By: Billie Swailes, PE
Civil Practice Leader
In October of 2019, a water leak was discovered at the Keedysville Springhouse, a public water source servicing 100% of the Town of Keedysville’s needs and 40% of the Town of Boonsboro’s. Erosion compromised the existing concrete weir wall used to maintain a pool elevation for the water intake pumps and water was escaping under the wall to such a degree there was the potential to lose the entire weir wall and pool. Triad was called by the Town of Boonsboro to meet, evaluate and discuss possible options for both a temporary and a permanent solution.
In the short term, we suggested the use of sandbags on the downstream side to raise the backpressure on the flow and equalize the flow. The Town had already begun to place sandbags in the upstream hole to slow the flow of water escaping.
For a long-term solution, Triad suggested pouring a new concrete cutoff wall along the entire inside of the existing weir wall. The new cutoff wall would bear on rock making it more stable and less susceptible to erosion. During our analysis, we also discovered repair work of the pool banks that were completed in 2016 were not stable and needed replaced. For this, we recommended imbricated riprap as the best option for stabilization.
With a plan for repairs developed, we met with Maryland Department of Environment (MDE) Wetland and Waterways Permitting to discuss the permitting needs for the repairs. Triad then performed a Wetland Delineation and a Topographic Survey of the area. We completed our design drawings and prepared the permitting applications to MDE.
During construction, there were unique obstacles to overcome. This water source is a spring that comes out of the ground through cracks in the limestone rock ledges. Thus, controlling the water during construction proved extremely difficult. The contractor could not seal all the ledges to stop the inflow. Instead multiple pumps and diversions were used to accomplish the work.
Triad employed a unique design feature of a clean water bypass system using sandbags to maintain the pool level at the pump intakes while bypassing the work area. The bypass system didn’t prevent all the water from coming into the work site, but the design maintained the critical pool elevation. The contractor used over 4,000 sandbags for this project.