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20 <br /> <br />upon the MAHL minus the background (commercial and residential) loadings and <br />a safety factor. The City uses a combination of uniform concentration and industry <br />specific mass based limits to establish local limits that ensure MAHLs are not <br />exceeded. Any applicable local limits shall be included in individual Industrial User <br />wastewater discharge permits or other control mechanisms. At no time shall the <br />City allocate loading to permitted users that causes these loadings to be exceeded: <br />Parameter lb/day <br />Arsenic (total) 5.29 <br />Cadmium (total) 2.01 <br />Chromium (total) 173 <br />Copper (total) 5.91 <br />Cyanide (total) 0.87 <br />Lead (total) 10.4 <br />Mercury (total) 0.11 <br />Molybdenum (total) 7.63 <br />Nickel (total) 7.59 <br />Selenium (total) 7.48 <br />Silver (total) 0.93 <br />Zinc (total) 108 <br />Biochemical Oxygen Demand1 83,000 <br />Total Suspended Solids1 89,000 <br />1 Established by NPDES Permit <br /> <br />Local limits apply at the point where the wastewater is discharged to the POTW <br />(end of the pipe). Categorical pretreatment standards apply at the end of the <br />process. However, the Director may elect to have local limits apply after <br />pretreatment and/or prior to mixing with dilution flows. <br />All concentrations for metallic substances are for total metal unless indicated <br />otherwise. <br />Where a user is subject to a categorical pretreatment standard and a local limit <br />for a given pollutant, the more stringent limit or applicable pretreatment <br />standard shall apply. <br />The City Council authorizes the Director to revise local limits. <br />C. POTW Protection Criteria <br />The City has established the following criteria (in mg/L) based upon technical evaluation <br />of the background loading. Any user proposing to discharge wastewater that contains <br />the following pollutants at or below the listed concentration shall not be required to <br />discharge under an industrial wastewater discharge permit unless the discharge meets