Entity Staff Report - 8/24/2021CITY COUNCIL OF SALT LAKE CITY
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COUNCIL STAFF REPORT
CITY COUNCIL of SALT LAKE CITY
TO:City Council Members
FROM:Sam Owen, Policy Analyst
DATE:August 17, 2021
RE:2020 Salt Lake City Street Lighting Master Plan
NEW INFORMATION
Pursuant to city resolution and state code, the City Council asked the Administration to present the
Street Lighting Master Plan proposal to the City Planning Commission. The April 14, 2021 City
Planning Commission forwarded the following along with a positive recommendation (i.e. a
recommendation that the City adopt the plan & its accompanying documents): the Commissioner
recommended that the Council “further explore the warmness of the light and the kelvin temperatures
and further understand that fully.” (Attachment 3)
It’s the understanding of Council staff that the Department of Public Utilities is confident in the plan’s
current recommendations and resources in the context of color temperature. The following
reconstruction of feedback and new information might be helpful and draws from a technical memo
(Attachment 2) prepared by the department & its consultant on the topic of light temperature and
impacts to the following categories of organic life.
The Department has communicated that the plan in its current state has adequate and appropriate
control measures to mitigate impacts to humans and wildlife, such as its neighborhood-level
evaluation and engagement recommendations for the process of developing lighting solutions for
unique geographic areas throughout the city.
-Birds:
o “There is no evidence that color temperature is a driving force in attraction and
mortality of migratory birds.” (Attachment 2, page 11, last paragraph).
-Insects:
o “One group where color is relatively more important is insects, which are, in general,
more attracted to blue, violet, and ultraviolet than yellows and reds. There are
exceptions to this pattern, but studies of insect attraction to different color
temperatures of LED find that lower color temperatures attract fewer insects. This
relationship has been quantified and can be used to compare attraction of specific
options for street lighting [citation omitted for clarity]. For nearly all [insect]
organisms investigated, lower color temperatures are assessed to have reduce impacts.”
(Attachment 2, page 11, last full paragraph)
Item Schedule:
Briefing: August 17, 2021
Public Hearing: TBD
Potential Action: TBD
Page | 2
-Human beings:
o “Scientists who are skeptical about the potential for outdoor to affect human health
point to the intensity thresholds for melatonin suppression. Based on models of human
physiology, they demonstrate that melatonin suppression is likely to be very small or
not measurable below approximately 5 [lux] [this is a technical measurement for one
dimension of lighting intensity]. Since outdoor lighting rarely reaches these levels
within dwellings, the impact is presumed to be minimal, regardless of color
temperature. This argument, however, does not extend to exposures outdoors at night
and illumination under street lighting often exceeds 5 lux.
A precautionary approach to color temperature for human circadian health relative to
outdoor lighting would be to favor the use of lower color temperature lighting… which
then would be balanced against other guideposts.” (Attachment 2, page 11, first
paragraph, emphasis added)
Finally, dark skies interests have been referenced or represented as compelling for inclusion and
serious consideration in the plan. The Department’s technical memo provides the following advice for
technical implementation sensitive to dark skies interests: “The take-home message of this research
for the Salt Lake City street lighting master plan is that for LED lamps lights to reduce light pollution
compared with the previously common HPS lamps, they must be 0% uplight [sic], 50% less bright,
and with a [color temperature] of no greater than 3000 K.” (Attachment 2, page 12, last paragraph)
In other words, for dark skies interests & for purposes of reducing impacts to organic life, the
Department has represented that the plan allows for flexible and responsive implementation of
lighting strategies to address a range of concerns, such as those listed as examples above.
In the future, the Council might consider the following elements in the context of a
potential motion considering adoption of the plan:
-The Council could include legislative intent language that the “dark skies” mitigation criteria
for “minimum impact on light pollution” be followed uniformly & that the department provide
annual or bi-annual reports on locations where that guidance has been superseded by other
constraints in the course of lighting implementation.
-The Council could ask the Department to consider where impacts to wildlife can be reduced or
eliminated, and provide a report on proactive lighting implementation that takes this value
into account as the plan moves ahead.
-The Council might ask the Department or Administration to consider options for evaluating
impacts to insect communities as a result of City street lighting changes.
-The Council might ask the Department to consider whether and where there are situations
where residents or groups of residents could regularly experience lighting intensity from public
fixtures at a level that would disrupt melatonin regulation.
Attachments
1. Transmittal
2. Department correlation report
3. April 14, 2021 Planning Commission minutes
Page | 3
PREVIOUS INFORMATION FROM THE FEBRUARY 2021 BRIEFING
ISSUE AT-A-GLANCE
The Council will receive a briefing on the proposed Street Lighting master plan. The new plan
synthesizes community feedback and technical advice into a document by which the department
proposes to guide street lighting improvement and maintenance throughout the city. The plan seeks to
create accommodation for different lighting needs and desires throughout the city.
Adoption of the street lighting master plan does not have a budget impact for this fiscal year; however
it is likely that deliberation on and adoption of the plan would pave the way for a new capital
improvement program and financial strategy for the Street Lighting enterprise fund. These
subsequent phases would have budgetary impacts for the enterprise fund, as well as potential impacts
to ratepayers.
ADDITIONAL BACKGROUND
From the transmittal: “The most recent street lighting plan was completed in 2006. In 2013, the
management of the streetlight system was transferred from the Transportation Division to the
Department of Public Utilities. This transfer included changing the funding source for the operation,
maintenance and capital improvements of the system from the General Fund and Special Assessment
Areas [SAA] to a newly created street lighting enterprise fund.”
The city provides different tiers of lighting service through the Street Lighting enterprise fund that the
current system inherited from the previous SAA structure; for example, enhanced lighting areas in
Rose Park, Yalecrest, and in the downtown area are assessed different rates for corresponding lighting
service that varies from the basic streetlighting in most of the city. Additionally, the department
maintains a private lighting program that receives a $20,000 annual grant from the general fund. This
funding allows property owners to obtain matching funds from the city for private light installation in
the public right-of-way. Maintenance of those private lights is the responsibility of the property owner,
although the department facilitates access to a lighting contractor to support that.
