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 summer of 1996 for reducing point source and nonpoint source loads of nitrogen to the Neuse River by
30 percent in five years. In order to achieve this 30 percent reduction, mandated solutions are
proposed for different pollution sources. For agriculture, the following combination of BMPs may be
required: 1) nutrient management and controlled drainage or 2) nutrient management or controlled
drainage and a forested riparian buffer or vegetative filter, or 3) forested riparian buffers and vegetative
filter strips when controlled drainage and nutrient management are not utilized (NCDWQ, 1996). These
regulations proposed the reestablishment of riparian buffers along both sides of perennial and
intermittent surface waters in the Neuse River basin, exclusive of ditches.
4.2.2 TECHNOLOGICAL DESCRIPTIONS
A BMP system is often required to effectively control NPS pollution, especially when the
critical pollutant source involves an animal operation. Most animal operations require a combination of
BMPs such as waste handling and manure application. Other BMPs may be needed to divert clean
water away from the site as well as feedlot runoff control. Cropland BMP systems may include terraces
and grassed waterways along with cover crops and conservation tillage.
4.2.2.1 Best Management Practice Systems
BMP systems that include a structure are very common for animal waste and cropland
treatment. Structures include holding ponds, pits, lagoons, dry stacks, sediment basins, and detention
ponds are often necessary to control pollution from farmsteads and fields; however, these structures do
not achieve maximum effectiveness in isolation. To maximize the effectiveness of a structure, they must
be combined with management practices such as waste utilization, nutrient management, or erosion
control.
Nutrient and pesticide management are, in general, the most cost-effective BMPs in terms of
requiring the least monetary investment for the greatest water quality benefit.
Sediment. Soil particles are detached by raindrop energy, overland flow, or wind energy. The
erosion of soil particles is a natural geologic process, but it can become accelerated when the soil
surface becomes exposed. Sediment loss can be reduced by BMPs that minimize exposure of the soil
and soil particle detachment. Such practices include conservation crop rotations, cover crops, and
conservation tillage. These BMPs improve soil structure and increase soil organic matter content and
surface roughness. Where permanent gullies form in a field, a grassed waterway can be used to reduce
gully erosion and provide a stable channel to divert runoff.
To minimize the transport of sediment there are several BMPs that reduce slope length and
steepness or water velocity. Stripcropping, terraces, and contour plowing or row arrangement serves to
reduce the slope length and reduce sediment transport. Field borders, filter strips, and level spreaders
4.2-2
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