Looking for some input on sewers

[EMS_0525]

My company does alot of storm and sanitary gravity sewers. We are trying to get all the styles set up for C3D. There is kind of a debate whether or to label from center of structure to center of structure, or inside wall of structure to inside wall. What is the normal? Some clients want one way some want the other. How does your company deal with it? Among this our company is getting into standards issues.... i have just come to the conclusion that there isnt standards at any company... Another question comes to my mind, im a very mechanical person, i work on all my own cars, do all my own work in my house... and i got to thinking how would i build sewers. What good is the center to center distance and elev.? If i was building it i would want from inside wall to inside wall... but how are they actually constructed? Any ideas? Inputs? would be great.

[lpseifert]

Station from center of structure to center of structure. Dimension pipe from inside face to inside face (horizontal distance).

[ReMark]

I worked in a municipal engineering department for eight years. It was our standard practice to dimension center-to-center between manholes on our sewer hub maps. What good is that? When you send a crew out to dig up the sewer the only points of reference are the manhole covers at the surface. Elevations at the center of the manhole indicate depth relative to grade. Subtracting the invert elevation of the lower end of the sewer from the upper end and then dividing by the distance between manholes gives you the slope (or pitch) of the sewer line. You can calculate depths of any point on the sewer line between the two manholes using this information.

 

How our sewers constructed? Basically the contractor sets the manhole first then starts installing his sewer pipe towards the location of the next manhole in line. Do you need a more detailed explanation?

[EMS_0525]

I worked in a municipal engineering department for eight years. It was our standard practice to dimension center-to-center between manholes on our sewer hub maps. What good is that? When you send a crew out to dig up the sewer the only points of reference are the manhole covers at the surface. Elevations at the center of the manhole indicate depth relative to grade. Subtracting the invert elevation of the lower end of the sewer from the upper end and then dividing by the distance between manholes gives you the slope (or pitch) of the sewer line. You can calculate depths of any point on the sewer line between the two manholes using this information.

 

Than center to center sounds good for as built information. But im still not seeing a benefit of designing that way, center of structure is an arbitrary point, inside wall is not.

 

How our sewers constructed? Basically the contractor sets the manhole first then starts installing his sewer pipe towards the location of the next manhole in line. Do you need a more detailed explanation?

 

I know they use lasers to make sure slope of pipe is what is supposed to be also. The contractor wouldnt stick a 8" sewer pipe to the center of structure to get the elevation. the pipe would end at the inside wall.

[ReMark]

Nowadays the contractor ends the pipe just inside the wall of the manhole. But back when men were men and lasers were science fiction for the most part the sewer pipe was run right to the center of the manhole. Then the mason (don't see too many of these on a sewer job any more) would remove a portion of the top of the clay pipe (prior to the use of pvc) and create a shelf on either side using mortar. I know this for a fact as I had seen it done and as a member of a survey crew climbed down inside a manhole to straddle the pipe centerline with a foot on the shelf to either side of the pipe to shoot inverts! This was prior to OSHA treating manholes as confined space entries. Heck, we'd pop the MH cover, wait 10 minutes, then I'd climb down inside! Scares the hell out of me now just to think about it. The deepest manhole I ever entered was almost 28 feet. Had to tie two ladders together to gain access and we used two 16 foot rods (one held atop the other) to shoot the invert! The sewer was cut through solid rock and passed under a cemetary. Ah...the good old days.

[eldon]

Looking at the thread title, it did cross my mind that we all contribute daily

 

But to matters more mundane, sewer pipe runs are not necessarily constructed to the same exacting standards as wrist watches. As long as there is a hole in the ground, which generally is sloping at a self cleansing gradient, that is good. The siting of manholes is governed by surface restrictions, and a manhole cover may not be over the centre of the manhole chamber. It is usually the man in the field who puts it where he can, thus resulting in the need for as-built surveys.

[EMS_0525]

Very true, but when setting up pipe structures library you need to tell it to do center to center or inside of wall... its all in the style. I know there is a difference in how close things are designed and how its conctructed, im working on a site with 3 baseball fiields and the grading is crazy, i know it will never get built like that....

 

This is all coming from how we set up our pipe networks in C3D.

[ReMark]

I freely admit to contributing my fair share.

 

True. Manhole covers are usually found to be shifted off-center more often than not. This is to facilitate access to the cast-in-place rungs found on most precast manhole sections (base, middle and tapered top).

[ReMark]

I don't use C3D so maybe you can educate me. What scale do you use to draw your sewer profile? We went by ConnDOT (Connecticut Department of Transportation) standards that called for a 4 (vertical) and 40 (horizontal) profile. One town I know of insisted on using a 5 and 50 profile.

 

Let me ask one more thing. Are you old enough to remember plan and profile paper with its distinctive pale red lines in the profile? OK...I'm dating myself.

[EMS_0525]

Its a C3D "style" you can tell it to label from center to center or inside wall... its a pipe network issue.... the scale of the drawing has nothing to do with it... im not sure of the scale my company uses though... we are trying to get standards ironed out... thats the reason for this issue. I believe we use 5 and 50.... not sure... im new here.

 

Remark i see you have a CB700... I have a '80 CB750K. Im only 26 BTW... that honda is older than me....

 

I have not done plan and profile dwgs by hand.

[ReMark]

Thanks for the information re: C3D. Maybe someone else will join in on this little side discussion.

 

My motorcycle is younger than me. Your motorcycle is older than you. I'm pretty sure I'm older than you. Maybe we should switch motorcycles? Although, I do love my sport bike.

[EMS_0525]

My true love is my street legal dirt bike....

 

ah... side tracked again.....

[ReMark]

That's how I started out...in the dirt! Yeah. Mud, water, trees, sand, dirt, logs, rocks and of course, my favorite of all, BUGS! Well there was that ONE time a wild turkey got in the way. And no I'm not speaking of the drinking kind.

[rustysilo]

I would set up styles for both c/c and inside face of wall, then just ask the client how they want theirs done.

 

I think for asbuilts it really wouldn't matter all that much, but you might want to use the dim from the inside face of wall for accuracy's sake.

 

In a design situation it would depend on how accurate you want the lengths to be, and the structure size and shape. The only time this becomes a concern is when you do your estimates as far as I can tell. Some might want their estimates to be right on. Others might want their estimates to have the overage cushion that measuring c/c would afford.

 

I guess another thought is whether you're using the 2d length or 3d length. If giving 2d length then going c/c would accommodate the difference in the 3d (actual) length.

[Tankman]

Looking at the thread title, it did cross my mind that we all contribute daily.

 

Quite often more than once a day, depending on the reading material available.

 

There are guidelines for the pipe incline, the "stuff" does need to flow freely.