ONE has worked with an industrial client in Blue Ridge region of Virginia to design and install a petroleum cut-off wall on the bank of a major regional river.
The cut-off wall was designed, using hydrogeologic modeling, to stop a historic diesel plume from migrating into the river while still allowing groundwater to flow under the wall to recharge the river. The installation trench, and pre-installed recovery sumps, also serve as a product accumulation and recovery system.
A brief synopsis of the project is as follows:
- Pre-Installation Design Tasks
- Analysis of historic groundwater elevations trends
- Hydrogeologic modeling of the impact of the wall on groundwater flow
- Selection of a hydrogeolocially appropriate backfill for the cut-off wall trench
- Petroleum Cut-off Wall Installation Tasks
- Demolition of unused infrastructure in the project area
- Excavation and backfilling of the wall trench and installation of recovery sumps
- Precision installation of the cut-off wall panels. Terminal depth of the wall panels could not deviate more than ±0.05-foot from the design specifications
- Post-Installation Tasks
- Installation of a clay cap over the over the trench to prevent water infiltration
- Final grading and surface restoration to prevent scouring
- Vacuum development of recovery sumps
- Long term monitoring and product recovery in the trench