104. On crossing sites where the free flow of fish needs not be ensured by reason of the presence of any of the situations described in section 103, the installation of the culvert must meet the following conditions:
(1) the diameter or span of the conduit or arch must be at least 450 mm;
(2) the conduit must be installed following the natural slope of the watercourse and be buried under the bed of the watercourse at a depth equivalent to 10% the height of the conduit, without exceeding 500 mm regardless of the size of the conduit;
(3) the culvert may not reduce the width of the watercourse by more than 50%, measured from the upper limit of the banks.
On a crossing site where the free flow of fish need not be ensured, a culvert may include 1 smooth wall conduit or 2 in the case of parallel conduits.