Chicago Design Storm from IDF Curve

[TORCHMAN]

Fellow engineers,

I am working on a small project where a bit of parking lot is being regraded to create a loading dock. This loading dock will slope down about 4 ft but the overhead door and opening will remain raised to current grade. As a method of storm water management, the architect proposed that a catch basin with a pump be added to the bottom of the loading area. I am looking to check the pump requirements for this application.

I plan on using a 5 and 100 year storm as a check per my regional guidelines. Specifically, I am stuck creating time series for chicago design storms required by the regional guidelines using IDF Curves (provided by MTO). While the MTO IDF Curve lookup tool provides coefficients A and B, the equations I find for chicago design storms require more coefficients (n and gamma) from the research I found - based on Bentley StormCAD website. Can anyone recommend an online resource or textbook with examples? Is the go to place "Applied Hydrology" by Chow et al. (1988)? I have found an online version but somehow it is missing the pages I need - Chapter 14.4

 

[Engimental]

https://sites.google.com/view/dstorm

When selecting a pump, make sure you consider pump run and rest (cycle) times for your design flow and sump size.

 

[TORCHMAN]

Thanks Engimental!

That is a great resource! Who made this? There is no copyright or any credit to anyone.

When it comes to considering the pump run and rest times, di you spec 1 min off 1 min off or 2 mins on 2 mins off?

 

[Engimental]

It was created by Lew Rossman (

https://www.openswmm.org/Topic/32275/dstorm-a-design-storm-wizard),

former lead developer of SWMM and EPANET at EPA.

Regarding pump cycling, it really depends on the number and type of pump/motor(s) (and even the specific model) used and the duty schedule implemented, but a general rule of thumb is a maximum of 30 evenly-spaced starts per hour. The key point (and challenge) is that the pump(s) need to deliver the required flow to fully capture the design storm while simultaneously maintaining acceptable cycling per manufacturer specifications over the full range of operating conditions that the pump will be subject to during its design life. This is hard to achieve without special measures (e.g., multiple pumps of varying capacity, VFDs or other RTCs, upstream detention, etc.) due to the high variability and high peak flows associated with stormwater. Therefore, your design should reflect the consequence of failure and the likely response time to repair/replace a failed pump.