The Stafford Source Water System supplies approximately 1 MGD
of water to rural northeastern Connecticut. The source consists of a large,
mostly wooded, watershed basin and three small shallow reservoirs in the
flowline of Roaring Brook. Reservoir No. 4 is a small shallow
impoundment located high in the watershed. Immediately below Reservoir
No.4 is a large, expanding, dairy farm operation. Water quality downstream
of the dairy farm is consistently poor, especially during storm runoff episodes. Reservoir No.3 lies approximately two miles downstream of the
farm. Reservoir No.2 is further downstream, and is the direct source of raw
supply water. Significant water quality impacts have been identified,
including nutrient and organic loads, high coliform counts, color, metals,
turbidity, and bluegreen algae blooms. Water treatment difficulties have
included controlling taste and odor, meeting chlorine demands (especially
during storm runoff peaks), and the formation of disinfection byproducts.
Efforts to identify and implement agricultural best management practices
(BMPs) to control runoff quality have progressed slowly due to private land
ownership and implementation costs.
Small, deep water layer aerators (with biological substrates to
enhance ammonia removal by nitrification) were installed in Reservoirs No.
3 and No. 2. The "indirect impacts" (iron and manganese, ammonia, and
sediment P release) related to high organic loads were significantly
controlled. However, water quality, especially during peak runoff episodes,
remained difficult to treat.
Reservoir No. 2 (the direct to source of raw water) is a shallow
reservoir consisting of two "bays". Roaring Brook (which carries dairy
farm runoff) enters the lower bay, flows through Reservoir No. 2, and
leaves either over the dam or through the supply intake. Approximately
half of the reservoir volume and area lie in the upper bay. A narrow
constriction connected the upper and lower bays of Reservoir No. 2. The
watershed drainage basin which drains directly to the upper bay was
entirely undisturbed woodland. In order to minimize supply water quality
impacts of agricultural runoff carried by Roaring Brook the intake was
extended to the upper bay of Reservoir No. 2, and a scrim-reinforced
curtain was used to separate the upper and lower bays of the reservoir at the
narrow constriction. The intent of this reservoir partitioning was to isolate
the water supply intake as much as possible from the impacts of water
quality in Roaring Brook, especially during storm episodes.
A comparison of water quality in Reservoir No. 4 (above the farm),
Reservoir No. 3 (below the farm), lower Reservoir No. 2, and upper
Reservoir No. 2, identifies the benefits of reservoir partitioning and intake isolation. Total coliform counts were very high at Reservoir No. 3 and
lower Reservoir No. 2 following storms, yet remained low within upper
Reservoir No. 2.
Total phosphorous concentration in surface and over-bottom waters
remained lower in the isolated upper bay, compared to the lower bay which
is exposed to Roaring Brook peak flows. Although total phosphorous
increased as the summer progressed, concentrations were lowest in the
upper bay. Includes figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 600 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 6 |
| Published : | 11/02/2003 |
