U.S. Army Corps of Engineers, St. Louis District

DAM SAFETY EVALUATIONS

Eastern Missouri

Under contract with the St. Louis District Corps of Engineers, Reitz & Jens provided Phase I Dam Safety Evaluations of non-Federal dams throughout the District boundaries on an as-needed basis. The purpose of this evaluation was to determine whether the dams could qualify for registration permits from the Missouri Dam and Reservoir Safety Council. From 1978 through 1980 a total of 18 dams were evaluated and formal reports were completed.

The dam safety evaluations included:

• determination of watershed hydrology through both record research and field reconnaissance
• evaluation of dam stability by field survey of the dam section, some geotechnical sampling of dam materials, slope and global stability analysis
• evaluation of dam hydrology by field measurement of emergency spillways and routing various storm events through the dam using HEC-1 software
• evaluation of dam seepage by field inspection.

The downstream hazard rating and PMP capacity of the existing spillways were calculated to evaluate dam compliance with registration regulations. The reports summarized the findings, provided recommendations for upgrades or maintenance depending on the dam size, dam condition, and downstream hazard rating. All dams evaluated for the non-Federal earth fill dams ranged from 45 to 60 feet in height.

As part of a Miscellaneous Geotechnical Services Contract with the St. Louis District in 1995, Reitz & Jens completed an erodability study of the emergency spillway of the Lake Wappapello Dam. In 1998, the District again contracted with RJ to complete a through- and underseepage evaluation of this Federal dam. The main embankment of the Wappapello dam is approximately 70 feet high and 2700 feet long, constructed in the 1930s with non-homogeneous materials including high plastic clays, clayey sand and gravelly sands.

Since the completion of the original Corps dam safety evaluations in 1980, Reitz & Jens has routinely provided similar services on many other dam sites throughout the Missouri. These services have included design of new dams, dam safety evaluations, and remedial procedures to correct stability or seepage problems on existing dams.