Rio Grande Dam - Seepage Reduction Design and Construction

Rio Grande Dam was constructed over 100 years ago near the headwaters of the Rio Grande in the San Juan mountains of southwest Colorado. The reservoir is impounded by an earthfill and rockfill dam built in a challenging geologic environment. The left abutment consists of a large heterogeneous rock slide deposit, while the right abutment is made up of fractured volcanic rock. Historically, the reservoir has experienced high seepage through both abutments and the dam foundation. A rehabilitation project was designed in 2012 and constructed in 2013 with the goal of reducing the seepage through the abutments and the foundation of the dam. A clay slope liner and clay blanket were constructed on the upstream face of the left abutment over the rock slide deposit to decrease seepage. A grout program was developed — utilizing real-time, computer-aided grout delivery monitoring — to construct a grout curtain into the fractured volcanic rock of the dam foundation and right abutment with the intent of infilling fractures to reduce seepage. Preliminary data, to date, indicate the rehabilitation project appears to have successfully reduced seepage through the dam foundation and the abutments by more than 50 percent of the historical average.