From the transmittal: “During the first few years of conversion to the new LED fixtures mainly within
industrial, commercial and higher density residential areas, Public Utilities received more positive
feedback than negative. When installation [of new LED lights] began in the residential neighborhoods,
there were more complaints. Residents were not pleased with the brightness of the lights as well as the
white light emitted. The City is also proactively working on various streets projects, community
improvement projects, pedestrian and bicycle friendly projects, and issues related to crime. Street
lighting has a role to play in all of these endeavors.” To this end, the plan also contemplates its
intersections with other adopted city planning documents. (transmittal page 39 et seq., plan page 19 et
seq.)
The department conducted extensive outreach through community and technical advisor groups. A
more detailed report on the outreach is located in the transmittal on pages three and four.
Furthermore, Council Members met in small groups with the administration to discuss the plan over
the summer of 2020.
ATTACHMENTS
1. Administration transmittal
Page | 4
POLICY QUESTIONS
1. Council Members often receive persistent and sometimes conflicting requests from
community members and community groups for lighting.
a. The Council might be interested in hearing from the administration about how
requests from community members and community groups would be vetted so
that lighting implementation takes place with inclusive engagement.
b. Council Members might wish to know how the administration proposes
resolving conflicting lighting requests; e.g. would those be resolved by taking
polls of property owners; what other methods would be available to determine
how to move forward when requests are conflicting for one area.
2. Council Members have adopted the expectation through resolution that master plans
go through a vetting process that includes review by the city’s Planning Commission.
The Street Lighting master plan has been in progress since before that resolution was
officially adopted in 2020. The Council has adopted other planning documents since
the resolution adoption that have not been reviewed by the Planning Commission.
a. Council Members might wish to request feedback from the administration on
the potential value of the Planning Commission reviewing the lighting plan
before its potential adoption.
3. The Council might wish for more specific figures related to the anticipated annual
budget impact when it comes to ongoing, regular implementation of the guidance in the
plan.
a. Additionally, when it comes to annual budget deliberations for the Street
Lighting enterprise fund, the Council might request a more extensive oversight
and guidance role when it comes to capital planning and appropriations for
each coming year, not unlike the general fund capital improvement program
process.
b. An opportunity to review this enterprise fund budget in greater depth each year
and throughout the interim could give the Council greater opportunity to review
the capital planning and budget proposals for equity considerations.
c. Because the technical and service requirements of the Street Lighting fund are
different from the other Public Utilities enterprise funds, additional budget
oversight and engagement could be more appropriate when it comes to the
improvements and expansions of the city’s lighting system on the basis of the
proposed plan.
4. Community members have inquired about the creation of enhanced lighting areas
through the general fund capital improvement program (CIP). Council Members might
ask for feedback from the department about the feasibility of creating these enhanced
lighting areas through general fund CIP, and then transferring the asset to the
enterprise fund for maintenance and cost recovery through increased lighting fees.
APPENDIX A
The master plan proposes the following policy statements (transmittal page 18; plan page 10):
Based on the application of planning guideposts and input of the steering and
technical committees, the master plan implements the following major policies:
• Street lighting will enhance safety through the implementation
of industry recognized standards.
Page | 5
• Street lighting standards include allowances to encourage dimming strategies
relating to pedestrian activity, wildlife and dark skies lighting.
• Street lighting will minimize the obtrusive effects of light at night resulting from
light trespass, light pollution, and glare through the selection and placement of
appropriate poles, fixtures, light type, and light levels.
• Provide pedestrian lighting in accordance with neighborhood plans and in
accordance with the typologies in this plan.
• Provide street and pedestrian lighting that minimizes impacts to sensitive
wildlife species.
• Select fixture types to provide dark skies protection.
• Implementation based on neighborhood and community input to determine pole,
fixture type, maximum and minimum light level, and the implementation of
adaptive dimming applications when appropriate.
The plan also enumerates a number of implementation priorities and steps; “proposed for
highest priority are neighborhoods current underserved for street and/or pedestrian
lighting based on adjacent land uses.” (plan page 11) Furthermore, “high conflict areas”
such as neighborhood byways and transit stations are proposed to be highest priority.
High conflict refers to the potential for an area to have a diversity of uses and needs. The
plan offers a helpful side-by-side table showing how the policy proposals have been
revised from their 2006 predecessors. (transmittal pages 34-35, plan pages 14-15)
APPENDIX B
The plan proposes the following process for implementation (transmittal page 19, plan
page 11). This process, all four steps, would take place systematically based on
recommendations and classifications made in the plan.
STEP ONE:
• Identify high conflict areas in the City
• Review the current lighting map to identify underserved neighborhoods
and high conflict areas
• Respond to request from community or neighborhood for lighting change
STEP TWO:
Page | 6
• Contact community and neighborhood representatives to identify
priorities and review options according to the matrix
•Identify neighborhood-preferred option according to the matrix
STEP THREE:
• Estimate cost of preferred option
• Seek funding approval
STEP FOUR:
• Design, schedule and implement preferred option
APPENDIX C
Page | 7
Page | 8
APPENDIX D
Salt Lake City Street Lighting Master Plan
Process & Issues Related to Correlated Color Temperatures (CCT)
06/16/2021
The topic of Correlated Color Temperature (CCT), which describes the perceived color of a light source, related
to street lighting has become quite controversial with the transition from predominantly high pressure sodium
(HPS) street lights with an amber color temperature (2200K CCT) to light emitting diode (LED) street lights,
which are can vary in color temp, typically from warm white (2700K) to cool/bluish white (5000K).
Recommendation: With a complexity of various research and opinions related to the CCT of street lighting, we
recommend that Salt Lake City perform a few pilot installations that demonstrate and compare different
CCTs in a few areas throughout the city, such as Single-Family Residential, Multi-Family Residential,
Commercial, and Downtown. These demonstrations will allow Salt Lake City to engage the public and
stakeholder groups in the final selection of CCT that is preferred and appropriate for each area. This process
should include some educational outreach to inform the public about the various issues related to CCT as
described in this memo and gather data on the preferences of the public and stakeholder groups.
