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Silicon Valley's Latest Desperate Housing Idea: On A Landfill (siliconvalley.com)
An anonymous reader writes:
Silicon Valley real estate developers want to construct a $6.7 billion housing complex over a former landfill with 5.5 million tons of municipal waste from the last 25 years. "The regulators were pretty skeptical at the start, I have to say," one of the firm's partners told a local newspaper. Besides the 1,680 units of housing, there'd also be 700 hotel rooms, plus 5.7 million square feet of office space, and 1.1 million square feet for retail stores. The project "includes elaborate safety systems to block the escape of combustible methane gas and other dangerous vapors, and to prevent groundwater contamination," according to the Bay Area Newsgroup -- including one foot of solid concrete over 30 acres of landfill, with the housing built above the first-floor shops and parking structures "as a way of creating additional distance between residents and any escaped gases in the event of an emergency." In addition, there's alarms and sensors, "as well as another system to monitor, collect and dispose of gases underground."
Though the project has gained key approvals from the city of Santa Clara, it could still take two decades to complete. "Last year, the City of San Jose sued the City of Santa Clara, charging that the imbalance between the project's jobs and housing -- 23,000 jobs and 1,680 housing units -- will increase housing demand in San Jose and tax its overstretched services and infrastructure... but both sides said they hope for an out-of-court resolution."
Though the project has gained key approvals from the city of Santa Clara, it could still take two decades to complete. "Last year, the City of San Jose sued the City of Santa Clara, charging that the imbalance between the project's jobs and housing -- 23,000 jobs and 1,680 housing units -- will increase housing demand in San Jose and tax its overstretched services and infrastructure... but both sides said they hope for an out-of-court resolution."
Yes, yes it is MUCH different than what they built on in San Francisco. There are two different meanings of landfill here. In the case of post-1906 San Francisco, the buildings were built on land that was created from what was formerly waterlogged areas. Backfilled with soil and other debris. The biggest risk with this type of "landfill" is liquefaction during an earthquake.
Here they are talking about building on top of a mountain of modern municipal and industrial wastes. Many of these wastes are still in the process of decaying. So you've got methane needing vented, various toxic metals and chemicals that need to be ensured they are contained etc.
So yes, they are VERY, VERY different.
There's tons of apartment buildings being built. All along Tasman by Cisco are massive apartment/condo complexes, and the old IBM facility off Cottle Rd had a 1000 units recently completed.
Nobody is building new stand alone single family homes. High density, multi-story apt or condo complexes, complete with pools, rec rooms, gyms and shopping on the first floor are the norm. If there's a single family home being built, it's being ruled with an iron fist by HOAs that charge $300/mo for nothing.
Landfill tends to not be compacted as well as regular soil. Consequently it tends to liquefy more easily during earthquakes, leading to uneven settling and destruction of homes built on top. Nearly all the homes which collapsed during the 1989 Loma Prieta quake were in the Marina district which was built on landfill (albeit mostly from dredging the harbor). (They were also 3-4 stories, which happens to have a resonance frequency matching that of most earthquakes.)
Smell is not an issue. The landfill is typically covered with several layers of barrier several feet thick, including watertight plastic sheeting.. Drainage holes are left along the sides to capture and treat excess water which manages to seep in when it rains, while methane recapture piping extracts gases which build up due to biological decomposition for resale. A friend's house is built on landfill and he never would've known it if I hadn't remembered the location as being a landfill from back when I was in high school.
You can build on it, but the buildings have to be built much more sturdily than if built on regular soil, and you're still screwed if the ground settles unevenly causing the home's foundation to break. Usually the land is used for non-structural purposes, like a park.