1. Sediment and Erosion Control: Field Performance of Construction Site BMPs and Optimized Designs for Enhanced Stormwater Control Stuart Jennings Reclamation Research Group, LLC

2. Format of Presentation Review of BMPs and resources Estimating erosion severity BMP strategies Observations from construction sites

3. Erosion Accelerated erosion occurs at construction sites when stabilizing vegetation is removed

4. On-site Stormwater Control Which BMPs are appropriate to my site? –What are the unique soil and vegetation characteristics of my site? –What can I expect for precipitation? –How long will it take for stabilization by vegetation?

5. Families of BMPs Surface Stabilization BMPs—hydromulch, straw mulch, erosion control blankets, temporary seeding, slope roughening, others Sediment Control BMPs—silt fence, check dams, sediment basins, lined channels, straw bales, others Non-storm water BMPs—Equipment decon areas, stockpile management, tracking control, stabilized site entrances, others

6. A Generic BMP Gameplan

7. Examples of BMPs—straw mulch

8. Examples of BMPs—rock check dams

9. Examples of BMPs—erosion control fabric

10. Revisiting the Construction BMP Palette Using EPA and Montana Department of Transportation Guidance http://cfpub.epa.gov/npdes/stormwater/ menuofbmps/ http://www.mdt.mt.gov/research/projects /env/erosion.shtmlhttp://www.mdt.mt.gov/research/projects /env/erosion.shtml

17. MDT Menu of BMPs –Section 3 - Best Management PracticesSection 3 - Best Management Practices –Section 3a - Soil Stabilization BMPsSection 3a - Soil Stabilization BMPs –Section 3b - Sediment Control BMPsSection 3b - Sediment Control BMPs –Section 3c - Wind Erosion ControlSection 3c - Wind Erosion Control –Section 3d - Snow ManagementSection 3d - Snow Management –Section 3e - Stabilized Construction Entrance/ExitSection 3e - Stabilized Construction Entrance/Exit –Section 3f - Water Conservation PracticesSection 3f - Water Conservation Practices –Section 3g - Material Delivery and StorageSection 3g - Material Delivery and Storag 50 page.pdf, 15 BMPs 41 page.pdf, 11 BMPs 3 page.pdf, 1 BMP 7 page.pdf, 3 BMPs

20. Developing a site specific strategy Soil type Slope steepness Potential rainfall Adjacent water resources Seasonality of work Construction sequencing BMP selection, installation, monitoring, maintenance Emphasis on surface stabilization or sediment control BMPs, or both

21. Erosion Prediction using the Universal Soil Loss Equation A=RKLSCP A = Average Annual Soil Loss (tons) R = Rainfall Amount K = Soil Erodibility L = Slope Length S = Slope steepness C = Cover Factor P = Conservation Practices RUSLE Computer Program: http://www.techtransfer.osmre.gov/NTTMainSite/Library/hbmanual/rusle.htm

22. Rainfall Factor (R) Rainfall intensity and duration Built in database for rainfall intensity As rainfall intensity increases, erosion increases As rainfall duration increases, erosion increases A=RKLSCP

23. NRCS TR-55 Storm Types

28. Soil Erodibility Factor (K) Relates to soil texture and rock content Silty soils are typically most erodible Sandy soils have better infiltration, larger particles Clay soils have better cohesion A=RKLSCP

29. Slope Factors L = Length of Flow Path Longer flow paths have more erosive power S = Slope steepness Steep slopes have higher runoff velocities A=RKLSCP

30. Cover Management Factor (C) Erosion rate directly proportional to the amount of vegetation cover protecting the soil surface Vegetation reduces rainfall impact energy Vegetation promotes infiltration Vegetation reduces runoff velocity Vegetation traps sediment Have control over this factor A=RKLSCP

31. Conservation Practices Factor (P) Manipulation of the soil surface to discourage erosion Provides slope storage Surface roughening Pitting Implemented on the contour A=RKLSCP

32. Example 1, Consider a 1 acre area In an area that receives 12 in of annual precipitation, 1 acre-ft of water is applied to the soil surface annually as rain and snow 1 acre-ft = 325,000 gallons per acre per year Therefore a 1 inch rainstorm = 27,000 gal water 27,000 gal water or 112 tons of water Question: How much erosion will occur? Answer: It all depends

33. Example 2, consider 1 acre of bare soil Apply 1 in of rain over a 1-hour period Sandy loam texture  90% infiltration, 3,000 gal runoff Silt loam texture  40% infiltration, 16,000 gal runoff Clay loam texture  20% infiltration, 22,000 gal runoff

