(1) The director may issue general permits to satisfy any or all of the waste water discharge permit requirements of chapter 90.48 RCW and the FWPCA.

(2) The director may issue general permits to cover categories of dischargers for geographic areas as described under subsection (3) of this section. The area shall correspond to existing geographic or political boundaries, such as:

(a) Designated planning areas under section 208 or 303 of the FWPCA;

(b) Sewer districts or other special purpose districts;

(c) City, county, or state political boundaries;

(d) State or county highway systems;

(e) Standard metropolitan statistical areas as defined by the federal Office of Management and Budget;

(f) Urbanized areas as designated by the Bureau of the Census; or

(g) Any other appropriate division or combination of boundaries.

(3) General permits may be written to cover the following within a described area:

(a) Stormwater sources; or

(b) Categories of dischargers that meet all of the following requirements:

(i) Involve the same or substantially similar types of operations;

(ii) Discharge the same or substantially similar types of wastes;

(iii) Require the same or substantially similar effluent limitations or operating conditions, and require similar monitoring; and

(iv) In the opinion of the director are more appropriately controlled under a general permit than under individual permits.

(4) The following discharges are not subject to permits under this chapter:

(a) Discharges to municipal sewerage systems of domestic wastewater from residential, commercial, or industrial structures.

(b) Any industrial or commercial discharge to a municipal sewerage system for which authority to issue permits has been granted to the municipality under RCW 90.48.165.

(c) Any industrial or commercial discharge to a municipal sewerage system operating under, and in compliance with, the applicable requirements of a local pretreatment program approved under section 307 of FWPCA and WAC 173-216-150. In the event of noncompliance, this exemption no longer applies and the discharger is immediately subject to enforcement action under chapter 90.48 RCW for discharging without a waste discharge permit.

(d) Discharges to municipal sewerage systems of wastes from industrial or commercial sources whose wastewater is similar in character and strength to normal domestic wastewater: Provided, That such discharges do not have the potential to adversely affect performance of the system. Examples of this type of discharge sources may include hotels, restaurants, laundries, and food preparation establishments.

(e) Discharges of domestic wastewater from a septic tank with subsurface sewage treatment and disposal and an ultimate design capacity less than or equal to fourteen thousand five hundred gallons per day. These systems are governed by on-site sewage disposal systems, chapter 246-272 WAC which is administered by the Washington state department of health.

(f) Discharges of domestic wastewater from a mechanical treatment system or lagoon followed by subsurface disposal with an ultimate design capacity less than or equal to three thousand five hundred gallons per day. These systems are governed by on-site sewage disposal systems, chapter 246-272 WAC which is administered by the Washington state department of health.