6.
City Council Work Session
- Meeting Date:
- 03/25/2014
- Co-Submitter:
- Steven Hill, Streets Leadworker
- From:
- Steven Hill, Streets Leadworker
- Department:
- Public Works
Co-Submitter:
TITLE:
Street Lighting Presentation
DESIRED OUTCOME:
To inform Council of current street light challenges to assist Council in future policy making
INFORMATION:
Purpose: To discuss street light challenges created through the following four competing values.
1-Public Safety –In the past ten years, the City has experienced an increasing number of street light mast arm failures, with eight occurring in the past year. These failures occur when the mast arm mount is ripped out of a steel light pole by wind loading. When these mast arms fail, arm and luminaire assemblies weighing over one-hundred pounds fall onto sidewalks and roadways. These failures appear to be an unintended consequence of a change to City street light standards set in 1989. The revised standards required the installation of Low Pressure Sodium (LPS) luminaires on poles and mast arms designed for use with High Pressure Sodium (HPS) luminaires. To date, none of these LPS assemblies have fallen onto pedestrians or vehicles. However, the failure of street light mast arms creates the potential for injury and/or property damage in the event that a pedestrian or motor vehicle would be struck by a falling mast arm assembly.
Public safety is improved when City roadways and intersections are continuously and uniformly illuminated. Over the past year, the City has averaged about 75 street light outages per day due to premature failure of LPS lamps and luminaires. Only a few cities in the United States have used LPS for street lighting. Some of these cities, such as San Jose, California, are discontinuing the use of LPS. Due to limited demand, LPS luminaires are manufactured to order and supply delays are common.. For example, the current City street light maintenance contractor has not yet received LPS luminaires ordered in October 2013.
2-Energy Efficiency – The City of Flagstaff is committed to sustainable practices including a long term goal to reduce municipal energy usage. In the past, LPS luminaires were identified as the most efficient lamp light source available. Newer Light Emitting Diode (LED) luminaires produce the same amount of light on streets as existing City luminaires while using about 50 percent of the electricity. The reduction in energy usage also results in a reduction in greenhouse gas emissions. LED luminaires also generate less waste over their usable life than existing City luminaires.
3-Fiscal Challenges – The increasing cost for the maintenance of LPS luminaires will exceed the Fiscal Year 2014 budget due to mast arm failures, and widespread premature failure of LPS lamps and luminaires. The current City contract for street light maintenance, which expires on April 1, 2014, has an annual cost of $54,000. Staff anticipates a 300 percent increase in contract rate. An additional $108,000 has been requested in the fiscal year 2015 proposed budget for the new contract.
Another fiscal challenge is the cost to modify or replace some or all of the 3000 existing City street light poles to prevent wind-load caused mast arm failures. Initial cost estimates range from $500 to $5000 per pole. An alternative to the replacement of existing poles is the replacement of existing luminaires with luminaires which have a wind load rating that is safe for the existing poles. Due to local observatories concerns about the spectrum of light from street lights, white LEDs, which are the most efficient (120 lumens/watt), were not considered as a citywide replacement option. Amber LEDs, which produce only yellow light, are very inefficient (19 lumens/watt) compared to existing LPS luminaires (46 lumens/watt). The installation of Amber LEDs would require a capital expenditure of about $28 million and require an ongoing budgetary increase of approximately $494,000 per year for electrical costs. Filtered LEDs, which limit the amount of light emitted in lower wavelengths, are more efficient (96 lumens/watt) than current or Amber LED luminaires. Installation of filtered LEDs would require a capital expenditure of about $2 million and result in an annual savings of about $66,000 in electrical costs.
4-Dark Skies Compliance – A commitment to dark skies is a core value of the City of Flagstaff and its citizens. This is a quality of life issue that not only enhances our connection with the environment but also enables a multi-million dollar astronomical industry. On October 24th, 2001, the City of Flagstaff became the World’s First “International Dark Sky City.” Local astronomers desire the almost monochromatic light emission from low-pressure sodium lamps because it can be “filtered out” for most research.
Background/History/ Research
In 1958, Flagstaff was the first city in the United States to pass an outdoor lighting code. The current City of Flagstaff street lighting standards were adopted in December 1989 in cooperation with local observatories. The standards mandated the use of Low Pressure Sodium (LPS) luminaires for two reasons. First, the LPS lamps produce a mostly single-spectrum, yellow color light output which is desirable to astronomers. Second, the LPS luminaires were understood to be the most efficient available at that time, as measured by lamp lumens per watt. The consensus was that LPS lighting would serve the needs of the city and protect the dark sky concerns of the local observatories. Unfortunately, the mast arm failures related to the wind loads of LPS luminaries are increasingly becoming a risk to public safety.
