Analyzing a complex oil spill at an Ottawa hospital

Spill Management
Analyzing a complex oil spill at an Ottawa hospital
By Dan McNicoll, Mark McCalla, Kathy O’Neill and Philippe Marleau
n January 2009, a large furnace oil
spill occurred beneath the Montfort
Hospital which is situated in the
east end of Ottawa, Ontario. During a $300M expansion program, a
50,000 litre underground storage tank
(UST) was installed just north of the “D
Wing” building of the hospital complex.
The UST supplies furnace oil to the hospital’s heating plant. A remote fill station
was located approximately 20 m from
the tank.
During final construction activities,
the remote fill pipe for the furnace oil
tank was inadvertently severed without
being repaired. In January 2009, during
a period of peak demand, the tank was
filled five times before strong petroleum
odours were noticed by the basement
staff. The hospital immediately evacuated the affected staff and retained exp
Services Inc. (exp) to determine the
source of the furnace oil odours and to
direct emergency response measures.
Emergency response
As part of the emergency response
program, indoor air samples were collected, portable air scrubbers were
brought in, furnace oil fill procedures
were immediately ceased, and an investigation was conducted to determine the
source of the furnace oil odours. After
some remote video camera work, a
break in the pipe was confirmed.
The furnace oil UST and piping was
subsequently removed and 1,200 tonnes
of furnace oil impacted soil were removed beneath the pipe break and around
the UST. Unfortunately, a significant
amount of furnace oil was determined to
have migrated directly beneath D Wing.
Interior sumps and sewers were inspected
and temporary oil recovery/groundwater
treatment measures were immediately
implemented, where necessary.
Subsurface Investigation
Exp conducted a detailed forensic investigation to determine the most likely
cause of the pipe break and calculated
that approximately 22,000 L of furnace
oil had leaked into the subsurface environment. Due to pending legal actions
I
64 | September 2011
Aerial view of hospital.
by the insurer, the cause of the pipe
break cannot be disclosed at this time.
A comprehensive subsurface investigation was performed to delineate the extent of the subsurface impact. In total, 28
interior and exterior overburden wells
and 33 interior and exterior bedrock
wells were constructed on the site, using
both conventional and unconventional
drilling techniques.
The site was found to be underlain by
approximately 1 - 2 m of granular fill
material, overlying native silty clay, and
silty glacial till. The till, in turn, is underlain by Ottawa Formation limestone
bedrock at depths ranging from 4 m to
10 m below grade. A major geological
fault also exists beneath the site and is
thought to pass directly beneath the affected D Wing building.
Bedrock groundwater flow direction
was found to be from northeast to southwest, or from the neighbouring residential houses towards the hospital. The
overburden groundwater regime was
found to be discontinuous and, where
present, was calculated to be flowing to
the south under a gradient of approxi-
mately 0.03 m/m.
The furnace oil plume was found to
have migrated beneath 75% of the D
Wing building footprint and towards the
adjacent off-site apartment building
property, located approximately 50 m to
the south. Large concrete earthquake
ballast slabs situated beneath the building served to channel and funnel the oil,
making its delineation (and subsequent
recovery) very difficult.
Stakeholders
The hospital’s medical records, decision support, and medical affairs departments are located directly over the
area affected by the spill. Health and
safety issues for these departments and
others located in the new wing needed
to be addressed throughout the remediation process. Measures are still ongoing to ensure that all concerns are met.
Hospital support services such as Facilities and Occupational Health and
Safety were key partners in the management of the situation, as was the Montfort
Hospital Governance. Another important
stakeholder was the hospital’s major tencontinued overleaf...
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Spill Management
Tank removal.
ant, the Department of National Defense.
The hospital is surrounded by a
neighbouring community whose residents have their own well and septic systems. Monitoring measures were put in
place and regular community communication sessions were offered to address
their concerns. A residential apartment
building is located directly to the south
of the hospital, so owner and resident
concerns regarding the spread of the
spill onto their property needed to be addressed on an ongoing basis.
Regular communication with various
ministries including Ontario Health and
Long Term Care, the Ontario Ministry
of the Environment (MOE), The Technical Standards and Safety Authority, the
City of Ottawa and other governing bodies, had to be addressed. Because the
project was not fully completed at the
time of the spill event, coordination was
needed with the general contractor and
prime consultant.
Finally, as the ultimate payer, the insurance company, the insurance adjuster,
and their broker representative were included in all aspects of communication
and overall management of the situation.
Remedial options analysis
Based on the findings of the subsurface investigation, a Remedial Options
Analysis (ROA) was performed to select
66 | September 2011
the most appropriate solution. The ROA
included a comprehensive review of
available remedial technologies; the selection of four preferred technologies or
options; preliminary cost estimates for
each option; estimates of the anticipated
operating period; and, an estimate of
hospital staff displacement duration.
The ROA focused on a phased approach to the overall site remediation
program. The first phase was concentrated on the recovery of furnace oil
product. The second phase consisted of
the establishment of the final remediation objectives (i.e., background, potable/
non-potable water, or site specific criteria). The third phase, if required, would
be to examine additional treatment technologies that could be used to reduce the
length of time required to attain the desired final remediation objectives once
all of the furnace oil product had been recovered (i.e., the addition of surfactants,
oxygen releasing compounds, etc.).
Based on the site conditions, it was
agreed that the provincial potable
groundwater criteria would be used as
the remediation criteria.
The four remedial options that were
ultimately selected for more detailed
costing were 1) natural attenuation; 2)
multi-phase extraction (MPE); 3) partial
excavation and MPE; and 4) complete
excavation. The preferred remedial option that was ultimately selected was
MPE.