What is Correlated Color Temperature (CCT)?
Correlated Color Temperature (CCT) is a measure of light source color appearance as compared to an ideal
blackbody radiator that is heated to a specific temperature, measured in degrees Kelvin (K). This is similar to
the variation of color seen in flames of a fire or gas stove. The higher temperature flame is perceived as blue
and lower temperature flame is perceived as yellow to orange.
How CCT is Addressed in the SLC Street Lighting Master Plan
The CCT of street lighting affects a few different areas of human experience and environmental impacts,
including: Brightness Perception, Nighttime Visibility, Color Identification, Aesthetic Character, Personal and
Cultural Preference, Human Health, Dark Skies and Behavior of Wildlife and Insects. This article from Pew
Charitable Trusts, “Citing Health Concerns, Some Cities Consider Dimmer LED Streetlights” provides an
overview of some of the controversial topics.
The Salt Lake City Street Lighting Master Plan has considered all of these perspectives by implementing a
thorough Engagement Process, evaluating current research, and providing flexibility of on-going community
engagement to determine the final CCT to be used in each neighborhood or Council District. This Engagement
Process helped to develop the Guideposts for this Street Lighting Master Plan, which are: Safety, Character,
Responsibility and Equity. All of the decisions and guidance within this Plan have been considered and
balanced in relationship to these Guideposts. Considering the Guidepost of Responsibility, the Street Lighting
Master Plan has followed the advice from the American Medical Association (AMA) and International Dark-Sky
Association (IDA) for a maximum of 3000K CCT in Commercial, Retail, Civic and Downtown areas. This Master
Plan goes further, by limiting the CCT in Residential areas to 2700K maximum, and near environmentally
sensitive areas to 2200K maximum. By stating “maximum” CCT levels, and providing a path for on-going
community engagement, this plan allows the flexibility for each community to determine if they would
prefer lower CCTs than these maximums.
The topic of CCT related to visibility and health are currently very active areas of research, with varying
conclusions which are sometimes contradictory. In general, the current body of research, and understanding
of human preferences indicates the following trends, which have been categorized according to the Street
Lighting Master Plan Guideposts:
• Safety – Brightness Perception: Higher CCT’s tend to appear brighter at night, even at lower measured
light levels. This is related to a shift in spectral sensitivity toward blue light in lower light levels
experienced at night under street lighting. While this can have a positive effect on visibility, it can also
have a negative effect of increased glare if not properly controlled. Early LED streetlight conversions
using cool/bluish white (5000K) LEDs installations received significantly negative public reaction.
• Safety – Nighttime Visibility: Higher CCT’s may improve visibility at night, however, some studies are
contradictory. Some street lighting visibility studies show that higher CCT’s result in improved visual
detection distance1. Other studies show lower CCT’s with improved detection distance, however, the
lower CCT may result in fatigue and reduced detection distance over longer periods of time2.
• Safety – Color Identification: Color Rendering is more important than CCT for color identification. This
topic of color identification was noted as a high priority for the Police Department. Prior to LED, lower
CCT light sources like high pressure sodium (HPS) (2200K) and low pressure sodium (LPS) (1800K) also
had very low color rendering index (CRI), making it more difficult to accurately identify colors of
objects seen under these light sources. Newer LEDs that use a phosphor-corrected amber (PC Amber)
to achieve lower CCTs (1800K – 2200K) can have improved CRI that is closer to higher CCT light
sources. The PC Amber light source does not yet have wide-spread use in street lighting, and has not
been included in many street lighting research studies. The proposed pilot studies are an excellent
opportunity for Salt Lake City to evaluate PC Amber LED against standard white-light LEDs that are
based on phosphor-corrected blue LEDs.
• Character – Aesthetics, Personal & Cultural Preference: CCT can evoke a wide variety of emotions or
perceptions, which can vary from person to person. The very warm amber light from streetlights with
lower CCT’s (1800K – 2200K) associated with the legacy light sources of LPS and HPS may be perceived
as “outdated” by some, while others perceive this color as “warm” and “inviting. Higher CCT’s (4000K
+) are often perceived as “institutional” or “sterile”, while some may perceive this as “contemporary”,
“clean” and “crisp”. The proposed pilot studies would allow citizens and stakeholders to express their
subjective opinions and allow the City to make a data-driven decision for what is appropriate in
different areas.
1800K 2200K 2700K 3000K 3500K 4000K
Warmer --- Cooler
Private/Intimate --- Public
Residential/Hospitality --- Commercial/Institutional
Historic --- Contemporary
Fuzzy/Dingy --- Crisp/Clean
Comfortable --- Glary
• Responsibility – Human Health: Exposure to too much light at night, especially higher CCT light with
more blue content, can disrupt healthy sleeping cycles, or circadian rhythms, in humans. Light in the
blue spectrum suppresses melatonin, which is needed during the day for people to wake up and be
alert. Exposure to blue spectrum light at night also suppresses or delays melatonin production,
resulting in sleep disruption, which can lead to increased long-term risk of some types of cancer,
including breast cancer and prostate cancer. While higher CCT lighting does play a significant role in
melatonin suppression, it is also important to control light levels, reduce glare, and avoid light trespass
from street lighting. Total exposure to light at night, or dosage of light, is needed to understand the
full impact of street lighting as compared to other light exposure from interior lighting, computer
screens, TVs and light trespass from private property.
• Responsibility – Dark Skies: Higher CCT light sources with more blue spectrum light contribute more to
sky glow than lower CCT light sources. The molecular composition of the Earth’s atmosphere refracts,
or scatters, blue spectrum light, which is why our sky looks blue. Controlling light that is distributed
directly upward into the sky is critical to reducing light pollution. This Street Lighting Master Plan
includes recommendations to reduce light pollution from all decorative lights, including Downtown
and Sugarhouse historic lights and neighborhood pedestrian lighting, such as Rose Park. This Plan also
reduces blue spectrum content, changing from 4000K CCT to 3000K, 2700K and 2200K CCTs,
depending on adjacent land use.
