Hemlock Semiconductor Operations LLC — NPDES permit MI0027375: limits, due date and EPA's record

NPDES permit MI0027375 · Minor NON-POTW · effective, expires 2028-10-01 · EPA's file as of 2026-09-19

EPA's record, 2025-09-01 to 2026-08-31

Last period with anything received: 2026-08-31. Most often over: Chlorine, total residual (1).

Reporting

Reports are due about 21 days after each monitoring period ends (the most common figure among MI permits in EPA's filings — check your permit).

Limits in force (44)

Outfall	Parameter	Statistic	Limit	Months
002	Temperature, water deg. fahrenheit	DAILY MX	report only	all year
002	Thermal Discharge	MO AVG	report only	all year
002	Thermal Discharge	DAILY MX	report only	all year
002	Oxygen, dissolved [DO]	DAILY MN	>= 3 mg/L	Mar, Apr
002	Oxygen, dissolved [DO]	DAILY MN	>= 5 mg/L	Jan, Feb, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec
002	pH	DAILY MN	>= 6.5 SU	all year
002	pH	DAILY MX	<= 9 SU	all year
002	Solids, total suspended	MO AVG	<= 20 mg/L	all year
002	Solids, total suspended	DAILY MX	<= 30 mg/L	all year
002	Solids, total suspended	MO AVG	<= 250 lb/d	all year
002	Solids, total suspended	DAILY MX	<= 380 lb/d	all year
002	Phosphorus, total [as P]	MO AVG	<= .8 mg/L	all year
002	Phosphorus, total [as P]	DAILY MX	report only	all year
002	Phosphorus, total [as P]	MO AVG	<= 10 lb/d	all year
002	Phosphorus, total [as P]	DAILY MX	report only	all year
002	Chloride [as Cl]	DAILY MX	report only	all year
002	Sulfate, total [as SO4]	DAILY MX	report only	all year
002	Copper, total [as Cu]	DAILY MX	report only	all year
002	Flow, in conduit or thru treatment plant	MO AVG	report only	all year
002	Flow, in conduit or thru treatment plant	DAILY MX	report only	all year
002	Chlorine, total residual	DAILY MX	<= 38 ug/L	all year
002	Solids, total dissolved	MO AVG	<= 500 mg/L	Jan, Feb
002	Solids, total dissolved	MO AVG	<= 500 mg/L	May, Jun
002	Solids, total dissolved	MO AVG	<= 500 mg/L	Jul, Aug, Sep, Oct, Nov, Dec
002	Solids, total dissolved	MO AVG	<= 520 mg/L	Mar, Apr
002	Solids, total dissolved	DAILY MX	<= 760 mg/L	Jan, Feb
002	Solids, total dissolved	DAILY MX	<= 760 mg/L	May, Jun
002	Solids, total dissolved	DAILY MX	<= 750 mg/L	Jul, Aug, Sep, Oct, Nov, Dec
002	Solids, total dissolved	DAILY MX	<= 910 mg/L	Mar, Apr
002	Solids, total dissolved	MO AVG	<= 6300 lb/d	Jan, Feb
002	Solids, total dissolved	MO AVG	<= 6300 lb/d	May, Jun
002	Solids, total dissolved	MO AVG	<= 6300 lb/d	Jul, Aug, Sep, Oct, Nov, Dec
002	Solids, total dissolved	MO AVG	<= 6500 lb/d	Mar, Apr
002	Solids, total dissolved	DAILY MX	<= 9500 lb/d	Jan, Feb
002	Solids, total dissolved	DAILY MX	<= 9500 lb/d	May, Jun
002	Solids, total dissolved	DAILY MX	<= 9400 lb/d	Jul, Aug, Sep, Oct, Nov, Dec
002	Solids, total dissolved	DAILY MX	<= 11000 lb/d	Mar, Apr
002	Mercury, total [as Hg]	MO AVG	report only	all year
002	Mercury, total [as Hg]	DAILY MX	report only	all year
002	Mercury, total [as Hg]	MO AVG	report only	all year
002	Mercury, total [as Hg]	DAILY MX	report only	all year
002	Mercury, total [as Hg]	1D	<= 4 ng/L	all year
002	Mercury, total [as Hg]	1D	<= .00005 lb/d	all year
002	Outfall observation,visual, y/n response	VALUE	report only	all year