Green space & bioswales lead to smaller detention ponds & bigger cost savings
The design of a 440,000-sq-ft aerospace manufacturing facility in Loves Park, Ill., required a coordinating exterior design. Collaborative efforts of contractors, landscape architects, and engineers who took part in the project design and construction made this possible. The $250 million Rock Cut Campus for Woodward Inc., an international aerospace parts supplier, was built to accommodate future production needs and employs approximately 350 team members. The campus sits on 75 acres, of which more than 20 acres were developed with impervious surfaces consisting of paved parking lots, roads and the building footprint. The campus also offers bike and pedestrian trails linking to recreational paths of the adjacent 3,092-sq-ft Rock Cut State Park, which is home to abundant wildlife, grasslands, wooded forests and lakes.
Many traditional construction projects employ standard storm water management practices dictated by code, which can include large areas of impervious paving, curbs and gutters that channel storm water through underground piping and infrastructure to large detention ponds, rather than developing environmentally friendly solutions. To maximize aesthetics while minimizing the costly and unseen underground infrastructure used on the campus, Woodward looked to Fehr Graham’s landscape architects to assist in developing a storm water management solution that was cost effective and aligned with the aesthetic brand they wanted for their facilities.
The design team identified options capable of filtering and transporting runoff from the 20 acres of impermeable surfaces. It was important to identify solutions that would best integrate creative storm water management strategies and incorporate more green space, trees and vegetation. The project goals were to design a solution that would help the Rock Cut Campus site blend in with the surrounding natural landscape of Rock Cut State Park, reduce the number of inlets and belowground piping associated with the collection and transport of storm water runoff, and provide a source for onsite irrigation.
Collected storm water is used in onsite water features like fountains along the employee outdoor patio.
Early on, it was determined that the building pad should be positioned on the highest point of the site to direct rainwater away from the manufacturing facility and maximize the conveyance of storm water by gravity through bioswales. The challenge was to ensure the capture and transportation of the large amount of runoff from the building while minimizing the use of traditional underground infrastructure. The landscape architects suggested functional landscaping, extensive use of existing green space and bioswales, and smaller detention ponds for settlement and reuse.
The Rock Cut Campus utilizes functional, low-maintenance native and adapted landscaping that also is welcoming and appealing to employees and visitors. Ornamental plants are more prevalent around the building and at entrances, adding aesthetics and helping utilize and infiltrate rainwater. Dry creek bed features are incorporated into the landscape to channel and collect storm water that is reused and celebrated through onsite water features, including fountains and bubblers located in the outdoor patio for employees to enjoy during working hours.
To minimize the development footprint and break up larger areas of pavement, major elements in the design included the extensive use of green space and incorporating bioswales—islands of green space placed strategically throughout paved surfaces. These large-scale infiltration opportunities are used to capture runoff, promote infiltration, improve water quality and transport excess runoff. The property has more than 1 mile in combined length of bioswales, which occupies 2.5 acres in area and serves multiple purposes, including:
- Filtration. Storm water runoff from the paved surfaces enter the bioswales through gradual slopes. Runoff is absorbed through multiple layers, which filter contaminants and pollutants as the runoff makes its way to the subsurface. Native and adaptive vegetation and trees are planted throughout the bioswales, serving to naturally filter further contaminants present in surface runoff. Tree and plant roots also improve soil structure and increase permeability of storm water into the ground. While some plants are used to take up contaminants in the soil, most of the filtering qualities of a bioswale occur in the upper layers of the soil where beneficial microbes and soil bacteria can break down contaminants picked up by storm water running off parking lots and roads. Studies have shown that bioswales can reduce pollutant loading by up to 95%.
- Transpiration. Trees and deep-rooted native plants throughout the campus take up rainwater in their roots and leafy canopies, hold it and give it back as oxygen through the process of transpiration. It is estimated that a single medium-sized tree can take up more than 2,000 gal of rainfall per year. This process helps further reduce surface runoff.
- Infiltration. The 20-ft-wide bioswales encourage infiltration throughout the paved surfaces, further reducing the amount of runoff. The presence of gravel and engineered soils promotes efficient storm water infiltration of storm water into the subsurface.
- Cost-effective. Utilizing green space and incorporating bioswales is an efficient and cost-effective solution. Typical cost savings can range from 15% to 80% less than conventional development by having fewer storm sewer piping, structures and paved surfaces, and a smaller storm water detention area. The savings of minimizing expensive and unseen underground infrastructure can be reallocated to develop a visually appealing and environmentally friendly site design.
- Aesthetics. Bioswales create an attractive visual to paved surfaces by incorporating native and ornamental perennials, shrubs and multi-stem trees.
Reaping the Benefits
With sufficient infiltration and runoff reduction, a large detention area was not needed to treat storm events. The Rock Cut Campus detention area is far smaller (two small ponds) and less costly than a conventional storm water management strategy. Excess runoff from bioswales and other green spaces, which has been filtered to reduce contaminants and pollutants, is transported to the detention ponds for storage to provide a source for site irrigation using off-the-shelf technology.
Incorporating more green space and vegetation throughout the property has provided added benefits—including temperature regulation—to the Rock Cut Campus and the surrounding environment. Those elements help avoid the Urban Heat Island phenomenon, which is caused by modern development when large areas of dark paving and rooftops absorb heat and increase the annual mean daytime temperature of urban areas by as much as 5°F above undeveloped rural land. Temperature variation can be even more pronounced at night, because the built environment acts as a heat sync that does not cool as quickly as the vegetated landscape. Increased temperatures can affect the larger community through increased peak energy demand and reduced air quality. By breaking up larger areas of pavement with green space, bioswales and tree canopy, Rock Cut Campus is mitigating this issue.
Woodward’s Rock Cut Campus utilized creative storm water management solutions, consisting of large-scale infiltration opportunities, and abundant vegetation and trees. Every property is unique, and storm water solutions for each property also should be unique. Reacting to storm water regulations and ordinances by relying on conventional infrastructure is not always the best solution for the client, the environment or the community. Bill Schmidt is landscape architect for Fehr Graham. Schmidt can be reached at [email protected] or 815.394.4700.