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SOP <br />Revision 6 <br />1/8/1988 <br />' Page 7 of 13 <br />being sampled before filling. <br />After completion of any preliminary field testing, returned to the <br />laboratory as soon as possible for analysis or preservation as required. <br />Samples that are not returned to the laboratory within an hour of sampling <br />are to be placed on ice at the time sample is taken. <br />From flowing streams, the water sample should be taken where the water <br />is well mixed, and well downstream of the confluence of a tributary stream. <br />Whenever possible, the sample is taken at the middle of the stream at mid - <br />depth. If equipment is available, an intergrated sample from top to bottom <br />' <br />taken at the center of the stream will be more representative. Samples <br />should not be taken at weirs but may be taken just below a point of <br />turbulence. Avoid floating or suspended materials. <br />From still ponds, the sample is to be taken at a point where the water <br />is representative of the main body of the pond. This point is sufficiently <br />removed from any incoming streams and at a depth that will minimize <br />localized concentrations. If necessary, multiple samples are taken and <br />combined to obtain a representative sample. <br />2.2.2 composite Samples <br />' The composite sample is prepared by combining a number of individual <br />I <br />samples that are taken at frequent intervals. The manner in which <br />omP <br />c osite samples are prepared is either prescribed or determined by mutual <br />� <br />agreement. <br />Samples requiring the addition of preservatives should either have the <br />' preservative added to each aliquot as taken or be collected in compositing <br />container which contains the prescribed amount of preservative. <br />m <br />1J, <br />