BEST MANAGEMENT PRACTICES (aka BMPs)
3 General Types:
Some commonly seen BMP's in Hawaii (mainly on construction sites):
Silt fencing - small and large shown in photo.
Silt fencing (runoff prevention and filter) and gravel in construction
site entrance (filter and to loosen excess dirt from truck tires)
Hydroseed - sprayed on sticky fast-growing grass seeds
Storm drain filter - rolled up screen material similar to that used in
silt fences; sometimes sandbags are used
STRUCTURAL
PRACTICES:
Check Dam - Small temp. barrier, grade control structure or dam
constructed across a swale, drainage ditch or area of concentrated flow.
Minimize erosion rate by reducing the velocity of storm water in areas
of concentrated flow, and to capture larger soil particles.
Construction
Exit Stone - Stabilized pad located at any point where traffic will
be leaving a construction site to a public roadway. To reduce or eliminate
the transport of material from the construction area onto the public roadway.
Construction
Road Stabilization - Use of construction specifications, techniques,
and materials to stabilize soils on which a travel way is constructed
as part of a construction plan. To provide a fixed route for construction
traffic, and to reduce erosion and subsequent re-grading on permanent
roadbeds btwn. the time of initial grading and final stabilization.
Dewatering
Structure -Temporary structure for settling and/or filtering sediment
laden water that is discharged from dewatering activities. To settle and
filter sediment laden water prior to the water being discharged off-site.
Diversion
- Channel of compacted soil constructed above, across, or below a slope,
with a supporting earthen ridge on the lower side. To reduce the erosion
of steep, or otherwise highly erodible areas by reducing slope lengths,
intercepting storm runoff and diverting it to a stable outlet at a non-reosive
velocity or to convey storm water through a construction site.
Filter
Ring - Temporary stone barrier constructed at storm drain inlets.
Used to reduce flow velocities and prevent the failure of other sediment
control devices. Also prevents sediment from leaving site or entering
drainage systems, prior to permanent stabilization of the disturbed area.
Gabion
- Large, multi-celled, welded wire or rectangular wire mesh boxes, used
as channel revetments, retaining walls, abutments, check dams, etc. Rock-filled
baskets, properly wired together, to form flexible monolithic building
blocks used for construction of erosion control structures and to stabilize
steep slopes or highly erosive materials.
Geotextile
- Geosynthetic fabric, either woven or non-woven, applied to either the
soil surface or between materials. To reduce erosion by and sediment found
in, storm generated water by providing filtration, separation, or stabilization
properties.
Gradient
Treatment - Step or terrace feature created along the contour of steep
or long slopes. Stepped slopes prevent slope erosion and the formation
of rills or washes by decreasing runoff velocities, trapping sediment,
increasing infiltration of water into the soil and supporting the establishment
of vegetative cover.
Riprap
- Permanent, erosion-resistant ground cover of large, loose, angular
stones with a geotextile or granular underlining. Used to protect culvert
inlets and outlets, stabilize banks, stabilize drainage channels, and
protect slopes and other areas subject to erosion by storm water, where
vegetative or geotextile measures are not adequate or appropriate. Reduces
erosion and sediment movement.
Sediment
Basin - Temporary basin consists of an embankment constructed across
a drainage way, or of an excavation that creates a basin, or by a combination
of both. Typically consists of an impoundment, a dam, a riser pipe outlet
and an emergency spillway. Size will depend on the location, size of the
drainage area, soil type, land cover/use, rainfall amount, and any unique
site conditions favorable to producing high runoff volume, velocity or
sediment. Used to retain runoff waters and trap sediment from disturbed
areas to protect properties and waters below the installation from damage
by excessive sedimentation and debris. Water is temporarily stored and
the bulk of the sediment carried by the water falls out of suspension
and is retained in the basin, while the water is slowly released over
a period of time.
Sediment
Trap - Temporary ponding area formed by constructing an earthen embankment
with a stone outlet. To detain sediment laden runoff from small, disturbed
area long enough to allow the majority of the sediment to settle out.
Silt
Fence - Temporary sediment barrier made of woven, synthetic filtration
fabric supported by steel or wood posts. Prevent sediment carried by sheet
flow from leaving the site and entering natural drainage ways or storm
drainage systems by slowing storm water runoff and causing the deposition
of sediment at the structure. Encourages sheet flow and reduces the potential
for development of rill and gullies.
