Society news

The society recently got involved with the discussion about a potential wind farm in the immediate vicinity of our Dark Sky site.  Members addressed various governing bodies within Foster Township and we sent this letter to the Board of Supervisors in October 2014 expressing our concerns.


October 11, 2014

To: Foster Township Board of Supervisors and Zoning Hearing Board
Foster Township
1000 Wyoming Avenue
P.O. Box 465, Freeland, PA 18224

From: Greater Hazleton Area Astronomical Society
P.O. Box 1032
Conyngham, PA 18219

Subject: Proposed EDF Renewable Energy Wind Turbines Near Our Astronomical Observatory Site in Eckley


The Greater Hazleton Area Astronomical Society was founded in 1977 as a non-profit educational organization to promote the study of astronomy and to provide an educational function for the Greater Hazleton Area. Since the Society’s inception, members have been involved in science education through special astronomy programs for public and private schools in our area. The society also provides astronomy programs for local organizations, scouting groups, the gifted-student program, state parks and the general public. GHAAS owns and operates an Astronomical Observing Site in Eckley, PA where we conduct astronomical studies and invite the public to view and learn about the night sky through our telescopes. GHAAS is recognized by the astronomical community nationwide for the contributions by its members to the science of astronomy.

As a non-profit educational organization, GHAAS relies on member contributions, donations and fund-raising events for funding.

Since 1989, our Society’s Light Pollution Abatement Committee has been working with local governments on updating of their ordinances as they relate to exterior lighting. The committee has also been educating the public, businesses and industries in our area about the problems of glare, light trespass and light pollution caused by poor lighting practices.

We are concerned about the planned wind turbines proposed to be installed near our Eckley Observatory Site. The nearest proposed location of wind turbines to our South is only 3,000 feet away. Another proposed location of wind turbines is located 3,500 feet to our North. Because of our proximity to the proposed locations of the wind turbines, activities at our Astronomical Observatory Site will be severely affected by obstruction of the night sky caused by the wind turbines. Our understanding is that the proposed wind turbines will be 500 feet tall. Based on our analysis of USGS topographic maps, we estimate that the night sky obstruction will be 12 degrees in altitude because of the wind turbines to our North, and 11 degrees in altitude because of the wind turbines to our South. Besides the direct impact to our site of night sky obstruction we are especially concerned about light pollution and light trespass from the proposed wind turbines.

Construction and operation of the proposed wind turbines will most likely involve a number of lighting installations contributing to light pollution that will negatively impact our GHAAS Observatory Site. These include but are not limited to the following:

1. Tower lighting required by the FAA.
2. Exterior lighting used for windfarm buildings.
3. Parking area lighting.
4. Roadway and access road lighting.
5. Sign lighting.
6. Power Utility storage yard and exterior building lighting.
7. Exterior lighting associated with construction phase activities including:
a. Earth moving equipment and vehicles
b. Temporary construction office trailers, container buildings and other structures.
c. Area flood lighting for nighttime construction.
d. Lighting needed for nighttime operation of cranes and other assembly equipment.
e. Site security lighting.

We are recommending that Foster Township request an impact study from EDF Renewable Energy that includes a determination of the visibility of the wind turbines and support structures in direct view from all areas of our location (Eckley). Documentation in the form of maps, drawings or other graphic projections should be provided that depict the proposed height of tall structures and wind turbine components including all elevation plots between the GHAAS Observatory Site and the wind turbine structures. Such representations should clearly define the portion of structures that would be visible from our site. A listing should be provided of the angle in degrees between the horizon and uppermost part of all tall structures. In addition, an accompanying listing should be provided of the azimuth in degrees of all tall structures using Eckley as a reference

The proposed lighting of the tall structures as discussed in the previous paragraph should be described. This description should include the following:

1. Lamp type proposed, i.e., Low Pressure Sodium, High Pressure Sodium, Metal Halide, Incandescent, Red LED, Xenon, etc.

2. Lamp wattage

3. Type of light fixture proposed as defined by the Illuminating Engineering Society of North America (IESNA), such as “full cut-off”, “cutoff”, “semi-cutoff”, floodlight, spotlight, etc.

4. If intermittent lights are to be used, the flash rate and flash duration should be provided along with an explanation of any synchronization used.

