Comprehensive Study Report

Volume 2 of the draft-design report provides a detailed description of the environment and of the inventory methods used to characterize it, while Chapter 2 of Volume 1 gives a summary description of the environmental components likely to be affected by the project. In the section below, the main environmental components of the study area are summarized.

6.1. Physical environment

6.1.1. Physiography and soils

Physiographically, the study area is bounded by the Laurentian foothills in the north and the St. Lawrence lowlands in the south.

In the stretch of river between the Grand-Mère Dam and the Manigance Rapids, 52% of the riverbanks are subject to heavy, medium or light erosion, whereas the erosion that occurs elsewhere in the region is considered negligible, since the banks are rocky or already have protection. Some 15% of the riverbank areas, particularly those composed of clay and silt, are described as undergoing active erosion (21% of right bank and 8.5 % of left bank).

The riverbank sectors between the Grand-Mère and Shawinigan dams are also highly sensitive to erosion, especially on the left bank, where the sensitive proportion is 33.5%. However, less than 2% of all the riverbank sections show signs of instability.

In the Shawinigan-La Gabelle sector, more than 80% of the areas on the right bank, which are predominantly clayey and steeply sloped, show a high degree of vulnerability to erosion (50% of the whole sector). Nearly 21% of these riverbank areas are undergoing erosion, particularly in the sector downstream from the railway bridge, within the zone of influence of the La Gabelle generating station.

Undercutting by waves at the base of talus slopes and landslides are the main erosional phenomena observed. The discontinuation of timber driving activities, the attendant dismantling of log booms and the associated increase in boating activities, especially in the area upstream from the Grand-Mère facility, will augment riverbank erosion in sensitive spots.

6.1.2. Hydrography

In the Saint-Maurice River basin, covering an area of 43 250 km², there are eight dams (Figure 3) on the main reach of the river (Rapide-Blanc, Trenche, Beaumont, La Tuque, Grand-Mère, Shawinigan-2, Shawinigan-3 and La Gabelle), one dam at the outlet of the uppermost reservoir on the river (Gouin Dam), and several dams on the Manouane and Matawin rivers, which are tributaries of the Saint-Maurice. Collectively, these works make the Saint-Maurice one of the most regulated rivers in the world. The reservoir of the Grand-Mère power station receives inflows of water from the La Tuque station, as well as from tributaries in the intermediate part of the drainage basin situated between the two sites, including the Aux Rats, Wessonneau, Matawin and Mékinac rivers.

6.1.3. Ice cover

In the forebay of the Grand-Mère power station, the ice cover forms as soon as winter begins and, aside from some ice-free areas in the fast-flowing sectors upstream from Mékinac, the entire area from the Manigance Rapids to the Grand-Mère station becomes covered with ice. Downstream from the facility, the ice cover forms more slowly owing to the higher current velocity, and ice formation begins along the banks and moves toward the middle of the river, with a complete ice cover eventually forming between the area upstream of Hêtres Rapids and the area upstream of the Beaurivage sector.

6.1.4. Water quality

The river water is considered to be of good quality. The municipalities of La Tuque, Grandes-Piles, Grand-Mère, Saint-Georges and Shawinigan all have sewage treatment plants. The same is true also for the Abitibi-Consolidated mills at Grand-Mère and La Tuque, the Belgo plant at Shawinigan, and the Canadian Pacific Forest Products (CPFP) mill at La Tuque.

6.1.5. Sediments

The inventory of the sediments found in the forebay of the power station shows that fine materials are present near the riverbanks, with the coarsest materials occurring toward the middle of the river.

Analyses of the fine sediments in this sector show that there is no severe contamination by the organic and inorganic parameters tested. Only one sampling station, situated in a small bay near the Highway 153 bridge, which still occasionally receives discharges from an old sewage outfall, presented some exceedances of the protection criterion relative to lead and mercury levels. Commissioning of the new power station will not, however, cause the resuspension of those sediments.

In the afterbay, the riverbed is rocky or composed of sand or gravel.

