Lake Christine Dam Rehabilitation

Challenges

Lake Christine Dam experienced a landslide in the natural slope (approximately 325 feet away from the dam). Safety concerns resulted in the Colorado Office of the State Engineer (SEO) restricting storage to 2.75 feet below normal pool. Colorado Parks and Wildlife (CPW) retained RJH to develop rehabilitation concepts for an unstable natural slope near an 18-foot-tall, 200-foot-long earthen embankment dam.

Solution

To better understand the relationship between the reservoir level and seepage in the slide area, RJH performed a test fill of Lake Christine.  The test fill included preparing and receiving SEO approval of a test fill plan, daily monitoring of the dam, reservoir elevation, outlet works flow, piezometer levels and seepage conditions at the dam and slide area, and preparation of a Test Fill Report. The reservoir level was slowly raised from its initial level below the restricted elevation to full pool elevation.  Multiple seepage locations were identified in the dam vicinity and in the natural slope in the slide vicinity.

RJH performed slope stability and seepage analyses of the natural slope in the vicinity of the slide to support design of a rehabilitation concept.  The selected concept included regrading the upper portion of the natural slope to a more stable angle, constructing a sloping drainage berm along the toe to safely collect seepage, and buttressing the slope with gabions.

RJH developed final design documents including drawings, specifications, and contract documents and provided engineering support during construction.