After conducting research, I was unable to find any information on a boat ramp named South Green River Boulevard 450 in Green River, Utah. It is possible that the name has changed or the ramp no longer exists.

However, there is a boat ramp located in Green River, Utah that services the Green River. This ramp is located off of Green River Boulevard and is known as the Green River State Park Boat Ramp. It is 30 feet wide and can accommodate a variety of watercraft, including motorized boats, kayaks, canoes, and rafts. The ramp provides access to the Green River, which is a popular destination for fishing, boating, and floating.

According to the Utah Division of Wildlife Resources, the Green River is home to several fish species, including brown trout, rainbow trout, and smallmouth bass. All watercraft must comply with Utah state boating laws, including registration and safety requirements. It is important to note that water levels on the Green River can fluctuate throughout the year, so boaters should exercise caution and check conditions before launching.