Stuntzner Engineering & Forestry was requested to engineer a repair to an earthen dam in the mid-Willamette Valley. Stuntzner has considerable experience in earthen dams. The original dam was engineered and had some construction oversight by an engineer. A repair in this section of the dam had also been engineered, but had also failed. Other (not engineered) repairs in the section have also been completed, but all have failed. The dam is approximately 1000 feet long and 30 feet high. A 350 feet length of the dam has had a number of slides on the outside face of the dam. Stuntzner completed review of Dam Safety records, geotechnical investigation, engineering the repair, permitting, and construction observation.
The owners wanted the dam repaired in 2012, if possible; a very limited time frame. Stuntzner, therefore quickly hand-augured holes in the embankment to try to determine the cause of the continued failures. The borings revealed that the likely cause of the continued failures was both poor embankment materials and poor compaction. Stuntzner designed a repair and coordinated closely with Oregon Dam Safety and the owner to make sure all would be satisfied with the project.
Because the summer dry season is required to repair a dam with the assumed construction methods, the project was not expected to be completed in 2012. The research started in June, the investigations and design were done in July and permitting was obtained in August. The dam repair started in late August of 2012. The repair required removing approximately 350 feet of one end of the portion of the dam that had failed, then rebuilding with acceptable material. The soils in this area had to be dried before being compacted in the dam. The unusually dry summer and fall along with considerable coordination between the contractor, Stuntzner and the owner allowed completion on the last dry day of the year! We are still monitoring the site to watch out for erosion issues and to watch the dam repair as the dam fills.
This was an example of when government agencies, landowners, engineers, and contractors were able to work together to accomplish an important repair in a compressed timeline.