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Utility Layout - Separation Requirements for Various Utilities

  • 1.  Utility Layout - Separation Requirements for Various Utilities

    Posted 09-27-2017 10:25 AM
    Howdy,

    First time ever post hopefully in the right section? I am looking for a direction to find standards regarding my question.

    Project location is at a Coastal Texas Port Facility.

    Designing a proposed potable water main, as well as, a saltwater main for fire protection.  Saltwater to be pressurized from a pumping station in emergency situations then to be flushed after use.  Question I have is separation distances for these two mains, as well as, can they be buried in the same trench.  I have a stretch where they parallel and looking at options. Both lines to be constructed of PVC.  Any help would be appreciated.  If any more input is needed from me, feel free to ask.  Young engineer and have not ran into this situation before.

    Thank you!

    ------------------------------
    Scott Mason P.E., M.ASCE
    Lead Project Engineer
    G&W Engineers, Inc.
    Port Lavaca TX
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  • 2.  RE: Utility Layout - Separation Requirements for Various Utilities

    Posted 09-29-2017 05:22 PM
    ​Scott,
         In my experience, the local authority for potable water has set standards and those are the minimum if no standards are held by the facility owner or (in the case of a construction contract) the specifications.  For example, we have run into the issue of collocating effluent reuse water in the same trench as potable, and defaulted to the local utility standards.  Another source of information would be the state DOH.

          When in doubt, collocate but maintain 6' separation or encase the potable in concrete.

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    Donald Jones P.E., M.ASCE
    Kailua HI
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  • 3.  RE: Utility Layout - Separation Requirements for Various Utilities

    Posted 10-01-2017 11:42 PM
    Morning Scott,
    I've constructed multiple utilities in one trench on several projects. Sometimes the utilities are installed at different elevations but in the same trench. (Projects were built in Middle East for Oil and Gas). 

    We followed British Standards there, however I'd like to add that American Standards are no different, there's always a specification somewhere.

    All these issues were already resolved. We just need to find them.

    ------------------------------
    Kalyan Emandi C.Eng, M.ASCE
    Sr. Project Engineer
    Senegal, West Africa
    ------------------------------

    Original Message


  • 4.  RE: Utility Layout - Separation Requirements for Various Utilities

    Posted 10-01-2017 11:43 PM
    Scott:  Separation requirements are usually set by the state if one of the mains is not potable water.  In California the distance face to face between potable water, and other non sanitized water is 10 feet face to face.  You should be able to look this up online for your state in their health and safety code.  Continuing on the safety issue, you also need to consider that you need to provide a reliable water system.  This means a looped system with short dead ends and valving so a damaged main can be isolated and not impact the system at large.  A standard engine unit can only carry enough water for a fire the size of 2.5 bedrooms.  Fire hose sections typically weigh 50 lb. and each engine has a limited amount of hose.  If you have not done this, ask your local fire station if you can run a block with a section of hose.  It is good training for body and understanding why taking fire hydrants out of service needs to be taken seriously.  In some cases I have allowed two standard size distribution potable water mains in the same street to provide a looped redundant system.  Because one main must be in service at all times, the mains need to be on opposite sides of the street.  In your case, if the potable main should burst, it could undermine and damage your fire distribution system. Does your fire system have a backup system?  It sounds to me that it is served by only your salt water pump.  In this case, I recommend keeping the main on the opposite sides of the street.  A single  source of water for fire suppression in my region would be unacceptable and no insurance would cover the properties.  Without a looped system "reliable water system" our Building Code will not even allow a property owner to deliver combustibles to form a building slab.  

    OK, so what do you do if there is absolutely no other option?  According to an ASCE article many years ago, it is not recommended to concrete encase PVC as  there is a chemical reaction that damages the pipe.  I also had a contractor tell me it was impossible to restrain PVC long enough for the concrete to set.  It tends to float.  I would recommend restrained joints that are staggered and keep them as far apart as possible and not in the same trench.  After thrust blocks are set, then encase in a three sac concrete mix.  It will help stabilize the location of the pipes but field crews will be able to dig it up.  If the agency is going beyond their discomfort and allowing you to use one trench, I suggest some type of bond breaker to separate the two encasements so working on one pipe will not damage the encasement on the other.  Find out what pipe type your agency wants.  Don't fall into the trap of specifying stainless steel because you are trying to reduce risk.  Well maybe it would be OK since it will be encased. Stainless steel corrodes when buried in the ground and it is very costly.

    ------------------------------
    Barbara Salvini P.E., M.ASCE
    Owner
    Barbara A.B. Salvin
    Ramona CA
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  • 5.  RE: Utility Layout - Separation Requirements for Various Utilities

    Posted 10-02-2017 09:53 AM
    Scott,

    Check with your local Department of Health (DOH) or agency responsible for drinking water in your area. We use 10' separation horizontal and 18" vertical for sewers.  And where the distances cannot be met we require concrete encapsulation.