• Responsibility – Behavior of Wildlife and Insects: In general, higher CCT light sources with more blue
spectrum light result in more negative effects on wildlife and insects. All full spectrum white lights
(2700 K and up) are considerably more biologically active than existing HPS lights and new PC Amber
LED lights. Using fully-shielded, low glare lights is also an important factor in reducing impacts to
wildlife and the ecosystem. Limiting light trespass into open space areas and critical wildlife habitats,
and providing adaptive dimming schedules are also included in this Street Lighting Master Plan.
• Equity – What is the Right Thing for each Neighborhood?: Engaging each community in the final
decision for the type of lighting and CCT is an important part of an equitable solution. This process
should include some education on the topics included in this memo and others related to street
lighting, as well as some survey and pilot demonstration to gather data on the opinions of the
residents and business owners in the area. While some areas may want more light and higher CCT for
safety concerns, this should be balanced with a responsible approach that incorporates all the issues
of human and environmental health, especially in residential areas.
More Background Information
1. Engagement Process
The Salt Lake City Street Lighting Masterplan was developed from a multi-level approach with a diverse set of
stakeholders and community members including:
• An Advisory Committee which met six times and included representatives from each City Council
District, Department of Public Utilities, and the Mayor’s Office. The Advisory Committee provided
guidance on policy issues and visioning. This group participated in site tours and surveys, visioning
sessions and progress updates along the way.
• A Technical Committee with City representatives from Police, Fire, Sustainability, Engineering,
Planning and Urban Forestry. The Technical Committee represented the interests of their
departments and contributed to the vision and guiding principles. This group participated in a site
tour to inform their feedback throughout the process.
The material and ideas produced from both groups was them reviewed by a community stakeholder group
with representation from Education, Business, Transit/Multi-modal transportation, and Environmental
organizations. The final draft plan includes input from both committees and feedback received during
stakeholder review. Once the draft document was complete, it received initial review from the City Council
and Planning Commission with a final recommendation to the City Council for adoption.
2. Guideposts: Safety, Character, Responsibility, Equity
a. Safety
i. Brightness Perception
The human eye contains two types of light activated cells in the retina, cones and rods. Cone cells require a
higher light level to be activated, and are responsible for color perception, experienced during the day and
under interior light levels. The rod cells are activated under lower light level conditions typically experienced
at night, and provide only gray-scale visual perception. The cones are more sensitive to the yellow end of the
spectrum and rods are more sensitive to the blue end of the spectrum. All lighting metrics, even for street
lighting use the daytime visual sensitivity curve, yet LED light sources with more blue spectrum content, or
higher CCT, appear brighter under lower light levels than lower CCT light sources. This effect is known as the
Purkinje Shift. This explains why people often perceive LED street lights as “brighter” and “more glary”.
ii. Nighttime Visibility Research
There are multiple studies by the Virginia Tech Transportation Institute (VTTI) that study how different street
lighting characteristics affect visibility. These studies measure visual detection distance of objects under
different light levels and CCT’s. Some studies show that higher CCT’s, particularly 4000K – 4100K resulted in
increased visual detection distance, even at 25% of the light level of HPS lights at 2100K1. Yet, the results are
not consistent when comparing CCT and detection distance across multiple studies, and a more recent study
showed that HPS at 2100K resulted in increased visual detection distance than 4000K LED 2.
Figure summarizing studies on detection distance under different roadway lighting in Anchorage, San Jose, San
Diego, and Seattle.
Figure showing comparison of CCT and different light levels on Detection Distance over multiple laps driving
around a test roadway at Virginia Tech Transportation Institute2.
iii. Color Identification
Accurate color identification of objects depends on the spectrum of the light source illuminating the object.
This is measured as Color Rendering Index (CRI), which ranges from 0 – 100, using a broad spectrum light
incandescent source as the reference. The image below shows a red car parked in front of a convenience store
with two different light sources illuminating the car. The parking lot has low pressure sodium lights (CRI - 0)
that have a very narrow, amber color spectrum, which distorts the red color of the car. The front of the car,
near the fluorescent light (CRI - 70) emanating from the convenience store has a broader spectrum of light,
which more accurately renders the red color.
LED light sources commonly used for street lighting with CCT of 2700K – 5000K typically have a CRI of 70 – 80.
The most common legacy light source for street lighting was high pressure sodium (HPS) with a CCT of 2200K
had a CRI of 20 – 35. The image below shows a side-by-side comparison of these light sources (LED on the left,
and HPS on the right) and their resulting ability to render colors in the field of vision.
Newer PC Amber LED light sources provide 2200K and lower CCT with CRI’s ranging from 35 - 68. The higher
range of this CRI is comparable to the lower range of CCT for LEDs with higher 2700K - 5000K. While most
major street lighting manufacturers do not currently offer PC Amber as a standard option, most
manufacturers will consider providing PC Amber as a special modification.
3. Character
a. Perception of Character and Aesthetics
Color temperature of lighting affects many different aspects of human experience. Color temperature is
perceived as cooler (blue) to neutral (white) to warmer (yellow to orange), which is inverse to the
temperature measurement of the ideal black body radiator (or flame temperature). Higher color temperatures
are described as “cooler” and lower color temperatures are described as “warmer”. Color temperature can
also evoke certain emotions or perceptions such as:
1800K 2200K 2700K 3000K 3500K 4000K
Warmer --- Cooler
Private/Intimate --- Public
Residential/Hospitality --- Commercial/Institutional
Historic --- Contemporary
Fuzzy/Dingy --- Crisp/Clean
Comfortable --- Glary
Figure 1. Example of PC Amber used in an environmentally sensitive area. https://adlt.com.au/wp-
content/uploads/2014/02/IMG_7110-620x413.jpg
References 1800K 2200K 2700K 3000K 3500K 4000K 5000K 6000K
In Nature Campfire Sunrise/Sunset Moon Daylight
Color
Description Orange Amber Warm White Warm White Neutral White Cool White Cool Blue
Legacy Light
Sources
Low Pressure
Sodium (LPS)
High Pressure
Sodium (HPS)Incandescent Halogen Neutral White
Fluorescent
Cool White
Fluorescent
Daylight
Fluorescent
(Limited Use)
Interior
Lighting Limited Use Dimmed
Hospitality
Residential /
Hospitality
Residential /
Hospitality Office Office /
Healthcare
Office /
Healthcare
(Limited Use)
Exterior
Lighting
Near
Astronomic
Observatories
Street Lighting
before LED
Higher End
Pedestian
Lighting
Early LED Street
Lighting
Installations
Figure 2. Example of 2200 K LED used for environmental and aesthetic sensitivity.
