columbia road/randolph court stream restoration july 2015

A Fairfax County, VA, publication

Department of Public Works and Environmental Services

Working for You!

Columbia Road/Randolph CourtStream Restoration

July 6, 2015

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Columbia Road/Randolph Court Stream Restoration

Stormwater Planning Division

Meeting Outline

• Fairfax County Stormwater Management• Project Existing Conditions• Proposed Stream Restoration• Construction Access• Design Schedule• Questions

3Stormwater Planning Division


Stormwater Management

Department of Public Works and Environmental Services

Land Development

Services

CapitalFacilities

Solid Waste Stormwater


Maintenance and Stormwater

Management Division

Wastewater

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Stormwater Infrastructure

• Conveyance System– 1,600 miles pipe and

paved channel– 43,000 structures– 6,800 outfalls

• Management Facilities– 1,540 County Maintained – 3,720 Privately Maintained

• State Regulated Dams

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Service Drivers

In response to The Clean Water Act of 1972

• National Pollutant Discharge Elimination System (NPDES)• Virginia Stormwater Management Program (VSMP) Regulations• Municipal Separate Storm Sewer Permit (MS4)• Total Maximum Daily Loads (TMDLs)

– Chesapeake Bay– Local Streams



Watershed

Watershed: Cameron Run

Subwatershed:Indian Run



Project Location



Existing Conditions- 4717 Columbia Road

120 feet of failing gabion walls

Angled culvert outlet discharging at high velocity eroding gabion wall toe



Existing Conditions- 4717 Columbia Road



Existing Conditions - 4713 Randolph Court

100 feet of failing gabion walls

Sanitary sewer adjacent to gabion wall failure



Existing Conditions - 4713 Randolph Court

Runoff from grass floodplain eroding bank behind gabions

High velocity at stream bend eroding gabion wall toe



Existing Conditions Along Stream

Bottom sections of gabion wirerusted through and losing stone



Existing Easements

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Project Constraints

• Complex project design:– In-stream construction

• Diversion of main tributary around construction site• Stream construction access

– Gabion replacement requires Building Permit• County Land Development Services (LDS) structural review

– Other permit requirements:• US Army Corps of Engineers Permits• Virginia Stormwater Management Program Permit• FEMA “no rise”/”no impact” floodplain study

– Gabion Walls• Currently two failed sections• More gabion wall sections will fail in the future

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Indian Run Stream Restoration

• Stream restoration project proposed upstream of this project, from Indian Run Court to Columbia Road

• Combine Columbia Road/Randolph Court project design with Indian Run stream restoration


• This project will most likely be a combination of Priority 3 and 4 Restoration Approaches

• Limited by Columbia Road culvert invert

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Stream Restoration Structures- Cross Vane

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Stream Restoration Structures - Root Wads

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Stream Restoration Structures - Boulder Toe

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Stream Restoration - Bank Benches

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Proposed Resource Protection Area (RPA) Plantings

• RPAs - vegetated riparian buffer zone:– Protect water quality– Filter pollutants out of

stormwater runoff– Reduce the volume of

stormwater runoff– Prevent erosion

• Reduce the amount of mowed grass within RPA

• Sanitary sewer easement limits types of vegetation

• Plantings provide great benefits to homeowners

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Temporary Construction Access

• Maximum allowed slope of construction access road is 10%

• Project Site Constraints– Steep slopes

• 4717 Columbia Road = 35%• 4712 Randolph Court = 25%

– Mature trees– Existing driveways

• Two feasible temporary construction access routes



Temporary Construction Access - Option 1

Grade a temporary ramp from 4717 Columbia Road to project site. Ramp

to be removed and site restored following construction completion.

Construction access with hardwood matting to protect tree

roots from construction equipment.

Access stream with temporary ramp at the low point of gabion

wall

Staging and Storage Area



Temporary Construction Access - Option 2

Install a temporary construction access from 4705 Columbia Road to project site following existing sanitary sewer

easement. Site to be restored following construction completion.

Construction access with hardwood matting to protect tree

roots and sanitary sewer from construction equipment

Access stream with temporary ramp at the low point of gabion

wall Staging and Storage Area

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Tentative Schedule

• Initiate Design Task Order (1 month)• Conceptual Design (5 months)

– Stakeholders Meeting– County Review

• 95% Design (2 months)• Final Design (1 month)

Design Task OrderJuly 2015

Conceptual DesignAug 2015 - Jan 2016

Final DesignMar - Apr 2016

95% DesignJan - Mar 2016

Additional Information

For additional information, please contact

www.fairfaxcounty.gov/dpwes

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Catie Torgersen

703-324-5864

[email protected]

columbia road/randolph court stream restoration july 2015

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