E&S BMP DESIGN. Working Toward a Better Conclusion

Transcription

1 E&S BMP DESIGN Working Toward a Better Conclusion

2 Are Compost Socks Enough? Compost socks are excellent BMPs when properly used and maintained However, they do have limitations

3 Compost Socks The right sized mesh must be used The flat dimension must be at least 1.5 times the specified diameter of the sock

4 Compost Socks Care should be taken to avoid twisting

5 Compost Socks Must be installed on existing level grade

6 Compost Socks Have definite slope length limitations

7 Compost Socks Cannot be used in areas of concentrated flow Best case: Undercut or overtopped Worst case: Failure

8 Compost Socks Must have good contact with underlying soil

9 Must be properly staked Compost Socks

10 Compost Socks Joints must be properly staked

11 Have a definite shelf life Compost Socks

12 Compost Socks Are easily damage by equipment

13 Compost Socks Damaged socks must be properly repaired or replaced This is not how to do it!

14 Haul Roads Haul roads can become major sources of sediment pollution if not properly designed, constructed, and maintained

15 Haul Roads Runoff should be directed off the roadway as efficiently as possible One method: crowning

16 Haul Roads In steep terrain, insloping works best

17 Haul Roads A suitable top dressing not only reduces sediment discharge but reduced wear & tear on equipment

18 Haul Roads Where insloping is used, a roadside ditch is needed Protective liners are required for roadside ditches discharging to special protection waters (HQ or EV), where discharging directly to surface waters, or where necessary to prevent the erosion of ditch itself

19 Haul Roads Typical liners used in roadside ditches include: Riprap Curled Wood TRM

20 Haul Roads Straw Bales in the ditch are not the answer Neither are rock checks

21 Haul Roads Properly spaced cross drains can help by keeping flow in the ditch to a minimum Make use of existing flow paths Provide suitable outlet protection

22 Haul Roads Outlet protection typically takes the form of riprap aprons Can also include transition mats, stilling basins, and drop structures

23 Haul Roads Waterbars are not recommended for active haul roads

24 Haul Roads Broad-based dips are recommended for active haul roads Broad-based Dip Low Gradient (<5%) Roadways

25 Haul Roads Broad-based dips for steeper gradients Broad-based Dip High Gradient (5% - 10%) Roadways

26 Haul Roads Stream Crossings Permits!!! It is not true that one crossing is allowed without a stabilized crossing!

27 Haul Roads Ford crossings are not appropriate during active construction

28 Haul Roads Temporary bridge is the preferred method of stream crossing

29 Haul Roads Culverted Crossing should have clean rock fill

30 Haul Roads Wetland Crossings Permits!!! Stable crossing must be provided

31 . Calibri Stabilized wetland Crossings Wood Mat HDPE Composite Mat Terramat Expanded Metal Grating

32 Haul Roads Runoff should be directed into a compost trap at stream and wetland crossings

33 Residential Lot BMPs Residential lot construction is often a major source of sediment pollution

34 Residential Lot BMPs Chapter 10 in the E & S Manual addresses typical BMPs used during construction on residential lots Three basic scenarios shown in the standard details: Lot Above Roadway Lot Below Roadway Lot Along Ascending or Descending Roadway

35 Residential Lot BMPs BMPs for residential lots are very simple: Upslope diversion Channel Compost sock with modified filler

36 Residential Lot BMPs BMPs for residential lots are very simple: Upslope diversion Downslope sediment barrier Silt fence

37 Residential Lot BMPs BMPs for residential lots are very simple: Upslope diversion Downslope sediment barrier Silt fence Fiber log

38 Residential Lot BMPs BMPs for residential lots are very simple: Upslope diversion Downslope sediment barrier Silt fence Fiber log Compost Sock

39 Residential Lot BMPs BMPs for residential lots are very simple: Upslope diversion Downslope sediment barrier Stabilized Entrance

40 Residential Lot BMPs BMPs for residential lots are very simple: Upslope diversion Downslope sediment barrier Stabilized Entrance Downspouts attached to roof leaders extended to curb

41 Residential Lot BMPs Maintenance of On-lot BMPs not provided

42 Commercial Lot BMPs Commercial lots often need more than sediment barriers

43 Commercial Lot BMPs Stormwater facilities can often be used as temporary E&S BMPs Perforated Metal box attached to concrete riser

44 Commercial Lot BMPs Stormwater facilities can often be used as temporary E&S BMPs Embankment sediment trap with slope pipes & plywood baffles

45 Commercial Lot BMPs Embankment sediment trap with compost socks & super silt fence baffles (ABACT)

46 Design of Compost Sock Traps Same maximum drainage area, required storage capacity, and freeboard as for other traps Sump area above socks often helpful No spillway required Minimum trap height = one 12 dia. Sock Socks may be stacked

47 Construction Sequencing Keep it simple! Must be site specific Must be complete from initial disturbance to final stabilization Address all proposed E&S BMPs Do not include maintenance Stabilize as you go Remove temporary BMPs when no longer needed Conditions of stabilization

48 Utilities Avoid conflicts with E&S BMPs show them on the E&S plan maps Installing a stormwater manhole in a sediment trap

49 Utilities Avoid conflicts with E&S BMPs show them on the E&S plan maps Avoid crossing surface waters wherever possible otherwise bypass normal flows Flumed Stream Crossing Pump Bypass Cofferdam

50 Utilities Avoid conflicts with E&S BMPs show them on the E&S plan maps Avoid crossing surface waters wherever possible bypass normal flows Use stabilized crossings Culverted Crossing Temporary Bridge

51 Utilities Avoid conflicts with E&S BMPs show them on the E&S plan maps Avoid crossing surface waters wherever possible bypass normal flows Use stabilized crossings Get 105 permits where needed Minimize open trenches (50 max at end of day) Follow OSHA requirements Keep current with backfilling & stabilization Blanket within 50 of surface water (100 of HQ or EV water)

52 Transmission Lines Time period for open trench operations at any station should be minimized 30 days for most locations Longer periods can be approved on case-by-case basis if sufficient justification provided

53 Transmission Lines Time period for open trench operations at any station should be minimized 30 days for most locations Longer periods can be approved on case-by-case basis if sufficient justification provided Trench plugs used at all stream & wetland crossings as well as on steep slopes

54 Transmission Lines Time period for open trench operations at any station should be minimized 30 days for most locations Longer periods can be approved on case-by-case basis if sufficient justification provided Trench plugs used at all stream & wetland crossings as well as on steep slopes Open cut stream crossings Bypass flows for minor streams (10 wide or less at normal flow depth) Completed within 24 (minor stream) to 48 hours (major stream up to 100 wide)

55 Transmission Lines Facilities for removing sediment from pumped water should be provided at all crossings Pumped water filter bag Portable Sediment Tank w/inclined Planes

56 Transmission Lines Facilities for removing sediment from pumped water provided at all crossings Pipe should be ready for placement before trenching begins

57 Transmission Lines Horizontal Directional Drilling (HDD) installation Suitable BMPs in place (sediment barriers) & operating properly Readiness for any inadvertent return Suitable method for collecting & treating drilling fluid

58 Conclusion It is always cheaper, and much more satisfying, to do things right the first time.

59 Darl Rosenquest P.E., P.G. Senior Civil Engineer DEP California Mining Office 25 Technology Drive Coal Center, PA