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For South Shore homeowners, unstable soil adds to challenge of rebuilding
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Photo credit: Newsday / Ed Betz | The house is first jacked up and placed on wooden supports called cribbages. Then, the helical piles, which are metal and have a corkscrew-like shape, are driven into the boggy soil beneath the home. (April 11, 2013)
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LI's 13 dead Many homeowners near bays and canals on the Sandy-ravaged South Shore face a challenge that architects, engineers and geologists say is a vital consideration for raising or replacing a home -- bog and fill that can undermine a structure's foundation.
From Atlantic Beach to Montauk, unstable material lurks beneath the surface.
Bog, a spongy type of soil resembling compost and sometimes called peat or muck, is a remnant of the glacial "outwash" thousands of years ago. It's not found in the middle of Long Island or on the North Shore. Summer bungalows built along the South Shore in the 1920s and 1930s, many of which became year-round residences, sometimes were built on bog, architects and local historians said.
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Fill is generally of more recent vintage, dredged up during construction of canals and used in housing developments often built on top of filled-in marshland, particularly since the 1950s.
"Always when you're near the water, to me that soil is in question and it needs to be tested," said James A. Prisco, a Garden City-based architect who is secretary of the Long Island chapter of the American Institute of Architects. "Most of the time there is unstable soil under the house."
Architect James Bouler, of the Islip-based firm Bouler Pfluger Architects PC, is working with scores of property owners to elevate Sandy-damaged homes. He worries that foundation-support problems posed by bog and fill may be lost on some homeowners and contractors who are raising houses.
"There's no doubt in my mind that there are people -- contractors and clients -- that are putting up [concrete] block on top of the existing foundation and setting the house back on it," he said.
Bouler said state code requires the bottom of the foundation footing to be 3 feet below grade, as the surface level is called, to prevent frozen water from affecting the foundation.
"Ever see a frost heave on a road, where the road freezes and you see these big bumps?" Bouler said. "It's the same thing [with a foundation], where water can freeze under the foundation and lift it. And then it thaws and goes down. . . . It can lift and thaw, lift and thaw, and eventually that's when you get some settlement," with foundation cracks that mean doors and windows do not open and close properly and flooring has dips.
Installing support system
The typical course of action is to erect a foundation that uses piles driven to precise bearing points below ground for more support, architects said. There are two main types: helical piles, which are metal and have a corkscrew-like configuration; or driven piles, also called timber piles, which are likened to telephone poles.
"The bog has a very low bearing capacity, so you have to have a much larger footing or a helical pile system under the foundation, which is what the house rests upon," Bouler said.
The experts cautioned that the existence of bog and fill is marked by inconsistency. Some locations in South Shore communities have it, and some don't.
A soil boring must first be conducted to establish what kind of material is under a house, soil scientists, engineers and architects said. Costs can range from $1,500 to $1,800, Prisco said.
Loretta Luning, president of Slacke Test Boring in Kings Park, said her firm has done soil borings in many South Shore communities and found unstable bog layers of varying depths -- some going 2 feet down and others extending as far as 12 feet below the surface.
"It's very prominent in the Babylon-through-Lindenhurst area, especially in the proximity of the canals," Luning said. "In some cases, when they built the canals, they dredged out and cut that [fill] out and threw it up on the land, compacted it, covered it with sand and built houses on it. And that's the problem.
"People down there are saying to me, 'My house has been here 40 years. Why all of a sudden do I now have to put in helical piles?' " she said. "The answer is the groundwater has increased so much and has become closer to grade than it was 40 to 50 years ago."
When bog or fill is a factor, the expense of home elevation increases.
Nick Hughes, co-owner of Hughes Brothers General Contracting in Northport, which specializes in installation of helical piles, said, "You wouldn't need piles if there was no bog. You would just need a standard footing on a foundation."
The piles must go through "the bog level, the organic level [and] any kind of fill material -- debris that's not suitable for bearing a new foundation on," he said. "We have to get down to undisturbed sand soil."
Costs of elevation
Elevation costs for a modestly sized home, of 1,200 to 1,500 square feet, probably would be "no less than $80,000," Hughes said. That price includes the lifting of the home, installing helical piles, installing a new foundation and a new floor, and setting the house down on the raised foundation.
On top of that is the cost of connecting electric, plumbing and sewer lines, as well as any renovation work needed inside the home, he and others said.
"I'm having helical piles put in because of the bog," said Bob Platin of Bayport. Hughes Brothers earlier this month installed the piles at his home, which took on 30 inches of water from Sandy's storm surge.
"It would be unwise to build a new foundation, an even heavier foundation," he said, because "bog is unstable." The total cost of lifting his house -- it will be 4 feet, 8 inches higher -- installing the piles, taking out the old foundation and putting in a new one, and other work will be about $110,000.
Timber piles are another option. But a house must be lifted and moved from its "footprint" so the piles can be driven in, and many South Shore lots don't have the space for such maneuvering, Bouler said. Installation of helical piles is done beneath a structure that has been raised and is resting on wooden supports called cribbages, without moving it elsewhere.
While those who live near the water have long been aware of flood-prone areas, Sandy's devastation laid bare the consequence of almost a century of development in the marshlands of Massapequa, Lindenhurst, Patchogue, Babylon, Mastic and other communities where bog and fill are found.
Caitlin Young, a doctoral candidate in geosciences at Stony Brook University, has studied the soil composition of Patchogue, Shirley and Mastic. Sediment core logs of those areas found peat and fill.
"The marshy wetland forms a layer of peat on the bottom, which is spongy. Above is cut and fill, which is a bit solid. Then you put a house on top of that, and therein lies the problem," Young said, noting settling issues that can occur from compromised foundations.
Bouler said the 1920s-era bungalows in Lindenhurst that he's seen didn't have deep foundations. "They simply dug a trench into the dirt and poured a footing," he said. "And what that means is that the bottom of the footing is only 8 inches below grade."
After World War II came housing developments built on former wetlands -- what former longtime Suffolk County planning director Lee Koppelman calls "fill-and-build policies" -- and construction of canals that offered the opportunity of waterfront homes featuring boat docks and piers.
"Dredging projects dumped the dredge spoils on the former swamp areas, land people got cheaply," said Koppelman, executive director of Stony Brook University's Center for Regional Policy Studies, who has chronicled the Island's development for more than five decades.
History of LI's development
He recalled homeowners in one Lindenhurst development calling the planning department in the 1960s to complain of grass sprouting through their foundations.
"The [marsh] grasses would pop their way right through concrete floors if there was any crack whatsoever," Koppelman said.
George Kirchmann, vice president of the Historical Society of the Massapequas, also remembered the area's booming development in the 1950s and 1960s.
"A lot of the area down there, especially six or seven blocks from the water, is fill. Dirt was dug out of the Great South Bay and put in the swampy area and let sit for a year." Kirchmann said houses were built on top of it.
"Nobody thought much about water damage in the future because it never happened before," he said. "Of course there weren't any houses down there [before the dredging], so it was a self-fulfilling prophecy."
Nicole P. Maher, senior coastal scientist with The Nature Conservancy of Long Island, said the Island lost more than one-third of its natural wetland acreage -- and possibly much more -- to development.
Wetlands have valuable functions, she pointed out: providing physical protection for the coastline from storms, protecting the quality of coastal waters by filtering out excess nutrients and contaminants, and helping sustain a "vibrant ecosystem."
"We used to think of wetlands as soggy, disease-ridden places of low value. That's why they were ditched and drained and filled in, so we could develop on top of them," she wrote in an email. "Now we know better."