An employee was measuring the 4x4 posts of a staircase. The employee was squatting down on the sixth or seventh step from the bottom, with his back facing down the stairs, looking at the condition of the soil under the stairs. While he was doing so, the ball of his foot slipped off the leading edge of the step, causing him to lose his balance and fall backwards to the bottom of the staircase and onto the pavement. He landed on his left side, sustaining contusions to the left hip and left shoulder as well as a sprain to the lower back. He was hospitalized.