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Figuring yardage in pond dam

whitemike

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Joined
Jan 9, 2013
Messages
96
Location
South-east Ga.
Occupation
Small land clearing biz owner
I have helped build many ponds with my daddy doing the figuring and bidding on the jobs. He passed away recently and now I need to bid on a job without his help. Here is the info I have the dam is 14' feet across top for 500 '. It has a 4:1 back slope, 3:1 front slope. It is backing up 12' off water at center off branch. Clay is a reasonable 6' deep. I know we cannot get exact amount off dirt needed to build this dam without looking and studying site but can someone give me a guild line _ formular to use to help. He could just look at site and put in bid but he had build many, many ponds in southeast ga. Why don't we say the things we should and ask the questions we could have befor its to late?
 
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norite

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Jul 31, 2010
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483
Location
Sudbury, Ontario, Canada
This is pretty basic math, draw a cross section of the dam with a triangle at least 14' high with a 4:1 backslope, the center section would be a 12' high x 14' wide rectangle and the front section would be a 12' high triangle with a 3:1 front slope. Now work out the area of each section and add the totals together. Then multiply by the length of the dam to get the total cubic feet, then divide by 27 to get the cubic yards.

There are many other aspects of dam construction you need to consider as they can be dangerous if they fail. For liability reasons alone, you or the client should consult a professional engineer and have him develop a plan.
 

bvfdfire

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May 19, 2010
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165
Location
east TX
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project superintendent for highway heavy construct
"This is pretty basic math, draw a cross section of the dam with a triangle at least 14' high with a 4:1 backslope, the center section would be a 12' high x 14' wide rectangle and the front section would be a 12' high triangle with a 3:1 front slope. Now work out the area of each section and add the totals together. Then multiply by the length of the dam to get the total cubic feet, then divide by 27 to get the cubic yards."

norite is right on; however, keep in mind that this will give you the COMPACTED yardage, you need to consider swell of excavated material when you account for your embankment. It varies, but silty sands, and lighter clays should have a swell of about 1.5 to 1.85 % /excavated yard. Another point that you might ponder, the front slope of the dam below water level could be transitioned to a 2:1, this would benefit you in 2 ways, it reduces your embankment needed to complete it, but it also reduces the face area that is directly affected by the weight of the water, which will help increase the holding power of the dam.

The amount of water that you are impounding would warrant doing a little Geophysical study and be sure that you don't trap some gravel bearing sand below your dam and through the clay core which would allow it to leak. And be sure that you've got some good heavy clay to build your central core with.
 

whitemike

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Joined
Jan 9, 2013
Messages
96
Location
South-east Ga.
Occupation
Small land clearing biz owner
Figuring yardage for pond dam

This is pretty basic math, draw a cross section of the dam with a triangle at least 14' high with a 4:1 backslope, the center section would be a 12' high x 14' wide rectangle and the front section would be a 12' high triangle with a 3:1 front slope. Now work out the area of each section and add the totals together. Then multiply by the length of the dam to get the total cubic feet, then divide by 27 to get the cubic yards.

There are many other aspects of dam construction you need to consider as they can be dangerous if they fail. For liability reasons alone, you or the client should consult a professional engineer and have him develop a plan.

Thank you for sharing your knowledge. Now days in our area it takes atleast 6 months to get a permit from the soil & water conservation office. It has to be built to there specs and yes an engineer has to develope a plan. so far the only info i have is those i put in forum. Not to discredit these engineers but sometimes i wonder if they ever leave office and got out in the real world, like to the site. On one job the landowner let timber grow on front & back slope of dam and it went to leaking, it had no core. The owner only wanted wood removed from front slope and leave back alone and natural (it was pretty). The pond had plenty off water-shed which presented a problem.The engineers plan called for core to be 12' wide on the front slope off dam, when water was at max. heigth pond only had 2' off core. Not to mention having to deal with incoming water and the slope. Daddy put engineers plan in glove box and we striped off bar-pit dug down to clay in-center off dam, back-filled and packed it with good clay and for a third the cost we fixed pond. Now if it was a new pond from ground up shifting core to the water side would not be any harder to do. Not knocking engineers here but in this case where was the practicality? I only add this for conversation, it has nothing to do with knowing how to bid on this job. I know there are variables but what is the rate-per-yard in southeast Ga. Since daddy's passing i have only taken on jobs by the hour but it is time to start bidding on the bigger jobs.
 
