UConn CLEAR is holding a Stormwater Pond Retrofit Workshop that will demonstrate how to retrofit existing dry and wet stormwater ponds and bioretention areas to allow for infiltration and/or better pollutant removal. The workshop will be presented by nationally-known expert Dr. Bill Hunt from North Carolina State University on Monday, July 26, 2021, from 9 am to 3 pm at the Mystic Marriott Hotel in Groton, CT. The workshop will cover: – Introduction and retrofit motivations – Retrofitting dry ponds for volume reduction & pollutant removal – Retrofitting bioretention for volume reduction & nitrogen removal – Retrofitting wet ponds for pathogen & nutrient removal – Field sessions on retrofitting existing structures Workshop description: The Stormwater Control Measures (SCMs) we design today are not the same as the Stormwater BMPs we placed in the ground 20 years ago. As such, lots of our older SCM infrastructure is dated and can be made to work better with simple retrofits. The motivations and types of SCM retrofits will be discussed, with a focus on dry detention, wet detention, and bioretention. The audience will learn that simple, cost-effective retrofits have the potential to greatly improve an SCM’s performance without increasing maintenance costs. In the afternoon we’ll be visiting several sites in the field. REGISTRATION is $25 and covers coffee and lunch Note: This will be an in-person workshop and attendance will be capped to maintain appropriate social distancing!
This program is part of the CLEAR MS4 Support Program, funded by CT DEEP.
It’s well known that rain gardens are great for infiltrating stormwater but people may not realize that they also help destroy common stormwater pollutants. Several studies have found that rather than accumulating pollutants in their soils, rain gardens tend to biodegrade them instead. One study (LeFevre et al., 2011) investigated petroleum hydrocarbon levels in 58 rain gardens in Minneapolis, MN representing a wide range of sizes, vegetation types, and contributing area land uses. The researchers found that petroleum hydrocarbon levels were well below regulatory limits in all the rain gardens sampled. And a tip for future rain garden installers, rain gardens planted with more robust vegetation with deeper roots did a better job at breaking down pollutants than those planted with only turf grass.
A rain garden’s ability to biodegrade pollutants is in contrast to what happens in more conventional stormwater management structures like retention ponds. Retention ponds are often installed with larger developments to receive a large volume of stormwater from impervious areas (ex. houses and roads in a subdivision, roof and parking lot of a Home Depot). Other studies (Van Metre et al., 2009; Van Metre et al., 2000; Kamalakkannan et al., 2004), found that pollutants like PAH’s (polycyclic aromatic hydrocarbons), a type of petroleum hydrocarbon, accumulate in the sediments of stormwater retention ponds. This creates a very expensive maintenance issue for retention pond owners when the time comes to remove and dispose of built up contaminated sediments.
Side note – stormwater can pick up PAHs from dust on pavements treated with coal tar sealants which are commonly used on parking lots, driveways, and playgrounds (but they have recently been banned from use on State and local highways in CT).