Green Infrastructure

Stormwater runoff, and the pollution and sediment it brings, wreak havoc on our local rivers, streams and creeks. There are effective natural solutions to help manage stormwater runoff. Those solutions ­ including tree plantings, bioswales, permeable pavement, rain gardens, riparian tree and shrub plantings and other native vegetative plantings near and along roadways, parking lots and sidewalks ­ are collectively known as green infrastructure or natural stormwater solutions. Generally, these have been applied as an addition to traditional stormwater infrastructure.

 
Natural solutions use the living landscape to capture, store, absorb, filter and slow the flow of stormwater runoff at the surface – before it enters sewer or stormwater systems and eventually local waterways. However, these solutions require maintenance plans and strategies. Proper maintenance is essential to ensure that projects perform as expected. Just a couple of examples: Maintenance activities for a rain garden include replacing mulch annually, pruning trees and shrubs as needed, and removing invasive species and weeds by hand monthly or at the minimum three times a year. Maintenance for a green roof includes removing weeds by hand, replacing dead plants, removing invasive species, clearing inlet pipes, removing trash and debris, and pruning.

 
Establishing written plans, budgets and procedures are needed to ensure proper long-term maintenance and are critical components to the success of any green infrastructure project. A dedicated source of funding that will allow for a budget capable of covering the costs of maintenance, staff, equipment, and the repair and replacement of green infrastructure on an ongoing basis. Otherwise, the systems will fail. Even with proper maintenance, green infrastructure cannot replace a woodland that was removed to build townhouses or data centers in terms of environmental services and stormwater filtering.
Modern urban drainage and suburban stormwater systems began by whisking the water away at the risk of extreme flooding downstream during larger storms. Methods to control stormwater flow like detention basins were then added to hold the water in place until it could be released safely during larger storm events. Engineered stormwater solutions using nature to replace hard surfaces and help control the flow can improve overall performance of the stormwater system.

 
However, as towns and communities grew, each new development project installed more concrete and other impervious surfaces in place of the softer, natural areas that slow and absorb water. This not only diverted more and more water to the stormwater system, but also removed the natural filtration of soil and plants to treat the mix of contaminants stormwater often carries before it heads downstream.
Fertilizers wash off lawns and end up in the drain. Brakes shed different types of metal. Even atmospheric deposition made up of exhaust from cars, buildings, businesses are sources of contaminants. Plants used in green infrastructure, like switchgrass, are chosen for their tolerance to a wide range of moisture conditions, and their deep roots retain water and nutrients. The soils used in green infrastructure are usually sandy with a bit of organic matter and specifically engineered to help retain contaminants like copper and zinc, both heavy metals commonly found in urban stormwater runoff.

 
Research at Penn State and Virginia Tech has found that the increasing inland salinization from the salt, used to melt snow and ice in the winter on the increasing number of paved roads, parking lots, sidewalks- the built infrastructure, can severely affect the vegetation’s survival and soil’s health, including how well they retain contaminants. According to their research salt replacesthe metals attached to the soil particles and releases them to the water environment. Salt impacts its ability to treat the stormwater and filter the contaminants.

 
Green infrastructure/ natural solutions are not the easy solution to overbuilding. Though they have become the buzz word for the Planning Department. Green infrastructure practices are often designed as infiltration, runoff reducing, and/or vegetation-based practices. Although the use of green infrastructure continues to increase across the country, there is still limited information about the long term functioning of the practices and the operations and maintenance necessary and their associated costs compared to more traditional approaches. This creates a challenge for local governments that are considering incorporating green infrastructure into the suite of practices they use to manage polluted runoff and protect clean water. This is critical when this water is the source water of our drinking water supply.