Harrisville’s Historic Town Spring

The Town Spring in Harrisville is a local treasure. Many local folks rely on the spring as a source of fresh drinking water. It produces 20 gallons-per-minute of clear, fresh water, and apparently has done so for the past 150 years. The current spring output on Skatutakee Road is located at the same site as the water tanks that supplied the railroad steam engines in the 1800’s and early part of this century. [Please note: the spring is not maintained or overseen by the Town, and water quality is not assured.]

 

Our 2013 Natural Resource Inventory underscored the importance of this public water supply to the people of Harrisville. Since this past summer, the Conservation Commission has been gathering information about the source waters of this spring. Some of the more important findings are that this spring is served by an “overburden aquifer”, i.e.,  glacial deposits of sand and gravel that extend south from the spring all the way up the flank of Beech Hill. Unlike typical “stratified drift” aquifers, the Town Spring aquifer does not have a protective layer of impermeable clay above the sand and gravel layers. Instead, the 20’ to 100′ deep sands and gravels of this “overburden aquifer” are exposed directly to the surface. This may render the Town Spring aquifer more vulnerable to surface pollution that may arise from development.

The Conservation Commission is exploring ways to protect the Town Spring aquifer, which covers a substantial area on both sides of the Dublin Road and up the flank of Beech Hill. We commissioned an engineering firm (Nobis Engineering) to provide a detailed map that outlines the aquifer (blue line) and the vital recharge areas that most directly feed the town spring’s waters (red line).

View the Town Spring Maps in full scale

Explanations for Aquifer Protection Zones shown on Harrisville Town Spring maps
New Hampshire, October 2014

Background:

An aquifer can be defined as “a formation, group of formations, or part of a formation that contains sufficient saturated permeable material to yield economical quantities of water to wells and springs” (Driscoll, F. G., 1986, Groundwater and Wells, Second Edition). A previous study of the Skatutakee Lake spring by ENSR in 2007 concluded that most or all of the water that flows from the Skatutakee Lake spring comes from glacially deposited overburden (as opposed to bedrock), in this case, sandy glacial till. The conclusion was based on well records that indicate that bedrock is 30 to 100 feet deep in the area and on other factors.

Explanations of Delineated Areas on Map:

Purple Dashed Line Skatutakee Lake Spring Direct Recharge Area: This is the area that likely provides recharge to the spring, based on the assumption that shallow groundwater flow occurs in roughly the same direction as surface water flow and is controlled by topography. The purple dashed line delineates the topographic drainage basin above the spring.

Red Line 175 Foot Buffer Around Recharge Area: Acknowledging the possibility that groundwater recharging the spring may not come from exactly the same area as the surface water drainage basin, a buffer is added around the direct recharge area. The 175-foot distance for the buffer was selected based on estimated flow from the spring during the ENSR study. On 1/24/07, it took less than one minute to fill a 7.5 gallon container from the spring outfall near the road. On 9/20/07, ENSR visually estimated the flow from the spring at 20 gallons per minute (gpm). For a 20 gpm community well, the New Hampshire Department of EnvironmentalServices rules specify a Sanitary Protective Area setback of 175 feet. This distance was selected as a conservative setback or buffer for the spring recharge area.

Blue Line Skatutakee Lake Spring Aquifer: The blue line delineates the aquifer in which the Skatutakee Lake Spring is located, in the professional judgment of Nobis Engineering Senior Hydrogeologist, James H. Vernon, Ph.D. The aquifer is characterized by thick (greater than 30 feet) overburden deposits characterized by sandy soils (mapping obtained from the publicdomain GIS database, NHGRANIT) derived from sandy glacial till deposits. The spring occurs near the northern (downhill edge) of the mapped aquifer. The aquifer occupies much of the hillside south of Skatutakee Lake, extending to Beech Hill. The criteria used for delineating the boundaries of the aquifer are overburden thickness, topography, and mapped soil type. The western boundary of the aquifer, along the shore of the lake is marked by a sharp decrease in overburden thickness from 30 or more feet to 12 feet or less, as evidenced by well records and the presence of a bedrock outcrop. The eastern boundary of the aquifer is characterized by a change in topography (drainage east to Nubanussit Brook) and a change from sandy to mucky soils.