EVALUATION OF GROUNDWATER RESOURCES IN THE TOWN OF CRAFTSBURY, NORTHEASTERN VERMONT USING BEDROCK, SURFICIAL, AND TOPOGRAPHIC MAPS
The marble-rich lithologies directly to the east of the RMC have been eroded to form a broad depression in which the Black River and a number of elongate N-S lakes are found. Uplands composed of pre-Silurian and Silurian-Devonian metamorphic rocks are located to the west and east, respectively, of the Black River Valley lowlands.
Uplands are primarily underlain by dense silt- and fine-sand-matrix glacial till. Till is thin (<20’) on hilltops and bedrock outcrops are abundant. Striations and grooves indicate ice motion of ~170-195°. Scattered ice-contact sand and gravel deposits overlie till in places. Glaciolacustrine deposits are common below ~1120’. Probable delta deposits are found at ~1120’.
There are 328 accurately located groundwater wells in Craftsbury and 96% (n=315) were completed in bedrock. Wells in Silurian-Devonian bedrock have slightly higher average yields and total depths (13 gpm; 267’) than those in pre-Silurian bedrock (10 gpm; 259’). Surficial wells (n=13) have average yields of 40 gpm. Preliminary analysis suggests that the elevated yields of some bedrock wells may be related to the presence of thick, saturated, and porous surficial deposits that overlie the bedrock.
Further analysis seeks to correlate well yields with other factors such as fracture domains, topographic slope, proximity to water bodies or lineaments, and drainage area(s).