5. Light output intensity of proposed luminaires as measured in candelas.

6. Location of luminaires on tall structures.

A discussion should be provided of the decision process and steps taken to mitigate potential increases in light pollution levels from all exterior light sources proposed. The proposed lighting for the following uses, and any other related uses requiring exterior lighting, both during and after construction of the wind turbines should be described:

1. Building exterior lighting and interior lighting that projects light outside
2. Parking area lighting
3. Roadway lighting
4. Power Utility lighting
5. Security lighting

Proposed lighting should be fully described for proposed buildings, parking areas, access roads, power utility facilities and structures, storage yards and earth moving operations. For each lighting application the following information should be provided:

A plan (or plans) of the site, complete with all structures, parking spaces, building entrances, traffic areas (both vehicular and pedestrian), and adjacent uses that might be adversely impacted by the lighting. The lighting plan should contain a layout of all proposed fixtures by location, orientation, aiming direction, mounting height and type. The plan should include, in addition to proposed area lighting, all other exterior lighting, e.g., architectural, building-entrance, landscape, flag, sign, etc.

A 10’x10′ illuminance grid (point-by-point) plot of maintained horizontal footcandles overlaid on the site plan, plotted out to 0.0 footcandles, which demonstrates mitigation of light trespass.

The maintenance (light-loss) factors, IES candela file nomenclature, lamp-lumen ratings and specific lamp manufacturer’s lamp ordering nomenclature, used in calculating the presented illuminance levels.

Description of the proposed lighting equipment, including fixture catalog cuts, photometrics, glare reduction devices, lamps, on/off control devices, mounting heights, pole foundation details and mounting methods.
Submission of a visual-impact plan that demonstrates appropriate steps have been taken to mitigate the potential consequences of on-site and off-site glare.

GHAAS offers the following recommendations concerning exterior lighting related to the proposed wind turbines. These recommendations are based on minimizing the adverse effect of light pollution to the GHAAS Observatory Site from construction and operation of the wind turbines.

FAA Tower Lighting Requirements: Official government guidance documents pertaining to the lighting of wind turbines and considered in preparation of this recommendation are as follows:

· US DOT FAA Advisory Circular 70/7460-1J dated 11/29/95-Obstruction Lighting.
· US DOT FAA Advisory Circular 150/5345-43F dated 09/12/06 – Specification For Obstruction Lighting
· US DOT FAA Advisory Circular 150/5345-43E dated 10/19/95-Specification for Obstruction Lighting Equipment.
· US DOT FAA Code of Federal Regulations, Part 77, dated March 1993-Objects Affecting Navigable Airspace.
· Report Number DOT/FAA/AR-TN05/50 dated November 2005 – Development of Obstruction Lighting Standards for Wind Turbine Farms

The focus of windfarm lighting plans studied by the FAA is on aviation safety and recommendations made by the FAA relate to visibility of windfarm turbines at night and do not address aesthetic concerns or light pollution caused by obstruction lighting. The FAA’s recommendations for maximizing the visibility of obstruction lighting for aircraft can understandably be at odds with minimizing the effect of obstruction lighting as a public nuisance problem of light trespass and an aesthetic annoyance, and also its effect on light pollution and resulting skyglow.

Any tower construction or alteration of more than 200 feet above ground level requires FAA approval and lighting may be required. Although white strobe lights are allowed on structures by the FAA, their use at night would be extremely detrimental to the night skies of Eckley and would end its use as a night sky resource for the astronomical community. The FAA allows use of red lighting for obstruction lighting by two methods: red flashing incandescent lighting and rapid discharge red strobe lighting. A minimum intensity of 2000 candelas is required at night for red or flashing strobe lighting. The FAA also has a standard (L-810) for red steady-burning obstruction lights, with an intensity of approximately 32 candelas.

Only recently has the FAA begun to address the special concerns of wind turbine lighting which involves multiple tall structures that can be dispersed over a wide area. Wind turbine installations can cover many square miles that vary in terrain features such as hills, flat plains and mountain ridgelines creating the need for obstruction lighting design specific to the particular windfarm location. In addition, the placement of the lights is contingent upon which type of physical configuration of wind turbines is being used, i.e., linear, cluster or grid arrangements.

