1. 1 Best Management Practices -Structural Measures – Level IA: Fundamentals Education and Certification for Persons Involved in Land Disturbing Activities Issued May 2009

2. 2 The Manual for Erosion and Sediment Control In Georgia Referred to as the Manual or Green Book Chapter 6 of the Manual focuses on the standards and specifications for planning, design and installation of erosion and sediment control measures. Updates to the Manual can be found on GSWCC’s website at www.gaswcc.georgia.gov under Programs Urban Lands New Updates to the Manual for Erosion and Sediment Control Page includes newly approved practices, approved products list and other associated documents.

3. 3 Best Management Practices Definition 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

4. 4 Check Dam Definition A small temporary barrier constructed across a swale, drainage ditch, or area of concentrated flow Purpose Reduce velocity Filter sediment Stabilize grade Not to be used in a live stream Cd

5. 5 Check Dam Design Criteria 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. Cd

6. 6 Check Dam Design How to Compute L: L = Height of Cd / Slope as decimal Graded 2”-10”

7. 7 Check Dam Example problem Independence School – School Road Slope From Topo = 5% – 13% Find length between check dams for 1. 5% 2. 10% 3. 13%

8. 8 Check Dam Solution 1.L = Height of Cd / Slope as Decimal L = 2 ft. / 0.05 = 40 ft. 2.L = Height of Cd / Slope as Decimal L = 2 ft. / 0.10 = 20 ft. 3.L = Height of Cd / Slope as Decimal L = 2 ft. / 0.13 = 15 ft.

9. 9 Check Dam Example

10. 10 Channel Stabilization Definition Improving, constructing, or stabilizing an open channel or waterway Purpose Prevent erosion and sediment deposition Provide adequate capacity for flood water, drainage, or other water management practices Ch

11. 11 Channel Stabilization Design Criteria 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 Ch

12. 12 Channel Stabilization Example

13. 13 Construction Exit Definition 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. Purpose To reduce or eliminate the transport of mud from construction area. Co

14. 14 Construction Exit Design Criteria 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 Co

15. 15 Construction Exit Co

16. 16 Construction Road Stabilization Definition Travel way constructed as part of the construction plan including access roads, subdivision roads, parking areas, and other on-site vehicle transportation routes Cr

17. 17 Construction Road Stabilization Design Criteria 6” coarse aggregate applied immediately after grading Geotextile applied for additional stability Grades should be < 10% for slope lengths less than 200 ft Road Widths: 14 ft for one-way traffic 20 ft for two-way traffic 24 ft for trailer traffic Cr

18. 18 Construction Road Stabilization Geotextile underliner

19. 19 Stream Channel Diversion Definition A temporary channel constructed to convey flow around a construction site while a permanent structure is being constructed within a streambed. Purpose To protect the stream channel from erosion and allows work “in the dry”. Dc

20. 20 Stream Channel Diversion Design Criteria 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 Dc

21. 21 Stream Channel Diversion Design Criteria Side slopes shall be no steeper than 2:1 Table 6-12.1 gives channel linings and acceptable velocities. Note differences from channel stabilization. Dc

22. 22 Stream Diversion Channel Stream Diversion Channel Linings Lining MaterialAcceptable Velocity Geotextile/0 - 2.5 fps polyethylene film or sod Geotextile alone2.5 - 9.0 fps Type 1 Riprap &9.0 - 13.0 fps Geotextile Dc

23. 23 Stream Channel Diversion

24. 24 Diversion Definition A ridge of compacted soil, constructed above, across, or below a slope to safely convey runoff to a stable outlet Purpose 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 Di

25. 25 Diversion Design Criteria 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 Di

26. 26 Diversion Selection of design storm based on type of diversion to be used Temporary10-yr, 24-hr storm Permanent25 or 50-yr, 24-hr storm Di

27. 27 Diversion

28. 28 Temporary Downdrain Structure Definition A temporary structure used to convey concentrated storm water down the face of cut or fill slopes. Purpose To safely conduct storm runoff from one elevation to another without causing slope erosion and allowing the establishment of vegetation on the slope. Dn1

