Lake Delhi Dam Reconstruction - A Good Dam Story

Abstract Only - This is the story of a community knocked down by a disaster and picking themselves up to restore a way of life. Lake Delhi Dam is located on the Maquoketa River southwest of Delhi, Iowa. During the flood event of July 23-24, 2010 a portion of the southern embankment was breached and the spillway’s gates were damaged. Flood waters infiltrated and seeped through a section of the northern embankment. For the next six years, Stanley Consultants worked side-by-side with the Lake Delhi Combined Recreational Facility and Water Control District to redesign, permit, fund and rebuild the dam.

A post-breach inspection was completed and alternatives developed for reconstructing the dam. The analysis involved subsurface and field investigations and data collection, engineering analyses, Dam Hazard Classification, preliminary design development and evaluation, and cost estimating. A labyrinth weir spillway which doubled the hydraulic capacity of the existing dam and rehabilitation of the existing spillway gate system was selected for design and construction. The design phase included embankment and structural stability analyses, seepage analyses, archeological and environmental studies, drawing and specification development, cost estimating, and construction scheduling.

Stanley worked closely with the Owner selecting optimal systems for each dam component considering maintenance, cost and aesthetics. One of the objectives of the design was to allow for the use of standard construction procedures and equipment minimizing the need for highly specialized contractors. This approach permitted the use of the local workforce and contractors.

Construction began in 2014 and was split into two phases to accommodate permitting requirements and expedite construction. Repair of the existing concrete structure and north abutment tie-in (Phase I) could be completed without impounding water, eliminating the need for a dam construction permit. This allowed Phase 1 construction to proceed while the application for the state permit was being processed. Once Phase I was substantially completed, allowing river flow to be passed through the gates of the repaired spillway, Phase II construction could begin. Construction was completed in 2016. This approach expedited construction, but also required Stanley to work with and coordinate between two Contractors.

During construction Stanley worked closely with the Contractors to address changed conditions encountered. These included old buried structures and foundation conditions varying from those indicated on the original drawings. working closely with the Contractor and Owner, Stanley engineers developed solutions that were constructible with workforce, equipment and materials readily available to the Contractor, reducing cost and delay.