PRESS RELEASE – DR. Roosevelt Isaac of Strata Engineering Consultants Ltd of Saint Lucia was granted an award of ‘Engineering Excellence International’ by the Consulting Engineers of Alberta, Canada in association with Golder Associates Ltd for his contribution to the John Compton Dam Desilting Project.
His contribution to the project emphasised the sediment characteristics in the reservoir and the geotechnical hazard assessment of the 1.5 million cubic metres of sediment to be removed from the dam by suction dredging and hydraulic fill placement at the storage site.
The sediment characterization involved drilling into the reservoir basal sediments and recovering soil samples for laboratory testing to identify the physical and chemical characteristics of the sediment to facilitate suction dredging and deposition at the storage site.
The physical tests performed on the reservoir sediment included particle size analysis, specific gravity, bulk density, mineral composition, x-ray diffraction analysis and geotechnical parameters.
The chemical tests performed were to identify the presence of heavy metals that would potentially restrict dredging activities or re-use of the sediment.
The geohazards assessment at the dam site involved the study as a result of climate change of the potential for landslides, rockfalls, debris flow and reservoir shoreline erosion.
Recommendations for geohazards mitigation include detailed terrain stability mapping using LiDAR or InSAR; detailed analysis of geological materials (soil and rock); the incorporation of probabilistic relations into the geohazard rating system; detailed slope stability analysis to include the effect of recharged springs and aquifers during rainstorms; reforestation; the construction of sediment traps on reservoir tributaries and the installation of rip-rap armour protection in areas vulnerable to reservoir shoreline erosion.
Dr. Isaac practised geotechnical engineering for a period of 15 years in the province of Alberta, Canada, which included 10 years as a senior geotechnical engineer at Syncrude Canada Ltd Oilsands mine in Fort McMurray, where he was employed to assist in the design and construction monitoring of the world’s largest hydraulic fill dam which was approximately 90 metres in height and was built on very weak, sensitive clay foundation subsoils.
The dam was erected by hydraulically pumping 240,000 tons of slurried tailings (sediment) sand per day over 18 kilometers length of dam with a surface area of 22 square kilometres and the water drained and recycled back to the mine extraction plant for reuse.
A total of 550 million cubic metres of hydraulically placed mine tailings sand was used to erect the hydraulic fill dam to its ultimate height of 90 meters.