Groundwater

The most productive aquifers in the Nashua River basin are sand and gravel deposits located in low-lying areas near surface-water bodies. Some deposits along the main valleys of the Nashua River basin can yield several hundred gallons per minute to single wells. Areas of high potential well yield lie along the Squannacook River in Townsend, the Nashua River at Fort Devens, and the Still River in Bolton. Much of the main valleys of the North Nashua and Nashua Rivers below Fitchburg contained glacial lakes, and are underlain by fine-grained lake deposits up to 100 ft thick.

The best known of these lakes was Lake Nashua, which extended broadly over the drainage area of the Nashua River from Boylston to East Pepperell. Lake deposits generally yield less than 100 gal/min to wells, but, if interspersed with coarser deposits, can yield 100 to 300 gal/min.

The basin is underlain by several types of crystalline bedrock. Wells drilled in bedrock for domestic use are commonly 100 to 200 ft deep and generally yield 2 to 10 gal/min. Some wells drilled in bedrock for industrial use, mostly in Leominster, yield 20 to 150 gal/min.