Sewers. Circular

55 √z X 2f = v, and v X a = V; x representing area of sewer / the wetted perimeter, f inclination of do. per mile, and v velocity of flow, in feet per minute; a area of flow in square feet, and V volume of discharge in cubic feet per minute.

Egg

D /3 = w, 2D/3 = w', and D = r. D representing height of sewer, w and w' width at bottom and top, and r radius of sides.

In culverts less than 6 feet in depth,* the brick-work should be 9 inches thick. When they are above 6 feet and less than 9 feet, it should be 14 inches thick.

If the diameter of top arch = 1, the diameter of inverted arch = .5, and the total depth = the sum of the two diameters, or 1.5, then the radius of the arcs which are tangential to the top, and inverted, will be 1.5.

From this any two of the elements can be deduced, one being known.

Oval

Top and bottom* should be of equal diameters. The diameter .76 depth of culvert; the intersections of the top and bottom circles form the centres for striking the courses connecting the top and bottom circles.

The inclination of sewers should not be less than 1 foot in 240.

Fig. 42.

Dimensions, Areas, And Volume Of Work Per Lineal Foot Of Egg-Shaped Sewers Of Different Dimensions

In laying large sewers through quicksands, cast-iron inverts are sometimes employed, and with success, to connect the foundation of the whole work together.

* Internal dimensions.

Area of Surface from which Circular Sewers will discharge Water equal in Volume to One Inch in Depth upon surface per Hour, including ordinary City Drainage.