SLOPE OF WATERCOURSE
Conduits with outlets must be installed in watercourses whose slope is greater than 2%. In addition, the slope of the watercourse may not exceed the percentage appearing in table 1, which varies on the basis of the length of the conduits.
Table 1. Maximum slope of the watercourse on the basis of the length of the conduits
|Length of the conduit (m)||Maximum slope of the watercourse (%)1|
|Less than 15||5|
|Equal or greater than 15||6|
1The slope is the inclination of the section of the watercourse between the first natural thresholds not touched by the work (excavation, installation of conduit, rockfill, etc.) and located upstream and downstream of the culvert. It is measured from the thalweg of each threshold.
NARROWING AND WIDENING OF THE WATERCOURSE
Maximum narrowing of the width of the watercourse: 20%
Widening of the watercourse: where required by the calculation of the flow
DIMENSIONS OF CONDUITS
Minimum diameter of the conduits: 1,200 mm
Minimum length of the conduits: 9 m
Maximum length of the conduits: 24 m
DESIGN OF OUTLETS
Characteristics of outlets
The outlets must be manufactured to remain in good working order and be functional for the expected life of the conduit. The outlets must not reduce the expected life of the conduit.
The outlets must have a height of 500 mm or more and dull edges. They must be equipped with abutments. The material of the outlets must be corrosion resistant.
The outlets must not be inclined by more than 9 degrees in relation with the transverse axis of the conduit. The joints between the outlets and the conduit must be leakproof. The number of outlets and their location in the conduits must comply with the standards in table 2, which vary according to the length of the conduit.
Table 2. Number and location of the outlets in relation with the length of the conduit
|Length of the conduit (m) 1||Number of outlets||Distance between outlets (mm)||Distance of the first and the last outlets in relation to the ends of the conduit (mm)|
1Conduits greater than or equal to 12 m in length may be obtained by connecting conduits with a lesser length presented in table 2.
Characteristics of notches in outlets
Notches in outlets must be rectangular with dull edges. Notches may be located in the centre of the outlets or off-centre alternating from one outlet to the other. The dimensions of the notches in the outlets must comply with the standards in table 3, which vary according to the diameter of the conduit.
Table 3. Dimensions of notches in outlets according to the diameter of the conduit
|Diameter of the conduit (mm)||Dimensions of notches|
|Width (mm)||Height (mm)|
|Less than 2,200||150||200|
|2,200 to < 2,700||200||250|
|2,700 to < 3,300||250||300|
|3,300 to < 3,600||300||300|
|3,600 and over||400||300|
PROCEDURE FOR INSTALLATION
Burial depth of downstream invert
The downstream invert of the conduit must be buried at a depth of 500 mm in relation with the thalweg of the control sill not touched by the work. The control sill is located downstream of the energy dissipation basin at a distance equal to or greater than three times the diameter of the conduit. The first outlet downstream of the culvert will be submerged.
Burial depth of the upstream invert
The upstream invert of the conduit must be buried at a depth of 200 mm in relation with the thalweg of the bed of the watercourse before the installation.
Energy dissipation basin
An energy dissipation basin is required downstream of the conduit. The downstream limit of the energy dissipation basin must be the control sill not touched by the work located at a distance equal to or greater than three times the diameter of the conduit. The depth of the energy dissipation basin must be ≥ 500 mm.
Slope for the installation of the conduit
The slope for the installation of the conduit depends on the slope of the watercourse, the length of the conduit and the burial depth of the upstream and downstream inverts. The installation slope must therefore be greater than the slope of the watercourse.
Culvert with parallel conduits
If outlets are installed in both conduits, the inverts of the conduits must be buried at the same depth.
If outlets are installed in only one conduit, the invert of the conduit without outlet must be located 500 mm higher than the invert of the conduit with outlets.
The following practices are prohibited:
- on-site welding;
- torch cutting of steel elements;
- cutting holes with a torch.