Little Hunting Creek Sewer Line Replacement
A public meeting was held on Dec. 11, 2017, to inform local neighbors of County plans to replace a sewer line that runs under the stream bed of Little Hunting Creek.
The gravity-fed line serves 480 households in Wessynton and Woodland Park, and brings sewage across to the creek to the Little Hunting Creek pump station. From there sewage is pumped to Noman Cole Sewage Treatment Plant at Lorton.
The 12" cast iron pipe runs from Woodland Lane to Stockton Parkway. It needs to be replaced because it has sagged, which results in freezing problems, perpetual maintenance needs, costly emergency repairs, and risks to public health and the environment due to possible sewage backups or overflows. The pipe is the second most critical of County sewer lines at risk of failure. The sag is believed to be due to inadequate bedding support when the pipe was installed in 1961, or to other improper installation methods.
The County contracted with Arcadis Design and Consultancy to evaluate nine alternative engineering solutions to the problem based on six criteria: homeowner disruption, operation and maintenance, cost, permitting requirements, easements needed, and schedule. Three alternatives were identified as viable, and the recommended alternative was to construct a new pipe using coffer dams. A coffer dam is used to isolate the creek and expose the area of the creek bottom where the pipe will be laid. The area inside the coffer dam would be dewatered, then an excavator would be used inside the coffer dam to dig the trench for the replacement pipe. Coffer dams would be built in one section of the creek at a time. After the new pipe is constructed, it would be connected to existing sewer lines on both sides of the creek, and the old pipe would be abandoned. The new proposed sewer would pass through one private property, at 8616 Stockton Parkway, near the current pipe.
Design work will continue until May 2019. Preliminary work to be done includes geotechnical investigation of soil conditions under the creek, work to confirm the projected alignment, wetlands delineation, field survey, vegetation survey, and permitting. Construction is projected to take place from July through November of 2019. There will need to be construction access from both west and east shorelines of the creek (at Woodland Park and Stockton Parkway), and some clearing may be needed. Barges and other in-water equipment will need to be docked and moored.