Stormwater Management

1. Stormwater Management Regulations relating to Stormwater Management Dennis A. Shannon Department of Agronomy & Soils Auburn University Stormwater Management

2. State Regulations • National Pollution Discharge Elimination System (NPDES) Permit • Section 402 of Clean Water Act implemented in Alabama by the Alabama Department of Environmental Management (ADEM) Stormwater Management

3. State Regulations relating to Stormwater Management • National Pollution Discharge Elimination System (NPDES) Permit • Responds to EPA’s 1990 Stormwater Program under CWA • Uses NPDES permits to reduce pollution associated with stormwater • Two Phases Stormwater Management

4. State Regulations relating to Stormwater Management • National Pollution Discharge Elimination System (NPDES) Permit • Phase I (1990) regulates • Medium & large municipal separate storm systems • Population 100,000 or greater • Construction activity disturbing ≥ 5 acres • 10 categories industry • Phase II Final Rule (2003) also regulates: • Small municipal separate storm systems (MS4) • Population ≥ 50,000 must have ordinances • Small construction activity disturbing ≥ 1 acre • City of Auburn has permit by rule status for smaller sites Stormwater Management

5. State Regulations • National Pollution Discharge Elimination System (NPDES) Permit • Construction, including: • Excavation • land clearing • other land disturbance activities and associated areas • generally relates to 1 acre or more • Builder must have plan • Must do minimum damage Stormwater Management

6. State Regulations • National Pollution Discharge Elimination System (NPDES) Permit • Construction: • Owner or Builder must: • Develop a stormwater pollution prevention plan (SWPPP) • Complete an endangered species determination for project site • file a Notice of Intent (NOI) • Obtain a NPDES permit • Implement all BMP’s outlined in SWPPP • File a notice of termination upon completion of project Stormwater Management

7. State Regulations • National Pollution Discharge Elimination System (NPDES) Permit • Surface coal mining • Non-metallic, non-coal mining, including • Quarrying • Excavation • Processing • Transloading • Storing • Recovery and associated areas • General permits for less than 5 acres • Specific permits for greater than 5 acres Stormwater Management

8. State Regulations • National Pollution Discharge Elimination System (NPDES) Permit • inactive or abandoned mining • surface or underground • mineral, ore or other material Stormwater Management

9. State Regulations • ADEM requires implementation and maintenance of appropriate, effective best management practices (BMPs) to prevent/minimize discharges of sediment and other pollutants into waters of the State of Alabama • (Alabama Handbook (1993) pp. VI-14, VI-15; (2003) Vol. 1, Chapter 3) • BMP • a practice/measure used for NPS pollution abatement Stormwater Management

10. State Regulations • Water of State of Alabama • any water not wholly contained on one individuals property or that crosses a property line • Violators must file report with ADEM showing that steps have been taken to correct deficiencies or violations • Certified by registered professional engineer • Report must address removal or stabilization of sediment deposited off-site. Stormwater Management

11. State Regulations • National Pollution Discharge Elimination System (NPDES) Permit • Normal farming activities exempt, except large animal feeding operations (“CAFOs”) • includes construction of waterways, terraces, water and sediment control basins, etc. • impoundments for recreation are not exempt if disturbance involves more than 5 acres • cannot discharge animal waste into a stream • large animal operations not exempt • i.e. 1,000 head beef feedlot • Confinement makes difference. • Pasture exempt • Most complaints in Alabama around Sand Mountain, relating to poultry, including dead birds in creeks. Stormwater Management

12. State Regulations • National Pollution Discharge Elimination System (NPDES) Permit • Normal silviculture exempt • construction of roads and landings of over 5 acres not exempt • ADEM gets involved mainly on a complaint basis • respond to report of apparent violation Stormwater Management

13. The Surface Mining Control and Reclamation Act of 1977 (PL 95-87) Stormwater Management

14. The Surface Mining Control and Reclamation Act • Public Law 95-87 passed because of the vast acreage being mined in the Western states and the unreclaimed mined land in the Eastern U. S. • drastically disturbed land is unsuited for most uses in the future • source of much water pollution and a safety hazard Stormwater Management

