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moves the mean down but since zero is also used when calculating wasteload allocations, <br /> this method is not unfair to dischargers. <br /> Metals present in water samples may be tied up in suspended solids when the water is <br /> present in the stream. In this form they are not"available"to fish and may not be <br /> detrimental to aquatic life. Because the data of record does not distinguish as to <br /> availability, some deviation from table values, and the use of x+ s, is further justified <br /> because it is unlikely that the total value in all samples analyzed is in available form. <br /> A number of different statistical methodologies could have been used where ambient <br /> water quality data dictates the standards. All of them have both advantages and <br /> disadvantages. It is recognized that the x+ s methodology also has weaknesses, in that <br /> the standard may not reflect natural conditions in a stream 100 per cent of the time, even <br /> though the use of x+ s already allows for some seasonal variability. However, the use of <br /> this methodology is justified since it provides a meaningful index of stream quality for <br /> setting stream standards. <br /> Since the x+ s methodology is an index of existing conditions and is not a classical <br /> statistical description, use of a methodology which eliminates outlyers, i.e. unusually <br /> high or low data which may be in error, is acceptable in approximating an average <br /> condition. The practice of eliminating only extremely high recorded data points and not <br /> low recorded values may result in erring on the side of safety. High recorded values may <br /> be due to sampling, laboratory, or recording error. To a limited degree the high values <br /> may be due to seasonal variation in the data base. <br /> Finally, the fairness and consistency of the use of any methodology in setting standards <br /> must recognize the manner in which the standards are implemented and enforced. It is <br /> essential that there be consistency between standard setting and the manner in which <br /> attainment or non-attainment of the standards is established based on future stream <br /> monitoring data. In addition the Division must take this methodology into account in <br /> writing and enforcing discharge permits. <br /> 9. No water quality standards are set below detectable limits for any parameter, although <br /> certain parameters may not be detectable at the limit of the standards using routine <br /> methodology. However, it must be noted that stream monitoring, as opposed to effluent <br /> monitoring, is generally not the responsibility of the dischargers but of the State. <br /> Furthermore, the purpose of the standards is to protect the classified uses and some <br /> inconvenience and expense as to monitoring is therefore justifiable. <br /> Section 3.1.15(5) of the Basic Regulations states that"dischargers will not be required to <br /> regularly monitor for any parameters that are not identified by the Division as being of <br /> concern". Generally, there is no requirement for monitoring unless a parameter is in the <br /> effluent guidelines for the relevant industry, or is deemed to be a problem as to a specific <br /> discharge. <br /> Some of the data developed by AMAX for metals values were based on "direct <br /> aspiration"testing method. This testing method has a detection limit 100 times higher <br /> than the furnace method used by the Division. In using"direct aspiration", detection <br /> limit is above some of the proposed metal values. Therefore, the Commission chose to <br /> disregard this data. Because water quality standards are set at levels of ten times below <br /> detection limits of the direct aspiration testing method, it is appropriate to use data based <br /> upon detection limits of the Health Department Laboratory. These detection limits for <br /> 12 <br />