RETURN TO MAIN WATER SUPPLY PAGE

WEST ASPETUCK RIVER WATERSHED
This drainage area appeared on the 1973 Conservation and Development Policies Plan map as the site for a potential water supply reservoir. While all later updates of the state plan continue to recognize the West Aspetuck as a potential public drinking water supply source, the dam proposal was dropped in favor of a piped diversion.

Today, the West Aspetuck River Watershed remains as a Conservation Area on the state plan map section showing New Milford.

ABOVE: In New Milford (NM) the large blue object is a proposed
reservoir on the West Aspetuck River, as shown on this excerpt from
the 1973 State Plan. Later versions of the Plan removed the reservoir,
but maintained the future public watershed designation as shown by
the light green color. The designation extends northerly into Kent.

In 1982 the US Army Corps of Engineers completed its Housatonic River Basin Urban Study. This technical report evaluated the use of the West Aspetuck Watershed for public water supply. The study found that a maximum safe yield of 4.7 MGD from a diversion (via a pump direct from the River, no dam and reservoir) could be obtained.

Costs for various alternatives were generated. The diversion was evaluated for combined use in Danbury, Stamford and then Greenwich. Water would be treated and stored in existing reservoir systems in those communities. The water would be diverted between the months of December and May.

Then a “second alternative plan would include diversion of water only to the Danbury system. The water could be diverted through an 18 mile long, 36 inch pipeline. The plan would include diverting 4.7 MGD to the Margerie and West Lake Reservoirs. The total cost of the plan would be $14.35 million.”

Then in 1986 the CT Interagency Water Resources Planning Board (IWRPB) reviewed potential new surface water supply sites previously identified by the Board. The result was that in 1987 the West Aspetuck River was changed from a potential reservoir to a diversion. A diversion, without the ponding of water a dam would provide, would have a lesser safe yield than the earlier reservoir proposal, and of course a much less disruptive impact.

Photo courtesy of Rick Gottschalk

Notes from the IWRPB decision of 1987 are as follows: “The high water quality and potential safe yield of the West Aspetuck River and the absence of potential sources of contamination in the watershed makes this site desirable. The extensive development within the proposed impoundment and the amount of road relocation required would probably restrict the development of this source as a surface water supply.

We recommend that the Board eliminate the site as a potential surface water supply source but consider it for inclusion as a potential diversion.” As noted, this area remains on the state plan as a potential future water supply source.

Photo courtesy of Rick Gottschalk

Designation of the West Aspetuck as a long range future water supply resource was endorsed by the Housatonic Water Utility Coordinating Committee in its 1988 plan entitled "Integrated Report for the Housatonic Water SUpply Management Area.

It is interesting to note that today, the entire watershed of the West Aspetuck River receives special notice within Section 2.9 of the New Milford, CT Inland Wetlands and Watercourses Regulations.

According to the regulations "Regulated area means any wetland, watercourse or the adjacent upland area as follows: within two hundred (200) feet of the ordinary high waterline of Candlewood Lake, the east or west branch of the Aspetuck River, the Still River, the Housatonic River or watercourses within the West Aspetuck River watershed (italics added), within one hundred (100) feet of the ordinary high waterline of any other watercourse, or within one hundred (100) feet of any wetlands which ever is greater."

The regulated area for scrutiny is thus set at a high two hundred feet from all tributaries to the West Aspetuck River, in contrast to 100 feet for most other streams.

As a technical note, the potential point of diversion for water supply has never been precisely identified, but it would be upstream from the confluence of the East and West Aspetuck Branches and thus north of low lying Boardman Road, the Century Enterprise Center and adjacent areas.

As the southernmost point for its surface drinking water supply classification, CT DEP uses a point on the West Aspetuck 0.5 mile north of the Housatonic River’s bank, northwest of the Century Enterprise Center.

Photo courtesy of Rick Gottschalk

Land cover change for 1985-2002 on a map of the combined East and West Aspetuck Watersheds is also of interest.

The following overview was developed for the HVCEO in 2006 by Don Smith of Roald Haestad of Waterbury, CT:

"The West Aspetuck River is a Class AA stream with good water quality and has been considered as a future water supply source for many years. The State’s 1973 Plan of Conservation and Development identified a potential reservoir site on the West Aspetuck River just above its confluence with the East Aspetuck River. Although the reservoir has been removed from the state and regional plans, the watershed has remained.

The West Aspetuck River has a tributary watershed of about 25 square miles. For a reservoir, based on an approximate safe yield in New England of 0.7 MGD per square mile (assuming adequate reservoir storage was available) the available water during a 100-year drought would be 17.5 MG. That is a very substantial yield and could serve the entire region for many years.

The catch, however, is the storage; without the reservoir there is no storage and the safe yield would just be the minimum flow in the river, which would be negligible during a drought period when the water would be needed most. The storage to provide 17.5 MGD would be at least 200 million gallons per square mile or 5 billion gallons. The reservoir assumed in the States 1973 Plan would have been much smaller than 5 billion gallons and the yield proportionately less.

The Corps of Engineers evaluated the feasibility of developing the West Aspetuck River for water supply in 1982 as a pumped diversion. Their estimated yield was up to a maximum of 4.7 MGD, and the locations of the storage were as far away as Danbury, Stamford and Greenwich. The estimated costs for diverting the water to Danbury’s West Lake and Margerie Reservoirs was $14.35 million in 1982, and included 18 miles of 36-inh pipe. The cost now would be twice that just for the pipeline, without even considering the energy costs for pumping.

United Water Connecticut, Inc.’s New Milford system has divested itself of its reservoir system. The reservoirs were very small and the yield was inadequate for the system. The Safe Drinking Water Act requires expensive filtration of all surface supplies, which made continued operation of the reservoirs uneconomical. The water system is now served entirely by wells.

The end result is that it does not appear practical to develop the West Aspetuck River for water supply because there is no reservoir in New Milford to store the water. And development as a diversion to existing reservoirs does not seem feasible at this time."

In 2006 a spokesman for the Intergovernmental Policy Division of CT OPM, Planning Specialist Jeffrey Smith, stated in a letter to HVCEO that development of the West Aspetuck watershed for drinking water purposes would be problematic at this point, but such use is not impossible and no formal action has ever been taken to remove the "potential water supply watershed" designation from the state plan.

"Given the situation with regard to drinking water supplies in your part of the state, OPM has had no compelling reason to remove this watershed from its protected conservation designation."