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These are technology-based limitations on pollutant discharges to POTWs promulgated by EPA in accordance with Section 307 of the Clean Water Act that apply to specified process wastewater of particular industrial categories, see 40 CFR 403.6 and 40 CFR Parts 405- 471.

Wastewater discharge limits

King County limits certain pollutants and prohibits the discharge of wastes that can harm the wastewater system. Local limits and prohibitions apply to all facilities that discharge industrial wastewater into King County's sewage system. Local regulations are in addition to all federal limits on pollutants. Local limits are established for the following:

Corrosives (pH)

When wastewater is too acidic or too alkaline it can corrode the sewage system. Maximum and minimum limits are set for wastewater discharged into the sanitary sewer. Limits are measured by pH.


Maximum limit Minimum limits
In King County, the maximum limit for wastewater discharged into the sanitary sewer is pH 12.0.

The instantaneous minimum limit is violated when any grab sample (a single, random sample) or continuous recording is less than pH 5.0

The daily minimum limit is violated when a recording of 15 minutes or longer remains below pH 5.5. The limit is also violated when four consecutive grab samples collected in intervals of at least 15 minutes in a 24-hour period are all below pH 5.5.

Fats, oils, and grease (FOG)

There are two types of Fats, oils, and grease (FOG):

  • Nonpolar FOG
  • Polar FOG

Nonpolar FOG

The King County limit for nonpolar FOG is 100 milligrams per liter of discharged wastewater. Nonpolar FOG can harm the biological phase of sewage treatment where microbes are used to break down wastes.

Industries use oil and water separators to pretreat waste water that contains nonpolar FOG. Separator plans must be approved by King County Industrial Waste (KCIW). KCIW has also given some local sewer utilities the authority to approve separator plans. 

View the KCIW oil and water separator fact sheet for plan submittal information installation guidelines (401KB)

Free-floating polar FOG

Free-floating polar FOG can block sewer lines. Dischargers are asked to minimize free-floating polar FOG. King County rules require:

  • Wastewater should not be discharged if free-floating polar FOG is visible on the surface or sides of a storage container.
  • A sample should contain less than 0.25 inches of free-floating polar FOG in a sample, per the KCIW-approved sampling method.
  • Dischargers do not add agents that emulsify free-floating polar FOG. 

FOG control plan

Some companies that discharge polar FOG in King County may need to complete a FOG control plan. The goal of the plan is to implement common sense controls of free-floating polar FOG. The basic components of the plans should include:

  • A written policy detailing support and commitment for the plan from management and corporate
  • A description of the facility type and a summary of what the facility is used for
  • The quantity of all FOG brought into the facility and quantities discharged to the sewer
  • Schematics of process areas that illustrate drains and discharge points connected to the sewer.
  • A description of current reduction, recycling, and treatment activities
  • Detail potential FOG reduction opportunities
  • Detail the reduction and control methods selected for implementation
  • Detail the processes that will be affected and the estimated reductions
  • List specific performance goals and the implementation schedule

Heavy metals and cyanide

King County waste discharge permits contain aqueous concentration limits, typically in units of milligrams-per-liter (mg/L); however, these permits also can contain mass-based limits for metals. The mass allocation procedure that the Industrial Waste Program uses involves reviewing the influent data for the applicable King County wastewater treatment plant and statistically determining the loading amount, in pounds-per-day (lb/day), associated with one standard deviation of the average flow rate. The reasoning behind this is that on any given day a single discharger should not be allowed to discharge a mass of metal that would exceed the typical range of fluctuation of the wastewater treatment plant. As a pretreatment program we need to make sure that the concentration or mass limits that are in our permits will not cause problems at the wastewater treatment plants. 

Loading Limits for Metals, July 2014 (85KB)

King County local limits are set for total metals, not dissolved metals. Companies that are not classified as significant industrial users and that discharge less than 5,000 gallons of wastewater per day only need to comply with the instantaneous limits.


