Resilient Stormwater Pump Station Systems in Virginia Beach
The frequency and severity of storms in the Virginia Beach area has increased significantly. Of the 18 coastal storms of record in Virginia Beach, 12 have occurred in the last 25 years. During one 6-week period in 2016, Virginia Beach experienced 35-inches of rainfall from three storms, or more than two-thirds of the average annual rainfall. Extreme weather, increased precipitation, sea level rise, land subsidence, and land development have greatly increased flooding impacts. Flooding conditions are worsened by older developments designed to lesser rainfall and tailwater criteria and often with constrained outfalls. The resultant recurrent flooding is a significant safety and quality of life concern.
Due to low-lying coastal terrain, a “berm, pond, and pump” solution is often required. The City has envisioned needing more pump stations in the future to protect its residents and has been establishing consistent requirements for pump station facilities. The requirements promote uniform pump station facilities which are a complex and significant infrastructure investment and promote uniform routine maintenance activities, storm preparedness and response activities during challenging storm events.
The planning and design of a resilient stormwater pump station system project with an automated tide gate, backflow prevention and interconnected pump stations will be presented. The project is in the eastern Shore Drive area and is in close proximity to the Chesapeake Bay which is a volatile and dynamic environment subject to tropical storms, Nor’easters, and heavy summer thunderstorms. The proposed system allows for the normal ebb and flood of tidal flow throughout the watershed and provides bypass pumping for 100% of the rainfall runoff around the tide gate when closed. Additionally, pre-storm canal drawdown by the pumps will provide storage volume for peak attenuation to provide an adequate level of service for the watershed and the principal urban arterial roadway. Tide gate closures will be automatically actuated by water level sensors but can be controlled remotely. Gate closure logic can employ predictive forecasting to prevent unnecessary pumping or to activate pre-storm drawdown based on anticipated climatic conditions. The resilient stormwater pump station system will protect the community against natural disasters and enhance the ability to recover from disasters.