Wachusett Dam
From Wikipedia, the free encyclopedia
 Wachusett Dam at Clinton |
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| Official name | Wachusett Reservoir Dam |
|---|---|
| Impounds | Nashua River |
| Creates | Wachusett Reservoir |
| Locale | Clinton |
| Maintained by | MWRA |
| Length | 965 ft |
| Height | 205 ft |
| Construction began | 1901 |
| Opening date | 1905 |
| Geographical Data | |
| Coordinates | |
The Wachusett Dam in Clinton, Massachusetts impounds the Nashua River creating the Wachusett Reservoir. It is 945 feet (288 meters) long and a maximum of 205 feet (62.5 meters) high. Construction started in 1901 and was completed in 1905.
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[edit] Information
This dam is part of greater Boston's water system, maintained and controlled by the Massachusetts Water Resources Authority (MWRA). Its discharge is into the Nashua River. When it was completed in 1905, the Wachusett Reservoir was the largest public water supply reservoir in the world. At that time, the Wachusett Reservoir Dam was the largest gravity dam in the world as well.
| Wachusett Dam outlet | The plaque at Wachusett Dam |
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[edit] Building the dam
The building of the Wachusett Dam and Reservoir at the turn of the century changed the town of Clinton forever. The Metropolitan Water Board selected the south branch of the Nashua River in Clinton as the best site for Boston's new water supply.
Churches, factories, homes, and schools within the valley had to be knocked down or moved. Roads and rail lines had to be relocated; a railroad tunnel and trestle had to be built in order to relocate the Central Massachusetts Rail Line, and over four thousand bodies had to be dug up and moved in the local Catholic cemetery. The project brought thousands of immigrants to the area for work. It proved to be one of the most amazing engineering feats in history. It is still considered the largest "hand dug" dam in the world today.
[edit] Early problems
A static liquefaction flow failure occurred in the upstream slope of the North Dike of Wachusett Dam near Clinton, Massachusetts on April 11, 1907 during the first reservoir filling. The fine sands of the upstream dike shell liquefied and flowed approximately 100 meters horizontally into the reservoir. This caused many Clinton residents considerable concern. However, the project’s Chief Engineer, Frank E. Winsor, assured the townsfolk that everything was okay. This event remains controversial. At least one engineering study claims that the initial failure is a precursor to the dam’s future failure. However, it has now stood for over one-hundred years.
[edit] MWRA water system overview
The MWRA and the Massachusetts Department of Conservation and Recreation (MDCR) own and operate the collection, treatment, distribution, and storage facilities that supply drinking water to some forty municipalities in the metropolitan Boston area. This water system design was based upon the purchase and subsequent protection of an entire watershed. This design assures that the water remains as pristine as possible. However, modern regulations require that all supplies of drinking water be chemically treated regardless of the source[1]. Additions to the MWRA water system throughout its history have resulted in redundancies that allow major sections of the water system to be shut down for repair or maintenance.
[edit] Water flow
Water flows from the MWRA's main storage facility, the Quabbin Reservoir in central Massachusetts, through the Quabbin Aqueduct to the Wachusett Reservoir in and around Boylston and Clinton [2]. Tributary rivers and streams comprising the Wachusett watershed, a 108 square mile (280 square kilometer) drainage basin, also feed the Wachusett Reservoir. At the eastern end of the Wachusett Reservoir, water enters the Cosgrove Tunnel at the Cosgrove Intake. The Cosgrove Tunnel feeds both the MetroWest Water Supply Tunnel (MWWST) and the Hultman Aqueduct. The MWWST starts from the Carroll Water Treatment Plant in Marlborough. The Hultman branches off at Framingham in two directions. The smaller branch, the Weston Aqueduct, empties into the Weston Reservoir in Weston. The main branch continues to the Norumbega Reservoir, also located in Weston[2].
[edit] Redundancy
Water can be treated with chlorine as it leaves the Wachusett Reservoir in an emergency, and again as it leaves the Norumbega Reservoir. This is to provide for a backup to the new water treatment facility, the John J. Carroll Water Treatment Plant, which started operation on July 27, 2005[3]. This plant is of modular design and provides ozonation for primary disinfection, chloramination for residual disinfection, fluoridation, and pH control.
[edit] John J. Carroll water treatment plant
Located at the town lines of Marlborough, Northborough, and Southborough, Massachusetts, this facility replaces the one used previously only for pH control[4]. It comprises four ozone generators with diffusers and five concrete contact chambers with a volume of 11.3 million gallons (42.7 million liters). The plant has a capacity of 275 million gallons (1.04 billion liters) per day, on an average day or 405 million gallons (1.53 billion liters) per day, at peak level. It cost US$340 million[3].
[edit] Electrical generation
The system includes three hydropower stations, with a total capacity of 8 MW[5]. Water released to the Swift River flows through the turbines at Winsor Station below the Winsor Dam. Water transferred from Quabbin to Wachusett can pass either through the turbines at Oakdale or through bypass pipes when flow requirements exceed turbine ratings. Water released from Wachusett into the Cosgrove Tunnel passes through the Cosgrove turbines[2][3].
MWRA power generation
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The Quabbin Aqueduct connects the two reservoirs, and relies upon gravity to accommodate the three separate operational needs. First, diversion of water from the Ware River into the Quabbin Reservoir uses this aqueduct. Second, water transfer from the Quabbin Reservoir to the Wachusett Reservoir, through a hydropower station or a bypass pipe, uses it as well. The bypass valves are non-regulating valves, and when opened, only the head in the Quabbin Reservoir and the physical characteristics of the aqueduct govern the flow. Because the turbines are flow limited, the bypass mechanism permits transfer rates nearly twice as high as are possible through the turbines. Operationally, the single aqueduct fulfills three purposes, but only one operational mode is possible at a given time [6].
[edit] MWRA references
- ^ Safe Drinking Water Act. Retrieved on 2006-12-01.
- ^ a b c MWRA water system. Retrieved on 2006-12-01.
- ^ a b c Water system history. Retrieved on 2006-12-01.
- ^ John J. Carroll water treatment plant. Retrieved on 2006-12-01.
- ^ Electrical power generating plants. Retrieved on 2006-12-07.
- ^ Water system configuration. Retrieved on 2006-12-01.
[edit] References
- http://en.structurae.de/structures/data/index.cfm?ID=s0001117
- http://erp-web.er.usgs.gov/reports/annsum/vol46/ep/04hqgr0076.pdf
