Special Bd. of Aldermen — 10/26/15 Page 13
impermeable cap similar to what we would put here but not encapsulated it. So those are the tannery waste.
But with this case of depleted uranium that we were trying to contain that was leeching into the groundwater,
we are going to be putting a wall around that to inhibit groundwater flow.
Alderman Tencza
So if | may just follow up, tannery waste it must be a problem for the last couple of decades with tannery waste
| would imagine in the northeast. So have there been any studies done to say that the waste, once it is
capped, is not an issue going forward, 10, 20, 30 years after it is capped?
Ms. Taylor There have been reviews that | believe the one site in Woburn that | am referring to and there
hasn’t been any issues with that capping of that material.
Mr. Millan-Ramos | have to add there are other sites where a secant wall per se has not been used but a
slurry wall which is less surgical, less effective or secure if you will, many of those sites, at least all the ones
that | know for years, they have been able to successfully contain liquid waste, not nearly as solid as what we
have in here. So we don’t have any reason to suspect that this will not perform as we need it to be.
Ms. Taylor Yes | think Darrin had mentioned the Gilson Road site that has a slurry wall, that’s another
Superfund site, we call it the Sylvester Site that has that type of a slurry wall that has been in existence, | don’t
even know how long. I’ve only been a manager for 2 years.
President McCarthy
| would point out that the Gilson Road site is a little different in that the slurry wall was constructed to contain
the groundwater while it was being treated and that the VOC’s have been primarily removed. So there isn’t the
issue of long-term leeching out from inside the slurry wall in that case, as far as | understand it.
Mr. Santos You are correct and I’m not an expert on that site. They were containing and pumping and treating
but they just recently, the EPA had | believe internal experts outside of the region do a hydraulic study on the
flow of water through that wall. One of the reasons was that it was one of the first slurry walls done under the
Superfund programs. It performed very well even after 30 years. So in terms of reducing flow across it, it is
still performing.
President McCarthy
It also occurs to me that we are talking now about the alternative of removing the lagoons, we have not talked
about the cost of that alternative and what it would cost to actually dig up the two lagoons that are on the
tannery property. Do we have a delta number for those?
Ms. Taylor Well our number in the engineering evaluation cost analysis that we came up with for just the
Mohawk Material, which would be the two lagoons and any of the other satellite areas is approximately $32
million dollars.
President McCarthy
As opposed to what was the number for containment?
Ms. Taylor Between $7 to $10 million. Our estimates are slightly larger than what the developer thinks but we
think it is going to be about $10 million dollars.
