Storm Water Runoff Design

[CivilG]

To whom it may concern,

I need to do an stormrwater runoff analysis of a 100 acre industrial site. The site currently discharges directly to waters of the US; however, the local water board is coming down on them and the facility needs to hold and or treat the runoff water. What method would you use to measure the runoff. The area has a large mix of surface types (grass, buildings, pavement, dirt, driveways). I remember doing a lot of studying of this in college but it has been a while. Would I use unit hydrograph method or something else. What about: V=CAR/12? Is the rational method (Q=CIA) good for anything? I am thinking I need a topographical survey of the site. Any advise would help. Thanks,

 

[TerryScan]

I would imagine you do need a topographical survey of the site. The best thing to do when determining methodology is to get the regulatory requirements (EPA, State, County, Local?). Regardless of what preferences we may have here, you need to satisfy the regulator. SCS methodology would likely be most appropriate for this type of application. Rational method is good for sizing pipes, not too appropriate for evaluating treatment BMPs for a 100 acre industrial site.

 

[beej67]

Get a topo, use the SCS method to design your pond. Find out what storm you have to treat - that's an important nugget.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[gbam]

Please confirm that you are looking to measure actual flow rates or are you wanting to estimate the runoff rates using a hydrologic analysis method that would compute discharge values? Might I recommend that you use the appropriate hydrology method that is approved by the governing agency; which may be or may not be SCS method. Hopefully, you have a drainage manual that can point you in the correct direction.

 

[BillsSis]

If the local water board wants the runoff to be held for any length of time before discharging, then that sounds like a detention pond. If that is the case, then you would need to use the SCS method (Curve Numbers for the cover of the land)because time is now involved rather than just the peak flows or discharges.

Reiterating what Terry, beej and gbam have said, first find out what the regulations are for the local water board or the governing entity of the stormwater in this area. Then, follow their regulations.

Good Luck!