Residents of the home in the 12300 block of Fifth Avenue Northeast went to bed Sept. 25, 2011 despite a faint smell of gas. When they began to turn lights and appliances on the next morning, their home exploded.
The blast was heard for miles and broke the windows out of nearby homes.
According to safety staff from the Washington Utilities and Transportation Commission, which monitors natural gas pipeline safety in the state, the events that caused the explosion started with a downed power line blocks away.
When the power line came down Sept. 25, it energized a metal fence post, which then energized an abandoned, buried metal water pipe, according to the report.
The electrical current then surged to the natural gas line, punching four finger-sized holes into it, according to the report.
Puget Sound Energy workers found and repaired three of the four leaks but missed the fourth.
According to the report, the leak likely filled the home's crawlspace with gas before exploding.
Washington Utilities and Transportation Commission safety staff are recommending penalties against Puget Sound Energy for violating gas safety rules by not surveying all the gas lines in the area for leaks.