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Vitrified Clay Pipe - Modern Use in Sewers

  • 1.  Vitrified Clay Pipe - Modern Use in Sewers

    Posted 04-02-2019 06:30 PM

    Hi,

    I'm trying to gauge what are utilities using for their gravity sewer systems.  How often is Vitrified Clay Pipe (VCP) still used?  Has any utilities revised old standards to adopt modern materials, such as HDPE? Are other materials considered as a standard?  I'm most interested in cities located in seismically active areas.

    Thanks in advance for your feedback.



    ------------------------------
    Michael Tran P.E., M.ASCE
    San Francisco Public Utilities Commission
    San Francisco CA
    (415)695-7372
    ------------------------------


  • 2.  RE: Vitrified Clay Pipe - Modern Use in Sewers

    Posted 04-03-2019 09:54 PM
    Dear Michael Tran:

    The use of VCP, PE Concrete pipe or Fiberglas or another kind of pipes in sewers depends on the market price and the availability in the local market. Generally,  you start your design with one economic study considering the unitary prices of the pipes including transportation, and installation. Finally, you choose the most convenient for the project. Don´t forget to consider the soil where you will install the pipe and the chemical characteristics of water that will be transported by the pipe.


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    Alvaro Villamizar-C P.E.,M.ASCE
    Port Coquitlam BC
    1778 8000194
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  • 3.  RE: Vitrified Clay Pipe - Modern Use in Sewers

    Posted 04-05-2019 09:39 AM
    Most cities throughout the western US allow the use of PVC pipe for sewer installation.  The Cities of Lincoln and Roseville, CA, just north of Sacramento still require VCP pipe for all sewer installations.  There is a Gladding McBean factory located in Lincoln and I believe they did a heavy sales job on both Cities many years ago to get them to require VCP for all of their facilities.  While there are pros and cons with both materials, the ease of installation, availability, maintenance and performance of PVC pipe makes it a better material than VCP for most standard applications in my opinion.

    I haven't seen HDPE used much for sewer.  But the City of Sacramento may have a large diameter HDPE pipe in it's list of approved materials.  I can't remember, it's been a few years.

    ------------------------------
    Thomas Coppin P.E.,M.ASCE
    Kimley Horn & Assocs Inc
    Frisco TX
    (972) 731-3814
    ------------------------------



  • 4.  RE: Vitrified Clay Pipe - Modern Use in Sewers

    Posted 04-08-2019 12:12 PM
    Hi Michael,

    Vitrified Clay Pipe is currently used by 7 of the 10 largest cities in the United States for gravity sanitary sewer piping. After 6,000-years as the worldwide sewer material of choice and 200 years' experience in U.S. sanitary sewers, municipalities are discovering (and returning to use) clay pipe again. When municipalities inspect their sewers, they find clay pipe that is over 100-years old that is still functioning as designed and still has many years of service life remaining. Other "modern" pipe materials, installed in the last 30 – 50 years are failing. I would say longevity and maintenance are the biggest factors in the return and continued use of VCP:

    1. Sustainability and Longevity: The natural properties of VCP make it uniquely suited to the high-sulfur, highly-abrasive and highly-demanding environment of a sanitary sewer. As a kiln-fired ceramic, VCP is naturally inert. It does not change over time, so VCP offers the longest life of any pipe material.

    2. Maintenance: Aggressive cleaning has been proven to reduce sanitary sewer overflows (SSO's). No other sanitary sewer pipe material can withstand the aggressive cleaning techniques commonly used in VCP. Unmatched abrasion resistance, a Mohs hardness of 9, average compressive strength of 18,000 lbs., all result in a pipe that can withstand jetting pressures of 5,000+ psi, flow rates of 80 GPM all while using any desired jetting angle. Maintenance departments around the country have become proponents of VCP.

    3.  Resiliency: VCP like RCP are rigid type conduits and will not suffer deflection from an event. Rigid pipe differ from flexible conduits as they don't rely on soil side support to resist deflection which can be lost after a seismic event. Rigid pipe with the typical shorter lengths and factory applied flexible compression joints can move through the ground similar to a bicycle chain and remain round. Many rigid pipe users have undergone seismic activity and continue to use rigid conduits for these reasons.

