The city of Boise has established a vision to become the “most livable city in the country.” It works to achieve this vision through its values of Lasting environments, Innovative enterprises, and Vibrant communities, or LIV. Following national development trends, Boise is experiencing significant construction in its downtown core, including new mixed-use buildings, hotels, and housing. This requires the city to keep up with capital improvements and infrastructure needs, pushing city officials to brainstorm creative solutions. To support development and its existing downtown neighborhoods, Boise created a LIV district concept—a neighborhood-scale framework for new growth and development that incorporates sustainability, walkability, and other design priorities. The Central Addition LIV District, the first project of this citywide effort, incorporates stormwater management, geothermal energy, and fiber-optic connectivity for businesses and residents.
The Central Addition neighborhood is a well-connected area in downtown Boise, a city that has recently experienced heightened interest in downtown living and other redevelopment opportunities. While updating the neighborhood master plan in 2013, city staff worked with local stakeholders to gain input and direction. That collaborative process inspired a more robust set of partnerships—involving city departments; the city’s urban renewal agency, the Capital City Development Corporation (CCDC); property owners; business representatives; and adjacent academic institutions. These partnerships aided in the creation of a district-scale concept for sustainable neighborhood development, a LIV district.
A LIV district offers a framework for redevelopment. The city describes it on its website as a “geographic area of focused investment that builds on the existing neighborhood fabric, addresses sustainability, and takes a balanced approach to planning.”
Boise’s first application of the LIV district framework, the Central Addition LIV District, is a 48-acre (19.4 ha) area with focused investments in placemaking, mobility, infrastructure, housing, economic development, stakeholder engagement, and collection of data to provide evaluation metrics. The vision for the district is for it to become a lively urban setting, including commercial, institutional, and multifamily residential uses.
At the center of the Central Addition LIV District is Broad Street, a five-block thoroughfare. A pedestrian-oriented corridor lined with high-density mixed-use buildings, Broad Street was chosen as the site of infrastructure improvements that are at the core of the LIV district. With stakeholder and city support, CCDC took on the redevelopment project because it was already familiar with supporting urban renewal projects in the city.
“The way that stormwater is being managed in this district has changed the way we’re doing stormwater management in all our partnerships downtown,” said Haley Falconer, environmental manager for the city. “Despite the challenges it has presented, this new process proved to us that we can do things differently throughout the city.”
In Boise, private property owners are required to manage—through on-site retention mechanisms—stormwater that would result from a 50- or 100-year storm. The runoff from public streets or rights-of-way is managed by the Ada County Highway District, which is responsible for the city’s streets. Stormwater management is frequently accomplished with infiltration practices possible because of favorable soils and low precipitation levels.
“In the Central Addition, we adopted the idea of using space in the public right-of-way for stormwater management both for the roadway and the private property, given that there would be a benefit to the public by treating the roadway runoff and allowing an opportunity for private development to focus their stormwater in those areas,” said Steven Hubble, the city’s stormwater program coordinator. This would allow “an easier pathway to more vertical development on those sites,” he said.
The street design includes innovative stormwater management features, including permeable pavers and Silva Cells—modular blocks that support tree growth and large volumes of stormwater capture in a compact area. Also included are landscaping between roadways and sidewalks in order to maximize buildable areas of private property and reduce pollution flow to the Boise River. During redevelopment, CCDC also implemented a direct-use geothermal heating system for use by Central Addition property owners as an alternative to natural gas.
Innovative Stormwater Techniques
Suspended pavement system. The city installed a combination of Silva Cells, street trees, and interlocking concrete permeable pavers along Broad Street. A stormwater management strategy employing Silva Cells has linked pavement modules that contain healthy soils beneath paved surfaces to support tree root growth. Silva Cells provide an opportunity to grow large street trees, restoring their ecological function, while also supporting traffic loads and utilities. All the stormwater facilities are located in the public right-of-way—under sidewalks or within parking lanes adjacent to the curb.
The Silva Cells were a key aspect of the success of the project, said Brendon Daniels, project engineer for T-O Engineers. “They really helped out because the stormwater system was incorporated into the landscaping system,” he said. “Typically, you look for a separation of the two to avoid damaging one another, but the Silva Cells allowed us to make the processes cohesive in a restricted area.
The facilities in the Central Addition LIV District are designed to provide additional stormwater management capacity for 3.2 acres (1.3 ha) of private property, or about ten city blocks.
“As those properties develop or redevelop, owners will have the opportunity to utilize this infrastructure to meet their stormwater management requirements,” Hubble said. Traditionally, private stormwater management would be managed on site by the owners. The innovative approach in the LIV district allows collaboration between public and private entities with shared responsibilities for long-term system operation and maintenance.
Opened in spring 2018, the Fowler is a 159-unit mixed-use project developed by Local Construct and located on the corner of Fifth and Broad streets in the Central Addition LIV District. Because it is adjacent to Broad Street, stormwater drainage from the roof and surrounding property is managed in the public system, with the property owner contributing to the operations and maintenance costs. This approach resulted in more developable land and helped streamline the development process. About 900 square feet (84 sq m) of public right-of-way on Broad Street was used to install Silva Cells along the Fowler. “Typically, these facilities would have to be installed on the private property side and would restrict the building envelope of the project,” Daniels said.
“The thought is that we cover stormwater-retention needs to make it easier and more desirable for developers to come into the area,” said Karl Woods, project manager for CCDC. Three other large mixed-use projects that follow the Fowler project model were in the design and approval phase in summer 2018, he said.
In July 2018, the LIV District Infrastructure Improvements project was recognized as a Top Project finalist by the Idaho Business Review.
The Broad Street development plan enabled the city to collect stormwater for both private and public property efficiently. “Traditionally, public and private drainage [in Boise] are not combined or treated in comingled facilities, so this project presents an opportunity to consider a new approach which can support urban-type development in the city and positive environmental outcomes,” Hubble said.
Although installation of the new system went well, the partners recognized a need for additional coordination earlier in the process. City agencies, utility providers, and adjacent property owners could have better collaborated from the beginning to ensure that the process included implementing all needed aspects at the same time, as well as to plan organized systems operations and maintenance.
City of Boise, “Central Addition—A LIV District,” https://www.livboise.org/initiatives/central-addition-a-liv-district.
City of Boise Planning & Development Services, “Central Addition Master Plan,” February 2015, https://pds.cityofboise.org/media/406884/central-addition-master-plan-final-with-appendix.pdf.
City of Boise, Central Addition marketing brochure, https://pds.cityofboise.org/media/421968/centraladdition.pdf.
Kim Burgess, “Top Projects awards finalists: nearly 50 projects are in the running,” Idaho Business Journal, July 30, 2018, https://idahobusinessreview.com/2018/07/30/top-projects-awards-finalists-nearly-50-projects-are-in-the-running/.
Nicole Blanchard, “Boise is the fastest-growing area in the U.S., Forbes says. And it will keep growing,” Idaho Statesman, March 1, 2018, https://www.idahostatesman.com/news/local/article202865919.html.