Dam Award

At each annual conference, the Association of State Dam Safety Officials recognizes individuals who have made outstanding contributions to the field of dam safety. This year’s award winners were recognized on September 12th, at the 2006 ASDSO Awards Banquet in Boston. One of those awards was the National Rehabilitation Project of the Year, awarded to Gannett Fleming, Inc. for Loch Raven Dam. William B. Bingham, Vice President of Gannett Fleming, Inc. reports that “geotextile filter fabric in the drainage system including interface drains (old dam to RCC buttress), face drain (RCC to Facing Concrete), and foundation/toe drains” were used in the project.
Loch Raven Dam is a 131-foot high, 700-foot long concrete gravity structure owned by the Baltimore Department of Public Works. The dam impounds approximately 23-billion gallons of water in the Loch Raven Reservoir, the “crown jewel” of the water supply system for the greater Baltimore region.
A failure of the dam would jeopardize the lives of more than 3,000 people, public and private property, and vital infrastructure,
Accordingly, Maryland regulations require that Loch Raven Dam safely pass the probable maximum flood (PMF). When evaluated against this criterion, two major deficiencies were noted: inadequate factors of safety for structural stability, and insufficient spillway capacity. Maryland Dam Safety directed the City of Baltimore to rehabilitate or remove the dam.
City officials quickly concluded they had no choice but to rehabilitate the dam. They selected Gannett Fleming to design a solution that would increase the dam’s stability and confine PMF overflow to the 288-foot-wide spillway. To this end, Gannett Fleming decided to increase the structure’s mass, install rock anchor, and raise non-overflow sections of the dam.
Of prime concern during the development process was the reservoir’s essential function of supplying water for nearly a million people. Building a new structure downstream was not an option, nor was an alternative to widen the spillway. The solution: Renovate the dam in two steps, one half at a time, while maintaining normal capacity.
Throughout the three-year project, the contractor faced formidable challenges. Unusually frequent and heavy rainfalls caused overtopping of the spillway, complicating the diversion scheme. All work took place in a pristine watershed environment, in compliance with stringent regulations and under close scrutiny from the surrounding communities. In spite of these complexities, the project was completed five months ahead of schedule and $500,000 under budget.
The project was a great cooperative effort. The Maryland Dam Safety Program required the City to conduct additional investigations and to make needed repairs. The City, Gannett Fleming, and the ASI/Cianbro JV team created an excellent design and construction project. All performed their jobs admirably, and all deserve credit for the project’s success.