Best Management Practices (BMPs) are proven methods that prevent sediment and nutrients from entering our surface waters. By implementing BMPs, all property owners can help slow or reverse the loss of lake clarity. According to the recently published Lake Tahoe Watershed Assessment, scientists have determined that implementing BMPs on existing development is one of the most critical steps toward improving water quality.
BMPs prescribed for residential and commerical properties may include:
Paving dirt driveways and roads.
A paved driveway is one of the most effective BMPs a homeowner can implement. Storm water flows right off a compacted dirt driveway. Also, vehicle tires, snow removal,and other disturbances carry dirt from unpaved driveways into the street storm drain system. Soil erosion and storm water runoff can be controlled with a properly designed paved driveway. Driveways should be designed to preserve natural vegetation and to blend with the natural landform. Slotted drains or other flow interceptors may be needed to convey surface runoff to infiltration structures or stabilized drainage areas, usually at the driveway edge. Properly designed paved driveways will collect and, ideally, infiltrate sheet flow runoff and will prevent any surface runoff from flowing into the streets and drainages. Paved driveways should be designed and installed by qualified professionals.
Infiltrating stormwater runoff from impervious surfaces.
Whenever possible, naturally vegetated areas should be protected and used for infiltration. The natural plant-soil complex can treat runoff better than any artificial infiltration system. Artificial systems must be used along impervious surfaces and driplines when natural vegetation isn’t present or is inadequate to infiltrate all the flow. Infiltration systems allow water to percolate through the soil, a process which filters and cleanses surface runoff of sediment and nutrients before it is discharged into rivers, streams and lakes as groundwater. An infiltration trench is a shallow rock- or gravel-filled trench located at drip lines or adjacent to other impervious surfaces where runoff collects or concentrates. Dry wells, sone- or gravel-filled pits, or French Drains are used when additional storage capacity for runoff is needed or as alternatives to infiltration trenches on steeper slopes.
Infiltration facilities shall be designed to accommodate the volume from a twenty year, one hour storm. An average intensity of 1 inch per hour can be used for this calculation. Infiltration facilities shall be designed utilizing the methodology set forth in the BMP Handbook. The bottom of infiltration trenches or dry wells shall be a minimum of one foot above the seasonal high water table
Stabilizing or retaining steep slopes and loose soils.
A retaining structure is a wall or other structure placed at the
bottom of an oversteepened slope to prevent erosion. Retaining structures,
including terraces, steps and other landscaping techniques, can be made of wood,
rock, brick, or concrete block.
The use of native vegetation along the top of and around retaining structures can increase the structure’s effectiveness. Vegetation alone and rock rip-rap (a layer of loose rock placed on an erodible surface) are also effective slope stabilization techniques. Implementation of this BMP may require a permit from TRPA or your local building department, depending on the height of the structure and the amount of soil to be moved. Staff people from those agencies will be happy to help determine whether a permit is needed.
Vegetating and mulching bare soils.
Vegetation stabilizes soil, reduces raindrop impact, reduces velocity of surface runoff, prevents wind and water erosion, and enhances natural beauty. A relatively simple plan to plant native grasses, shrubs and other plants can be a highly effective BMP. Lists of approved plant species are available from TRPA, you local Resource Conservation District, and the Nevada Cooperative Extension.
The use of native and adapted plants is a Best Management Practice because those species require less fertilizer and irrigation than other species. Fertilizer application must be carefully managed to prevent excess plant nutrients from reaching surface and groundwater. Irrigation must be monitored to prevent overwatering and added surface runoff. Wood chip and bark mulches may be used for temporary stabilization or as permanent ground cover and round trees and shrubs.