The Wilderness Boundary to Forest Road 40N54 section of the Whitewater River in California is a beautiful and challenging run for experienced whitewater enthusiasts. The ideal streamflow range for this section is between 300 and 1,500 cubic feet per second (cfs). At lower flows, the river can be technical and rocky, while higher flows can create big waves and powerful currents.

The class rating for this section ranges from Class III to IV, with some challenging Class IV rapids and obstacles. The segment mileage is approximately 7.5 miles, starting at the wilderness boundary and ending at Forest Road 40N54.

One of the most notable rapids in this section is called "Deadman's Drop," which is a Class IV rapid with a steep drop and large waves. Other challenging rapids include "Sidewinders" and "Tunnel Chute."

There are specific regulations in place for this area, including a permit requirement for overnight stays in the wilderness and a limit of 15 people per group. Additionally, visitors are required to pack out all trash and leave no trace.

Overall, the Wilderness Boundary to Forest Road 40N54 section of the Whitewater River offers a thrilling whitewater experience for experienced paddlers with a range of challenging rapids and beautiful scenery. It is important to check current flow conditions and obtain necessary permits before embarking on this adventure.