12/3/2015 | Posted By David Cutler at 10:31 pm

Mapping Hidden Seattle

The City’s Top Opportunities for Growing a Resilient Future

-David Cutler

Today is Buildings Day at COP21 in Paris, where we all take a look at how our built environment can help communities thrive. Locally this year, the City of Seattle is updating its Comprehensive Plan, the top-level urban policy document that guides how the City will manage growth and direct its investments as we move towards a carbon neutral Seattle.

As you might imagine, part of our city’s planning process requires that we calculate whether, in fact, the city has the zoned capacity to accommodate growth estimates.  The calculation is called a development capacity analysis. Typically, the results are summarized in a series of tables and graphs that identify broad geographic areas where we still have room for growth and where we don’t.  Summaries such as this are valuable for establishing city-wide urban policy and for measuring overall performance towards our goals.  For example, it shows that, in general, we are doing a good job of directing growth to Urban Centers and Villages and that, given our current planning assumptions, we have plenty of space for all the newcomers we hope will arrive.  Here’s an excerpt of the city’s analysis from April 2014:


A detailed read shows that nearly three quarters of all housing units added to the city since 1994 have gone to Urban Centers and Villages, and that, for now, we have three times the housing capacity we think we need.

As reassuring as this is on its surface, it doesn’t reveal much of anything about:

  • WHEN expected growth is likely to occur. For example, which types of sites might redevelop sooner and which ones may go later.  Change is rarely uniform.
  • WHAT that growth might look like. Building form and the distribution of building typologies affect issues ranging from neighborhood character, to energy performance and materials consumption. For example, stacked flats generally have better energy performance per square foot than townhouses, house more people per acre of land area, and consume fewer construction materials per unit.
  • WHO it may affect most. For example, existing development standards in our growth areas influence whether redevelopment will be affordable or unaffordable, targeted towards families or singles, owners or renters, and affect the residential densities needed to support local businesses, schools, and social services, and vice versa.
  • WHERE specifically growth is more likely to happen. Urban Centers and Villages are big places, and no two are alike.  As cities grow, often it’s the extremities and seams between neighborhoods that feel the most pressure.  Data aggregated across ½ mile and ¼ miles areas doesn’t help us discern between what is happening at the center and what is happening at the edge of neighborhoods.

As an architect and planner, these are the types of questions that my clients and neighbors ask me about.  And after spending six years on the Planning Commission, whose charge it is to steward the Comprehensive Plan, you’d think I’d have some answers at the ready.  It’s true, there are some to be had.  The Plan’s nearly 400-page Environmental Impact Statement (EIS) and first-of-a-kind Growth and Equity Report evaluate everything from GHG emissions and health to displacement risk and access to opportunity.  The Seattle Sustainable Neighborhoods Assessment Project, another corollary report for the Plan, also provides additional insight into affected populations.  But still, these don’t illuminate how growth may translate down to the scale of the block, or site – which, after all, is where we live, where we work, and where we experience the city on a daily basis.

So, over the course of the last couple months or so, we at GGLO decided to dig a little deeper.  We wanted to discover the map of Seattle that is hidden among the Plan’s data sets and the Land Use Code’s development standards.  What we found might help shed light on how we might prioritize among the Plan’s nearly innumerable goals and policies and how we tailor investments in ways that support city-wide development to ensure an essential supply of housing for Seattle’s diverse population.

We started with the City of Seattle’s Development Capacity Analysis.  We used the same data sources (from the King County Assessor) and the same step-by-step process (See Appendix 2 of the Analysis, pages 13-15) to identify parcels that are likely to redevelop.  But rather than report the resulting capacity as “aggregations of … individual parcel information” by large “planning areas or other areas of interest,” we divided the City into approximately one-acre cells (200’ x 200’, or about a half-block) and vertically extruded the redevelopment capacity within each cell to represent the localized number of potential new housing units, or potential new gross square feet.

We generated three simple maps which correspond to the three ways the City determines whether a parcel has any future redevelopment capacity:

  1. Parcels significantly underbuilt in terms of housing units. Capacity in our city’s multifamily residential zones (HR, MR, and LR) can be estimated almost entirely as housing units, since the Land Use Code severely limits non-residential uses in these areas.  Here, the City calculates a Development Ratio (DR:UNITS) by dividing the number of units existing by the maximum number of units allowed by the Code.  The HR, MR and LR zones each have unique DR:UNITS thresholds.  Below a certain ratio, parcels are considered “REDEV.” Our map shows the number of potential new units geospatially referenced to our one-acre cells.


