 After plant explosions killed one employee each in 1835, 1847, 1849, 1850, and 1851, a major explosion on 12 October 1855 killed seven employees, including Whipple's brother and son, injured five more and destroyed a canal boat and parts of the mill.Manufacture of gunpowder in response to orders avoided the hazard of storing powder inventories until orders were received, but required water power on demand.The canal lock system controlled outflow from Sebago Lake; and, as a shipper interested in the well-being of its customer, canal management was receptive to regulating water releases to meet needs of the powder mill.