What is the impact? The contaminants seep into creeks where it contacts people and critters, poses a vapor intrusion risk to occupied basements, and poses a risk to contractors digging. Basement dewatering similar to the Oregon Expressway underpass can cause movement of these plumes over time, thereby exacerbating the problem.
An important development last week occurred in the scientific and environmental community where the toxicity of TCE has been clarified by USEPA. The news is not good, but should inform the seriousness we take the issue as we manage this over the future decades. "The USEPA is classifying TCE as carcinogenic to humans by all routes of exposure, based mainly on its high risk of causing kidney cancers, but also on Non-Hodgkin’s lymphoma and liver cancer."
Here are some links where the coverage was originally flagged to me, with the USEPA statement as the third link:
Blog Post: Web Link
USEPA Health Assessment: Web Link
My experience, is that the City could improve the attention to the issue and its long-term impact. The City has old maps of plume extent - and they should be current. The Fire Department did not seem to respond well when releases from a broken recovery well were called in. Public Works employees who dig and work in these zones are not informed of hazards. I tried to stimulate engagement, but broadly, this does not gather the attention it might, and would encourage the City to engage deeper, and create a stronger dialogue with the potentially responsible parties. (This is a dialogue I am not part of, but experience dictates that the discussion maybe too cozy, and as such too much comfort is accidentally enjoyed - and folks aren't protected.)
Once again, Palo Alto can actually be a the forefront. Thousands of communities are impacted, and it has been difficult for local government to find its role when this is not a problem they caused or controlled its cleanup. It is not a spend issue, but rather a value that needs more strongly to be lifted up inside the city. The sky is not falling, but we can do more to improve the longterm safe guards.