Contacts
 



Keyword Site Search







A New Standard for

Yosemite National Park

by James R. Benya, PE, FIES, IALD, LC

Principal, Benya Lighting Design

As we think about how to design in the early 21st Century, environmentalism and sustainability are key concepts. Not only do we face the prospect of more people and more development, but also with them comes increased per capita consumption of natural resources. You don't need to be a tree hugger to understand the imminent threat of pollution as you look at the air in major cities throughout the world.

This struggle between mankind and nature is most evident in the US National Parks like Yosemite. All forms of development conflict with the purpose of the Park, which is to preserve the wilderness. But in order to meet the demands of visitors, a certain amount of development must occur. The US National Park Service (NPS) is constantly challenged to find the proper balance in every national park. From NPS Management Policies. Chapter 4:

"The National Park Service will cooperate with park neighbors and local government agencies to seek to minimize the intrusion of artificial (sic) light into the night scene in parks with natural dark, recognizing the part that darkness and night sky play in the overall visitor experience. In natural areas, artificial (sic) outdoor lighting will be limited to basic safety requirements and will be shielded when possible."

Electric lighting can be considered one of the more invasive and unnatural elements of civilization. In the dead of night in Yosemite Valley, even a 100-watt lamp is a beacon. Without lights, the visitor can enjoy the stars and the majesty of the valley illuminated by starlight. However, unless there is some lighting, the problems of modern society create liabilities and threaten the comfort of park visitors.

NPS and Yosemite Concession Services (YCS) retained architects Esherick Homsey Dodge and Davis and my firm to identify the issues and find solutions. Working with Bill Rust of NPS, we were empowered to consider any and all measures before developing a lighting "master plan" that would guide projects from all architects and landscape architects into the future. To demonstrate its techniques and viability, several current projects permitted us to apply the plan immediately.

Existing Conditions

First, the project examined the existing lighting throughout the Valley and in Wawona. In general, there was very little general lighting, and fortunately, no street lighting or other major lighting system. Most of the lighting systems were in the vicinity of the developments.

The most offensive lighting in the Valley was at the gas station near Yosemite Lodge. The design of the gas station was similar to most, having a canopy with high-wattage metal halide luminaires generating 50 foot-candles at the pump. Worse, the drop lens lights generated tremendous amounts of light pollution and light trespass. Coincidentally, the threat of environmental damage from gasoline tanks was even worse, and the gas station was decommissioned during the project.

Canned soda machines were the most widely distributed sources of offensive light found in the park. Each machine was estimated to generate about 5% of the light pollution and trespass of the gas station. In addition, the lighting for each machine consumes 2,000 kWh per year, costing nearly $200.

The balance of the lighting found in the park was a variety of relatively ordinary equipment, although wear was showing on older lighting systems. Lighting levels throughout the park were generally quite low, if there was any lighting at all. But other than the soda machines and gas station, the only other existing lighting problems were generally caused by ordinary lighting equipment that should have been better shielded to prevent light trespass and light pollution.

Lighting and Liability

The team's first concern was for the safety and security of Park employees and visitors. This was immediately expanded to include universal accessibility. Lighting is generally understood to play a primary role in all three concerns. From the NPS Management Guidelines:

"The saving of human life will take precedence over all other management activities. The National Park Service and its concessionaires, contractors and cooperators will seek to provide a safe and healthful environment for visitors and employees.."

However, NPS and YCS are constantly challenged to choose between nature and civilization. It is not possible to have a natural mountainous environment that is well lighted at night and provides universal accessibility. So to a certain extent, the NPS Management Guidelines acknowledge that, at some point, the forces of nature will prevail:

"However, park visitors assume a certain degree of risk and responsibility for their own safety when visiting areas that are managed and maintained as natural, cultural, or recreational environments. The NPS recognizes the environment being preserved is a visitor attraction but that it also may be potentially hazardous."

