ANCHORAGE, Alaska (AP) — Poor risk assessment and management were among factors that led to the grounding of a Shell oil drilling rig in the Gulf of Alaska in 2012, the Coast Guard said in a report released Thursday.

The report also says Alaska’s tax laws influenced the decision to tow the Kulluk to Seattle for maintenance. Royal Dutch Shell PLC believed the drill vessel would have qualified as taxable property on Jan. 1, 2013, if it was still in Alaska waters.