Centering catch basins.

[biggixxerjim]

I was just wondering if any of you could clarify something for me. As far as catch basins go, I know that there are 2 hub/offsets that you dig your basin to. However, how do you know when the basins you put in the ground are going to line up right with the edge of the curb/roadway??


Thanks guys.

 

[digger242j]

I guess that would depend on where the offsets are put in, relative to the gutter line. Are there any centerline stakes, or have the truck drivers run them all over? If you know the centerline of the road, and the width of the road, then you should be able to figure out where the gutter line is.

I'd think (although I can't say that everybody would do it this way), that the offsets would be for the actual gutter line, because that's what the surveyor knows. He doesn't necessarily know the thickness of the catch basin wall, which he would have to know if he were giving you offsets for the actual outside of the box itself.

 

[RyanCKing]

Install them after the gutter is installed. Extend the drain pipe past the point where the CB will be. Make sure you have plenty to work with. After the curb and/or gutter is placed install the catch basin. This will probaly involve cutting the curb and/or gutter and replacing some of it. I am not sure of the type of Catch basin you are using but this should work with all.

 

[digger242j]

Install them after the gutter is installed.

We don't have many of the details of this particular job, but I have a hard time believing any inspector would go for that solution. Not to mention that if there's a separate subcontractor doing the gutters, he's not going to remobilize to patch into your catch basin for nothing.

 

[ForsytheBros.]

Jim-

down here in TX, i assume you're referring to "curb inlets" on curb and gutter sections of roadway? Not sure how your construction staker is preparing your offset hubs, but my opinion is to run two offset hubs to the front of the box (parallel with the curb line). Hubs would correspond to begin/sta of the box and be at some prespecified offset from the c/l or edges of box but having the same bearing as the curb line.


PS- i think i'm sort of repeating what Digger is going after so maybe i'm not providing a new thought here.

 

[dayexco]

if you are refering to what we call a "type b" basing...a 2'x3' inside measurement basin, to make your castings work out, the back of the inside of the box is typically the back side of your curb. we always have the engineer give us offsets to establish the back inside of the box, works good for us.

 

[digger242j]

A picture is worth a thousand words. This is what dayexco, ForsytheBros, and me, are all talking about. Correct?

On edit: I probably should have called out the distance the stakes were offset, but you get the idea...

 

[ForsytheBros.]

Yes siree Digger- Perfect, thanks for the illustration.

Obviously if the curb line is in a tighter radius curve , placing the hubs closer to the outside walls (longitudinally) of the inlet helps the "chord" approximate the curb curve radius better......

 

[Dickie]

Are there any centerline stakes, or have the truck drivers run them all over?

:bouncegri Oh, will this never end???


(...here's hoping not!) :yup

 

[tylermckee]

How our engineer stakes our CB's. 10' and 15' offset stakes to the center of CB

 

[tylermckee]

A picture is worth a thousand words. This is what dayexco, ForsytheBros, and me, are all talking about. Correct?

On edit: I probably should have called out the distance the stakes were offset, but you get the idea...

so do you have to make offsets of your offset stakes so you can dig past them?

 

[digger242j]

But Tyler, that way how do you know you don't have it cockeyed with respect to the gutter?

And yes, sometimes you have to reference the offset stakes, but with your method, what do you do for CBs that have pipe crossing the street directly from the left one to the right one?

 

[tylermckee]

But Tyler, that way how do you know you don't have it cockeyed with respect to the gutter?

And yes, sometimes you have to reference the offset stakes, but with your method, what do you do for CBs that have pipe crossing the street directly from the left one to the right one?

usually be staked the same way, 10 and 15' offset stakes to the center of the cb, except the stakes will be off of the other side. He always runs the stakes perpendicular to the basin, so we just eyeball it up square with the stakes and call it good, any minor adjustment we get with risers. Its been working for us.

 

[RonG]

The diagram that Tyler provided would be the preferred way to do it except that the offset measurement should be from Face Of Curb,not the center of the structure.That way you can line it up with the correct gutter profile by measuring to the center of the catch basin top,both the front and back and the surveyor will have set your offsets exactly 90 degrees from the curbline.
Any other solution pretty much has you destroying your reference while you excavate the hole unless the offsets are a good distance away.As I remember the FOC is pretty close to 12" beyond the back of the riser.If I have any questions or forget after not having done one for a while I assemble it on top of the ground and measure it.Ron G

 

[ForsytheBros.]

This begs another question: Do you guys do most all of your construction staking or sub that out? And if sub'd out, how close are you to your surveyor that you get the most valuable hubs set w/o extraneous information or hub locations likely to get destroyed?

 

[dayexco]

This begs another question: Do you guys do most all of your construction staking or sub that out? And if sub'd out, how close are you to your surveyor that you get the most valuable hubs set w/o extraneous information or hub locations likely to get destroyed?

i'm a touch confused here. typically, the owner of the projects we work on provide their own staking, quality control techs. the only info placed on our stakes, is fill/cut, and distance of the offset. i work in a small community "20k people", so the 2 dif engineering firms we work with normally are available on a 1/2 days notice to stake for us, and usually don't stake more than a day ahead of our work. i guess we don't have much of a problem with stakes being destroyed.

 

[dayexco]

The diagram that Tyler provided would be the preferred way to do it except that the offset measurement should be from Face Of Curb,not the center of the structure.That way you can line it up with the correct gutter profile by measuring to the center of the catch basin top,both the front and back and the surveyor will have set your offsets exactly 90 degrees from the curbline.
Any other solution pretty much has you destroying your reference while you excavate the hole unless the offsets are a good distance away.As I remember the FOC is pretty close to 12" beyond the back of the riser.If I have any questions or forget after not having done one for a while I assemble it on top of the ground and measure it.Ron G

we have our offsets spaced at 20' leaving plenty of room to get machinery in there to excavate the hole. everybody does it different the way it sounds, but all of our engineering firms here stake the offsets to the inside of the backside of the catchbasin being installed. placing the basin isn't rocket science, i've seen where there are utility conflicts where the utility couldn't be moved, that the castings were offset off the basin by as much as 6" and mortered back in.

 

[ForsytheBros.]

Dayexco-

sorry to confuse. A significant portion of our background is municipal or public work. Most of what we see is Owner=>Engineer=>Contractor

Typical scenario for us is for job specifications to have Owner/Engineer provide initial horizontal/vertical control , with the responsibility for staking put on the contractor (via either in -house guys or contract surveyors). We always ask at a pre-bid for the owner to freshen up the original control points to reduce time/$$ for us finding it prior to stake-out.

 

[Squizzy246B]

Are there any centerline stakes, or have the truck drivers run them all over?

ROFLMAO :lmao :lmao :lmao

 

[RonG]

If you measure the long side of the catch basin top where it meets the pavement and divide it by two and mark the center of it,likewise measure the back side along the curbline and mark it also in the center the only dimension you really have to know is your offset to face of curb.If you pull your offset with the twine going directly over the center of the catch basin top using the centerline marks you made directly under the twine and you measure 10' back to your first offset stake or whatever distance they provided then you have nailed it.The only variable now is elevation but using this method you can set a basin within a fraction of an inch without much hassle.Of course it goes without saying that you can only be as accurate as the surveyors offsets as they have to be 90 degrees from the curbline for this to work.Ron G