Nestled between the foothills of the Cascade Mountain range and the Puget Sound lies Lake Washington, a lake that contains an extraordinary history. Many call the shores of Lake Washington home. Residences include many prominent citizens, major industries, and until recently, the U.S. Navy. Three major floating bridges cross the Lake. One is State Route 520 and the other two comprise the western end of Interstate 90. Prior to bridge construction Lake Washington had it’s own ferry system.

Lake Washington is the largest lake in western Washington. The lake is approximately 20 miles long encompassing 71.5 miles of shoreline and 28 square miles of land.  In the center of the lake is a large island known as Mercer Island. I-90 travels across the island connecting Seattle with the eastside communities of Bellevue, and Issaquah.  The average depth of the lake is 110 feet and it’s deepest spot, northwest of Mercer Island, is about 220 feet deep. Since the lake surface is about 21 feet above mean sea level, its deepest point is nearly 200 feet below sea level.

The southern end of the lake is home to the Boeing Corporation’s Renton commercial aircraft plant where all Boeing 737’s, and 757’s are assembled. The Cedar River, one of two main tributaries, flows past the plant and enters the lake. The other tributary, known as the Sammamish Slew enters the lake at the northern end. The U.S. Navy made it’s home on the northwestern shores in an area known as Sand Point.

Over the years many unfortunate accidents have occurred on the lake. The remains of these accidents and the stories they tell are contained within the lake’s depth. Arguably the most remembered accident on the lake was the sinking of the old I-90 bridge. In 1990 the bridge was undergoing reconstruction and was scheduled to reopen servicing the eastbound lanes of I-90. In November of that year a fierce storm blew in and ravaged the bridge. Waves crashed over the bridge deck filling pontoon structures that provided flotation. Within hours the bridge, which was a floating structure, began to sink. Section after section gave way and fell to the bottom of the lake approximately 300 feet below. The bridge was eventually replaced with a new floating bridge.

The Department of Transportation is not the only agency to sustain losses in Lake Washington. The U.S. Navy has had its share of aviation mishaps. When you dive underwater you expect to find sunken ships, old bottles and coins, but nothing can prepare you for a fully armed PB4Y-2, a four engine bomber larger than a B-17, resting upright on its landing gear.

The World War II Navy aircraft may be one of the more dramatic things in the lake, but there are many others. In 1991 UAS completed the first comprehensive survey of the lake bottom. UAS used side-scanning sonar to locate at least seven military aircraft including a huge martin Mariner PMB flying boat, more than one hundred sunken boats and ships, a train, several sunken forests, the pontoons of the old I-90 bridge.

These images and links are of four Navy wrecks currently held within the lake’s depth. In addition one potentially civilian aircraft was recovered by UAS.

Lake Washington, History and Mystery

For thousands of years, prior to the turn of the century, Native Americans inhabited the shores of Lake Washington. They called it ha’cuy’lake and the people who lived in the eighteen house sites scattered along its shore were called hachua’bsh, the ‘lake people’. They caught fish from the lake and nearby streams. They hunted vast numbers of waterfowl in the extensive marshes along the shore as well as muskrats, otter, raccoons, deer and elk.

The lake would seem to have been a perfect Eden for these people, but in their folklore it has an otherworldly, even frightening character. Legends identify places along the shore haunted by dangerous supernatural beings: monsters that sucked swimmers to their doom, huge spotted serpents with horns on their head that caused terrible landslides, and a race of dwarfs who drove people insane. One told of a man who tried to capture an elk in the lake and got his shirt caught in its antlers. Both disappeared underwater, and some time later their bodies appeared in Puget Sound near Richmond Beach. Some sort of mysterious, subterranean channel connecting the lake with the Sound seemed to have swallowed them. Another legend claimed the lake itself swallowed Mercer Island every night and disgorged it every morning.

This perception reflected the peoples’ long relationship with the lake, and its own dramatic history. Clearly, the lake was a mysterious place whose depths held powerful secrets. Some of these revealed themselves when the Europeans settled the land and began to change its character.

When workers completed the Lake Washington Ship Canal, connecting the lake with Lake Union and Puget Sound in 1916, the lake’s level was lowered about nine feet to match that of Lake Union. The exposure of the lake’s near shore shallows wiped out most of the salmon spawning beds and killed the wapato plants harvested but the Native Americans. The Black River, which was then the outlet for the lake, was also destroyed. The Black River flowed from the south end of the lake into the Duwamish River and Elliott Bay.

The newly exposed lakeshore revealed a number of interesting things. In Union bay, the wooden stumps of an ancient fish trap poked above the mud. At the mouth of the May Creak, near Kennydale, the remains of campfire circles indicated the lakeshore had been even lower in the past. Even more interesting and mysterious were the forests of drowned trees that surfaced at several places along the lakeshore.

