The modifications to the dam were mandated by State and Federal Dam Safety regulations that required the rehabilitation of the dam to withstand future extreme flood events. Since Hurricane Agnes in 1972, engineers have been aware that the dam was vulnerable to overtopping during extreme floods.

The upper Loch Raven dam was originally constructed in 1912 to a height roughly 6m above the streambed. Ten years later, it was raised approximately 18m, to its current elevation of 88m asl. In the early 1970’s, structural improvements to the face of the dam, and mechanical improvements to the intakes were completed to supply drinking water to over one million people in Baltimore City, Baltimore County, Howard County, and Anne Arundel County.

The recent improvements added significant mass to improve the stability of the original gravity dam structure. Steel anchors were also installed through the dam and into the underlying bedrock. Silt and debris that have accumulated at the base upstream of the dam was removed, and roller compacted concrete (RCC) was added to stabilise the toe of the dam and to the face of the dam. The non-overflow sections of the spillway were raised by approximately 6m.