Parameter Daily Average Maximum mg/l (ppm) Instantaneous Maximum mg/l (ppm)


1.0 4.0


Chromium 2.75 5.0
Copper 3.0 8.0
Lead 2.0 4.0
Mercury 0.1 0.2
Nickel 2.5 5.0
Silver 1.0 3.0
Zinc 5.0 10.0
Cyanide* 2.0 3.0

*Cyanide amenable to chlorination, not total cyanide

Hydrogen Sulfide

Hydrogen sulfide gas can be dangerous to breathe and causes serious odor problems (the smell of rotten eggs). When hydrogen sulfide reacts with water it forms sulfuric acid. Sulfuric acid can cause corrosion and destroy sewage pipes.

There are two types of hydrogen sulfide:

  • Atmospheric sulfide
  • Soluble sulfide (dissolved in water)

Atmospheric sulfide

The following are atmospheric hydrogen sulfide limits as measured at a monitoring station designated by King County:

  • 15.0 parts per million volume (ppmv) as a 15-minute average
  • 10.0 ppmv as an 8-hour average
  • 3.0 ppmv as a 7-day average

Soluble sulfide

King County may restrict soluble sulfide discharges on a case-by-case basis. For guidance, King County has a screening limit of 0.1 mg/liter.

Organic Compounds

Organic compounds discharged into the sewer may cause toxic gases and fumes, which can harm sewer workers. Examples of organic compounds include:

  • Solvents
  • Cleaners
  • Thinners
  • Pesticides
  • Laboratory chemicals 

The King County Industrial Waste Program (KCIW) has developed screening levels for certain volatile organic compounds (VOCs). We provide VOC screening levels (25KB) as guidance to industrial users of the King County sewer system. These screening levels are not an authorization to discharge. Businesses can get authorization to discharge industrial wastewater with a discharge authorization or waste discharge permit issued by KCIW. 

Prohibited wastewater discharges

Flammable or explosive materials

It is against the law to discharge flammable or explosive solutions into the sewer system without formal approval from the King County Industrial Waste Program (KCIW). Before discharging, contact KCIW to find out if discharge of a solution is acceptable.

King County has the following local limits:

1. No person shall discharge any pollutant, as defined in 40 CFR (Code of Federal Regulations) 403.5, that creates a fire or explosion hazard in any sewer or treatment works, including, but not limited to, with a closed-cup of less than 140 degrees Fahrenheit or 60 degrees Centigrade using the test methods specified in 40 CFR 261.21.

2. At no time shall two successive readings on an explosion hazard meter, taken at the point of discharge into the system or at any point in the system, be more than 5 percent of the Lower Explosive Limit (LEL) of the meter nor shall any single reading be more than 10 percent of the LEL.

High Temperature

High temperatures can disrupt wastewater treatment plant operations. Industrial wastewater must not exceed 150 degrees Fahrenheit (65 degrees Celsius) when discharged into the public sewer system. King County prohibits discharges with temperatures above 104 degrees Fahrenheit (40 degrees Celsius) when they reach the treatment plant. Discharges hot enough to interfere with biological processes are also prohibited.

Settleable solids

Solids capable of settling can restrict or block wastewater flow in sewer lines. A company or facility that discharges solids that causes a sewage backup is liable for any damages.

King County has the following local limit for settleable solids:

  • Industrial wastewater must contain less than 7 milliliters per liter of solids capable of settling.

King County prohibits discharge of the following types of waste from non-domestic sources:

  • Materials such as ashes, sand, grass, and gravel
  • Solid or viscous pollutants in amounts that will obstruct the flow in the collection system and/or treatment plant
  • Solid material from food processing, including food grinder waste, which is not capable of passing through a one quarter inch sieve


A King County Public Rule specifies the local limits. Prohibited Discharge Standards are in 40 CFR (Code of Federal Regulations) 403.5 and King County Code 28.84.060. 

