Soil and Water Contamination

I am interested in the health of soil and water, and have heard many stories about high levels of toxicity in the Bay Area ("nothing lives in the bay water, because of all the oil spills", "Don't get vegetables at the farmer's market from these farms, they are from an area with toxic soil"...) 
I know the dump in Mexico City affects the surrounding elements with runoff and whatnot, so here are some basic questions:

How fertile/toxic is the soil in SF and in MC?
What kinds of toxins are present?  Why?
What is being done to clean them up?  Where does the contaminated soil go?

What toxins are present in the water supply?  How safe/unsafe is the tap water? 

Here are some links I found useful in beginning to answer some of these questions:

http://articles.sfgate.com/2009-02-26/news/17188773_1_pg-e-coal-tar-chemicals

http://www.sfexaminer.com/local/A-supersize-cleanup-effort-97990319.html

http://www.epa.gov/region9/water/dioxin/sfbay.html

http://www.nap.edu/openbook.php?record_id=4937&page=1

-Ariel H.