6.2. Biological environment

6.2.1. Fish fauna and fish habitat

In all, 26 fish species were inventoried in the area between Shawinigan and La Tuque. Species of interest for fishing include walleye, yellow perch, smallmouth bass, northern pike, brook trout, white sucker and longnose sucker. These species are found both upstream and downstream from the Grand-Mère facility. Occasional catches of Atlantic salmon and muskellunge were also made downstream from the Grand-Mère power station.

Atlantic salmon and American eel are the only two migratory species likely to occur in the study area.

Atlantic salmon, introduced into some waterbodies upstream of Grand-Mère (Taureau Reservoir, and Mékinac, Inman and Dunbar lakes) occasionally swim into the Mékinac and Matawin rivers and from there into the Saint-Maurice. However, this nonindigenous species appears only occasionally in the sector downstream from the Grand-Mère facility.

There are reports of American eels being found in the afterbay of the Grand-Mère generating station. However, this occurrence is considered unusual, since the eels would have to get over a 44-m-high drop at the Shawinigan complex, located 16 kilometres downstream, in order to reach that area. Furthermore, experimental fishing conducted to date has not turned up any sign of the species' presence between the two dams in question, and it is not known to have occurred beyond the Grand-Mère facility. The existence of a series of large falls and cascades at the site of the present hydroelectric facilities has no doubt always impeded American eel migration in this sector.

The smallmouth bass population that is found between the generating station and the Hêtres Rapids is considered to be at risk, since its abundance level is low and sport catches are small as well. In 1997 in an effort to promote the species' production, GDG Conseil Inc. established wildlife enhancements in the Beaurivage sector, which is between the CN bridge and the Hêtres Rapids. The enhancement structures consist of two or three large boulders which were installed in order to block the current. In addition, gravel material (20 to 45 mm in diameter) was provided to permit the construction of nests.

Inventories conducted between the Grand-Mère station and the Hêtres Rapids confirmed the presence of three spawning grounds in fast-flowing water and two spawning sites in slow-moving waters. About a dozen aquatic beds, containing known or potential fish habitats, were also identified between the Grand-Mère and La Gabelle dams (GDG, 1997).

In the local study area, smallmouth bass spawn in an area covering at least 150 m², which is part of a shoal located at the foot of the left gravity dam. White sucker also spawn in this shoal (1 547 m²) and in another shoal near the left bank, downstream from Simard Point (10 300 m²). Yellow perch use a small area of riparian scrubland on the right riverbank opposite Simard Point, at the northern end of the beach where the industrial outfall is located. In view of the prevailing hydraulic conditions at this spot, this habitat is of little value at present and the new conditions that are anticipated will not change the situation appreciably. In addition, although no walleye spawning grounds were identified, it is possible that the species spawns in the local study area.

6.2.2. Avifauna

With over 118 bird species observed in the extended study area and the surrounding region, the sector has a fairly high diversity of bird species. The Atlas of Breeding Birds (Gauthier and Aubry, 1995) reports data on the confirmed nesting of some 50 species. In the riparian environment, given the limited areal extent of wetlands, the fairly straight riverbanks and anthropogenic disturbances, favourable habitats for waterfowl and shorebirds seem to be in short supply. The proponent did not identify any special or unusual habitats in the local study area.

6.2.3. Riparian and aquatic vegetation

Aquatic beds are the most common type of wetland in the study area. From the Manigance Rapids to the La Gabelle power station, habitats of this type occupy an area of about 198 ha. They are most abundant in the forebays of the Grand-Mère (118 ha) and Shawinigan (35 ha) generating stations.

Tapeweed assemblages largely dominate the plant communities of the aquatic beds sampled between the Highway 153 bridge and the Hêtres Rapids. Other plants include Canada waterweed, needle spikerush and emersed pondweed, which are deep-rooting perennial species. These plants are evenly distributed at a depth range of 0.5 to 2 m.

Emergent weedbeds (marsh), found at depths between 0 and 0.5 m, are composed primarily of marsh bedstraw and aquatic zizania (wildrice), with some Pennsylvania knotweed. Wet meadows and shrub swamp occupy the part of the floodplain that is exposed during the low-water period in summer, with the dominant plant assemblages of those habitats being reed canary-grass and alders and willows, respectively.