https://www.atpiluminacion.com/files/actualidad/201223_Yamaguchi/atp-iluminacion-yamaguchi-2@2x.png
Figure 3. Example of 2700 K LEDs in the field.
Figure 4. Example of 3000 K LEDs in the field. https://www.clantonassociates.com/our-projects/16th-street-mall
Responsibility (Longcore)
b. CCT / Spectrum & Human Health
Human circadian rhythms can be influenced by exposure to light at night. The mechanism is presumed to be
the suppression of melatonin production. Melatonin is a naturally occurring hormone that is produced by
humans and most organisms during darkness and it plays central roles in regulating human daily rhythms
across all aspects of human physiology. It is also “oncostatic”, meaning that it keeps cancer tumors from
growing. Because exposure to too much light at night suppresses melatonin, unnatural light exposure has
been identified as a risk factor for certain cancers, including breast and prostate cancer. Suppression of
melatonin varies depending on the wavelengths of light, with a peak sensitivity in the light blue. Daylight, with
a color temperature of 6500 K, is very effective at suppressing melatonin production (Figure 5).
Figure 5. Spectral power of daylight (colors) with the overlap with human melatonin suppression sensitivity (lighter colors). Melatonin
sensitivity curve is in the background in gray. Upper left: Daylight (D65), Upper right: 4200 K LED, Lower left: 2200 K LED, Lower right:
1900K High Pressure Sodium. Source: fluxometer.com
The relative power of lights to suppress melatonin can be calculated, and it decreases with color temperature
for standard light sources (Figure 3).
Few studies connect color temperature with health outcomes in the epidemiological literature, perhaps
because the technology to do such studies is only recently becoming available. A study of breast and prostate
cancer in Spain published in 2018 provides initial information, which is consistent with greater effects being
associated with higher color temperatures. In this study, greater blue light outdoors at residences of cancer
patients compared with those of controls was associated with a 47% increased risk of breast cancer and a
doubling in prostate cancer risk3. In contrast, outdoor lighting alone (of all colors) was not associated with
increased risk. The study also accounted for light experienced in the sleeping environment, with a significantly
greater risk of prostate cancer for those sleeping in a “quite illuminated” bedroom, but no statistically
significant result for breast cancer3.
Figure 3. Relative sensitivity of human circadian system, as measured by melatonin suppression, for typical LED light sources and High
Pressure Sodium, compared with an equal brightness of daylight.
Scientists who are skeptical about the potential for outdoor to affect human health point to the intensity
thresholds for melatonin suppression. Based on models of human physiology, they demonstrate that
melatonin suppression is likely to be very small or not measurable below approximately 5 lux4. Since outdoor
lighting rarely reaches these levels within dwellings, the impact is presumed to be minimal, regardless of color
temperature. This argument, however, does not extend to exposures outdoors at night and illumination
under street lighting often exceeds 5 lux.
A precautionary approach to color temperature for human circadian health relative to outdoor lighting would
be to favor the use of lower color temperature lighting (Figure 3), which then would be balanced against other
guideposts.
c. CCT / Spectrum & Critical Wildlife Habitat
i. Tracy Aviary
Color temperature is one factor that influences the degree to which light at night affects wildlife. Depending
on the group of organisms, color may be able to reduce or increase effects a little or a lot. One group where
color is relatively more important is insects, which are, in general, more attracted to blue, violet, and
ultraviolet than yellows and reds. There are exceptions to this pattern, but studies of insect attraction to
different color temperatures of LED find that lower color temperatures attract fewer insects. This relationship
has been quantified and can be used to compare attraction of specific options for street lighting (Figure 4).
For nearly all organisms investigated, lower color temperatures are assessed to have reduce impacts. The
difference between 2700 K and 3000 K tends to be small, and all full spectrum white lights (2700 K and up) are
considerably more biologically active than existing HPS lights.
There is no evidence that color temperature is a driving force in attraction and mortality of migratory birds,
however. Light visible from above affects the distribution of migratory birds 5, 6, but the satellite used for these
studies does not distinguish between colors of light and in fact does not measure blue and violet light at all.
The recommended approach to reduce impacts on migratory birds from roadway lighting is to fully shield
lights to eliminate upward glare and to only use the amount of light necessary so that the reflected light is
kept to a minimum. Current efforts to reduce bird mortality in Salt Lake City by the Tracy Aviary focus on
voluntary efforts by building owners to shut off interior lights during migration. The amount of lighted
window area on buildings correlates with bird collisions 7. The project team discussed these issues with Ms.
Cooper Farr of the Tracy Aviary during the development of the Master Plan.
Figure 4. Relative attractiveness of different LEDs and High Pressure Sodium to insects, as quantified Longcore et al.8 from an insect
attraction curve developed by Donners et al.9
d. CCT / Spectrum & Dark Skies
We followed the work of the Department of Energy with respect to the effect of different color temperatures
on light pollution for astronomical observation 10. The DOE study modeled the effects of different
combinations of spectrum, uplight, and intensity under different weather conditions, human vision adaptation
levels, and distance from the lights. These results compare high-pressure sodium as the baseline, with PC
Amber LED (1872 K), and 2700–6100 K LEDs. When compared on an equal basis for other factors (same
uplight and intensity), only the PC Amber produced roughly equivalent light pollution compared with HPS and
all full-spectrum LEDs produced significantly more light pollution, especially when considering human night
vision. This difference is shown for a range of LEDs and HPS using the “starlight index”11 (Figure 5). When
both HPS and LEDs were assumed to have 0% uplight and the LEDs were set at half the intensity of the LEDs,
then LEDs with CCT < 3000 K were comparable to or produced less light pollution than HPS. Results were
similar with HPS at 2% uplight and LEDs at 0% uplight and 50% intensity.
