Failing home septic systems can allow coliforms in the effluent to flow into the water table, aquifers, drainage ditches and nearby surface waters.  Sewage connections that are connected to storm drain pipes can also allow human sewage into surface waters.  Some older industrial cities, particularly in the Northeast and Midwest of the United States, use a combined sewer system to handle waste.  A combined sewer carries both domestic sewage and stormwater. During high rainfall periods, a combined sewer can become overloaded and overflow to a nearby stream or river, bypassing treatment.