114 permanently affordable homes—Can there be more than 114?

By Shawn Rupp, M.S. Architectural Engineering, CU Boulder 2018

On Thursday February 3, the Boulder Planning Board will hold its first Concept Plan Review for a proposed project at 3300 Penrose Place—east of 30th Street, between Iris and the Diagonal Highway. Since this is the first time the Planning Board will be discussing the project, it’s important to speak up in favor of more housing.

While the project’s proposed 114 units of affordable housing would be an excellent addition to Boulder, the 4.75-acre site offers an opportunity to build an even greater number of units. This would align with Boulder’s goals of reducing in-commuting, providing more accessible housing, and promoting compact infill development.

Write an email of support for the project or learn how to speak remotely to Planning Board on Thursday February 3 here.

Site Description

The proposed development site is a 4.75-acre property that has served as the headquarters of the Geologic Society of America (GSA) since the early 1970s. Located between Iris Avenue and Diagonal Highway and immediately to the west of 34th St, the property is adjacent to the newly-renovated Wonderland Creek bike path and within half a mile of 10 RTD bus stops.

The original GSA building was constructed in 1971 and sits on the north end of the property along with a 1990 addition and 2 paved parking lots. Wonderland Creek runs through the undeveloped south end of the property.

Project Description

This initial proposal from Coburn contains 114 units on the 4.75-acre property, all of which are to be permanently affordable units (60% AMI) managed by Boulder Housing Partners (BHP). Four of the project’s five proposed buildings will be new construction, and one would be an adaptive reuse of the original GSA building. The units are planned to include efficiency living units and one- and two-bedroom apartments.

Site Plan Superimposed on Existing Conditions

This original building was found in 2001 to be eligible for listing on the National Register of Historic Places, and the City’s historic preservation staff is expected to recommend that a landmark designation application be submitted as a condition of this project’s approval. Historic designation would allow the developer to take advantage of state and federal tax credits.

Zoning and Land Use

The zoning for the site is RH-4 (high-density residential), and the designated land use under the Boulder Valley Comprehensive Plan is High Density Residential, which requires residential density of 14 units or more per acre. The proposed project exceeds this density, with a total of 24 units per acre. However, given the size of this property, the proximity to transit and bike networks, and the ever-growing need for housing in Boulder, this project has the opportunity to increase the density even further if the Boulder City Council would pass an ordinance to allow for it.

Under city codes, properties zoned RH-4 have a requirement to maintain 1,200 ft2 of open space for every dwelling unit. Every 2 efficiency units count as 1 dwelling unit, so the total required open space for the proposed number of units is 120,000 ft2. The project currently has exactly this allotment of open space, so the addition of more units would necessitate an alteration to the open space requirement.

City council recently passed such an ordinance for the Diagonal Plaza project. This ordinance allows the project to adopt the mixed-used zoning (MU-2) open space requirement, which means that 15% of the total land area would need to remain open space rather than 1,200 ft2 per dwelling unit. It would be beneficial to do the same at 3300 Penrose to allow for the addition of more housing.


The project as-proposed would require 131 parking spaces under Boulder’s city code. The developers of the project have requested a reduction here and are proposing to build 86 parking spaces (34% fewer than required by code).

This reduction in the number of parking spaces would be beneficial and warranted. BHP has noted that they would provide residents with Ecopasses and work to set up a carshare on site. Given these programs plus the site’s  proximity to transit and bike networks, the number of parking spaces per unit could be reduced even further, either by reducing the number of parking spaces or by increasing the number of dwelling units without increasing parking.

As proposed, the project will add 114 units of much needed affordable housing. However, with a 4.75-acre property that is ideally situated along bike and transit networks, the city has an opportunity to allow even more housing.

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