As Joni Mitchell sang, they “paved paradise and put up a parking lot”—but who said that parking lots couldn’t have redeeming qualities? In our San Francisco-based landscape architecture studio, we wanted to explore the benefits of designing a better parking lot. Building on the work of other designers and ecologists, we knew that well-landscaped lots can improve infiltration, increase shade for human comfort, diminish urban heat-island effects, use phytoremediation to clean polluted runoff, augment wildlife habitats, and, if the conditions are right, provide off-hours public open space. What was missing, however, was a rigorous site analysis to help determine which of these design approaches was best for any given site.
To address this gap, we connected with Leigh Christy in our Los Angeles office. She and her Cities + Sites designers are working with an impressive mapping tool called Hazel, which she helped develop as part of a team led by the Arid Lands Institute. The 2015 winner of the AIA College of Fellows’ Latrobe Prize, Hazel maps soils with high potential for infiltration, and subtracts areas of known sub-surface contamination, locating opportunities for aquifer recharge. For now, its data is limited to the San Fernando Valley.
Peter Arnold, the co-director of Arid Lands, sent us his data for the San Fernando Valley. Rachael Cleveland, a landscape designer in our San Francisco office, used publicly available GIS maps to overlay data on hydrology, elevation, land use, and the location of parking lots. In analyzing the overlaps we saw a variety of applications for this lot concept, all of which could take advantage of existing land use. Thus the Park*ing Garden was born.
We identified three opportunity sites, each with specific programmatic adjacencies to drive our design approach. While certain strategies can be applied to every site—the use of permeable pavers, for instance, and drought-tolerant planting palettes—specific site conditions will vary, informing the material palette, the level of detail design, and the potential program. These include proximity to a water feature or natural area, anticipated level of use, context (urban, residential, etc.)
- Adjacent to an educational facility: This parking lot cleans water before it enters a nearby body of water (in this case, the Los Angeles River), and provides additional event and play space on nights and weekends for the students of the K-12 Campbell Hall School.
- In or adjacent to a downtown/civic center: Due to its public visibility, this lot calls for a more refined material palette. The parking plaza could provide space for farmer’s markets, food trucks, and other public events and gatherings.
- Adjacent to a natural area: Located at the urban periphery in a park and recreational area, this lot incorporates a rustic material palette of crushed stone and native plantings to nourish habitat and create visual continuity with the surrounding natural area.
For each site, we calculated the amount of water that would be returned to the aquifer based on area and average yearly rainfall. Aggregated across the high-infiltration zones, these amounts could represent significant opportunities for aquifer recharge. For instance, we calculated that, for downtown San Fernando alone, if all the parking lots over permeable soil were made into parking gardens, 16 million gallons of water would return to the aquifer each year.
I presented our concept for the first time at the VERGE Conference in Santa Clara, California, as part of a panel on Decentralized Infrastructure. During the discussion, a representative from Edison mentioned that Los Angeles County currently pays $1,000 an acre-foot for imported water and foresees paying much more should drought conditions worsen. If the cost of the Park*ing Garden were less than the cost of buying municipal water, a case could be made for large-scale applications. However, as an audience member pointed out, drought conditions limit the volume of water reaching many of these sites. So, to provide a fail-safe, on-site source of water, we anticipate designing the Park*ing Garden in conjunction with a greywater-harvesting system.
We are now exploring multiple partnerships for a pilot study. We’ll keep you posted the location of our first Park*ing Garden!
Arid Lands Institute co-directors Peter Arnold and Hadley Arnold lead a team that includes Rowan Roderick-Jones, CSci, ENV SP, Associate, Water Systems Group, ARUP, San Francisco; Deborah Weintraub, AIA, LEED AP, Chief Deputy City Engineer, Bureau of Engineering, Department of Public Works, City of Los Angeles; Leigh Christy, AIA, LEED AP BD+C, Associate Principal, Perkins+Will, Los Angeles; and John Haymaker, AIA, Ph.D., LEED AP, Director of Research, Perkins+Will, Atlanta.