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and collection systems classified according to the population criteria in subrules (2) and
(6) of this rule may be placed in a higher classification by the department, by reason of
the incorporation in the treatment facility or collection system of special features of
design, by characteristics more difficult to operate than usual, by reasons of a particularly
difficult type of sewage, by reason of particular stream conditions or combinations
thereof.
(2) One of the following minimum classifications must be assigned to each treatment
facility that serves the public:
(a) Class A, treatment facilities serving or designed to serve a population of 50,000 or
more persons.
(b) Class B, treatment facilities serving or designed to serve a population of 10,000 or
more, but less than 50,000, persons.
(c) Class C, treatment facilities serving or designed to serve a population of 2,000 or
more, but less than 10,000, persons.
(d) Class D, treatment facilities serving or designed to serve a population of less than
2,000 persons.
(3) Treatment facilities utilizing the waste stabilization lagoon process shall be
classified by the department into 1 of the 2 following classes, designated as class L2 and
L1:
(a) Class L2, treatment facilities utilizing the waste stabilization lagoon process that
include special mechanical devices such as aerators, chemical precipitation, disinfection,
or other factors. Class L2 must be considered a higher classification than class L1.
(b) Class L1, treatment facilities utilizing the waste stabilization lagoon process that do
not include special mechanical devices such as aerators, chemical precipitation,
disinfection, or other factors.
(4) Treatment facilities that require minimal operation and control, and serve a
population of less than 1,000 persons may be classified by the department as a special
classification, designated as class SC. These treatment facilities include, but are not
limited to, septic tank and tile field systems, and recirculating sand filters.
(5) Class RTB, treatment facilities that retain and treat discharge from approved
facilities serving a combined sewer system in accordance with its discharge permit.
(6) Collection systems that convey wastewater to a treatment facility, with all flow
transported through a combination of gravity sewers, gravity sewers and pump stations
with force mains, or low-pressure collection systems, must be classified by the
department into 1 of the 4 following classes, designated as class C1, C2, C3, or C4, with
class C1 being the highest:
(a) Class C1, collection systems serving or designed to serve a population of 50,000 or
more persons.
(b) Class C2, collection systems serving or designed to serve a population of 10,000 or
more, but less than 50,000, persons.
(c) Class C3, collection systems serving or designed to serve a population of 2,000 or
more, but less than 10,000, persons.
(d) Class C4, collection systems serving or designed to serve a population of 150 or
more, but less than 2,000 persons unless otherwise required by the department.
R 299.2912 Treatment facility classification and collection system changes.