15. The Surface Mining Control and Reclamation Act • applies only to mining for coal • addresses adverse onsite and offsite impacts to the related natural resources Stormwater Management

16. The Surface Mining Control and Reclamation Act • potential pollutants include: • acid drainage with toxic quantities of • Copper • Iron • aluminum • manganese • mine spoils with toxic quantities of copper, iron, aluminum and manganese that will not support plants Stormwater Management Maryland Department of Natural Resources

17. The Surface Mining Control and Reclamation Act • potential pollutants include: • sediment • pyrite (FeS2) commonly exists in coal deposits and produces “yellow-boy” • acid water and poor plant growth medium Stormwater Management National Oceanic and Atmospheric Administration National Oceanic and Atmospheric Administration

18. The Surface Mining Control and Reclamation Act • Requirements • stormwater management • water quality parameters are well defined and may include treating the water that is in basins • prime farmland be restored to original productivity Stormwater Management

19. The Surface Mining Control and Reclamation Act • all other landscapes be reclaimed according to an approved plan that addresses: • erosion and sediment control • plant diversity • landscape attributes • i.e. “original contour” • water quality parameters well defined • wetlands protected Stormwater Management

20. The Surface Mining Control and Reclamation Act • Administered By State Agencies • Alabama Surface Mining Reclamation Commission • NPDES oversight by ADEM • Estimates of Area Needing Reclamation • Abandoned • Alabama • 1977 - 72,000 acres • much smaller in 2008 • probably less than 20,000 • Required by law • Alabama • 35,000 acres Stormwater Management

21. Determining Runoff Exercise Dennis A. Shannon Department of Agronomy & Soils Auburn University Determining Runoff

22. Watershed Hydrology • A watershed is a natural drainage area, where all the water drains to a common point. Determining Runoff Gary Wilson, USDA Natural Resources Conservation Service

23. Watershed Hydrology • The amount of runoff flowing through the outlet point is a function of • total rainfall • watershed area draining towards the outlet • the rates of infiltration and evapotranspiration. Determining Runoff

24. Watershed Hydrology • Changes in the hydrology of the watershed that increase the percentage of rainfall that runs off the landscape increase the risk of scouring erosion and flooding lower in the watershed. • Changes in runoff need to be estimated prior to development Determining Runoff

25. Watershed Hydrology • Important factors affecting volume of runoff are: • Watershed area • Watershed slope • Soil characteristics • Vegetative cover characteristics Stormwater Management

26. Watershed Hydrology • Runoff Estimation Formulas • Mannings Formula • uses slope, cross-sectional area and an estimate of surface roughness to estimate flow velocity in open channels • not covered • p. 88 in Troeh et al. Stormwater Management

27. Watershed Hydrology • Runoff Estimation Formulas • NRCS Curve Number Method • (better known as SCS Curve Number Method) • an empirical model that uses information about: • the watershed size • average slope • Cover • hydrologic soil group • hydrologic condition • Estimates: • runoff volume • peak flow Stormwater Management

28. Watershed Hydrology • Runoff Estimation Formulas • NRCS Curve Number Method • These estimates are used to design outlets and stormwater management structures that are safe to handle peak flows from runoff from storms of designated storm size. • These structures should be constructed before making changes to the hydrology within the watershed. Stormwater Management

29. Purpose • Become familiar with one method used in evaluating the features of a landscape to determine the runoff from rainfall events. • Learn the effects of soil properties, cover and other site characteristics on amount of runoff in a watershed Determining Runoff

30. References • Alabama Engineering Field Design Manual • Appendix A6 in 1993 edition of Alabama Handbook for Erosion Control, Sediment Control and Stormwater Management on Construction Sites and Urban Areas. • (Not found in 2003 edition, but version available on the web at • http://efotg.nrcs.usda.gov/treemenuFS.aspx?Fips=01081&MenuName=menuAL.zip • and http://directives.sc.egov.usda.gov/17541.wba Determining Runoff

