Green stormwater infrastructure (GSI) can have significant environmental and operational benefits, but to fully gauge the success of GSI projects — and to meet reporting requirements — it’s important to incorporate specific monitoring strategies to assess functionality, enhance performance and determine maintenance frequencies.
There are a variety of GSI monitoring strategies that can be implemented, but a central component for a successful monitoring program is tailoring the strategies to the GSI owner’s unique needs, expectations and available resources.
The first step in selecting a monitoring strategy is evaluating what type of monitoring the owner needs. Is the owner reporting certain information to a governing body or entity? Does the owner have its own expectations for how to quantify performance?
The next step is determining which strategies will be most cost-effective by evaluating a given test or procedure based on the amount and type of data it will collect. This information is then weighed against how much time it will take to collect and analyze the data. This allows the owner to institute monitoring programs that best reflect individual needs and resources.
For instance, the City of Kansas City, Missouri, implemented several monitoring strategies to assess GSI demonstration projects constructed as part its Consent Decree with the Environmental Protection Agency to reduce combined sewer overflows. Project monitoring began by assessing the infiltration rate as a performance metric. This metric was driven by the city’s requirements for duration of ponded water. In addition, when the monitoring began, most completed projects involved soil, making this an effective strategy. Our team was able to make recommendations and suggestions as each GSI location came online to determine the most effective monitoring strategy for a given project.
However, the monitoring efforts for the city of Omaha’s GSI projects were based around the city’s objective to demonstrate how natural-like systems reduce stormwater runoff and pollution entering the local water bodies. The GSI monitoring program for Omaha included components to quantify natural processes and measure water quality. Our team evaluated monitoring tests and equipment that would allow the city to understand these complex systems and collect metrics that could be used in its annual stormwater reporting.
Regardless of the unique needs of each municipality, the goal of all monitoring strategies is to determine how well a GSI project is performing, if the existing system can be optimized and whether there is room for improvement on future projects.
These monitoring strategies can also evolve time. In Kansas City, assessing the infiltration rate began with a labor-intensive test that can take up to six hours, but this year our team has incorporated some abbreviated processes and automated equipment that still deliver desired metrics.
GSI monitoring can take considerable resources, but if monitoring strategies are chosen carefully to best meet the individual needs of the owner, they can also deliver valuable feedback about how these innovative strategies are performing in the real world.
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