Dam Inspection
Toogood Pond, City of Markham, Ontario
This project involved the detailed condition assessment of the reinforcing steel in the main piers of the Toogood Pond Dam, in Markham, Ontario. The dam was built in 1960 and consists of a concrete spillway structure bordered by earth embankment dams on both sides. The spillway structure is approximately 23 m long and 6 m high, and includes five stop log bays for regulating the water flow. The walkway over the structure is supported by the end walls and four reinforced concrete piers built on top of the spillway slab.
The main aim of this project was to assess the condition of the embedded steel reinforcement, which is prone to electrochemical corrosion due to the corrosive and wet environment. The inspected areas included both sides of each of the four supporting piers on the downstream side, as well as each of the end walls.
The spillway structure of the Toogood Pond Dam in Markham, Ontario.
The corrosion of the steel reinforcement was assessed using InspecTerra’s proprietary iCAMM inspection technology. This method is a good alternative to the half-cell potential test. The half-cell test could not be used at this structure, because it requires drilling through the concrete to establish direct contact with the reinforcing steel, which would put the structure in a vulnerable position. In addition, the presence of significant humidity and moisture in the structure would render the half-cell test results highly unreliable.
For a general overview of the corrosion conditions of each of the areas, the inspections focused on the lower half of each of the walls. These areas are subject to higher environmental impacts due to moisture and water flow, and therefore are expected to have higher amounts of degradation. The inspection of all ten walls was conducted in approximately 4 hours by a two person inspection crew.
Scanning the condition of the steel reinforcement embedded in the main piers using the iCAMM tool.
The iCAMM results were used to quantify the cross-sectional loss of the steel reinforcement in each of the inspected areas. The results were well correlated with visible signs of corrosion on the concrete surface, such as cracking, scaling, disintegration, discoloration, pop-outs, and spalling, however, slight discrepancies were also encountered as expected, since the presence (or the absence) of exterior signs on the concrete surface cannot always be considered a true representation of the actual condition of the embedded steel reinforcement.
Picture of one of the inspected wall sections and the contour plot of the reinforcement cross-sectional loss based on the iCAMM inspection results.
This application demonstrated some of the key advantages of the iCAMM technology, which allows quantitative results to be obtained quickly and effectively without the need for any surface preparation or direct access to the embedded reinforcement, and under adverse environmental conditions (e.g., high humidity and moisture, high (or low) temperature, presence of salt/chlorides, etc.).
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