Hiking - Human waste is often a major source of environmental impact from hiking. These wastes can contaminate the watershed and make other hikers ill. Bacterial contamination can be avoided by digging catholes 10 to 25 cm deep (4 to 10 inches, depending on local soil composition) and covering after use. If these catholes are dug at least 60 m (200 feet) away from water sources and trails, the risk of contamination is minimized.