Public Works and Environmental Services

CONTACT INFORMATION: Our administrative offices are open 8 a.m. – 4:30 p.m., Mon - Fri
703-324-5500 TTY 711
12000 Government Center Parkway
Suite 449, Fairfax, Va 22035
Joni Calmbacher
Director, Stormwater Planning

Colvin Run Phase II at Lake Fairfax Park Stream Restoration

Project Update: January 26, 2024

  • Notice to Proceed with Construction was issued on October 30, 2023.
  • The Construction Contract duration is 500 days.
  • Construction of Reach 2, nearby Hunter Mill Rd., is scheduled to be complete in April 2024.
  • Construction of Reach 1, between Lake Fairfax Drive and the Cricket Fields, is scheduled to be complete in April 2025.

Project Background

This project is a continuation of the Colvin Run Phase I project, Difficult Run Watershed Management Plan project DF9213, completed in 2018, and includes the restoration of approximately 4,454 linear feet of channel along two severely incised and over-widened tributaries to Colvin Run within Lake Fairfax Park.

Project Description

looking upstream outer bank erosion
Looking upstream outer bank erosion in upper reach of main stem
looking upstream at incised channel in lower reach of main stem
Looking upstream at incised channel in lower reach of main stem

The goal of the project is to improve water quality through restoration of approximately 4,454 feet of stream channels by returning the physical characteristics of the channel to dynamic equilibrium and enhancing the ecological functions and processes within the riparian corridor. The project will improve water quality through creating sustainable channel dimensions, profile and pattern, installation of grade control structures, improving floodplain connectivity, reducing erosion, installing native vegetation, enhancing existing floodplain wetlands and enhancing the ability for biogeochemical processing of phosphorous, nitrogen and suspended sediment within the channel and on the floodplain.

Grade control structures to be installed within the stream channel will mimic bedrock outcrops and beaver dams, and include rock sills, step pools, cascades, riffles, boulder riffles and large woody debris jams. These grade control structures are made of boulders, clay, logs, limbs and reinforced bed material. At-grade rock sills will extend outward from several of the in-stream grade control structures to prevent erosion on the floodplain and protect existing wetlands along the riparian corridor. The stream restoration design minimizes disturbance to natural resources by using the existing footprint of the channel to the greatest extent possible and realigning the channel only where necessary to protect infrastructure and to achieve the most sustainable restoration potential

Project Location

The project is in the Hunter Mill Magisterial District in Lake Fairfax Park.

Aerial photomap showing the proposed work areas. Indicated are Hunter Mill Rd Construction Entrance & Construction Access Pathway, Restoration Reach 1, Restoration Reach 2 and Construction Entrance.

Aerial photomap showing the proposed work areas. Note: This graphic does not show the full extent of the project’s Limits of Disturbance (LOD). Trail closures and detours will be in place during construction. For the safety of park users, only designated construction staff are permitted to be within the project’s LOD. The project’s LOD is delineated by blaze orange safety fencing.

Project Phase


Project Benefits

  • Restore and maintain aesthetic and recreational benefits for County residents and park users
  • Protect and improve water quality in the Difficult Run Watershed, Potomac River and Chesapeake Bay
  • Significantly reduce streambank erosion
  • Establish a stable stream and riparian buffer planted with a diverse mix of native vegetation
  • Protect at risk infrastructure (trails, footbridges and road culverts)
  • Annual Water Quality Benefits:
    • Total Suspended Solids load reduction of 188,265 lbs/yr
    • Total Phosphorous load reduction of 586.27 lbs/yr
    • Total Nitrogen load reduction of 1,432.78 lbs/yr


What to Expect

Construction access into the project area will be from Lake Fairfax Drive, the driveway to the Cricket Field and Hunter Mill Road.

When construction begins, fencing will be installed to delineate the limits of disturbance and tree save areas.  Construction equipment and materials will be transported from staging and stockpile areas to the active work areas along stabilized construction access pathways.  Signage for construction vehicle access will be posted along the roadways and trails. Portions of the Rails to River Trail and Cliff Hanger Trail, which cross the work area, will be closed during construction and signage will be posted for trail detours around the work area.  The main channel and tributary crossings along the Cliff Hanger Trail, west of the Cricket Field and upstream of the pedestrian bridge, will be slightly relocated and improved during construction.  There will be temporary closures of the roadway from Lake Fairfax Drive to the large shelter/picnic area and public restrooms during active construction activity in that vicinity and during the time required for replacement of the road culvert.

Construction activities will occur throughout the week starting after 7 a.m. on weekdays. Note that at some periods during construction work may occur on weekends after 9 a.m.  Construction activities are permitted until 9:00 pm throughout the week and weekend.  These start times are in accordance with the Fairfax County Noise Ordinance.

Project Cost and Funding Source

The project costs are paid for by the County’s Stormwater Service District. The cost of project design is $975,000. The cost of project construction is $3,630,000.

Presentations to the Community

Colvin Run Phase II - Stream Restoration Presentation, August 17, 2022.


For more information, please email the Project Manager, Justin Pistore at within the Stormwater Planning Division, Department of Public Works and Environmental Services, or call 703-324-5685, TTY 711.

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