Appius Claudius Caecus (c. 340 cE-273 всЕ) Sometimes a group of people have big, pressing needs that can be solved by engineering. Such was the case in ancient Rome, and the problem was the water supply. The year is approximately 300вс and Rome is growing. But the water supply stinks. Literally. Water from underground has a bad taste, and water from the Tiber River is loaded with pathogens. To solve the problem, Roman engineers commissioned by censor Appius Claudius Caccus developed aqueducts. The first one, called Aqua Appia, is a perfect example. The engineers found a large, clean spring about 10 miles (16 km) outside Rome. Located at a higher elevation than Rome, gravity could do the work of moving the water toward the city. Roman engineers cut trenches or dug tunnels (often through solid rock) and then lined them with waterproof mortar. If a valley got in the way, the engineers built a bridge to carry the channel. The channel sloped gently downward all the way to the city. What to do about mud and sediment in the water? The water flowed slowly through wide, deep pools so particles could settle out. How to maintain the tunnels and clean them out? Vertical shafts connected the tunnels to the surface. What if too much water surged through the system? The tunnels had overflow vents to drain away extra water. The Aqua Appia aqueduct is thought to have delivered 20 million gallons (76 million liters) of water per day to Rome. Once inside the city, the water from an aqueduct could flow into large, elaborate public fountains, to public baths, into pipe systems to residences, or into the sewer system. The sewers carried waste out of the city and kept Rome remarkably clean. Even with 20 million gallons of water a day, Rome outgrew the supply. So the engineers built more aqueducts. Over the course of five hundred years, there were eleven aqueducts feeding Rome, the longest one stretching 56 miles (90 km). The entire system brought perhaps 300 million gallons (1.1 billion liters) of water per day to over a million people. It was an amazing achievement and it led to later innovations such as the modern sewer system.