WRECO teamed up with Dokken Engineering and Geocon on this design-build project to update the outfall structures at Miller Lake Dam at Beale Air Force Base. Dokken Engineering was responsible for civil and structural design and Geocon was responsible for geotechnical design.
Miller Lake Dam is an earthen dam, constructed of rock fill, built in 1962. It consists of a 29-foot tall embankment with 814 acre-feet storage capacity. The dam is located along Reeds Creek with a 3.17 square mile watershed. The existing outfall structures consist of three 4’x3’ box culverts, a 36” pipe, a newly constructed spillway, and a non-functioning outlet works or low flow pipe. The dam has experienced several overtopping events, most recently in 1995 and 1996.
Miller Lake Dam embankment and the concrete emergency spillway
Improvements to the dam outfalls were modeled under several conditions and for storm events ranging from the 10-year storm event to the Probable Maximum Flood event. The results were that there would need to be four 6’x6’ box culverts installed on each abutment for a total of eight 6’x6’ box culverts to meet the necessary criteria. The outlet works were also replaced with a new, functioning system that consisted of a 30” pipe.
Downstream assessments were performed to determine the impacts of increasing the size of the dam outfall on the downstream properties. In addition, an unsteady HEC-RAS model was developed to simulate a dam breach at the site and to develop the inundation mapping. Hydrology and Hydraulic Reports are being prepared for all locations and will include an Operations and Maintenance Manual for both dams.
The Miller Dam Repair project won APWA Sacramento Chapter’s 2018 Project of the Year Award – Environment – Flood Control Category.