Westport AtHletic field lighting

REGulation review & Evaluation report

July2009

Environmental Design Consultants + Lighting Designers

195 Church Street, Suite 10C

New Haven, CT 06510

p: 203.777.1400

overview

Atelier Ten was engaged by the Town of Westport, Connecticut in July 2009 as independent professional lighting consultants to evaluate proposed lighting zoning regulations drafted by the Westport Parks and Recreation Department and to make recommendations about how to address light trespass issues specifically related to outdoor athletic lighting.

Atelier Ten reviewed the Parks and Recreation proposal and subsequently researched existing, applicable municipal lighting ordinances and lighting industry reference materials on light trespass for this report. Atelier Ten visited Staples High School and Saugatuck Middle School on July 29, 2009 to view the two fields and surrounding areas under current consideration.

EXISTING ORDINANCES AND STANDARDS

There are no federal or state regulations that specifically address light trespass. This is an issue that many municipalities have addressed through local ordinances and zoning regulations. Our survey of municipal light trespass ordinances around the US indicates a range of values and approaches to light trespass control. Typical light trespass thresholds or allowable illuminance levels at residential property boundaries vary from 0.1 footcandle (fc) to 0.8 fc, with 0.5 fc being the most common. The standard measurement method also varies. Many of the municipal ordinances offer exceptions for outdoor sports lighting provided the luminaires are well-shielded “low glare” luminaires with low aiming angles (tall poles) and that curfews and schedules are in place to turn lights off after events.

Several technical documents reference light trespass:

The IESNA Recommended Practice 33-99 (RP-33) Lighting for Exterior Environments

Authored by the Illuminating Engineering Society of North America (IESNA) Outdoor Environmental Lighting Committee, this is a design guide for exterior lighting. The guide recommends that municipalities assign a “Lighting Zone” to each zoning district, based on use to inform the amount of allowable light trespass. The values shown are for vertical illuminance measured in footcandles measured at the property boundary at eye level “in a plane perpendicular to the line of sight” [to the luminaire].

Lighting or Environmental ZoneIlluminanceLimit

LZ-1 Dark (park and rural settings)0.10 fc

LZ-2 Low (residential)0.30 fc

LZ-3 Medium (commercial/industrial, high density residential) 0.80 fc

LZ-4 High (city centers) 1.50 fc

RP33 also states “these area [Lighting Zone] categories can provide the basis for restricting the brightness that must be tolerated in a specific environment. Within any category a curfew or “after hours” time may be established allowing higher lighting levels during those areas when the curfew is not in effect.” It does not specifically reference sports lighting but the curfew system is often applied tooutdoor sports and recreation facility lighting.

Model Lighting Ordinance (MLO)

The Model Lighting Ordinance (MLO) is a document co-authored by the Illuminating Engineering Society of North America (IESNA) and the International Dark Sky Association (IDA) and endorsed by the International Association of Lighting Designers (IALD). Currently in its public review phase, the MLO is intended to serve as a professionally written, best practicedocument for adoption by individual municipalities as a reasonable and enforceable approach to controlling light pollution, light trespass, and energy use. The system for measuring glare is still to be developed.

The MLO uses the following light trespass categories:

Lighting or Environmental ZoneIlluminance Limit

LZ-0 No Ambient Lighting0.05fc

LZ-1 Low Ambient Lighting0.10 fc

LZ-2 Moderate Ambient Lighting 0.30 fc

LZ-3Moderately High Ambient Lighting0.80 fc

LZ-4 High Ambient Lighting1.50 fc

The MLOalso offers the following recommendations for sports lighting:

“Complex and Non-Conforming Uses: Upon issuance of a special use permit by the Authority, lighting not complying with the technical requirements of this ordinance but consistent with its intent may be installed for complex sites/uses or special uses including, but not limited to, the following applications:

  • Sports facilities, including but not limited to unconditioned rinks, open courts, fields, and stadiums.
  • Construction lighting.
  • Lighting for industrial sites having special requirements, such as petrochemical manufacturing or storage, shipping piers, etc.
  • Parking structures.
  • Bridges, public monuments, public buildings and urban parks.
  • Theme and amusement parks.

To obtain such a special use permit, applicants shall demonstrate that the proposed lighting installation:

  • Has been analyzed using the Performance Method and for which Sky Glow, Light Trespass and Glare values have been calculated.
  • Has sustained every reasonable effort to mitigate Sky Glow, Light Trespass and Offensive Glare supported by a signed statement describing the mitigation measures. Such statement shall be accompanied by computer calculations indicating the light trespass levels (horizontal and vertical at ground level) at the property line.
  • Employs lighting controls to reduce lighting at a Project Specific Curfew (“Curfew”) time to be established in the special use permit.
  • Complies with the Prescriptive or Performance Method after Curfew. The Authority shall review each such special use permit application. A special use permit may be granted if, upon review, the Authority believes that the proposed lighting will not create unwarranted glare, sky glow, or light trespass.”

The MLO is still in draft form, but has been out for public review since February 7, 2009 and is expected to be adopted later this year. The MLO text could be adopted by Westport regardless of whether it is a 100% document finalized by the IDA and the IESNA.

LEED Sustainable Site Lighting Credit

LEED for Schools is a green building rating system created by the US Green Building Council (USGBC). It has a section that specifically addresses sports lighting and light trespass. It should be noted that LEED is a building rating system designed to minimize negative environmental impacts and awarda rating point for exceeding accepted standards. This light trespass credit SSc8 in its current version is very stringent and most LEED projects do not achieve this credit.

