Dam features Iowa’s first labyrinth spillway
Lake Delhi Dam received the top award, the Grand Conceptor, in the annual engineering excellence competition held by the American Council of Engineering Companies (ACEC) of Iowa. The annual competition recognizes engineering projects that demonstrate innovation, complexity, achievement and value.
Designed by Stanley Consultants, the reconstructed dam features a labyrinth spillway, the first of its kind in Iowa and one of the largest in the Midwest. Rarely seen in the Midwest, the labyrinth design can pass high volumes of water across a short distance without using mechanical gates or electrical systems. The accordion-shaped spillway makes it possible, tripling its capacity to pass water as compared to a conventional spillway design.
A community-wide celebration was held at Lake Delhi last summer to mark the dam’s completion and the lake’s rebirth. It also marked the restoration of the small lakeside community. The event was held exactly six years from the devastating day when 12 in. of rain caused lake levels to raise 8.5 ft. The floodwaters overtopped and breached the earthen dam. In just a matter of hours, the popular recreational lake had drained, and the region’s economic engine was reduced to 450 acres of muck.
The community rallied, determined to rebuild the dam and restore the 9-mile-long lake, raising $1.7 million as seed money for the rebuilding. Lakefront property owners taxed themselves to the highest extent possible for a 20-year, $6 million dam reconstruction bond.
Rebuilding the dam met with opposition on multiple levels. Stanley Consultants, an Iowa-based engineering firm, played an essential role navigating the $13 million project through multiple roadblocks for the next six years. Completing the vast array of classification, permitting, and funding requirements took four years, followed by two years of construction.
During those six years the community of Delhi (pop. 470) and the entirety of Delaware County, felt the economic impact caused by the loss of the lake. Property tax revenue plummeted, property values plunged, construction around the lake slowed to a stop, and income streams for local businesses that depended on the lake traffic dried up. The recent reopening of the lake has reinvigorated the community. The lake is a beehive of recreational activity, construction has resumed, and local businesses are struggling to keep up with demand.
In October 2016, just weeks after the lake reopened, the dam was put to the test by the lake’s fifth largest recorded flood. The automated gates performed flawlessly and the floodwater passed with no significant rise in the water level near the dam.