Sump/Baffle box in a drainage ditch

[SSAuburn]

I'm trying to add a sump/baffle box to a drainage ditch.  I'm confused about what is the best way to go about this.

I'm taking this project over from someone else.  They had created a surface. However, I'm confused about how the surface they made was created, but I have used it to give me a reference to were the sump is located on the profile view. (circled in blue).  Currently that surface has wall that are 1.5' high with a bottom at -1.5'.  I have drawn in the sump on the profile view (highlighted in yellow).

I have tried to start over by using breaklines.  I have already created a standard breakline on the N and W side at 0.  However, on the east side I can't figure out how to create a breakline and keep the drainage basin grading to the exisitng drainage basin grade.

I have attached screen shots of the plan and profile view. 

[Joe-Bouza]

I'm confused to what your question is? do you want to create a structure or know how to grade the ditch? what is the phantom line and the blue circle area of the box?

[john.mckenzie]

So the sump baffle box. What is it going to do. is it to direct flow to a pipe?

Are you trying to direct flow until it reaches a certain elevation in the ditch and then have the excess flow travel further downstream via the ditch?

the surface looks like an existing ground surface but. That can be deceiving depending upon the style applied.

I would recommend doing a couple of things.

1.

If you are confused as to how the surface was created, you can check to see if it is xreffed or data shortcut into the current dwg. Follow the clues back to the source and investigate. There will be a trail. Not always clean and clearcut but you should be able to determine how the surface was built to a reasonable degree of certainty.

2.

If you are accepting of the surface data as is and want further assistance, we will need to know exactly what you are trying to accomplish with the bafflebox.

Because right now, I am the one baffled. LOL