Shallow Marine MASW: A Case History and Lessons Learned

The concrete spillway associated with a small dam in Rapid City, South Dakota has evidenced persistent seepage since its construction in the 1970's. Visual inspection appears to indicate signs of worsening seepage. Geotechnical borings from dam pre-construction as well as modern boring logs taken on either side of the spillway have been consulted; however, budgetary, access, and logistical constraints restricted a more in-depth geotechnical boring program. A geophysical investigation was ordered to better define the subsurface stratigraphy. This data would be used to perform seepage/flow net analysis and determine some remedial solutions to mitigate seepage and extend the life of the structure.