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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 runoff, and will prevent any surface runoff from flowing into the street storm drain system. Paved driveways should be designed, installed and paved by qualified professionals.
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. Dry wells, stone- 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.
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. Retaining structures should be used for slope stabilization only. Terraces, steps and other techniques which destabilize slopes or require movement of large amounts of soil should not be used. 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.