September 2001 AGGMAN Geology

September 2001

Geology

“Solum Certum Nihil Esse Certi” Pliny, the elder, Historia Naturalis

By William H. Langer

Editor’s Note: This article is the ninth in a 12-part series focusing on how geology can lessen the “surprises” and help overcome the challenges posed by nature during the process of aggregates extraction.

During 79 A.D., Pliny, the elder, visited Mt. Vesuvius. It was erupting, and Pliny wanted to demonstrate to the populace that there was nothing to fear. Unfortunately, he was wrong. He was overcome by fumes from the volcano and died.
Why would I use a quote from Pliny as a title for this article? Because this article is about environmental risk. “Solum certum nihil esse certi” translates to “The only certainty is uncertainty.” And uncertainty creates risk. Had Pliny known for sure that he would be killed when he visited Mt. Vesuvius, there would have been no risk—just a certainty. However, he did not know for certain the outcome of his actions, and his unfortunate error in risk analysis resulted in his untimely demise.
Risk analysis is over 5,000 years old. In the Tigris-Euphrates valley, around 3,200 B.C., a group called Asipu served as risk analysis consultants for people making risky or uncertain decisions. Around 1950 B.C., The Code of Hammurabi formalized contracts that contained a risk premium covering the loss of ships and cargo. Modern risk management concepts are applied to hazards to humans that are created by humans—such as dam failures, nuclear power plant failures and traffic accidents; and hazards to humans that are created by nature—such as lightning strikes, earthquakes, floods, landslides and diseases. Recently, the concept of risk management has also been applied to hazards to nature that are created by humans, such as the risk of human activities polluting the water, impacting natural areas or harming wildlife.
The aggregate industry is an extractive industry and aggregate resources cannot be obtained from the landscape without causing some environmental impacts. We know with certainty what some of those impacts will be (such as noise and dust), and we can take measures to control those impacts and restrict them to tolerable limits.
There is uncertainty with other impacts. By its very nature, aggregate extraction involves development in three dimensions—we cannot completely characterize what is below the land surface, and there is always some degree of uncertainty about the type and extent of adverse impacts that could arise.
Some potential environmental impacts are not obvious, particularly in geologic environments, such as active stream channels, slide-prone areas and karst, which are dynamic and respond rapidly to outside stimuli. In these environments, aggregate mining may alter sensitive parts of the natural system at or near the site, thus creating cascading environmental impacts. For example, aggregate mining in some karst might lower the water table, which will remove the buoyant support from soil that overlies water-filled caverns or other solution features, which might result in land collapse, which will create a sinkhole.
To further complicate matters, the physical, biological and cultural characteristics of an area impacted by or impacting an aggregate operation are in a constant state of change, and those changes can modify the environmental impacts of mining. For example, an environmentally sound crushed stone operation in a karst area could start causing damage to the environment if the nearby ground-water system is modified by natural conditions (such as a prolonged drought) or by human activity (such as increased ground-water withdrawal by a nearby water-well field). Our inability to completely understand complex natural systems and the difficulty associated with possible changes over time introduces uncertainty, and uncertainty creates environmental risk.
An environmental risk describes the consequences of a natural or human action and the likelihood that those consequences will become real. Consequences commonly are considered to be adverse affects. An initiating event is an event that triggers the environmental impact, making the consequences become real. Environmental risks can be real or perceived. Even if environmental risks are real, the initiating event may never take place during the period of risk, resulting in no adverse environmental consequences. The issue is “Can risks be identified and successfully managed?”
A number of factors go into managing environmental risks from extracting aggregate. Permits, regulations and requirements, and enforcement of those regulations and requirements play major roles in preventing common environmental risks. Economics and the desire for safe operations are also strong incentives for environmental compliance. Even with no incentives, an operation can work without causing any serious environmental problems purely by the chance of good fortune.
But good fortune did not work for Pliny and may not work for aggregate producers. Environmental risk analysis has a vital role to play in protecting the environment from the impacts of mining and is a valuable tool that the aggregate industry can use to demonstrate that it can manage environmental issues to produce acceptable levels of environmental protection. The article next month will describe the risk analysis process and how to apply it to the aggregate industry.

William H. Langer is a geologist with the Mineral Resources Team of the U.S. Geological Survey.