Integration of Brownfield Redevelopment and Stormwater Mitigation

8 May

Brownfields include property where redevelopment or reuse may be complicated by the presence (or likely presence) of contamination. Vacant parcels may also be brownfield sites. Redevelopment of brownfield properties often include approaches specifically designed to reduce or eliminate environmental risks to humans and the environment. These approaches include removing contaminated soil or waste materials, treating soils on site, placing a cap or barrier over contaminated areas, performing bioremediation, or conducting monitored natural attenuation.

Most urban communities are required to develop municipal stormwater management programs to control discharge of contaminants from their stormwater and sewer systems. These programs usually require new development and redevelopment projects to implement best management practices (BMPs) that reduce contaminant discharges and control stormwater runoff from reaching surface water bodies. The specific requirements for each stormwater program vary, however, most require or encourage development projects to address stormwater runoff through controls that either infiltrate stormwater before its runoff from a property or provide for the detention and treatment of the stormwater before discharge.

Communities seeking to implement sustainable stormwater management frequently manage runoff by use of rain gardens, bioswales, permeable pavement, and other “green infrastructure” practices. These stormwater infiltration practices often allow accumulated runoff water to percolate into the subsoil, reducing stormwater runoff. Projects that infiltrate stormwater runoff on-site can provide multiple benefits, including decreased stormwater infrastructure costs, increased groundwater recharge, and decreased pollutant loads in stormwater runoff.

Vacant or under-used parcels are often ideal locations to locate stormwater infiltration ponds and constructed wetlands. However, it is important to merge sustainably managing stormwater with brownfield site considerations. Infiltrating stormwater where contaminants are present may mobilize contaminants and increase the potential for groundwater contamination.  However, complete removal of contaminated soils can create a ready-made stormwater detention basin in an urban area.

Successful implementation of stormwater management and infiltration practices at brownfield sites requires careful planning. Stormwater management planning and implementation should be integrated with site investigations, state approvals, the selection of clean-up approaches, and the design and engineering of site improvements. The safe implementation of stormwater infiltration needs to be considered during the early phases of planning for site redevelopment. Locating infiltration practices so that they do not mobilize contaminants requires a collaborative effort by team members responsible for delineating and defining the contamination, remedial engineering, site planning, and site design.

Geography and climatic patterns often cause flash flooding in the West. Increasing pipe sizes and detention capacity of existing stormwater sewers is expensive and does little to improve the overall livability of urban neighborhoods. By implementing creative improvements to stormwater systems, the opportunity exists to reduce the threat and minimize potential flooding impacts. Open space features and park amenities can be created that effectively deal with stormwater quantity and quality issues while creating amenities such as ponds, fountains, pathways, and landscaped areas that enhance neighborhoods and become gathering places for community events and activities. By reducing the liability and cost gap associated with brownfield assessment and potential clean-up activity, private property in urban areas can benefit from integration of stormwater retention and community amenities.

 

Scott Wilson is Vice President of Environmental Services at Ayres Associates. DCI’s 2014 Annual Conference, Vibrant Colorado Downtowns, will feature a half-day Colorado Real Estate Redevelopment Forum on Friday, September 12 to focus on building a stronger awareness of redevelopment trends and tools in our state, and how the public sector can shape redevelopment to drive the community vision.  

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