Best Management Practices. Structural Measures – Level IB: Advanced Fundamentals Education and Certification for Persons Involved in Land Disturbing Activities. Issued May 2009. The Manual for Erosion and Sediment Control In Georgia. Referred to as the Manual or Green Book
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Issued May 2009
Updates to the Manual can be found on GSWCC’s website at www.gaswcc.georgia.gov under
Programs Urban LandsNew Updates to the Manual for Erosion and Sediment Control
Vegetative measures & structural measures
Properly designed, installed, & maintained in accordance with specification in the Manual for E&S Control
Provide effective erosion prevention & sedimentation control
A small temporary barrier constructed across a swale, drainage ditch, or area of concentrated flow
Not to be used in a live stream
There is no formal design. The following standards
shall be used:
Drainage area shall not exceed
Two (2) acres for stone check dams
One (1) acre for hay bales
Height - the center of the check dam must be at least 9 inches lower than outer edge. Height should be 2 feet maximum measured to center of check dam.
How to Compute L:
L = Height of Cd / Slope as decimal
Improving, constructing, or stabilizing an open channel or waterway
Prevent erosion and sediment deposition
Provide adequate capacity for flood water, drainage, or other water management practices
Typical linings include vegetation, riprap, and concrete
Lining selection depends on the velocities within the channel
Vegetative lining shall be established using erosion control blankets or matting or sod
For Design Velocity
0 - 5 Ft/Sec Vegetation (Ds3, Ds4, Mb)
5 - 10 Ft/Sec Rock Riprap (Appendix C)
> 10 Ft/Sec Concrete
Grade stabilization structures may be needed to reduce velocities
Stone stabilized pad located at any point where traffic will be leaving a construction site to enter a public right-of-way, street, alley, sidewalk or parking area.
To reduce or eliminate the transport of mud from construction area.
No formal design. The following standards shall be used:
Aggregate size – stone in accordance with National Stone Association R-2 (1.5 to 3.5 inch stone)
Pad thickness – gravel pad minimum thickness of 6 inches
Pad width – minimum width should equal full width of all points of vehicular egress, but not less than 20 feet wide
Pad length – minimum of 50 feet
Washing - Wash tires if action of vehicles over gravel does not remove sediment. Divert tire washing to proper area
Travelway constructed as part of the construction plan including access roads, subdivision roads, parking areas, and other on-site vehicle transportation routes
6” coarse aggregate applied immediately after grading
Geotextile applied for additional stability
Grades should be < 10% for slope lengths less than 200 ft
14 ft for one-way traffic
20 ft for two-way traffic
24 ft for trailer traffic
A temporary channel constructed to convey flow around a construction site while a permanent structure is being constructed within a streambed.
To protect the stream channel from erosion and allows work “in the dry”.
Drainage areas < 1 square mile (640 acres)
Bottom width shall be a minimum of 6 feet or equal to the bottom width of the existing streambed, whichever is greater
Side slopes shall be no steeper than 2:1
Table 6-12.1 gives channel linings and acceptable velocities. Note differences from channel stabilization.
Stream Diversion Channel Linings
Lining MaterialAcceptable Velocity
Geotextile/ 0 - 2.5 fpspolyethylene
film or sod
Geotextile alone 2.5 - 9.0 fps
Type 1 Riprap & 9.0 - 13.0 fps Geotextile
A ridge of compacted soil, constructed above, across, or below a slope to safely convey runoff to a stable outlet
To reduce the erosion of steep or otherwise highly erodible areas by reducing slope length, intercepting storm runoff and diverting it to a stable outlet at a non-erosive velocity.
Location determined by outlet conditions, topography, land use, soil type, length of slope, seep planes, and the development layout
A diversion consists of two components:
Ridge Design – have stable side slopes, no steeper than 2:1 and minimum width of 4 ft at the design water elevation after settlement. Design shall allow 10% for settlement
Channel Design – Land slope must be taken into consideration
Selection of design storm based on type of diversion
to be used
A temporary structure used to convey concentrated storm water down the face of cut or fill slopes.
To safely conduct storm runoff from one elevation to another without causing slope erosion and allowing the establishment of vegetation on the slope.
