POTABLE WATER MAIN CONSTRUCTION 1

[Florida]

I HAVE TO DESIGN A WATER MAIN UNDER A ROAD THAT HAS DRAINAGE SWALES IN BOTH SIDES. THE SWALES ARE KIND OF DEEP. THE BOTTOM OF THE SWALE IS ABOUT 5 FEET BELLOW THE ROAD CENTERLINE ELEVATION. SHOULD I DESIGN THE WATER MAIN STRAIGHT FROM THE BOTTOM TO THE BOTTOM OF THE DITCHES OR SHOULD I GO ALONG WITH THE TERRAIN PROFILE. IF I GO STRAIGHT FROM BOTTOM TO BOTTOM THE WATER MAIN WILL BE CONSTRUCTED 7 FEET BELLOW THE ROAD GRADE, OTHERWISE I COULD KEEP THE STARDARD 3-FOOT BELLOW THE GRADE ELEVATION. THE WATER TABLE ELEVATION IS ON THE BOTTOM OF THE SWALE AND THE SOIL IS WELL DRAINED SAND. I AM NOT SURE IF ALL FITTINGS THAT I WILL SAVE CONSTRUCTING THE WATER MAIN STRAIGHT WILL COMPENSATE FOR THE DEEPER TRENCH THAT I WILL HAVE TO DIG AND MANAGE DURING THE WORK.... THE TOTAL LENGTH OF THE CROSSING IS +- 140 FEET.<br>I APPRECIATE ANY COMMENT OR ADVISE. THANKS

 

[mikolay]

You do not want to make a high point in the profile of the pipeline under the road as this is where air will tend to accumulate.&nbsp;&nbsp;Any air will be hard to push/pull out of the main.&nbsp;&nbsp;Design your main to be on a steady grade from ditch through ditch.&nbsp;&nbsp;Locate any high points in the main profile out of the road where you can locate a hydrant.

 

[Florida]

Mykolai answer makes a lot sense to me and I appreciate his help. I just would like to clarify one more thing in the same problem. The span of the water main under the road is a steady grade for approximately 35 feet (from road shoulder to road shoulder).. Can I just install an air rel. valve in one side of the road to avoid the air to accumulate??? If you think this solution is acceptable... Do I need to install more air valves in this &quot;W&quot; shape water main profile (in the other two high points)??? And the last question.. If I decide to go straight from ditch to ditch ..... Do I need to install any air rel. valve in the high points?<br>I really appreciate your advice... Thanks <br>

 

[mikolay]

Again, I suggest avoiding high and low points in the profile, do not use a &quot;W&quot; shaped profile.&nbsp;&nbsp;Lay one steady grade across the road and ditches, even if this means digging deeper in places or place insulation over the shallow main, although you probably don't have that requirement in Florida.&nbsp;&nbsp;Use one air release valve at the end of the line.

 

I agree with mikolay whenever possible.&nbsp;&nbsp;There are situations when using bends or offsets are unavoidable.&nbsp;&nbsp;How long is the main?&nbsp;&nbsp;How much cover is required over the water main?&nbsp;&nbsp;If you install the main 7' deep, do you come back up to a higher elevation with the rest of the main?&nbsp;&nbsp;I just finished a project where I crossed a state road.&nbsp;&nbsp;In 80' of 12

 

[bballfan]

I posted above, but the entire post did not show up.&nbsp;&nbsp;I joined today and my ID is bballfan.<br><br>I agree with mikolay whenever possible.&nbsp;&nbsp;There are situations when using bends or offsets are unavoidable.&nbsp;&nbsp;How long is the main?&nbsp;&nbsp;How much cover is required over the water main?&nbsp;&nbsp;If you install the main 7' deep, do you come back up to a higher elevation with the rest of the main?&nbsp;&nbsp;I just finished a project where I crossed a state road.&nbsp;&nbsp;In 80' of 12&quot; watermain, we had 5 conflicts.&nbsp;&nbsp;Fiber optic and elect. and communication banks, a 48&quot; storm drain and a 96&quot; raw water main.&nbsp;&nbsp;At our tie in point to the existing water main we had 4 feet of cover.&nbsp;&nbsp;When we finally got pass all the conflicts we got back on grade, 4' from top of pipe to finish elevation grade.&nbsp;&nbsp;We used 45' bends and offsets to accomplish this installation rodded and thrustblocks.&nbsp;&nbsp;I installed ARV's at every high point.&nbsp;&nbsp;This profile looked unbelieveable.&nbsp;&nbsp;Remember, trapped air in the main makes holding a steady required psi for testing very difficult.&nbsp;&nbsp;Good luck