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Make ‘dark skies’ part of the streetlight discussion

While you’re at it …

Posing under a glaring downtown streetlight, then-City Councilors Chris Moore and Larry Delgado were fighting to shield streetlights to save Santa Fe’s “dark skies” back in 1997. (Eddie Moore/Albuquerque Journal)

Last Tuesday, members of the Santa Fe City Council committee took up changes to the ordinance that grants PNM a franchise, or permission, to use city right of way for its power and light infrastructure.

The main reason that the ordinance is on the council agenda these days is to raise the fee that PNM pays for the franchise. The new franchise fee would be 3% of the gross receipts the utility receives from the sale of electricity within the city limits. The fee is now at 2%.

The fee increase is supposed to raise $700,000 and would add 50 cents to a $50 monthly electric bill, since PNM will pass along the cost. The increase, although still not approved by the City Council, is already built into the budget for the next fiscal year that begins July 1. City officials say the franchise agreement with PNM hasn’t been changed since it was first passed in 1974, although, of course, the rate consumers pay for electricity has gone up over the years.

Given a chance to review the ordinance, councilors brought up other issues, like seeking assurances that PNM’s equipment is in good working order (based on the belief that, like potholes, we have too many power outages in Santa Fe); assistance from PNM in converting streetlights to more energy-efficient LED lamps; and liability insurance.

Since this discussion is underway, there’s another thing to put on the City Council’s plate: setting goals to make most or all streetlights “dark sky”-friendly, with hoods or shades that direct light down instead of outward. Santa Fe has spectacular night skies, but glaring streetlights – 60% owned by the city, 40% by PNM – can blot out both public and backyard views. Although Santa Fe does have some shielded streetlights, particularly around the Plaza and other parts of downtown.

Also, Santa Fe needs to ensure that switching to LED doesn’t actually make light pollution worse, which is something LED lighting can do, particularly when its mix of red, green and blue modules has too much blue.

In Tucson, about 23,000 streetlights were switched to LED starting in 2014. City government there worked with lighting experts and astronomers to reduce light pollution. The new lights were fully shielded to send light downward and were hooked up to a wireless network that allowed for dimming and data collection, according to an Arizona Daily Star report.

The International Dark-Sky Association, which happens to be based in Tucson, subsequently did a study that showed that the city’s “skyglow” had been reduced by 7% over the course of LED conversion: good, but not as much as had been hoped for.

The Daily Star report says that, once installed, new lights were dimmed to 90%, with the proviso they could be turned on full blast once the lights get dirty over time. Thousands of lights in low foot-traffic areas were dimmed to 60% during post-midnight hours.

In addition to dimming, a key part of Tucson’s effort to hold down light pollution was to reduce blue wavelengths from streetlights, tamping down what can be a harsh glare and more scattered lighting from standard LED fixtures. “Many cities have put in the most efficient LED lighting systems just to save as much energy as possible and resulting in aesthetically very poor, garish lighting,” expert Christian Monrad told the Star.

Dark-sky advocates are in general worried about LED lighting’s impact. One thing they fear is a “rebound effect,” where the lower cost resulting from LED technology’s reduced energy use just gets plowed into installing still more lights, negating both energy and financial savings.

In other parts of the country, residents can pay to have shields installed on individual streetlights whose glare is bothersome.

All this is food for thought when and if Santa Fe gets serious about considering streetlight impact on light pollution in our own dark sky. With the PNM franchise on the agenda, this may be a good time to start. In any case, the inevitable and necessary conversion to LED lights needs to be undertaken with study and care.