To help distinguish where electric lighting was needed, the team embraced NPS terminology of "frontcountry" and "backcountry". Frontcountry was redefined to mean the developed area of the park, immediately accessible by auto or park bus and sufficiently developed to attract visitors having a wide range of ages and access capabilities. Backcountry was redefined to mean the majority of the Park, including campgrounds, vista points, and other locations where preserving nature clearly took precedence over the broad range of human needs. The team determined that frontcountry areas should be lighted for safety, security and accessibility. Backcountry areas might have electric lighting, but only as determined on a case-by-case basis by NPS. At Yosemite, most of the front country areas are on the Valley Floor, associated with the Awahnee, Yosemite Lodge, Curry or Yosemite Village.

 Yosemite has long been a favorite place for visitors from around the world. The natural beauty (bottom) has made it one of the most photographed places in America. As part of the lighting design, luminaires (Left) were mounted to a post.

How Much Light?

Standards of the Illuminating Engineering Society of North America (IES) are generally used to establish exterior lighting levels. However, IESNA standards are based on lighting in civilization and do not address the unique lighting requirements of a National Park. A reasonable compromise, even in the frontcountry areas of the Park, needed to be set. After considerable deliberation and the review of measurements taken at key locations in the Park, the team agreed to a table of light level recommendations that addressed IESNA standards. For lighting situations considered most critical, the lowest published IESNA standard was selected, but for less critical areas, lighting levels less than IESNA recommendations were adopted. This critical step, taken carefully and in consideration of environmental lighting principles (now published as IESNA RP-33, Exterior Environmental Lighting) made it possible to envision a lighting plan adequate to the task but not a bit more light than necessary.

Light Trespass and Light Pollution

Light trespass and light pollution are, unfortunately, common conditions of electric lighting. Light trespass occurs when light intended to illuminate one area is carelessly allowed to illuminate other areas nearby. Light pollution occurs when stray light is emitted upwards, illuminating clouds, dust and other airborne matter and obscuring the night sky. It can also illuminate tree crowns in a forest setting, detracting from the natural setting.

The International Dark-Sky Association (IDA) is a non-profit group whose mission is to minimize or eliminate light pollution. IDA recommendations are reflected in IESNA RP-33, although there are important differences. The IDA has historically recommended low-pressure sodium light sources, which in turn permit astronomy with filters to remove yellow light and increase visibility of the balance of the spectrum. However, numerous recent IESNA papers show an increasing concern over human visibility with spectrally deficient light sources at low light levels. White light sources were chosen instead. The design team recognized that to prevent both light pollution and light trespass, the most important thing was to control light and cast light mostly downward from any luminaire. As a secondary guard, power limits were set on all lamp types to minimize inadvertent light trespass or pollution by using wasteful high-wattage lighting practices.

 The crook-arm, bell shaped pole lights (left) used at the Park have sharp cutoff optics and flat lenses. The poles blend into the backdrop of the forest and rustice building (bottom) styles.

Source Options

Operating costs of a lighting system include energy efficiency, relamping costs, and periodic replacement of parts like ballasts. Most of the time energy efficiency is the largest single cost item. From a practical standpoint, though, lamp life is a key concern because to maintain a lighting system at low light levels, there is no redundancy and all lamps need to be operating. Spot relamping costs are much higher than other means of changing lamps.

The need for relatively small amounts of light caused the design team to turn to compact fluorescent lamps to play a significant role. Historically, fluorescent lamps were too large to use in many outdoor applications, and early compact fluorescent lamps would not start reliably unless the outdoor temperature was at least 32 F. New triple-tube compact lamps using amalgam technology and electronic ballasts can start at temperatures as low as -15 F. To minimize lamp choices for stocking and management purposes, 26 watt lamps were ultimately chosen for a number of different lighting applications.

The balance of the working lamp stock was determined to permit present and future lighting designers to meet the demands of the various frontcountry facilities. For parking lot lights and similar locations typically needing a lot of light, the program permits metal halide lamps up to 100 watts. Compared to the 175-1000 watt lamps used in urban and suburban parking lots, this relatively low lamp wattage helps minimize the possibility of lights being too bright or creating light trespass and light pollution. For landscape lighting and other delicate applications, the team decided it would be reasonable to permit a few halogen lamps such as PAR38 and MR16. Spectrally deficient lamps like high-pressure sodium and low-pressure sodium were eliminated from further consideration.

