The inclusion of an internal drainage system was considered innovative at the period. Near vertical tubular 8 in (200 mm) cut-off drains were provided at five-foot (1.52 m) intervals along the dam to relieve internal seepage through the concrete. While state of the art materials-handling methods were used, in some instances labour-saving machinery worked beside operations intended to maximise the labour content. Sustenance workers were employed chiefly for on-site preparation, road construction, foundation excavation, clearing timber from the reservoir basin, and on some concreting operations. Skilled workers were required on the dam for fixing the formwork where the concrete was poured. These workers were probably employed at normal day labour rates, the main employment method used on the project. Bulk handling of cement was also used for the first time in Australia, this saw a significant saving as opposed to bagged cement which was the standard practice of the day. Generally construction work proceeded smoothly and from an engineering point of view there were few setbacks. However, one did occur in the early stages of construction. In March 1934 there was a violent storm bringing of rain in less than two days. As a result, the river rose rapidly which flooded the dam foundation workings. Pumps had to be installed and work resumed three days later. The dam was completed in September 1940. When built it was the longest concrete gravity dam in Australia, and also the second highest after the Burrinjuck Dam in New South Wales. As of 1997 of the 90 large concrete and masonry gravity dams in Australia the Canning Dam is still the fifth highest and the sixth longest. It is the largest concrete dam in Western Australia in terms of length of crest and volume of concrete. The final cost of the dam was significantly less than had been originally budgeted for, and the work was completed on schedule to a date that was calculated seven years previously. Recently the Canning Dam has been subjected to considerable cracking of the upper parts of the dam and upper gallery. Investigations have shown that cracking was due to strong AAR (alkali aggregate reactivity) in the concrete. AAR results in swelling of the concrete, which may cause secondary compressive stresses, localised map cracks, and, ultimately structural cracks. In addition, the concrete tensile strength and elasticity significantly decreases. Many old concrete dams are known to suffer from AAR, including Fontana Dam in Tennessee and Pian Telessio dam in Italy among others. Extensive remedial works were undertaken between 1999 and 2001 to strengthen the dam wall.