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Studies

Rockbridge County – Route 11 Natural Bridge State Park

Project Photos

Project at a Glance

Locality
Rockbridge

District
Staunton

Contact
Susan Hammond, Lexington Residency
540-463-3108
Sandy Myers, Communications
540-332-9201

Overview

The Virginia Department of Conservation and Recreation and the Virginia Department of Transportation are partnering as DCR’s master plan efforts for Natural Bridge State Park move forward. Natural Bridge came under DCR management in 2016. 

Route 11 travels over the Natural Bridge geological formation. VDOT is responsible for the maintenance of the Route 11 road surface and roadbed. Route 11 at this location is not considered by modern standards to be on a bridge. Instead Route 11 sits on a geological formation made of limestone. This type of rock material is common throughout the Shenandoah Valley and results in karst features, like sinkholes and caves.

DCR manages the park and its assets including the Natural Bridge geological formation. Both DCR and VDOT are committed to preserving the formation for current and future generations and are working together toward this goal. 

As a partner in the master planning process VDOT has provided resources and expertise for a geological analysis of Natural Bridge. VDOT is also conducting a transportation and mobility study on Route 11.

VDOT and DCR will use the data and reports as a basis for working together to establish a long-range plan for the preservation of Natural Bridge. Route 11 will continue to be located on the Natural Bridge structure during the master planning process. To date, no data have emerged indicating the road is unsafe for traffic. Efforts will continue to preserve the Natural Bridge geological formation for current and future generations to enjoy.

Geological Studies

Please click here for: Final report-Natural Bridge Investigation

Prior to summer 2017 the Natural Bridge geological formation was not inspected by VDOT. In the late 1990s VDOT performed a limited inspection along with another private study done for the owner of Natural Bridge at that time.

To assist DCR with its master planning work, VDOT engineers and geologists began a series of non-destructive geological tests that were completed in January 2018. A written analysis was part of this work. VDOT contracted testing services through an agreement between the Virginia Transportation Research Council in Charlottesville and Radford University. The testing was led by Dr. Chester (Skip) Watts of the Environmental and Engineering Geosciences Program at the Department of Geology at Radford University. Dr. Watts specializes in engineering geology and is a Certified Professional Geologist in the Commonwealth of Virginia. Dr. Watts is the past Dalton Distinguished Professor of Geology at Radford University and now heads the Geohazards Research Center.

Below is a listing of each test, type of data collected and data purpose. This material was reviewed by an advisory board whose members are independent of DCR and VDOT. At the conclusion of all testing, the final report was produced in spring 2018.

Ground Penetrating Radar (GPR)
LiDAR surveys
Unmanned Aerial System Surveys
Resistivity
Seismic Reflection or Refraction
Gigapan
Vibration monitoring, geophones, or other monitoring tools
Other methods as deemed necessary

Ground Penetrating Radar (GPR)
When: July 2017
Data Type: Electromagnetic waves in the radio spectrum in the microwave spectrum. Air-Coupled Radar and Ground-Coupled Radar
Data Purpose: This non-destructive test provides 2D imaging of existing roadway layers.

Terrestrial Light Detection and Ranging (LiDAR)
When: August and October 2017
Data Type: 3D laser surveying (high resolution 3D digital models from the ground below the rock arch) 
Data Purpose: The LIDAR surveys provide a three dimensional representation of the geological formation’s surface features.

Unmanned Aerial System Surveys
When: November 2017
Data Type: Digital Photogrammetry (high resolution photographs).  Photography from unmanned aerial vehicles (UAV).
Data Purpose: Provides visual surface photographs and enhances surface mapping, and can be used to build 3-dimensional computer models of the rock structure. Complements the LiDAR survey data.

Electrical Resistivity
When: October 2017
Data Type: 2D imaging of rock formation subsurface
Data Purpose: This test will lay wires across the road surface. Small electrical pulses travel through the rock formation and are measured at various locations. The measured resistivity of the material at various depths provides an indication of the material type (rock, sand, air) and water content. These data provides a 2-D image of the formation subsurface for use in later analyses.

