In July 1927, Stephen T. Mather, Director of the National Park Service, met with District Engineer Bonner of the National Forest service to discuss the proposed plan to upgrade the Wawona Road. Mather told the Forest Service representative that the Park Service did not expect funding for the road reconstruction project for another four or five years, but agreed the road needed work, and said it would be desirable to spend $50,000 on maintenance for and minor improvements to the present road. One thousand feet of the road was widened to 18' in October, and 11 culverts, ranging from 18" to 24" in diameter, were installed.63
Mather announced the plans to upgrade the Wawona Road early in 1928. He stated that the project would make the Mariposa Big Tree Grove accessible year-round, and would also help promote additional winter sports and camping in areas away from the congested Valley floor. The new roadway was originally planned to enter from the south along Big Creek, bypassing Wawona. However, the owners of the Wawona Hotel objected, stating that the proposed bypass would decimate their business, and offered a 100'-foot right-of-way across their property. Although engineers had determined that the Big Creek route would have an easier grade and would cost less to construct, the Park Service agreed to Wawona route.64
Engineer Henry S. Tolen of the BPR's San Francisco was sent to Yosemite to survey a new right-of-way. Tolen reported that the steep grades from Grouse Creek up to Inspiration Point and back down to the Valley were too steep for traffic requirements. He recommended that a lower route be established by constructing a new road along the bluffs below Turtleback Dome.65
The National Park Service and the Bureau of Public Roads conducted two years of intensive studies concerning the effect the new road would have on the park landscape. The final survey set the route with a maximum grade of 6 percent for lengths not exceeding 2,000', and maximum radii of 200' for open curves and 300' for blind curves. Park Superintendent Charles Goff Thomson determined that the preliminary road realignment design and some proposed alternatives were unacceptable. He claimed "A road benched out of the palisades would have produced an irremediable scar, ruinous to the landscape. An underpass in the region of Bridalveil Fall was studied but finally rejected. And a zig-zag road would have been unsafe for modern traffic and would have made an appalling disfigurement." The plan finally adopted called for a new highway tunnel to be bored through the mountainside below Inspiration Point. By keeping the road's location high, 1,800' of the scarring on Turtleback Dome was eliminated, and the road's distance was reduced by .77 mile from the original survey. The road was designed around the 18' wide Forest Highway Standard. This decision was reached with the consensus of Park Service management, leading landscape architects, and the National Park Service Board of Expert Advisors for Yosemite National Park, composed of Dr. John B. Buwalda, Duncan McDuffie and Frederick Law Olmsted, Jr.66
The chosen tunnel route initially met with opposition. National Park Service Chief Engineer Frank A. Kittredge pushed for a route up Grouse Creek and over Turtleback Dome, hoping to save Inspiration Point as a roadside feature. Park service Assistant Director Horace Albright also favored the higher route because of Inspiration Point,67 but the BPR route was ultimately accepted.
In May 1928, four miles of the new route between Alder Creek and Camp Hoyle (the Civilian Conservation corps Camp near Wawona) had been surveyed, and a preliminary line had been run as far as Chinquapin. By the end of July, the line had been extended as far north as Avalanche Creek. The roadway was to closely follow the old road from a point north of Alder Creek as far as Bishop
