Abstract: At 1:12 p.m. on September 4, 2018, an employee was working at a vineyard. His employer was leasing the 0.9-hectare (2.3-acre) property from a private citizen to grow grapes for wine production. The employee was working as the field manager. He was onsite with a coworker, who was an intern. They were there to do ground maintenance. The employer had instructed the employee to trim branches from some of the oak trees around the perimeter of the property. The branches were obstructing the path of a tractor and blocking sunlight from the grapevines. The employee was working from an extension ladder. He was using a Stihl 021 chain saw to cut the branches. The intern was helping the employee by holding the ladder while the employee worked from it. They were at the edge of the southeast corner of the property. The employee leaned the extension ladder onto a limb of the oak tree. He had climbed about 3 meters (10 feet) up the ladder. Using the chain saw, he began to cut a 125-milllimeter (5-inch) diameter branch adjacent to the ladder. Before he had finished cutting through the branch, the branch broke. It swung downwards, but it remained hanging. The employee went for a second cut. At that point, the branch fell. It hit the ladder and knocked the employee from the ladder. The employee fell approximately 3 meters (10 feet) to the ground. The employee suffered several fractured several disks in his lower spine. He had to have back surgery. He was hospitalized for six consecutive days. The Napa Fire Department reported the incident at approximately 3:00 p.m. that same day. The employer did not report the incident, thus not complying with the reporting requirements. On September 7, 2018, a compliance and safety officer arrived at the site of the incident. Based on the facts gathered during the investigation and from the observations mentioned above, the employer was issued the following citations: Regulatory citation for Title 8 CCR Section 342(a) for failure to report in a timely manner the serious injury suffered by the employee. General citation for Title 8 CCR Section 3421(c) referencing 3203(a)(4) for failure to train and instruct employees about the hazards associated with operating the chain saw. Serious Accident Related citation for T8 CCR Section 3425(a)(1) for failure to ensure that the chain saw was operated in accordance with the manufacturer's instructions.