There are 1.4 million underground storage tanks containing petroleum
products or other hazardous chemicals in the United States, says the
EPA (U.S. Environmental Protection Agency) and about 20% of these (or
280,000 tanks) are leaking today, the agency estimates. The other 80%,
of course, will leak some time in the future, since all human creations
are subject to the ravages of time.
EPA has studied the tanks that are leaking today and has concluded that
60% leak because of corrosion, 25% because of improper installation and
structural failure, 10% from loose fittings, and the remaining 5%
because of spills and overfills.
To combat this clear and present danger to the nation's supply of clean
water, the EPA in April issued proposed rules that all tank
owners/operators will have to follow (after the rules are finalized,
after a lengthy process of public hearings, rewriting and reissuance).
Under the proposed rules, owners or operators of underground storage
tanks (USTs) will have to install leak detection systems and to
demonstrate the financial ability to clean up any messes their tanks
The EPA's proposed regulations are particularly tough on 54,000 tanks
(4% of the total) that contain any of 701 specific toxic chemicals
listed in the Superfund law (CERCLA, the Comprehensive Environmental
Response, Compensation and Liability Act). NEW tanks built to hold any
of these 701 chemicals must be supplied with a "secondary containment"
system aimed at preventing leaks into the general environment. A
"secondary containment" system could be a second tank inside the first
tank, or it could be a concrete tank built around the first tank, or it
could be some kind of "impervious" plastic liner installed around the
first tank. Leak detection systems will be required between the first
tank and the secondary containment system. Existing tanks holding any
of these 701 chemicals must, within 10 years, comply with the same
requirements as new tanks. But the EPA has already announced that
variances will be available at the end of ten years for those owners
who demonstrate that their tank is protected against corrosion and
equipped with an effective leak detector.
Editorial comment: The EPA's proposed regulations seem certain to
contaminate the nation's underground water supplies. Even the
"secondary containment" systems required for hazardous chemical tanks
will not prevent environmental contamination though they will reduce
the rate at which contamination occurs. or many of the same reasons
that double-lined landfills will all eventually leak, double-lined
underground storage tanks will all leak sooner or later. A double-lined
tank will leak later, rather than sooner, meaning that our
grandchildren will pick up the tab, not we. But leak they will.
However, the most glaring problem with the EPA's proposed regulations
is its clear failure to keep gasoline out of the nation's water supply.
Half the nation's underground storage tanks (700,000 of them) contain
gasoline; every service station today has an underground gasoline tank,
if not more than one. Gasoline is a rich mixture of toxic chemicals.
For example, gasoline is 2% to 5% (or more) benzene, 6% to 8% toluene,
1% to 1.5% ethyl benzene, 2% to 5% xylene, and so on. Even the
additives to gasoline are themselves often toxic, such as ethylene
dibromide, which the government recently banned as a fumigant for much
of the nation's grain supply because it is carcinogenic. No doubt the
most famous additive is lead, which is now being phased out because of
its toxicity to humans and other forms of life. Unfortunately, as lead
is phased out, the benzene content of gasoline is being increased to
keep the gasoline's octane rating up.
Benzene is a potent human carcinogen. The EPA has set a "criteria
level" for benzene in drinking water, based on the agency's estimate of
benzene's ability to cause cancer. The EPA estimates that one cancer
would be caused among a million people if they drank water for a
lifetime contaminated with 0.66 micrograms of benzene in each liter of
How much water could be contaminated up to the EPA's "criteria level"
if a single gallon of benzene spilled from an underground tank? Knowing
that benzene has a specific gravity of 0.879, using arithmetic we can
figure out that five billion liters of water would be contaminated to
the 0.66 microgram/liter level by spillage of a single gallon of
benzene. Since most people drink two liters of water per day, or 730
liters of water in a year, we can see that a single gallon of benzene
is sufficient to contaminate a water supply that 68.5 million people
would drink in a year. That's how much water the people of Los Angeles
County (all 7.9 million of them) would drink in a nine year period--and
it could ALL be contaminated up to the EPA's "criteria level" for
benzene by a single gallon of spilled benzene.
We estimate that, at any given moment, there are at least two billion
gallons of gasoline stored underground in the U.S. and that about 100
million gallons of this is pure benzene.
The EPA is not requiring double-lined tanks for the nation's 700,000
gasoline tanks. It is, instead, requiring leak detection systems. Leak
detection systems are devices that tell you it's time to lock the barn
door because the horse left some time ago. The EPA's proposed
underground storage tank regulations are a prescription for disaster.
EPA plans public hearings in late May and in June, in DC, in Dallas,
and in San Francisco. For further information, contact Robin Woods,
EPA; phone: (202) 382-4377.
Descriptor terms: regulations; water pollution; water; leaks; epa;
hazardous chemicals; storage tanks; superfund; groundwater; editorials;
gasoline; benzene; emergency preparedness; lust; ust; benzene; cancer;
carcinogens; drinking water; statistics;