William D. Balgord: Sand mining operations are often misunderstood by critics
A fundamental transformation is underway in U.S. oil and gas production.
Hydraulic fracturing, known also as "fracking," combined with horizontal drilling in oil-rich shales promises a secure energy future. But fracking runs afoul of President Barack Obama's plan to phase out carbon-based energy (starting with coal) in pursuit of lowering carbon dioxide emissions.
Fracking involves injecting (under pressure) slurry, consisting of sand mixed with water and dispersants into oil-bearing geological formations. The slurry forces apart thin layers of clay in a rock matrix. As pressure is released, sand grains remain behind, propping open the layers and allowing freed oil to be pumped to the surface.
To date, fracking is done in North Dakota, Montana, Texas, Oklahoma, Pennsylvania and West Virginia.
Sand preferred for fracking has particle size, shape (rounded grains) and composition tailored to specific shale formations. The best comes from sand-stones in western Wisconsin, Minnesota and Iowa that once formed along beaches during the Cambrian Period a half billion years ago.
Until recently, mining operations expanded rapidly but slowed with sagging oil prices. Demand for sand will rebound strongly once prices recover and drilling resumes possibly next year. Yet, confusion surrounds sand mining.
Sand mining draws strong opposition from environmentalists spreading false fears to convince local governments to prohibit mining within their jurisdictions.
Claims of contamination of wells, alteration of streams and lakes, drying of wetlands and destabilizing the ground near the mines are made. There is no substance behind speculation that removing sand from shallow deposits will cause earthquakes. Never has there been an earthquake near a sand mine. In the seismically stable upper Midwest, earthquakes are extremely rare.
Sand, limestone and granite quarrying dates back 200 years in U.S. history. Earthquakes are not associated with these activities despite what I have heard from some local residents.
Minnesota Department of Natural Resources regulations protect lands, the air and waterways within the state. Mine operators must submit detailed plans before projects are approved. As each successive stage is completed, the affected property must be restored to forest, agriculture or parkland.
Another issue arises in regard to whether sand mining would elevate airborne silica affecting persons living nearby. It's worth noting that Mine Safety and Health Administration regulations strictly limit onsite exposure to silica. Silica dust must remain within safe limits at all outdoor locations extending to plant boundaries and beyond.
At a Minnesota sand mine, air samples taken upwind and downwind revealed no increases of airborne silica originating from the plant. Researchers attributed occasional tiny amounts found upwind to nearby agricultural operations and unpaved roads in the area or to distant sources, such as the U.S. and Mexican deserts to the southwest.
Yet another issue has been the use of the flocculent, polyacrylamide, to remove clay and silt from process water. The chemical quickly degrades to innocuous by-products and doesn't persist long enough to find its way to area wells. The same flocculent, administered at higher levels, is used for clarification at municipal plants that supply the drinking water to millions around the United States.
Note the water used in sand plants is recycled with minor evaporation losses made up from wells onsite.
Water drawn from Minnesota's abundant resources for future operations is projected to fall well below consumption levels in the agriculture sector and other industries in the state. Consumption is far less than levels consumed by municipalities.
Except for increased truck traffic, few advertised risks from sand mining turn out to be credible. Processed sand is loaded into sealed rail cars destined for the oil fields or to loading facilities along the Mississippi River. From there, sand travels by barges to the Gulf Coast.
Like other enterprises, sand mines provide high-paying jobs in both Minnesota and Wisconsin counties where the median-wage scales tend to fall below the states' averages. Sand-mining operations contribute tax revenues to state, county and municipal governments.
William D. Balgord has a doctorate in geochemistry and heads Environmental & Resources Technology Inc. in Middleton, Wis.