18" Watermain dead end 3

[skairi]

I am been working on a multi-million roadway project and during the water main installation the constrution was changed from 2 phases to 3 phases due to MOT issues. But in the 2nd phase the water main have 400 ft of dead end which was approved by the by the authorities. But i got the situation now that the authorities want this line to be flushed periodically which is the change in the scope of work. Every week the authorities checking the Chlorine level which is above 0.2ppm and per them the actual main have 1.0ppm.
My question is how much Chlorine level should be maintained to keep the quality of water? Or is there the possibility that if we shut down the dead end and in the next phase we can do the Bac-T test and go from there?

 

[bpattengale]

Are there any branches or services off of the 18" main on the 400'? If not just shut the closest gate valve and drain the line. During phase 2 just redisinfect the line after the line is completed.

The 10 States Standards for Waterworks recommends a minimum free chlorine residual of 0.2 mg/L (0.2ppm) in the distribution system, so as far as that is concerned it sounds like you're meeting it but eventually the water is going to stagnate in the 400' of line if there isn't any flow.

If the authorities are really concerned about the line, install a temp fire hydrant at the end of the line. A flow rate of about 2000 gpm out of the hydrant should provide the recommended flushing velocity of 2.5 fps in the 18" main.

 

[bimr]

Has the water line been turned over to the owner? If so, then the owner would be responsible for the flushing. If the water line has not been turned over to the owner, maybe the turnover can be expedited so that the flushing is no longer the concern of the Contractor.

One would doubt that the owner would be enthused with having a third party flush his system. If flushing is necessary, it may be more appropriate to install an automatic flush system, not a high flow hydrant flush that may possibly damage the water system.

https://my.sfwmd.gov/portal/page/portal/common/pdf/splash/spl_alf_devices.pdf

http://www.hydrants.com/index.php?p...facturer_id=0&option=com_virtuemart&Itemid=30