Water Quality Considerations

Drinking Water Quality

The land belonging to Ethel Walker School (EWS) under consideration for either development or conservation sits atop a large, high quality water aquifer (Stratton Brook Aquifer).  It provides 73% of the water for 14,000 Aquarion customers in Simsbury, Granby and East Granby (see the Aquarion Site).  Additionally, it provides 100% of the water to many private wells.  Runoff from the Ethel Walker Land goes directly into this water supply.  Figure 1 displays detailed aquifer mapping information.  Figure 2 displays Simsbury's mapping of the Aquifer Protection Zone (APZ) around the Stratton Brook Aquifer and the EWS property under consideration.

Fig. 1 Aquifer Mapping Detail and Sources

Aquifer Protection
Fig. 2  Simbury's mapping of the Aquifer Protection Zone (CLICK TO ENLARGE).

In a Community Source Water Assessment Report issued by the Drinking Water Division of the Connecticut State Department of Public Health on the EWS well (Gravel Pack Well 99), it was recommended that the school “support and encourage the acquisition of open space land within the source water area.”

Another report (on the Stratton Brook Wellfield belonging to Aquarian Water Company) notes that “more than 50% of land for this source water area is undeveloped, which could present a risk if developed inappropriately.” Sources of potential risk include “residential properties that store or use hazardous materials like petroleum products, solvents or agricultural chemicals.”

Stormwater runoff is another important consideration. During construction soils are exposed to rainfall that increases erosion and sedimentation. Once roads and homes are constructed, the now impervious cover leads to increased runoff, reduced groundwater recharge, and a decrease in natural mechanisms of pollutant removal. Urban stormwater runoff typically contains elevated concentrations of nitrogen and phosphorus that are most commonly derived from lawn fertilizer, detergents, atmospheric deposition, organic matter, and improperly installed or failing septic systems. Nutrient concentrations in urban runoff are similar to those found in secondary wastewater effluents (American Public Works Association and Texas Natural Resource Conservation Commission).

Impervious cover on undeveloped land is near 0 percent. Single-family residential areas range from 25 to almost 60 percent total imperviousness. When impervious cover in a watershed reaches between 10 and 25 percent, ecological stress becomes clearly apparent. Beyond 25 percent water quality becomes degraded, and biological diversity decreases (NRDC, May 1999).

Polluted runoff and development-related contamination are the largest threats to water quality.  Once the quality of our water is adversely affected, the current good quality will be difficult if not impossible to buy back.