APA regulators receive grim report on landslide

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July 16, 2011

KIM SMITH DEDAM Press-Republican The Press Republican Sat Jul 16, 2011, 02:11 PM EDT

RAY BROOK — Data from the biggest landslide in state history reached Adirondack Park land-use regulators this week.

Adirondack Park Agency commissioners listened with concern as Dr. Andrew Kozlowski, a research geologist and director of Geological mapping for the New York State Museum, offered a grim report of an 82-acre landmass still very much in motion.

The Keene slide began sometime between May 4 and 6, Kozlowski said, due to excessive groundwater pressure from melting snow and heavy rain.

No final tally of costs related to the landslide has been made, because the event isn't over yet.

Kozlowski said there is property at the bottom and in the path of the "toe" of the slow-moving mass of earth.

Nobody has been injured, but four homes caught at the top, near or on tension cracks, have been impacted.

One is slowly being torn apart.

Another owned by the Marlatt family has been lifted by construction crews and rolled back from a 15-foot landslide drop that has grown in a month to 30 feet.

And two other houses are sitting on ground just yards from the "crown" or top scarp of the landslide.

The winding pathway of Adrian's Acres Lane winds up the mountain within a stone's throw just west of the slump.

The road give access to another 30 homes uphill and, so far, beyond the plane of moving earth.

FUNNELS

Data shows the Keene landslide has slowed down somewhat as rain has ceased in recent days, Kozlowski said.

But he said the forest soils are now littered with "thousands and thousands" of tension cracks wide, open gashes in the forest floor that act like funnels, allowing any amount of rain direct access to the bottom layers to lubricate hundreds of millions of tons of shifting earth.

Kozlowski said they heard water burbling at the toe end of the landslide.

And, he said, if you stood there long enough, you could see it move.

"It's not going to run over you," he said, "but it is 82-acres of earth moving down a slope. The forces we are talking about are immense."

'Far from equilibrium'

The toe of the landslide, which is shaped something like the scalloped edge of a scarf draped over one shoulder of Little Porter Mountain, has moved about 15 to 20 feet since it started, Kozlowski told APA.

The Keene Valley landslide is "far from equilibrium," the scientist said.

It has moved from 2-inches to as much as 2-feet a day over the past two months.

Data suggests the event would continue and "is possibly expanding," given thousands of gaping tension cracks.

"It's a ground system that has now opened up," Kozlowski said, calling it "certain and a fact" that the landslide will accelerate.

The slide is already impacting one home at the bottom and is in a tug-of-war with one utility pole.

Ongoing research and monitoring stations revealed some geological surprises.

But Kozlowski said existing data is too incomplete to offer any planning guidance.

"Existing geological maps are inadequate to evaluate landslide hazards in the region."

But some ancillary information is coming.

Test holes around the Keene Valley landslide found lake-clays and sandy soils some 200 to 300 feet higher up the mountain slopes than expected, deposited there thousands of years ago by the ancient retreat of glaciers.

APA Commissioner Cecil Wray owns a home in the ridgeline confines of Adrian's Acres.

He asked Kozlowski if there are any lessons to be learned "for those of us who live on (the hills) of Keene Valley?

Kozlowski said Light Detection And Ranging (LiDAR) contour mapping would provide detailed images showing potential problem areas, noting that Adrian's Acres is a "reactivated" landslide that could have been spotted with LiDAR data and a trained geologic eye.

"It says we really have to do some better mapping in the Adirondack Park," APA Chairman Curt Stiles said.

Email Kim Smith Dedam at: kdedam@pressrepublican.com