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Hydrology Report Shows the dangers of developing on the Belmont Uplands.
Cambridge resident and environmental spokesperson
summarizes Horsley and Witten Report.
added to website March 8, 2012
A recent report by the Horsley Witten Group clearly outlines the hydrological case for preserving the Silver Maple forest currently occupying the site of a proposed housing development in Belmont.
The report outlines significant hydrological problems with this proposed development, which are not adequately addressed by the current development plans.
As explained in the report, the removal of vegetation and the installation of impervious surfaces such as rooftops and asphalt parking lots, causes an increase in water runoff; the developer's own drainage report anticipates a 40% increase over natural conditions. Allowing this additional water to drain into the nearby Little river would cause increased flooding during a major storm. Since increasing flooding in a FEMA floodway is not permitted by the towns of Belmont and Cambridge, the developer is proposing to build underground storage containers to temporarily store the excess water during a major storm. After the flooding has subsided, the water would be released slowly over time into the surrounding watershed.
The problem with this solution, according to Horsley Witten's report, is that the groundwater under this particular site is already very close to the surface. During and after a storm, the groundwater levels rise temporarily as the ground soaks up water which is then slowly released into the surrounding wetlands. State regulations require that any underground storage tanks are always at least 2 feet above the groundwater level. According to the report, the current design of these storage tanks will not meet this criteria during a significant flooding event. The report does suggest a potential alternative, which is to construct additional wetlands near the site, which can store and evaporate the additional water. However, that is not part of the current development plans.
The report also highlights the importance of the existing habitat on the uplands that is slated for destruction and the severe negative impacts this development will have on the already poor water quality of the Little River and Alewife Brook, as documented on the Mystic River Watershed Association's (MyRWA) website. Currently the site provides a rare urban home for wild mammals including Coyote, Foxes, Otters and Deer, to name just a few. The forest also serves as a significant habitat and breeding site for birds.
Far from being a NIMBY issue, the preservation of this forest and important wilderness area is a common sense investment into our future health and safety as a community. There are many less flood-prone and less environmentally sensitive sites in Belmont and Cambridge for creating 60 affordable housing units (only 60 of the proposed 299 units will actually be affordable housing). The simple and obvious solution is for the public to purchase this land and add it to the adjacent Alewife Reservation where it can be enjoyed by future generations and can continue to naturally regulate the water cycle in our communities.
Quinton Y. Zondervan