29. 29 Temporary Downdrain Structure Design Criteria There is no formal design. The following standards shall be used: 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. Dn1

30. 30 Temporary Downdrain Structure 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 Dn1

31. 31 Dn1

32. 32 Permanent Downdrain Structure Definition A permanent structure used to safely convey surface runoff from the top of the slope to the bottom of the slope Purpose Minimize erosion due to concentrated storm runoff on cut of fill slopes Dn2

33. 33 Permanent Downdrain Structure Design Criteria 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 Dn2

34. 34 Permanent Downdrain Structure

35. 35 Filter Ring Definition A temporary stone barrier constructed at storm drain inlets and pond outlets. Purpose 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. Fr

36. 36 Filter Ring Design Criteria There is no formal design. The following standards shall be used: 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 Fr

37. 37 Filter Ring

38. 38 Filter Ring Example

39. 39 Definition Gabions are large, multi-celled, welded wire or rectangular wire mesh boxes, used in channel revetments, retaining walls, abutments, check dams, etc. Purpose Used to stabilize steep or highly erosive slopes Gabion Ga

40. 40 Design Criteria Construction plans and drawings should be prepared by professionals familiar with the use of gabions Should be securely “keyed” into the foundations and abutment surfaces Gabion Ga

41. 41 Gabion Examples

42. 42 Grade Stabilization Structure Definition Structure used to stabilize the grade in natural or artificial channels Purpose Prevent the formation or advancement of gullies and reduce erosion and sediment pollution Gr

43. 43 Grade Stabilization Structure Design Criteria Structures – designed in accordance with sound 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/commercial100-yr, 24-hr & recreation buildings Recreation & 25-yr, 24-hr landscape areas Agricultural Land 25-yr, 24-hr Gr

44. 44 Level Spreader Definition 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. Purpose 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. Lv

45. 45 Level Spreader Design Criteria Length – Determined by 10-yr, 24-hr storm Width – Minimum 6 feet Lv Peak Q (cfs)Minimum Length (ft) Up to 1010 11 – 2020 21 – 3030 31 – 4040 41 – 5050

46. 46 Rock Filter Dam Design Criteria There is no formal design. The following standards shall be used: 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 Rd

47. 47 Rd Rock Filter Dam

48. 48 Retaining Wall Definition A wall constructed of concrete masonry, reinforced concrete cribbing, treated timbers, steel pilings, gabions, stone drywall, rock riprap, etc Purpose Used to stabilize cut or fill slopes where stable slopes are not attainable without the use of wall Design Criteria Requires design specific to the site Re

49. 49 Retaining Wall Example

50. 50 Retrofitting Definition A device or structure placed in front of a permanent storm water detention pond outlet structure to serve as a temporary sediment filter Purpose 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 Rt

51. 51 Perforated Half-Round Pipe with Stone Filter Should be used only in detention ponds with less than 30 acres total drainage area. Never to be used on exposed pipe end or winged headwall. Diameter of half-round pipe should be 1.5 times the diameter of the principal pipe outlet or wider than the greatest width of the concrete weir. Perforations and stone sizes are shown in Figure 6-19.1. Shall be fixed by specified means (bolts, etc) to concrete outlet structure. Rt-P

52. 52 Slotted Board Dam with Stone Can be used in detention ponds with drainage areas up to 100 acres. Can be used with open end pipe outlets, winged headwalls, or concrete weir outlets. Should be installed with minimum size 4x4 inch posts. Boards should have 0.5-1.0 inch space between them. Rt-B

53. 53 Retrofitting

54. 54 Retrofitting Example

55. 55 Sediment Barrier Definition 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. Purpose Prevent sediment carried away by sheet flow from leaving the site and entering natural drainage way. Sd1