31. Watershed Hydrology • Why estimate runoff? • Estimates of runoff (acre-inches) and peak flow (cubic feet per second) are necessary to design conservation practices that convey, detain or store runoff and stormwater. • These practices include: • shaping natural depressions into grassed waterways • numerous construction practices frequently referred to as “structures.” Stormwater Management

32. Watershed Hydrology • The practices must provide a shape and capacity for concentrated runoff to reach a safe outlet without creating erosion and without failing because of stormwater overtopping the structure. Stormwater Management

33. Estimating Runoff • Important factors affecting volume of runoff are: • Watershed area • Watershed slope • Soil characteristics • Vegetative cover characteristics Determining Runoff

34. Watershed Hydrology • Frequency and Duration Concepts • frequency explains how often a storm of given size is expected to reoccur • e.g. every 5 years, 10 years, 25 years, 50 years, 100 years • durationexplains how long of a period to consider when evaluating the storm • e.g. 1/2 hour, 1-hour, 6-hour, 12-hour, 24-hour • example of describing a storm or design: “10-year, 24-hour storm” Stormwater Management

35. Watershed Hydrology • NRCS Curve Number Method • (SCS Curve Number Method) • Inputs: • watershed size • average slope • cover • hydrologic soil group • hydrologic condition • Estimates: • runoff volume • peak flow Stormwater Management

36. Watershed Hydrology • NRCS Curve Number Method • These estimates are used to design outlets and stormwater management structures that are safe to handle peak flows from runoff from storms of designated storm size. • These structures should be constructed before making changes to the hydrology within the watershed. Stormwater Management

37. Determining Runoff Steps in Estimating Runoff by NRCS Curve Number Method Determining Runoff

38. Step 1 • Estimate drainage area (watershed area) acres • 45 acres Determining Runoff

39. Step 2 • Determine watershed slope factor • Average watershed slope in direction of overland flow • Flat • 0 – 3 % • Moderate • 3 – 8 % • Steep • > 8 % • Slope = 6 % • = Moderate Determining Runoff

40. Step 3 • Determine curve number (CN) • Determine soils and hydrologic soil groups • TABLE 2-2 (pages 2-5 through 2-7) • Soil survey Determining Runoff

41. Determining Runoff

42. Step 3 • Determine curve number (CN) • Determine • land use/cover • hydrologic condition • (related to soil quality) • treatment or practice • TABLE 2-3 (page 2-8) • 25 acres pasture – contour & terrace • 20 acres wood Determining Runoff

43. Determining Runoff

44. Step 3 • Determine curve number (CN) • develop weighted curve number if two or more heterogeneous areas exist • weight to reflect acres and CN for each area • 20 acres X CN 60 = 1200 • 25 acres X CN 59 = 1475 • 1200 + 1475 = 2675 • 2675/45 acres = 59.4 CN ~ CN 60 Determining Runoff

45. Step 4 • Select rainfall criteria • Frequency • Duration • example: • Grassed waterway or outlet – 10 year, 24 hour storm • Fish Pond • Principal spillway - 5-year, 24 hour storm • Emergency spillway – 25-year, 24 hour storm Determining Runoff

46. Step 5 • Determine runoff (inches) • use CN and rainfall • TABLE 2-4 • (pages 2-11, 2-12, 2-14) Determining Runoff

47. Determining Runoff

48. Step 5 • Determine runoff (inches) • use CN and rainfall • from TABLE 2-4 • Lee County 5 yr 24 hour storm = 5.4 inches • Lee County 25-yr 24 hour storm = 7.3 inches Determining Runoff

49. Step 5 • Determine runoff (inches) • Use Figure 2-2 (page 2-9) to read off direct runoff or Table 2-5 Determining Runoff

50. Determining Runoff