Hydrogeology of the Jointed Dolomites, Grand Rapids Hydroelectric Power Station, Manitoba, Canada
The Grand Rapids generating station, completed in 1964, is a 330,000 kilowatt hydroelectric installation located near the mouth of the Saskatchewan River on the west side of Lake Winnipeg, Manitoba, Canada. The operating head is some 130 feet. The 2000-square-mile reservoir is confined at its eastern end by concrete intake and spillway structures and 16 miles of earth dikes with a maximum height of 100 feet. The single-line grout curtain beneath the dike axes is about 18 miles long.
The reservoir area is underlain by Ordovician and Silurian dolomites with a scattered cover of tills and glaciolacustrine silts. There are many sinkholes in the dolomites.
The distribution of joints and joint fillings in the different lithological units were mapped and statistically analyzed. A quantitative ground-water flow technique was devised using the natural vertical water velocity profiles in uncased NX-sized drill holes.
The exploration and research program described was an essential part of the design phase for the grout curtain. Since completion, continuous observations have demonstrated the evolution of the induced ground-water regimen, confirmed the effectiveness of the control measures (grout curtain and pressure relief holes), and provided data for the development and further testing of the analytical procedures for ground-water flow analysis.
Figures & Tables
Engineering Geology Case Histories Number 6
This is the sixth volume in the Case History series of the Division on Engineering Geology of the Geological Society of America, initiated in 1957. Each succeeding volume has enjoyed increasing acceptance as an aid to the practicing geologist and engineer, student, and teacher, alike. This volume is a collection of general case histories on dams, tunnels, highways, and underground construction. Indeed, the Baldwin Hills reservoir failure is another in a long list of cases which demonstrate why the geologic environment, features, and circumstances are of major concern to engineering works.