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6 Feb ’14
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Ah ha!
Content of Horizontal Sloped Cylindrical Tanks or Pipes
The calculator can also be used for partly filled circular pipes.
So it is only a static measurement which does not account for water movement or flow rate, but I still think it's useful.
15 Feb ’12
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Have you looked into licensing requirements to do this?
6 Feb ’14
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Do you mean permits?
6 Feb ’14
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Brought this up last night to my friend. She came up with:
http://ucanr.edu/sit.....138029.pdf
Page 13 refers back to table 8.1 on page 3...
Drainage Structure Sizing |
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Drainage Area(Hectares) |
Size of Drainage StructureInches and Area (m2) |
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| Steep Slopes Logged, Light Vegetation C= 0.7 |
Gentle Slopes Unlogged, Heavy Vegetation C=0.2 |
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| Round Pipe (in) | Area (m2) | Round Pipe (in) | Area (m2) | |
| 0-4 | 30" | 0.46 | 18" | 0.17 |
| 4-8 | 42" | 0.89 | 24" | 0.29 |
| 8-15 | 48" | 1.17 | 30" | 0.46 |
| 15-30 | 72" | 2.61 | 42" | 0.89 |
| 30-50 | 84" | 3.58 | 48" | 1.17 |
| 50-80 | 96" | 4.67 | 60" | 1.82 |
| 80-120 | 72" | 2.61 | ||
| 120-180 | 84" | 3.58 | ||
Notes: If pipe size is not available, use the next larger pipe size for the given drainage area. For intermediate terrain, interpolate between pipe sizes.
|
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I'm not sure what area of hectares qualifies as the drainage area, so I assumed the entire portion of valley slope that could possibly drain towards the stream prior to the start of the culvert. Using Google Earth, I got 30.25 hectares which would be 42 or 48 inch pipe on the table.
While on page 13 they make a recommendation to plan for bigger events like 20 to 50 year storms and also warn to consider 100 year floods, I'm not sure if the table is for normal rainfall, or for one of the bigger events. The table does say it is for a rainfall of 3 to 4 inches per hour so if I can determine local hourly rainfalls for normal vs big events that might help. Of course there is also the matter of for how many hours and/or how many days of continuous rainfall or for new rains adding more before the prior rains could be drained away.
42 inch pipe will cost about $2000 while 48 inch will cost about $2600. While saving that $600 is tempting, this has the potential to be a "pay more now, or pay WAY more later" decision. According to the table, 48 inch pipe might make the difference for a big event. The additional diameter will also help with passing debris and/or passing water despite debris under normal conditions.
6 Feb ’14
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Okay, using:
http://www.calctool......williams_g
(Edit: Originally posted April 23, 2014, 6:00 pm -- Corrected May 22, 2014, 8:28 am -- Correction of data to actual depth drop which is 1 foot for every 24 feet.)
With
- Roughness = 100
- Pipe Length = 24 feet
Drop = 2 inchesDrop = 12 inches
For 42 inch pipe I get
Capacity = 35,733.2 gallons per minuteCapacity = 94,031.5 gallons per minuteVelocity = 8.27507 feet per secondVelocity = 21.7758 feet per secondPipe Slope = 0.694444%Pipe Slope = 4.16667%
For 48 inch pipe I get
Capacity = 50,768.0 gallons per minuteCapacity = 133,596 gallons per minuteVelocity = 9.00132 feet per secondVelocity = 23.6869 feet per secondPipe Slope = 0.694444%Pipe Slope = 4.16667%
I think I am satisfied with the data and reasoning in favor of 48 inch pipe.
Rise (height) which is the internal dimension is listed as 36 inches for 48 inch arch pipe. I'm adding 10 inches to allow for upper and lower wall thickness which is listed as 5 inches each. That's 46 inches tall. Rise for 48 inch round pipe is 48 inches. Add 10 inches to allow for upper and lower wall thickness which is listed as 5 inches each. That's 58 inches tall. So arch pipe would save 14 inches in height.
Span (width) which is the internal dimension is listed as 58 inches for 48 inch arch pipe. For arch pipe, that is the ground level width. For round pipe, ground level width is about 1/3rd of the 48 inch diameter which would be 16 inches. I could potentially get round pipe and then get flared end sections for it later. The flared end section has the same ground profile as arch pipe. But flared end sections are about $1600 each. So buying round now could save about $700 in the short term, but cost $3200 in the long term.
I think wider ground contact is important, and saving on height may prove necessary, so again, arch pipe wins out. 48 inch arch pipe it is.
Now I just need to confirm that 24 feet (3 sections of 8 feet each) will be wide enough. I know that the slope must at a minimum use the 4/3 formula which states that for every 4 feet of height, 3 feet of width must be added for slope. So an 8 foot wide road surface with 2 feet of planted erosion control shoulder on either side would be 12 feet wide. The arch pipe is 3 feet 10 inches tall, rounded to 4 feet, and I need 4 feet of depth above that to bury phone and electric which would be 8 feet tall. That should also be enough height to bring the fill to elevation. At 8 feet high, applying the 4/3 formula tells me I need to add 6 feet on either side for slope. That brings the width of fill at the base to 24 feet and 12 feet at the top. So 24 feet of culvert pipe should work.
6 Feb ’14
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6 Feb ’14
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Since it looks like I may have high clay content (not performed soil test yet), the reading material on culverts advised against that. If I need to truck in fill, I need to know how much. So...
50' full depth span
30' slope span (80' full span)
12'Wx8'xH50'L=4800x2(side slope)=9600
12'Wx8'Hx15'L=1440(slope span)+9600=11040 cubic feet
11040 cubic feet = 408.888889 cubic yards (rounded to 409) = 456 tons = 24 truckloads
17yds = 19 tons = 1 truckload
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