Sizing catch basin parking inlets
Sizing catch basin parking inlets
(OP)
Does anyone have experience sizing catch basin inlets in parking lot? I am doing this for the first time and have not had any luck finding adequate information online or in books.
RE: Sizing catch basin parking inlets
RE: Sizing catch basin parking inlets
RE: Sizing catch basin parking inlets
For ponding up to 0.4 ft:
Q=CPd^1.5
C=3.0
P=Permieter of grate minus side against curb
d=depth
For ponding over 0.4 ft:
Q=CA(2gd)
C=0.67
A=clear grate opening
g=32.2 ft/sec^2
Hope this helps a little
RE: Sizing catch basin parking inlets
RE: Sizing catch basin parking inlets
good lick
RE: Sizing catch basin parking inlets
I assume you've graded the parking to a series of low points which you are placing inlets. How much depth of water can you tolerate at the inlet? 0.1'? Back check the spread of water at that depth. It would also be nice to leave some "dry" isles for people to get to their cars without stepping ankle deep during a rain shower. Tweak the grading plan.
I’m guessing your next task is storm detention.
RE: Sizing catch basin parking inlets
RE: Sizing catch basin parking inlets
I suggest the following:
1) Determine if there is a regulatory requirement for maximum allowable ponding depth at a specific storm interval/type (10yr 24hr Type II; 25 yr 6hr Type III,; etc).
2) Determine if you client has a requirement for maximum allowable ponding depth at a specific storm interval/type.
3) Determine the maximum allowable ponding depth at a specific storm interval/type for the most active governmental body in your area.
4) Use the more restrictive of the ponding depths for design unless there is a specific reason not to do so (such as direction from your client to use the maximum allowable ponding depth).
5) Make sure that any depth selected protects the health, safety, and welfare of the public regardless of other requirements.
6) Determine the traffic types: heavy vehicular, light vehicular, bicycle, pedestrian, wheelchair, motorcycle, etc.
7) Develop the runoff hydrograph for the watershed contributing to each inlet.
8) Use the traffic types to determine the appropriate grate type (maximum grate spacing to allow safe passage of tires without dropping into grate, minimum grate load capacity to carry heaviest traffic).
9) Route the inlet watershed runoff hydrograph through the inlet/grate (and subsurface system) to determine if it is adequate. (You can develop a routing spreadsheet to automate this analysis using the various appropriate orifice, pipe, weir, and channel equations/models. There are several software package that will aid in this analysis as well. See “http://hhwq.blogspot.com”.)
10) Verify adequacy of grate
11) Repeat steps 8, 9, and 10 as necessary.
Let me know if you need more information. There are lots of documents (manuals, guides, etc) available that will walk you step-by-step through this process.
Also, Why do you have a grate in the middle of the traffic lane? Why not have depressed islands between the rows of spaces. The depressed islands can eliminate or reduce the number and size of inlets and pipes necessary while providing detention, retention, and associated water quantity and water quality management benefits. For images of this, see “h
.
tsgrue: site engineering, stormwater
management, landscape design, ecosystem
rehabilitation, mathematical simulation
http://hhwq.blogspot.com