There is no formal design. The following standards shall be
Placement – located on undisturbed soil or well compacted fill
Diameter – provide sufficient capacity required to convey the max runoff expected during the life of the drain
Sized according to its contributing drainage area
* 0.3 Ac = 10 in. * 0.5 Ac. = 12 in.
* 1.0 Ac. = 18 in.
Commonly used in conjunction with Diversions (Di)
Removed once the permanent storm water disposal system is installed and functioning
Storm drain outlet protection (St), shall be placed at the downdrain outlet
Anchored every 10 ft
Outlet protection and lined channel
A permanent structure used to safely convey surface runoff from the top of the slope to the bottom of the slope.
Minimize erosion due to concentrated storm runoff on cut of fill slopes
May be constructed of concrete, pipe, pre-fabricated sectional conduit or other adequate materials
Should be designed by professionals familiar with these structures
All structures shall satisfy GDOT Standards and Specs
Shall safely convey the 25-yr, 24-hr storm
Outlets must be stabilized
A temporary stone barrier constructed at storm drain inlets and pond outlets.
Reduces flow velocities, preventing the failure of other sediment control devices. Prevents sediment from leaving the site or entering drainage systems, prior to permanent stabilization.
There is no formal design. The following standards shall be
Location- Shall surround all sides of the structure receiving runoff and should be placed no less than 4 ft. from the structure. When placed in front of a retrofit it should be placed no less than 8-10 ft. from the retrofit
Stone Size – Constructed of stone no smaller than
3-5 inches in diameter for inlets with diameters less than 12 inches
10-15 inches in diameter for pipes with diameters greater than 12 inches
Height – no less than two feet from grade
Gabions are large, multi-celled, welded wire or
rectangular wire mesh boxes, used in channel
revetments, retaining walls, abutments, check
Used to stabilize steep or highly erosive slopes
Construction plans and drawings should be prepared by
professionals familiar with the use of gabions
Should be securely “keyed” into the foundations and
Structure used to stabilize the grade in natural or artificial channels
Prevent the formation or advancement of gullies and reduce erosion and sediment pollution
Structures – designed in accordance withsound engineering practices – can be constructed of concrete, rock, masonry, steel, aluminum, treated wood
Types - straight drop, drop inlet, box inlet, chute spillway
Capacity – Conditions of adjacent areas is considered when determining the storm frequency
Residences/commercial 100-yr, 24-hr& recreation buildings
Recreation & 25-yr, 24-hrlandscape areas
Agricultural Land 25-yr, 24-hr
A storm flow outlet device constructed at zero grade across the slope whereby concentrated runoff may be discharged onto stabilized ground and converted to sheet flow.
To dissipate storm flow energy at the outlet by converting storm runoff into sheet flow and to discharge it onto areas stabilized by existing vegetation without causing erosion.
A temporary stone filter dam installed across small streams or drainageways
Capture and filter sediment for removal when working in a stream or water body.
Reduce velocity of water.
*The use of a rock filter dam in a stream is considered fill by
the U.S. Army Corps of Engineers and is not allowed in their
There is no formal design. The following standards shall
Drainage area - shall not exceed 50 acres
Height –should not be higher than the channel banks
-center should be at least 6 inches lower than outer edge
Slide slopes – shall be 2:1 or flatter
Location – as close to the source of sediment as possible
Stone size - determined by design criteria for Riprap
A wall constructed of concrete masonry, reinforced concrete cribbing, treated timbers, steel pilings, gabions, stone drywall, rock riprap, etc
Used to stabilize cut or fill slopes where stable slopes are not attainable without the use of wall.
Requires design specific to the site
A device or structure placed in front of a permanent storm water detention pond outlet structure to serve as a temporary sediment filter
Allows permanent storm water detention basins to function as temporary sediment basins for LDAs
Shall not be used in detention basins on live streams or DA >30 acres for Rt-P
headwalls, or concrete weir outlets.
Height should be approx. ½ the height of outlet structure.
Pond must be capable of storing the required volume of storage in addition to required stormwater volume.
Temporary structures typically constructed of silt fence supported by steel or wood posts. Other types may include sandbags, straw bales, brush piles or other filtering material.