"Appropriateness"

After all the standards are set and research done, there remains the application of lighting to the actual buildings and developed areas of the park. As with any project, the daytime appearance of the lighting equipment must work within the (mostly) rustic and eclectic architecture of the Park.

The design team identified a number of criteria upon which to base lighting selections: Form often follows function, so a number of luminaire styles will be needed for various applications; Energy efficient light sources generally require ballasts that must be located within the luminaire housing; Modern cutoff optics are sufficiently different from traditional light luminaire styles so as to restrict traditional styles that might be used; The dramatic and somewhat harsh climate of Yosemite must be accommodated. Products should be suitable for Valley Floor or higher elevations; Lighting systems should be selected for 20 year life if possible by requiring very durable materials and finishes. Lighting equipment should be specification or premium grade to sustain this life requirement; Mounting systems and locations must be equally durable, taking the forces of man and Nature into account.

The team ultimately used the words "appropriate" and "appropriateness" to describe the proper application of lighting equipment in each situation. It is a combination of technology, design, history and common sense, addressing the widest possible range of considerations. The team was able to determine a few specific luminaires to use in common applications.

Pole Lights and Bollards

There are many frontcountry locations where pole lights are recommended, including parking lots, gas stations and bus stops. The challenge was to determine a pole style that would look appropriate and age well, while maintaining the lighting qualities recommended by the study.

The final choice was for a crook-arm, bell shaped pole light with sharp cutoff optics and flat lenses. Painted forest green to blend against the typical backdrop of the forest, these particular poles were specifically chosen to bridge a wide range of traditional and contemporary rustic building styles and appear as "original" as possible without sacrificing lighting quality. The selected manufacturer, Architectural Area Lighting, is based in California and features high performance optics with the choice of several IES distribution types. Using a 100 watt metal halide lamp and mounted between 15 and 20 feet above grade, this lighting system is capable of exactly meeting the design requirements for parking lots and other service areas. The number of poles was increased and mounting height reduced to produce higher light levels around gas pumps.

While the lighting requirements of the pole light could be met with ordinary shoebox luminaires, the style of the luminaire was critical in the selection of this product. It was acknowledged, however, that other styles might be suited to other building types or specific applications. For instance, a different style might look better near the recently renovated Yosemite Lodge (by Esherick Homsey Dodge and Davis, see photo). This choice was left open to future architects and landscape architects on future projects.

During the review of existing lighting, we noted a number of contemporary "bollard" lights, especially in the area around Yosemite Village and the shopping core of the Park. Unfortunately, most of the bollards were damaged, many of them leaning to one side. Low-level lighting in this rugged environment is doomed to being buried in snow, struck by cyclists and snowplows, and occasionally vandalized. A more robust solution was needed. The team selected a post-mounted luminaire instead of a bollard. Mounted one to each of one or more sides of a post, the luminaire employs a 26 watt compact fluorescent lamp. The post, made of concrete or stone, is set back from the trail. In its most common application, there is only one luminaire per post.

The selected luminaire is a downlight-only, natural bronze housing which can be mounted to a wall, post or other vertical surface. Bronze was chosen to permit the light over time to develop a natural patina, in turn making the design appear more original to the Park. The manufacturer, Shaper Lighting of Richmond, California, also offers variations in lamp type, size, and material. With its soft geometric shape, this light can be used in many applications, keeping lighting fixture types to a minimum.

Other Lights

The completion of the Lodge renovation included a number of low voltage spots and landscape lights, mostly to permit after dark dining in the patio area outside of the Mountain Room Restaurant. This is one of the few applications where the dramatic lighting techniques often associated with landscape architecture can be employed.

Since the project was completed, additional projects have begun and their design teams have been required to follow the master plan described here. The most common complaint about the plan is that is requires more lighting design skill than most traditional engineers and contractors possess. Project budgets need to be increased, both to retain professional lighting designers and to utilize the better quality lighting equipment called for in the plan. The results, however, are clearly more sustainable and natural to the visitor and employee alike. LASN


Related Stories




December 10, 2019, 7:47 pm PDT

Website problems, report a bug.
Copyright © 2019 Landscape Communications Inc.
Privacy Policy