The local study area comprises three aquatic beds and two marshes (emergent weedbeds), including one located on the left bank upstream from the existing weir and the other at the future disposal site for excavated material. Wet meadow and shrub swamp habitats appear to be poorly represented in the local and extended study areas downstream from the Grand-Mère facility. In the downstream part of the zone of influence, development of scrubland and aquatic beds is limited by the rocky substrates bordering the river and the steep banks.

6.3. Human environment

6.3.1. Socio-economic and socio-demographic profile

The study area is situated almost entirely within the Centre-de-la-Mauricie RCM, which encompasses about 15 municipalities, 10 of which border the Saint-Maurice River. The most populous cities are Shawinigan, Shawinigan-Sud, Grand-Mère and Saint-Georges. This RCM stands out from other areas of Quebec by the fact that its primary and secondary sectors are more fully developed, but its tertiary sector is less developed, though it is expanding rapidly. The unemployment rate is high, or about 18%. There are no North American Indian communities within the study area. Three Native communities, the Weymontachie, Obedjiwan and Manouane reserves, are situated on land outside the project's zone of influence.

6.3.2. Recreation and tourism

The La Mauricie National Park, the Shawinigan Falls regional park and the Saint-Jean-des-Piles-Grandes-Piles sector are the main centres of recreation and tourism in the region. The Saint-Maurice River, which in summer 1996 was used by more than 15 000 pleasure boating enthusiasts (motor boats, canoes, etc.), is the venue for a major annual canoeing event called the "Classique internationale de canots de la Mauricie." Following the dismantling of the booms formerly used to float timber downstream to paper mills, the river became completely accessible to boats between the Grand-Mère Dam and the Manigance Rapids. The bay near the Grand-Mère golf course, Desaulniers Point and Simard Point, along with the area just downstream from the generating station, are frequented by fishermen during the summer.

In winter, ice fishing is conducted in a number spots within the extended study area. Three fishing sites were identified by the proponent in 1996: the bay on the right bank just upstream from the Auberge de Grand-Mère and the bays downstream from the village of Saint-Roch-de-Mékinac and Ile aux Pins. Snowmobilers and all-terrain vehicle operators also use the river. There are some groomed trails and spontaneous trails which give access to the river, including one trail leading to the left bank upstream from the existing weir. Trail No. 3 of the national snowmobiling network crosses the Saint-Maurice north of the La Gabelle Dam, while provincial trails 347 and 318, located upstream from the Grand-Mère Dam, are among the most popular snowmobile trails in the extended study area. In 1996, it was estimated that more than 13 500 people visited the area between the La Gabelle generating station and the Manigance Rapids during the winter.

6.3.3. Land use

In the immediate area of the municipality of Grand-Mère, there is very little vacant land. Abitibi-Consolidated's industrial facilities are located there, and so is an extraction site operated by Construction et Pavage Maskimo, some CN property and a residential zone. It should be noted that the Grand-Mère generating station can only be reached by crossing the paper mill's land. On the left bank, the majority of parcels of land between the railway tracks and the Highway 153 bridge belong to Hydro-Québec. Entreprises Grand-Mère-Est owns some land near Highway 153, but the land located at Lac-à-la-Tortue belongs to Excavation Gaston Trépanier.

6.3.4. Archaeology and heritage

Six zones within the local study area have components of potential archaeological significance that may be affected by the construction work. The inventory did not uncover any evidence of prehistoric human occupation, however. From a historical viewpoint, the structures or artifacts identified in the construction area are of limited industrial, architectural or heritage significance.

According to a study done by Hydro-Québec, the Grand-Mère hydroelectric station, whose architecture is based on that of a gothic cathedral in France (Sainte-Cécile d'Albi), is considered one of the three most promising facilities from a heritage standpoint out of about 90 hydroelectric complexes evaluated. Its heritage value is not limited to the station building itself, since the retaining and control structures still rank as part of the most important multiple-component concrete dams ever built in Quebec. Many of the site's electrical and mechanical components also have an exceptional, very high or high heritage value.