Profiles - Variable offset of profile

[wes.85389]

I've just recently ran into this problem, I can't find the answer anywhere else...

We were recently doing a simple water main extension in a rural area. We wanted to use the centerline of the road as the alignment (since it's an existing road and a good benchmark for the contractor) and show the water main on the roadway celterline alignment and profile. On the roadway centerline alignment and profile, I then wanted to show the profile of the existing ground over the proposed water main. We tried using the "Sample Offset" when creating the profile from surface, but the water main wasn't equidistant from the centerline. I then wanted to just make the watermain polyline into an alignment, but even a slight change to the alignment (1 foot total) would throw off my stationing by 1 foot from the point of the change to the end of the alignment.

Is there a way make a profile have a "master" alignment and then follow a "slave" alignment for a profile display? Similar to how a corridor for a turn lane can follow a secondary alignment when tapering.

You help is greatly appreciated.

[Anthony Rhodes]

Make two alignments. The first (Master) should be the centerline of the road. The second (slave) should where you want the waterline. From there make one profile view for each master and slave that shows the existing grade. Then super impose the existing slave profile into the master profile.

[wes.85389]

Thanks!

I looked into this, but due to the bends and deflections around trees, mailboxes, etc. the "water main" alignment is longer than the "centerline alignment". In a small section I tested, I used a 300' centerline section and the length of the the water main alignment perpendicular to the centerline alignment was 310'. When I superimpose the two, the beginning and ending points, which should be the same, are off by 10'. If I expand this out by a few miles, the distance difference really begins to add up.

I tried to make a few screen captures to upload, but I can't get them to work with the Manage Attachments option at this time.

Thanks for your help!

[Anthony Rhodes]

I am not sure how you can account for the difference in length between the 2 profiles, that is going to be a problem no matter how you draw everything. If I were in your shoes and the decision was on my shoulders I would make the plan and profile sheets run along the water line and show the road in the plan view for reference. I am assuming you are going to have the waterline staked out which should answer any questions the contractor would have about how the main layed out in reference to the road. If you are not having the waterline staked then the contractor was going to "wag" it in anyway and it does not really matter how the profile is cut in the plans.

P.S. For what it is worth if I were in your shoes and the decision about where to cut the profile was not in my hands I would explain the length problems to who ever makes the decisions and let them deal with the headaches. Either way the decision is made and you get to drive on with the design.

[wes.85389]

That's what we have discussed previously, but the Project Manager wants it to reference the centerline. Then we have reviewers who want to see the water main itself profiled. The issue came up when we had to deflect and bend around a nice brick driveway entrance (even if it was techincally in the DOT R/W). The water main alignment was on the back side of the ditch. The bend required the water main to go under the ditch, to the front side of the ditch for approximately 35' and then bend back under the ditch to the backside of the ditch again. The reveiwer wants to see the pipe deflect under the ditch while the PM wants to use the centerline and I'm trying to satisfy both. Thanks for your time and assistance. I'm going to keep looking, but if you have anything else, please let me know.

[BlackBox]

Superimposing one Profile onto another within a Profile View does account for the difference in Alignment Length by projecting the slave alignment Profile onto the master Profile View. This will acurately display all of the bends, etc. of your Pipe Network as seen from the Profile (i.e., the right side) of the master alignment. Even when staking out the utility, stationing is always based upon either roadway alignment, or a survey established baseline in my experience, and never using the actual utility alignment (unless they are one and the same). My $0.02