96 



mid-length of the tank. The cradle, in the center of the tank, was 

 then secured by ropes to large U-bolts on return-flow pipes that 

 terminated at this location, (Figure V-6) . It was not clear whether 

 the outflow of the pipes during testing would influence the DPG. 



The instrument, carried upon the shoulder of one deck-hand, 

 was then positioned on a trestle over the tank and lowered into the 

 water by another rope slung through an arm on the trestle. Care was 

 taken to keep the instrument arms away from the trestle and tank 

 walls using two lateral control lines that were held on each side of 

 the tank. The instrument was received by a diver, guided and 

 positioned into the cradle, and secured with cable ties. The 

 orientation of the instrument was checked by measuring the distance 

 from the wall to each of the cradle legs with a tape secured along a 

 wooden "T," The top of the "T" was held against the wall to ensure 

 that the measurement was taken perpendicular to the wall. A 100 foot 

 length of unarmored cable, earlier mated to the instrument above 

 water, was interfaced with a power supply and strip chart recorder in 

 a trailer alongside the tank. Despite the poor underwater 

 visibility, (less than six inches), the entire installation took less 

 than two hours and required only two divers and one deck-hand. 



To remove the equipment, the procedure was reversed. The 

 cradle was lifted from the water by securing a rope between it and a 

 van, then the van was driven away and the cradle hoisted up along the 

 wall. 