Slope
Drain - Temporary pipe installed from top to bottom of a cut or fill
slope. To convey storm water runoff down the face of a cut or fill slope
without causing erosion on or below the slope.
Storm
Drain Inlet Protection - Temporary protective device formed around
a storm drain inlet to trap sediment. To prevent sediment from entering
storm drainage systems, prior to temporary or permanent stabilization
of the disturbed area.
Storm
Drain Outlet Protection - Paved and/or riprapped channel treatment,
placed below storm drain outlets. Reduce storm water velocity and dissipate
the energy of flow leaving a storm drain before it empties into receiving
channels, and to armor erodible materials.
Surface
Roughening - Use of mechanized equipment to apply a rough texture
to soils at final grade. Technique used for creating unevenness on bare
soil to prevent slope erosion and the formation of rills. Functions are
to reduce erosion potential by decreasing runoff velocities, trap sediment,
increase filtration of water into the soil, aid in the establishment of
vegetative cover.
BACK TO TOP
Buffer
Zone - Strip of undisturbed, original vegetation, enhanced or restored
existing vegetation, or the re-establishment of vegetation surrounding
an area of disturbance or bordering streams, ponds, wetlands, or lakes.
Provide a buffer zone which can filter and infiltrate runoff, reduce storm
runoff velocities, protect channel banks from scour and erosion, provide
flood protection, cool rivers and streams by creating shade, provide food
and cover for wildlife and aquatic organisms, reduce construction noise,
and improve aesthetics on the disturbed land.
Disturbed
Area Stabilization (w/ mulch) - Applying hay, straw, mulch, plant
residues, or other suitable materials, produced on the site if possible,
to the soil surface. Reduce runoff and erosion, conserve moisture, promote
germination of seed, prevent surface compaction or crusting, protect seed
from birds, modify soil temperature, and increase biological activity
in the soil.
Disturbed
Area Stabilization (w/ permanent vegetation) - Planting of perennial
vegetation such as trees, shrubs, vines, grasses or legumes on exposed
areas for final permanent stabilization. Reduce storm water runoff velocity,
maintain sheet flow, protect the soil surface from erosion, promote infiltration
of runoff into the soil, improve wildlife habitat, and improve aesthetics.
Disturbed
Area Stabilization (w/ sod) - Permanent vegetative cover using sod
brought from locations off site. Establish immediate ground cover, reduce
storm water runoff, protect the soil surface from erosion, reduce damage
from sediment and runoff to downstream areas, and improve aesthetics.
Disturbed
Area Stabilization (w/ temporary vegetation) - Establishment of temporary
vegetative cover with fast growing species for seasonal protection on
disturbed or denuded areas. Reduce storm water runoff velocity, maintain
sheet flow, protect the soil surface from erosion, promote infiltration
of runoff into the soil, improve wildlife habitat, improve the soil condition
for permanent plantings, and improve aesthetics.
Erosion
Control Blanket/Matting - Protective blanket or soil stabilization
may used to assist in establishment of temporary or permanent vegetation
on steep slopes, channels, or stream banks. Prevent soil erosion of the
soil surface, promote seed germination, protect young vegetation, prevent
erosion of seed, prevent wind dispersal of seed or mulch, and allow for
easy installation of seed and/or mulch.
Polyacrylamide - Land application or storm water application of product containing anionic polyacrylamide (PAM). Land application of PAM is performed to reduce soil surface erosion due to wind and/or water forces. Promotes settling of fine soil particles in sediment basins.
Stream
Diversion Channel - Temporary channel constructed to convey stream
flow around in-stream construction. Used to allow in-stream work to be
conducted separate from flowing water.
Temporary Stream Crossing -Temporary structure installed across a flowing stream or watercourse for use by construction equipment. Provides a means for construction vehicles to cross streams or watercourses without moving sediment into the stream, damaging the streambed or channel or causing flooding.
Bioengineered
Stream Bank Stabilization - Use of readily available native plant
materials to maintain and enhance stream banks; or to prevent, or repair
and restore small stream bank erosion problems. Trap sediment from adjacent
land, form a root mat to stabilize and reinforce the soil on the stream
bank, provide wildlife habitat, enhance the appearance of the stream,
lower summertime water temperatures providing a healthy aquatic environment.