The bark, still attached to the snags and well preserved, identified most as Douglas Fir. An old legend told of a man who went to the southern end of Mercer Island to strip bark off the drowned trees. Dried, this made excellent fuel for his house fire. But he began to experience strange, unpleasant sensations. These, others claimed, were produced by supernatural dwarfs inhabiting the tree trunks. The dwarfs resented the man stripping off the bark as much as a person who would have his clothes taken away.

The snags hiding just beneath the surface of the water or rising above presented a navigational hazard. In 1919 workers removed nearly 200 of them or dynamited their tops to within 30 feet of the surface. The remaining trees stood upright in 60 to 120 feet of water. Huge landslides seem to be the likeliest way these forests ended up in the lake.

Geologists had concluded that an enormous ice sheet gouged out the lake basic during the ice age. They speculated that the lake had once been an arm of Puget Sound. Duwamish Indian legend recalled a time when the lake contained salt water. In the late 1950s core samples taken from bottom sediment confirmed the legend. For a brief period, thirteen to fourteen thousand years ago, the sea had invaded the lake basin. The delta building from the ancestral Cedar River soon pinched the arm from the Sound and melt water from the ice sheet and from other streams created a deep freshwater lake. The lake was already mature when the eruption that produced Oregon’s Crater Lake left a telltale layer of ash on the bottom about 6,800 years ago.

The lake bottom has a ‘W’ shaped profile, with steep sides plunging to a floor which gently rises in the center due to the movement of silt by seasonal convection currents. Near shore, a wave cut terrace rings the lake 40 feet below its present surface, evidence of earlier water levels. As the Cedar River delta grew it dammed more water in the lake basin raising its level.

Lake Washington’s bottom sediments and the objects resting in them provide a detailed history. Carbon 14 measurements of the submerged trees indicate that a number of events occurred around 3,000, 2,500, 1,700, and 1,100 years ago. The latest group of trees helped date an earthquake believed to have occurred along a break in the North American Plate called the Seattle Fault. Scientists believe that an earthquake along this fault, which runs roughly east to west from the Kitsap Peninsula through Seattle’s business district, beneath the lake bottom, and out past the Sammamish plateau, lifted the southern portion of the fault. Restoration Point, at the southeastern end of Bainbridge Island, was raised as much as 20 feet and Alki Point in Seattle rose 13 feet.

The earthquake, estimated at 7 to 7.5 on the Richter Scale, caused rockslides in the Olympic Mountains, and sent several forests-covered sections of Lake Washington’s shoreline into the lake. Two of these slides produced the sunken forests on the west and southeast sides of Mercer Island. The third was on the northeast shore of the lake at O. O. Denny Park. An analysis of sunken forests from Mercer Island indicated they died sometime in the fall, winter, or spring between the years 894 and 997 AD.

These landslides were catastrophic events. Sections of Mercer Island more than 150 feet high collapsed, traveling nearly a quarter mile before coming to rest deep in the lake. Their plunge sent huge waves sweeping across the lake’s surface and slamming into the shore, probably devastating native villages. Little wonder they regarded the southern end of Mercer Island with dread.

Dates from other trees in the lake suggest massive landslides occurred earlier, and other evidence suggests one happened as recently as 300 years ago. These disasters and a relentlessly rising lake level must have contributed to the Indian’s ambivalent feelings towards the lake; feeling that are preserved in their folklore. Scientific data also suggests that similar disasters are likely to occur in the future.

The history of Lake Washington is often shaped by natural disasters but human tragedy also shapes the lake. Contained in the lake are bits of history known only to a few adventurous explorers. Aided with high-tech equipment UAS has located a train of coal cars lost to the lake in 1875.

The train belonged to the Seattle Coal & Transportation Company, one of the early local business enterprises that succeeded in putting Seattle and the eastside on the map. In the fall of 1863, surveyor Edwin Richardson discovered coal beside a stream later named Coal Creek. Wagons hauled sacks of coal down to the lake where it was transported to the west shore by sail boat, rowboat, or Indian canoe. Six weeks later, prospectors discovered a richer coal seam south of the Creek at a place called Newcastle, named after the famous English mining town. To bring the coal form Newcastle to Seattle, the company constructed a cumbersome system of tramways and barges to haul trains of iron-wheeled wooden cars. Each cart was capable of carrying two tons of coal from the mines to bunkers on the Seattle waterfront. In January 1875, the sternwheeler Chehalis was rounding the northwest point of Mercer Island when a gale blowing from the south tipped the barge it was towing and sent 18 cars plunging into the lake. They remain where they sank, well preserved in 200 feet of water, many of them upright and still carrying their cargoes of coal.

UAS has taken the lead in crafting laws to preserve the state’s underwater archaeological resources in an effort to prevent these and other wrecks from becoming vandalized and to ensure proper conservation and restoration. Hopefully, one day the train may be on display in Renton and some of the aircraft will find shelter in the Museum of Flight. Lake Washington has always been a valued for its beauty and as a natural resource. We are now coming to understand its value as a historical resource.