An employee was working in a wastewater facility, cleaning a metal screen. He positioned it against a railing on top of a metal grating, which was above a headworks bypass channel. When he stepped onto a trapezoid-shaped section of grating, it slid forward and tipped into the channel. The employee fell about 5 feet into the channel, which contained about 1 foot of stagnant wastewater. He suffered a rotator cuff and ligament tear in his left shoulder, a contusion on the left side of his back, a broken left-side rib, and a tear of the medial collateral ligament in his right knee.