Existing windfarm obstruction lighting installations have used a variety of obstruction lighting schemes making use of white strobe lighting, red flashing and red strobe lighting and red steady-burning lights at night. FAA Report Number DOT/FAA/AR-TN05/50 dated November 2005, Development of Obstruction Lighting Standards for Wind Turbine Farms, that studied the obstruction lighting of existing windfarms, offered the following observation in its study’s concluding remarks: “The red light fixtures that are programmed to flash simultaneously with each other have been determined to be the most effective and efficient technique for lighting wind turbine farms as obstructions.” By “most effective”, the FAA’s report is referring to the best lighting method for maximizing the visibility of the structures for aircraft. Simultaneous flashing of obstruction lighting in a synchronized manner also unfortunately maximizes the visual effect for ground observers and hence light trespass and light pollution.

The FAA does not require the lighting of all wind turbines of a windfarm but instead will approve plans for lighting specified wind turbine units such as those on the periphery of the installation and the highest wind turbines with unlighted separations or gaps of no more than 1/4 to 1/2 mile.

Aviation Obstruction Lighting Recommendations:

Position wind turbines at locations where obstruction lighting will not be visible from Eckley.

Size wind turbine towers so that obstruction lighting will not be visible from Eckley.

Minimize the number of wind turbines to be lighted within lighting design requirements of the FAA.

White strobe lighting should not be used. As per the FAA recommendation DOT/FAA/AR-TN05/50 : “They (white strobes) distract the pilot from his interpretation of the other red flashing and steady-burning obstruction lights and can cause confusion. Even support towers for meteorological devices located within the confines of the turbine farm should not be equipped with nighttime white strobe lights, but rather display flashing red lights.”

According to an FAA report DOT/FAA/AR-TN05/50, windfarms have experimented with external upward directed flood lighting of turbine structures with halogen floodlights. The FAA concludes “floodlighting a number of wind turbines within an extensive turbine farm installation might be aesthetically unacceptable.” Any upward floodlighting of the proposed wind turbines would be the demise of our Eckley site and its use as a night sky resource.

Existing wind turbine lighting designs have included a mix of both red flashing/red strobe lights each with a minimum intensity of 2000 candelas and of steady-burning red obstruction lights, each with an intensity of approximately 32 candelas. Since the steady-burning red obstruction lights cause less light pollution, their use over red flashing or red strobe lights is preferred and should be maximized in the lighting design.

The FAA has established standards for classifying categories of obstruction lighting and for red flashing or strobe lighting at night, allows a range of periods for the light’s on/off state. This lighting period is defined by “flash rate” measured in flashes per minute (FPM) and “flash duration” measured in milliseconds (ms). For red incandescent and red strobe lighting, flash rates of 20 to 40 FPM are allowed under Category L-864 and 60 FPM under Category L-855. To minimize light pollution, the slowest flash rate of 20 FPM allowed by FAA should be used. For red incandescent lighting, flash durations of 1/2 to 2/3 of the flash period is allowed and for red strobe lighting flash durations of between 100 and 2000 ms periods are allowed. To minimize light pollution the minimum flash durations allowed by the FAA should be used.

The FAA has studied flashing obstruction lighting of windfarms at night that operate in unsynchronized and synchronized modes. The FAA concluded: “synchronization of the obstruction lighting array increased the effectiveness of the lighting installation immeasurably and provided significantly improved information concerning the shape and extent of the wind turbine farm as an entity.” It is recommended that proposed obstruction lighting for the wind turbines not be synchronized in a manner that all wind turbine lights flash at the same time in unison, but instead flash separately in a sequenced pattern in order to minimize light pollution.

We are recommending for the lighting of predominantly horizontal surfaces, light fixtures should be aimed straight down and should be fully shielded fixtures that meet IESNA full-cutoff criteria. Externally illuminated signs should have fixtures mounted at the top of the sign and aimed downward. The fixtures should be designed, fitted and aimed to shield the source from off-site view and to place the light output onto and not beyond the sign. At no point on the face of the sign should the illumination exceed 1-vertical footcandle during hours of darkness. The light source for internally illuminated signs should not exceed 500 initial lumens per square foot of sign face. Only light fixtures approved by the International Dark-Sky Association (IDA) as Dark-Sky friendly fixtures and listed on the IDA web site should be used during the construction and operation of the proposed wind turbines.

In summary, we have major concerns about the proposed EDF Renewable Energy wind turbines near our GHAAS Observatory Site in Eckley. We are requesting that you reject the request for the special exception. Installation of the wind turbines as proposed will severely impact use and operation of our GHAAS Observatory Site in Eckley because of obstruction of the night sky, increase in light pollution and light trespass on our property.

Thanks for your consideration of this request.

Gary Honis
GHAAS Vice-President

Thomas Orff
GHAAS – Secretary