Calais Planning Commission
            Shoreland/Village Boundary inquiry
Gary Root

On June 21, 2007, I walked the overlapping area between the Shoreland and the Village districts in Maple Corner with Larry Becker, the Vermont State Geologist with the intention of identifying the features that control surface and sub-surface hydrology.  Mr. Becker identified a few basic principles for judging the hydrology:

  1. In areas with gently sloped deep homogeneous soils, surface and sub-surface hydrology generally follows the contour of the land.
  1. In areas that are shallow to bedrock, the surface runoff follows the contour of the land and subsurface runoff follows the contour of the sub-layer.
  1. The exact shape and impermeability of a bedrock layer can not be known, but a prediction can be made if sufficient outcroppings can be observed.

The following characteristics are limited to bedrock of the Waits River formation, a layered partially metamorphosed limestone schist, as this is the type of bedrock found in Calais (except for a granite dome in Adamant).

    1. Waits River Schist is limestone which, over time, can be dissolved by the action of water, leaving behind the less soluble silicates (called rotten ledge by well drillers)
    2. Waits River Schist is more permeable with the layering than across the layering.  It forms a more reliable barrier if the layers are nearly vertical or slope away from the protected resource (the Shoreland)
    3. Cross fracturing compromises the impermeability of the barrier

On this walk, Larry Becker examined the height of land approximately midway between the Camp Road and the County Road in Maple Corner. 

The bedrock outcropping along that ridge is sufficiently continuous to encourage some level of confidence that it forms a subsurface barrier subject to the above limitations.

The layering of the outcroppings is nearly vertical to approximately 20º sloping toward the pond – not as good as sloping away from the pond, but still vertical enough to constitute a barrier that is only slightly compromised

There are infrequent cross-fractures, again a slight compromise to the subsurface barrier.

Mr. Becker concluded from his observations that the height of land between the Camp and County Roads does constitute a surface and subsurface water barrier and that, to be conservative in using this as a barrier, a planning body could establish a buffer zone to protect the barrier.  A buffer of 25 to 50 feet seemed sufficient to him.

We then went South of the Worcester Road and walked the similar formation to the power lines.  He identified this as a similarly suitable barrier.