TESTS OF DRAINAGE PUMPING PLANTS. 
43 
The test showed an average efficiency at 6-foot lift of 50.55 per 
cent. At a lift of 6.32 feet and while pumping more than 76,000 
gallons per minute the guaranteed efficiency of 52^ per cent was 
attained. 
TESTS OF 12-FOOT WOOD SCREW PUMP, NEW ORLEANS DRAINAGE SYSTEM. 
The drainage of New Orleans and the sanitary sewers are separate 
systems. The area drained amounts to 25,000 acres, or a little more 
than 39 square miles. The capacity of pumping plants for drainage 
will eventually be equal to 7.33 inches of run-off removed in 24 hours. 
The pumping units include eleven 12-foot screw pumps. (See fig. 4.) 
Tests were made of one of the 12-foot Wood screw pumps at New 
Orleans pumping plant No. 1, on November 17, 1916, and January 
Fig. 4.— Section through 12-foot screw pump, New Orleans drainage pumping plant. 
17, 1917. In the test of November 17 the flume was divided into 10 
equal areas. As the bottom was V-shaped the width of these sections 
was greatest at the sides of the flume and least near the middle. 
Velocities were observed at 0.2, 0.6, and 0.8 depth in each area, and 
the mean velocity for an area was taken to be the mean of the three 
velocities observed. The sum of the 10 separate areas multiplied 
each by its mean velocity gave the total discharge and this divided by 
the total area gave the mean velocity. 
In the test on January 17, 1917, observations were taken of velocity 
at the same sections as in the previous test but at one-sixth, five- 
tenths, and five-sixths depth. The mean of three readings was used 
as the mean velocity of the vertical section, and the total discharge 
was obtained by summing up the discharges of the separate sections. 
Table 37 gives the results of the tests. 
