Slide 72 of 87
Notes:
Most non-stormwater discharges are strictly governed under the National Pollutant Discharge Elimination System (NPDES) and require a state or federal permit. The three basic kinds of non-stormwater discharges in a subwatershed are:
1) Septic Systems (on-site sewage disposal systems) are used to treat and discharge wastewater from toilets, wash basins, bathtubs, washing machines, and other water consumptive items that can be sources of high pollutant loads. One out of four homes in the country uses a septic system, collectively discharging a trillion gallons of wastewater annually (NSFC, 1995). Unlike other non-stormwater discharges, septic systems are not regulated under NPDES, but are approved by local and state health agencies.
2) Sanitary sewers collect wastewater in a central sewer pipe and send it to a municipal treatment plant. Ideally, this permits more efficient collection of wastewater, and often higher levels of pollutant reduction. The extension of sanitary sewer lines is not without some risk, however, as it has the potential to induce more development than may have been possible in a watershed previously served only by on-site sewage disposal systems (particularly when soils are limiting). In addition, not all sanitary sewer conveyance and treatment systems are capable of achieving high levels of pollutant reduction.
3) Other A planner should also investigate whether other non-stormwater discharges are a factor in the subwatershed. Examples include industrial NPDES discharges, urban "return flows" (discharges caused by activities such as car washing and watering lawns), water diversions, and runoff from confined animal feeding lots.