Environmental Engineering Reference
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legislature, Republican Bill Galvano. Representative Galvano proposed that the whole town be
moved to a new site and sent the responsible party a proposal suggesting that they pay for most of
the cost of relocating residents to a new site of their selection in exchange for dropping their 2005
lawsuit. Tallevast residents apparently asked for assistance after some of them were declined rei -
nancing of their mortgages because of the plume of contamination from the former American
Beryllium plant (Marsteller, 2005).
To address residents' concerns over their property values, the responsible party established the
Tallevast Property Value Protection Program for current homeowners interested in selling or rei -
nancing their residence. The program offers a payment for the reasonable difference (up to 40%), if
any, between the actual sale price negotiated and the appraised fair market value if there were no
associated groundwater impact. The program also provides assistance with residential seller support
services such as appraisals, home inspections, brokerage services, and home marketing assistance
The Tallevast site provides an excellent example of how to manage dynamic community rela-
tions through multiple channels to ensure that relevant information is distributed to community
stakeholders in a timely manner. The responsible party hosted frequent and widely announced
public meetings to explain the ongoing work and staffed these meetings with the consultant team
that was performing the work. In addition, the responsible party maintained a website with a com-
plete report repository and prepared dozens of informative newsletters that were mailed to the
affected residents. Communications have at times been contentious, but the responsible party
ensured that residents had ample opportunity to register their concerns and inquire directly with the
parties performing the work.
8.4.5 D
ISCUSSION
The Tallevast saga continues. Looking back on all that has transpired, it might be tempting to sec-
ond-guess how the site was addressed. But several features of this case would probably have caused
most environmental professionals to follow the same course and arrive at a similar conceptual model,
only to discover later that it does not quite i t. By following conventional wisdom and orienting an
investigation around biodegradable hydrophobic chlorinated solvents—as is typically done at these
types of sites—the persistent and extremely mobile nature of 1,4-dioxane was not effectively
assessed. The bias in the sampling and analytical methods for 1,4-dioxane in open-cased irrigation
and domestic wells made a signii cant difference as well. The peculiar mounding seen in the site
potentiometric surface map was generally consistent with the site location on a relative topographic
high; yet, the magnitude of the mounding appeared greater than the local topographic relief.
Nevertheless, most hydrogeologists would probably not start out with a conceptual model that
included an unknown 50 gallons/min water main leak next to the source area! This feature alone was
probably responsible for a much larger mass fraction leaving the source area in multiple directions
than could have been anticipated to occur under a natural gradient.
The Tallevast case is a reminder that a conceptual model is always a work in progress, to be revisited
and updated frequently as more data become available, and whose assumptions should be periodically
questioned. On the basis of the documents reviewed by the author, it appears that the responsible party,
consultants, and regulators involved have been quite effective at adapting to changing conditions and
have made substantial progress to address a complex and vexing 1,4-dioxane plume.
8.5 STANFORD LINEAR ACCELERATOR CENTER GROUNDWATER
CLEANUP SITES
The Stanford Linear Accelerator Center (SLAC National Accelerator Laboratory, hereafter SLAC)
site provides examples of 1,4-dioxane migration behavior in low conductivity bedrock aquifer
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