Creative solutions

By Timothy Allinson, P.E.

Murray Company, Long Beach, Calif.

I would like to take this opportunity to wish everyone a Happy New Year! Let's hope 2009 ushers in a better economy under our new presidential leadership. We certainly could use it!

I was recently faced with an unusual problem on a project that required a creative solution. We were in the process of installing the underground piping for a fairly large design-build project. One of the first things we do in the shop drawing process is to produce canning sheets - the drawings that indicate all the required pipe sleeves. These drawings are produced by our detailers from the design drawings prepared by our engineers.

In this particular case, an 8" sanitary drain had to be sleeved through an 18-foot long grade beam. The sleeve for an 8" pipe should be at least 10" in size. As human nature sometimes holds, the detailer erred and accidentally indicated the sleeve as 8" on the canning sheet, rather than 10". He had called out the pipe size on the sleeve rather than the proper sleeve size.

The canning sheet was issued to the field, the long sleeve was installed in the wrong size, and the mass of concrete was poured around it. Shortly thereafter, the error was realized, and the detailer came to me very upset to announce that he had screwed up.

We looked at the problem every which way and sideways. We tried to go over, under and around the grade beam, but there was no way of getting past it. We considered what it might cost to core drill the grade beam to a 10" diameter, and both shuddered at the thought of the expense. Then a light bulb went on.

"What's the sleeve made out of?" I asked him.

"Steel," he replied, "schedule 10."

"Maybe we can use the sleeve as the pipe?" I suggested.

We mused over the possibility for a few minutes and discussed how this might be executed.

"The steel would have to be lined," he pointed out. "It's not galvanized."

"And it would require a variance from the City," I added.

I got on the phone with SOS Pipe Restoration and asked whether they could line the pipe in short order, the answer to which was, thankfully, "Yes." I then called the City and was told that a variance would likely be granted if I filled out the necessary forms, provided technical information and furnished the obligatory check, which I did the next day.

The day after that, the pipe restoration company showed up to line the pipe, but they had brought the wrong material. The proper material had to be sent overnight from Florida for installation the following day.

Over the weekend, an engineer from the City's mechanical test lab witnessed the installation and pressure test. The entire installation was blessed, and the problem was solved. However, there remained one technical issue that was bugging me. I asked the pipe restoration guy, "What happens if the outer surface of the pipe corrodes? After all, only the inside of the bare steel was lined."
The pipe restorer informed me that the product (called Permaliner) was so substantial that it would maintain the pipe integrity even if the entire pipe around the liner were to corrode and crumble away. For this reason, they use it to restore vitrified clay pipe. Once the liner is in place, the clay pipe can deteriorate entirely, and the liner will remain intact.

I was still concerned about possible shear forces years down the road that might fracture the pipe liner during ground settlement, if the steel pipe were to corrode and lose its strength. So we elected to pour a mass of concrete around the exposed steel to support the liner, should the steel eventually corrode.

By now, the entire underground system is installed, backfilled, the grade slab is poured, and the building is going up above. The reason I share this story is to demonstrate that creativity and resourcefulness can be used to solve the most challenging problems, even in our seemingly mundane, but beloved, plumbing industry.

Timothy Allinson is a Senior Professional Engineer with Murray Company, Mechanical Contractors, in Long Beach, Calif. Prior to entering the design--build industry he worked for Popov Engineers, Inc. in Irvine, Calif, and JB&B in New York City. Tim holds a BSME from Tufts University and an MBA from New York University. He is a professional engineer licensed in both mechanical and fire protection engineering in various states, and is a leed Accredited Professional. Tim is a past-president of ASPE, both the New York and Orange County Chapters, and sits on the board of the Society of American Military Engineers, Orange County Post.