To the Editor:

The village should be very careful in permitting more parking at the proposed Stewart’s expansion site. The problem is that most parking surfaces, as well as roofs and streets, are impervious surfaces.

Abundant research (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1257665/) shows that impervious surfaces contribute to the degradation of water bodies. Pollutants accumulate on impervious surfaces and are washed off during storms.

Impervious surfaces prevent precipitation from percolating into soil where the pollutants are effectively filtered. Furthermore, stormwater from impervious surfaces flows more rapidly into streams, making them more susceptible to flooding and to surges that destroy habitat and cause bank erosion.

Some of Altamont’s streams show signs of destabilization from hydraulic surges.

Ecologists have proposed various trigger points for the ratio of impervious surfaces in a watershed but generally, more is worse.  The impact of adding impervious surfaces can be mitigated with:

— Adequately sized vegetated buffers (Stewart’s is immediately adjacent to a stream with virtually no buffer);

— Retention ponds and rain gardens (none shown on the map);

— Green roofs; and

— Sometimes, use of pervious pavers.

It is possible to accommodate commercial growth but it should be properly engineered.

There is a great deal of information for municipalities interested in improving their green infrastructure (http://www.dec.ny.gov/lands/58930.html;  http://www.dec.ny.gov/docs/water_pdf/swdm2010entire.pdf).

A GIS [Geographical Information System] layer for impervious surfaces in Albany County is underway and should be used in evaluating future projects. 

Simon Litten, retired research scientist

Department of Environmental Conservation

Altamont