    The majority of underbuilt multifamily parcels exist in our LR zones, and many these lie outside the boundaries of our Urban Centers and Villages. Areas like Fre-lard, Holman Road, NE 145th and 15th Ave NE, Alki, North Delridge, and Highpoint stand out.  These are areas where new medium-density wood-frame walk-up construction types could provide an affordable and often times close-to-transit housing option for families and growing households.

    Some hot spots where higher residential density can occur include:

    •   Northgate, west of I-5 including the northwest Outpatient Medical Center
    •   Rainier Beach
    •   First Hill
    •   NE 145th and 15th Ave NE
    •   Othello
    •   S. Orcas and Martin Luther King Jr. Way S
  2. Parcels significantly underbuilt in terms of gross floor area. In Seattle’s Commercial and Mixed-Use Zones (C, NC, and SM), both residential and non-residential development are allowed, so the City calculates a parcel’s redevelopment capacity using a Development Ratio (DR:SQFT) based on gross square feet – dividing the existing building gross floor area  by the maximum floor area allowed by the code.  Like DR:UNITS, the C, NC, and SM zones have specific thresholds below which a parcel may be considered REDEV.  To keep the comparison to our HR, MR, and LR zones somewhat apples to apples, and since even Steve Walker, the City’s Director of the Office of Housing says we are in the midst of a housing crisis, we’ve mapped this redevelopment capacity in terms of housing units. We multiplied the potential new gross floor area on a parcel by the observed percentage of residential area per zone, then divided that by an average gross unit area of 1,000 square feet.


    Just like the City planned it, most of our mixed-use capacity is within our Urban Village and Urban Centers.  But, it’s worth noting that where industrial areas exist, development pressure pushes right up to the boundaries, threatening one of the city’s largest and most stable jobs bases. This can be seen clearly in the southern reaches of Ballard.

    Hot spots in the city’s mixed-use zones include:

    •   Northgate on both sides of I-5, including the Mall
    •   Mt. Baker near Rainier Ave S and McClellan
    •   All of South Lake Union
    •   West Seattle Triangle
    •   Othello and Martin Luther King Jr. Way S
  3. Parcels with buildings significantly undervalued relative to the land.  In our downtown and industrial zones, the strength and scale of market influences are such that neither the DR:UNITS method nor the DR:SQFT method is quite appropriate.  Instead, here the City calculates redevelopment potential by dividing a parcel’s assessed building value by its assessed land value.  This is called an Improvement to Land Ratio (ILR), and again, below a certain threshold, a parcel is considered redevelopable.  Our map shows the capacity of these areas in gross square feet.  The large project scales and enormous capital investments required to develop in the downtown zones don’t translate reliably into housing units as a sole measurement of development potential. Often, new projects come on line with a mix of office, housing, and hospitality uses.


    Near our center city, there is a mountain of untapped development capacity in the Denny Triangle, which when built out, can provide an important bridge between with South Lake Union, Pike / Pine and the downtown core. This is likely a future hub of the City.  It is relatively flat, which is great for walking and ground floor retail; project scales are large enough to support a robust mix of housing and jobs; it is at the intersection of transit modes, including LINK, streetcar lines, and bus; and it has already seen significant investments from major employers the likes of Amazon, Vulcan, the Washington State Convention Center, and Federal Courthouse.

    Hot spots:

    •   Yesler Terrace
    •   Civic Square
    •   Denny corridor near 5th

We did not map the development capacity of our single family areas, nor did we look at our industrial zones.  The Development Capacity Analysis shows that Single Family accounts for only 4.4% of the city’s total housing capacity, which one might say is negligible considering that nearly 65% of the city’s land area is zoned for this purpose.  (For more info, look here.)  Put another way, the housing capacity return on acre of land area invested (HC-ROI) in single family zones is 1.09 units/acre, while the HC-ROI for all other areas that allow housing, including downtown and other areas, is more than 17 units per acre.  This means that for every single family house our Comprehensive Plan protects, we potentially prohibit 17 new households from moving to our city.

Industrial lands do not, and frankly should not, allow housing development.  These areas account for over 16% of our total jobs capacity although they occupy only 11% of the city’s total land area.

Also, it’s important to note that just because a parcel is identified REDEV does not mean that it will in fact redevelop.  There are myriad other factors that any property owner evaluates when determining whether to redevelop or sell for redevelopment – things like: is the property’s existing revenue stream more valuable over the long term than receiving a lump sum payment for the land now; or is the construction cost of the allowed building typology low enough to be offset by future sales or rent rates; or more simply, is the complexity and uncertainty of redevelopment in a given location at a given time even worth the undertaking?  Any of these issues could tip a property into REDEV, or vice versa, regardless of what the map shows.

We invite you to follow the link below, dive in and explore hidden Seattle.

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