I dont quite understand your problem, but I will add this maybe it will help. HGL isnt your actual water surface elevation, but a head representive only, since it includes velocity. It can exceed your top of pipe, just not your top of the inlet castings. I havent encountered a flat HGL before...
Doghouse inlet is simply a regular inlet placed over an existing sewer run. So the bottom of the basin is cut to fit over and around the existing run. Then the run is opened up to allow flow from the inlet into the run. The resulting inlet looks like a doghouse before its installed.
Grass or jute matting can be considered erosion protection. I would call the soil/water conservation district in charge and see if they'd approve something as simple as grass since the slope is minor.
Anyone have an equation to calculate the time it takes for a specific amount (cubic feet) of water to exit a 2" orifice? Taking into account the pressure changes by the decreasing depth of the water above the outlet as it drains??
Anyone know of a good, general equation determining the capacity of an inlet? My basin in question is in a parking lot low point; Given dimensions and open area of the casting, what Q can it take before it ponds a given depth?
I found one that says Q(cfs)=3.0(grate permimeter)(depth of...
How are the connections from the bottom of the basin to the pipe network made? Settlement of the filled pipes on saturated soil may cause additional stresses on the connections.