56. 56 Silt Fence Design Criteria 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 Types Type A - 36” wide Type B - 22” wide Type C - 36” wide Wire reinforced, high flows and velocities Sd1 Alternatives for Type – B and Type – C are available at www.gaswcc.georgia.gov

57. 57 Criteria for Silt Fence Placement

58. 58 Silt Fence 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 Sd1-C

59. 59 Silt Fence Example

60. 60 Mulch Berms

61. 61 Straw Bale Detail Sd1-Hb

62. 62 Detail of Type A Silt Fence

63. 63 Silt Fence Detail of Type B

64. 64 Silt Fence Detail of Type C

65. 65 Inlet Sediment Trap Definition Temporary protective device formed around a storm drain drop inlet to trap sediment. Purpose 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. Sd2

66. 66 Excavated Inlet Sediment Trap

67. 67 Inlet Sediment Trap (Sd2-F) For inlets that drains a relatively flat area (slope no greater than 5%) and shall not apply to inlets receiving concentrated flows

68. 68 For inlets receiving runoff with a higher volume or velocity Inlet Sediment Trap (Sd2-B)

69. 69 Inlet Sediment Trap (Sd2-Bg) For inlets where heavy flows are expected and where an overflow capacity is necessary to prevent excessive ponding

70. 70 Inlet Sediment Trap (Sd2-G) For inlets where heavy concentrated flows are expected

71. 71 Inlet Sediment Trap (Sd2-P) For inlets once pavement has been installed

72. 72 Temporary Sediment Basin Definition 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 Purpose To detain runoff waters and trap sediment from erodible areas to protect properties and drainage ways Sd3

73. 73 Temporary Sediment Basin Design Criteria 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 Surface Area 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 Sd3

74. 74 Baffles

75. 75 Baffle Detail

76. 76 Examples Temporary Sediment Basin Sd3 Incorrect filter rock size

77. 77 Temporary Stream Crossing Definition Temporary structure installed across a flowing stream or watercourse for use by construction equipment. Purpose Provides a means for construction vehicles to cross streams or watercourses without moving sediment into streams, damaging the streambed or channel, or causing flooding. Sr

78. 78 TO BE SHOWN ON THE ES&PC PLAN 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.

79. 79

80. 80 Temporary Stream Crossing Example

81. 81 Storm Drain Outlet Protection Design Criteria Capacity Tailwater Depth Apron Length and Thickness Apron Width Bottom Grade Side Slope Alignment Geotextile Materials St

82. 82 Outlet Protection Example

83. 83 Surface Roughening Definition Providing a rough soil surface on the contour Purpose 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 Su

84. 84 Surface Roughening Design Criteria 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. Stair-Step Grading Grooving Tracking Su

85. 85 Surface Roughening

86. 86 Tracking with bulldozer treads on clay soils is not recommended unless no alternatives are available. The soil surface is severely compacted and runoff is increased.

87. 87 Topsoiling DEFINITION Stripping off the more fertile top soil, storing it, then spreading it over the disturbed area after completion of construction activities. PURPOSE To provide a suitable soil medium for vegetative growth on areas where other measures will not produce or maintain a desirable stand. Tp

88. 88 Conditions This practice is recommended for sites of 2:1 or flatter slopes where: 1.The texture of the exposed subsoil or parent material is not suitable to produce adequate vegetative growth. 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 plant growth. Topsoiling Tp

89. 89 Vegetated Waterway Definition A waterway that is shaped or graded to required dimensions and stabilized with vegetation. Purpose Dispose of stormwater runoff Prevent erosion Reduce Sedimentation Wt

90. 90 Vegetative Waterway

91. 91 Clean-out Elevations  One-Half (1/2) Full Silt fence Check dams Rock filter dams Inlet sediment traps  One-Third (1/3) Full Temporary sediment basins Retrofitted detention ponds

92. 92 Review BMPs Required on LDAs by Erosion and Sedimentation Act of 1975 Proper design, installation, and maintenance Vegetative Measures Control erosion Treat at source Structural Measures Control sedimentation Treat after erosion has begun