Landslides a Deadly Threat to a Growing Community
The following is an introduction to a series of articles on landslides of the past, and the potential for future landslides in Columbia County.
During research on the 1915 Knickerbocker Cement Plant landslide that killed five men and injured seven others, it was learned that additional landslides occurred in the Claverack-Greenport area during the following 10 years.
Investigation uncovered more landslides in Stockport, and an ongoing problem in road maintenance due to slippage throughout the western part of the county.
The geological reports on the Knickerbocker and other slides blamed clay, not quicksand or erosion. The clay was described as yellow and blue, and it had reached a semi-fluid point where it squeezed out of the surrounding strata and precipitated the slide.
A trip to the New York State Museum and a conference with Robert Fickies, associate engineering geologist with the New York State Geological Survey, and an expert on geological hazards, revealed a potential for disaster still exists in Columbia County and surrounding areas.
Readers connect the California coast with mud slides, not realizing that the Hudson Valley is also prone to slides, only one of two such areas in the state, and one of the very few in the northeast.
The problem here is not mud, but clay, deposited when the last glacier (Wisconsin) was melting and receding.
A lake, or series of lakes, extended from Rhinebeck to Glens Falls, and on the east from the area near the Columbia County airport westward to the cliffs of the Heldebergs. The lake is called Lake Albany, and the clay, deposited in beds sometimes hundreds of feet deep, is known as Lake Albany clay.
It was this clay, known then as blue clay, that was used for making bricks in the brickyards along the Hudson River. This clay also was utilized in cement production.
The danger lies on the slopes of hills composed of Lake Albany clay. Most are "marginally stable" in their natural state, though they are moving imperceptibly.
However, when the clay is infiltrated with water, it becomes slippery. The soil on top is floating on a sea of quivering ooze. At that point, a landslide can occur spontaneously, as happened in the Episcopal Church cemetery in Stockport in 1908.
Thousands of small slides occur each year, usually not noticed because they happen in woods or in uninhabited areas. In many cases, these slopes find their own gravity, and simply change shape.
The focus of the articles to follow is what happens when man changes the natural equilibrium of these slopes. The Albany-Troy area is a perfect example of disaster in the making since houses began sliding down State Street in the city's early history.
Lake Albany was at its widest in this region, and both cities are built on deep deposits of clay--as is the city of Hudson. In 1843, 15 people were killed in a major landslide in Troy, with whole blocks of houses wiped out after a January thaw.
More recently--1973--a Troy Hills apartment project had to be evacuated when the building was found to be slipping sideways after a landslide.
When the Empire State Plaza was built on what was know to be a landslide prone area in Albany, 20,000 steel piles were driven deep into the more stable ground to anchor the complex.
In 1982, a landslide in Elsmere threatened to break a 48-inch pipeline supplying water to Albany--an event that echoed a similar slide that came inches from destroying Hudson's water pipe 64 years ago.
Pressure to Build
There is pressure today to build on hills that offer views of the river or creek valleys. Where lake clay is present, additional weight should not be added to the hill, nor should it be excavated. Drainage should be rerouted to assure the slope does not become waterlogged.
Adding soil to extend a yard or lessen a slope will exacerbate the problem by placing more weight where ideally there should be none.
Mr. Fickies describes water saturated lake clay as resembling toothpaste. If a brick is placed on a tube of Crest, and the cap removed, the paste will flow out rapidly and the brick will sink. This analogy occurs in many lake clay landslides; in others the hillside simply flows to a lower position.
This series will begin . . . with an explanation of Lake Albany and the clays that take its name. Other articles will be about some Columbia County landslides.
The final article cannot rightly be under the heading of "Historic Columbia County." It will deal with today's problems with this clay, and the precautions, if any, that are being taken to assure that there is not a repeat, on any scale, of the 1915 Knickerbocker landslide.
That article will also feature a reproduction of the Columbia County section of a map entitled "Landslide Susceptibility Within the Lake Clays of the Hudson Valley, New York." It will illustrate where the beds are located, and where there is a potential for landslides.
Writing this story required the help and experience of a long list of knowledgeable people who had to deal with someone totally ignorant of every facet of geology, soil science, and engineering. It was a learning experience, and I now view the topography of the county with entirely new eyes.
The geologists of New York State who were barraged with questions at all hours were kind and patient, not only from a desire to assist, but also because they felt the public should be aware of the problems the lake clay can create.
Finally, I should apologize for the melodramatic title. To label the series "Problems with County Clay" would certainly not have attracted readers. As the series continues, and the properties of this clay are described, I hope the readers will find the sleeping dragon appropriate.
COPYRIGHT 1988 MARGARET SCHRAM