2 attach grout supply and pump a measured amount of grout to cut off potential preferred drainage path above the test drain length 3 allow time for grout reaction to go to completion and for water level to stabilize to equilibrium conditions 4 after equilibrium is achieved measure equilibrium water level by inserting a water level probe down the water supply pipe 5 apply pressure to the pinch valve to shut off flow to the section of pv drain 6 purge air from lines by pumping water down the purge tube until no air bubbles are seen coming from the water supply pipe 8 connect the water supply pipe to a constant head water source with metering capability 9 release air from the pinch valve to start flow of water into the pv drain this is time zero for the test a description of a rudimentary field test along with an example of the appropriate calculations is given by welker a l devine b j goughnour r r and foster j u201c measurement of in situ hydraulic conductivity and coefficient of consolidation using prefabricated vertical drains u201d proceedings of the 83 rd annual meeting of the transportation research board washington d c jan 11 15 2004.