How to Prevent Construction-Related Nonpoint Source Pollution

Best Management Practices

Methods and procedures that prevent or reduce pollution are known as best management practices (BMP). The following list of best management practices reduce construction-related nonpoint source pollution.

Sediment

• Diversion Dikes: Diversion dikes should be built at the upslope perimeter of the construction site to channel rain water away from the disturbed area. The diversion dikes should be built prior to any earth moving, and should be seeded and mulched immediately after they are built.
• Vegetative Buffer Strips: Of primary importance when construction sites are adjacent to water bodies, a buffer strip of undisturbed vegetation between the water body and the construction area reduces run-off water velocity and traps sediment. This reduces sediment delivery to surface waters and adjacent properties.
• Seeding and Mulching: Mulch should be applied to exposed soil at the end of each work day. Seed should be applied to topsoil stockpiles and bare soil after use of soil and disturbances to the soil have stopped.
• Hay Bale Dikes: Hay bale dikes are very cost effective as short-term sediment traps. They can be located across slopes, at the foot of slopes, along stream banks, and in small drainage ditches that occasionally carry sediment-laden water.
• Silt Fencing: Sediment fencing is temporary filter-cloth fencing that is used to catch sediment-laden run-off from small areas of soil disturbance. This usually reduces run-off velocity to a degree favorable for sediment deposition.
• Vegetative Cover: Natural vegetation controls erosion in several ways. It protects the soil surface from the impact of falling rain and decreases the velocity of run-off. It helps maintain the soil's capacity to absorb water and holds soil particles in place. A construction planner can significantly reduce soil erosion and sedimentation by limiting the removal of vegetation. If removal is necessary, it should be done in stages to decrease the duration of soil exposure. Vegetation should be retained in areas of moderate to high soil erosion potential, such as steep slopes, drainage ways, highly erodible soils, and stream banks.
• Sediment Basin: A sediment basin is a temporary dam constructed across a drainageway to intercept and retain sediment and other waterborne debris. It provides a temporary means of detaining sediment-laden run-off long enough for the majority of sediment to settle out. Special consideration needs to be given on depth of water table when this practice is used in order to ensure that infiltration of pollutants do not contaminate ground water aquifers.
• Sediment Trap: A sediment trap is a small temporary ponding area formed by constructing an earthen embankment to intercept sediment-laden run-off from a small disturbed area long enough to trap and retain it to settle out. This practice should be installed at points of discharge from disturbed areas for a maximum period of 18 months. Special consideration needs to be given on depth of water table when this practice is used in order to ensure that infiltration of pollutants do not contaminate groundwater aquifers.