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da'yoop

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Joined
May 19, 2010
Messages
151
Location
upper michigan
Thank you for sharing your knowledge. Now days in our area it takes atleast 6 months to get a permit from the soil & water conservation office. It has to be built to there specs and yes an engineer has to develope a plan. so far the only info i have is those i put in forum. Not to discredit these engineers but sometimes i wonder if they ever leave office and got out in the real world, like to the site. On one job the landowner let timber grow on front & back slope of dam and it went to leaking, it had no core. The owner only wanted wood removed from front slope and leave back alone and natural (it was pretty). The pond had plenty off water-shed which presented a problem.The engineers plan called for core to be 12' wide on the front slope off dam, when water was at max. heigth pond only had 2' off core. Not to mention having to deal with incoming water and the slope. Daddy put engineers plan in glove box and we striped off bar-pit dug down to clay in-center off dam, back-filled and packed it with good clay and for a third the cost we fixed pond. Now if it was a new pond from ground up shifting core to the water side would not be any harder to do. Not knocking engineers here but in this case where was the practicality? I only add this for conversation, it has nothing to do with knowing how to bid on this job. I know there are variables but what is the rate-per-yard in southeast Ga. Since daddy's passing i have only taken on jobs by the hour but it is time to start bidding on the bigger jobs.

I don't know if this will help you or not when it comes to figuring out how much to charge but could you go back and look at some of his previous jobs to see how much he charged for them?
 

whitemike

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Joined
Jan 9, 2013
Messages
96
Location
South-east Ga.
Occupation
Small land clearing biz owner
Good thinkn, my sisters & I do have mountains of paperwork we are going though now. In his bill book the jobs he had bidded on will state the landowners name, and the agreed apon price. Not much info on paper it was in his head. Thank you
 

norite

Senior Member
Joined
Jul 31, 2010
Messages
483
Location
Sudbury, Ontario, Canada
Bvfdfire is also right on. I didn't go into a lot of further detail as it was not apparent that the o/p knew enough how to properly construct a dam and I was trying to encourage him to consult an engineer so that the dam would be designed properly.

whitemike, you need to look at the old jobs your dad did, see how he did them and sort of reverse estimate the jobs. Since you say you have records of the final prices, you need to look at the jobs and come up with some unit prices for excavation, haulage, grading and compaction per cubic yd. which you can then apply to new jobs that come your way. Good luck and remember when your Dad was starting out he probably didn't have all the answers either, by experience you will learn. Good luck.
 

DPete

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Feb 21, 2007
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1,677
Location
Central Ca.
V=(h) A1+ A2 divided by 54....volume = height X ( area of the top + area of the bottom) divide by 54 will give you cu. yds. Remember to dig a core and calc the fill for it . That will be compacted fill yards you need to multiply by 20 or 30% depending on material to get cut yards, at least that's how I do it. Clear as mud I bet LOL
 
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Tinkerer

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The shore of the illinois river USA
Another point that you might ponder, the front slope of the dam below water level could be transitioned to a 2:1, this would benefit you in 2 ways, it reduces your embankment needed to complete it, but it also reduces the face area that is directly affected by the weight of the water, which will help increase the holding power of the dam.

For safety reasons and liability a 2:1 slope should have a 3:1 or flatter area from a few feet below water level to the top of the pond. Also a safety ledge a minimum of 4 feet wide at the top of the 2:1. The reason being , a mower sliding down a 2;1 or children wanting to go wading. I have never finished the slope on a pond or borrow pit that the safety ledge was not required.
 

Scrub Puller

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Mar 29, 2009
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Gladstone Queensland Australia
Yair . . . Dunno Tinkerer

it also reduces the face area that is directly affected by the weight of the water, which will help increase the holding power of the dam

On reflection do you think the above statement by bvfdfire is correct . . . anyone else care to comment.

Cheers.
 

lumberjack

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Dec 24, 2011
Messages
1,044
Location
Columbus, MS
The lateral force of the water doesn't care if the dam's face is vertical or just above horizontal. So in that respect, it doesn't lessen the lateral (blowout) force.

The flatter the angle of the face the more girth and mass the dam has, which will increase its holding power due to the lateral force being absorbed by more girth.
 
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