The take-home message of this research for the Salt Lake City street lighting master plan is that for LED lamps
lights to reduce light pollution compared with the previously common HPS lamps, they must be 0% uplight,
50% less bright, and with a CCT of no greater than 3000 K. The minimum impact on light pollution could be
achieved with PC Amber or comparable filtered LEDs that produce a similar CCT as HPS (~ 1800 K).
Figure 5. Relative impact of LEDs and HPS compared with a source similar to daylight, using the starlight index9. 2700–3000 K LEDs are
similar in impact to HPS if they are operated with half of the lumen output of the HPS.
4. Equity
This Street Lighting Master Plan strives to provide an equitable approach to the recommendations and
establishment of priorities for implementation. This approach identifies areas that are currently underserved
with street and pedestrian lighting. Some of these areas have expressed concerns of safety, and would prefer
to have more lighting installed in their neighborhood. Other areas, that currently darker and have few street
or pedestrian lights, have expressed concerns about dark skies and light trespass, and would prefer to no
additional lighting it their neighborhood. With these disparate perceptions, this Street Lighting Master Plan
encourages on-going community engagement before implementing any street lighting projects to determine
what lighting strategies the community would prefer.
During this on-going public engagement process, it is important to include some public education about the
issues involved with guideposts, including CCT issues that are discussed in this memo. It is also as important to
implement pilot demonstrations that allow citizens to see and experience the lighting options, including CCT
and dimming, to gather data to make a fully informed decision on the final street and pedestrian lighting
strategies to implement in any neighborhood.
1 Gibbons, Clanton. Seattle LED Adaptive Lighting Study. Northwest Energy Efficiency Alliance, 2014. p. 42
2 Bhagavathula, R., R. Gibbons, J. Hanifin, and G. Brainard. LED Roadway Lighting: Impact on Driver Sleep Health and
Alertness, 2021. Pre-publication draft of NCHRP Research. p.
Report 968. Transportation Research Board, Washington, D.C.
3 Garcia-Saenz, A., et al., Evaluating the association between artificial light-at-night exposure and breast and prostate
cancer risk in Spain (MCC-Spain study). Environmental Health Perspectives, 2018. 126(4): p. 047011.
4 Grubisic, M., et al., Light pollution, circadian photoreception, and melatonin in vertebrates. Sustainability, 2019. 11(22):
p. 6400.
5 La Sorte, F.A., et al., Seasonal associations with urban light pollution for nocturnally migrating bird populations. Global
Change Biology, 2017. 23(11): p. 4609–4619.
6 McLaren, J.D., et al., Artificial light at night confounds broad-scale habitat use by migrating birds. Ecology Letters, 2018.
21(3): p. 356–364.
7 Parkins, K.L., S.B. Elbin, and E. Barnes, Light, glass, and bird–building collisions in an urban park. Northeastern Naturalist,
2015. 22(1): p. 84–94.
8 Longcore, T., et al., Rapid assessment of lamp spectrum to quantify ecological effects of light at night. Journal of
Experimental Zoology Part A: Ecological and Integrative Physiology, 2018. 329(8-9): p. 511–521.
9 Donners, M., et al., Colors of attraction: modeling insect flight to light behavior. Journal of Experimental Zoology Part A:
Ecological and Integrative Physiology, 2018. 329(8-9): p. 434–440.
10 Kinzey, B., et al., An investigation of LED street lighting’s impact on sky glow. 2017, U.S. Department of Energy (Contract
DE-AC05-76RL01830): Richland, Washington.
11 Aubé, M., J. Roby, and M. Kocifaj, Evaluating potential spectral impacts of various artificial lights on melatonin
suppression, photosynthesis, and star visibility. PLoS ONE, 2013. 8(7): p. e67798.
Salt Lake City Planning Commission April 14, 2021 Page 1
SALT LAKE CITY PLANNING COMMISSION MEETING
This meeting was held electronically pursuant to the
Salt Lake City Emergency Proclamation
Wednesday, April 14, 2021
A roll is being kept of all who attended the Planning Commission Meeting. The meeting was called to
order at approximately 5:30 pm. Audio recordings of the Planning Commission meetings are retained for
a period. These minutes are a summary of the meeting. For complete commentary and presentation of
the meeting, please visit https://www.youtube.com/c/SLCLiveMeetings.
Present for the Planning Commission meeting were: Vice Chairperson, Amy Barry; Commissioners;
Maurine Bachman, Adrienne Bell, Carolynn Hoskins, Jon Lee, Matt Lyon, Andres Paredes, Sara
Urquhart, and Crystal Young-Otterstrom. Chairperson Brenda Scheer was excused.
Planning Staff members present at the meeting were: Wayne Mills, Planning Manager; Molly Robinson,
Planning Manager; Paul Nielson, Attorney; David Gellner, Principal Planner; Krissy Gilmore, Principal
Planner; Aaron Barlow, Principal Planner; Marlene Rankins, Administrative Assistant; and Aubrey Clark,
Administrative Assistant.
Vice Chairperson, Amy Barry read the Salt Lake City emergency proclamation.
REPORT OF THE CHAIR AND VICE CHAIR
Chairperson Scheer was not present.
Vice Chairperson Barry stated she had nothing to report.
REPORT OF THE DIRECTOR
Wayne Mills, Planning Manager, provided the public with instructions on how to participate during the
meeting. He also provided the commission with information regarding how permits and zoning functions
in the City.
