As Carborro seeks to update the area lighting section of the ordinance, there are two major pollution issues to consider.
The first is pollution created by increased electrical demand or wattage. Since all new electrical demand will currently be provided by Duke Energyâ€™s coal fired power plants all of the health risks associated with burning coal on massive scales will be increased proportionately. These well known risks start at the source of coal extraction and end at the increased stack pollutants from nitrous oxide to CO2.
In an attempt to increase security it has been suggested that the light pole height be raised from 15 feet to 25 feet. To start with there is no factual data to show that increased area lighting reduces crime. It does however decrease fear of crime and that is an important issue since perception is what drives our actions.
In the example presented by the town staff the new 25 ft light would be a 250 watt Duke Energy standard area light. Herein lies the problem. First as the light source moves away from the lighted surface the amount of light diminishes by the square of the distance. It takes a lot more watts to light a surface from 25 feet than it does from 15 feet. The second part of the problem is using Duke Energy lights. Since Duke energy profit is derived from the sale of electricity it is in their interest to have higher wattage lights.
Here is an example for comparison. In Arcadia we have five 12 foot high area lights that provide security. These lights have 13 Watt compact fluorescent bulbs Over twenty years these five lights will use 5,694 Kilowatts of electricity which in turn will produce 13,096 lbs of CO2. If these lights were replaced with the 250 watt Duke Energy lights suggested for the ordinance study over the same 20 years they would consume 109,500 Kilowatts of electricity which again in turn would produce 251,850 lbs of CO2. Almost twenty times as much pollution. Can we really in good conscience think about doing this with Peak oil and global warming on the horizon.
The second form of pollution is a bit more abstract, that is glare and night sky pollution both are lifestyle impacts. Anyone who has flown into RDU and looked down has seen the tremendous amount of reflected light from street lights. It is so bright you can see it from satellites. That is wasted light going into the night sky.
A shielded 250 watt light at 25 feet will still shine brightly into your 12 foot second story window and certainly temporarily effect your night vision at eye level. The 12 foot high Arcadia lights use a fixture called Glare Buster to specifically shield the night sky and the windows of adjacent homes.
My recommendation for the ordinance, as a way to protect us and our grandchildren from both pollution types, would not be to restrict the height of the lights at all but restrict the lamp wattage to 20 watts and restrict glare. This way as you raised the height of the lights you would need to go to more efficient lamps such as LEDs . If this is not politically feasible then the standard height should be restricted to 15 ft with minimum glare with a relatively simple procedure available for raising the height when fear of crime is a perceived issue but keeping the wattage the same by increasing the efficiency of the lamp.
Giles Blunden is an architect and a resident of Carrboro.