Effective analysis, design and maintenance of stormwater quality Best Management Practices
As concern for sustainability continues to become more mainstream, it is more important than ever to specify appropriate stormwater quality Best Management Practices. Particularly BMPs that meet permitting requirements while maximizing overall benefits and minimizing total life cycle costs.
Recently, I attended a workshop to catch-up on the latest research on the long-term effectiveness of stormwater quality BMPs and discuss various types of low-impact development BMPs. The Floodplain Management Association sponsored the Stormwater BMPs Workshop, and the workshop team was led by Jennifer Walker, President of Watearth, Inc.
The focus of the workshop was low-impact development, which centers around:
- Emulating natural treatment and storage processes within the site design rather than in larger centralized facilities.
- Redirecting stormwater runoff to other beneficial uses, such as on-site irrigation and groundwater recharge.
Key takeaways from the workshop were:
- Successful LID implementation requires careful consideration of factors such as soil type, groundwater, installed soil nutrient content, plant and soil biology and chemistry, and regional climate.
- Practices that limit on-site erosion and trash influx are important for protecting downstream water quality, and also for extending the useful life of your LID features.
- Manufactured off-the-shelf treatment solutions can buy you consistency in treatment and maintenance, at the cost of the multi-treatment benefits of true “green infrastructure.”
- Studies have shown that when designing a large development (about 200 acres or less) with many similar lots, you can usually analyze the aggregated areas and LID features as a single large site, with minimal difference in the predicted treatment.
- Dry detention basins can be promoted as “mosquito death traps,” because the eggs laid just after a storm will later dry out. (Hey, it’s worth a try anyway).
Jennifer Walker also introduced two new-to-me design tools (both of which are free).
The National Stormwater Calculator allows a user to estimate a site’s hydrologic conditions and the effectiveness of several LID practices. This calculator includes rain gardens, green roofs, infiltration basins and permeable pavement. My favorite feature in this program is the ability to easily compare design alternatives using built-in cost curves that account for LID practices used, new versus redevelopment, site suitability and region.
EPA SWMM is a comprehensive tool for tracking stormwater quality and quantity, and can be applied to small, simple sites and large, complex watersheds alike.
It’s great to get a refresher and learn what new technologies are available. Even better, it was great to network with other consulting engineers and local government water resource personnel.
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