See the letter (Brachwitz) or go back to the Drinking Water Quality section.

Key to Map, Sources, and Explanations

The colors are listed more or less from the outside of the map moving inward.

base map          Mail-a-Map Street Map of Simsbury, CT (Harbor Publications, 2004)

(turquoise)       boundary of Stratton Brook Aquifer Protection Area

                          Source: DEP map “Aquifer Protection Area, Simsbury, CT, Jan 2005”

This is a preliminary (Level B) mapping, which is an estimate of the land area from which the Stratton Brook municipal water supply wells draw their water. The Level A mapping, which is not yet available, will delineate the final Aquifer Protection Area. (Water companies are responsible for doing the Level A  and B mapping and submitting the results to the DEP.)

(yellow)             boundary of town-mapped Secondary Recharge Zone

(purple)              boundary of town-mapped Primary Recharge Zone

                          Source: Town map, “Town of Simsbury Aquifer Protection Zones and

                          Areas Served by Private Wells”, updated April 1992, based on US

                          Geological Survey Datum and the Simsbury Planning Department

A recharge area/zone is the area over which rainfall contributes to recharging the aquifer with new water. The contribution may be  in several ways.

     1. Water falling over the aquifer can soak directly down into the groundwater held by the aquifer;

     2. Surface runoff coming from outside the aquifer limits may soak into the ground over the aquifer and reach groundwater underneath;

     3.Water reaching groundwater outside the aquifer limits can then flow underground into the aquifer groundwater;

     4. Rain may fall directly into a body of water or run off into such a body and enter the aquifer from there.

Why the DEP Aquifer Protection Area differs from the town-mapped Recharge Zones is not entirely clear. (Perhaps the Level A mapping, when it becomes available, will resemble the town mapping more closely.) The town mapping was done using field exploration and borings, geophones (which use sound to sense underground geological features), examination of well logs from previous fieldwork, and examination of geological and topographical maps.

(pink)                 limit of the Stratton Brook Aquifer

Source: US Geological Survey publication, Availability of Water from Stratified-Drift Aquifers in the Farmington River Valley, Simsbury CT by R. L. Melvin and J. W. Bingham (1991)

The limit in most cases occurs where the stratified drift (gravel and sand) of the aquifer meets adjacent till and bedrock. (Till is a mixture of particles of all different sizes, from fine clay to huge boulders. Because the small particles fill in the spaces between the larger ones, till allows little movement of water.) In some places the aquifer limit is not precisely defined because in these places it depends on the groundwater drainage divide, which may differ from the surface-water drainage divide above it. Studies to define it more precisely were apparently not done. This uncertainty accounts for the gaps in the pink boundary line.

(blue)                 boundary of areas of high transmissivity

(orange)             boundary of areas of greatest transmissivity

                          Source: same map as used for aquifer limit, above

Transmissivity is related to permeability and vertical cross-section. Pollution reaching these high-transmissivity areas is likely to have the greatest effect on the drinking water, because water and dissolved pollutants move most readily through this part of the aquifer and pollutants thus have less time to be adsorbed or broken down before reaching the wells. In addition, the water company well pumps exert a pull that directs water (and pollutants) towards them; areas close to the wells are influenced by this force more than areas farther away. Low-transmissivity areas near the high-transmissivity areas can contribute pollution to the high-transmissivity areas by surface runoff and by very slow groundwater inflow.            

(green)               boundary of the Ethel Walker property west of Bushy Hill Rd.

                          Source: Simsbury Plan of Development map of Nov. 1994

(black dashed lines)    boundaries of some of the undeveloped town-owned and state-

                          owned land in this area. Not all of it is shown here.

                          Sources: Simsbury Plan of  Development map (Nov. 1994) and Simsbury

                          Open Space map published by the Simsbury Land Trust