Research and development
The article, "Hidden Savings" (CE News, October 2006) was very interesting. I work for a structural engineering firm (four owners and 12 employees) in Seattle. During the last two years, we have spent many hours developing a library, or a "model set," of typical or template AutoCad details for our engineers’ use, which will improve efficiency and accuracy of the development of our structural drawings. We are also in the process of developing a model set of engineering spreadsheets (in Microsoft Excel format) to perform wind, seismic, and gravity analyses for every aspect of our designing process. Does the time that we spend on the development of these qualify as research and development (R&D), or does R&D always have to "answer questions about uncertainties"?
The costs for the template to improve the efficiency and accuracy of the development of the structural drawings probably wouldn’t be considered for the R&D costs. However, the costs associated with the work to perform wind, seismic, and gravity analyses will most certainly apply as an R&D activity. The general theme is that R&D activities are applicable when they are designed for answering/resolving technical uncertainties. So, what you want to look for are areas where you were able to overcome an uncertainty through your design process. Keep in mind that the improvement doesn’t have to be major; slight incremental improvements are fine. Also, keep in mind that the development costs have to be your burden and not reimbursed by a client. It has to be at your risk.
Paul L Peterson, CPA MBA
Wiss & Company, LLP
Your article, "Dangerous dams" in the [February 2007] issue of CE News was very interesting. In July 2003, my daughter and three friends inadvertently canoed over a low-head run-of-river dam on the Vermilion River in Danville, Ill., and one of her friends drowned. As a result, I applaud your efforts in educating and publicizing this issue. I wish I could say that that dangerous dam has been removed or modified to become less of a public safety hazard. I cooperated with the owner of the dam and spent time on a technical advisory committee regarding this dam. Ultimately, funding is needed to remove the dam and increase public safety on this popular recreational stream.
Karl Visser, P.E.
Thanks for your kind note. Each year for the past 15 years, we have dedicated one class in hydraulic engineering at Rose-Hulman Institute of Technology to educate our civil engineering students about the dangers of low-head dams. Needless to say, getting the word out that way was a slow process. CE News reaches 50,000 subscribers, most of which are practicing civil engineers. Perhaps the article will mobilize engineers in concert with low-head dam owners to remove or modify these "drowning machines." The lives that could be saved are so much more valuable than the cost of rehabilitation.
Michael Robinson, Ph.D., P.E., and Robert Houghtalen, Ph.D., P.E.
I was immediately drawn to your article on low-head dams since 50 years ago I designed two dams for water supply. One is 10 feet [high] and the other 12 feet. As far as I know, they are still there. They are ogee sections. I don’t suppose that affects the hydraulics very much. I have no idea if they have ever drowned anyone. You mention retrofitting to mitigate the hazard and you suggest large rip rap. Would precast concrete chunks do the job? Large rip rap might be hard to find in some areas. I first thought of tetrapods, but they would probably be hard to get and unnecessarily expensive.
Richard O. Albright
I am sure there are many engineers who have unknowingly designed these structures or have clients that own them. You are correct to note that ogee spillways do not inhibit the formation of the dangerous "hydraulic" formation, depending on the depth of the tailwater. However, ogee sections can be modified to remove the drowning danger. I have every reason to believe that precast concrete chunks would work as well as large riprap.
Robert Houghtalen, Ph.D., P.E.
I enjoyed the article on dangerous dams as it brought some interesting memories back from my childhood. I was in my early teens and swimming with a friend in central Kansas. We decided it would be pretty cool to fake a fight while walking along the top of the dam and simply to jump over the edge of the 4- to 5-foot drop to the downstream side of the dam. I slipped on the moss-covered surface and fell into the water directly at the base of the dam. I was a very strong swimmer and had very little concern on the way down. After the splash though, I struggled mightily and was repeatedly sucked back into the base of the dam. I was very panicked at the time and for some reason, whether it was the hand of God or simply some other miracle, through no coherent thought process of my own, I suddenly quit struggling and the water just "flushed" me out of the problem area and all was well. I have always had some inkling as to what forces were at work in this experience and now have a very good understanding after reading your very informative article. Thanks for your good work on a rarely discussed problem.
I am glad you enjoyed the article and thank you for sharing your personal experience with low-head dams. Unfortunately, your story is all too common with these structures, but thankfully you were able to rescue yourself. As you discovered, it is impossible for even the strongest swimmer to swim out of the hydraulic. Many rescue personnel explain that to escape the hydraulic, you have to do what is counter-intuitive—stop fighting the hydraulic and get to the bottom of the stream where the current will push you downstream past the hydraulic.
Michael Robinson, Ph.D., P.E.
Save railroad right of ways
Thank you for publishing Mathew Phair’s article on the T-Rex transportation infrastructure expansion in Denver in the October 2006 CE News. Please note that a fundamental part of the project was the availability of the old Colorado & Southern railroad right of way. In my opinion, lightly used railroad rights of way are invaluable assets to the community and should never be completely abandoned. Even if we do not have a specific transportation or public utility plan for them, they should be protected intact for future generations. Much of the recent transit expansion in Los Angeles has been done at reasonable cost and minimal societal impact using these old rail lines. Our profession should guide these right-of-way preservation efforts and should never abet their destruction.
