Lake Delhi Dam Breach - Two Perspectives

On July 24th, 2010, after nearly 90 years of operation, the Lake Delhi Dam experienced what is believed to be a record inflow of water (based on recorded flows at a USGS gaging station on the Maquoketa River in Manchester, Iowa and estimated flows between the gaging station and Delhi Dam) that exposed long dormant design deficiencies and unrepaired maintenance problems. The record inflow coupled with design deficiencies and uncompleted repairs spelled disaster for the structure that had stood strong for so long. While Iowa’s staff of one full time dam safety technician had regularly inspected the dam and requested that repairs be completed in a timely manner, the Iowa DNR was not in a position to begin a full scale failure investigation. However, the State was fortunate to receive the assistance of members of the national dam safety community to begin a dam failure investigation. Ultimately, the National Dam Safety Review Board agreed to convene an Independent Panel of Engineers (IPE) to review the operational characteristics of the project leading up to the breach; perform an evaluation of the breach of the dam to determine the specific failure mode; and submit a final report documenting the results of their findings on the cause of the breach of the upper reservoir and the important lessons learned.
The IPE operated independently and access to individuals and to any requested information was freely granted. Areas of focus included: the design and construction of Delhi Dam; subsequent modifications to the dam; the operational and performance history of the dam; past examinations and reviews of the dam; the timeline of events involved in the breach of Delhi Dam; the post-breach condition of the dam; and the emergency response to the dam breach. The findings of the IPE are included in a detailed written report.
This first part of this paper will discuss the steps Iowa’s Dam Safety staff took prior to and immediately following the dam breach and the process used to request assistance through the National Dam Safety Review Board to convene an Independent Panel of Engineers. The second part of this paper will focus on the Independent Panel of Engineers (IPE) findings regarding Lake Delhi Dam Breach. Lessons learned from both the State and the IPE perspective will be presented. 21 pp. 2 references.