    Let me know if you need more information.


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    Spiridon Lazaris P.E.,M.ASCE, MPA, mASCE, ENV-SP
    Spiros Lazaris Engineered Solutions LLC
    [email protected]

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  • 5.  RE: Vitrified Clay Pipe - Modern Use in Sewers

    Posted 04-09-2019 12:17 PM
    I agree with Hans. In my opinion, the best strategy is to open the spec to many materials meeting your spec requirements. A closed spec is what the manufacturers are looking for. It essentially gives them a monopoly on the project/municipality. Why would an engineer want to box themselves in that way? Performance specs will help the owner get what they are looking for at the best price, consider backfill, cracks, joint integrity, and deflection. Some contractors are experts at installing VCP, others at RCP, HDPE, etc. They can all compete for the low bid.

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    Matthew Mace,P.E.,M.ASCE
    Shaker Heights OH
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  • 6.  RE: Vitrified Clay Pipe - Modern Use in Sewers

    Posted 05-16-2019 03:14 PM
    I see many folks have replied. I heard there are sewer agencies in the Pacific Northwest that are considering bringing back the use of VCP as a green sustainable practice. I don't know if the groups thinking of it are talking to their seismic risk groups. As a water provider, I don't like the sewers using them because they are fragile, not water tight and can contaminate the trenches we use.

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    Teresa Elliott M.ASCE
    Chief Engineer, Portland Water Bureau
    Portland OR
    (503) 708-5839
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  • 7.  RE: Vitrified Clay Pipe - Modern Use in Sewers

    Posted 05-17-2019 12:24 PM
    Michael,
    I've had a chance to read all these great response to your questions and I don't have very much to add to this conversation.
    Anyway, I've been blessed enough to work in many different places around the world and have had the opportunity to work with many different types of pipe materials (VCP, ACP, Concrete (non reinforced, RCP, PCCP), PVC, DIP, Fiberglass, HDPE, etc.).  And as you are aware if one designs, installs, operates, and maintains the gravity sewer systems properly (using any of those materials)​.  In the case of VCP a lot of the municipalities that I have worked with generally have issues with VCP and in my opinion I don't necessarily believe its the VCP, our designs and installation practices have improved over time.  Many of the failures of VCP have been due to the practices of the those days, for example we now look at the bedding and backfill much differently than before (I'm sure 20 to 30 years from now someone is going to think the things we did today belong in the dark ages as new technologies and advancements happen).  All this being said there is a lot of VCP out there today that is still in very good shape and going strong.  Again in many of those municipalities they replace (or rehabilitee) their VCP an issue arises.  However, when they replace it, it tends to be another type of pipe material altogether. One of the reasons behind this is because they can reduce the number of joints between manholes (laying lengths for VCP can be shorter than PVC, DIP, Fiberglass, etc.) and thus reduce risk of joint failure.
    As for your seismic question it's been a while since I've worked in an area like yours but I do know that the National Clay Pipe Institute publishes 100 years and older sewer table and I believe that they state that San Francisco has had a VCP in operation since 1876, one may wish to do a little research on that line and see how it's doing, just a thought.  There are others on that list as well that one may wish to do some research on.
    Well I've taken up enough of your time.
    Have a great day and good luck!
    Doug

    ------------------------------
    C Douglas Jenkins, PE., M.ASCE
    Director - Water Networks
    Ramboll
    Atlanta, GA
    770.781.1720
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  • 8.  RE: Vitrified Clay Pipe - Modern Use in Sewers

    Posted 05-30-2019 05:21 PM
    VCP is used exclusively for small diameter sanitary sewers in Phoenix. Older VCP has issues with the joint materials, but this has been resolved in the 1970's with the rubber gasket joints. VCP, unlike PVC, is a rigid pipe material.

    I have completed an assessment of more than 2 million feet of VCP in Phoenix.  All, or almost all, of defects identified were during the backfilling of the pipe, or due to an outside influence including a gas line bored through the pipe, or damage from excavation of another utility.  In Phoenix, the groundwater table does not affect the pipe.

