Tesla website says:
((( NUMMI factory was used by Toyota to produce the Corolla and Tacoma vehicles using the industry-leading Toyota production system. It is one of the largest, most advanced and cleanest automotive production plants in the world. ))
(( New United Motor Manufacturing, Inc. (NUMMI) has previously identified environmental conditions at the Tesla Factory which affect soil and groundwater, and has undertaken efforts to address these conditions. Although we have been advised by NUMMI that it has documented and managed the environmental issues at the Fremont site, we cannot currently determine with certainty the total potential costs to remediate pre-existing contamination, and we may be exposed to material liability as a result of the existence of any environmental contamination at the Fremont site. )))
NUMMI was appraised at about $1.07 billion. And Toyota gave it to Tesla for about $42 million.
Read about CERCLA law. The primary liability is on Toyota/GM - the ones who caused the pollution. Besides, Tesla has the political support of the Obama administration as well as the Governor of California, Jerry Brown.
If they got an axe to grind, they can go after the oil companies that are doing the hydrofracturing, contaminating the subsoil to the tune of millions of acres. The biggest polluter of them all? The Federal Government with its nuclear waste, nuclear bomb testing, etc.