Botetourt County Completes Dam Safety Study, Orchard Lake Dam Classified as High Hazard
Botetourt County has completed a state-required safety study of Orchard Lake Dam, which found that the dam should be classified as a "high hazard" structure under Virginia's dam safety regulations. This classification is based on what could be affected downstream in the unlikely event of a breach, not an indication that the dam is unsafe or at risk of failing now. The report will be submitted to the Virginia Department of Conservation and Recreation (DCR) for review.
Orchard Lake Dam is an earthen dam located in the Amsterdam District on a tributary of Tinker Creek, about three-quarters of a mile upstream of Catawba Road. It holds back a roughly 13.5-acre lake and is jointly owned and maintained by a private landowner and Botetourt County. The dam serves as both a stormwater management facility and a recreational amenity for the Orchard Lake neighborhood.[BW1]
Why Was This Study Needed?
Dam owners in Virginia are required by state regulations to understand what would happen downstream if their dam were ever to fail. This is done through something called a Dam Break Inundation Zone (DBIZ) study — essentially a detailed engineering analysis that maps out how far and how fast water would travel if the dam broke, and what it would affect along the way.
Orchard Lake Dam did not have a current study like this on file with the Virginia Department of Conservation and Recreation (DCR), the state agency that oversees dam safety. To meet this requirement, the County hired Timmons Group, an engineering firm, to conduct the study.
Study Findings
Using detailed computer modeling of rainfall, streamflow, and the dam's structure, Timmons Group evaluated several "what if" scenarios, including a sudden failure during normal conditions and failure during major storm events.
The study's key conclusion: Orchard Lake Dam should be classified as a "high hazard" structure under state dam safety regulations.
It's important to understand what this classification means — and what it doesn't:
- It is not a statement about the dam's current physical condition or an indication that failure is imminent. The "high hazard" label is a technical classification based on what would be affected if a failure were ever to occur.
- The classification is based on the fact that a dam failure would put three downstream homes and nearby roadways within the flood path before floodwater would naturally spread out and diminish.
- State regulations use hazard classifications to determine how strong a dam needs to be built and maintained. Under the rules, high-hazard dams must be able to safely pass a very large, rare storm event without overtopping. The study found that Orchard Lake Dam's current spillway is not large enough to do this. This means upgrades will likely be needed to bring it into compliance.
The Next Steps
The full study report will be submitted to DCR for its official review. Timmons Group has started a follow-up alternatives analysis, which will look at different engineering options for upgrading the dam to meet state requirements. This second study is expected to be finished later this fall, and the County will share updates as more information becomes available.
The combined cost of the DBIZ study and the upcoming alternatives analysis is $79,450. The County applied for two Virginia DCR grants totaling $67,450 to help offset most of that cost. Unfortunately, DCR was unable to award either grant due to a lack of available state funding, so the County has covered these costs directly.
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