Prevent sediment carried away by sheet flow from leaving the site and entering natural drainage way.
Shall not be installed across streams, ditches, waterways or other concentrated flow areas
Structure and all accumulated sediment will be removed as soon as project is permanently stabilized
Type A - 36” wide
Type B - 22” wide
Type C - 36” wide
Wire reinforced, high flows and velocities
Alternatives for Type – B and Type – C are available at www.gaswcc.georgia.gov
For stream buffers and other sensitive areas, two rows of Type C silt fence or one row of Type C Silt Fence backed by hay bales shall be used
6’ Post Spacing
Detail of Type B
Detail of Type C
Temporary protective device formed around a storm drain drop inlet to trap sediment.
To prevent sediment from leaving site or from entering drainage systems prior to permanent stabilization of disturbed area
Should be installed around all storm drain drop inlets that receive runoff from disturbed areas.
The drainage area shall be no greater than
An excavation may be created around the inlet sediment trap to provide additional sediment storage at the rate of 67 cubic yards per acre for the drainage area
For inlets where heavy flows are expected and where an overflow capacity is necessary to prevent excessive ponding
For inlets where heavy concentrated flows are expected
For inlets once pavement has been installed
A basin created by excavation or the construction of a barrier or dam across a concentrated flow area
Consists of a dam, pipe outlet, and an emergency spillway
To detain runoff waters and trap sediment from erodible areas to protect properties and drainage ways
Size according to location, size of drainage area, soil type,
and rainfall pattern
Location – shall never be placed in live streams
Volume – shall be 67 cubic yards per acre drained
Shape – Length to Width Ratio greater than 2:1
Spillways – Principal and Auxiliary. Even if the principal spillway is designed to convey the peak rate of runoff from a 25-yr, 24-hr storm, an emergency spillway shall be present
Conduit through dam (8 inch minimum)
Perforated Riser (1/2 inch holes, 3 inches apart) or Skimmer outlet
St – Outlet Protection
Ch – Channel Stabilization
Temporary Sediment Basin
Temporary Sediment Basin
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 streams, damaging the streambed or channel, or causing flooding.
Not to be used on streams with a drainage area greater than one square mile (640 Acres)
In place for less than one year
Design based on drainage area and slope of watershed
Must convey 2-yr, 24-hr storm
Bridge or culvert crossings may be used
Installed perpendicular to stream
1. Drainage area (ac), average slope of watershed (%), and stream flow rate at bankfull flow (cfs).
2. Detailed dimensions of components for the type of crossing to be used.
Paved and/or riprapped channel sections, placed below storm drain outlets
Reduce the velocity of flow from storm drain outlets
Reduce erosion of receiving channels
Apron Length and Thickness
Providing a rough soil surface on the contour
Aid in the establishment of vegetative cover with seed
Reduce runoff velocity and increase infiltration
Reduce erosion and provide for sediment trapping
Soil surface should not be roughened if slope is to be
stabilized with matting or blankets
Selection of an appropriate method of surface
roughening depends on the type of slope. Slope
steepness, mowing requirements and whether the
slope is formed by cutting or filling should be
considered when choosing one of the three methods
of achieving a roughened slope surface.
recommended unless no alternatives are available.
The soil surface is severely compacted and runoff is
spreading it over the disturbed area after completion of
growth on areas where other measures will not produce
or maintain a desirable stand.
1.The texture of the exposed subsoil or parent
material is not suitable to produce adequate
2. The soil material is so shallow that the rooting
zone is not deep enough to support plants with
continuing supplies of moisture and food.
3. The soil to be vegetated contains material toxic to
A waterway that is shaped or graded to required dimensions and stabilized with vegetation.
Dispose of stormwater runoff
Capacity – At a minimum convey peak runoff expected from a 25-yr, 24hr storm
Velocity –Iswell within the limits of permissible velocity
Drainage - Subsurface drainage measures shall be provided for sites with high water tables or seepage problems. When base flow is present a stone center or lined channel is required.
67 cubic yards per acre drained of sediment
storage is required for each project
Required on LDAs by Erosion and Sedimentation Act of 1975
Proper design, installation, and maintenance
Treat at source
Treat after erosion has begun