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Huntington Levee Community Meeting January 16, 2014
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January 16, 2014
Building Design Branch
Huntington Levee Community Meeting
Building Design Branch
Purpose of Meeting
• Review levee conceptual design features and recommendations
• Receive feedback from the community on project features before moving forward with final design
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Agenda
I. Project Background
II. Conceptual Design Features
III. Accreditation
IV. Questions
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• June 2006 -160 homes were flooded from a storm event
• 2009 – US Army Corps of Engineers (USACE) completed a study to evaluate flood damage reduction measures in the Huntington Community
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Project Background
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• September 2011- Tropical Storm Lee caused damage to 160 homes in the Huntington Community
•November 6, 2012 – Fairfax County voters approved stormwater bond referendum to fund design and construction of flood damage reduction measurers
•November 9, 2012 – Fairfax County advertised for consultant design services
• June 2013 – Fairfax County awarded the levee design contract to ARCADIS
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Project Background
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Project Background
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• November 2013 – ARCADIS submitted the Phase I design package to Fairfax County
• Survey – 300 acre of aerial survey, 80 acre field survey, 26 field run cross sections of Cameron Run, utility survey
• Geotechnical Investigation – collection and analysis of 13 additional soil borings
• Wetland delineation
• Conceptual Design
• Review USACE 2009 study and conceptual design
• Evaluate potential refinements/alternatives
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Project Background
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• Phase II (January 2014-Winter 2017)
• Schematic Design (30%)• Design Development (60%)• Permitting• Land Acquisition• Construction Documents (100%)• Bidding
• Phase III (Winter 2017-Spring 2019)
• Construction
• Original schedule condensed by 7 months
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Project Background
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Conceptual Design Features
• Collection Drains vs. Cut Off Wall• Pump Station Location• Stormwater Diversion • Earthen Levee vs. Earthen Levee/I-Wall
Combination
Key Design Considerations
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Collection Drains vs. Cutoff Wall
Pros• Lower cost
• Ease of construction
Cons• Maintenance of toe
drainage pipe
• Higher risk of piping thru levee due to clogging of toe drain
• Additional pumping capacity required (6,700 gpm)
Pros• No maintenance
of toe drainage
• Reduced risk of piping thru levee
Cons• Higher cost
• Specialized construction
• Concern that it could raise groundwater levels and flood basements
Collection Drain (Recommendation)
Cut Off Wall
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Potential Pump Station Locations
Westside SWPSLocation
Eastside SWPSLocation
Central SWPSLocation
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Center of Levee Western End Eastern End (Recommendation)Property requirements
• Fairfax owned park property
• Would occupy space otherwise available for the excavated ponding area or park recreation area
Permanent Access• From Liberty Dr. over raised road
through excavated ponding area - Very exposed during storm events, safety concern
Neighbor concerns / buffering• In center of neighborhood park
recreation area
• Very visible from neighborhood
Drainage• Requires a third channel to
Cameron run with additional wetlands impacts and maintenance
Property requirements• Adjacent commercial parcel is
ideal, but prohibitively costly
Permanent Access• Easy access off Fenwick Dr. or
new access road from Metroview Pkwy.
Neighbor concerns / buffering• Very close to homes at Fenwick
Dr.
Drainage• Divert all flow to Western end
• Slightly smaller diversion channel than Eastern option
Property requirements• Fairfax owned park property
Permanent Access• New access road from Hunting
Creek Rd.
Neighbor concerns / buffering• Far from residential properties in
Huntington Neighborhood
• Buffered by wooded area
• Backs up to apartment complex recreation area
Drainage• Divert all flow to Eastern end
• Slightly larger diversion channel than Western option
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Potential Pump Station Locations
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Stormwater Diversion
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Stormwater Diversion Options
Grass Lined Drainage Ditch• Erosion concern from high
flow velocities
• 30’ wide @ 2:1 side slopes
• Maintenance concerns and mowing
• Standing water concerns due to flat grades
• Lowest installation cost
Concrete Drainage Ditch• Not as wide due to steeper
side slopes (1:1 = 15’-20’ or vertical = 10’)
• Fence to prevent access• High construction cost for
cast in place• Less maintenance than grass
lined
Precast Concrete Box Culvert
*Recommendation• Limited access points –
security bars to prevent entry
• Buried – any potential standing water is not exposed
• Precast construction – culvert segments trucked to site
• Maintenance - confined space entry
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Earthen Levee vs. Earthen Levee/Wall Combination
Earthen Levee Earthen Levee / I-Wall Combination
(Recommendation)Pros• More natural aesthetic
• Clear access to Cameron Run
Cons• Higher cost
• Generates greater construction traffic
• Greater overall levee mass, width varies from 60 feet – 85 feet
Pros• Reduced construction traffic
• Lower cost
• Smaller overall levee mass, width reduced by 17’
• Reduced backwater impacts
• Reduced impact to treesCons• Maintenance of wall
• Access thru wall
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Examples Architectural Facades
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Earthen Levee/Wall Combination
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Earthen Levee
Earthen Levee / I-Wall Combination
Levee Cross Sections
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Earthen Levee/Wall Combination
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Earthen Levee/I-Wall Combination
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Accreditation
• Levee will be designed to meet FEMA accreditation standards
• Fairfax County will submit an accreditation package to FEMA for their consideration
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Questions
Contact Information – Huntington Levee Project Phone #: 703-324-5800 Email address:
Contact Information – Stormwater Questions Phone #: 703-324-5821 Email address:
Huntington Levee Website: www.fairfaxcounty.gov/dpwes/huntingtonlevee
To request this document in an alternate format call 703-324-5800, TTY 711.
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