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<br />uncontaminated ground waters. The numeric standards <br />• applicable to this classification are the EPA Interim <br />Primary Drinking Water Standards and Secondary Drinking <br />Water Standards; which are given in Table No.7. <br />The Colorado Basic Standards state that there shall be no <br />increase above naturally occurring concentrations of <br />radioactive and organic substances in ground water, i.e. the <br />discharge of these substances into ground water is <br />prohibited. The Basic Standards further state that there <br />shall be no discharge in concentrations or amounts that <br />jeopardize beneficial uses or are toxic to humans, animals, <br />plants or aquatic life. The state has not as yet established <br />effluent standards applicable to ground water, other than <br />the prohibition of organic and radioactive substances, as <br />previously mentioned. It is understood that the process to <br />promulgate standards is in motion but the timing is probably <br />several years away. With the possible er,ception of the area <br />near monitor well MW 4, (site no. 17), it appears that any <br />contamination of ground water has been confined !o that <br />underlying the pond (and seeping to surface south of the <br />pond). In this area primary drinking water standards have <br />been er.ceeded at 12 ground water sample sites and secondary <br />standards have been e>;ceeded at 8 sites. However, at four of <br />these latter sites only the manganese standard has been <br />e>:ceeded (refer to Figure Nos.2 and 14). Interestingly, the <br />• sample collected at the interceptor drain (site 21), <br />representing surface and ground water inlow to the new pond, <br />contained e:;cessive concentrations of cadmium, a primary <br />drinking water parameter. <br />The ground water adiacent to the Animas River, er.cept at <br />site 13, essentially meets state Class 1 standards for the <br />parameters sampled er.cept for manganese. The same is true <br />for the ground water at site 10, immediately south of the <br />area contaminated by seepage emanating from the old pond. <br />The groundwater in this area is a matter of particular <br />concern due to its proximity to the contaminated seepage <br />water.The B foot thick gravel strata below the old pond at <br />site 9 (well M-15) projects into site 10 (well M-17), thus <br />there is a potential for groundwater contamination at this <br />site (refer to Plate III-2). <br />The high zinc values found in wells MW 1, MW 3, P 3 and P 4 <br />(sites 15-19, inclusive) maY be the result of a plume <br />emanating from old, oxidized tailings in the vicinity of <br />site 13 (well M 20) where the zinc concentration is 62.6 <br />mg/1. However, it is more probable that the high zinc <br />concentration in these wells is due to the seepage of decant <br />water through the pond dikes and discharge from the pond <br />• -17- <br />