Small diameter water supply main next to a gas station 2

[KristiNZ]

Hi
I am looking at a new water supply main that is to be installed in the near future. The route that we need to take puts us next to a petrol station that has been operating for at least 30 years. It is assumed that there will be some level of hydrocarbon contamination in the soil and that this could potentially impact on the supply main.
We are wanting to use PE pipe as this is economical and will work well in a seismic event (which is paramount for us in NZ).
Does anyone have information on if there is a suitable PE product, or if there is a heat component as to when hydrocarbons leach through PE pipe?
Cheers

 

[dicksewerrat]

Drill some test wells. If the soil is contaminated, the station may be liable for clean up and extra costs for the water main. The info may also help you keep the workforce safer.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[rconner]

http://www.google.com/url?q=http://...gQFjAA&usg=AFQjCNHqAOSgnEttW7Af7Lc8C8He7b0h7A

 

[LittleInch]

Try this stuff.

http://www.gpsuk.com/range/33/protecta-line.html

Incorporates a thin metal liner to prevent leaching of petroleum products through PE which is authorised by the UK water council (I think), but it has been around for some time now. It needs to be jointed using special couplings which also incorporate this so can't be fusion welded.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[rconner]

If you are wanting to "try" polyethylene pipe for potable water service in contaminated ground, or ground that is/will be potentially contaminated, there are some things you should probably be aware of. Gasoline and/or its constituents e.g. in contact with the pipe will we absorbed inward/accumulate into the polyethylene in the pipe i.e. it will eventually "permeate" through the polyethylene material. This mechanism is incidentally not prevented by high pressure differential from the inside to the outside. Most of these constituents are either known, or suspected, as being quite bad actors as far as the health of folks using the water is concerned. You should probably also be aware that polyethylene absorption of such substances not only results in permeation, but it also causes swelling and other affects on the constituents/physical properties of the plastic pipe wall and/or sheath. In this regard notice that per the chemical resistance "Library" of a major manufacturer (I believe in your general end of the world) posted at

http://www.iplex.com.au/iplex.php?page=96&c=838,839,840,841,

polyethylene has "No Resistance" to most concentrated benzene (a major constituent of gasoline) and it appears for some reason claiming "Information Not Available" for any more dilute or weak solutions. Per the same database at

http://www.iplex.com.au/iplex.php?page=96&c=1046,1047

polyethylene has only "Limited Resistance" to generic "Gasolene - High Octane", with it appears a claim of "Information Not Available" regarding ANY concentrations to which this nebulous "Limited..." grade is specifically applicable. The categorization by this major manufacturer of "Information Not Available" is some curious, in that I think polyethylene pipe in reality has been around at least to minimal extent since about WWII! Closer to us in the USA the site at

http://www.plasticpipe.org/pdf/tr-19_thermoplastic_pipe_for_transport_of_chemical.pdf

has some seemingly reassuring words in the beginning text, but see also the not too veiled warning finally on page 3, "In general, thermoplastic pipes should not be used where a permeating chemical in the environment surrounding the pipe could compromise the purity of a fluid, such as potable water inside the pipe (See also PPI Statement N on Pipe Permeation)." Also, finally on page 24 in this section you will see a grade of "N" ("Not Resistant") for exposure of unpressurized polyethylene pipe to all listed types of gasoline (and about a hundred bolded disclaimers furthermore indicating loading/pressure/stress/strain on the pipe certainly doesn't help!).
If you are convinced that in the face of these realities, and via some wizardry e.g. with the alleged continuity and strength of a thin metal foil and special connectors etc., a "barrier" pipe system will be dependable for the life of the plastic pipe system in the real world, there may also be yet further questions regarding maintenance/repairs of inevitably some field-damaged pipe as well as future connections and future tapping, and maybe particularly once the pipes have absorbed contaminants.
Finally, perhaps a question may need to be asked is the cost of these new pipes (not to mention field labor etc.) really "economical" as you wish when other alternatives are available? Per the list prices I have noticed on page 8 at

http://www.plumbinganddrainageplastics.co.uk/SLA Brochure 09.pdf

it appears only 6m or 12m discrete pipe lengths of all sizes larger than 180mm (~7" dia) are available i.e. no longer "coils", meaning regardless of field layout it appears a lot of field "connectors" and assembly of same will be needed. The listed price per meter e.g. of 225 mm DR11 barrier pipe is £134.40/m (I calculate about 62.28 USD per foot at today's exchange rate.). This manufacturer doesn't appear to even show a price for any larger "couplers", though I noticed on page nine a DR17 and smaller 180 mm, "Fluid Hydraulic Compression" coupler is priced at £470.40 ea (I calculate about 715 USD each!) Of course all kinds of fittings and appurtenances are inevitably also required in distribution systems, and I see here the price of this same sort of "Equal Tees" in these little 180mm sizes is a whopping £1435.34/or ~2,181.72 USD EACH. Whether or not the system will work in the short and long term, it is clear this manufacturer is thus quite "proud" (with such prices, as they say down South) of same.

 

[LittleInch]

The barrier pe pipe isn't cheap, but if you only needs it for the length of the contaminated ground won't significantly affect the overall cost. You could also just put in a few lengths of steel pipe....

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[cvg]

install in a steel casing past the gas station

 

[greggy]

We have successully used a LMW (low molecular weight) hydrocarbon non-permeable pipe wrapper called PetroGard made by MPC Containment Systems on a 36-inch ductile iron diameter water main through 300 feet of BTEX-contaminated area. Find them on the net. We had to get EPA approval to use the material, but succeeded. The material is intended to contain leaking fuel in its conveying lines, so we used it to keep fuel out of our main. The EPA asked, "If it's made to keep hydrocarbons contained INSIDE the wrap, how do you know it will work to keep hydrocarbons OUT?" We answered, "We'll turn the wrapper inside out," which was the dumb answer to a dumb question.