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 Solution Permanent Solution Construction Questions
Background – Location DC Fairfax County Alexandria
Tropical Storm Lee Fairfax DC County Alexandria
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
Outline Background Site Conditions Immediate Response Temporary Solution Permanent Solution Construction Questions
Before Lee Neighboring Utility Sewer Fairfax County Sewer
After Lee Neighboring Utility Sewer Fairfax County Sewer Damaged Sewer
Site Conditions (After Lee) County 36” Encased Concrete Sewer Weir Apron Low Flow weir Cut into Dam Concrete Dam with Z-pile
Apron Void
Causes for Damaged Pipe Large high intensity flows in Holmes Run Scour caused by high flows Earthquake?
Outline Background Site Conditions Immediate Response Temporary Solution Permanent Solution Construction Questions
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
Pumps Silent pumps to limit disturbance to surrounding community 24 pump monitoring to prevent overflows High Cost
Outline Background Site Conditions Immediate Response Temporary Solution Permanent Solution Construction Questions
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
Connection to Adjacent Sewer Neighboring Utility Sewer Fairfax County Sewer New Sewer Damaged Sewer
Temporary Structure Features Canal Gate Pipe Slope
Outline Background Site Conditions Immediate Response Temporary Solution Permanent Solution Construction Questions
Permanent Solution Drop Manhole Micropiles Structural Steel Protecto 401 Stream Bank Protection Stream Restoration
Permanent Crossing Overview Neighboring Utility Sewer Fairfax County Sewer New Sewer New Manhole
Drop Manhole Lowers the elevation of the pipe in the stream Allows for better pipe protection and armoring
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
Structural Steel Gussett Plate Lacing Transversal beam Longitudinal Beams Cradle Stiffener Plate Bents
Pipe and Protecto 401 36” Diameter Ductile Iron Pipe Protecto 401 Liner Selected
Stream Bank Restoration Coir Block Soil Lifts at Construction entrances
Stream Restoration Upstream and Downstream of the Weir Apron Reinforced Bed Mixture Stream Base Fill Imbricated Rock
Stream Restoration - Downstream
Low Flow Weir Cut Out
Outline Background Site Conditions Immediate Response Temporary Solution Permanent Solution Construction Questions
Construction PortaDam Goose
Porta Dam
Porta Dam
Porta Dam
Dry Site
Dry Site
Goose on Site
Outline Background Site Conditions Immediate Response Temporary Solution Permanent Solution Construction Questions
Acknowledgements Jonathan Okafor Mike Pekkala mpekkala@greeley-hansen.com Jonathan.okafor@fairfaxcounty.gov Clyde Wilber Thomas J. Russell cw@clydewilberllc.com Thomas.russell@fairfaxcounty.gov Carlos Englert Sam Shaikh cenglert@schnabel-eng.com Sam.shaikh@fairfaxcounty.gov Qamar Kazmi Brendan Schillo qkazmi@schnabel-eng.com Brendan.schillo@fairfaxcounty.gov Mohammad Nasim Ken Eyre mnasim@schnabel-eng.com keyre@greeley-hansen.com Gary Ferrante gferrante@greeley-hansen.com Ed Gerulat egerulat@greeley-hansen.com
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