Michael McGinley, P.E.
Sewer horror stories
After reading recent articles about aging wastewater infrastructure [CE News, December 2006], I feel obligated to provide a rebuttal to this nonsense. The fact is that the majority of defects in wastewater collection systems are not due to the age of the systems at all. The majority of pipe failures and maintenance problems in wastewater collection systems are caused either by defects that have been present in the system from the day it was installed, or by subsequent damage or clogging caused by more recent construction, poor judgment, or objectionable activities adjacent to the existing piping.
In my various positions in this industry, I have been watching in-pipe wastewater inspection video for the past 20 years for collection systems in California and Washington. In one Western Washington city, for example, I reviewed approximately 100,000 linear feet of recent in-pipe inspection video, with almost 10,000 defects logged in the inspection reports. Very few of these 10,000 defects are due to the age of the wastewater collection system. In fact, there are many reaches of 100-year-old clay and concrete pipes that are still in good condition. In my work, I find a low correlation between pipe age and pipe condition.
Almost every problem I have ever observed in wastewater collection systems was caused by one or more of the following:
- Tunneling under the existing sewer collection piping to install subsequent utilities, then failing to provide proper compaction, or flowable fill, under the existing wastewater collection pipe.
- Installing other utilities over the top of existing sewer collection piping and crushing the existing sewer pipe by excessive compaction energy.
- Poor construction techniques during subsequent lateral connections, such as the "hammer tap" method, that results in mortar and lateral pipe ends intruding into the main sewers and partial obstruction.
- Breakage of existing wastewater collection piping followed by installation of a sleeve with flexible connectors at both ends as a "repair." Always use rigid connectors for this purpose.
- Inspectors who fail (for whatever reason) to enforce the provisions of wastewater construction contracts (for example, the low-pressure air test and in-pipe inspection video).
- Changes in pipe alignment, grade, diameter, or material at some point between manholes. We will eliminate a large number of sewer backups in this industry, and make maintenance easier, by installing manholes at all locations where any of these changes occur. Such manholes should have been installed at the time of original construction.
- Sewer rehabilitation methods that either don’t work for very long, or don’t work at all.
- Use of excessive force and water pressures in rodding and jetting pipes during cleaning, and when cutting roots with mechanical equipment.
- Failure to install properly sealed joints, which allows root intrusion.
- Hydrogen sulfide corrosion caused solely by factors that should have been known and accounted for (or eliminated) at the time of the original design, or which could have been corrected at any time since then using information that has been widely known for more than 20 years.
- Horizontal directional drilling through the existing sewer collection piping.
- Restaurants or other grease generators being allowed to connect to the collection system without full-size grease interceptors.
- Pipes laid on uneven slopes, or subsequent settlement caused by the failure to excavate and remove compressible soils under the pipe.
- Allowing debris, such as rocks, gravel, and concrete chunks, to enter the wastewater collection system during the original or subsequent construction.
- Installation of damaged or defective pipe (or pipe with defective gaskets) that should have been rejected by the inspector.
- Installation of pipe with pulled joints or rolled/intruding gaskets.
- Pipe laid with insufficient bedding material or the wrong bedding material, leaving the pipe unprotected during compaction.
- Engineers who specified the wrong type of pipe for the intended application, or a pipe too small to account for future flow rates.
- Outside drops that serve to complicate the cleaning and inspection process. The typical manhole (if properly constructed) may outlive the typical outside drop. If you need a drop, construct an inside drop bowl and pipe, where it can be properly inspected, maintained, and replaced when required.
As you can see, none of these problems is directly related to the age of the collection system, although the defects in wastewater collection systems will continue to get worse with age. I think this industry has wasted billions of dollars putting defective wastewater collection systems in the ground and then damaging them in the years following construction. This trend continues today.
The technology and techniques for constructing wastewater collection systems have improved significantly, of course. But all of the problems I mentioned above can be solved by using modern construction techniques, which are frequently ignored.
For the wastewater collection systems you are responsible for, try this experiment: The next time you review in-pipe documentation showing pipe damaged for no apparent reason, check your utility maps for utilities installed after the sewers. Then, go out in the field and look for evidence of trench patches at those locations. Every crack has a cause. Do you think it is just a coincidence that much of the damage to existing sewer pipes corresponds to asphalt patches on the surface from subsequent utility installation?
If you think the proper response to sinkholes and failing wastewater collection infrastructure is to blame the problem on old-age and buy more "asset management" software, then I believe you are heading in the wrong direction. The best infrastructure is that which requires the least management. Contractors, inspectors, engineers, and wastewater system managers don’t need more software to tell them how to do their jobs.
Although I have focused here on wastewater piping, there are similarities with wastewater manholes and stormwater collection systems as well.
During my career, I have seen numerous examples of infrastructure that cannot be properly inspected because of the lack of access. Remember this: That which cannot be inspected cannot be maintained. If you build anything that cannot be inspected, you have just guaranteed that it will never be maintained.
My message to the wastewater industry is this: It is time to stop crying about aging wastewater collection infrastructure and time to start doing your job. It is irresponsible and unprofessional to howl continuously about the age of the infrastructure when the problem rests at your own doorstep.
I would appreciate feedback from those in this industry who have a different experience.
Steve Willie, P.E.