Consult a good reference ...

Published March 19, 2015 15:36 by John Doe

Consult a good reference manual

Jasmin,

In your role you need some fundamental knowledge about well construction criteria. I suggest that you purchase a copy of Groundwater and Wells , 1986, Johnson Division. Johnson is a famous maker of well screens here in the US.

Another good reference, but harder to find, is Water-Well Design and Construction, by RL Harlan, KE Kolm, and ED Gutentag, Developments in Geotechnical Engineering, 60, Elsevier, 1989.

There are two primary aspects of well design - hydraulic design and structural design. Your current question relates to the latter condition, structural design. The general objective is that the well must not collapse under its own weight, the screen not collapse either, and the material not loose strength over the design period of the well, nominally 50 years. I have worked on wells that are functional after 100 years, but thats not usual.

It is not unusual to see PVC well casing to 500 feet. The designer needs to pick a pipe-wall thickness that has enough strength to stand up under its own weight. Screen selection has to have the same considerations of strength under compression. PVC screens are not strong, so you may be looking at a hybrid - PVC casing and a stainless steel screen. They are expensive. Don't shy away from using good materials that are more costly, remember the design life aspect. Don't rule out steel casing if the cost-life cycle analysis provest it out, but you have to consider loss of strength over time due to corrosion - as others have experienced in your area. On the flip side, the price of PVC is linked to oil - this may be the lowest pricing for PVC casing we will see for some time!

Another are not to skimp on is the hydraulic design. I don't have time to go into details here but the money spent on a high quality, high open area screen can be recouped in the first several years of operation due to decreased pumping (power) costs. Again, consult and study Groundwater and Wells and you will be well informed.

Best regards,

Greg