A question came up during the site tour
on February 14 as well as in an email to Gregg from Chris Rowe. We
thought we would include the Stakeholder group in our response:
"Chris Rowe asked me about the decision process to do borings deeper
than 10 feet in the reactor vault areas. In the scoping process for
the original study, we stopped at 10 feet strictly because of available
funding. The scoping of the project was to "10 feet or refusal."
But in that scoping, and in the original study document, we reserved
two cases where it might be appropriate to go deeper.
The first case was if we found contamination
at 10 feet and felt we needed to go somewhat deeper to characterize it.
The second was the case where the information gathered in the HSA
might indicate that we should. I am not aware that we've had the
first case occur yet. But the second case occurred during the HSA
investigation when we learned in detail the excavation of a majority of
the reactor vaults, basically a bowl cut into solid rock. We learned
in some cases that concrete debris was pushed back into the hole during
We discussed these conditions with the
tech advisory group at the time of reviewing those HSAs and suggested that
we try to get samples at depth, and decided to look for technology that
would allow us to do that. The sonic drill rig was chosen for the
reactor sites. Given the contamination seen at the SRE in our most
recent review of data with stakeholders, I think the decision was prudent.
Will we find contamination at depth?
I don't know. But it would be better to give DTSC and DOE that information
in the course of our work now so they can plan for a more detailed excavation
(with the money implications understood) than let them start a surface
remediation and find on their own that they need to go deeper. Chris
also asked about the analyses of the deep borings. We're doing basically
'everything' on the reactor areas -- all the analyses we have -- because
of the potential for issues."
Please let me know if you have questions.
Remedial Project Manager
EPA Region 9
Superfund Division (SFD81)
San Francisco, CA 94105
(415) 972-3167 w
(415) 972-3528 f
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