pipe trench in gypsum 2

[Sully03]

We currently working on a land development project were the trench for the sanitary and storm will be located in gypsum.

What precautions should be taken to avoid undermining of the pipe? during construction and after.

thanks
cory

 

[BigInch]

Before placing bedding material and backfill, line the trench with geotextile. That should minimize the potential for washout of the loosest material. At areas of steep grade changes along the pipeline profile, I place sand/cement bag barriers in and perpendicular to the length of the trench. The hights and intervals of each barrier should be sufficient to create a stair-step pattern (going uphill), with the rise of one barrier's height reaching 150 mm or so above the base elevation of the next barrier.

After the trench is backfilled, if at all possible, construct 150mm to 200 mm chevrons across the right-of-way to remove any rainwater from the RoW as quickly as possible in order to avoid any possibility of it saturating the backfill in the trench. If chevrons are not practical, consider other methods of runoff diversion, such as construction of small channels at regular intervals, water overshoots when ravines cross perpendicular to the RoW, construction of timber water breaks entering the RoW, etc. When in doubt about what to do, go look at the nearest railroad to see how they've been handling it for the last 100 years. Lots of experience to be had for only the price of observation there.

http://virtualpipeline.spaces.msn.com

 

[RWF7437]

Also, be aware that Gypsum is probably very corrosive ( I believe) so if you have metallic pipe, especially ferrous materials, special protection may be required.

good luck

 

[Krite]

Gypsum - Calcium Sulphate will attack concrete as well.