Montclair Dam Spillway


Montclair Property Owners Association (MPOA)


Froehling & Robertson, Inc.


Montclair, Virginia




August 2018


The Montclair Dam Spillway Upgrade Project consisted of the construction of a buried concrete cutback wall to meet the requirements of DCR regulations for the dam and spillway at Lake Montclair. The purpose of the cutback wall in the spillway of the dam is to prevent erosion of the spillway in the event of flood waters entering the spillway. Other portions of the project included constructing a brand-new parking lot and entrance for the beach, installing a water and sewer service line for the beach, and placing a foot of new sand across the entire beach.

The spillway of the dam is a functioning sand beach that the Montclair Property Owners Association (MPOA) utilizes for their residents to enjoy throughout the summer and a location for various events. The cutback wall is located across the length of the beach and buried approximately 2 feet from the sand surface, to a depth of approximately 23 feet. In order to complete the project, not only was the beach was closed to residents, but Lake Montclair was closed to boaters to allow the lake level to be lowered by 20 feet. It was a priority of MPOA to complete this work quickly to minimize the amount of days in which the lake would be closed to residents.

Throughout the entirety of the project, known and unknown obstacles were presented which challenged the team to work through issues to find a solution that worked for all parties involved. One challenge of the project was the differing elevations of the bottom of the wall based on the location of the rock encountered onsite. It was a DCR requirement for the footing of the wall to be doweled into bedrock for additional strength of the wall. The team developed a 4D-model of the entire cutback wall with the 4th dimension being a time-based schedule detailing each separate concrete pour. As the construction progressed, the field conditions of the rock differed from the per plan location, and adjustments were made to the model to accurately reflect those changes. This tool allowed the team to plan the schedule, sequence, and formwork and rebar details to construct each portion of the wall.