MPE remediation system
Exp designed the multi-phase extraction system to recover free phase furnace
oil; petroleum impacted groundwater;
petroleum vapours beneath the building;
and to enhance biological degradation of
the residually impacted soil beneath the
building that could not be removed.
The MPE system involved the installation of 16 interior recovery wells
within the basement of the building and
13 exterior recovery wells along the
southern property boundary to prevent
off-site contaminant migration. All of
the recovery wells are equipped with
pneumatic submersible pumps, which
recover oil, water and vapours from beneath the building and direct them to an
exterior, on-site facility for treatment.
Piping from each recovery well is directed beneath portions of the floor,
within wall cavities, and above the ceiling. Installation of this piping distribution system within an operating hospital
required extensive planning, coordination, security, installation of elaborate
infection control barriers, and testing to
demonstrate containment and treatment
of petroleum vapours within the barriers
prior to their removal.
Pilot and full scale remediation
Prior to the design of the full scale
MPE system, a readily available, small
packaged MPE unit was used on-site in
order to provide some immediate control of the subfloor vapour emissions;
collect and recover some of the furnace
oil product; confirm the appropriateness
of using MPE at this location; obtain site
specific hydraulic conductivity and air
permeability measurements; assist in
sizing of the vacuum blowers, water
pumps, oil/water separator, etc.; and, assist in determining the volumes of water
and air that needed to be withdrawn
from the subsurface for regulatory permitting purposes.
The pilot test successfully demonstrated that a full scale MPE system
would be effective at this location. Sitespecific soil parameters were calculated
and used in the design of a full scale,
permanent MPE system. The final design included three large vacuum blowcontinued overleaf...
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Spill Management
Treatment System.
ers, 29 pneumatic submersible pumps, a
large compressor, an elaborate sediment
filtration system, liquid and vapour
phase granular activated carbon, an
oil/water separator, and a sophisticated
control system with remote access and
alarm capabilities.
The full scale MPE remediation system was activated in January 2011 and
has proven to be very effective. To date,
approximately 60% of the 22,000 L of
furnace oil product spilled has been recovered and petroleum vapour concentrations within the hospital have been
reduced to acceptable levels.
Initial capital costs for the remediation system and emergency response
measures were in the range of $8 to $10
M, and the monitoring and maintenance
costs for the anticipated 10 to 15 years
of operation are expected to be in the
range of $10 to $15 M.
Indoor air quality
Immediately after learning of the
spill event, hospital staff became very
concerned over their exposure to potentially hazardous air contaminants associated with the oil. In order to ensure
their health and safety, the hospital engaged exp to conduct indoor air quality
monitoring and provide recommendations on other mitigative measures that
could be employed.
68 | September 2011
An indoor air monitoring program
was implemented and is presently being
conducted on an ongoing basis, including the regular collection of indoor air
samples for laboratory analyses of
volatile petroleum hydrocarbons (PHC)
and real time, direct read, monitoring of
total volatile organic compound (TVOC)
levels.
In addition, two sophisticated, real
time TVOC monitors were installed in
the D Wing basement, which provide
continuous readings and record all readings on a data logger. These two units
are equipped with audio/visible alarms
in the event of elevated readings.
Although, at present, there are no
Canadian or US standards for TVOC,
the Health Canada guideline indicates
target and action levels of 1,000 and
5,000 µg/m3, respectively, are being discussed. The European Community indicates that, at a TVOC exposure over
3,000 µg/m3, symptoms such as odours,
irritation, and discomfort may occur and
complaints may be expected.
Since the operation of the pilot, and
subsequent full scale, remediation system, concentrations of TVOC have decreased and have remained stable in
what is considered to be a normal range.
In addition to the field measurements, indoor air samples are collected
for laboratory analyses at nine locations
every three months. Sample locations
are in rooms where there were previous
complaints of odours, in unoccupied
rooms awaiting occupancy, and in areas
situated above the oil plume. Analytical
results are compared to Ontario Ministry
of Labour (MOL) Occupational Exposure Limits and calculated MOE risk
based target levels for the tested parameters. Over the last year, all measured
parameters were below these levels.
Benzene concentrations ranged from <1
µg/m3 to 3.6 µg/m3, which is much less
than the MOL permissible occupational
exposure limit of 1,600 ug/m3.
Lastly, exp recommended that the
ventilation system in the basement of the
D Wing be adjusted to increase the air
pressure so that it is positive with respect
to the subfloor. With the negative subfloor pressure created by the MPE system, air flow within the basement is in a
downward direction. This prevents potential vapours from migrating upwards
into the hospital environment. To monitor air flow direction, there are currently
four manometers installed within the
basement floor that record and log the
pressure difference between the office
environment and the subfloor regime.
MOL investigation and findings
The local Ministry of Labour office
conducted a comprehensive investigation in order to determine whether the
remediation system and monitoring programs were sufficient to safeguard staff
from being exposed to unacceptable
health risks associated with the oil spill.
After their review, the MOL concluded that the site remediation system
has proven to be effective and worker
exposure to airborne petroleum hydrocarbons is acceptable. There is no evidence to indicate that a chemical hazard
presently exists for workers at the hospital, due to exposure to airborne petroleum hydrocarbons associated with the
fuel oil spill.
Dan McNicoll and Mark McCall
are with exp Services Inc.
Kathy O’Neill and Philippe
Marleau are with the Montfort Hospital
For more information,
E-mail: [email protected]
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