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Nonpoint Source Pollution
Best Management Practices

What Are BMPs?

Best management practices (BMPs) are structural devices, systems and procedures developed over time to help control or manage operations. For example, there may be a set of BMPs to cover dam construction or coal mining.

Historically, however, BMPs have been associated with pollution control. As the past lead nonpoint source (NPS) pollution control agency of Virginia and the cost-share manager for state funded agricutultural BMPs, the Department of Conservation and Recreation (DCR) has been heavily involved in the development, research, demonstration and promotion of NPS BMPs over the past few decades. DCR has the primary responsibilities for many of these programs, legal issues and law enforcement, and policy development.

NPS BMPs are devices, systems and procedures that reduce or eliminate NPS pollutants from harming the environment, particularly to water features. Conservation officials estimate that most of the pollution that degrades water quality in Virginia’s streams, lakes, reservoirs and bays comes from nonpoint sources.

NPS BMPs are often grouped by the type of land use from which the NPS pollutants originate. This includes:

  • Urban BMPs.
  • Agricultural BMPs.
  • Forestry BMPs.
  • Other lesser sources.

Urban NPS BMPs

Urban NPS BMPs are often installed or practiced for the control of stormwater. Such BMPs include retention ponds, silt fences and rain gardens. Thus they are increasingly referred to as Stormwater Treatment Practices. These BMPs are best installed during construction, but some may be retrofitted to old development or provide long term stormwater control benefits beyond the actual construction disturbances. Other urban BMPs may be instituted to alleviate the effects to water quality from everyday urban living, such as cleaning streets of the litter, dirt and toxics that accumulate on them before they go into storm drains. This is referred to as source control, because it removes trash and pollutants at their source, before storm runoff washes them into streams.

Agricultural NPS BMPs

Approximately 25 percent of Virginia’s land area is used for some kind of agricultural activity. Many of these activities can be the source of significant amounts of nutrient (phosphorus and nitrogen), sediment, pathogen and pesticide pollution to water features in Virginia. Agricultural uses are believed to be the single biggest contributor of nutrient and sediment loadings to state waters.

Accordingly DCR and other conservation partners in the state, including the U.S.D.A. and Soil and Water Conservation Districts, spend a large portion of their time and budgets installing, promoting and tracking agricultural NPS BMPs. These include practices to control cropland runoff, animal waste dispersal, streambank erosion, improper use of fertilizers and pesticides, and other NPS pollutant reduction actions. This is accomplished by constructing control devices such as riparian buffers, diversions, grass filter strips, animal waste control facilities, animal carcass incinerators, stream exclusion fencing, and chemical and fertilizer handling facilities. It is also accomplished through activities such as rotational grazing, planting of cover crops, capping of abandoned wells, practicing integrated pest management, nutrient management plan implementation and other similar proven actions.

Among the many agricultural NPS BMP promotional and funding assistance programs available in the state are the:

Forestry NPS BMPs

Forestry BMPs primarily consist of devices and actions that reduce or eliminate soil erosion arising from forest clearing, tree removal and stream crossings. This can include incentives to leave land as forest and to practice wise harvesting and land preparation. It can also include efforts to protect trees from disease and insects that might cause forest clearing. The spraying of pesticides is therefore also a concern that is addressed.

Forest land dominates Virginia’s landscape, constituting about two-thirds of the land area, but is the least polluting when left undisturbed. Forestry NPS BMPs are promoted and financially assisted by federal and state programs, including:

  • U.S.D.A. Reforestation of Timberlands (RT).
  • Virginia Forest Land Enhancement Program (FLEP).
  • U.S.D.A. EQIP.

Other NPS BMPs

NPS BMPs related to on-site waste disposal systems are not so land-use specific in that they are needed and occur wherever septic systems are installed and used. These BMPs primarily consist of actions to maintain the systems, which historically are not maintained, repair or replace those that have failed, or install an alternative system when necessary.

Another area NPS BMPs are utilized is in the reclamation of abandoned or recently active mining activities, thereby reducing erosion and sedimentation of nearby water features.

NPS BMP Effectiveness

The effectiveness of a NPS BMP is a measure of how well it reduces the NPS pollutant production or delivery to water features. Optimal effectiveness is obtained only through the controlled construction and installation of the practice’s structural device, or the precision undertaking of the practice procedure, in accordance with the BMP’s design specifications. Specific practice guidelines can be found, per NPS BMP, in the Virginia Agricultural BMP Cost Share Manual for BMPs that qualify for Virginia’s Cost-Share, CREP and BMP Tax Credit Programs. Similar specifications exist for acceptance into the federal funding programs.

Even when constructed, installed or practiced as per specifications, the effectiveness of NPS BMPs will vary by location owing to each sites’ particular conditions, including weather, soil type, slope, wildlife, stream size and other unique site-specific characteristics. Likewise the effectiveness of a particular NPS BMP will vary over time for a number of reasons, such as weather, land use change and level of maintenance. Therefore only rough averages of effectiveness for regional areas are possible. Many of the NPS BMPs in Virginia must be assigned an effectiveness based on limited evaluations and model simulations because the amount of water quality monitoring that would otherwise be needed is cost prohibitive. DCR typically uses values that have been calculated through its involvement with the EPA Chesapeake Bay Program modeling efforts.

Cost-effectiveness can be measured by associating reductions expected per NPS BMP with the cost to implement the practice. This could be done for the total costs or for the funding agency’s portion of that cost.

DCR tracks each BMP in the CREP, Cost-Share and Tax Credit programs in an agricultural BMP database. This database contains much of the information needed to estimate reductions produced by BMPs, either singly or summed by watersheds. Using a stored design lifespan for each BMP, it is also possible to estimate reductions over time or occurring at any specific time. Every practice has an expected design lifespan – a period of time after implementation in which NPS reduction should continue.

The agricultural BMP database can also help officials determine who participates in these programs, compare the acceptance of BMP types across the state, avoid duplication of effort, show areas lacking controls, track finances and provide many other useful insights into role of NPS BMPs and the success of the programs that promote them. You can query this database here.