The Monument Hill Road Boat Ramp in Oroville, California is a concrete ramp that provides access to the Thermalito Afterbay, which is a large reservoir located on the Feather River. The ramp is approximately 18 feet wide and has a gentle slope, making it suitable for a variety of watercraft.

According to the latest information available, the Thermalito Afterbay is open to motorized boats, including fishing boats, ski boats, and personal watercraft. However, there are restrictions on the use of certain types of boats, such as airboats and jet boats, due to safety concerns.

It should be noted that access to the Monument Hill Road Boat Ramp and the Thermalito Afterbay may be subject to change due to seasonal changes, maintenance, or other factors. Therefore, it is recommended to check with local authorities or consult the latest information available before using this boat ramp.