Re: Ground-Water Treatment Wastes Valuable Resources

[Mel Smyre <msmyre@primenet.com>]

The pumping of groundwater into surface waters as part of a mitigation
action does appear common. This is also the case at Twin Cities Army
Ammunition Plant (TCAAP) in Ramsey County, Minnesota, a Superfund site, as
part of the boundary groundwater recovery system. The deep groundwater
acquifer is tapped "uphill" from a pollution plume to prevent further
spread of polluted acquifer waters under the cities of New Brighton and St.
Anthony. Some water is used at the TCAAP site and excess water is
discharged into Rice Creek, which runs through my backyard on its way to
the Mississippi River. This situation has existed over ten years and the
acquifer pollution plume has shrunk somewhat -- it certainly would have
spread underneath Minneapolis if this action were not being taken.

Rice Creek runs somewhat higher because of the discharge. Erosion has been
periodically severe in the last 8 years along the stream in some areas,
resulting in significant loss of land and trees. Watershed owners are now
bearing a cost of about $25 per linear foot (the remaining 25% of costs
after support from the Rice Creek Watershed District and local government
grants) for installation of riprap or other erosion control measures. The
erosion control measures have some impacts on wildlife (waterfowl, fish,
shellfish) which are not considered at any government level.

The excess water empties into the Mississippi River upstream of the
drinking water intake for the city of Minneapolis (and starting with St.
Paul, many other cities downstream). In this case, replenishment of the
acquifer may be happening but hardly at a rate of the pumping -- shallow
depth groundwater is the greatest beneficiary.

There is a URL for the Operating Unit involved reflecting pump and treat
for the groundwater portions. This site is based on reports up to 1992.
(Later reports don't appear to be online, but are available either at TCAAP
or the public library at Shoreview, Minnesota.)
http://www.frtr.gov/abstracts/00000016.html

A good description of TCAAP hydrology including effects on the pollution
plume at different depths is at 
http://denix.cecer.army.mil/denix/Public/Library/Remedy/Twin/twin02.html

/s/Mel Smyre
Community Member, TCAAP RAB