The Marin County Canal
by Robert L. Harrison
In the 1890s the economic value of canals was universally recognized. The Suez Canal had been opened a few years earlier and its impact on the wealth of Europeans was well documented. The French were building a canal across Panama and a Nicaraguan canal was under discussion in the Congress. Locally, at a much smaller scale, improvements to the San Rafael Canal were underway to maintain water borne commerce inland as far as Irwin Street.
A canal was also being discussed for southern Marin County. As headlined in the Sausalito News of August 24, 1895, “Adjunct to the ‘Canal Nicaragua’ Offered”. The project’s ambitious goal was to provide a second opening from the Pacific Ocean to San Francisco Bay. The Golden Gate was thought by some to be dangerous as it was subject to strong currents and required crossing of the treacherous “Potato Patch” shoal. Elk Valley, later known as Tennessee Valley, just north of Golden Gate, had the potential to be a safer second opening to the Bay.
The hazards encountered at the Golden Gate were dramatized by a wreck involving the S. S. Tennessee. On a foggy March night in 1853 the ship attempting to enter the Bay was swept by a strong current past the Golden Gate. Around nine p.m. a passenger standing on the bow spotted breakers and shouted a warning to the wheelhouse. The warning came too late. The ship struck the rocks at Indian Cove. The Captain successfully beached the ship enabling the First Mate to wade ashore to rig a cable line. During the night all 551 passengers and 14 chests of gold were safely brought to shore by cable or quarter boat. Not a single life was lost. By noon the next day the S. S. Tennessee broke up and sunk.
The valley and cove were renamed in memory of the S. S. Tennessee. The Tennessee Valley cuts through the hills of the Marin Peninsula about three miles north of the Golden Gate. The nearly three mile long valley rises on a gentle slope to just under 200 feet at the summit. The construction of a canal through to the ocean was reported in the August 24, 1895 Sausalito News as, “…presenting no engineering difficulties [and] could be compassed with comparatively small expense”.
The Marin County Ship Canal was discussed in a meeting between County officials and the Army Corps of Engineers in 1936. In its January 17th edition the Sausalito News described it this way, “And, there was revived the plan studied twenty-five years or so ago to cut a ship canal through a gap in the hills to the Pacific Ocean at Tennessee Cove, a scheme that sounds almost fantastic at first blush but which, upon careful study, appears quite feasible…” The canal fit well into the County’s desire to dredge Richardson Bay and develop its Sausalito shore for industrial use. The president of the Marin County Planning Commission spoke of “…the need for utilizing this otherwise worthless body of water.”
While the Tennessee Valley offers a relatively uncomplicated route for a canal between the ocean and the bay, it is worthwhile to consider the scale of the undertaking from a preliminary engineering viewpoint. Assuming the canal was at sea level and served ocean going traffic, to be functional its dimensions would need to be comparable to the first Panama Canal: 110 feet wide by 40 feet deep. Built at sea level no locks would be required.
To construct such a canal, excluding dredging its approaches in the ocean or bay, would require about 13 million cubic yards of excavation as well as a plausible plan to dispose of the material. To put this enterprise in perspective, in 1936 constructing the four-lane 3.4 mile long Waldo Grade required 1.8 million cubic yards of excavation. This was the largest earth moving project completed by the California Highway Department up to that time. The highway builders used most of the excavated material as embankment elsewhere on the project site. For the canal most of the material would require disposal at another location, probably in the ocean.
The Marin County Canal would also require a high level multi-lane bridge to carry Highways 1 and 101 over ocean going vessels. The cost of the canal and bridge plus the cost of dredging the Richardson Bay and ocean approaches to a depth of 40 feet for a distance of about two miles would likely bring the 2018 project cost into the billion dollar neighborhood. It would not be the “feasible” project envisioned at the 1936 meeting described above. Despite the realities of this project, the Sausalito News on January 27, 1944 reported Marin County organized labor in its post-war employment program included, “Construction of a sea level canal through Tennessee Valley to the ocean, thereby creating two entrances to the bay.”
Today the Tennessee Valley, now part of the Golden Gate National Recreation Area, is highly regarded for its beautiful scenery and as an ideal place for invigorating hikes. Beyond the hikers, the only other entity that passes through the valley is the summer fog that finds its way inland through the low lying break in the range of coastal hills.
Originally published at https://annetkent.kontribune.com.