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• reports. The frequency column on Table 6 indicates the number of <br />exceedences out of the total number of samples (i.e., 1/2 indicates one <br />exceedence out of two samples). Below is a summary of standards that <br />were exceeded, Given in parenthesis is the source and use of each <br />standard. <br />Parameter Number of Wells <br />iron (CDOH, irrigation) 1 <br />manganese (CDOH, irrigation) 2 <br />In addition, two samples from the same well had cadmium values that were <br />less than an elevated detection limit (20 ug/1 vs. a normal detection <br />limit of 3 ug/1), which was higher than the CDOH standard of 10 ug/1. <br />Likewise, the same two samples had lead values that were less than an <br />elevated detection limit (200 ug/1 vs. a normal detection limit of 20 <br />ug/1), which was higher than the CDOH standard of 100 ug/1. The cause <br />. of these elevated detection limits was a decision by the laboratory to <br />dilute the samples prior to analyses in order to reduce the effects of <br />interferences (primarily, high salinity).. <br />Elevated levels of iron may be attributed to natural (i.e., not mining <br />related) conditions, since elevated levels for this parameter are not <br />found in the adjacent Seneca II spoil wells. The high levels of iron <br />displayed in the one alluvial well (YGAL15) may be the result of organic <br />matter and plant debris present in the alluvium (Hem, 1989, pg. 77). <br />This well displayed high levels of iron prior to mining. <br />High manganese values may, in part, be due to recharge from the spoil <br />aquifer, although high values are often common, especially in alluvial <br />material (Hem, 1989, pgs. 86-89). Both wells displaying high manganese <br />values this year also did so prior to mining. It should be noted that, <br />while the CDOH uses a standard of 0.2 mg/1, the EPA states that this <br />standard is used to protect crops grown in soils with a pH value lower <br />than 6.0. In soils with a higher pH (as are found in the Yoast region}, <br />• a more appropriate standard would be 10 mg/1 (EPA, 1976). This year, no <br />well displayed a value higher than 2.36 mg/1. <br />7 <br />