Examples of this kind of pollution include dairy waste ponds, food processing plants, and agrochemical processing plants. In contrast, NPS pollution consists of diffuse discharges of pollutants throughout the natural environment. Nonpoint sources of pollution, including erosion, and, to a lesser degree, animal nutrient production, occur naturally at certain levels. However, common management practices increase these types of pollution. Nonpoint source pollution from rangelands can be exacerbated by grazing, road building, mining and recreational activities.
Grazing can be a source of excessive sediment, nutrients, and pathogens.
Animal concentration in riparian areas allows the direct deposition of nutrients and pathogens in waterways, and can cause streambank erosion and sedimentation. Statewide and nationwide, sediment is considered to be the primary nonpoint pollution source on rangelands. However, in Marin County, because of the high concentration of livestock on dairies, animal waste is the greatest pollution concern from both point and nonpoint sources. The project area encompasses the watersheds of three major coastal streams north of San Francisco, within Marin County. The watersheds encompass approximately 232 sq. miles, or 148,480 acres, primarily in agricultural ownership.