NRCS Overview - Association of State Dam Safety Officials

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NRCS Overview - Association of State Dam Safety Officials

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


NRCS Dam Inventory

Significant Hazard: 2,200

High Hazard: 2,050

Total: 4,250

May 2011


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


Typical Filter Diaphragm Configuration

NRC S

NEH Part 628

Chapter 45

Filter

Diaphragms

FEMA


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


Typical Chimney Drain

Sloping chimney

filter/drain

Conduit

FEMA


• 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


Lost River 16

• West Virginia

• Water Supply-

Flood Control

• Completed ?

• Height 90 feet

Gannett Fleming Inc.


Typical Embankment Section


Drainage System Perspective

Gannett Fleming Inc.


Blanket Drain Typical Section

Fine Drainfill – ASTM C33 Fine Aggregate

Medium Drainfill – ASTM #8

Coarse Drainfill – ASTM # 57


Drain System Plan


Manhole Section

Pipe bend detail


New Creek 14

• West Virginia

• Water Supply-

Flood Control

• Completed

1963

• Height 110

feet


Excavation Plan

Gannett Fleming Inc.


Typical Section


Fine Drainfill – ASTM C33 Fine Aggregate

Coarse Drainfill – ASTM # 8

Blanket Drain Detail


Coarse Drainfill Placement in Blanket Drain


Welding HDPE Toe Drain


Placing Fill on Top of Blanket


Completion of Blanket Drain At Outlet


Construction of Chimney Drain and Berm


Toe Drain Access Manhole


Renwick Dam

• North Dakota

• Flood Control –

Recreation

• Completed

1962

• Height 50 Feet


Approximate Foundation Drain Location


12 inch diameter asphalt coated CMP


Excavation for Foundation Drain Inspection


Excavation for Foundation Drain Inspection


Exposed Foundation Drain Pipe


Cleaning Pipe


Second Drain Investigation Excavation


Open Joint in Pipe


Pipe Repair


Modified Drain Outlet


Millsite Dam

• Utah

• Water supply

• Completed

1972

• Height 115 ft.


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


Placing Zone III


Chimney Drain


Surface of Chimney Drain During Fill Construction


Conceptual Modified Section


• 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


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


Transverse

Crack in

Embankment


Upstream Approach

16-OZ Geotextile

URS


HDR Engineering Inc.

Filter Placement


Centerline Approach

16-OZ Geotextile

Ninyo & Moore


Trench Excavation


Filter Placement


Filter Placement


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


• Salado 15R

• TX

• Flood

Detention

• Completed

2005


RCC Plan


Section Through RCC Steps

Geotextile

Coarse Drainfill


Drain Pipe Detail


Drainfill Placement


RCC Placement


Finished RCC Lift


• Bear Creek 12

• North Carolina

• Low Hazard

• Spillway Repair

• RCC Drop

Structure


Drop Structure Plan


Drain Section


Drain Construction


Geocomposite Drain


Geocomposite Drain


RCC Placement

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