Service Station Remediation

1
Title Page
Bioremediation of contaminated soil and
groundwater at a service stationWaterloo,
Ontario, Canada
2
Site
The gas station at Phillip and Columbia Street
was sold to a new company and any soil and
groundwater contamination of the site due to its
previous operation by Sunoco had to be removed.
3
Excavation and Tank Removal
  The old gasoline tanks were removed and holes
bored to detect gasoline and then a deeper
excavation was done to the groundwater level to
check for this contamination
The water surface showed visible signs of oil
contamination.
4
Drilling
The soil that was contaminated was excavated and
removed to a secure landfill site To remove, or
at least reduce, the contamination of the
groundwater below the soil, holes were drilled
and pipes were installed around the edge of the
contaminated zone
These pipes had perforated sections spanning the
soil and groundwater regions and going a few feet
below the water table The larger pipes surrounded
the contaminated areas and were all then joined
to the vacuum pumping systems
5
Pumping
The pipes were joined together at the surface and
pumps were attached to these pipes. The pumping
systems pumped a mixture of groundwater, pure
gasoline product floating on the surface of the
groundwater and soluble products from gasoline
that had entered the groundwater. These soluble
products would have included benzene,
ethylbenzene, toluene and xylenes. The
mixture of gasoline, soluble products from
gasoline products and water was pumped into a
tanker truck on the property and disposed of
after separation into the two phases of water and
gasoline. The water would have contained the
water-soluble components.
6
X-sectional Diagram
To Separation and Collection
Pump
Excavation
Soil
Free gasoline product
Groundwater
Cross Sectional Diagram of excavation and wells
7
Final Operations

• Pumping continued for some months until most of
  the free product and soluble components had been
  removed from the immediate vicinity of the site.
  Pumping also ensured that no more migration of
  the soluble components in the groundwater could
  occur. A negative gradient was established during
  pumping so that surrounding contaminated water
  flowed into the site and not away from it.
• Pumping would have to have been continued for
  many years if ALL of the soluble components in
  the groundwater needed removal through this pump
  treat methodology.
•  
• The residual soluble components were assumed to
  have been remediated through biological
  mechanisms in the groundwater.
• In this particular case, bioremediation was used
  as a final cleanup operation, but the bulk of the
  materials were removed via the pump and treat
  method. This is often referred to as polishing
  that is, removal of the residual, low levels of
  soluble components through bioremediation
  activities performed by indigenous microorganisms

End