High Risk of Liquefaction in
Proposed Patterson Ranch Development
These photos show wetlands in
Coyote Hills. The United States Army Corps of Engineers and
Environmental Protection Agency jointly define
wetlands as: Those areas that are inundated or saturated
by surface or ground water at a frequency and duration
sufficient to support, and that under normal circumstances
do support, a prevalence of vegetation typically adapted for
life in saturated soil conditions. Wetlands generally
include swamps, marshes, bogs, and similar areas.
The map below shows parts of
the Bay Area where soils are at risk of liquefying in a
strong earthquake. A 4.2 magnitude earthquake on or near the
Hayward Fault hit Oakland on July 20, 2007. A 4.2 magnitude
quake shook Lafayette on March 2, 2007. Geologists have long
said the Hayward Fault is primed for a major snap—magnitude
7 or higher—and that the chances of one happening within the
next 30 years is high.
Liquefaction occurs when
loose, waterlogged soil is shaken. It loses strength and
behaves like a fluid, causing buildings to sink in much the
same way your feet sink into soggy sand at the edge of the
When this happens, the ground
isn’t strong enough to support structures; pipelines snap,
and buildings sink and tilt. The risk is highest on
artificial fill and along creeks and rivers.
An ancient delta that
underlies much of Fremont, made of silt deposited by Alameda
Creek, is rated at high risk (see orange area of Fremont).
Sources: U.S. Geological
Survey and California Geological Survey 2006;
As the map shows,
Ardenwood/Forest Park is highly susceptible to
liquefaction in a strong earthquake.
Is it logical and reasonable to build
520 high-density 2-story housing units, as proposed in the Patterson Ranch development, in
front of Coyote Hills Park? Fremont has plenty of developable land, closer to
the center of the city, which is at lower risk. Also, much of Patterson Ranch is
wrapped by Crandall Creek, where its water would seep under the ground of the
proposed development (see photos: top, east of Ardenwood Blvd.; bottom, west of
Ardenwood Blvd.). This land is part of a floodplain.
Strong afternoon winds from SF Bay (less than a mile away) could exacerbate fires if gas and water line break in an earthquake. Housing collapse is more likely given their construction on manmade fill (require more than 130,000 cubic yards of soils to raise above flood level) on top of liquefacation-prone soil.
Across from the proposed Patterson Ranch development, the
15.5-acre Tupelo lot is being built densely with 276 3-story condos/townhouses
and houses (see photo above).
If added to the proposed
520 housing units, there would be 800
housing units built on land that is highly susceptible to liquefaction.
Multiplying 800 units of apartments/condos/townhouses/houses by 4 (average number of
residents per housing unit) results in an additional 3,200 Fremont
residents, who would need City services in an emergency. This is on top of the
current residents who live in the 5,000+ densely packed homes in Ardenwood and
Don’t you think it is the
responsibility of the Fremont City Council and Planning Commission to ensure our
safety rather than approve a high-density housing development that would
jeopardize local citizens’ safety?
Developers would like to diffuse the problem by saying they would
do whatever they can to minimize the dangers. What technology is a match for the
strong forces of nature?
In conclusion, given the issues of liquefaction, floodplain, and
residents in an area already with the highest density in Fremont, should the
Fremont city council have approved this proposed 520-housing unit Patterson Ranch
Fremont experienced a 5.7 magnitude earthquake on October
Click on the link below to see
a simulation of 7.5 magnitude earthquake.
Trailer simulates earthquake (Then click on the small
square on lower right to start video.)