Sanitary Design Flow for Parking Garage

Are you collecting rainwater? You can use this as your flow rate Q=CIA

Q=flow rate (L/s) ; C=run-off coefficient; just say 0.9; I - rainfall intensity mm/hr

A= coverage area (sq.m).

If not, assumed carpark area will be covered with water at depth of 50mm (to get the volume) then divide it by your assume drain time to get your flow rate.

Some local code based the flow rate on the sprinkler flow rate.

Ah, to be given an opportunity such as you have in an age when stewardship of resources appears to matter...You could use your stormwater design system to generate a bit of power on rainy days perhaps to run emergency exit signs or something better depending on how many stories of vertical drop will be involved..Dream about the possible before designing the system to handle a problem..design the system as an opportunity to utilize creative engagement ..Perhaps make it in to a cascading loop of falling water only functional on rainy days chuteing into your municipalities sewer system..at the bottom end or into a pond as part of the garge landscaping design which would connect to a sewer at overflow spots like in a tub or larger pool.I think if i were younger i'd be a design engineer and have fun with the process and the outcome wherever possible..Regards,MartyW a rambler on most occassions

Water flow is collected water from the roof or top level, per local code and conditions, PLUS rainfall that gets into the open sides of the garages. City of Chicago presumes that to be rain at a 45 degree angle against the side of the building.

Check with local code authority for your building.

Since you are connecting to sanitary seweer, you will probably need an OWS (oil/water separator) that the owner/operator of the parking garage will have to clean and maintain.

Forget about generating enery from the falling water, flow is too unsteady to economically generate.

However, you have an opportunity to "harvest" rainwater for later use in irrigation for landscaping or other "Non-potable" applications. This could be worth some green points if this is for a campus looking to be environmentally conscious.

Definitely check with your local authority for the desing storm requirements and any special requirements. Typically the design storm for a sorm drainage collection system will not approach a 100 year event, this is more typical of a design storm for a storage or detention system. Design storms for collection systems is more typically 5 years to 25 years depending on local codes. You can use many methods to develop a design storm hydrograph, SCS methods are frequently used for this.