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.
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.
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.
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.
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.
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.
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...
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......
:bouncegri Oh, will this never end??? (...here's hoping not!) :yup
How our engineer stakes our CB's. 10' and 15' offset stakes to the center of CB
so do you have to make offsets of your offset stakes so you can dig past them?
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.
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
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.
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.
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.
ROFLMAO :lmao :lmao :lmao
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
ok, all of this has helped very much, but: 1. How do you determine where the face of the curb is going to be if there are no roads or even centers of roads established? If you were to go into a field with nothing but 1 10' offest on the right (outside of curb) and one 10' offset to the left (in the road), how would you determine what is square if there is NO road yet to pull off of? 2. Centerline stakes would be a huge luxury, but most disgruntled surveyors just want to get in and out. And why don't ALL the surveyers just write the cut on the stake?? You would still number them and have a log of what cut went at what stake, but there would be no waiting on the cutsheets in the trailer:Banghead
sounds to me as though you need to educate the crew doing your staking for you. the ones we work with ask us how we want it staked, give us the fill/cuts, AND stationing on each stake so we know they haven't been moved, plus leave us a permanent elevation benchmark somewhere close by so we can double check their stakes to see if somebody played with them.
I am a little suprised after reading the posts in this thread. It sounds like the Engineer will layout most of the projects. Here all we ever get is an elevation TBM and two control points. All layout is up to the contractor. I layout the project myself paying close attention to the C/L. At first I did not like being responsible for layout, I always thought that the Engineer was paid to design the project, he should at least do the inital layout. Now I kind of like doing the layout. About 80% of the time I find a mistake in the plans. This usually results in a contract change order. If the Owner's Engineer did the layout I may not have gotten the change order. On one project last summer if I had installed a culvert per plans specs. it would have stuck 8 inches above the finished road. We called it the "speed bump culvert". On that project there were so many design flaws it got to be a real pain. Sorry if this got off track, setting a CB is not hard just pay close attention to the C/L and TBM.
I may be confused with the style of CB you are using but how do you determine the elevation of the inlet? Every project I have seen the gutter determines were the exact elevation of the pavement and corresponding drainage inlets. I know elevations are given by the surveyers but if the concrete is off elevation by even a tenth or so drainage may be inhibited. I understand the may be adjusted as the concrete is placed. If these are in valley gutters or where asphalt will be placed you may be able to raise the CB after they pave over them. Either way the elevation of the CB is must allow for proper drainage from either the pavement or gutter. THe only way I can see that the elavation may be not entirely precise is if this CB is off pavement such as in dirt or landscaping. -Ryan King
The boxes are marked on the plan for having a certain elevation, typically the inlet of that box. Take the box required for that cut, subtract the thickness of the floor plus some for gravel base, and that is bottom ofthe cut. The size, shape and height of that box is determined by what is needed to come up to finished grade. A box could be 3' or 30' deep, depending on finished grade and where that is in relaiton to sewers flow
if you're finding problems with engineering/staking on 80% of your jobs, you need to sit the owner of these projects down and explain to them they need to be hiring a different engineering consultant. that is totally absurd!! unless you had pipe installed that had to be dug up, relaid, catch basins precast that are wrong height, etc., it's funny they're giving you additional money in the form of a change order unless that error cost you financially. unless there was time lost due to demobilizing/mobilizing to the jobsite because of having to wait for specialty items, you'd never get that accomplished here. i must be fortunate in working with very competent engineering companies. we just don't run into that kind of headache here. if there is a little snafu, and can be resolved in short order, the last thing i want to go do is beat the owner up for more money if there's really no big loss of money involved, it sheds a bad light on the engineer, and if i'm always begging for extra money, me.
Dayexco- we've been sharing in a post on General topics regarding shallow digging/utilities. A post you made stated: " last week we were installing a 10" sanitary sewer main 13' deep in a development. in the alley we approached, we encountered a cable tv wire, 3' away, a competitor's cable tv wire, 3 ' away a telephone cable, 3' away a 4" gas main, 3' away a primary power cable...try getting a trench box under that, an excavator bucket in between them, compaction equipment around or underneath them...a real headache. proper planning on their part would have put all the wires in one duct bank or trench, and the gas line 3' away from that, making only 2 items to jump, work around. it's really getting to be a headache in my neck of the woods with this problem. any of you encountering the same? " Under this Centering Catch Basin thread, you question if compensation should be considered unless possibly mob/demob is involved or financial burden incurred. I would contend that the utility situations you mentioned in General above listed thread are significant financial burdens to your firm incurred due to time and overhead expended doing "dirt surgery" around them. Do you guys go into a job with a "bump up" factor in bid (and thus risk not getting the project in low bid scenarios!) for "unforseen" utility situations. If so, how do you quantify such (please forgive me- i'm not trying to pry into your company's strategic decisions here)? We are not allowed in Texas One Call Law to request locates for utilities for design work-only construction. Thus as the contractor i'm at the mercy of the engineering firm/owner to give me a "clear" job or show no utilities whatsoever on the plans and let me take my chances. If they show a partial utility locations on plans, am I not bound contractually that's what's in the ground? And if I find utilities that even the owner/operators of the utilities don't know about, do those things not also affect the critical path? Being long winded here- please don't think i'm being confrontational, but rather trying to understand construction contracts around the U.S. I do understand that there's a relational balance with owner and engineer and