Site Grading - MINIMUM slope errors

Site Grading & Site Design Vignettes and Multiple Choice

Site Grading - MINIMUM slope errors

Postby Sparky83 » Thu Mar 02, 2017 11:39 am

This is an example of the most common error in site grading.

DO NOT use sketch circles to check the MINIMUM slope. You must measure the path that water will take downhill. Use sketch lines...shown in red. Sketch circles can only be used to measure a distance that is a straight line...basic geometry.

The green dimensions total 56'-0" even though the tips of the topo lines are within 50' of each other. Same for the blue dimensions at 65'-0" apart.

site grading no min slope.JPG


This file has better resolution. Thanks to mandyk650:
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Last edited by Sparky83 on Sun May 07, 2017 4:33 am, edited 1 time in total.
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Re: Site Grading - MINIMUM slope errors

Postby thd7t » Thu Mar 02, 2017 2:51 pm

Thank you! I have seen you post this diagram before, but was having trouble finding it. It looks like you are following low points (swales) and the percent grade is determined by the path of the water. Am I understanding this correctly?
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Re: Site Grading - MINIMUM slope errors

Postby Sparky83 » Thu Mar 02, 2017 4:42 pm

thd7t wrote:Thank you! I have seen you post this diagram before, but was having trouble finding it. It looks like you are following low points (swales) and the percent grade is determined by the path of the water. Am I understanding this correctly?

The distance the water will travel....along the centerline of the swale (red lines) cannot exceed 50' if you have a min slope required of 2%.
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Re: Site Grading - MINIMUM slope errors

Postby thd7t » Fri Mar 03, 2017 9:40 am

This really clarified things for me.
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Re: Site Grading - MINIMUM slope errors

Postby Poedirty » Sat Mar 04, 2017 10:20 pm

Thank you!
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Re: Site Grading - MINIMUM slope errors

Postby KOOTA » Tue Mar 07, 2017 10:34 am

in order to avoid this you just make the distance between the 107' elevation swales larger? is there a max separation to stay with in, (talking about107 elevation line that goes around the building)
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Re: Site Grading - MINIMUM slope errors

Postby Sparky83 » Tue Mar 07, 2017 12:41 pm

KOOTA wrote:in order to avoid this you just make the distance between the 107' elevation swales larger? is there a max separation to stay with in, (talking about107 elevation line that goes around the building)

The "points" coming from the north & south on the east side of the display should be close to each other. They are the same elevation so there is no minimum distance between them. If they are too far apart, they do not provide adequate runoff protection for the display.
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Re: Site Grading - MINIMUM slope errors

Postby redbird11 » Wed Apr 12, 2017 7:09 pm

Hmmm...are you not changing your rise more than 1 foot?

1'-0"/.02= 50'-0". Something doesn't add up about this statement.
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Re: Site Grading - MINIMUM slope errors

Postby Sparky83 » Wed Apr 12, 2017 7:10 pm

redbird11 wrote:Hmmm...are you not changing your rise more than 1 foot?

1'-0"/.02= 50'-0". Something doesn't add up about this statement.

What are you talking about?
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Re: Site Grading - MINIMUM slope errors

Postby redbird11 » Mon Apr 17, 2017 2:26 pm

Sparky- I apologize, I see now that I did not know what I was questioning. The resolution of the screenshot showed up poorly on my phone. I have now looked at it on the computer, and I get it.
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