Preserving the Blue Ridge Parkway

Maintaining one of the most beautiful roads in the world requires not only competent technical skills, but an appreciation for the safety of the visiting public and the preservation of the precious resources they travel miles to experience.

  

By Cdr. Nathan Epling, P.E., BCEE, M.SAME, USPHS

 


 

Considered one of the most scenic drives in the world, the Blue Ridge Parkway stretches along 469-mi through the moun­tains of Virginia and North Carolina. The nostalgic two-lane road entreats visitors to slow down and enjoy the lazy curves, rock guardwalls, stone waterways, grassy bays and its signature vistas.

Few visitors, however, may realize the extent to which over the years engineers have worked throughout the parkway to ensure an experience that is safe for them and the environment.

As a U.S. Public Health Service engineer officer arriving nine years ago, I did not expect the level of effort necessary for the parkway to provide clean, safe drinking water; treat and dispose of wastewater; and minimize the impact of construction in protected areas. The parkway operates several visitor contact stations, camp­grounds, restaurants, lodges and offices for staff, visitors and volunteers. Sites along the road may have thousands of visitors in a day. Children and elderly, being more vulnerable to disease, make up a significant proportion of the visitation. Keeping the public safe from disease is a top priority.

Blue Ridge Parkway

 

UNDERSTANDING THE MISSION

As far back as 1918, when the U.S. National Park Service first requested a U.S. Public Health Service officer (an engineer) to support the parkway, leader­ship understood it would not survive if visitors departed with serious sickness or injury.

Similarly, any park development could not mar the very scenic beauty that drew people to the area in the first place. Our pride in national parks, including the Blue Ridge Parkway, is in large measure a result of engineers and designers learning to work within many unique environments and bring generations of visitors safely in touch with our natural wonders.

 

DRINKING WATER SYSTEMS

Since its inception, the parkway had relied on spring developments as the primary source for water in remote areas. In the 1980s, to better comply with Safe Drinking Water Act requirements, the parkway converted its multitude of spring-based water supplies to groundwater wells. The addition of chlorine for disinfection also presents challenges as deep aquifer water chemistry is not always suitable for monitoring residuals (water hardness can react with the free chlorine normally measured to ensure proper disinfection). While alternative disinfection methods have been considered, chlorine is the most reliable and least operationally demanding.

Underground concrete reservoirs, some designed in the late 1930s, are found on the top of hillsides to gravitationally flow water to buildings and hydrants. These tanks range from 10,000-gal to 225,000-gal and are often divided with an interior baffle to reserve half the water for emergencies. With modern confined space regulations, staff now relies on contractors to perform tank cleaning and inspections (a cost not considered when originally designed).

Most of these systems are drained when the camping season ends in November and restarted and tested in the spring. This prevents shallow parts of the distri­bution pipes from freezing in the frigid mountain winters. Ideally dug below frost depths, many pipe trenches encountered granite and were not placed at the design depth. Realigning water pipes for depth or other operational benefits has the added complexity of natural and cultural resource preservation. To minimize removal of trees and other sensitive vegetation, and poten­tial archaeological resources, water lines are generally kept to existing alignments.

 

POWER AND COMMUNICATION

Power and communication are trouble­some operational issues. Severe thunder­storms are common throughout the open season. They wreak havoc on end-line, rural electric infrastructure. Float systems are often zapped by storms, resulting in pumps not operating when tank levels are low. Radio communications using solar power have helped create more reliability, unless they also take a direct hit by lightning.

The parkway is looking in to pressure sensing technologies that may prove more reliable. In places without nearby electric lines, diesel generators powered deep well pumps. However, as solar technology has progressed, diesel systems are being replaced with quiet, more automated technologies.

Linn Cove Viaduct 

LINN COVE VIADUCT

Throughout its first 50 years of construction, the Blue Ridge Parkway blasted, graded and tunneled its path through the Appalachian Mountains. In the 1970s, as designers began to consider the last and most difficult segment of road to finally complete all 469-mi they made arguably the project’s most significant environ­mental decision.

As they considered the cost to the pristine natural resources found in a spot called Linn Cove in North Carolina that a road or tunnel would require, they elected for a more sensitive path—a decision, however, that would demand a highly complex engineering feat, ultimately result­ing in what is regarded as the most complicated concrete bridge every built. The Linn Cove Viaduct, a bridge of precast segments elevated on seven piers, hovers just above jutting rocks and uneasy vegetation 4,100-ft above sea level, curving along contour and matching grade at both ends. Construction began in 1979, finishing in 1987 at a total cost of $10 million.

At 1,243-ft long, the viaduct acts as a monument for environmental preservation that not only parkway engineers are challenged to meet, but we as Americans can take pride in and seek to surpass as our civi­lization continues to balance our needs with those of a sustainable and inspirational environment.

 

WASTEWATER CHALLENGES

The most problematic environmental engineering challenge over the past couple of decades has been onsite wastewater. As systems that were built over half a century ago finally start to show symptoms of fail­ure, parkway engineers are confronted by considerable constraints not anticipated by the original planners.
 


 

Technological innovations within the last 10 years have brought a number of new opportunities for engineers to improve the parkway’s onsite wastewater treatment and disposal operations.


 

Where a modern residence may require a reserve drainfield area for future use, no such consideration was made in the camp­grounds and picnic areas where every inch was planted, paved or otherwise prepared for an RV or tent camper. Many systems, due perhaps to seasonal use and remark­able designs (drainfield lines were made of corrugated pipe cut lengthwise and set similar to today’s “chambered” drainfields), have lasted well beyond the design lifecycles we use currently. These camp sites have literally “grown up” in planned vegetation precious to the scenery visitors expect. More remote but open areas considered for onsite wastewater disposal often add archeological limitations that further constrain design. The smallest system with minimal impact to resources, including operations, is preferred.

Textile Media TreatmentOver its first 60 years, the parkway employed many technologies to handle these restrictions—Imhoff tanks, spray fields (in wooded areas), automatic siphon dosing pumps, seepage beds, even septic tanks with drain valves, presumably to empty contents into less visited areas off season. All of these had varying levels of success and sustainability, and were prob­ably quite innovative for their time.

Technological innovations within the last 10 years have brought a number of new opportunities for engineers to improve the parkway’s onsite wastewater treatment and disposal operations.

  • Textile Media Treatment—minimized noise disturbance and maintenance burden.
  • Attached-Growth Media Treatment— reduced restaurant waste strength for onsite disposal.
  • Standard Drip Drainfield—minimized tree removal and grading to protect forested area and trails.
  • Anaerobic Drip Drainfield—mini­mized treatment needed in remote area; preserved popular field for visitor recreation.
  • Septic Tank Effluent Pumping— preserved 50-year growth vegetation around campground sites.
  • Solar Powered Dosing Tanks—elimi­nated drainfield near stream; preserved sites in heavily used picnic area.

  

LOOKING AHEAD

These advancements are enabling the parkway to meet or exceed current onsite wastewater regulations while preserving the resources enjoyed by visitors. As engineers continue to strive for greater sustainability, technologies are chosen that do not over­burden operators, require excessive energy, or create undue waste.

Parkway staff will watch closely the performance of these systems over the next decade—improving and expanding their use as needed to protect finite resources.

  


 

Cdr. Nathan Epling, P.E., BCEE, M.SAME, USPHS, is Civil Engineer, Blue Ridge Parkway, U.S. National Park Service; 828-348-3481, or This email address is being protected from spambots. You need JavaScript enabled to view it." target="_blank">This email address is being protected from spambots. You need JavaScript enabled to view it..