As a result of discussions between staff at the City and the local observatories, City staff has analyzed several street light luminaire replacement scenarios. The replacement of existing luminaires with LED luminaires having smaller wind-loading values should eliminate mast arm failures. The scenarios provide about the same amount of light that is currently present on city roadways. The analysis compared amber LED luminaires which would address the observatories preference for limited spectrum (yellow) light and a filtered LED product that eliminates most light output below 500 nanometers
The recent reconstruction of West Street provided an opportunity to test several different types of LED luminaires. Amber LEDs were installed between Cedar and Sixth Avenues. White LEDs were installed at the pedestrian signal at West and Dortha. Filtered LEDs were installed between Arrowhead and Sixth Avenues. The intersection of Cedar and West has existing LPS luminaires on the traffic signal poles. These installations allow the four different lighting sources to be observed in one location.
Path Forward:
To prevent additional mast arm failures in the future, existing street light poles need to be modified or replaced, or LPS luminaires need to be replaced with luminaires that do not exceed the structural wind load design of existing poles. If an alternative LED luminaire can be selected, the Flagstaff Metropolitan Planning Organization (FMPO) has $573,000 of Federal funding programmed over next several fiscal years for the purchase of LEDs for use on major roadways.
The existing City street lighting standards should be revised to address mast arm failures, non-uniform lighting and a failure to improve non-compliant roadway lighting to current standards. Updates are necessary to remove the combinations of poles, mast arms and luminaires that exceed the safe wind-loading limits of current standard poles.
The Flagstaff Metropolitan Planning Organization currently has funding available for the City to contract with a lighting engineering firm to perform measurements of the current levels of sky glow in Flagstaff. This would establish a quantitative baseline for use during future street lighting discussions. This type of study introduced scientific data into the controversy about installation of street lighting along Highway 89A in Sedona.
The City of Flagstaff will sponsor and participate in the Dark Skies and Emerging Technology Conference. The conference is scheduled for August 19-20, 2014 in Flagstaff, AZ. The conference will serve as a forum to share data and perspectives by exploring issues related to dark skies, as well as explore ways these issues have been addressed in other regions through best practices in lighting technology, incentives to improve lighting, and model ordinances. The FMPO is contributing research funding for this conference.
1-Public Safety –In the past ten years, the City has experienced an increasing number of street light mast arm failures, with eight occurring in the past year. These failures occur when the mast arm mount is ripped out of a steel light pole by wind loading. When these mast arms fail, arm and luminaire assemblies weighing over one-hundred pounds fall onto sidewalks and roadways. These failures appear to be an unintended consequence of a change to City street light standards set in 1989. The revised standards required the installation of Low Pressure Sodium (LPS) luminaires on poles and mast arms designed for use with High Pressure Sodium (HPS) luminaires. To date, none of these LPS assemblies have fallen onto pedestrians or vehicles. However, the failure of street light mast arms creates the potential for injury and/or property damage in the event that a pedestrian or motor vehicle would be struck by a falling mast arm assembly.
Public safety is improved when City roadways and intersections are continuously and uniformly illuminated. Over the past year, the City has averaged about 75 street light outages per day due to premature failure of LPS lamps and luminaires. Only a few cities in the United States have used LPS for street lighting. Some of these cities, such as San Jose, California, are discontinuing the use of LPS. Due to limited demand, LPS luminaires are manufactured to order and supply delays are common.. For example, the current City street light maintenance contractor has not yet received LPS luminaires ordered in October 2013.
2-Energy Efficiency – The City of Flagstaff is committed to sustainable practices including a long term goal to reduce municipal energy usage. In the past, LPS luminaires were identified as the most efficient lamp light source available. Newer Light Emitting Diode (LED) luminaires produce the same amount of light on streets as existing City luminaires while using about 50 percent of the electricity. The reduction in energy usage also results in a reduction in greenhouse gas emissions. LED luminaires also generate less waste over their usable life than existing City luminaires.
3-Fiscal Challenges – The increasing cost for the maintenance of LPS luminaires will exceed the Fiscal Year 2014 budget due to mast arm failures, and widespread premature failure of LPS lamps and luminaires. The current City contract for street light maintenance, which expires on April 1, 2014, has an annual cost of $54,000. Staff anticipates a 300 percent increase in contract rate. An additional $108,000 has been requested in the fiscal year 2015 proposed budget for the new contract.
