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Reston Section 24 Regional Stormwater Management Facility Repair and Rehabilitation Project Hunter Mill District
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Reston Section 24
Regional Stormwater Management
Facility Repair & Rehabilitation Project
Hunter Mill District
Project No. FX4000-DF006
Description and Overview:
This stormwater management facility (Facility ID 0067DP) is located on Reston Homeowner Association property within
the Difficult Run Watershed. The pond was originally built without adequate access to perform non-routine maintenance
such as sediment removal and structural repairs. This project was initiated because the existing facility was overtopped
during a storm event and severely eroded the emergency spillway and portions of the dam embankment. Also, the
upstream inundation area is wooded and the outfall structure tends to clog with debris and requires frequent
maintenance. To stabilize the emergency spillway and reduce the chance of dam failure, the capacity of the principle
spillway is increased by installing a larger size pipe and the emergency spillway is armored. To control the frequent
maintenance a larger size BMP trash rack is installed. A permanent maintenance road is installed to provide access for
all types of future maintenance work.
Project Scope of Work:
• The eroded emergency spillway was reconstructed and armored with CL-II rip-rap.
• The eroded dam embankment was reconstructed.
• The existing 48” corrugated principal spillway pipe was replaced with a larger 60” CL-III RCP.
• The existing riser structure was replaced by a large size (6’ x 6’ and 8’ high) structure.
• The pond was graded and sediments were removed to achieve the original storage capacity.
• Installed a 0.4 mile long permanent access road for future maintenance.
• Installed a Fair Weather Crossing capable for vehicular access.
• Restored the disturbed area using seeding and covering with coir fiber matting on all embankment slopes.
DPWES Project Team:
• Project Manager - Dipmani Kumar
• Construction Manager - Yousef Rayyan
• Project Inspectors - Yudhie Brownson & Jack Schambach
• Land Acquisition Agent - Carol L. Kresge
• Survey Analyst - Gregory Harper
Project Details
This stormwater management facility is located near Twin Branches and Snakeden Branch
in a low density residential area of Hunter Mill District and receives runoff from a 236 acre
drainage area. The access Road meanders through the woods along an existing pedestrian trail.
6’X6’ Riser
Location Fair Weather Crossing Site Entrance
Site Limits
Twin Branches Road - Tax Map No. 27-1
Stormwater Management Facility ID 0065DP
Pre-existing Condition: No adequate access
for maintenance
Post Construction: New permanent access
road for maintenance
Pre-existing Condition: Fair Weather Crossing
Post Construction: New Fair Weather Crossing
Dam Embankment
Pond Inflow
Pre-existing Condition: Sediment accumulation in pond and
blocked principal spillway pipe. Pond was originally
constructed with an outlet control structure (riser).
Pond Inflow
Debris Screen
Post Construction: New Control Outlet 6’X6’ Riser Structure,
disturbed areas were planted with native seed and
protected with Coir matting cover
Pre-Existing Condition: End Section of the Principal
Spillway 48” Corrugated Pipe
Post Construction: Endwall of the New 60”
Principal Spillway Pipe Culvert
Dissipater pool
Pre-Existing Condition: Severely Eroded
Emergency Spillway
Post Construction: Emergency Spillway
after Repairs
For additional Information, please call
Irene Haske, Public Information Officer
703-324-5821, TTY 711
www.fairfaxcounty.gov/dpwes