Seepage Investigation For Remedial Grouting, Crafton Hills Reservoir, California

Abstract

Abstract Engineering geologists are often tasked with a dam or levee seepage problem that needs to be repaired, but it is not clear where the seepage pathway is, how fast the seepage is flowing, or how best to repair the problem area. This article discusses a dam seepage area at the Crafton Hills Reservoir in San Bernardino County, CA. Upon refilling the enlarged reservoir, new seepage was observed in unexpected locations. Although the seepage amount appeared to be small, project managers decided to seal off the new seepage pathway utilizing subsurface grouting so the seepage would not become a long-term problem. In order to develop an effective remedial grouting program, additional subsurface information was needed. It was already known that the foundation materials are variable, likely have a variety of hydraulic conductivity values, and may respond differently to grouting depending on the pressures applied. Several methods were employed to determine the primary seepage pathway(s) and the range of pressures to use that would provide the most effective grout penetration. Although the geologic investigation led to some contradictory and unexpected results, the use of multiple testing methods provided a much better understanding of the foundation rock, which led to a more robust remedial grouting plan.