Now the two cities have chewed through a buffer zone up to the dairy doorstep. Daily, they also produce 15 million gallons of washwater - water that rinses cows before milking and also cleanses milking equipment and the barn. That muck has become a bigger burden as dairies squeeze more cows on less land and homeowners live within sight and sniffing distance. Today, at some dairies, manure piles look like mini foothills and cows slosh belly-deep in dung. Geography and development have complicated control of manure and washwater, both of which could be used as fertilizer, except that there isn't enough farmland around to absorb it.
Most dairies here sit near the bottom of a gradual mountain slope.
Those dirty flows can reach the Santa Ana River, which ultimately replenishes much of Orange County's drinking water. The chief problems are salt and nitrates, two byproducts of cow waste that can leach into groundwater. In fairness, long-gone citrus groves also left agricultural residue. Close to 300 dairies and 320,000 cows live around the developing cities of Chino and Ontario in Southern California. By and large, no.