Saint Lawrence River HVDC Powerline Crossing
Encyclopedia
The Saint Lawrence River HVDC Powerline Crossing is the crossing of Hydro-Québec
's Quebec-New England
HVDC transmission line over (and later, under) the Saint Lawrence River
between Grondines and Lotbinière
, Quebec
, Canada
. The crossing is very remarkable, as it was first implemented as overhead crossing, which was later replaced by a cable tunnel.
This unusual and very expensive way was chosen as Hydro-Québec wanted to complete the transmission line in time, which was only possible with an overhead crossing of Saint Lawrence River. However, due to the negative visual impact of the large towers of the overhead crossing by the local population of Grondines and Lotbinière, it was decided to build a cable tunnel under the river, although this made the project more expensive.
In 1988 construction work for three artificial islands in the Saint Lawrence River, which were connected with jetties
to the mainland as construction for the pylons of the overhead crossing started. Between July 1988 and spring 1989, 20,000 truck loads of 400000 tonne were transported.
In 1989 the towers of the temporary overhead line crossing
were erected. The suspension pylons on each side of the waterway were 140 metres (459.3 ft) tall to ensure the required clearance. Building these towers required five months construction time and approximately 40 specially trained workers.
At the end of 1989 the overhead crossing, which consisted of five towers, was completed.
In spring 1989 work on the 3954 metres (12,972.4 ft) long cable tunnel started, which took six months of drilling in two 12-hour shifts. The average drilling rate was 27 metres (88.6 ft) a day, but achieved in horizontal sections over 90 metres (295.3 ft) a day.
On March 26, 1990 the tunnel boring machine
reached the surface 8 centimetres (3.1 in) away from its target point. Later the tunnel was covered with concrete, and troughs for the cable support were installed.
On November 1, 1990 the HVDC transmission line went in service with a transmission rate of 1200 MW, which was increased to 2250 MW on July 1, 1991.
In 1992 the overhead line over the Saint Lawrence River, including the artificial islands and the jetties were dismantled. Portions of one of these towers would later be used as part of the observation tower at La Cité de l'Énergie
in Shawinigan. The costs for dismantling was $16 Million (CDN
).
Hydro-Québec
Hydro-Québec is a government-owned public utility established in 1944 by the Government of Quebec. Based in Montreal, the company is in charge of the generation, transmission and distribution of electricity across Quebec....
's Quebec-New England
Quebec - New England Transmission
The Quebec – New England Transmission is a long-distance high-voltage direct current line between Radisson, Quebec and Sandy Pond in Ayer, Massachusetts...
HVDC transmission line over (and later, under) the Saint Lawrence River
Saint Lawrence River
The Saint Lawrence is a large river flowing approximately from southwest to northeast in the middle latitudes of North America, connecting the Great Lakes with the Atlantic Ocean. It is the primary drainage conveyor of the Great Lakes Basin...
between Grondines and Lotbinière
Lotbinière, Quebec
Lotbinière is a municipality in the Municipalité régionale de comté de Lotbinière in Quebec, Canada. It is part of the Chaudière-Appalaches region and the population is 909 as of 2009. It is named after seigneurie of which it was part...
, Quebec
Quebec
Quebec or is a province in east-central Canada. It is the only Canadian province with a predominantly French-speaking population and the only one whose sole official language is French at the provincial level....
, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
. The crossing is very remarkable, as it was first implemented as overhead crossing, which was later replaced by a cable tunnel.
This unusual and very expensive way was chosen as Hydro-Québec wanted to complete the transmission line in time, which was only possible with an overhead crossing of Saint Lawrence River. However, due to the negative visual impact of the large towers of the overhead crossing by the local population of Grondines and Lotbinière, it was decided to build a cable tunnel under the river, although this made the project more expensive.
In 1988 construction work for three artificial islands in the Saint Lawrence River, which were connected with jetties
Jetty
A jetty is any of a variety of structures used in river, dock, and maritime works that are generally carried out in pairs from river banks, or in continuation of river channels at their outlets into deep water; or out into docks, and outside their entrances; or for forming basins along the...
to the mainland as construction for the pylons of the overhead crossing started. Between July 1988 and spring 1989, 20,000 truck loads of 400000 tonne were transported.
In 1989 the towers of the temporary overhead line crossing
Overhead line crossing
An overhead line crossing is the crossing of an obstacle—such as a traffic route, a river, a valley or a strait—by an overhead power line. The style of crossing depends on the local conditions and regulations at the time the power line is constructed. Overhead line crossings can...
were erected. The suspension pylons on each side of the waterway were 140 metres (459.3 ft) tall to ensure the required clearance. Building these towers required five months construction time and approximately 40 specially trained workers.
At the end of 1989 the overhead crossing, which consisted of five towers, was completed.
In spring 1989 work on the 3954 metres (12,972.4 ft) long cable tunnel started, which took six months of drilling in two 12-hour shifts. The average drilling rate was 27 metres (88.6 ft) a day, but achieved in horizontal sections over 90 metres (295.3 ft) a day.
On March 26, 1990 the tunnel boring machine
Tunnel boring machine
A tunnel boring machine also known as a "mole", is a machine used to excavate tunnels with a circular cross section through a variety of soil and rock strata. They can bore through anything from hard rock to sand. Tunnel diameters can range from a metre to almost 16 metres to date...
reached the surface 8 centimetres (3.1 in) away from its target point. Later the tunnel was covered with concrete, and troughs for the cable support were installed.
On November 1, 1990 the HVDC transmission line went in service with a transmission rate of 1200 MW, which was increased to 2250 MW on July 1, 1991.
In 1992 the overhead line over the Saint Lawrence River, including the artificial islands and the jetties were dismantled. Portions of one of these towers would later be used as part of the observation tower at La Cité de l'Énergie
La Cité de l'Énergie
La Cite de l'Énergie is a theme park based on local industrial history and located in Shawinigan, Quebec, Canada.-Facilities:*A science centre, which includes a high observation tower and features a multimedia show as well as a permanent interactive exhibit...
in Shawinigan. The costs for dismantling was $16 Million (CDN
Canadian dollar
The Canadian dollar is the currency of Canada. As of 2007, the Canadian dollar is the 7th most traded currency in the world. It is abbreviated with the dollar sign $, or C$ to distinguish it from other dollar-denominated currencies...
).
See also
- Hydro-Québec's electricity transmission systemHydro-Québec's electricity transmission systemHydro-Québec's electricity transmission system is an expansive, international power transmission system located in Quebec, Canada with extensions into the Northeastern United States...
- Quebec - New England TransmissionQuebec - New England TransmissionThe Quebec – New England Transmission is a long-distance high-voltage direct current line between Radisson, Quebec and Sandy Pond in Ayer, Massachusetts...