PASCOAG AND MTBE

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PASCOAG AND MTBE

• A BRIEF HISTORY AND UPDATE
• RI-DEM
• OFFICE OF WASTE MANAGEMENT

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PASCOAG
-Rural community located in the town of
Burrillville, RI -MTBE (Methyl Tertiary Butyl
Ether) is a commonly used gasoline
additive -Rhode Island MTBE drinking water
standard 40 ppb (parts per billion)
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PASCOAGS WATER SUPPLY

• Serves approximately 5000 people
• The Pascoag Water District used one 16 well,
  drawing 350 GPM (Gallons per Minute) from both
  the bedrock and overburden aquifers
• The well was activated in February 2001
• There was no backup water supply for the Pascoag
  Water District

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HISTORY

• August 30, 2001 A Pascoag resident concerned
  about an odor in his water has it tested
  results show MTBE over 400 ppb.
• Residents were immediately notified that they
  should not drink the town water and minimize skin
  contact.
• The RI-DEM was immediately brought in to identify
  the source. Dozens of properties were evaluated.
  Main Street Mobil is identified as the source
  within 2 days.

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• The owner of the Mobil station was brought to
  court to enforce RI-DEM requirements for
  exploration and remediation. The owner soon goes
  bankrupt. RI-DEM takes over all assessment and
  remediation activities.
• RI-DEM begins door to door delivery of bottled
  water for drinking, handing out 60 gallons per
  water customer per month.

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November 2001 A carbon filter system is
installed by RI-DEM at the public well. Water
could be used for bathing and other non-drinking
uses.
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January, 2002Four months after the problem was
discovered Pascoag residents are hooked up to the
neighboring Harrisville water supply and now have
clean drinking water. But this situation stresses
the Harrisville water systems capacity.
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EPA ASSISTANCE
Reallocated up to 400,000 in Federal Grant Funds
to assist with initial public water treatment
. Provided two 1 million dollar grants for
assessment and remediation.
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RI-DEMASSESSMENT AND REMEDIATION

• Given the immense size of the problem and the
  need for immediate action, assessment and
  remediation activities were performed
  simultaneously and in a phased approach.
• RI-DEM investigated and began remediation of the
  worst areas of contamination (on-site) first and
  then proceeded further into the problem.

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ASSESSMENT Assessment of overburden (soil)
contamination was substantially completed within
10 months of RI-DEMs involvement. Bedrock
assessment approximately is now 60 completed.
To date over 50 shallow and deep overburden
wells and 16 bedrock wells have been
installed. These wells are tested by RI-DEM
every three months to evaluate changes in
contamination over time.
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Floating gasoline (product) over 6 inches thick
was found over 500 from the source in shallow
bedrock. Significant deep overburden
contamination was found up to 1200 feet away.
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INTIAL TOTAL MTBE PLUME MTBE plume is over 1500
feet long and over 20 acres in size
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REMEDIATION
SYSTEM 1 Within 30 days of RI-DEM taking over,
soil venting system was installed onsite. An
on-site system pumping water from the site was
activated one month later. SYSTEM 2 Remediation
was expanded off-site six months later to include
five bedrock groundwater recovery wells. The
current system now draws groundwater onsite and
over 500 feet offsite from overburden and
bedrock.
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The four gas and diesel USTs were removed from
the former Main Street Mobil Station.
Approximately 1000 cubic yards of heavily
contaminated soil was excavated (approximately
100 dump truck loads).
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Current system has pumped and cleaned over three
million gallons of contaminated water and
successfully removed approximately 3000 gallons
of equivalent gasoline over its 2 years of
operation.
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TOTAL MTBE INITIAL
TOTAL MTBE CURRENT
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WELLHEAD REMEDIATION (SYSTEM 3)
A four month pump test was performed in 2003 at
the public well. The test was made to mimic the
normal pumping conditions of the well. Much lower
levels of MTBE were encountered than expected,
ranging from 40 to70 ppb (2001 MTBE
concentrations were over 700 ppb).
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FUTURE WORK

• DEM is currently evaluating remediation
  technologies in the mid-aquifer area including
  bioremediation, chemical oxidation and ozone.
• The type and scope of future investigation and
  remediation will be partially based on the
  intended use of the aquifer. Will this area ever
  be used for supplying drinking water in the
  future?
• Using the aquifer for drinking water will require
  additional assessments and remediation strategies
  that will not be needed if the area is to be
  classified as permanently contaminated and
  non-potable.