Water monitoring wells comprise standpipes / monitoring wells typically installed using hand held percussion window sampling, mini tracked rigs or larger cable percussion drilling. The installation usually consists of 50mm HDPE plastic plain pipe (for the top 1-2 metres) and then a perforated 50mm HDPE pipe (normally 1-2 mm slotted) to the base of the hole, to allow for monitoring of water and/or Gas wells. The borehole is back filled with washed sand/gravel which is used as filler between the pipe and strata. A Bentonite plug may also be used. A cover or bung with gas tap can be fitted to allow for regular samples to be taken. The well installation is usually finished at ground level with either a lockable protective flush (traffic rated) or a raised (0.5 metre high) metal cover.