Water treatment plants and distribution systems at community and non-transient non-community public water systems are classified based on the size and complexity of the water system facility. Classification of a water system or water system facility determines the level of certification required for operators in direct responsible charge of a water system or water system facility as prescribed by OAR 333-061-0225.

1. (1) Small water system classification applies when a water system serves fewer than 151 service connections and:

   1. (a) Uses only groundwater as its source; or
   2. (b) Purchases finished water from another public water system.
2. (2) Water distribution classification applies when a water system is not classified as small in accordance with section (1) of this rule, and is based on the population served by the water system as specified in Table 50.

3. (3) Water treatment classification applies to water treatment plants when:

   1. (a) A water system is not classified as small in accordance with section (1) of this rule; and
   2. (b) Treatment is provided for contaminants identified in OAR 333-061-0030(1) through (5) and (7) by that water treatment plant.
   3. (c) Water treatment classification is based on a point system that reflects the complexity of water treatment present. Points are assigned as specified in Table 51. For the purposes of operator certification, water treatment plants are classified as identified in Table 52, based on the cumulative score of components identified in Table 51.

4. (4) Filtration endorsement is an additional classification that applies when a water treatment plant is classified as Water Treatment 2 and uses conventional or direct filtration treatment to treat surface water or groundwater under the influence of surface water. Filtration endorsement certification, as prescribed by OAR 333-061-0235, is required for operators designated in direct responsible charge of a water treatment plant receiving the filtration endorsement classification, except for those operators already certified at Water Treatment Level 3 or higher.

   [ED. NOTE: To view attachments referenced in rule text, click here for PDF copy.]

Statutory/Other Authority

ORS 448.131

Statutes/Other Implemented

ORS 448.450 & 448.455

History

PH 28-2025, amend filed 12/30/2025, effective 01/01/2026
PH 118-2024, amend filed 12/13/2024, effective 01/01/2025
PH 7-2023, amend filed 01/31/2023, effective 02/01/2023
PH 14-2014, f. & cert. ef. 5-8-14
PH 3-2013, f. & cert. ef. 1-25-13
PH 4-2009, f. & cert. ef. 5-18-09
PH 2-2006, f. & cert. ef. 1-31-06
PH 33-2004, f. & cert. ef. 10-21-04
PH 20-2004, f. & cert. ef. 6-18-04
PH 16-2004(Temp), f. & cert. ef. 4-9-04 thru 10-5-04
OHD 7-2002, f. & cert. ef. 5-2-02
HD 14-1997, f. & cert. ef. 10-31-97
HD 19-1990, f. 6-28-90, cert. ef. 7-2-90
Reverted to HD 18-1988, f. & cert. ef. 7-27-88
HD 11-1989(Temp), f. & cert. ef. 12-29-89
HD 18-1988, f. & cert. ef. 7-27-88
HD 2-1988(Temp), f. & cert. ef. 2-10-88