Page 8 - Moving the Earth_ The Workbook of Excavation

LAND CLEARING AND CONTROLS

1.8 THE WORK

CONTAMINATED GROUND

Legal Basics. The discovery of contaminated ground is an environmental hazard. Excavating
contractors or site developers, who normally move “clean dirt,” must be wary about protecting the
business from the legalities of environmental hazards. They must do everything feasible to protect
themselves from environmental entanglements. An environmental due-diligence survey should be
done. It involves three stages: (1) initial assessment (any history or current evidence of contami-
nation), then (2) investigation, and finally (3) remediation.
For instance, assume a basement is being dug in a development and an old, unknown under-
ground storage tank is broken and leaks heating oil into the ground. Who is to be blamed? As the
contractor, you may be in trouble if your only insurance is a standard, comprehensive, general liability
policy. To cover this special liability, it is necessary to have an “environmental rider” on the basic
liability policy.
In addition to adequate insurance coverage, contractors should protect themselves by asking
for phase 1 and phase 2 reports at prebid meetings. The phase 1 report involves a thorough inves-
tigation of the site’s past uses as well as uses of surrounding properties. Phase 2 details the results
of soil and water sampling at the site.
Even if the reports indicate the site has a clean bill of health, the construction contract should
have a stop-work clause—especially if excavation is involved. This allows the contractor to stop
work without penalty if potential environmental hazards are found. The contractor should then
contact the project owner, or her or his agent, and report the finding. If the owner refuses to report
a situation that poses an immediate hazard to human health or the environment, the contractor may
be bound to report the situation to the proper authorities.
Reporting environmental problems can be complicated simply because of the numerous agencies
that require notification. If a required one is missed, the fine can reach $25,000. To avoid any over-
sight, report to all possible agencies—the Environmental Protection Agency (EPA), state agencies,
fire departments, local planning commissions, the National Response Commission, and the like.
If a regulatory agency determines that the property’s contaminated soil must be cleaned, the
owner must carefully select an experienced soil remediation contractor. This is important because
the property owner is fully liable for the contractor’s actions—and penalties for bad actions start
at $10,000 per day.

Treatments. In the early days, most contaminated soil was simply dug up and hauled to a land-
fill. However, now in the United States the Environment Protection Agency (EPA) encourages
alternative treatment methods to actually clean the soil or make its contaminates less harmful.
These methods are known as soil remediation techniques. They can be classified into five general
categories: biological, physical, immobilization, chemical, and thermal.
A 1993 EPA report “Cleaning Up the Nation’s Waste Sites: Markets and Technology Trends”
gives insight into the uses of the various technologies. The technique chosen for a given site
depends on the contaminants and the site’s geology. For example, cleaning up an old gas station
may be handled best with vapor extraction if the contamination is mostly gasoline and if the soil
is not too dense. In dense soils, biomediation could be a better choice. But if heavier oils are present,
thermal desorption may be most effective.
Biological remediation (bioremediation) uses microorganisms, such as bacteria, that eat soil con-
taminants and turn them to harmless—or at least less toxic—compounds. This method is preferred
because it works in situ, i.e., is done in place. Nutrients and oxidizers are added to the soil to stim-
ulate the growth of hydrocarbon-eating bacteria. A specialized equipment system, called MecTool,
is used for in situ soil remediation and can inject microbial nutrients to depths of 100 feet.
Physical methods for remediation include such processes as drawing a vacuum through wells
drilled in the soil to pull out volatiles, or pressurizing the wells with heated air, or in situ steam
stripping, a vacuum extraction process with steam injection wells. The vapors captured in all three
processes are then treated to remove the contaminants. Another physical technique uses a water-
and-detergent solution to wash the contaminants from the soil.