate the famous M-Wave in an irrigation channel near Montrose, Colorado. The Wilderness Channel has six named drops, Entrance Exam (class 2), Huey Lewis (class 2), Bread and Butter (class 2+), Sunset (class 3), and M-Wave (class 3+). The Competition Channel has two named drops, Bridge Drop (class 3), and Big Drop (class 4). Commonly kayak surfed waves on the Wilderness Channel include Entrance