[CPEO-MEF] Kerr-McGee perchlorate remediation

[Lenny Siegel <lsiegel@cpeo.org>]

As a member of the ITRC (Interstate Technology Regulatory Council), on
September 8, 2004 I received a series of briefings about the Kerr-McGee
perchlorate cleanup in Henderson, Nevada, and the following day I took
part in a bus tour of the Henderson area. The lead presenter was Todd
Croft of the Nevada Department of Environmental Protection (NDEP). While
I had received similar briefings in the past, this two-day interchange
offered opportunities to ask penetrating questions and view the site up
close. Furthermore, the cleanup is further along than reported just a
few months ago.

The primary groundwater plume in Henderson emanates from the former
Kerr-McGee production site northward to the Las Vegas Wash, which it
enters through a surface seep as well as groundwater. Kerr-McGee, under
direct oversight by NDEP, intercepts the plume at three locations: On
site with a slurry wall and extraction wells; with wells mid-plume at
Athens Road, which is just upstream of local sewage treatment system
recharge basins; and with more extraction wells on the edge of the Wash.

The system now catches about 90% of the original perchlorate flow into
the Wash. By October, 2004, it expects the residual releases to fall to
about 100 pounds of perchlorate per day.

Water from all three extraction locations is pumped into a new two-stage
Fluidized Bed Reactor at the former production plant. This is a rather
large ex situ bioremediation system, based upon similar, but smaller and
simpler systems at the Longhorn Army Ammunition Plant (TX),
Aerojet-Rancho Cordova (CA), and the McGregor Naval Weapons Industrial
Reserve Plant (TX). The Kerr-McGee treatment system has proven more
challenging to operate, not only because the quantity of contaminant is
much higher, but because high concentrations of other (naturally
occurring) chemicals are present in the water.

American Pacific, owner of the plume from the nearby Pepcon Plant (site
of a massive 1988 explosion), is characterizing its flow, and NDEP
expects it to prevent perchlorate from that source from reaching the Las
Vegas Wash. The industrial park owner is investigating other property in
the area. While it's possible that other perchlorate (from Kerr-McGee or
other sources) may enter the Wash in the future, NDEP does not expect
the quantities to be significant in comparison to the main Kerr-McGee plume.

Perchlorate which has settled in the gravels of the Las Vegas Wash is
beyond the capture systems. However, additional extraction is not
planned. NDEP's modeling shows that with the current level of releases
into the Wash most of those deposits will flush out within about two
years, the time it would take to build a system to treat the gravels.
Sampling thus far is consistent with the model.

Additional modeling, coordinated with the results of Metropolitan Water
District sampling downstream in the Colorado River, suggests that
downstream perchlorate concentrations will fall below 2 parts per
billion by mid-2005. 

Of course, outside of Nevada there is no cleanup-oriented investigation
of water originating in the Colorado River. No one is looking at the
groundwater basins that have been recharged with contaminated Colorado
River water.

Nevertheless, assuming that the NDEP reports and projections are
accurate, the asserted success in capturing and destroying perchlorate
suggests that there is unlikely to be new treatment of Colorado River
water in California and Arizona. Concentrations are already below
California's Public Health Goal of 6 parts per billion (ppb), they are
unlikely to rise, and in fact they are likely to approach 2 ppb by the
time any new treatment system could be built. Only a promulgated
drinking water standard of 1 ppb would force such treatment.

Meanwhile the massive, expensive extraction and treatment system above
the Las Vegas Wash is approaching full efficiency, and it is expected to
operate for decades.

Lenny
-- 


Lenny Siegel
Director, Center for Public Environmental Oversight
c/o PSC, 278-A Hope St., Mountain View, CA 94041
Voice: 650/961-8918 or 650/969-1545
Fax: 650/961-8918
<lsiegel@cpeo.org>
http://www.cpeo.org
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