A SEEMINGLY simple kid’s prank of throwing rocks and other material down a storm drain resulted in a major emergency repair job to prevent the collapse of a 42-in. sanitary sewer main in Spokane, Washington.
In a short period of time, a group of kids completely blocked an 18-in. pipe leading to the city’s combined sanitary/ storm drain system. The drain soon began to overflow, sending water streaming down the 800-ft, 33° west facing slope of Spokane’s Latah Creek. Within a few short hours, the rushing water cut a large eroding trench 12 to 15 ft wide and deep at the top of the slope, and 3 ft wide by 6 to 8 ft deep at the bottom.