One of the main water pollution culprits in the Neponset River Watershed is street runoff (e.g., water, or "stormwater"). During a rainstorm, water flows over the landscape - over roofs, yards, parking lots, sidewalks, woods, wetlands, ponds, streams and roads. Because so much of our landscape now consists of pavement, concrete or mowed lawns, this "stormwater" flows over the ground for longer than it used to, picking up contaminants, until it eventually flows into catchbasins and is transported, untreated, into streams, where it affects aquatic ecosystems. Previous to all of the development, rainwater seeped into the ground, where it was filtered by the soil, plant roots and microorganisms, before eventually joining the groundwater.

In its travels over the ground, stormwater picks up contaminants such as the following: in yards, it's the chemicals people use, like fertilizers, pesticides, herbicides, fungicides, in addition to items like cigarettes and pet waste; on sidewalks, driveways, roads and parking lots, it's snow- and ice-melt chemicals, pet waste and cigarettes again, sand and litter such as cups, plastic products, fast food containers, etc., and the by-products of our driving around in automobiles.

The contaminated stormwater then flows into catchbasins. Catchbasins are connected via underground pipes to nearby streams or rivers. So, the cigarettes, pet waste, salt, sand, herbicides and oil wind flow with the stormwater, into the catchbasin, along underground pipes and into the stream down the street. 

Another method for cleansing stormwater is to sever the underground stormwater pipes before they reach the receiving stream, and to build a biorentention cell ("biocell") there. 

A biocell is essentially a depression created in the ground that is then filled with a special soil mixture and a combination of plants that will effectively filter out contaminants from the stormwater and tolerate the altering conditions of wet, dry and moist soils - in addition to occasional, short periods of standing water. 

The biocell pictured below is sited along Pine Tree Brook in Milton. The Pine Tree Brook biocells include outlet pipes via which the biocell-filtered water flows under the walking path and into Pine Tree Brook. The filtered water also could seep slowly into the ground to join the groundwater, instead. 

Note that biocells can be planted to look very manicured or more natural. The biocells along Pine Tree Brook are more natural-looking. The construction of the biocells was funded through a grant obtained by a partnership of the Neponset River Watershed Association and the Town of Milton. Learn more about this project here or by contacting NepRWA Outreach Director and Restoration Manager Carly Rocklen at 781-575-0354 x303, rocklen@neponset.org.

NepRWA also worked with Milton to prevent contamination of stormwater in the Pine Tree Brook watershed, through a public education initiative. We implemented a house-to-house informational canvas to educate residents about how to keep stormwater and Pine Tree Brook clean, and we applied decals to catchbasins and tree-filter-boxes.

The project also included installing pick-up-after-your-dog signs and dog-waste-disposal stations. See the pictures below. 

For more information about the Pine Tree Brook stormwater project, contact NepRWA Outreach Director and Restoration Manager Carly Rocklen at 781-575-0354 x303, rocklen@neponset.org or NepRWA Executive Director Ian Cooke at 781-575-0354 x305 or cooke@neponset.org.