NRCS Overview. National Dam Safety Program Technical Workshop #19 February 22-23, 2012

Transcription

1 NRCS Overview National Dam Safety Program Technical Workshop #19 February 22-23, 2012 Thomas Brown National Design, Construction, and Soil Mechanics Center (NDCSMC) Fort Worth, Texas

2 NRCS Dam Inventory Significant Hazard: 2,200 High Hazard: 2,050 Total: 4,250 May 2011

3 Filter/Drain Configuration Filter/Drain objectives Intercept, filter and safely discharge seepage Implementation of TR60 minimum requirements varies Between regions and states Dam size Function Site Conditions Historically have often constructed individual filter/drain elements Foundation Drain Filter Diaphragm around outlet conduit

4 Typical Filter Diaphragm Configuration NRC S NEH Part 628 Chapter 45 Filter Diaphragms FEMA

5 Filter/Drain Trends Same overall filter/drain objectives Continuous filter/drain system including chimney Comprehensive protection against expected and unexpected Seepage More unique rehabilitation filter/drain configurations to address individual circumstances of existing structures

6 Typical Chimney Drain Sloping chimney filter/drain Conduit FEMA

7 More accessible design Pipe Components Larger diameter pipe Gradual bends Manhole access points Pipes placed near toe to allow excavation if required FEMA P-675, FEMA 484 Solid wall HDPE or PVC Reclamation DSO-09-01, September 2009 Flow measurement/sediment capture features

8 Lost River 16 West Virginia Water Supply- Flood Control Completed? Height 90 feet Gannett Fleming Inc.

9 Typical Embankment Section

10 Drainage System Perspective Gannett Fleming Inc.

11 Blanket Drain Typical Section Fine Drainfill ASTM C33 Fine Aggregate Medium Drainfill ASTM #8 Coarse Drainfill ASTM # 57

12 Drain System Plan

13 Manhole Section Pipe bend detail

14 New Creek 14 West Virginia Water Supply- Flood Control Completed 1963 Height 110 feet

15 Excavation Plan Gannett Fleming Inc.

16 Typical Section

17 Fine Drainfill ASTM C33 Fine Aggregate Coarse Drainfill ASTM # 8 Blanket Drain Detail

18 Coarse Drainfill Placement in Blanket Drain

19 Welding HDPE Toe Drain

20 Placing Fill on Top of Blanket

21 Completion of Blanket Drain At Outlet

22 Construction of Chimney Drain and Berm

23 Toe Drain Access Manhole

24 Renwick Dam North Dakota Flood Control Recreation Completed 1962 Height 50 Feet

25 Approximate Foundation Drain Location

26 12 inch diameter asphalt coated CMP

27 Excavation for Foundation Drain Inspection

28 Excavation for Foundation Drain Inspection

29 Exposed Foundation Drain Pipe

30 Cleaning Pipe

31 Second Drain Investigation Excavation

32 Open Joint in Pipe

33 Pipe Repair

34 Modified Drain Outlet

35 Millsite Dam Utah Water supply Completed 1972 Height 115 ft.

36 Typical Section Zone I = -5 w/30-48% minus No. 200 Zone II = -5 w/19-43% minus No. 200 Zone III = +5 material Foundation: Silty/Clayey Sand&Gravel

37 Placing Zone III

38 Chimney Drain

39 Surface of Chimney Drain During Fill Construction

40 Conceptual Modified Section

41 Used extensively Geosynthetics Primarily used in rehabilitation Limitations Use as a filter When located within the dam embankment In applications where both filtration and flow are required

42 Embankment Rehabilitation in Arid Regions Dry Dams Short duration loading Extensive Cracking Primary failure concern is erosion verses piping Choke filters rather than filter/drains Intercept and reduce erosive flow and particle movement through embankment cracks Drainage is not a primary consideration

43 Transverse Crack in Embankment

44 Upstream Approach 16-OZ Geotextile URS

45 HDR Engineering Inc. Filter Placement

46 Centerline Approach 16-OZ Geotextile Ninyo & Moore

47 Trench Excavation

48 Filter Placement

49 Filter Placement

50 Spillway Drains A preponderance of NRCS dams have unlined spillways Increasingly, hardened spillways are being used Majority are over the dam embankment Drainage system is important aspect of design

51 Salado 15R TX Flood Detention Completed 2005

52 RCC Plan

53 Section Through RCC Steps Geotextile Coarse Drainfill

54 Drain Pipe Detail

55 Drainfill Placement

56 RCC Placement

57 Finished RCC Lift

58 Bear Creek 12 North Carolina Low Hazard Spillway Repair RCC Drop Structure

59

60 Drop Structure Plan

61 Drain Section

62 Drain Construction

63 Geocomposite Drain

64 Geocomposite Drain

65 RCC Placement