Dig This With Deb

A column to tell people about the building process by Deb Blanchard


Watching the rain fall today (and almost every day this week!) makes me reflect on a conversation recently with our landscape architect Catie Martin and civil engineer Jim Devellis, both from the firm of Devellis Zrein, Inc.  They met recently with Committee Chair Carol Ambrozy and myself during a site visit to monitor the library project.  Two of the important green features on our project were discussed – the detention pond and the rain garden.

The rain garden will be located in the middle of the parking lot.  Besides giving a green feel to the parking section, this planted area performs an important drainage function.  With impervious pavement in the parking lot and storm water runoff from Main Street, excess water and pollutants in the form of trash, debris, and materials used in salting and sanding roads during snow season can be a problem.  Instead of flowing into a storm drain or the river or collecting on the pavement, the rain garden drainage is designed to hold the runoff water while it soaks into the ground.

Native plants and mulches in the rain garden are specially chosen to combine natural processes to filter the pollutants.  A series of soils and gravel layers are also used to allow quick infiltration of the water through the soil so that mosquitoes cannot complete their breeding cycle.  Plants also return water moisture back into the air through a process known as transpiration.

The library roof has been designed to pitch rain water into a drainage system that flows into pipes that come down the side of the building, go underground and connect into the drainage for the rain garden.

As for the detention pond or basin, earlier a patron had corrected me when I talked about our detention pond saying I must mean ‘retention’ pond.   Being unsure, I asked Jim Devellis and he kindly responded to me with the following:

“Your pond ... A detention pond “detains” the water because it comes in fast and leaves slow but at the end of the day it drains dry. Kind of like filling up the bathtub quick with the drain open. It is safer, has no potential for stagnant water and mosquitoes and is more appropriate for this site.

A retention pond “retains” the water and when new water comes in, it pushes out the old water but at the end of the day it stays a pool of water.  Good for sites with poor soil (like clay). Not appropriate for this site.

Some quick points when you are trying to describe the detention pond ... it slows the water down before it goes into the river to minimize potential flooding downstream, the plants that we choose take up or absorb the pollutants as they pass over them, the plants offer food for the wildlife, the sandy bottom allows groundwater recharge and because there are no mechanical filters or moving parts like some water quality devices, it is maintenance free other than minimal plant care/ mowing etc.”.

These green features also contribute to our LEED certification under “Site Development: Protect or Restore Habitat”. This credit promotes biodiversity by encouraging projects to protect or restore the site with native species.

The library is also pursuing two grants that will further rehabilitate the back lot as a green space for passive recreation and educational opportunities to learn more about the beautiful Miller’s River that flows past our library. As we were walking around the site, Jim Devellis leaned against the back retaining wall listening to the rushing sound of water and remarked ‘You just can’t buy this sound like it is here in its natural form. I could sit here all day.’  How lucky we are to have this right in our own downtown.

In picture: (l to r) Catherine Martin, landscape architect and Jim Devellis, civil engineer, both of Devellis Zrein, Inc., discuss the detention pond area with Chair Carol Ambrozy.