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COL0124D0 DE'PART7NEM OF HEALTH Water Quality Control Division WQC9-PE-B2 4300 Cherry Crerek Drive South Denver. Colorado 80222-1530 ADDENDUM TO RATIONALE SAAR AND GRAVEL PRODUC770N OPEIL1770NS (AND OTTI£R NONMETALLIC MINERALS EXCEPT FUEL) GENERAL PERMIT IN COLORADO COLORADO DISCHARGE PERMIT NUMBER COG-500 PURPOSE OF AMENDMENT The renews! permit did not include the specific numeric limits for process water discharges from the industrial sand category, whidr is roverec! by the Federal Ef}Suertr Guidelines (40 CFR 436, Subpar DJ. Therefore, the permit hat been modified to include the appropriate limits for this category. The itulustrial sand category was previously included in the list ojjacility types in paragraph a, below. Under the new m~egory (paragraph c, below), the 30-day average 7SS limit is slightly stricter, and a daily maximum limit is included, as opposed to a day average limit. The other limits are the same. The Federal Effluent Guidelines also cover process-get+erated wastewater from facilities employing NF (Hydrofluoric) flotation. Howevrr, this permit does not include the Federal numeric limits for this type of jaciliry. This rs a genera! permit, designed to rover the widest possible range ojfacilities with similar wastewater characteristic. In effectively achieving this broad coverage, the pa~r+it must also be relatively simple. Therefore, some of the more irrdividualisric or complex eff/utN limi[ations, suc/r as for process-generatrd wastewater from itulustrinl satin facilities employing HFfloration, are not included in this permit. lndust,~a/sand (aciliries employing HF flotation are sot allowed to discharge process wales under this permit. !f an applicam wishes to discharge process water from this type of jaciliry, they msst apply for an individual permit. Howeuer, this type of jaciliry may discharge slormwaler under this permit, ns allowed under Pan L C of the permit. Numeric Limitations: Numeric limits will be applied for some of the industrial categories covered by this permit. These limits are from the EPA Federal Guidelines for the applicoble point sourtt category, as folbws: a. Mineral mining and proctirsitrg point sourer category - 40 CFR 436 - subpar B (meshed stone), C (construction sntrd acrd gra+rl), R (phosphate rock) -and all other industrial jaclities cohered under S1C Code 14, except those speciflcn!!y listed in paragraphs 6 and c below, and concrete batch plantt located at any facility otherwise covered by this gerrernl permit: Table 1 -Effluent Limits Parameter Limit Rationale Flow, MGD 7SS, rug/I pH, s.. u. Oil nrrd Grease, mg/1 Tots! Dissolved Solids, mg/I (Colo. River Bruits orrlyJ Total Phosphorus (as P), mg/I Repon a/ NA 30/45 b/ Stare E,Qluenr Regulation 6.5-9.0 c/ Water Quality Standards 10 a/ State Eflluem Regulations Repon n/ Salinity Regulations Repon n/d/ Bern Professional Judgment Footnotes on fallowing pnge.