Culvert sizing

Culvert sizing. Culvert sizing. Project proponents and department staff shall use any of the following calculation and assessment methods for potentially exempt culverts under s. NR 320.04 (10) and culvert individual permit applications under s. NR 320.06 . (1) Calculation of required culvert area. To determine the required culvert area, measurements shall be made of the channel width of the stream in feet at the bankfull width (W), and the maximum bankfull height in feet above the stream bottom (H) (see diagram). These measurements shall be made at each of 3 locations or transects along the stream: the location of the newly proposed culvert crossing; 100 feet upstream from the crossing; and 100 feet downstream from the crossing. Where there is an existing crossing being replaced, measurements at the site of the crossing may not be representative due to impacts related to the existing crossing. In such instances two measurements shall be taken, upstream and downstream of the crossing location. Measurements shall be taken to ensure that the locations where measurements are made are representative of the stream overall. The individual measurements of W and H shall be averaged to derive the final W and H values. The required culvert area is then calculated with the following equation: (2) Culvert sizing. Once the required culvert area has been determined, the applicant can identify the proper culvert size by reviewing Table 1 for round culverts and Table 2 for arched pipe culverts. The minimum size culvert needed to pass flows shall have an area that is as much or more than the required culvert area. For example, the recommended culvert size for a culvert area calculation of 8.50 square feet would be 42 inches. (a) To find the area of any round culvert, use the following equation: (b) Example culvert area calculation. (3) Culvert length determination. The proper culvert length is determined by the following calculation: (a) To determine the length of any culvert, use the following equation: (b) Example culvert length calculation.