Contaminated utility corridor adjacent
to a service station.
Organic and/or aqueous liquids
flow downhill and travel
along the path of least
resistance. Disturbed soil or
granular backfill surrounding underground
infrastructure, such as water,
sewer, telecommunications, gas or
electrical services, facilitate the subsurface
migration of liquid phase contaminants.
As a consequence, utility corridors
represent “preferential migration
routes” and become readily contaminated.
In urban environments there are
numerous potential sources of subsurface
contamination. Historically, single
wall, steel tanks installed underground
over the past 50 years represent
one of the most common sources of
subsurface contamination, particularly
with regards to petroleum hydrocarbon
products. Information published by
Environment Canada indicates that
without adequate corrosion protection,
up to half of these types of storage tank
leak by the time they are 15 years old.
Due to the co-location of utility corridors
and vehicle refueling facilities
along major transportation routes,
many instances of utility corridor contamination
involve hydrocarbons leaking
from underground storage tanks
and fuel delivery systems at automotive
service stations. A US study
reported by Holsen and Park (1991),
indicated the majority (89%) of incidents
involving contamination of water
distribution systems were caused by
automobile related products such as
gasoline, diesel and motor oil.
The environmental and health and
safety risks posed by petroleum hydrocarbons
within utility corridors may
include preferential contaminant
migration, vapour migration to building
basements, contamination of
drinking water supplies, explosive
atmospheres in sewers and conduit
based utility systems, exposure of utility
workers to contaminated soil and
groundwater, to name but a few.
Although these risks are well established,
the nature and degree of chemical
and physical damage that these types of contaminants can cause to a
diverse range of material receptors
(buried infrastructure) is an emerging
science that has not achieved a similar
level of recognition or understanding
within the environmental management
field. What is clear from our work with
a broad range of utility owners is that
this type of damage often represents a
significant risk or liability with respect
to asset management and, depending
on the nature of the utility, has considerable
potential to jeopardize public
health and safety.
The ability of environmental pollutants
to damage man-made materials and
structures was first recognised in a 1983
guidance document issued by the UKbased
Interdepartmental Committee on
the Redevelopment of Contaminated
Land entitled “Guidance on the
Assessment and Redevelopment of
Contaminated Land, (ICRCL 59/83)”. In
this document, acids, chlorides and sulphates
were identified as hazardous substances
because of their ability to cause
deterioration of concrete foundations.
Organic compounds including “oily and
tarry substances” were noted to have the
potential to attack plastics, rubber and
other polymeric materials used in pipe
work, service conduits, jointing seals and
protective coatings on concrete and metals.
In addition, organic compounds were
known to migrate through plastic pipe
work without causing structural failure
and thus contaminate drinking water
supplies.
Adverse effects associated with
utility corridor contamination may
include:
Hydrocarbons may permeate directly
into drinking water supplies and contaminate
potable water supplies above
regulatory limits;
Seals, sealants and protective coatings
may swell or be destroyed;
Exterior polyethylene sheaths may
swell and delaminate from underlying
surfaces and become more permeable
to water, resulting in corrosion of
internal components;
Dissolved hydrocarbons in groundwater
may act as a carbon-based food source which promotes the growth of
biological organisms that can cause
increased corrosion rates in metal and
concrete structures;
Hydrocarbons will dissolve and
destroy tar or bitumen-based products
including black fibre duct conduit,
waterproof coatings on foundation
walls and coal tar enamel coatings on
gas and oil pipelines;
The interaction of fuels with buried
infrastructure may result in the release
of hazardous degradation by-products,
such as polycyclic aromatic hydrocarbons
(PAH) and asbestos, contributing
to secondary contamination and unexpected
environmental and health and
safety risks.
Some underground materials (such
as products containing creosote or tar)
may become so severely damaged that
the utility no longer meets design specifications.
For example, black fibre duct
(BFD), also known as “Orangeburg
Pipe”, is commonly used to house electrical
and telecommunication cables. When exposed to gasoline the BFD
swells and blisters and the conduit can
no longer be used to house new cables
and the removal of existing cables may
be hindered or prevented.
Coal tar enamel coatings are often
encountered on gas distribution lines.
Under normal conditions the enamel
coating is a hard, brittle, almost glasslike
material that ordinarily remains
well bonded to the gas pipeline over a
long, almost indefinite, life span.
When exposed to gasoline, the coating
may become soft, friable and completely
disbonded from the underlying
steel pipe.
The adverse effect of petroleum
hydrocarbons is not limited to coal tar
enamel coatings. Gasoline and diesel
also cause polyethylene coatings to
swell and delaminate from the underlying
steel pipe. Under normal conditions
the steel pipe is also coated with
a coal tar-based material under the
polyethylene sheathing; however, this
coating is no longer present on this
section of the pipeline.
Although the potential hazard that
hydrocarbons such as gasoline and
diesel pose to buried infrastructure was
recognized more than two decades ago, current environmental legislation
in North America has focused solely
on protecting human health and safety
and ecological receptors, not buried
infrastructure. Most environmental
regulators consider infrastructure damage
to be a civil matter that is best
addressed by negotiation and, if necessary,
by litigation through the application
of tort law, as typified by Rylands
and Fletcher.
Due to the absence of suitable criteria
to assess impacts to materials
encountered within utility corridors, it
has been the author’s experience that
damage to underground infrastructure
is often underestimated or overlooked.
This problem is exacerbated by investigation
techniques that do not intersect
utility bedding materials in which contaminants
migrate and accumulate. Offsite
boreholes or excavations are often
advanced at a safe (or regulated) distance
away from utilities to minimize
the risk of causing physical damage.
Consequently, they often fail to identify
contamination localized around the utility
and provide an inaccurate assessment
of off-site conditions.
In instances where off-site contamination
is not identified or is not considered to represent a concern from an
environmental perspective, utility
integrity and worker/public health and
safety may have been compromised by
the existence of unidentified and/or
unrecognized infrastructure damage.
Whenever off-site contamination is
known or suspected, most jurisdictions
require the responsible party to notify
adjacent landowners of the presence of
contamination. However, utility owners
and operators generally do not own
the land through which their rights-ofway
run. Therefore, they are frequently
excluded from the notification
process and do not have an opportunity
to properly assess all the risks associated
with contamination in their utility
corridors.
Acknowledgment
The author wishes to thank Josef
Pach (TELUS), Ferenc Pataki (Terasen
Gas), Kevan Van Velzen (City of
Calgary) and Mike Zemanek (Alberta
Environment) for their kind permission
to publish this article.
