Tag Archives: foundations

Keeping Boston buildings secured on wood pilings, fill

Posted on by

Parts of Boston rest on wood pilings on fill that reclaimed land from waterways. This has led to a lot of repairs:

Much of modern-day Boston was underwater when European settlers first arrived on the Shawmut Peninsula. From the late-1700s to the late-1800s, the city aggressively expanded, filling parts of Massachusetts Bay with soil, sand and gravel. Today, the city has about 5,250 acres of filled land, said Mr. Simonelli.

To build on the unstable surface, builders drove tree trunks into the fill until they hit firmer ground, then placed foundation stones on top of these wooden piles. This technique was used until the 1920s, when foundation-building technology changed, Mr. Simonelli said.

Wooden piles can remain intact for hundreds of years if covered by groundwater, as they were when first installed. As the city grew, construction of tunnels, sewers, basements and subways caused the groundwater level to drop in many areas, which exposed the tops of the pilings. Air causes the wood to rot, said Giuliana Zelada-Tumialan of the engineering firm Simpson Gumpertz & Heger. As the rotted wood crumbles, the foundation stones sink, and so do the structures they support…

Repair means an expensive process called “underpinning”—cutting off the rotten wood at the top of the piles and replacing it with steel. It usually involves hand-digging a series of pits in the basement floor, a laborious process that can cost more than $200,000, and another $100,000 to repair the brick damaged by settling, said Mr. Kempel of Pegasus Luxury Homes, who has bought, renovated and sold a number of Boston houses. That cost doesn’t include any repairs or renovations that would be required if that basement unit was living space, as many are in row houses.

This is a hidden dimension of many urban buildings. What exactly do they stand on? How solid is the land underneath large structures? What happens if the foundations underneath are threatened? I remember looking as a kid at diagrams of what was underground in New York City or Chicago and wondering how it all worked with subways, gas, water, and electric lines, and other items.

The focus of this article is on pretty expensive real estate in Boston, particularly residences. With this kind of money involved, property owners – who the article notes may not even know about the potential problems and/or bypass inspections – can afford to fix their foundations. What happens when this affects public buildings or property owners with fewer resources? Perhaps this has to do with the value of fill land; given its proximity to the water and the city center, such land might be more valuable on the whole across cities. But, I could also imagine where a sizable city would have to put together a significant effort to help out a range of property owners.

 

Building large buildings over the Hudson Yards in Brooklyn

Posted on by

How are large skyscrapers and buildings constructed on top of a railroad yard? See the example of Hudson Yards in Brooklyn:

Hudson Yards is the largest private development project in U.S. history, and it’s being built without footings or foundations. Instead, the project is going to sit atop 300 concrete-sleeved, steel caissons jammed deep into the underlying bedrock. Work on the platform broke ground last week, and will take roughly two and a half years to complete. In that time, there’s a lot of engineering to do.

Caissons are a technology borrowed from bridge building, and they are what makes this project possible. The engineers will drill them anywhere from 40 to 80 feet into the Manhattan schist (the dense, metamorphic bedrock that supports the city’s soaring skyline). The caissons are meticulously arranged in the narrow spaces between the tracks. Above, the they will connect to deep-girdle trusses – some up to 8 stories tall – that control and redirect the towering weight overhead. Finally, the slab. “The total punishment is somewhere in the neighborhood of 35,000 tons of steel and 50,000 cubic yards of concrete,” says Jim White, the lead platform engineer. And that’s before they start loading buildings on top.

Building an elevated platform over an active train yard requires clockwork scheduling. White used computer models to coordinate the tempo of his drilling and truss-laying around the rhythm of the rails. “We look at the area of the yard and model in the train traffic, when it moves on an hourly basis and actually design the connections so we can install these 100 foot long trusses when have a window of opportunity,” says White. For the two and a half years it will take to complete the platform, there are only four scheduled track closures.

That is quite a lot of weight over a rail yard. However, such projects are not unknown in large cities where people look to maximize both space above and below ground. Space is at a premium so construction projects need to get creative and allow for a multitude of uses.

A Harvard sociology class where students will distribute $100k in grant money

Posted on by

A Harvard sociology course with $100,000 in grant money to distribute sounds like a cross between the work of a typical intro-level social problems course and what foundations do:

While most Harvard College students focus on what they will take away from a course, students who enroll in Sociology 152: “Philanthropy and Public Problem-Solving” this spring will have the opportunity to give back­—in the form of $100,000 in grants to Boston-area non-profits of their choice.

Students enrolled in this new course will split into teams based on area of interest. Each team will conduct research on a particular social issue, ranging from homelessness to education reform, and will eventually choose a local organization to provide with a grant.

The Once Upon A Time Foundation, based in Fort Worth, Texas, has donated $100,000 for students enrolled in the course to distribute to non-profits. The foundation has funded similar courses at Stanford, Princeton, Yale, and various colleges in Texas.

Harvard Kennedy School Senior Lecturer Christine W. Letts and Senior Research Fellow James L. Bildner will co-teach the class, which will be open to both College and Kennedy School students. “It’s an exceptional opportunity,” Bildner said.

An opportunity indeed.

While this could be good practice, I wonder if students might reach another conclusion: handing out just $100,000 is not enough to tackle serious social problems. Even major money sources like the Bill & Melinda Gates Foundation can only do so much.