Located in Illinois’ capital city of Springfield, the gated spillway at Spaulding Dam is a modern-day example of engineering ingenuity, historic preservation, and sustainable design.
Constructed around 1932 on Sugar Creek, the 1,600-foot earth dam created the Lake Springfield reservoir. The lake has a 4,200-acre normal pool and a 5,800-acre maximum pool at the top of the dam. At maximum pool, the spillway has a discharge capacity of more than 65,000 cubic feet per second. The dam featured a concrete and brick cutoff wall and a gated spillway with five floating steel-drum gates. The reservoir was designed to provide drinking water for city residents and supply water to cool City Water, Light & Power’s (CWLP) power-generation plant. The gated spillway controlled the lake’s water levels.
"We choose to work with Hanson because of the level of expertise in the field of study of a particular project." — Todd LaFountain, CWLP
After more than 70 years of continuous operation, Spaulding Dam’s owner, CWLP, determined that the dam was in need of rehabilitation. The gates — original to Spaulding Dam — were nearing the end of their service life.
The five gates were each 45 feet long and located between substructure elements of a historic concrete bridge. The gates operated under a vertical range of 0 feet to 8 feet. Each original gate consisted of a steel “pie-shaped” drum that was completely enclosed with steel-skin plates. One issue affecting the dam involved gate control. Each gate was individually and manually controlled by raising or lowering the water level in the chamber beneath each gate.
Hanson Inc's Engineering Services
In 2005, CWLP selected Hanson to evaluate the rehabilitation and replacement alternatives for the dam’s five floating steel-drum gates. Hanson was joined on this project by Bergmann Associates, a design firm with headquarters in Rochester, N.Y., that assisted with gate selection, construction plan and shop drawing reviews and site visits.
After evaluating seven potential gate types for Spaulding Dam, Hanson presented the options to CWLP. The city selected a hydraulically operated hinged-crest gate system. The gates offer reliability, stability, accessibility, safety, and technological upgrades and feature redundancies for the hydraulic power unit, electrical power and PLC controls.
The project also involved Hanson conducting a breach analysis and helping CWLP update its Emergency Action Plan. Hanson’s water resources engineers studied the impact Spaulding Dam could have on Springfield and downstream communities in the event of a probable maximum flood. Conducting one of the largest breach analyses in Illinois, Hanson studied more than 5,000 square miles of watershed. Engineers developed a watershed model that included more than 480 cross-sections spanning 150 river miles.
Hanson used GIS to model and map areas around Spaulding Dam and update CWLP’s Emergency Action Plan, identifying buildings, neighborhoods, and communities that might be affected during a dam failure.
The project team achieved a sustainable design by reusing some elements from the original structure to update and improve the operations at Spaulding Dam. Working in cooperation with the client and various permitting agencies, the project team kept the historic elements of Spaulding Dam intact while constructing a new gate system using modern design and construction techniques.