that actions today may have adverse (or positive!) reactions 5, 10... years down the road in terms of business relationships. I suspect this depends on the project, but does your company have any general rules of thumb related to how much delay/overhead overruns you'll accept on a job before requesting change orders? Returning to focus on Jim's last 2 points: 1. On DOT projects here in my area of TX (at least the ones i've seen), all that exists prior to construction staking of the proposed roadway are a series of "H" points (hubs on the ground- and not necessarily on the roadway CL). TxDOT specification i believe requires points spaced no greater than every 1500'. All points have an XY (or NE if you prefer that nomenclature) and an elevation. They are the primary control from which all existing and proposed features are developed. One other post mentioned 2 points and i suspect that works pretty well although additional points provide redundancy in the event of destroyed primary control and for additional construction staking checks. HOPEFULLY, your engineering firm which designed the job will post enough data in the plan set to layout any feature of the project by merely reading the plans. I submit that many firms do not have engineers with enough "trench time" to understand your particular needs for staking etc. This goes back to the education of surveyors (and engineers!) that Dayexco and others stressed. Most jobs today are semi-complicated and more detailed due to computer aided drafting and design software. One reply indicated a desire to perform staking himself in lieu of the surveyor. I concur, as i think it makes me a better contractor as well as civil engineer. However, obvious risk is applied to our shoulders in this situation and that level of risk will be different for each company. Also requires me to brush the dust off the old trigonometry books from school!! Anyway,some folks want to move dirt, not survey, and i respect that. Given the horizontal control of the job, some location feature of your basin can be given an XY coordinate in space (in the designers CAD file). If the roadway has a horizontal alignment on the plans (CL alignment), trigonometry provides us with a station and offset to that point of interest on the basin. I cannot answer specifics about your particular curb offset situation, but for any point i need to lay out on the job, the following is true to my knowledge: I can set a total station on a known xy coordinate and backsight another known xy coordinate (how convenient that the "H" points are there for me!). This establishes a 0 bearing line . If i know the desired XY coordinate of the point to lay out (CL basin, 10' o/s hub, corners of box, etc...), trig gives me the angle i need to turn with the gun and also the distance along that angle that i need to pull from the pin that the instrument is on to lay out the point. We always attempt to get cadd files from engineering firms for jobs to assist us in the development of construction staking in the event that the plans might lack a station/offset or two. However, the cadd files are merely a supplement, not to replace, the paper plans. Having the cadd files often allows us to check xy's or sta/offsets provided by the engineer prior to our stakeout-not to take the responsibility off the designer, but as one post indicated, we might be able to find something in the plans that helps us to be a better "partner" on the job....... i apologize for being long-winded
my father started in the underground biz in 47, i'm 53, been doing it all my life, i took over the biz in 1980. my son is 28, has been working full time during school summer break since he was 13. so he has probably as much experience as many people my age in the business. that said, i can see by the posts that we're very fortunate here having the engineering companies that we do. we typically don't run into too many situations that require a major overhaul of the job or the request of a change order. and i've also found that by working with the engineer on smaller snafu's without bringing it to the attention of the owner of the project, that we've built a good working relationship with these engineering firms that in turn has brought us many referals on future projects. the prior post on the utilities being in in conflict with our construction. we are allowed to do a pre-bid locate, although you won't get it in the 48 hr. time frame. on the particular job i was talking about, i was aware they were there, and we bid accordingly. that was not the primary focus of that post. the focus was that those utility owners could do some planning as to the placement of their utilities just like everybody else and reduce the risk of damage to their utility, and making it easier on us.
dayexco I believe that you read more in to my post than was there. I have always considered an Engineer to be a Professional. My opinion has begun to change. What I have been finding in rescent contracts are simple mistakes. Usually they are mathmatical mistakes in elevation or alignment. A square peg will not fit in a round hole. Most of them I will point out in the pre-construction meeting, as I will double check everything before I put a blade in the ground. Others are not found till work has begun. A change order does not automaticly mean more money. It means there has been a change to the specifications in the contract. At the completion of a contract I am required to submit a set of redline drawings. My final survey points must match the contract drawings. If they do not then there had better be a contract change order stating that there is a change in the drawings, or final payment and retainage is with held. Because I do all of my own surveying I usually find the mistakes before they become a problem to me. I do not bury pipe and then have to dig it up. I do not try to beat up the Owner over a change order for more money. In fact I have a reputation with the Owners and Engineers in this area as being easy to work with. I have given away enough money on contract change orders doing them for free to pay for the new dozer I have been shopping for. Because of this I have been invited to quote work for Owners I have contracted to in the past that I would not have gotten. I have a reputation of doing good work as well as being fair and honest. The two points I was trying to make were here Contractors are required to layout their own work, and as of the last few years I have been seeing a lot of design mistakes, either in elevation or alignment. A mistake means more paper work for me. not more money. I can only remember one change order resulting in an increase to the contract price. It was a little too big for me to write off. It involved 23,000 yds. of cut and compacted fill. It was also the last project the designing Engineer did for that Owner.
Dave- you mentioned that you prefer to do your own layout work. Do you use total stations or RTK/GPS for most of your stuff? thanks
ForsytheBros, I am still in the dark ages, I use either a Sokkia transit or a Lecia total station. Leica has a "Smart Station" that is RTK/GPS based, I have been researching. I am just not ready to make that big of an investment yet. It looks like a fast system. Most of my jobs may not have enough "clean air." McAninch did a 9 mile addition to a highway close to me. They use a GPS based system. Watching them use, I can see that it is the way to go. Maybe some day I will work up the nerve to change.