Alternative 5 in Detail
Prior to implementing this remedy there will be a series of on-site
studies to determine both effectiveness and appropriate treatments.
Consequently, there will be considerable more detail released in the future,
including a health and safety plan on measures to control dust emissions.
The areas associated with the pond bottoms will be solidified using in
situ stabilization. In situ
involves underground mixing of concrete soil and waste to produce a solidified
column. The areas receiving solidification are those that have toxic waste
extending downward to contact the watertable. In
situ stabilization would prevent any further groundwater contamination and
allow natural attenuation (dilution) of toxins already present.
The amount of area actually remediated is only a few percent of the total
area that will be covered by the cap. It is unclear at this time how extensive
the in situ stabilization will be, how
far laterally it will extend, and how deep. The number 15,000 cubic yards of
solidification has been used, and a map by Parsons Engineering (Figure 3 of the
Remediation Construction Document, August 1996) shows solidification only in the
former ponds area. Remedial Investigation data shows far more areas would
require solidification treatment.
Areas containing phosphate
that must be excavated for consolidation will need to be treated prior to
removal. This treatment is likely to involve stirring with augers to expose the
elemental phosphorus to air for conversion to phosphate.
After the solidification is in place several areas would be excavated and
consolidated on top of the former pond areas. All of the slag areas in the
Northern property would be consolidated, as would the pond 42 area and all of
the top soil and roads in and around the main plant area. Under the Residential
option there are additional areas in the Northeast and Southeast property that
would be excavated and consolidated. The commercial option omits treatment of
these areas. Excavated areas would be backfilled with clean dirt brought in from
off-site. The consolidated mass would be capped with layers of geotextile fabric
and earth. A drainfield is installed on the top and the material inside stays
dry since it is above the watertable. Estimates are that it will take 8 years
for contaminates in groundwater to attenuate to background levels, except for
radium-226 which will take slightly longer.
At this time both the borders and the height are unknown. The public has
been told the base could be anything from 20 to 30 acres and height estimates of
15 to 40 feet. A good guess is about 25 acres at the base rising to 30 feet
high. This is roughly 3 football fields long, 3 football fields wide, and 3
stories tall. No information is available on the effects of storm surge or high
winds on the structure. Nor is there any information on the potential for the
mass to generate sinkholes from effects on ground water flow. There does not
appear to be a similar structure built in river coastal areas. It is fair to
call this plan "experimental" since there are many unknowns related to
long-term stability.
The EPA prefers to use the term "landfill" only when structures
have a defined bottom, such as a RCRA approved liner. However, it is fair to
call the Stauffer structure a landfill, or for that matter, a dumpsite.
The area occupied by the final dumpsite will be about 40 acres, based on a
1994 property assessment. According to this report one parcel in the northeast
area would be developed as residential. The remaining portion would be developed
as commercial. The 40 acres comprising the final landfill will be deeded to
prevent any development, and a maintenance bond likely will be required. Since
the material is radioactive and elemental there is no "half-life" for
the structure. The landfill will likely be plainly visible for a millennia.
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