Seismic Evaluation and Remediation of Croton Dam

The seismic stability of the Croton Dam left embankment was evaluated for potential earthquake ground motions. Design ground motions were selected for a maximum credible earthquake of magnitude 6+ with peak horizontal bedrock acceleration of 0.1g. Field and laboratory test results were used to characterize the static and dynamic properties of the embankment and foundation materials. Static finite element analyses were performed as well as dynamic SHAKE analyses to evaluate the expected performance of the embankment. Results showed liquefaction and strength loss in certain zones of the embankment resulting in large deformation of the slope. Remediation of these areas of the dam was necessary. Various techniques were evaluated including drainage, construction of a berm at toe, vibro-grouted stone columns and compaction grouting. Compaction grouting was selected.