Stormwater management is a crucial element of all site designs, but has increased challenges in higher-density, infill scenarios. Our landscape architects and engineers work collaboratively to satisfy the state and local engineering code requirements while integrating the facilities into the design theme.
A good example is the redevelopment of an existing parking lot in an established office park that was converted to residential townhouses (Montgomery Row). This project will house approximately 162 townhouses and a community park on 10 acres.
The park design provided a unique opportunity to use planted stormwater areas to help frame the design and became part of our layout of arcs within the larger V-shaped open space (shown below). Other solutions allowed us to use stormwater facilities to take up grade and provide permeable pavement within alleys. Such a multi-functional approach to site design synthesizes function and form uniquely for each site.
Micro-bioretention is a multifunctional practice that can be adapted easily for new and redevelopment projects. With this process, stormwater runoff is conveyed to small, landscaped depressions that temporarily store and filter water through a mixture of engineered soils, sand, and gravel. Micro-bioretention provides water quality and quantity treatment, aesthetic value, and can be scaled to meet a site design’s constraints.
Permeable pavements are also effective for meeting a site’s pavement needs and for providing stormwater management treatment. Most notably, they’re useful for pedestrian sidewalks and plazas or for lighter loaded vehicular access or parking. Assuming the soil infiltration rates are acceptable, permeable pavements may be used in both new and redevelopment applications.
Each of these techniques were used in various open spaces throughout the Montgomery Row site. Our design team approached the design such that the stormwater management would provide a visual asset that would illustrate how rainwater is managed on site, how it defines space, as well as provide visual interest.
For example, along the promenade that parallels the public road, where roof runoff is diverted to terraces integrated between the entry steps to each of the town home entrances. The terraced rainwater management features are defined by low, brick walls that also serve as seat walls along the promenade. The plantings are specifically designed to provide visual interest throughout the seasons and to support the critical microbial life within the designed soil profile.
When the soils mature, 1 tablespoon of healthy soils can contain as many as 1 billion microbes. This microbial life will feast on the captured pollutants and convert them to benign substances, a critical step in cleaning the rainwater before it is discharged from the watershed.