Dead Run Stream Restoration Public meeting February 18, 2015
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Middle Potomac Watershed Plan Implementation Dead Run Stream Restoration Project Public Meeting McLean Community Center February 18, 2015 Stormwater Planning Division Department of Public Works and Environmental Services
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Transcript of Dead Run Stream Restoration Public meeting February 18, 2015
Middle Potomac Watershed Plan Implementation
Dead Run Stream Restoration Project
Public MeetingMcLean Community Center
February 18, 2015
Stormwater Planning DivisionDepartment of Public Works and Environmental Services
Meeting Outline
• Fairfax County DPWES and Stormwater Management
• Countywide Watershed Plan Implementation• Project Introduction and Objectives• Natural Channel Design Principles• Existing Conditions• Proposed Improvements • Next Steps• Questions?
Fairfax County Department of Public Works and Environmental Services (DPWES)
Department of Public Works and Environmental Services
Land Development
Services
CapitalFacilities Solid Waste Stormwater
Stormwater Planning Division
Maintenance and Stormwater
Management Division
Wastewater
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
Service Drivers
In response to The Clean Water Act of 1972…
National Pollutant Discharge Elimination System (NPDES)Virginia Stormwater Management Program (VSMP)
RegulationsMunicipal Separate Storm Sewer Permit (MS4)Total Maximum Daily Loads (TMDLs)
Chesapeake BayLocal Streams
Countywide Watershed Planning
“Healthy Watersheds, Healthy Communities”
• 30 Designated Watersheds
• All 15 watershed plans have been adopted by Fairfax County
http://www.fairfaxcounty.gov/dpwes/watersheds/
Middle Potomac Watershed Plan
• Watershed Characterization– Water Quality Monitoring– Land Use Change– Pollutant Loading
• Structural Project– 25 year plan
• Non-Structural Practices– Policy and Regulations
http://www.fairfaxcounty.gov/dpwes/watersheds/
Dead Run Watershed Plan
• Dead Run has a drainage area just over 3 mi2
• 24 priority projects identified in the watershed management plan
• Pond retrofits• LID Stormwater Enhancements• Stream Restoration• Neighborhood Stormwater
Improvementshttp://www.fairfaxcounty.gov/dpwes/stormwater/projects/project_list.htm
Approximately 1/3 of the roof is covered in vegetation. The benefits of a “living roof” include:• Reduces the amount of stormwater runoff• Absorbs air pollution and carbon dioxide• Reduces the energy needed to cool the building in summer
Partnership: LID Stormwater EnhancementsDolley Madison Library
Vegetated Roof- Delosperma and Allium plants in bloom
Partnership: LID Stormwater EnhancementsDolley Madison Library
Sustainable Site Design
Dead Run – Before & After
Drainage Area(acres)
Phosphorous Removal(lbs/yr)
Nitrogen Removal(lbs/yr)
Sediment Removal(tons/yr)
415 15 283 3
Stream Restoration
Dead Run – Stream Restoration
Stream Monitoring Program
Study Objectives1. Generate long-term monitoring
data.
2. Evaluate relations between observed conditions/trends and BMP implementation.
3. Transfer the understanding gained to other less-intensively monitored watersheds.
http://va.water.usgs.gov/projects/ffx_co_monitoring.htm
Dead Run Stream Restoration
Dead Run Stream Restoration
Segment 1 – Dominican Retreat• 2,000 Linear Feet
• Extends to Old Dominion Drive
• Residential lots along Merrimac Drive and Van Ness Court
Dead Run Stream Restoration
Segment 2 – McLean Central Park• 800 Linear Feet
• Completely in Park
• Starts below previously restored section near library
Dead Run Stream Restoration
Segment 3 – Dead Run Stream Valley Park• 1,500 Linear Feet
• Extends to Churchill Road
• Residential lots along Elizabeth Drive and Carol Rayes Street
Natural Channel Design
Background and Design Approach
Geomorphic Assessment of Stream Channel.
Dead Run Stream is between Stage III and V.
Understanding channel evolution informs the design process.
Dead Run Watershed Assessment
• Drainage area at upstream of Segment 2 is 380-acres
• Drainage area at downstream end of Segment 2 is 492-acres
• Drainage area at downstream end of Segment 3 is 685-acres
Evaluate Bankfull Channel design parameters and 100 year floodplain
Assessment of Channel Conditions using BANCS method, Bank Erosion Hazard Index (BEHI) and Near Bank Stress (NBS)
Representative photograph of Dead Run Stream channel conditions. Note tree impacts due to soil loss.
Representative photograph of Dead Run Stream channel conditions. This is tributary going up to tennis courts.
Representative photograph of Dead Run Stream channel conditions. This is within Segment 3.
Representative photograph of Dead Run Stream channel conditions. This is within Segment 3.
Representative photograph of Dead Run Stream channel conditions. Bottom of Segment 3 at Churchill Road.
What benefit does stream restoration provide? • Reduces soil loss, phosphorus and nitrogen nutrients. • TP reduction credits up to 2.6x the CBPO interim value and TN
reduction credits up to 5x the CBPO interim value.
• Evaluate tree conditions.• Inform design and
decision making.• Trees 12” and larger
located.• Significant effort has
been made to re-design channel to save and protect trees.
Concept Design Dead Run Stream Restoration
Segment 2 and 3
Representative Design Strategies• Dead Run Restoration will primarily
include a combination of Priority 3 and 4.
Priority 4Stabilize Channel In-Place
Concept DesignSegment 2 Upper
Concept Design Segment 2 Lower
Segment 3: Existing Conditions Analysis, Floodplain Areas
Segment 3: Existing Conditions AnalysisEasements, Utilities, Trails, Bridges, Properties
Ex. Sanitary Sewer
Segment 3: Concept Channel Layout
Proposed Channel
Segment 3: Evaluate Trees and Channel Design
Proposed Channel
Potential Tree Removal
Segment 3: Proposed In-Stream Structures Analysis
Proposed Channel
Potential Tree Removal
Proposed Structures
Modified Cross Vane
Looking upstream at boulder rock toe and constructed riffle
Looking upstream at boulder rock toe – 2 and 3 courses
Infill mix comprised of cobbles, gravels, sand, silt, topsoil
Larger material, usually cobble
Constructed Riffle(aka Reinforced Streambed)
Constructed Riffle
Segment 3: Evaluate the project limits and the area necessary to restore the stream* Save trees and minimize disturbance
Proposed Limits of Work
Segment 3: Evaluate Access Routes and StagingBenefits: Save trees, reduce trail closures, opportunities to re-landscape.
EntranceAccess
Next Steps
• Complete Preliminary Design including access options
• Public Meeting• Final Design• Project Construction
• FY2017/FY2018 - dependent on available funding• Community Coordination: Pardon our Dust
• Maintenance and Operation
Dipmani Kumar, [email protected]
Matt Meyers, [email protected]
Stormwater Planning DivisionDepartment of Public Works and Environmental ServicesFairfax County12000 Government Center Parkway, Suite 449Fairfax, Virginia 22035(703)-324-5500
www.fairfaxcounty.gov/dpwes/stormwater
Questions ?
• Contact Information
A Fairfax County Publication, February 18, 2015To request this information in an alternate format call 703-324-5500, TTY 711