35. Model example Sub- Watershed Watershed Area (acres) Horizontal Slope Length (feet) Slope Steepness (%) A4.830010 B950020 C4.420050 This example uses an 18.2 acre watershed and the Colstrip 16-18 climate record

36. Sub- Watershed Watershed Area (acres) Horizontal Slope Length (feet) Slope Steepness (%) A4.830010 B950020 C4.420050 Bare soil, no BMPs

37. Sub- Watershed Watershed Area (acres) Horizontal Slope Length (feet) Slope Steepness (%) A4.830010 B950020 C4.420050 Bare soil, no BMPs

38. Sub- Watershed Watershed Area (acres) Horizontal Slope Length (feet) Slope Steepness (%) A4.830010 B950020 C4.420050 Bare soil, no BMPs

39. Sub- Watershed Watershed Area (acres) Horizontal Slope Length (feet) Slope Steepness (%) A4.830010 B950020 C4.420050 BMP= soil rough, broadcast seeded, woodfiber mulch

40. Sub- Watershed Watershed Area (acres) Horizontal Slope Length (feet) Slope Steepness (%) A4.830010 B950020 C4.420050 BMP= soil rough, broadcast seeded, woodfiber mulch

41. Erosion Control by Dense Grass Subwatershed Area (acres) SoilManagement Sediment Yield (tons per acre) Total Sediment Yield (tons) A4.8Loamy SandDense Grass0.0030.0 B9Loamy SandDense Grass00.0 C4.4Loamy SandDense Grass0.010.0 A4.8SiltDense Grass0.0080.0 B9SiltDense Grass0.0190.2 C4.4SiltDense Grass0.040.2 A4.8Silty ClayDense Grass0.0050.0 B9Silty ClayDense Grass0.010.1 C4.4Silty ClayDense Grass0.020.1

42. Sediment Yield Example SiteSubwatershedAreaSoilManagement Sediment Yield, tons per acre Total Sediment Yield (tons) ColstripA4.8Loamy SandRough, Bare8.541 ColstripA4.8Silty ClayRough, Bare9.244 ColstripA4.8SiltRough, Bare47226 ColstripA4.8Loamy Sand Rough, Bare, broadcast seeded, woodfiber mulch 2.913.9 ColstripA4.8Silty Clay Rough, Bare, broadcast seeded, woodfiber mulch 3.114.9 ColstripA4.8Silt Rough, Bare, broadcast seeded, woodfiber mulch 1781.6 ColstripA4.8Loamy SandDense Grass0.0030.0 ColstripA4.8Silty ClayDense Grass0.0050.0 ColstripA4.8SiltDense Grass0.0080.0 ColstripB9Loamy SandRough, Bare31279 ColstripB9Silty ClayRough, Bare33297 ColstripB9SiltRough, Bare1801620 ColstripB9Loamy Sand Rough, Bare, broadcast seeded, woodfiber mulch 9.989 ColstripB9Silty Clay Rough, Bare, broadcast seeded, woodfiber mulch 1090 ColstripB9Silt Rough, Bare, broadcast seeded, woodfiber mulch 61549

43. Runoff Curve Numbers NRCS National Engineering Handbook Runoff Curve Number –Dependent on soil characteristics and cover Simpler planning tool for runoff outcome expressing the percentage of rainfall that is likely to runoff Four soil types with increasing runoff potential compared to typical land uses

45. Runoff Coefficients Cover Type Soil Type A (sand) Soil Type B Soil Type C Soil Type D (clay) Open space—good grass39617480 Paved parking lot98 Gravel road76858991 Fallow agricultural land—bare soil 77869194 Good rangeland/pasture39618689 Hay meadow, no grazing30587178 Sagebrush with good grass understory -354755 Newly graded areas77869194

46. Example How much runoff would result from a 0.4 inch rainstorm falling on a 2.5 acre construction site with the following characteristics: –Type B soil –25% undisturbed pasture –17% paved parking –10% gravel roads –48% newly graded areas

47. Calculation 0.41 inch rainstorm across 2.5 acres= –0.41”/12 x 2.5 acres x 43,560 ft 2 x 7.48 gal/ft 3 = 27,831 gallons of rainfall on site –22, 734 gallons runoff –5,096 gallons infiltration Cover Type%CNRunoff (gallons) Undisturbed pasture25614244 Paved parking17984636 Gravel roads10852366 Newly graded areas—bare soil 488611,489

48. Review Erosion is a naturally occurring process that is greatly accelerated on construction sites when bare soil is exposed There are many types of BMPs that may be used to control erosion (Internet guides) Erosion can be predicted by computer models and vast amounts of sediment can be eroded from small areas

