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A Winding Road: Building a Sustainable Sanitary Sewer Stream Crossing in Emergency Conditions APWA Mid-Atlantic Conference Virginia Beach, VA May 10, 2013 Outline Background Site Conditions Immediate Response Temporary

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A Winding Road: Building a Sustainable Sanitary Sewer Stream Crossing in Emergency Conditions

APWA Mid-Atlantic Conference Virginia Beach, VA May 10, 2013

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Outline

 Background  Site Conditions  Immediate Response  Temporary Solution  Permanent Solution  Construction  Questions

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Background – Location

DC Fairfax County Alexandria

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Tropical Storm Lee

DC Fairfax County Alexandria

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Tropical Storm Lee

The Holmes Run Crossing saw 8-10

inches of rain

Parts of Fairfax County received over

5 inches of rain in 5 hours

Rainfall equated to 500-1000 year

storms in parts of Fairfax County

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Outline

 Background  Site Conditions  Immediate Response  Temporary Solution  Permanent Solution  Construction  Questions

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Before Lee

Neighboring Utility Sewer Fairfax County Sewer

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After Lee

Neighboring Utility Sewer Fairfax County Sewer Damaged Sewer

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Site Conditions (After Lee)

County 36” Encased Concrete Sewer Concrete Dam with Z-pile Low Flow weir Cut into Dam Weir Apron

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Apron Void

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Causes for Damaged Pipe

Large high intensity flows in Holmes

Run

Scour caused by high flows  Earthquake?

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Outline

 Background  Site Conditions  Immediate Response  Temporary Solution  Permanent Solution  Construction  Questions

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Immediate Response

By pass pumping in place within 48

hours of discovery of the break

Emergency Contractors  Adjustment of weir boards in an

upstream flow structure

 Working with neighboring agencies to

coordinate pumps and response

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Pumps

 Silent pumps to limit disturbance to surrounding

community

 24 pump monitoring to prevent overflows  High Cost

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Outline

 Background  Site Conditions  Immediate Response  Temporary Solution  Permanent Solution  Construction  Questions

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Temporary Solution

On land connection to the adjacent

trunk sewer

The connection is suitable dry

weather and smaller wet weather storms

 Allowed for time to design a long term

solution

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Connection to Adjacent Sewer

Neighboring Utility Sewer Fairfax County Sewer New Sewer Damaged Sewer

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Temporary Structure Features

Canal Gate  Pipe Slope

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Outline

 Background  Site Conditions  Immediate Response  Temporary Solution  Permanent Solution  Construction  Questions

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Permanent Solution

Drop Manhole  Micropiles Structural Steel  Protecto 401  Stream Bank Protection  Stream Restoration

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Neighboring Utility Sewer Fairfax County Sewer New Sewer New Manhole

Permanent Crossing Overview

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Drop Manhole

 Lowers the elevation of

the pipe in the stream

 Allows for better pipe

protection and armoring

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Micropiles

 14 micropiles in 7 pairs  Core reinforcement,

steel casing, grout

 Drilled into

disintegrated rock

 Drilled and not driven to

protect the weir and stream

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Structural Steel

 Gussett Plate  Lacing  Transversal beam  Longitudinal Beams  Cradle Stiffener Plate  Bents

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Pipe and Protecto 401

36” Diameter Ductile Iron Pipe  Protecto 401 Liner Selected

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Stream Bank Restoration

 Coir Block Soil Lifts at Construction entrances

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Stream Restoration

 Upstream and Downstream of the Weir Apron  Reinforced Bed Mixture  Stream Base Fill  Imbricated Rock

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Stream Restoration - Downstream

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Low Flow Weir Cut Out

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Outline

 Background  Site Conditions  Immediate Response  Temporary Solution  Permanent Solution  Construction  Questions

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Construction

PortaDam  Goose

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Porta Dam

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Porta Dam

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Porta Dam

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Dry Site

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Dry Site

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Goose on Site

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Outline

 Background  Site Conditions  Immediate Response  Temporary Solution  Permanent Solution  Construction  Questions

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Acknowledgements



Jonathan Okafor Jonathan.okafor@fairfaxcounty.gov



Thomas J. Russell Thomas.russell@fairfaxcounty.gov



Sam Shaikh Sam.shaikh@fairfaxcounty.gov



Brendan Schillo Brendan.schillo@fairfaxcounty.gov



Ken Eyre keyre@greeley-hansen.com



Gary Ferrante gferrante@greeley-hansen.com



Ed Gerulat egerulat@greeley-hansen.com



Mike Pekkala

mpekkala@greeley-hansen.com



Clyde Wilber cw@clydewilberllc.com



Carlos Englert cenglert@schnabel-eng.com



Qamar Kazmi qkazmi@schnabel-eng.com



Mohammad Nasim mnasim@schnabel-eng.com

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