Culvert Life Cycle Cost Analysis 1

[ufcivilengineer]

I've been tasked to come up with a life cycle cost analysis spreadsheet for various existing culverts.
Things to consider:
1) Many of these culverts are large diameter CMP
2) Many of these culverts are already at the end of their service life. Internal corrosion. Bituminous Coating gone on 70%-80% of the pipe.
3) Some of the culverts have been compromised structurally, i.e. groundwater can be seen flowing into the culvert through pipe separation.
4) How do I check for voids around the barrel length?
5) Do I replace them. Line them with HDPE?
6) If we line the culvert, do we pump grout into the voids around the existing pipe exterior.

Any input would be greatly appreciated.

 

[dicksewerrat]

Lining the pipes by CIPP or Fold and Form can be done. Slipline can also be done. Slipline will give you a smaller pipe when completed than the other two methods and you should grout the annular space.
Voids can be found in man entry sizes by the hammer method. I'm not sure if they have a ground penetrating radar they can put in a small pipe. It would be better to fill any voids outside the pipe that can be found. There may be a sonar system out there that would work. There is a trade show in Toronto the end of March where you could learn a lot more. N0-Dig 2009.
The life cycle for all the lining systems would be 50 years and all can be designed as a stand alone pipe.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[WL123]

If you line them will the capacity still be adequate?

How deep are they, replacing with concrete culverts may be cheaper, you may spend more in investigating the existing pipe than just replacing them.

 

[dicksewerrat]

the capacity of the new lined pipe will be greater than to old pipe. Manning's n value CMP = .024, CIPP or Fold and form will be approximately .016. this is due to the smoothness of the liner and filling the corrugations partially. Culverts under major roads can ussually be done in one day. What is the time frame for dig and replace?

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[vie]

It sounds like you have 2 different tasks. Creating a life cycle analysis is typically done considering new pipes. If you have existing pipes that have deterioration are you wanting to determine the remaining service life for the pipe? If so, there are published guidelines from the FHWA for RCP and CSP. Nothing I know of for HDPE yet.

You will have to determine a ranking system for the condition of the pipe. Again, FHWA has this spelled out. Their method allows you know assess the pipe's critical time to when a repair is needed.

I suspect that for large diameter CSP (say over 30 inch) any time the pipe is sloped over one (1) percent slope even with a manning's n of 0.24 the velocities in the pipe will be in excess of 5 fps. This is a MAJOR issue for all CSP with galvanized, bituminous and aluminized type 2 coatings. You loose all the benefits of those coatings with velocities above 5 fps.

You've got a lot of issues to contend with with joint leakage/seepage, especially if the culvert or closed pipe system is over 10 years old.

Lining with corrugated HDPE will be difficult if there is much deflection in the CSP. If over 10% deflection then it is doubtful you will be able to line the CSP with corrugated HDPE. Maybe a solid wall HDPE. There's issues with how far you can push the pipe. Grouting the voids between the pipe is critical AND the method of joining the joints of the pipe is critical. A soil tight type of seal (even if gasketed) will not hold out the grout and the grout will bleed into the inside of the pipe. Personally I agree that removing the pipe is the best option if you can handle the open cut cost.

I'd be happy to talk with you. This is part of my engineering practice and I specialize in pipe forensics, inspections, life cycle cost analysis, regulatory code modification and storm water storage and quality design.

David