By: John Norris, RLA; Featured in the Spring 2012 issue of Colorado Real Estate Journal
May 1, 2012
Introduction to LID
Being green doesn’t stop at a structure’s four walls, but often times “green building” is focused on just that - buildings. Site design is critical to any successful green building project, because it lessens development impacts on the local environment’s natural systems. One method of site design that has proven successful in the Denver Metropolitan area is Low Impact Development, or LID. LID has many advantages over conventional site design, because it can lower site infrastructure costs while increasing the environmental health and aesthetic beauty of a project.
LID is a multi-faceted engineering design and land planning approach that maintains and conserves a site’s pre-development hydrology and natural systems. When implementing LID, stormwater management is achieved through directing runoff from impervious surfaces, like parking lots and roofs, to small-scale grassed or landscaped areas. These areas are often referred to as bio-swales, rain gardens, and on-site infiltration basins. They are utilized to slow runoff and provide treatment through filtration, settling of sediment, and biological uptake of pollutants. The landscaping included in these areas also offsets the heat island effect and creates wildlife habitats.
There are many advantages to implementing LID on your site. Most notably, LID can be cost effective in the design and construction of the stormwater management system. LID can potentially eliminate costs for grading and land clearing, reduce costs for materials, and reduce long-term maintenance costs.
Because LID focuses on emulating the pre-development condition of a site, there are many environmental benefits as well. Headwater streams that may be vulnerable to degradation from erosive storm flows and pollutants from developed areas are protected. Wildlife and bird habitats are maintained, and limited grading reduces the introduction of noxious weed species.
Case Study: Adams County Government Center and Natural Park
A great example of LID here in the Denver Metropolitan area is the new Adams County Government Center and Natural Park. The site is located at the crossroads of Highways I-76 and E-470. This 90-acre campus is home to all Adams County offices and has an adjacent natural park.
Norris Design’s team members played a key role in developing the site plan and drainage plan for the project, which followed LID principles. A site design concept was developed to allow the southern and eastern edges of the property to become semi-passive constructed wetlands. This key concept allows the campus to return clean water back to the regional watershed through natural processes which occur in eight constructed wetland cells. The wetland cells cascade through the watershed and act as a natural buffer from the nearby highways. They also provide desired urban wildlife habitat, natural landscape, and opportunities for regional trail connections.
Norris Design worked in tandem with Gensler and Civil Arts Drexel, to further develop the LID concept by including porous landscape detention, rain gardens, and a green roof to demonstrate other semi-passive ways to recycle effluents on the site. “LID is easy to integrate with the landscape, and is now more important than ever because of the increasing costs of infrastructure and public focus on sustainable development”, said Aaron Hayne, a Senior Associate at Norris Design who has incorporated these landscape elements in many projects.
Norris Design provided oversight for the porous landscape detention, constructed wetlands, rain gardens and green roof. The first two constructed wetland cells were a challenge to develop due to a high degree of effluent being discharged and its resultant algae growth in the pond. The team was able to overcome these challenges by dewatering the existing pond and allowing the wetland plants to be germinated separately prior to planting and filling the cells.
The result of this effort is a successful example of LID. The Government Center and Natural Park provides ample stormwater runoff mitigation, removes pollutants through filtration, and provides a buffer to the nearby highways. The Natural Park is connected to the wetland cells and retention ponds that create a preserve for native birds and wildlife. [Click for more images of Adams County Natural Park]
Expectations of LID
Although LID has proven successful on a variety of levels in our local market, adjusting to change in the built environment takes time. Many Coloradoans have enjoyed decades of lush turf landscapes that use large quantities of irrigation water. These high water-use surroundings have an immediate aesthetic affect, but the environmental impacts are lasting and significant.
When choosing to implement LID, an owner must understand that a naturalized landscape takes more time to mature, but the benefits are worth the wait. A naturalized landscape, such as the one developed at the Adams County campus, lowers maintenance costs, uses less water, and uses less fuel (from maintenance vehicles). The regional landscape character is protected, along with open space and natural systems.
Implementing LID on your project is an opportunity to enhance community health, protect the local environment, and lessen impacts to natural water systems and streams. It is easily incorporated into urban projects because the features are small-scale and integrated with the landscape. Consider implementing LID on your next project, and see what a balanced approach to green building – both buildings and site design – can do for your triple bottom line (people, profit, planet).