Erosion & Sedimentation Best Management Practices

Minimizing erosion and sedimentation to protect, maintain and restore water quality

E&S BMPs are activities, facilities, measures planning or procedures used to minimize accelerated erosion and sedimentation to protect, maintain and restore the quality of waters and the existing and designated uses of waters within the Commonwealth during earth disturbance activities.

Definitions:

Silt Sock

Compost filter socks are a type of contained compost filter berm. They consist of a biodegradable or photodegradable mesh tube filled, typically using a pneumatic blower, with a coarse compost filter media. Compost filter socks are flexible and can be filled in place or in some cases filled and moved into position. They are especially useful on steep slopes. Heavy vegetation should be removed prior to installing the sock. Compost socks can also be used on rocky slopes if sufficient preparation is made to ensure good contact of the sock with the underlying soil along its entire length. They may also be used on pavement as a perimeter control.

Silt Fence

Silt fence may be used to control runoff from small disturbed areas when it is in the form of sheet flow, and the discharge is to a stable area. Only those fabric types specified for such use by the manufacturer should be used. In order to provide sufficient fabric for proper anchoring of the fence, standard filter fabric width should be 30” min.; reinforced and super filter fabric width should be 42” min.

Straw Mulch

Mulches absorb rainfall impact, increase the rate of infiltration, reduce soil moisture loss due to evaporation, moderate soil temperatures, provide a suitable environment for germination, and protect the seedling from intense sunlight. All seeded areas should be mulched or blanketed to minimize the potential for failure to establish an adequate vegetative cover. Mulching may also be used as a temporary stabilization of some disturbed areas in non-germinating seasons.

Erosion Control Blankets

There are many varieties of erosion control blankets on the market. They range from rolls of natural and artificial materials, which are typically installed by hand, to liquid, spray-on, materials that make use of a bonding agent to hold natural or artificial fibers in place until vegetation becomes established. Erosion control blankets should be used on all slopes that are 3H:1V or steeper and where potential exists for sediment pollution to receiving surface waters. Since rock slopes pose little, if any, potential for erosion, cut slopes in competent bedrock and rock fill slopes need not be blanketed. Erosion control blankets should be used for all seeded areas within 50 feet of a surface water — 100 feet of a special protection water — regardless of slope.

Sediment Trap

Sediment Traps may be designed to function as temporary facilities, or incorporated into the Stormwater Management System upon completion of the project. In the latter case, the trap should be dewatered, cleaned, and stabilized prior to its conversion to a detention pond.Wherever possible, sediment traps should be located below all proposed areas of disturbance. Locating traps within proposed grading areas typically results in a major portion of the earthmoving taking place without benefit of the trap being in place that was designed to handle runoff from thedisturbed areas.

Rock Construction Entrance

A rock construction entrance should be installed wherever it is anticipated that construction traffic will exit the project site onto any roadway, public or private. Access to the site should be limited to the stabilized construction entrance(s). A geotextile underlayment should be placed over the existing ground prior to placing the stone

Inlet Filter Bag

Filter bags should be capable of trapping all particles not passing a No.40 Sieve. Wherever filter bags are used they should be installed according to the manufacturer’s specifications. Filter bags designed to fit over the inlet grate are not recommended for most storm sewer inlets. Use of such filter bags could result in a severe reduction of the inlet capacity resulting in flooding or runoff bypassing the inlet. Wherever such bags are used, they should be located at topographic low points and limited to ¼ acre maximum drainage areas. Inlet filter bags are not acceptable as the primary BMP to remove sediment from site runoff water.

Vegetative Stabilization

All disturbed areas that have not otherwise been stabilized and have significant potential for erosion should be stabilized with vegetation. This includes graded areas where it is anticipated that future earthmoving will take place within the coming year. Areas that will be subject to earthmoving within 12 months may be stabilized with temporary seed mixtures, predominantly annual grasses. All others should be stabilized with permanent seed mixtures — predominantly perennial grasses. When final grade is achieved during non-germinating months, the area should be mulched until the beginning of the next planting season. However, the area will not be considered stabilized until a minimum uniform 70% vegetative cover of erosion resistant perennial species has been achieved. Critical areas —erodible soils, within 50 feet of a surface water, etc. — should be blanketed. Temporary erosion control BMPs that were installed for the earthmoving phase of the project must remain in place and be maintained in working order until permanent stabilization is achieved.