CONSENT AGENDA
Red Rock Brewery Brewhouse at approximately 426 West 400 North - Conditional Use and
Conditional Building and Site Design Review Time Extension Requests - MJSA Architects representing
200 West Holding, LC the property owner, is requesting that the Planning Commission grant a one-year
time extension on the Conditional Use and Conditional Building and Site Design (CBSDR) approvals for
a brewery at the above listed address. The Commission originally granted Conditional Use and CBSDR
approval for this project on April 24, 2019. A one-year extension to the Conditional Use approval was
previously granted on April 22, 2020. This request would extend both approvals to expire on April 24,
2022. The project is located within the TSA-UC-T (Transit Station Area Urban Center Transition) zoning
district within Council District 3, represented by Chris Warton. (Staff contact: David J. Gellner at (385-
226-3860 or david.gellner@slcgov.com) Case numbers PLNPCM2018-01008 & PLNPCM2019-00255
APPROVAL OF THE MARCH 24, 2021, MEETING MINUTES.
MOTION
Commissioner Lyon moved to approve the consent agenda. Commissioner Bell seconded the
motion. Commissioners; Bachman, Bell, Hoskins, Lee, Paredes, Urquhart, Young-Otterstrom, and
Lyon voted “Aye”. The motion passed unanimously.
Salt Lake City Planning Commission April 14, 2021 Page 2
PUBLIC HEARINGS
Bookbinder Studios on 2nd West Design Review at approximately 422 South 200 West - A request
by Scott Harwood, representing OZ Opportunity Fund LLC, is requesting Design Review approval to
develop a 7-story, 83’-1" tall residential structure to be located on two contiguous parcels located at 418
S 200 W and 422 S 200 W. The proposed building will encompass 115 studio and one-bedroom units.
The building will have two structured parking levels with 58 parking stalls and five levels of apartment
units above. The applicant is requesting Design Review approval to allow for additional building height
and modification to the required building entrances. The project site is located in the D-2 (Downtown
Support) zoning district and is located within Council District 4, represented by Ana Valdemoros (Staff
contact: Krissy Gilmore at (801) 535-7780 or kristina.gilmore@slcgov.com) Case number
PLNPCM2021-00035
Krissy Gilmore, Principal Planner, reviewed the petition as outlined in the Staff Report (located in the
case file). She stated Staff recommended that the Planning Commission approve the request with the
conditions listed in the staff report.
The Commission and Staff discussed the following:
• Clarification on number of parking spaces provided
Scott Harwood, Eric Hansen, and Jonathan Kland, applicants, provided a presentation with further
details.
The Commission, Staff and Applicant discussed the following:
• Clarification on entrance layout
• Whether the entrance is visible from the street or the parking lot
PUBLIC HEARING
Vice Chairperson Barry opened the Public Hearing;
Lisa Hazel – Raised concern with energy efficiency and would like to see bike parking.
Cindy Cromer – Stated that in the East downtown, a building of this height used to be an allowed use.
She also stated she thinks it’s time that something is done about the fact that the planners are spending
time on a request like this, where units that will be available and are modestly priced have been delayed
arriving in the market place by the amount of time that the petition has been in the Planning Department.
Seeing no one else wished to speak; Vice Chairperson Barry closed the Public Hearing.
The applicant addressed the public comments.
The commission and applicant discussed the following:
• Clarification on height of structure behind the proposal
• Clarification on whether the City will be undertaking mandatory zoning amendments with the result
of legislative changes
• Affordable Housing Overlay zone
• Design Review ordinance modifications and when a proposal for height should go before the
Commission
Salt Lake City Planning Commission April 14, 2021 Page 3
MOTION
Lyon Based on the analysis and findings listed in the staff report, information presented, and the
input received during the public hearing, I move that the Planning Commission approve the
Design Review request (PLNPCM2021-00035) for the project located at approximately 422 S 200
W with the conditions listed in the staff report.
Commissioner Urquhart seconded the motion. Commissioners Bachman, Bell, Hoskins, Lee,
Paredes, Urquhart, Young-Otterstrom, and Lyon voted “Aye”. The motion passed unanimously.
2020 Salt Lake City Street Light Master Plan - Representatives from the Department of Public Utilities
of the City will provide an overview of the 2020 Salt Lake City Street Light Master Plan (Plan). Major
changes in the 2020 Plan from the 2006 Plan include a systematic approach for choosing lighting
strategies of public ways based on adjacent land use, pedestrian activity, and street typology. The 2020
City Street Light Master Plan includes all areas of the City and will impact all City Council districts. (Staff
Contact: David Pearson, Streetlight Program Manager at (801) 483-6738 or david.Pearson@slcgov.com;
or Marian Rice, Deputy Director at (801) 483-6765 or marian.rice@slcgov.com)
Aaron Barlow, Principal Planner, introduced Marian Rice, Deputy Director of Salt Lake City Department
of Public Services, and Jesse Stewart Salt Lake City Department of Public Services.
The following participants were also available for questions:
• Laura Briefer; SLCDPU
• Jesse Stewart; SLCDPU
• Marian Rice; SLCDPU
• David Pearson; SLCDPU
• Dane Sanders, Clanton & Associates;
• Annaka Egan, GSBS;
• Jesse Allen, GSBS;
• Travis Longcore;
Jesse Stewart, provided a presentation with details regarding the proposal.
The Commission and Staff discussed the following:
• Clarification on how neighborhood byway is defined
• Process when a resident request a light on their street
• Clarification on whether there is a standard number of lights on a street
PUBLIC HEARING
Vice Chairperson Barry opened the Public Hearing;
Lisa Hazel – Stated her opposition of the request.
Judi Short – Provided an email comment that was read into the record requesting to know the type of
public engagement was performed.
Dave Iltis – Stated his opposition of the request in its current form.
Seeing no one else wished to speak; Vice Chairperson Barry closed the Public Hearing.
Dane Sanders addressed the public comments and concerns.
