Under the Environmental Protection Agency's permitting requirements in the Clean Water Act, municipalities must reduce runoff volume and pollutants in the municipal separate storm sewer systems and combined sewer outfall stormwater discharges. Green stormwater infrastructure (GSI) is an approach to reducing pollutants and removing overflow of stormwater discharge. It utilizes natural processes, plants, soils, and hydrologic modifications to treat the discharge to restore and mitigate flood damage.
Funding for a Solution
One way municipalities and major metropolitan areas are funding the implementation of green stormwater solutions is by instituting fees. They analyze impervious surface area on properties and set a fee based on the size. The fees are applied to the impervious area that is created from a new construction project and to existing impervious cover.
Many combined sewer systems that exist today were created in the late 1800s or early 1900s due to health concerns over the lack of sanitary facilities. Now, during storm flow runoff events, stormwater discharge is mixed with sewage discharge, resulting in tremendous impairment to water quality and negative impacts on streams across the country. These outdated systems need to be replaced or upgraded, which requires a great amount of funding and work. The fees within these metropolitan areas are a fair solution to solving stormwater issues by funding the implementation of GSI.
Bumpout bioswale: This green stormwater infrastructure tool is used street-side to capture and filter stormwater runoff.
The various GSI techniques that can be utilized include blue roofs, green roofs, rain barrels, and planter boxes, which detain stormwater. Subsurface storage and infiltration systems underneath sidewalks can be utilized along with permeable pavements to detain and infiltrate runoff where subsurface conditions and suitable soils permit. Along streets, right-of-way bioswales, curb extension areas, and curb bumpouts use bio retention systems that have modified soils and plants that slow, filter, and infiltrate stormwater flows. Rain gardens, stormwater wetlands, stream daylighting, and restoration-floodplain reconnection also work to provide reductions in stormwater and improve water quality. These approaches all work to reduce the volume of stormwater that enters the sewer system, reduce the maximum or peak flow rate, and improve water quality.
Bio-retention basin: This green stormwater infrastructure tool is a landscaped depression used to slow and treat on-site stormwater runoff.
It Takes a Team
The key to applying various GSI techniques is to fully characterize and verify what is occurring within that system. The challenge is looking at each site and watershed area and identifying the alterations that have historically occurred, then determining what is the best solution or the best series of solutions. I've had experiences from coastal areas to mountainous landscapes, as well as various urbanized watershed types. They all have different drainage characteristics and response times. To fully and completely characterize a site it takes a multidisciplinary team consisting of surveyors, biologists, soil scientists, historians, archaeologists, engineers, hydrologists, and designers. Working together the design team can determine the best solutions and apply the appropriate stormwater management practice.
Climate change and severe weather events are creating opportunities for integration of infrastructure development, planning, and water/stormwater management. Our country does a good job of infrastructure planning already, incorporating the water resource aspect is the key to future solutions of water-related issues.