[' ', ' ', 'Page', '10', 'The', 'IWC', 'is', 'calculated', 'as', 'follows:', 'Qe', 'IWCt', '=', '-------', '(100)', 'Qe+0Os', 'Acute', 'WLA', '(WLAa)', '|', 'In', 'order', 'to', 'ensure', 'that', 'the', 'acute', 'standard', 'is', 'met', 'within', 'a', 'short.', 'distance', 'from', 'the', 'outfall', 'during', 'critical', 'conditions,', 'and', 'that', 'lethality', 'is', 'prevented', 'in', 'the', 'allocated', 'impact', 'zone,', 'the', 'establishment', 'of', 'the', 'acute', 'WLA', 'must', 'reflect', 'rapid,', 'complete', 'mixing', '.', 'of', 'the', 'effluent', 'with', 'the', 'receiving', 'strean.', 'It', 'is', 'believed', 'that', 'for', 'effluent', 'dominated', 'streams,', 'a', 'steady', 'state', 'complete', 'mix', 'calculation', 'is', 'adequate', 'for', 'addressing', 'the', 'above', 'concerns,', 'and', 'is’closely', 'representative', 'of', 'actual', 'mixing', 'conditions', 'instream.', 'Effluent', 'dominated', 'is', 'defined', 'as', 'an', 'instream', 'waste', 'concentration', '(IWC)', 'of', 'greater', 'than', '50%', 'at', 'the', 'critical', 'conditions', '(in', 'this', 'case,', 'the', '1Q10).', 'For', 'these', 'effluent', 'dominated', 'situations', 'the', 'calculated', 'WLAa', 'will', 'be', 'relatively', 'small', 'and', 'the', 'effluent', 'containing', 'the', 'relatively', 'small', 'WLAa', 'should', 'be', 'completely', 'mixed', 'instream', 'in', 'a', 'relatively', 'rapid', 'manner.', 'This', 'results', 'in', 'a', 'small', 'allocated', 'impact', 'zone', 'that', 'may', 'contain', 'concentrations', 'of', 'pollutants', 'above', 'the', 'acute', 'standard,', 'but', 'the', 'size', 'of', 'the', 'zone', 'and', 'the', 'relative', 'small', 'concentratioris', 'of', 'pollutants', 'in', 'the', 'zone', 'should', 'guard', 'against', 'lethality.', 'In', 'order', 'to', 'address', 'the', 'acncape', 'of', 'providing', 'an', 'adequate', 'zone', 'of', 'passage', 'for', 'passing', 'or', 'drifting', 'organisms,', 'the', 'mixing', 'zone', 'standard', 'presents', 'latitudinal', 'spatial', 'restrictions.', 'These', 'spatial', 'restrictions', 'involve', 'one-half', 'the', 'width', 'of', 'the', 'stream', 'or', 'one', 'third', 'the', 'cross', 'sectional', 'area', 'of', 'the', 'stream.', 'In', 'order', 'to', 'address', 'the', 'zone', 'of', 'passage', 'restrictions,', 'the', 'steady', 'state', 'complete', 'mix', 'must', 'be', 'performed', 'with', 'the', 'fraction', 'of', 'the', 'receiving', 'stream', 'that', 'provides', 'for', 'an', 'adequate', 'zone', 'of', 'passage', 'and', 'that', 'addresses', 'the', '©', 'latitudinal', 'spatial', 'restrictions.', 'Since', 'stream', 'bottom', 'configurations', 'vary', 'from', 'site', 'to', 'site,', 'a', 'cross', 'sectional', 'area', 'may', 'not', 'be', 'a', 'realistic', 'measure', 'for', 'general', 'guidance', 'on', 'addressing', 'a', 'zone', 'of', 'passage.', 'It', 'is', 'believéd', 'that', 'the', 'one-half', 'width', 'of', 'the', 'receiving', 'stream', '(considered', 'as', 'one-half', 'the', 'volume', 'of', 'stream', 'flow)', 'is', 'the', 'appropriate', 'variable', 'to', 'use', 'in', 'addressing', 'the', '—', 'latitudinal', 'restrictions.', 'Since', 'the', 'one-half', 'of', 'the', 'cross', 'sectional', 'area', 'is', 'the', 'limiting', 'latitudinal', 'restriction,', 'the', 'steady', 'state', 'complete', 'mix', 'calculation', 'must', 'be', 'performed', 'with', 'one-half', 'the', 'volume', 'of', 'the', 'critical', 'stream', 'flows', '(1010).', 'If', 'the', 'permit', 'writer', '|', 'has', 'information', 'that', 'indicates', 'that', 'the', 'receiving', 'stream', 'bottom', 'configuration', 'at', 'the', 'discharge', 'point', 'is', 'nonuniform', 'and', 'results', 'in', 'most', 'of', 'the', 'receiving', 'stream', 'volume', 'being', 'channeled', 'at', 'the', 'discharge', 'point', 'shore,', 'the', 'permit', 'writer', 'may', 'perform', 'the', 'steady', 'state', 'complete', 'mix', 'calculation', 'with', 'one-third', 'of', 'the', 'critical', 'stream', 'flow.', ' ', 'reseonpeos']