In any crossing of the Suez Canal by Egyptian forces, success was highly dependent on the performance of the Egyptian Corps of Engineers, which had several daunting tasks to accomplish. Israeli engineers had constructed a massive artificial sand barrier spanning of the canal's east bank (except for the Great Bitter Lake, where the width of the canal made a crossing unlikely). To prevent erosion, the sand barrier was supported by concrete, which was one metre (3⅓ ft) above the water at high tide, and three metres (10 ft) above water at low tide. The canal was wide and approximately deep. Engineers had to clear seventy passages through this sand wall, each seven metres (23 ft) wide. This meant the removal of of sand for each passage. Initially, conventional methods were tested for breaching the sand wall. It was found that, to clear a single passage required 60 men, 1 bulldozer, 600 lb of explosives and five to six hours, uninterrupted by enemy fire. Since the crossing sites would likely be congested and under enemy fire, these methods proved to be impractical and too costly.