NC Mountain to Sea Trail
The North Carolina Mountains-to-Sea Trail (MST Trail) is a 1,150-mile hiking trail that stretches from the Great Smoky Mountains to the Outer Banks. The trail starts at Clingman’s Dome (the highest point in Tennessee and the Great Smoky Mountains National Park), travels over Mount Mitchell (the highest mountain in the Appalachian chain), and through Jockey’s Ridge State Park (the highest sand dune on the East Coast). Along the way, the trail goes through three national parks, two national wildlife refuges, three national forests, seven state parks, and two lighthouses (one of which is the nation’s tallest).
The trail may be enjoyed in different ways. Through-hiking (attempting to hike the entire length) is possible and has been done, but most choose to enjoy segments of the trail, particularly those closest to home. For those of us in the Greensboro area, Section 24 of the MST Trail (known as Greensboro Lakes) is about 21 miles long. This section comprises a network of interconnected trails that trace the outline of two of Greensboro’s municipal water reservoirs. The section extends from U.S. 220 near Bur-Mil Park east to Bryan Park. Section 24 is described in detail here.
Friends of the MST Trail (FMST) are putting together a trail guide of the entire trail, and the first segment (Peak to Peak – Clingmans Dome to Waterrock Knob) is now available. Additionally, an interactive map combines satellite imagery, route information, and updates and photos to allow you to plan your hike accordingly.
The Mountains-to-Sea Trail depends largely on communities, volunteers, and donations to build and maintain this North Carolina treasure. Visit www.ncmst.org to see how you can help.
Using Geophysical Methods to Explore Sinkholes in Tennessee
In January 2015, Pyramid Environmental conducted a geophysical investigation at an open sinkhole (ground collapse) in a dry retention pond for a client at their remediation site in Tennessee. The survey was conducted to determine the lateral and vertical extent of the sinkhole feature in the subsurface, and to evaluate the average depth to bedrock in the surrounding area within the pond. The investigation consisted of Multi-Electrode Electrical Resistivity (MER) testing at nine locations across the property, shown in the figure below.
The resistivity data provided a reliable representation of the geologic conditions within the upper 50 feet of the subsurface at the property. Geologic conditions generally were characterized by a stratum of dry surface clayey soils underlain by saturated clayey soils that were further underlain by limestone bedrock. The survey indicated an average depth to bedrock of approximately 27 feet below the pond bottom. In five of the resistivity profiles surrounding the area of ground collapse, a clear break in the zone of saturated clayey soils was observed. The break is interpreted to represent sandy in-filled soils with increased porosity, resulting in the downward movement of soil and water, ultimately causing the ground collapse. The figure below is a 2D resistivity profile, showing the general conditions encountered around the sinkhole.
A second area of concern was identified to the northwest of the visible ground collapse. The nature of the soils in this area suggests they may also potentially result in a ground collapse in the future. 3D imaging of the two areas of concern provides further evidence of in-filled sandy soils that are “raveling” downward into the underlying rock unit and causing unstable conditions. Raveling is the process by which water transports soil particles downward into cavities in the underlying strata. The figure below is a 3D resistivity rendering, which shows the zones of in-filled, collapsing soils associated with the sinkhole and the second area of concern.
Surveys such as these are invaluable planning tools that help identify and delineate subsurface hazards. Based upon the results of the geophysical data, Pyramid’s client is now able to make informed decisions about the current and future use of the property surrounding their remediation site.
