Rehabilitated dam receives awards

BALTIMORE—The Loch Raven Dam has received nine national and regional engineering and construction awards since its dedication in September 2005. A gravity dam originally constructed in 1914 and subsequently enlarged, Loch Raven underwent a three-year rehabilitation to prepare for future storms and to meet new federal guidelines.

Gannett Fleming, an international planning, design, and construction management firm, served as the prime engineer for the dam-strengthening project; the joint venture of ASI/Cianbro Corporation was the contractor.

Most recently, the Association of State Dam Safety Officials selected the Loch Raven Dam as the 2006 National Rehabilitation Project of the Year. This award recognizes a unique remedial design that advances state-of-the-art technology in the field of dam safety and exemplifies high professional engineering standards.

The Loch Raven Dam impounds 23 billion gallons of water and serves as a primary water source for the Baltimore region. Failure of the dam had the potential to cause a significant loss of life and property, as well as negatively impact the drinking water supply that serves nearly 1 million people. The goal of the Loch Raven Dam project was to bring the dam into compliance with current safety regulations, while maintaining the reservoir as a water source throughout the building period.

For the project, the team incorporated several innovative design and construction elements. Fifty-seven, high-capacity post tension anchors were designed to pin the existing dam to the underlying bedrock, increasing the dam’s stability during construction. Approximately 50,000 cubic yards of roller-compacted concrete were also produced on-site and placed against the front of the dam, adding substantial mass and changing the profile of the gravity base structure. Steel gates were designed in the non-overflow section to maintain access to Loch Raven Drive, resulting in considerable cost savings.

Delivered five months ahead of schedule, the Loch Raven Rehabilitation Project was completed nearly $500,000 under budget. As a result of the project, the structure was rehabilitated to withstand the most severe storm conditions expected during the regulatory-defined probable maximum flood.

Gannett Fleming performed the study, design, and construction phase services for this project and was responsible for all on-site materials testing. Additionally, the firm assisted the city in conducting a significant community outreach program. Meetings, site visits, and regular print and Internet updates helped to educate the public about the project.