Wastewater discharge regulations

King County is responsible for telling organizations that send industrial wastewater to the King County sewer system about federal hazardous waste reporting requirements. This information is provided in accordance with Title 40 CFR Part 403.8(f)(2)(iii).


Industrial wastewater comes from any business system besides toilets or sinks in bathrooms or break rooms. Some industrial wastewater contains hazardous waste. This waste can be dangerous and potentially harmful to people or the environment. The United States Environmental Protection Agency (EPA) lists certain hazardous wastes under the Resource Conservation and Recovery Action (RCRA). 

Who must report hazardous waste discharges?

You must notify King County, EPA, and the Washington State Department of Ecology (Ecology) if your facility sends any of these substances to a King County sewer:

When to notify

  • Within 180 days from beginning to discharge the substances.
  • Within 90 days of the effective date of the published regulation whenever EPA adds additional wastes that your facility discharges to the RCRA list.

How to notify King County

You can notify King County by applying for an Industrial Waste Permit. Identifying the listed or characteristic RCRA hazardous wastes on your wastewater discharge permit application serves as notice to KCIW.

How to notify EPA and the Department of Ecology

To notify the EPA and Department of Ecology, send the following information to the addresses listed below.

 EPA Region 10  Washington State - Ecology

Director, Office of Air, Waste and Toxics

Environmental Protection Agency

1200 6th Avenue

Seattle, Washington, 98101

Manager, Solid and Hazardous Waste Management Division

Department of Ecology

Mail Stop PV-11

Olympia, Washington, 98504

If your facility sends more than 100 kilograms of listed or characteristic hazardous waste per month to the sewer, do the following:

  • Estimate the mass and concentration of the hazardous waste in the waste stream during that calendar month
  • Provide an estimate of what is expected during the following twelve months 


Revised Code of Washington (RCW) - Chapter 90.48 - Water pollution control

Grant of authority sewerage systems: Washington Administrative Code (WAC) - Chapter 173-208

Dangerous waste regulations: Washington Administrative Code (WAC) - Chapter 173-303


Portions of King County Code - Title 28 (518KB)

See portions of Sections 28.81, 28.82, and 28,84 on the established fees, rules, and regulations for the disposal of industrial waste into the sewerage system.

King County Public Rules

King County Industrial Waste Local Discharge Limits - PUT 8-13-2-PR (256KB)

Discharge of Construction Dewatering to the Sanitary Sewer - PUT 8-14-1-PR (232KB)

Discharge of Contaminated Groundwater to the Sanitary Sewer - PUT 8-15-1-PR (259KB)

Discharge of Cooling Water into the Sanitary Sewer - PUT 8-16-1-PR (217KB)

Discharge of Hauled Waste at a King County Publicly Owned Treatment Works (POTW) - PUT 8-22-1-PR (229KB)

King County Industrial Waste Fees - PUT 8-24-PR (5.51MB)

Enforcement Response Plan (ERP)

The ERP document outlines how King County will investigate and respond to instances of industrial user noncompliance. The ERP ensures:

  • Violations are corrected promptly
  • King County’s industrial users receive consistent treatment
  • Economic advantages for noncompliance are removed
  • King County to recover labor and material costs associated with violations

Read the Enforcement Response Plan (296KB)

National categorical pretreatment standards

The federal government has established wastewater discharge limits for specific industries. These industries are called categorical dischargers. Categorical dischargers must get a full King County permit. A permit is mandatory regardless of their wastewater discharge volume. Categorical discharge industries include:

  • Aluminum forming
  • Battery manufacturing
  • Centralized waste treatment
  • Circuit-board manufacturing
  • Coil coating
  • Copper forming
  • Electrical and electronic components
  • Electroplating
  • Inorganic chemical manufacturing
  • Leather tanning and finishing
  • Metal finishing
  • Metal foundries
  • Nonferrous metal manufacturing
  • Pesticide manufacturing
  • Petroleum refining
  • Pharmaceutical manufacturing
  • Porcelain enameling
  • Pulp and paper mills
  • Wood preserving