Fox Metro Local Discharge Limits

(Ordinance #517, Section 300.120)

The following are numerical local discharge limits derived by Fox Metro using USEPA provided procedures.

Unless otherwise indicated, concentrations in this section are expressed in mg/L and refer to the total amount of the constituent present in all phases, whether solid, suspended or dissolved, elemental or combined, including all oxidation states. Where constituents may be measured as other than total, the word "total" is indicated for clarity.

The Hexane Extractable Material, indicated in this section and Section 300.125 of Ordinance #517, refers to the sum of polar hydrocarbons (such as vegetable oils, animal fats, and other highly biodegradable oils) and non-polar hydrocarbons (such as petroleum based oils and greases) as determined by HEM and SGT-HEM analyses. The Silica Gel Treated Hexane Extractable Material in this section refers to petroleum oil, non-biodegradable cutting oil, products of mineral oil origin and other non-polar hydrocarbons as determined by HEM and SGT-HEM analyses.

Discharges from each separate discharge of a User, as measured under the provisions of this Ordinance shall not contain in excess of the following concentrations based upon a 24-hour composite sample.

Discharges exceeding the numeric standard for Total Mercury shall be allowed if all of the following conditions are met:

• The discharger does not use mercury; or, the discharger uses mercury and this use cannot be eliminated; or, the discharger uses mercury only in chemical analysis or in laboratory or other equipment and takes reasonable care to avoid contamination of wastewater; and,

• The discharger is providing the best degree of treatment consistent with technological feasibility, economic reasonableness and sound engineering judgment. This may include no treatment for mercury; and,

• The discharger has an inspection and maintenance program likely to reduce or prevent an increase in the level of mercury discharges.

However, in no case shall any discharge of mercury, alone or in combination with other sources, cause pass through or interference at the POTW as prohibited by 40-CFR-403.5(a)(1).

• Discharges exceeding the numeric standard for Total Silver shall be allowed if all of the following conditions are met:

• The discharger does not use silver; or, the discharger uses silver and this use cannot be eliminated; or, the discharger uses silver only in chemical analysis or in laboratory or other equipment and takes reasonable care to avoid contamination of wastewater; and,

• The discharger is providing the best degree of treatment consistent with technological feasibility, economic reasonableness and sound engineering judgment as indicated in the most current version of the "Code of Management Practice for Silver Dischargers", as published by the Association of Metropolitan Sewerage Agencies (AMSA) and the Silver Council; and,

• The discharger has an inspection and maintenance program likely to reduce or prevent an increase in the level of silver discharges.

However, in no case shall any discharge of silver, alone or in combination with other sources, cause pass through or interference at the POTW as prohibited by 40-CFR-403.5(a)(1).

Discharges from each separate discharge of a User, as measured under the provisions of the Ordinance, shall not contain in excess of the following concentrations based upon a grab sample.

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