Seismic Reflection or Refraction
When: October 2017
Data Type: Refraction seismology (or seismic reflection) is a method of non-destructive exploration geophysics that uses the principles of seismology to estimate the properties of the Earth's subsurface from refracted seismic waves. A hammer device will be used to strike the ground and measure seismic response.
Data Purpose: These tests help measure the density of rock and how sensitive the rock is to vibration.  This test will help add engineering properties to the structural map of the rock.

GigaPan
When: Fall 2017
Data Type: GigaPan uses very high-quality digital images to investigate the surface of the rock.
Data Purpose: These images reveal aspects of the rock surface that may reveal the underlying structure and may not be immediately visible from ground vantage points.

Vibration monitoring, geophones, or other monitoring tools
When: November 2017
Data Type: Geophones are small seismic sensors that will be placed in a pattern across the ground at various locations or on the geological formation itself. Geophones convert ground motion into analog electrical signals displayed as wavy lines (ground vibrations)..
Data Purpose The geophones measure ground movement, such as vibration from an external source.

Transportation Studies

Route 11 Alignment Study at Natural Bridge

The Virginia Department of Transportation is conducting an alignment study for Route 11 (Lee Highway) in the Natural Bridge area of Rockbridge County. During 2018 VDOT is examining a 5.5-mile segment of Route 11 between Interstate 81 exit 175 (Natural Bridge) and exit 180 (Fancy Hill). Michael Baker International will conduct this study under a contract with VDOT.

The study is a preliminary location review of Route 11. Several possible alignments for portions of Route 11 is part of this work. If a future realignment of Route 11 is recommended, an additional location study including a no-build option is required before any right of way work or construction work is done to move any part of Route 11.

The Route 11 alignment study will inventory road-related features in the corridor plus document existing conditions and deficiencies. Existing accident data, operational analysis/congestion areas, environmental constraints and cost will be investigated. Ground and aerial survey work was conducted in late winter and early spring 2018.

Once the information is collected, a Citizen Information Meeting will be held in the community in fall 2018 to discuss the options and determine the need and scope of potential improvements including potential alignment alternatives.

Route 11 is a primary road used for local and through traffic. It is also used as a detour alternative for I-81 traffic when crashes close all northbound and/or southbound lanes in this area. Other detour routes can take up to 90 minutes or more to travel. Route 11 travels through Natural Bridge State Park and a portion of it lies on the Natural Bridge geological formation.

Study results will be provided to Rockbridge County for future planning and to the Virginia Department of Conservation and Recreation for its Natural Bridge State Park master planning work. Route 11 will maintain its current location within the park during the master planning process.

Public Event

Route 11 Natural Bridge Alternatives Study
Citizen Information Meeting

Tuesday, October 30, 2018, 5-7 p.m.

Natural Bridge Hotel & Conference Center
15 Appledore Lane
Natural Bridge, VA 24578

Technical Advisory Panel for the Natural Bridge Geological Investigation Project

An advisory committee of prominent geologists in the United States and Canada reviewed all geological testing results from 2017, testing summaries and conclusions and issued an independent report. 

Dr. Tony Szwilski, Ph.D., P.E. Huntington, WV
Director of the Center for Environmental, Geotechnical and Applied Sciences (CEGAS)

Dr. Thomas M. Murray, Ph.D. Blacksburg, VA
Professor Emeritus, Virginia Polytechnic University

Dr. Abdul Shakoor, Ph.D. Kent, OH
Professor Emeritus, Kent State University

Dr. Edward J. Hoppe, Charlottesville, VA
Associate Principal Research Scientist, Virginia Transportation Research Council

Mr. David Spears, Charlottesville, VA
State Geologist for the Commonwealth of Virginia

News Media Events

Natural Bridge Lidar Testing - Media Availability
Wednesday, August 16, 2017, 9:30 a.m.
Natural Bridge State Park Visitors Center, 6477 South Lee Highway, Natural Bridge, VA 24578 

Natural Bridge Geological Testing - Media Availability
Tuesday, October 3, 2017, 10:00 a.m.
Natural Bridge State Park Visitors Center, 6477 South Lee Highway, Natural Bridge, VA 24578

Natural Bridge Geological Testing - Media Availability
Tuesday, January 23, 2018, 10:00 a.m.
Natural Bridge State Park Visitors Center, 6477 South Lee Highway, Natural Bridge, VA 24578

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Page last modified: Oct. 9, 2018