    We follow 10 State Standards and our DOH requirements for our specs. ​http://10statesstandards.com/waterrev2012.pd

    Good Luck,
    Jim




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    James Bednarczyk Aff.M.ASCE
    Junior Engineer
    Mohawk Valley Water Authority

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  • 6.  RE: Utility Layout - Separation Requirements for Various Utilities

    Posted 10-03-2017 12:45 PM
    Take time to peruse 43TAC§21. Here, reference was made to TCEQ, a government agency that is the OPR for water lines and spacing requirements. ( Texas Administrative Code) http://texreg.sos.state.tx.us/public/readtac$ext.ViewTAC?tac_view=5&ti=43&pt=1&ch=21&sch=C&rl=Y)



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    Justin Obinna P.E., M.ASCE
    Area Engineer,
    Texas Dept of Transportation
    Carrizo Springs TX
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    Original Message


  • 7.  RE: Utility Layout - Separation Requirements for Various Utilities

    Posted 10-03-2017 04:39 PM
    I think this is the wrong link.  This is from the Dept. of Transportation.  The specs govern crossings of highways.

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    Barbara Salvini P.E., M.ASCE
    Owner
    Barbara A.B. Salvin
    Ramona CA
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    Original Message


  • 8.  RE: Utility Layout - Separation Requirements for Various Utilities

    Posted 10-03-2017 12:45 PM
    Scott,

    The Texas Commission on Environmental Quality (TCEQ) is the governing agency that sets standards for water distribution systems.  The standard separation distances for water and wastewater is no closer than 9 ft. in all directions measured from the outside surfaces.  There are exceptions to have at minimum 4 ft. horizontal and 2 ft. vertical separation (drinking water above) if pressure rated pipe is used and other requirements are followed, See 30 TAC Rule 290.44 for more information.  I hunted around on the TCEQ website for more information on salt water lines and how they are classified, but could not find anything specific to your application as fire protection.  One thing that comes to mind is you may have to have specially labelled fire hydrants indicating non-potable water, but I am not sure.

    I suggest you go to the water section of the TCEQ website.  There is an email address for questions.  I have submitted questions before for unique situations I've encountered.  They are a bit slow but do provide comprehensive answers.

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    David Dillmann P.E., M.ASCE
    Snr Project Manager
    Atkins North America, Inc.
    Carrollton TX
    ------------------------------

    Original Message


  • 9.  RE: Utility Layout - Separation Requirements for Various Utilities

    Posted 10-05-2017 10:35 AM
    Howdy,

    Thanks everyone for the reply.  Before I posted my question I had made a phone call to TCEQ.  I am pretty familiar with their rules.  They had no rules to refer to my question.  They simply said we do not have a rule for that.  The saltwater main will be also served by the potable water system hence the flushed after use.  It will have a switching system.  Both pipes will be pressure pipes.  the potable water 8" and the saltwater main will be 12" .  I have a stretch of about 200'+/- where I need to run both of these mains, as well as, a 6" pressure pipe for storm water all within 7' of horizontal space.  This is why the question came up.  And I have a hard time classifying a saltwater fire main as sanitary sewer in terms of rules.  I could see where they would use the term "non-potable mains" instead of wastwater collection mains, but I do not remember seeing this.  The 8 and 12 will parallel for some 1/2 mile or so.  Hope this can help answer some questions yall had.

    ------------------------------
    Scott Mason P.E., M.ASCE
    Lead Project Engineer
    G&W Engineers, Inc.
    Port Lavaca TX
    ------------------------------

    Original Message


  • 10.  RE: Utility Layout - Separation Requirements for Various Utilities

    Posted 10-10-2017 03:27 PM
    In California we have very stringent cross connection standards.  We maintain separation requirements for any main that could have bacteria.  Certainly untreated water from the ocean and storm water would qualify.  About six years ago the state reduced the standard for separation between potable water and disinfected reclaimed water.  In CA, your connection between potable water and ocean water would need a backflow device (reduced pressure type) or a 12 inch air gap at a tank. You might want to look at the california standards for options where you can't maintain full separation.  There are options presented such as upgrading pipe class for PVC, etc. which may be cheaper.  If you should ever face litigation, following a standard that is well known and specific will help you represent that you were following a conservative industry standard and professional standards.

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    Barbara Salvini P.E., M.ASCE
    Owner
    Barbara A.B. Salvin
    Ramona CA
    ------------------------------

    Original Message


  • 11.  RE: Utility Layout - Separation Requirements for Various Utilities

    Posted 10-05-2017 10:36 AM
    There was an interesting study performed several years ago, commissioned by FDOT and undetaken by the University of South Florida (USF). The study was chaired by Dr. Kranc, PE; OPTIMUM PLACEMENT OF UTILITIES WITHIN FDOT R/W .

    This study took into consideration all of the separation requirements and considered both existing and "virgin" utility corridors. As I recall, Dr. Kranc and his group developed an Excel spreadsheet that would create an optimal placement matrix based upon the type, size and number of utilities being placed and also took into consideration issues such as, future access needs and maintenance.

    There is a link to this study on the FDOT website; OPTIMUM PLACEMENT OF UTILITIES WITHIN FDOT R/W


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    Gregory Jeffries B.S., M.ASCE
    Regional SUE Manager - Texas
    McKim & Creed
    Certified Utility Contractor
    UESI - Utility Risk Management Division
    Utility Investigation Committee Member
    ------------------------------

    Original Message


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