2022 AIA Communities by Design Reimagining Petaluma SDAT - Report - Page 25
Petaluma DAT
The 15-Minute City
The 15-minute city is a concept that describes a
residential community with a decentralized mixed-use
development node that provides most of the resident’s
daily needs within a 15-minute walk from all the
residents’ homes. The concept – as we know it today –
was articulated by Professor Carlos Moreno of Pantheon
Sorbonne University in Paris and is loosely based on
Jane Jacobs’ classic book on urbanism The Death and
Life of Great American Cites. The concept has recently
been adopted as a planning principal by such influential
bodies as the C40 Cities Climate Leadership Group,
but the idea of an urban environment being created
or substantially altered to better serve the daily needs
of residents by purposely de-centralizing commercial
functions, employment, and vital human services and
thereby reducing automobile use leading to healthier,
human-centric, and sustainable cities has many
precedents and proponents in the 21st century. It is an
idea with a great deal of traction.
One of the primary charges to the AIA DAT team was
to apply this principle and describe what becoming a
15-minute city would mean to the City of Petaluma. To
do this, we began with mapping exercises.
Note: the maps and drawings present within this section
were created during the four-day DAT visit, and are
intended to be conceptual and illustrative rather than
prescriptive.
Community Input
Attendees at the community workshop on August
5, 2022, specified several challenges, assets, and
opportunities for transforming Petaluma into a
15-minute city.
Existing Challenges
• Poor access to food and other needs in many
neighborhoods
• Need more affordable housing options
• Support and services for socioeconomically
disadvantaged communities
• Very car-centric, leading to feelings of unsafety for
pedestrians and walkers
Existing Assets
• Downtown node is walkable and provides many
services and experiences
Opportunities for Action
• Create walkable nodes with food
• Allow more mixed-use neighborhoods that support
small businesses
• Rent control
• More equitable spending and development policy
between East and West Petaluma
Our Approach
First, given the City’s robust mapping database that
illustrate social vulnerability and environmental
degradation information across the City, we overlayed
maps of what we felt were the most relevant data sets
to determine where in the City these impacts were
compounded. Map 1 (“Base Map”) is the base map of
Petaluma we used as an underlay.
Map 2 (“Environmental Impacts”) overlays heat islands
(defined by the US EPA as “urbanized areas that
experience higher temperatures than outlying areas”)
with areas experiencing various pollution impacts such
as a relatively higher presence of airborne particulate
matter or contaminated soils. As heat islands were
present over most parts of Petaluma, the areas where
both categories of environmental impact are present
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have been highlighted in the colored overlayer.
Map 3 (“Socioeconomic Disadvantages”) combines
areas of the City where residents experience higherthan-average housing cost burden, relatively low
income, and a cumulative “social vulnerability index” (the
potential negative effects on communities caused by
any external stresses on human health). These factors
are mapped by the solid tones. A fourth factor, poor
access to grocery stores (defined as residents who live
more than ½ mile from a grocery store), shown by the
red outline on Map 3, includes two large pockets of
residential lots at the right side of the diagram.
Our next step involved creating a 15-minute walk circle
and placing it on the map. The radius of this walk circle
represents the distance an average person can walk in 15
minutes, or three-quarters of a mile. The diameter of the
circles is twice this distance – one and one-half miles –
with a star in the center representing a point within the
circle that is not more than 15 minutes from every other
point within the circle.
Map 4 shows this walking circle centered on Petaluma’s
historic downtown representing the facts that the
historic downtown is most certainly a vital mixed-use
district, but that this downtown is well outside the
15-miute walk distance of most of Petaluma’s residents
– especially those who live in the City’s “east end” on
the other side of Highway 101. Our mission, then, was
to determine how many of these stars – representing
potential mixed-use development “nodes” – would be
necessary and feasible to include all the map’s yellow
zones – the City’s residential blocks.
After covering the City with these planning circles so
that all residential blocks were included, we needed to
shift the nodes as shown in Map 5 according to two
important principles adopted uniquely for this exercise.
Our proposed locations for development nodes:
• Do not displace any existing residential units
thereby making the locations equitable;
• Are located where existing commercial uses and/
or underutilized open space already existed thereby
making the locations more feasible.
From this study, we determined that nine of these
potential mixed use development nodes would be needed
to provide equitable and feasible 15-minute walkable
access for perhaps 95 percent of the City’s residents.
After going back into the City with cameras and maps
and finding exact locations for these development nodes,
we then assigned them priorities based on the overlayed
socioeconomic and environmental impact data of Maps
2 and 3 (see Sketch 1). Map 6 identifies these nodes and
prioritizes them.
Recommended Nodes
We have classified these nine development nodes in
five “tiers”. Node 1 is the highest priority development
site. Nodes 2A, 2B, and 2C are critically important to
achieving Petaluma’s goal of becoming a 15-minute
city. Nodes 3A, 3B, and 3C present clear opportunities
for equitable growth. Development at Node 4 would be
advantageous; Node 5 represents a site that needs only
minor improvement.
For purposes of this report, we will describe the four
nodes in Petaluma’s East End first, the three nodes in
Petaluma’s West End second, and conclude with the two
nodes in Petaluma’s Midtown.
