Pit depth
To achieve point 1 above, it is normal practice to make the pit floor lower than the datum dimension and then cast into the floor levelled steel ‘sole plates’ at the required height minus 5–10 mm to allow some upward adjustment of the machine to the exact floor level. The final levelling can be done by some form of millwright’s levelling pads, or more usually levelling screws and shim plates, as shown in Fig. 18.5.
The system described above allows the pit floor to have some slight ‘fall’ towards a small drainage sump fitted with a level alarm or float operated pump. If the site has a high water table, the pit will have been suitably ‘tanked’ before final concrete casting to prevent ground water seepage; however, spillage of vehicle liquids and cell washing will drain into the pit so a means of taking these liquids into a foul liquid intercept drain is advisable.