Officially known as the Headwaters Control Structure, this structure is most often referred to as Gray's Bay Dam. It is the starting point and source of Minnehaha Creek, which flows into the Mississippi River some 22 miles downstream.

The historic level of Lake Minnetonka was probably about 925 feet in elevation. A mill was established in 1853 near the present day intersection of Minnetonka Road and Plymouth Road just east of I-494. That mill included a dam that raised the level of Minnehaha Creek as much as 12 feet. This raised the level of Lake Minnetonka to about 932 feet in elevation. The higher water levels allowed packet boats to travel from the mill site to settlements along the lake.

The Minnetonka Mills closed in 1886 and burned in 1902. At some point during that interval, the dam at Plymouth Road was removed. To prevent the lake levels from falling too far, a wooden weir was built at this location in 1897. That structure was rebuilt in 1932 and again in 1944. A more significant headwater control dam was built in 1979. That that time, a study determined that the ideal lake level is 929.4 feet above sea level. The control structure is adjusted to maintain that level as much as possible. However, evaporation often has a greater impact on water levels, so the lake sometimes falls below this target level.

The Minnehaha Creek Headwaters Park and the Headwaters Control Structure were extensively remodeled in the mid-2000s. A deck was added in 2005, and the pedestrian bridge was added in 2006. The pedestrian crossing uses a long catwalk across Gray's Bay to connect to the regional rail system. The observation decks and picnic tables make for great places to stop and watch birds or do a little fishing.

The photo above is looking west towards the outflow side of the control structure. The pedestrian bridge is on the near side of the dam. The photo below is looking north towards the dam from the park on the south side of the bay.

The photo above is looking north along the outflow side of the dam from the south shore of Minnehaha Creek. The photo below is a similar view from the north shore of the creek.

The photo above is a view of the deck that is located on top of the dam. The metal plates give access to the three control gates located below the deck. The photo below is a view looking northeast across Gray's Bay, which is an eastern lobe of Lake Minnetonka.

The photo above is a close view of the downstream side of the control gates. The dam is fully closed on this late fall morning. The photo below is the lake side of the dam. Note that water levels are about 8 inches below the normal target levels.

The photo above is looking south towards the dam structure from the earthen embankment that makes up a majority of the dam. The photo below is looking north from the same location. The chain link fence blocks access to the majority of the embankment.

These two photos are views of the earthen dam embankment. The horizontal structure is a cap that was placed on a wall of sheet pile that has been driven into the embankment to stabilize the structure. The lake is on the far side of the dam in each of these two views.