Salt Lake City Planning Commission April 14, 2021 Page 4
The Commission and Staff discussed the following:
• Clarification on why the highest amount of kelvin was chosen
MOTION
Commissioner Lyon stated, based on the findings, analysis, testimony and plan presented, I move
that the Planning Commission forward a positive recommendation to the City Council to adopt
the 2020 Street Lights Master Plan and the accompanying Technical Guidance and
Implementation document. With a recommendation to the City Council:
1. To further explore the warmness of the light and the kelvin temperatures and further
understand that fully.
Commissioner Young-Otterstrom seconded the motion. Commissioners Bachman, Bell, Hoskins,
Lee, Paredes, Urquhart, Young-Otterstrom and Lyon voted “Aye”. The motion passed
unanimously.
The meeting adjourned at approximately 7:05 pm.
International Dark-Sky Association
5049 E. Broadway Blvd., #105,
Tucson, AZ 85711 USA
tel +1.520.293.3198
www.darksky.org
Executive Director: Ruskin Hartley
Emeritus Director: David L. Crawford, Ph.D.
Board of Directors: Diane Knutson, President, USA • Kellie Pendoley, Vice President, Australia • Kim Patten, Treasurer, USA • Ken Kattner, Secretary, USA •
Laurel Alyn-Forest, USA • Alejandro Sanchez Miguel, Spain
August 16, 2021
Amy Fowler, Chair
Salt Lake City Council
PO Box 145476
Salt Lake City, UT 84114-5476
Re: Street Lighting Master Plan
Dear Chair Fowler and Councilmembers:
The International Dark-Sky Association (IDA) is the recognized authority on light pollution and is
the leading organization combating light pollution worldwide. We advocate for a future in which
the night sky, filled with stars, is celebrated and protected around the world as shared heritage
benefitting all living things. Protecting nighttime darkness and promoting quality outdoor lighting
practices have distinct benefits for wildlife, human health and wellbeing, energy security, and pub-
lic safety.
Our vision is encapsulated in Values-Centered Outdoor Lighting (https://www.darksky.org/our-
work/lighting/values-centered-outdoor-lighting/), a resolution adopted by our Board of Directors in
January 2021. These values are in turn described by the Five Principles for Responsible Outdoor
Lighting (https://www.darksky.org/our-work/lighting/lighting-principles/) jointly promoted by IDA
and the Illuminating Engineering Society (IES):
1. All light should have a clear purpose
2. Light should be directed only where needed
3. Light should be no brighter than necessary
4. Light should be used only when it is useful
5. Use warmer color lights whenever possible
IDA supports the draft Street Lighting Master Plan that currently under consideration by the Salt
Lake City Council. We find it to be consistent with both Values-Centered Outdoor Lighting and the
Five Principles. It contains the best practices that we encourage for all jurisdictions, and if adopted
it would set a new standard for street lighting plans for large cities.
In particular, the IDA commends specific policy elements of the plan that give it flexibility while not
compromising on core principles. These elements include:
• A flexible approach to allow illumination levels below IES recommendations that en-
courages dimming strategies based on community engagement and that benefits
both dark skies and wildlife (Principles 3 and 4).
• Use of zones for maximum permissible Correlated Color Temperature (CCT) values
that limit 3000 kelvin (K) lighting to commercial zones; sets 2700 K as the maximum
for residential zones without commercial elements; and establishes 2200 K as a
maximum in open space and the industrial zones, which happen to be near sensitive
natural resources in and near the city (Principle 5).
• Inclusion of policy goals to minimize impacts on wildlife and to balance energy effi-
ciency with human and environmental health needs (Principle 1).
• A commitment to shielding decorative street lighting to eliminate uplight (Principles 1
and 2).
• Specific commitment to reduce the obtrusive effects of light at night, including light
trespass onto private property, light pollution affecting the region, and glare that re-
duces visibility and nighttime safety and comfort (Principle 2).
Municipal lighting systems represent a large component of the light pollution generated by cities in
the United States. This plan, when implemented, will reduce light pollution from Salt Lake City and
make it a leader in this field.
We have experience with the successful LED streetlight conversion of Tucson, Arizona, that
measurably decreased the city’s light emissions (see https://www.sciencedirect.com/science/arti-
cle/abs/pii/S0022407317308178). Appropriate technology and lighting design approaches are
available to upgrade street lighting systems, reduce energy consumption, and limit the adverse
impacts of excessive artificial light at night. The Salt Lake City plan goes a step further to incorpo-
rate 2200 K lighting in some areas, and offers flexibility to choose lower CCTs in residential and
commercial areas. This plan would put Salt Lake City at the vanguard of outdoor lighting best
practices among world municipalities.
Given the above considerations, we urge the City to adopt the Street Lighting Master Plan.
Yours sincerely,
John C. Barentine, Ph.D.
Director of Conservation
cc: Salt Lake City Council
Hon. Erin Mendenhall, Mayor
Street Lighting Master Plan
City Council Presentation
August 17, 2021
Planning Commission Recommendation
SLCDPU Presented to the Salt Lake City Planning
Commission
April 14th 2021
•Planning Commission made a positive recommendation to the City Council to
adopt the Street Lights Master Plan and the accompanying Technical Guidance
and Implementation document.
•Planning Commission recommended to the City Council to further explore the
warmness of the light and the kelvin temperatures, and further understand that
fully.
Engagement Process
Advisory
Committee
Technical
Committee
Residents selected by Council Staff
Represent the interests and concerns of their
district in relation to street lighting.
•SLC Sustainability
•SLC Fire Department
•SLC Police Department
•SLC Transportation
•SLC Engineering
•SLC Planning
•SLC Parks and Public Lands
Salt Lake City
Transportation
Division Salt Lake City
Engineering
Division Salt Lake City
Planning Division
Guideposts
Color Temperature
CCT = 1800K
CCT = 2200K
CCT = 2700K
CCT = 3000K
CCT and Dimming Pilot Study
Dusk to 10pm
Light Criteria
10pm to 12am
Reduce Pedestrian
Criteria
12am to 2am
Light Criteria
2am to Dawn
Reduce to Low Ped
Criteria
Thank You!