(This first appeared in the Wyoming Livestock Roundup in November, 2014)
Oil and gas production is on the rise in eastern Wyoming. Technological advances in exploration and extraction, like fracking and horizontal drilling are opening up large new reservoirs in places that haven’t boomed in over 20 years, or that never boomed before. A large part of my job as the University of Wyoming soils extension specialist involves research and education on the best ways to restore soils disturbed during extraction activities. In much of Wyoming that involves working with federal agencies and energy companies to develop new and better ways to restore the fragile productivity of arid rangelands.
But most of the land surface in eastern Wyoming is privately owned, and landowners can profit from leasing surface rights to drilling companies. But without careful planning for reclamation, long-term sustainability of farms and ranches can be threatened. Disturbance that comes with well pads, access roads, and pipelines is often difficult to repair, and recovering forage production, wildlife habitat, and soil water storage can be a long and difficult process that, if not done correctly, is too often unsuccessful.
Lease agreements should contain clear and complete final reclamation standards, but that is not always enough. Successful reclamation results from carrying out several steps, starting before a blade ever hits the ground. Stipulating proper procedures before, during, and after construction can prevent failure. This article discusses critical components that should be clearly described in reclamation plans and included in oil and gas development lease agreements.
A predisturbance or baseline inventory provides information on general characteristics of a site from both existing information like the soil survey, and on-site evaluation of wildlife habitat and use, forage production, water quality protection, aesthetics, and other qualities, as well as specific soil, vegetation, and landscape characteristics. The inventory establishes a framework for post-reclamation monitoring and evaluation.
Topsoil stripping should carefully follow the predisturbance plan, with operators carefully salvaging only the best soil, which is often very shallow in Wyoming. Stripping too deeply mixes topsoil with salty, clayey, or rocky subsoils and reduces the reclamation potential. Stripping depth should vary with the depth of the soil across a site as indicated in the predisturbance inventory. This requires a skilled equipment operator trained to visually recognize the correct depth. Stripping depth should be marked with stakes. Lower slopes and swales usually have deeper soils while upper slopes, knolls, and ridge tops have shallower soils. Eroded sites may have no salvageable topsoil.
In the cool, dry environment of Wyoming, stockpiling topsoil deeply and for relatively long periods is not as detrimental to the quality of the soil as moving it. While the initial disturbance accelerates decomposition and causes loss of soil organic matter, once in a pile, dry soils are essentially in cold storage and don’t change much until moved again. Stockpiles should be seeded and protected from erosion by constructing silt fences or using straw bales, trenches, or other erosion-control practices around them as soon as possible.
Backfilling with subsoil and underlying materials and grading to the original topography, along with reestablishing drainage properties, set the stage for successful reclamationKeeping slopes less than 3:1, or 33-percent gradient, minimizes erosion after reclamation. Surface drainage patterns should be rebuilt to reestablish essential hydrologic functions and minimize erosion.
Before topsoil is respread on the graded surface, sites should be deep ripped to reduce compaction of the subsoil/ underlying material to appropriate rooting depth (at least 12 to 18 inches deep). Ripping soils allows for greater water infiltration, greater aeration of the soil. The most common primary tillage practices prior to spreading topsoil are deep ripping, deep chisel plowing, deep disking, and scarifying on the contour to control erosion.
After working the graded area, topsoil should be respread to depths consistent with the original depths. Topsoil should be chiseled, disked, and firmed with, a roller harrow on the contour to control erosion and prepare a proper seedbed. If results of predisturbance soil analyses are not available, test soils for nutrient content and salinity after spreading and use the typical productivity as the yield goal. This prevents unnecessary amendment application or over-fertilization.
Seeding technique and equipment depends upon seed size, which determines the proper depth of seeding and the seeding rate for each. When seeding grasses with a seed drill, 20 seeds per square foot is a sufficient rate; however, when the mix contains grasses, shrubs, and forbs, a better rate is 50-100 seeds per square foot (usually 10-16 pounds per acre). Large-seeded species are typically planted with a grass-seed drill while small-seeded, fluffy species should be planted with a broadcast seeder. Ideally, one seed mix should be designed for drilling and another for broadcasting.
Seeding time is crucial and, for Wyoming, reclamation seed mixes should usually be seeded in the fall after the soil temperature is around 40°F but before ground freezes (typically after October 15). Most native species need to be planted in the fall to break dormancy. Seeding times may vary by year and region within Wyoming. A spring seeding prior to April 15 may work in eastern Wyoming, where annual rainfall is over 15 inches and spring and early summer precipitation is fairly reliable.
Developing and following a long-term monitoring plan is crucial so problems can be identified and controlled early. Close attention should be paid to seeding success, noxious weeds, and erosion. Establishing a seeded plant community in Wyoming often takes three to four years and some shrubs may take that long just to germinate.
For more detailed information on key components for successful reclamation that should be included in oil and gas lease agreements, please see the University of Wyoming reclamation extension bulletin series on line at http://www.uwyo.edu/wrrc/bulletins.html, especially bulletin number B-1242, Reclamation Considerations for Oil and Gas Lease Contracts on Private Land.