What will happen to a sinking California? Just ask San Luis Obispo

from Grist:





For those wondering why California is sinking, look no further than San Luis Obispo. Not too long ago in that idyllic Central Coast city, an overdependence on groundwater became a destructive and expensive problem that today could serve as a warning to cities and counties throughout the state.

In 1989, amid one of the longest droughts in California history, the city’s water supply had reached a critically low level. Officials implemented mandatory water reductions of 20 percent for businesses and their 40,000 residents. And, for the first time in San Luis Obispo’s history, it began pumping groundwater. It drilled massive water wells. By 1990, the city was getting about 40 percent of its water from the ground.

Slowly, the earth began moving. The ground underneath buildings started to sink as the water supporting it was pumped to the surface. One family reported a quarter-inch crack that started in the kitchen floor and began creeping throughout the house.

The Bear Valley Center, a shopping center near one of the city’s major extraction wells, began to bend into a V-shape as the land beneath it sank. It suffered from what geologists call differential subsidence, in which varying soil composites result in certain spots sinking faster than others. The middle of the shopping center was sinking quicker than the rest, and it was causing major problems. Sidewalks cracked and sloped back toward the building. Doors and windows in the shopping center became jammed in place. Business owners couldn’t fully close their doors at night and were forced to use large chains and padlocks to secure their shops. ................(more)

http://grist.org/climate-energy/what-will-happen-to-a-sinking-california-just-ask-san-luis-obispo/