Parking Lot Inlet Ponding

[TieGuy07]

I'm looking to analyze the depth of ponding (for a 3-yr & 100-yr storm event) at each grate inlet for a parking lot storm sewer system -I'd appreciate any input on the best way to do this without using a for fee software program -thanks.

 

[sam74]

Do a google search for neenah foundry. They have a grate capacity tool on their website which gives a ponding depth for several grates they have actually modeled. If your lucky neenah grates have been specified for your project. If not peruse their catalog and find a similar grate to the one you are using.

I tried to access the site after googling but could not get to it. They may be having some problems or are updating.

 

[gbam]

If you have not spec'd out a proprietary grate, then all you need to do is determine the open perimeter and open area of the grate and compute the depth based on weir and orifice flow. Use the one that controls. At times there are additional safety factors required, clogging. Check with you local reviewer/design standards.

 

[TieGuy07]

Ok, thanks for the info -Neenah's inlet calculator is handy enough.

 

[saruman26]

The FHWA has a program available from the hydraulic software side of their site called "Visual Urban" that contains modules to do exactly what you describe.

http://www.fhwa.dot.gov/engineering/hydraulics/software/softwaredetail.cfm

 

[Maury]

Assuming that your storm sewer sysstem is designed for an event between 3-year and 100-year, then the grate capacity will be the conttolling factor for a 3-year storm and the tables furnished by Neenah will tell you the depth; the storm sewers will be the limiting factor for the 100-year event and the depth will be determined by the topopgraphy and the elevation of the overflow, not by inlet hydraulics.

 

[harringr]

Grate inlets may be evaluated using the following formula (with restrictions)

Q cfs = 3.0(PH^3/2)
P = permiter of the grate (ignoring bars)
H = head over grate
this can only be used for h=0.4 or less
If it is not a combination inlet them multiply by 75% to account for clogging

this assumes that the total discharge can enter the system for the design storm ...
others an hgl will have to be run and a routing program (100-year storm)