Design survey work flags and tags trees within the work zone to measure any environmental impact
Users of a popular section of the Gerry Connolly Cross County Trail in the Pohick Stream Valley are noticing tree markings and other activity not normal to the quiet, beautiful and shady trail which runs along the rocky stream. What is the purpose of the flagging tape and numbered discs tagging the trees along a long stretch of the trail?
One doesn’t usually expect to see a focus on trees for this type project. The project primarily renews and rehabilitates sanitary sewer pipe and manhole structures along the creek and trail. Existing pipes in the waste water system in Mount Vernon and Springfield Districts along a 1.2 mile linear distance, have been evaluated as “at risk of failure.” Anna Neugebauer, a branch chief in the County’s Wastewater Collection Division, says aging pipes being at higher risk, are targets for rehabilitation to prevent pipe collapse. While her office has no other projects of this scale going on now, Neugebaruer says system rehabilitation is routine throughout the county to maintain system operation and avoid problems.
This project, now in the design phase, is estimated to be through the bid process in January 2024 and be in construction for one year, beginning in early summer 2024. The construction cost, preliminarily estimated at $14 million, is fully funded through sewer service fees, not taxes.
The existing pipes will be renewed in place. The method, called Cured-in-Place-Piping, can improve the system with considerably less disruption and cost. Instead of digging up old pipes, opening earth trenches, new pipe made of a soft material impregnated with resin is fed through, as a liner to old pipe, then hardened in place, using either hot water, steam, or ultra-violet lamps. The hardening method used here has not yet been selected this early in the project design phase.
A trenchless system rehabilitation will have less impact on trees and other environmental factors at the project site. So why are the trees a focus? Neugebauer says that data collected on the size and health of trees in the construction area is shared with the county’s Park Authority. Should trees be impacted by work around them, the Park Authority can decide what replanting or other intervention is warranted.
The negative project aspect that can not be avoided is trail closure. The work area includes the stream valley below Pohick Road on one side and developments on the ridge near Gwynedd Way, Godolphin Drive, and St. George Court on the other side of the stream, beginning at Wadebrook Terrace. Pedestrian trail closures are likely for up to a year. With the work completed in phases, some detour paths will divert trail users to the sidewalk along Pohick Road for a portion of the project duration. Users can expect to see posted signs in advance of trail closure.
Although users may miss use of this favorite trail, the completed work means the system is renewed for the next 50 years.
For project updates, see Project Number WW-000028-013, at https://www.fairfaxcounty.gov/publicworks/capital-projects/pohick-interceptor-rehabilitation-phase-1