Another fiscal challenge is the cost to modify or replace some or all of the 3000 existing City street light poles to prevent wind-load caused mast arm failures. Initial cost estimates range from $500 to $5000 per pole. An alternative to the replacement of existing poles is the replacement of existing luminaires with luminaires which have a wind load rating that is safe for the existing poles. Due to local observatories concerns about the spectrum of light from street lights, white LEDs, which are the most efficient (120 lumens/watt), were not considered as a citywide replacement option. Amber LEDs, which produce only yellow light, are very inefficient (19 lumens/watt) compared to existing LPS luminaires (46 lumens/watt). The installation of Amber LEDs would require a capital expenditure of about $28 million and require an ongoing budgetary increase of approximately $494,000 per year for electrical costs. Filtered LEDs, which limit the amount of light emitted in lower wavelengths, are more efficient (96 lumens/watt) than current or Amber LED luminaires. Installation of filtered LEDs would require a capital expenditure of about $2 million and result in an annual savings of about $66,000 in electrical costs.
4-Dark Skies Compliance – A commitment to dark skies is a core value of the City of Flagstaff and its citizens. This is a quality of life issue that not only enhances our connection with the environment but also enables a multi-million dollar astronomical industry. On October 24th, 2001, the City of Flagstaff became the World’s First “International Dark Sky City.” Local astronomers desire the almost monochromatic light emission from low-pressure sodium lamps because it can be “filtered out” for most research.
Background/History/ Research
In 1958, Flagstaff was the first city in the United States to pass an outdoor lighting code. The current City of Flagstaff street lighting standards were adopted in December 1989 in cooperation with local observatories. The standards mandated the use of Low Pressure Sodium (LPS) luminaires for two reasons. First, the LPS lamps produce a mostly single-spectrum, yellow color light output which is desirable to astronomers. Second, the LPS luminaires were understood to be the most efficient available at that time, as measured by lamp lumens per watt. The consensus was that LPS lighting would serve the needs of the city and protect the dark sky concerns of the local observatories. Unfortunately, the mast arm failures related to the wind loads of LPS luminaries are increasingly becoming a risk to public safety.
As a result of discussions between staff at the City and the local observatories, City staff has analyzed several street light luminaire replacement scenarios. The replacement of existing luminaires with LED luminaires having smaller wind-loading values should eliminate mast arm failures. The scenarios provide about the same amount of light that is currently present on city roadways. The analysis compared amber LED luminaires which would address the observatories preference for limited spectrum (yellow) light and a filtered LED product that eliminates most light output below 500 nanometers
The recent reconstruction of West Street provided an opportunity to test several different types of LED luminaires. Amber LEDs were installed between Cedar and Sixth Avenues. White LEDs were installed at the pedestrian signal at West and Dortha. Filtered LEDs were installed between Arrowhead and Sixth Avenues. The intersection of Cedar and West has existing LPS luminaires on the traffic signal poles. These installations allow the four different lighting sources to be observed in one location.
Path Forward:
To prevent additional mast arm failures in the future, existing street light poles need to be modified or replaced, or LPS luminaires need to be replaced with luminaires that do not exceed the structural wind load design of existing poles. If an alternative LED luminaire can be selected, the Flagstaff Metropolitan Planning Organization (FMPO) has $573,000 of Federal funding programmed over next several fiscal years for the purchase of LEDs for use on major roadways.
The existing City street lighting standards should be revised to address mast arm failures, non-uniform lighting and a failure to improve non-compliant roadway lighting to current standards. Updates are necessary to remove the combinations of poles, mast arms and luminaires that exceed the safe wind-loading limits of current standard poles.
The Flagstaff Metropolitan Planning Organization currently has funding available for the City to contract with a lighting engineering firm to perform measurements of the current levels of sky glow in Flagstaff. This would establish a quantitative baseline for use during future street lighting discussions. This type of study introduced scientific data into the controversy about installation of street lighting along Highway 89A in Sedona.
The City of Flagstaff will sponsor and participate in the Dark Skies and Emerging Technology Conference. The conference is scheduled for August 19-20, 2014 in Flagstaff, AZ. The conference will serve as a forum to share data and perspectives by exploring issues related to dark skies, as well as explore ways these issues have been addressed in other regions through best practices in lighting technology, incentives to improve lighting, and model ordinances. The FMPO is contributing research funding for this conference.