Product(s):	SewerGEMS, CivilStorm
Version(s):	10.00.XX.XX and higher
Area:	Modeling

Problem

How can a depth of fill (also known as fill depth or filled depth) be modeled in a pipe, to represent sand, sediment or other form of fill at the bottom of a pipe?

How does this impact results such as calculated depth in the pipe?

Solution

"Fill Depth" (known as "filled depth" in EPA-SWMM) is a property of a circular shaped conduit in SewerGEMS and CivilStorm, but only when using the Explicit (SWMM) solver (as selected in the calculation options). It is used to represent sediment at the bottom of a circular pipe, impacting the pipe's capacity. From the EPA-SWMM documentation:

As for calculations, they will treat it as if the effective area of the pipe is the blue shaded area in the diagram above and the hydraulic grade will appear accordingly in profile view for example.

Note that when viewing the calculated depth in a conduit with fill depth, it is measured from the top of the fill (depth/height of the blue shaded area in the diagram above) rather than being measured from the actual pipe bottom. This assumption is consistent with EPA-SWMM itself (where the calculated depth is also measured from the top of the fill) as of version 5.2.

For example given a 12 inch pipe, 6 inch fill depth, and calculated HGL about equal to the pipe top, the calculated depth is reported as about 6 inches (because it is the depth of water). The fill depth effectively increases the pipe bottom elevation.

How does "Fill Depth" work for conduits?

Problem

Solution

See Also