The Lake Montclair Property Owners Association (MPOA) owns Montclair Dam, a 74-foot-tall High Hazard earthen dam on Powells Creek in Prince William County, VA. MPOA constructed the dam as a recreational and aesthetic lake for the community. The Virginia Department of Conservation and Recreation, Office of Dam Safety, required an inundation Study and Spillway Stability Analysis to be completed as the first steps to obtaining a new Regular Operating Permit.

Invited to collaborate with Shirley Contracting, F&R completed an inundation study and mapping for use in the HOA’s EAP. The Inundation Study confirmed the dam was High-Hazard with no allowable spillway reduction. The existing spillway capacity was insufficient and proved erodible using SITES analysis of its current configuration, which included a beach at the lakefront and a parking lot as amenities in the spillway.

F&R performed a Preliminary Engineering Report (PER) with several options. The MPOA selected a concrete cutback protection wall and an increased spillway flow area to meet the required capacity and allow the amenities to be retained. F&R designed the spillway and managed its construction. At project completion, the dam received a new Regular Operating Permit.

F&R was awarded the HCCA’s Excellence in Infrastructure Award for our efforts in assisting the Shirley Contracting team.