i did one in the late 70s for a hgv company ,dug the pit , put approx 6 inches of pea gravel in the bottom ,then put a steel liner in there with a 6 inch square cut out in the corner with a removable lid for a pump just in case it there was underlaying water if the water table rises in stormy condition ,(different ground conditions control this ),,then we bricked up the sides and ends ,,in the small cavety we left between the brick work and the steel lining we were able to run cables for lights and sockets ,
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