How do you do it? Here the most common way I see is for the pipe to run from center of structure to the center of the next structure. The pipe lengths calculated correspond to these distances. That way there is no confusion between the orientation of the structure and the direction of the pipe.
I am working on drawings where the pipe ends at the edge of the structure regardless of whether or not it comes in at a weird angle. I find this annoying because it is drawn to the midpoint of the edge line. The projected pipe would not pass through the center of the structure, so I am left to ponder whether to stake the center of the structure or the end of the pipe. In this case there are curb inlets, so I will have to hold the orientation of the structure with the curb.
The pipe length is the length from edge to edge of structures. They will certainly need a little more than that especially if it comes in on an angle to build this. Which way do you normally do this?
I stake the structures. Offsets for curb inlets are to the centerline of the inlet, inline with the face of curb. Pipe alignment stakes are calculated from structure to structure. The contractor is responsible for the actual connections if they are detailed as specifically as described.
All of that being said, if you contract such detailed layout, make sure your plans give you enough information to pinpoint the pipe ends. More importantly, make sure you are well compensated for all of the added liability you are assuming!
I always do it the way you described. I just feel better about it when it's drawn that way as well.
In my case, I am working directly for the contractor, so I will just have to give the guys whatever they ask for. Either way I'm getting paid for my time so it doesn't matter too much. I just don't want to do it twice.
I'm with Kevin here. I stake the C/L of structures. For curb line CB's I'll set a 5' off back of curb stake too, to go with the regular grade stakes/cut sheet. Let the nerd brigade figure out if the pipe length is ok. Then there are concentric vs eccentric MH's, makes a difference too. Some of those 6' dia MH's really goof things up. Not my problem, here's your C/L & cuts - per plan.
I'm well into 5 digits of structures staked over the years. Only had to "buy" one CB because the plans sucked and I didn't catch the engineers dimensional screw up. Missed the curb by about 20 ft. Still my bad, but CB's then were only around $900. Beer was cold when I got home....;-)
> How do you do it? Here the most common way I see is for the pipe to run from center of structure to the center of the next structure.
For steeply sloping pipes the 2' of extra run may make a significant difference in elevation but if the pipe slope is moderate the difference is within the limit of error. Also may be an issue for 72" and larger manholes. I've seen it done both ways. It's something to be aware of.
As far as CAD goes, I like to run the pipe linework to the center and then use a screening hatch on my manhole symbol to give the open circle appearance.
fist is the pipe supposed to be attached to the outside wall of the box?
and how is that attachment made?
and I do hope your pipe lengths are true slope distances!
slope distances at flow line, especially important when using tapered pipe.
OK, seriously I have seen all of the above...
99% are center of structure. those workmen are smarter that you think.
Dan - we are both in Jersey and most plans I see run from center of structure to center of structure when calculating pipe lengths. I have asked a couple engineers and most tell me that is the way it has always been done.
I have seen it where the pipe lengths are to the true edges of the structure and I just think that in most situations it just complicates things. As another poster mentioned, we stake the structures and worry more about the curb alignment. Of course if we see something that will cause a conflict with another utility we make sure to point it out to our client and the engineer.
Cool....so I'm not going crazy. I thought maybe because the design is from a big international firm they did it the other way in a lot of places, but it seems the way I am familiar with truly is the most common. I feel better about running this one the same way I always do.
> Cool....so I'm not going crazy. I thought maybe because the design is from a big international firm they did it the other way in a lot of places, but it seems the way I am familiar with truly is the most common. I feel better about running this one the same way I always do.
yes there are some watch makers out there... probably best to chat with the on site foreman and make sure that they are getting what they want.
I now remember I have seen highly detailed designs (and staking to match) for multiple pipes with varying inverts and sizes and tight angles between the pipes using precast boxes ... pretty rare I think
Gotta say, it seems as though the contractors we dealt with 10 to 20 years ago really knew their stuff and were good enough to spot problems and pick up the phone and ask questions.
We still deal with some really good guys out there but I am finding that there seems to be a shortage of those guys whether it is curb guys, utilities or buildings.
Just had a contractor give us hell about a long run of stakes for curb that the contractor swears we screwed up. We get to the site to check and I notice that the area in question had decent fills to get to top of curb. Just for Sh**ts and giggles I lay my tape from the top of curb they built to the stake along the slope. None of the curbs had been built at a horizontal distance of 4 feet from the stake - they held the slope distance.
Still gives you knot in your stomach when you get that call even though you are pretty sure your info is correct.
I always stake the structures, let the pipe crew worry about how they tie in the pipe. Lately I draw the structures in so they can see them on their controller and can get the box oriented correctly. I don't know about there, but in Ky. there are several companies that make precast boxes. They have all been approved by the state, but they don't necessarily match the dimensions called for in the plans. Last job I had to get their detail sheets to see exactly what they were sending at each location.
When I used to design storm/sewer runs, I would get the distance from center to center and then round my distances down to the nearest 1 or 2 foot increments. It made all my calculations easier and my slopes were all hard %'s (no 1.333333% and things like that).
Thad
🙂
if the contractor's budget is really really tight I suppose some would consider it better to be dumb and do it wrong, then get paid big money for time delays, demo, and rebuild.
human nature for some low life ones I guess
[sarcasm]I always stake the pipe to the center of the inlets. They can always get in there and jack hammer them back to the sides alot easier than they can stretch that last joint 4 inches[/sarcasm]
True - although in this instance the client made the contractor rip it our and do it again on the contractors dime.
Had an interesting conversation with one of the contractors I really like working with. A client told him straight that while they do great work and everyone knows its right, his bid of 1 million for the site was much higher than another guy who was at $ 800,000. They knew the cheaper group does shoddy work and anticipated about 100k in mistakes. That would still leave them with 100k that they could keep in their pocket. Sad but true