LEED uses the same Lighting Zones and corresponding illuminance limits as RP-33, but it dictates Lighting Zones based on population density and does not offer local authorities the option of designating zones. The population density from the 2000 census map shows the surrounding area of both Saugatuck and Staples Schools at fewer than 3,000 people per square mile. This classifies both fields as Lighting Zone LZ-2. This would allow a maximum of 0.3fc at the boundary.

LEED also stipulates that the illuminance measurements must be taken vertically and horizontally at the boundary on a five foot grid. The vertical grid is taken from the ground to maximum pole height facing the playing field. There is no provision for lighting curfews to comply with in order to achieve the LEED SSc8 light pollution and trespass credit.

Lighting or Environmental ZoneIlluminance Limit

LZ-1 Dark (park and rural settings)0.10 fc

LZ-2 Low (residential)0.30 fc

LZ-3 Medium (commercial/industrial, high density residential) 0.80 fc

LZ-4 High (city centers) 1.50 fc

conclusions

There is no national standard for controlling or limiting light trespass. Light trespass is an issue for which a municipality must determineits own acceptable level of illuminance at the property line, how to measure it and whether to provide curfews or timetables for special use conditions such as sports, recreation, or event lighting.

The currently proposed lighting design approach for Westport using well-shielded luminaires and 80-foot poles is a good strategy for mitigating light trespass for the given locations and conditions. Without a “special use” permit as outlined in the MLO and RP-33, it is unlikely that suitable sports lighting for the Staples or Saugatuck athletic fields could comply with the light trespass levels of 0.3fc or even 0.8fc were it zoned as LZ-3 by the zoning board.

The photometric study provided for the proposed athletic field lighting for Staples High School indicates illuminance levels over 1.0 fc at the property boundary, with footcandle readings falling off to zero quickly beyond the property boundary. This may be need additional photometric analysis, as it seems to assume that the measurement grid is a horizontal measurement at grade. The elevation behind the grandstands in this area drops off sharply and will allow more light to penetrate into the adjoining properties than is illustrated in the photometric report. All light trespass standards in the referenced documentation use a vertical measurement at eye height or above to measure light trespass. We recommend that the photometric report be adjusted to show vertical illuminance up to maximum pole heightas described in the amended Parks and Recreation textas recommended below and the report should account for the elevation changes. The steep slope may cause a higher likelihood of objectionable glare downhill. This may be mitigated through stockade type fence or other visual screening. It should be noted that late autumn football games will take place when there is much less foliage than during the summer.

Regarding the Town of Westport Parks and Recreation proposal, we recommend that Westport consider amending the proposal in the following ways:

32-19.1 Application Requirements

An application for Site Plan and Special Permit shall be submitted as required under §44 of the regulations. In addition to §44, the applicant must submit the following:

(a) A photometric plan for the entire area to be lighted. This plan shall show all property lines that abut the area to be lighted. The values measured are to be vertical footcandles measured at the property border at ground level up to the highest point of structures or luminaires. Calculate the line-of-sight illuminance at or above grade on a vertical plane at the property line, up to the highest point of structures or luminaires. Calculate the direct light from individual luminaires and light reflected from all solid surfaces on the site, using a Light Loss Factor of 1.0. Assume the reflecting surfaces are diffuse.

32-19.4 Conditions of Approval

(d) Lighting structures shall be designed to minimize light spillage onto surrounding residential properties. All lighting must be down directed to the greatest extent possible. Illuminance of 0.3 footcandles or less must be achieved at the property line measured as described in 32-19.1 (a). If illumination levels are above 0.3fc then additional mitigation must be enacted including but not limited to fencing or plantings to block light trespass and curfews and automatic controls.

We also recommend Westportconsider integrating an edited version of theMLO text for special permitting of athletic field lighting, omitting the measurementsfor sky glow and glare since it is still under development within the MLO and a comprehensive system for measurement is not agreed upon by the professionallighting community. Although this document is still under Public Review and currently marked “Not for Adoption or Use,” the section on special permitting is particularly applicable to Westport’s issues. When this document is finalized and released for public use, Westport should consider adopting it as applicable.

As included earlier in this report, the MLO excerpt is as follows, striking out the non-applicable portions and adding minimal text for clarification, as indicated in brackets:

“Complex and Non-Conforming Uses: Upon issuance of a special use permit by the Authority, lighting not complying with the technical requirements of this ordinance but consistent with its intent may be installed for complex sites/uses or special uses including, but not limited to, the following applications:

  • Sports facilities, including but not limited to unconditioned rinks, open courts, fields, and stadiums.
  • Construction lighting.
  • Lighting for industrial sites having special requirements, such as petrochemical manufacturing or storage, shipping piers, etc.
  • Parking structures.
  • Bridges, public monuments, public buildings and urban parks.
  • Theme and amusement parks.

To obtain such a special use permit, applicants shall demonstrate that the proposed lighting installation:

  • Has been analyzed using the Performance Method and for which Sky Glow, Light Trespass and Glare values have been calculated. [using the calculation method described in the Application Requirements].
  • Has sustained every reasonable effort to mitigate Sky Glow, Light Trespass and Offensive Glare supported by a signed statement describing the mitigation measures. Such statement shall be accompanied by computer calculations indicating the light trespass levels (horizontal and vertical at ground level) at the property line.
  • Employs lighting controls to reduce lighting at a Project Specific Curfew (“Curfew”) time to be established in the special use permit.
  • Complies with the Prescriptive or Performance Method[Application Requirements calculation method after Curfew. The Authority shall review each such special use permit application. A special use permit may be granted if, upon review, the Authority believes that the proposed lighting will not create unwarranted glare, sky glow, or light trespass.”

Attachment:

Model Lighting Ordinance (MLO) developed by the International Dark-Sky Association and the Illuminating Engineering Society 60% Public Review version issued February 7, 2009.

Modifications March 2, 2009

End of Report

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