government regulation. agricultural operations account for a large percentage of all nonpoint source pollution in the united states. when large tracts of land are plowed to grow crops, it exposes and loosens soil that was once buried. this makes the exposed soil more vulnerable to erosion during rainstorms. it also can increase the amount of fertilizer and pesticides carried into nearby bodies of water. atmospheric inputs atmospheric deposition is a source of inorganic and organic constituents because these constituents are transported from sources of air pollution to receptors on the ground. typically, industrial facilities, like factories, emit air pollution via a smokestack. although this is a point source, due to the distributional nature, long-range transport, and multiple sources of the pollution, it can be considered as nonpoint source in the depositional area. atmospheric inputs that affect runoff quality may come from dry deposition between storm events and wet deposition during storm events. the effects of vehicular traffic on the wet and dry deposition that occurs on or near highways, roadways, and parking areas creates uncertainties in the magnitudes of various atmospheric sources in runoff. existing networks that use protocols sufficient to quantify these concentrations and loads do not measure many of the constituents of interest and these networks are too sparse to provide good deposition estimates at a local scale highway runoff highway runoff accounts for a small but widespread percentage of all nonpoint source pollution. harned (1988) estimated that runoff loads were composed of atmospheric fallout (9%), vehicle deposition (25%) and highway maintenance materials (67%) he also estimated that about 9 percent of these loads were reentrained in the atmosphere. forestry and mining operations forestry and mining operations can have significant inputs to nonpoint source pollution. forestry forestry operations reduce the number of trees in a given area, thus reducing the oxygen levels in that area as well. this action, coupled with the heavy machinery (harvesters, etc.) rolling over the soil increases the risk of erosion. mining active mining operations are considered point sources, however runoff from abandoned mining operations contribute to nonpoint source pollution. in strip mining operations, the top of the mountain is removed to expose the desired ore. if this area is not properly reclaimed once the mining has finished, soil erosion can occur. additionally, there can be chemical reactions with the air and newly exposed rock to create acidic runoff. water that seeps out of abandoned subsurface mines can also be highly acidic. this can seep into the nearest body of water and change the ph in the aquatic environment. marinas and boating activities chemicals used for boat maintenance, like paint, solvents, and oils find their way into water through runoff. additionally, spilling fuels or leaking fuels directly into the water from boats contribute to nonpoint source pollution. nutrient and bacteria levels are increased by poorly maintained sanitary waste receptacles on the boat and pump-out stations. control (for water pollution) main articles: agricultural wastewater treatment and erosion control contour buffer strips used to retain soil and reduce erosion urban and suburban areas to control nonpoint source pollution, many different approaches can be undertaken in both urban and suburban areas. buffer strips provide a barrier of grass in between impervious paving material like parking lots and roads, and the closest body of water. this allows the soil to absorb any pollution before it enters the local aquatic system. retention ponds can be built in drainage areas to create an aquatic buffer between runoff pollution and the aquatic environment. runoff and storm water drain into the retention pond allowing for the contaminants to settle out and become trapped in the pond. the use of porous pavement allows for rain and storm water to drain into the ground beneath the pavement, reducing the amount of runoff that drains directly into the water body. restoration methods such as constructing wetlands are also used to slow runoff as well as absorb contamination. construction sites typically implement simple measures to reduce pollution and runoff. firstly, sediment or silt fences are erected around construction sites to reduce the amount of sediment and large material draining into the nearby water body. secondly, laying grass or straw along the border of construction sites also work to reduce nonpoint source pollution. in areas served by single-home septic systems, local government regulations can force septic system maintenance to ensure compliance with water quality standards. in washington (state), a novel approach was developed through a creation of a "shellfish protection district" when either a commercial or recreational shellfish bed is downgraded because of ongoing nonpoint source pollution. the shellfish protection district is a geographic area designated by a county to protect water quality and tideland resources, and provides a mechanism to generate local funds for water quality services to control nonpoint sources of pollution. at least two shellfish protection districts in south puget sound have instituted septic system operation and maintenance requirements with program fees tied directly to property taxes. agricultural operations to control sediment and runoff, farmers may utilize erosion controls to reduce runoff flows and retain soil on their fields. common techniques include contour plowing, crop mulching, crop rotation, planting perennial crops or installing riparian buffers.: pp. 4-95–4-96 conservation tillage is a concept used to reduce runoff while planting a new crop. the farmer leaves some crop reside from the previous planting in the ground to help prevent runoff during the planting process. nutrients are typically applied to farmland as commercial fertilizer; animal manure; or spraying of municipal or industrial wastewater (effluent) or sludge. nutrients may also enter runoff from crop residues, irrigation water, wildlife, and atmospheric deposition.: p. 2–9 farmers can develop and implement nutrient management plans to reduce excess application of nutrients.: pp. 4-37–4-38 to minimize pesticide impacts, farmers may use integrated pest management (ipm) techniques (which can include biological pest control) to maintain control over pests, reduce reliance on chemical pesticides, and protect water quality. forestry operations with a well-planned placement of both logging trails, also called skid trails, can reduce the amount of sediment generated. by planning the trails location as far away from the logging activity as possible as well as contouring the trails with the land, it can reduce the amount of loose sediment in the runoff. additionally, by replanting trees on the land after logging, it provides a structure for the soil to regain stability as well as replaces the logged environment. marinas installing shut off valves on fuel pumps at a marina dock can help reduce the amount of spillover into the water. additionally, pump-out stations that are easily accessible to boaters in a marina can provide a clean place in which to dispose of sanitary waste without dumping it directly into the water. finally, something as simple as having trash containers around a marina can prevent larger objects entering the water. country examples united states nonpoint source pollution is the leading cause of water pollution in the united states today, with polluted runoff from agriculture and hydromodification the primary sources.: 15 regulation of nonpoint source pollution in the united states the definition of a nonpoint source is addressed under the u.s. clean water act as interpreted by the u.s. environmental protection agency (epa). the law does not provide for direct federal regulation of nonpoint sources, but state and local governments may do so pursuant to state laws. for example, many states have taken the steps to implement their own management programs for places such as their coastlines, all of which have to be approved by the national oceanic and atmospheric administration and the epa. the goals of these programs and those alike are to create foundations that encourage statewide pollution reduction by growing and improving systems that already exist. programs within these state and local governments look to best management practices (bmps) in order to accomplish their goals of finding the least costly method to reduce the greatest amount of pollution. bmps can be implemented for both agricultural and urban runoff, and can also be either structural or nonstructural methods. federal agencies, including epa and the natural resources conservation service, have approved and provided a list of commonly used bmps for the many different categories of nonpoint source pollution. u.s. clean water act provisions for states congress authorized the cwa section 319 grant program in 1987. grants are provided to states, territories, and tribes in order to encourage implementation and further development in policy. the law requires all states to operate nps management programs. epa requires regular program updates in order to effectively manage the ever-changing nature of their waters, and to ensure effective use of the 319 grant funds and resources. the coastal zone act reauthorization amendments (czara) of 1990 created a program under the coastal zone management act that mandates development of nonpoint source pollution management measures in states with coastal waters. czara requires states with coastlines to implement management measures to remediate water pollution, and to make sure that the product of these measures is implementation as opposed to adoption.