    For PVC pipe, I have seen issues with the pipe getting out of round due to incorrect backfilling procedures, as it is a flexible pipe.

    Other pipe materials, especially for larger pipes, include Fiberglass (HOBAS or Flowtite). Fiberglass pipe is also a flexible pipe material.  Reinforced concrete pipe with T-Lock liner (PVC) or a HDPE liner have also been used for recent larger diameter sewers. Old sewers which have deterioration due to H2S gas damage include non-reinforced concrete pipe.

    It is important that the trench is designed and backfilled to meet the pipe used.

    ------------------------------
    John Malone P.E.,M.ASCE
    Senior Project Manager
    Garver Engineering
    Phoenix AZ
    (480) 646-5374
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  • 9.  RE: Vitrified Clay Pipe - Modern Use in Sewers

    Posted 04-04-2019 10:08 AM
    Hi Michael,

    I design sewer systems in NH, MA and CT and have personally never seen or even heard of installing new VCP, though that's not to say that it isn't being done in NE.  Far and away the most common material that I see being installed is PVC (SDR 35) when sufficient cover is provided.  The next most common material I tend to see is ductile iron with Protecto-lined interior especially when there is insufficient cover under traffic loading or very deep cuts (>20 ft).  I also see PVC (SDR 26 or thicker) for very deep installs.  As far as HDPE goes I only tend to see it for stormwater applications.  I understand that some areas have approved the use of certain types of polypropylene pipe such as the Sani-tite by ADS, or similar, though I haven't personally used it.  I'm not in a seismically active area, but I hope that helps.

    Jose Lovell, P.E., M.ASCE
    Manchester, NH

    ------------------------------
    Jose Lovell P.E.,EIT
    Kleinfelder / SEA Consultants
    Manchester NH
    (603) 289-8777
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  • 10.  RE: Vitrified Clay Pipe - Modern Use in Sewers

    Posted 04-05-2019 09:08 AM
    The Cloaca Maxima in Rome is still functioning after 2500 years. However, VCP are heavy, fragile, and require skilled installation and inspection.

    Today I see almost entirely PVC pipe for the smaller sizes and concrete pipe with internal lining for the large transmission mains.
    As for anything else, I have favored including all materials allowed by the Owner in the Specifications and let the contractor decide which is the most economical to use in the local market.

    ------------------------------
    Hans H. Coucheron-Aamot
    [Retired]
    Albuquerque NM
    (505) 897-2554
    ------------------------------



  • 11.  RE: Vitrified Clay Pipe - Modern Use in Sewers

    Posted 04-09-2019 01:19 PM

    Hi everyone,

    Thanks so much for your responses and feedback.

    We are considering to open the standard specifications to other materials.  As a slight background, our standard specifications are several decades old.  It allows for nearly exclusive use of Vitrified Clay Pipe and RCP for larger diameters.  Although VCP has great properties as mentioned by Spiridon Lazaris, we are witnessing poor installation practices, inadequate quality assurance measures, potential brittle behavior of VCP under significant ground movement (differential settlement, seismic events, construction loading, etc.), pervious nature of clay (inflow / infiltration), poor joint quality.

    I was on site the other day and to my surprise, a piece of VCP fitting shattered when dropped from no more than 2' in the air onto pavement shattered.  Would there be concerns of microfractures that are not identifiable during CCTV visual inspections?

    Best,



    ------------------------------
    Michael Tran P.E., M.ASCE
    San Francisco Public Utilities Commission
    San Francisco CA
    (415)695-7372
    ------------------------------



  • 12.  RE: Vitrified Clay Pipe - Modern Use in Sewers

    Posted 04-09-2019 04:54 PM
    Seems to me you need to straighten out your construction inspection practices regardless of the materials used.
    VCP is not to be dropped from any height. The old fashioned way to check for cracks is to tap a piece lightly with a hammer and listen to the sound. If it rings clear like a bell, the piece is sound; if it rings flat, it has a crack.

