Typically in Maine, petroleum contamination is remediated utilizing techniques that don’t take into account energy consumption or the overall “carbon footprint” of the remedial option. Soil excavation is the most common method, while groundwater extraction and treatment is used for sensitive groundwater resources. Trucking contaminated soil has the obvious environmental impacts of fuel consumption and air emissions. Pump and treat groundwater systems consume large amounts of electricity for pumps and filters, and often generate wastes that requires special disposal. At a site in western Maine, St.Germain Collins designed and implemented a green technology for groundwater treatment that consumed no electricity, generated no waste, and had a carbon footprint limited to vehicle use for periodic site visits. This system was based on the fact that petroleum hydrocarbons in groundwater are degraded by microbes naturally present in the subsurface. Biodegradation is often limited by a lack of oxygen, and to accelerate the process, St.Germain Collins installed a ten well oxygen injection system. The effectiveness of the system was monitored by sampling five wells known to be contaminated. Before system startup, groundwater impacts were dominated by volatile petroleum hydrocarbons (VPH) with a high of 11,961 ug/L. After six months of operation, VPH at the same location was reduced to 4,599 ug/L. A similar pattern was observed across the Site with no significant rebound observed two months after system shutdown. Because of its effectiveness and minimal environmental impact, oxygen injection should be considered as a viable remedial method for petroleum contaminated groundwater in Maine.

1. Green Remediation of
Petroleum Contaminated
Groundwater Using Oxygen
Injection in Western Maine
Brian Bachmann, CG
Keith Taylor, CG
2012 Maine Water Conference
March 14, 2012

2. Introduction
Typically in Maine, petroleum contamination
is remediated utilizing:
• techniques that don’t take into account
energy consumption, or
• the overall “environmental footprint” of
the remedial option.
St.Germain Collins

3. Soil Excavation
• Environmental
impacts from
excavator, trucks,
recycling plant:
° Air emissions
° Fossil fuel
consumption
St.Germain Collins

4. Pump and Treat
• Groundwater extraction and
treatment systems (GETS)
are used for sensitive
groundwater resources.
• Environmental Impacts from
GETS:
° High electricity needs
° Air emissions
° Waste from pretreatment
and post treatment (e.g.,
iron removal)
St.Germain Collins

5. Natural Attenuation
• Allows hydrocarbons to
biodegrade completely on
their own; we only monitor
• Low-carbon footprint
• But it takes a very long
time--some sites have
been monitored since the
1990s.
• Monitoring for decades still
requires vehicle usage
St.Germain Collins

6. Site Description

7. Site Description
• Contamination first
documented in 2004.
• Free product diesel fuel
present, but erratic in
location and thickness.
• Also mixed diesel and
gasoline dissolved
phase contamination.
• Petroleum fingerprinting
indicates both old and
new contamination.
St.Germain Collins

8. Hydrogeology
• Glaciofluvial, deltaic, and
eolian sand deposits
mapped in area.
• Soil borings at site
penetrated up to 30 feet
of interbedded fine to
coarse sand with minor
silt.
• No clay or low
permeability material.
St.Germain Collins

9. Hydrogeology

10. Contamination
Approximate
Extent of
Contamination

11. Remedial Goals
• The goal of remediation was to reduce the
high concentrations of dissolved petroleum
downgradient of the site.
• DEP were primarily concerned with vapor
migration and free product.
• Owner wanted to reduce dissolved phase
concentrations to reduce vapor risk
• A clean site was not the goal.
St.Germain Collins

12. Remediation
• Certain conditions lead to choosing oxygen
injection:
– High permeability (easy for oxygen to move)
– Deep water table (precluded soil excavation)
– Relatively inexpensive, small carbon footprint
– Strong evidence of anaerobic biodegradation.
• Aerobic biodegradation is more efficient at
removing petroleum hydrocarbons.
St.Germain Collins

13. Remediation
• Evidence of anaerobic biodegradation:
– Low DO, SO4, NO3 in the middle of the plume
– High Fe, Methane, Heterotrophic Plate Count
(bacteria) in the middle of the plume
Dissolved
Oxygen
(ppm)
St.Germain Collins

14. Remediation
Sulfate (ppm)
St.Germain Collins

15. Remediation
• 10 oxygen injection wells
installed:
• 4 up-gradient of source
• 6 down-gradient of source
• 1-inch diameter
• 3 feet of 200-micron micro-
porous screen at the bottom
• 30-foot depth
St.Germain Collins

16. System Design
• Each well connected
to the oxygen source
by 0.25-inch tubing
sealed in road cut
• Oxygen source is
200-pound liquid
oxygen cylinder.
St.Germain Collins

17. Oxygen Source and Delivery
• Cylinder connected to a
manifold designed to
regulate the amount of
oxygen delivered to
each well.
St.Germain Collins

18. Contamination
Approximate
Extent of
Contamination

19. Initial Groundwater Quality
• In January 2011,
impacts dominated
by volatile petroleum
hydrocarbons (VPH)
• Highest total VPH
level in January
2011 was 11,961
ug/L at MW-10.
St.Germain Collins

20. Operation and Maintenance
• The system ran for six months without
interruption.
• Visit the site every two weeks, install new
liquid O2 tank, collect monitoring well
measurements.
• All site visits were coordinated with
company supplying oxygen. They were
already traveling to the area so additional
trip was not needed.
St.Germain Collins

21. Dissolved Oxygen Trends
• System operated without problems from
January 2011 until shutdown in June 2011.
• Background DO levels before system startup
were 1 to 3 mg/l.
• DO level of 40 mg/l was measured at well
MW-11 on May 27, 2011.
• Aquifer had become highly oxygenated, even
within the plume.
St.Germain Collins

22. Groundwater Quality at System
Shutdown
• By June 2011, total
VPH at MW-10 had
been reduced to
4,599 ug/L.
• 62% reduction at
MW-10
• 84% reduction at
MW-9.
St.Germain Collins

23. Groundwater Quality 2 Months
After Shutdown
• In August 2011, 2 months after system
shutdown, another round of groundwater
samples were collected.
• Wanted to assess potential for rebound.
• Rebounding of contaminant concentrations
common in groundwater remediation.
• Reflects a return to equilibrium conditions.
St.Germain Collins

24. Groundwater Quality 2 Months
After Shutdown
• Very little
rebound
• Total VPH
reduced an
average of
61%

25. How Green are these
technologies?
IN SITU
BIODEGRADATION?
DIG?
PUMP?

26. For More Information Contact:
St.Germain Collins
846 Main Street, Suite 3
Westbrook, ME 04103
info@stgermaincollins.com
(207) 591-7000