a: 



X 



Calibration Results 



From a series of calibration tests 

 performed in the laboratory in the manner 

 described, a series of plots of resistance 

 readings were prepared in figure 6 (see 

 page 11). These were made for four 5-minute 

 intervals at varying rates of velocity. The 

 plots reveal that rate of dilution is linear. 

 If dilution is such that the resistance 

 value in the standpipe approaches that of 

 the diluent, however, the plot then obvi- 

 ously will leyel off. Preparation of such 

 a graph is recommended for determining the 

 number of 5-minute tests that will accu - 

 rately represent dilution rate and velocity 

 before the resistance of the solution in 



1.6 

 1.5 

 1.4 



1.3 

 1.2 

 I.I 



J. 0.9 



io.8 



> 0.7 h 



»- 

 z 0.6 



q: 



2 0.5 



< 



0.4 



0.3 



0.2 



0.1 







3 4 5 6 7 8 



DISPLACEMENT UNITS 



Figure 7. --Relation established in the laboratory between 

 displacement on the X axis and apparent velocity 

 of the Y axis derived as explained in the text. 



the standpipe approaches the resistance of 

 the diluent . 



Table 4 and figure 7 present the com- 

 parisons of apparent velocity and displace- 

 ment made in the laboratory using the 

 procedure outlined in steps 1 to 10. It 

 will be noticed that the points were estab- 

 lished with Several mixtures of materials 

 yielding a variety of permeabilities and 

 porosities. The value of permeability, K, 

 was solved for as the unknown factor in 

 Darcy's formula K = ir . The three other 

 components of his formula were measured 

 directly from the test flume. The porosity 

 factor was determined by the displacement 

 method; i.e.,. a given volume of material 



displaces a measurable volume 

 of water. The standard volume 

 of water in the standpipes in 

 these tests (step 4) was taken 

 to be 5 cubic inches. Using 

 the method of least squares, 

 we obtained the straight line 

 Y = 0.0600 + 0.1634X (figure 7), 

 where Y is the apparent velo- 

 city in ft./hr. and X is the 

 dilution units. 



OPERATION OF THE MILL CREEK 

 STANDPIPE IN THE FIELD 



A3 mentioned before, the 

 method for using the Mill Creek 

 standpipe is to dig a hole in 

 the streaimbed, place the pipe 

 in it , aijd refill the hole with 

 gravel. For obvious reasons, 

 this method precludes immediate 

 Sampling of conditions in the 

 streambed. However, the plan 

 calls for prolonged occupancy 

 in the gravel of the streambed 

 as during the entire incubation 

 period of the salmon eggs. For 

 this reason the standpipe is in 

 two pieces. When the standpipe 

 is not in use, the main shaft 

 protrudes only slightly above 

 the gravel, the cap is screwed 

 on and the sleeve is turned to 

 the closed position. It is 

 then moderately safe from drift- 

 ing objects, from the occasional 

 force of water moving at high 

 velocities, and does not become 

 filled with silt. In operation, 

 the cap is removed and the 



10 II 



13 