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    Hans H. Coucheron-Aamot
    [Retired]
    Albuquerque NM
    (505) 897-2554
    ------------------------------



  • 13.  RE: Vitrified Clay Pipe - Modern Use in Sewers

    Posted 05-11-2019 02:20 PM
    Michael - We generally specify the best material for the application location.  We have sewer lines that run through contaminated soils, have minimal cover with heavy truck or rail traffic, poor subsoil conditions with high I&I, and some that carry industrial discharge.  We use VCP, ductile iron, RCP and HDPE depending on the site conditions and what is being carried in the pipe.  Generally we find proper quality control during installation is a big factor in having the sewer achieve its expected design life.  In the past several years we've updated our installation specs to emphasize quality control and we have added post installation testing and inspection before the work is accepted.

    ------------------------------
    Steven Brown A.M.ASCE
    Project Manager
    City of Dubuque Engineering Dept
    Dubuque IA
    (563) 589-4272
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  • 14.  RE: Vitrified Clay Pipe - Modern Use in Sewers

    Posted 05-10-2019 10:57 AM
    Just wanted to bring this back up and see if there's any additional feedback.  Thanks!

    ------------------------------
    Michael Tran P.E., M.ASCE
    San Francisco Public Utilities Commission
    San Francisco CA
    (415)695-7372
    ------------------------------



  • 15.  RE: Vitrified Clay Pipe - Modern Use in Sewers

    Posted 05-16-2019 06:44 PM
    Vitrified clay pipe made 50 years ago used gasket joints that easily met the leakage tests specified for sanitary sewer pipes. VCP is fragile in transport and above ground handling, but once properly installed in trenches no more so than any other pipe.

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    Hans H. Coucheron-Aamot
    Retired
    Albuquerque NM
    (505) 897-2554
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  • 16.  RE: Vitrified Clay Pipe - Modern Use in Sewers

    Posted 05-17-2019 08:01 AM
    At that, the fragility of VCP  and requiring skilled handling, mostly applies to the larger sizes. For the most common sizes, 8 -12", common sense will do.

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    Hans H. Coucheron-Aamot
    [Retired]
    Albuquerque NM
    (505) 897-2554
    ------------------------------



  • 17.  RE: Vitrified Clay Pipe - Modern Use in Sewers

    Posted 05-29-2019 02:52 PM

    Michael-

    As others here have mentioned, proper installation is a key element to the performance and ultimate service life of any pipe material; proper material handling on site is a minimum expectation for all pipe materials.

    VCP is unforgiving at the time of acceptance; an installation error is found immediately upon backfill load. This is considered, by many, to be a benefit to the owner. Most other materials are forgiving at a 30-day acceptance test; a benefit to the installation contractor.

    In many of our "new" VCP municipalities, I have seen the benefits of placing requirements for training and certification on "new to VCP" contractors and inspectors within each project specification, provisions, or contract. Typical project training programs are 1 to 2-hours in duration and address all aspects of pipe installation and acceptance testing. This training occurs before the project begins and all parties need to be present together; from pipe layers to the superintendents on the contractor side, as well as the inspection team, designers and the owner.

    We have developed a well-received training program as well as an installation manual based upon years of experience and research; these are offered at no charge! If you are interested in seeing one of our training programs, or if you're willing to discuss any other concerns, please give me a call.



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    Jeffrey Boschert P.E.,M.ASCE
    President - National Clay Pipe Institute
    Chesterfield MO
    314-229-3789
    www.ncpi.org
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  • 18.  RE: Vitrified Clay Pipe - Modern Use in Sewers

    Posted 06-09-2019 11:02 AM
    I have been wanting to add that, though I don't know of anyone having looked into it, I suspect that in the old times with just simple tongue and bell joints, the joints would very soon seal up tight with the grits and fats in the sewage, and groundwater pollution contributed from VCP sewers, if any, would be insignificant compared to that from other sources.

    Today, of course, VCP sewers must meet the same requirements for air tests as any other pipe materials, and do.

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    Hans H. Coucheron-Aamot
    [Retired]
    Albuquerque NM
    (505) 897-2554
    ------------------------------