49. How do we control erosion? Limit the extent of disturbance Rapidly reestablish stabilizing plant cover Promote infiltration and prevent runoff Provide for capture of sediment if runoff occurs

50. Mass Balance Bozeman receives ~19 inches of annual precipitation, or 516,000 gallons of water per acre per year What happens to all that water? Mass balance is required: P-ET+D±RO=∆S P=Precipitation ET=Evapotranspiration D=Drainage RO=Run-off/Run-on ∆S=Change is soil storage

51. BMP Strategy We can’t change precipitation We want to maximize evapotranspiration (plants) We want to maximize infiltration (drainage) We want to minimize runoff P-ET+D±RO=∆S

52. Soil Physics

53. Infiltration and Evapotranspiration Infiltration of precipitation is greatly increased by soil structure and presence of plants. In Montana most all precipitation can infiltrate if the precipitation intensity is modest and the ground isn’t frozen. ET>>R Plants can evapotranspire hundreds of thousands of gallons per acre per year

54. Facilitating Rapid Vegetation Establishment Avoid compaction Maximize surface roughening Beware of fine textured soils Consider temporary seeding

55. Rapid & Robust Sparse Slow & Stunted

56. The Revegetation Dilemma Vegetation is the glue that holds the soil in place Most construction sites use seeded vegetation and not sod Most construction sites are not irrigated Vegetation grows slowly Stabilization commonly takes 2 years in Montana

57. Rapid Revegetation (cont.) What we want for stormwater control is rapid vegetation growth to reduce stormwater discharge What we commonly get is slow vegetation growth and accentuated erosion from typical time of seeding in late fall until mid summer when a small plant may grow from the seed planted

58. Rapid Revegetation (cont.) We typically seed perennial native grasses The seeding window for perennial native grasses occurs twice a year—early spring and late fall. An opportunity exists to use a temporary seeding with an annual grass Annual plants grow quickly, can be planted anytime the soil is warm and damp. Annual plants are a good soil stabilizer and the seed is inexpensive

59. Wheat versus Western wheatgrass

60. Western Wheatgrass (perennial plant) Wheat (annual plant)

61. Progressive Sizing of Sediment Control BMPs

62. Progressive Sizing—Sediment Control BMPs Discharge Watershed Boundary Ditch/Drainage Bottom 7 6 5 4 3 2 1 In this 1 acre hypothetical watershed 100% of the area has been disturbed. A 1 inch rainfall occurs and 50% of the rainfall infiltrates into the soil. How much stormwater runs through each BMP? Assume that the spacing between BMPs is constant.

63. Progressive Sizing—sediment control BMPs Discharge Watershed Boundary Ditch/Drainage Bottom BMP NumberSubwatershed Size (acres) Volume of Water Generated (Gallons) 10.05 (pink line)679 20.1 (maroon line)1358 30.2 (olive line)2716 40.34073 50.56789 60.810862 71.013578 7 6 5 4 3 2 1

64. Why is erosion control important? Sediments are a leading cause of water pollution in Montana and in the U.S. –3723 miles of Montana streams impaired by sediments ( MDEQ TMDL program 2002 ) Sediments in streams are a leading cause of fishery degradation Significant fines are possible –$436,000 in MT Water Quality Act fines since 2002 –40 active enforcement cases in FY 08

65. Single family residence homesite $34,800 fine

66. Observations from construction sites in MT, WY, ID http://stormwater.montana.edu/ CD (Stormwater Control: Implementing Construction Site BMPs in the Northern Rocky Mountains)

76. Compost Application using Blower Truck Several hundred feet of hose can be attached to the blower truck to allow for distant installation of compost blankets on steep slopes Compost Blanket

78. Revegetation Results using Compost on steep highway cut slopes Glacial silt parent material Alluvial rock parent material

85. Monitoring in response to precipitation or snow melt

86. Changing Site Hydrology/ Seasonal Changes in Climate

87. Some BMPs Require Removal

88. Importance of Soil Quality

89. Importance of Surface Roughening and Seedbed Preparation Contour Tillage

90. Surface Protection

91. Streambank Stabilization

92. Note sediment in culvert Nick Point without appropriate anchoring

97. 2002 2003 2006

100. BMP Strategy Summary Understand unique site attributes: soil, slope steepness, climate, soil quality Promote infiltration of precipitation into soil Need to achieve rapid and robust vegetation establishment Need Sediment Control BMPs until vegetation established Need maintenance and monitoring