Proposed Rain Garden for the Bridge Street Marketplace
By: friendv3 (friendv3) 2009.05.20

As the Mad River Valley community happily welcomes spring and warmer temperatures trickle into our Vermont valley, we must again revisit the effects of run-off into the river. We all love spending time along the river during the spring and summer, However, as the summer months quickly approach, we also need to consider the cleanliness of the river before jumping in.

In the more urbanized areas of Vermont, particularly Chittenden County, stormwater runoff has become quite a concern in recent years. Though the Mad River watershed does not have the same level of development as those areas, scientists studying the Mad River identified several sub-watersheds where the area occupied by impervious cover is at or approaching levels that have been shown to create water quality issues.

The Bridge Street Marketplace is a diverse collection of businesses located in historic Waitsfield. The dirt parking lot servicing the shops is located adjacent to the river. Due to the location of the lot, sediment and polluted run-off discharges directly into the river at the site. Friends of the Mad River, a local watershed group, was recently awarded grant funding to build a rain garden at the Bridge Street site. The lot is owned by the Historic Bridge Street Condominium Association who has already agreed to the rain garden.

Like any garden, a rain garden can serve many functions while still serving an aesthetically pleasing view to any passer by. Rain gardens are designed to capture and absorb rainwater and snowmelt known as “stormwater runoff”. The garden slows the runoff entering a site, thus controlling the water quality and quantity before releasing it into the landscape (river in this case). When stormwater runs off of impervious surfaces such as parking lots, compacted soil, roofs and roads, it accumulates pollutants such as nitrogen and phosphorus, bacteria from animal waste, oil and grease, and other heavy metals from vehicles. The runoff is then either collected in a stormwater drain that discharges into a lake or river or enters the water source directly.

At the Bridge Street Marketplace site, stormwater runoff from nearby buildings, roads and the parking lot enters directly into the Mad River causing flooding and stream bank erosion. Andres Torrizo of Watershed Consulting and a Bridge Street business member, is completing the design of the rain garden. After surveying the landscape, Andres will design an appropriately sized rain garden for the north end of the lot, where run off is most prominent.“ Runoff from the north end of the Bridge Street Shops parking lot currently drains directly into the Mad River without any treatment, so we would like to route that watershed area into a stormwater treatment system in order to improve the water quality and decrease the volume of runoff before it discharges into the river,” says Torrizo.

Depending on the size of the garden and the surface area of the site (in this case the parking lot is mostly flat) intentional depressions in the landscape can also be designed to absorb excess water and make the most of precipitation and water entering the site. According the Winooski Natural Resources Conservation District, the runoff that is filtered through a rain garden will be treated at a rate 30% greater than that of a typical backyard lawn. Other benefits include slowing potential floods and erosion from the road; decreased need for maintenance and use of fertilizers; increase in wildlife habitat for birds, butterflies and other beneficial insects; provide a great microclimate; etc. Most likely, the rain garden will require very little upkeep, with exception of moderate weeding in the first year and cutting back dead growth annually in early spring.

The garden will consist of various perennial grasses, shrubs and some small trees which will most effectively filter particulates and other pollution from run-off. An example of some of the plant species to consider include, but are not limited to: Goatsbeard (Aruncis dioicus), Purple Leaf Bugbane (cimicifuga ramosa), Royal Fern (osmunda regalis) commonly known as Fiddleheads, Drooping or Pendulous Sedge (carex pendula), Tusock Sedge (carex stricta), Black-eyed Susan (Rudbeckia hirta), etc. A rain garden manual for any homeowner or business and detailed list of plants appropriate for Vermont rain gardens can be found at the Winooski Natural Resources Conservation District website at www.vacd.org/winooski

The proposed rain garden for the Bridge Street Marketplace will be installed by the Friends of the Mad River and local volunteers in late summer 2009. FMR Watershed Coordinator, Caitrin Noel concludes, “"This project will not only directly address a water quality issue, but the site is highly visible making the project a great opportunity to do some education about stormwater. We are just on the cusp of beginning to have issues from stormwater in the Mad River watershed. If people start thinking about stormwater now, and using smart development techniques, we can go a long way in avoiding future problems."


For further information, questions or to volunteer please contact Caitrin Noel at friends@madriver.com