1. (1) The director shall classify all wastewater treatment plants according to the criteria in Table 4.
2. (2) If Table 4 indicates multiple classifications, the department will classify the wastewater treatment plant at the higher classification.
3. (3) The operator in responsible charge of the wastewater treatment plant must be certified at a level equal to or higher than the plant classification.

4. (4) When the plant is operated on more than one daily shift, the lead operator of each shift must be certified no lower than one level below the plant classification.

   Table 4

   Treatment Plant Classification Criteria

   Treatment Plant Classification Criteria
   Treatment Type	Design Flow MGD	Classification
   Primary	≤ 1	I
   ˃ 1 ≤ 10	II
   ˃ 10 ≤ 20	III
   ˃ 20	IV
   Lagoon (Nonaerated)	All	I
   Lagoon (Aerated)	≤ 1	I
   ˃ 1	II
   Biofiltration	≤ 1	II
   ˃ 1 ≤ 10	III
   ˃ 10	IV
   Extended aeration	≤ 5	II
   ˃ 5	III
   Activated sludge	≤ 1	II
   ˃ 1 ≤ 10	III
   ˃ 10	IV
   SBR	≤ 1	II
   ˃ 1 ≤ 10	III
   ˃ 10	IV
   Wetland treatment	≤ 1	I
   ˃ 1 ≤ 5	II
   ˃ 5	III
   Tertiary	≤ 5	III
   ˃ 5	IV
   MBR	≤ 1	II
   ˃ 1 ≤ 10	III
   ˃ 10	IV

5. (5) Plants may be classified differently than indicated in Table 4 if:

   1. (a) They have characteristics that make operation more or less complex or difficult than other similar plants with the same flow range.
   2. (b) The conditions of flow or the use of the receiving waters require an unusually high degree of plant operational control.
   3. (c) They use an approved method of wastewater treatment that is not included in this section.

[Statutory Authority: Chapter 70.95B RCW. WSR 19-15-025 (Order 18-02), § 173-230-330, filed 7/10/19, effective 8/10/19.]