Current through Register Vol. 60, No. 12, December 1, 2021
Dissolved oxygen (DO): No wastes may be discharged and no
activities may be conducted that either alone or in combination with other
wastes or activities will cause violation of the following standards: The
changes adopted by the Commission on January 11, 1996, become effective July 1,
1996. Until that time, the requirements of this rule that were in effect on
January 10, 1996, apply:
(1) For water
bodies identified as active spawning areas in the places and times indicated on
the following Tables and Figures set out in OAR 340-041-0101 to 340-041-0340:
Tables 101B, 121B, and 190B, and Figures 130B, 151B, 160B, 170B, 180A, 201A,
220B, 230B, 260A, 271B, 286B, 300B, 310B, 320B, and 340B, (as well as any
active spawning area used by resident trout species), the following criteria
apply during the applicable spawning through fry emergence periods set forth in
the tables and figures and, where resident trout spawning occurs, during the
time trout spawning through fry emergence occurs:
(a) The dissolved oxygen may not be less than
11.0 mg/l. However, if the minimum intergravel dissolved oxygen, measured as a
spatial median, is 8.0 mg/l or greater, then the DO criterion is 9.0
mg/l;
(b) Where conditions of
barometric pressure, altitude, and temperature preclude attainment of the 11.0
mg/l or 9.0 mg/l criteria, dissolved oxygen levels must not be less than 95
percent of saturation;
(c) The
spatial median intergravel dissolved oxygen concentration must not fall below
8.0 mg/l.
(2) For water
bodies identified by the Department as providing cold-water aquatic life, the
dissolved oxygen may not be less than 8.0 mg/l as an absolute minimum. Where
conditions of barometric pressure, altitude, and temperature preclude
attainment of the 8.0 mg/l, dissolved oxygen may not be less than 90 percent of
saturation. At the discretion of the Department, when the Department determines
that adequate information exists, the dissolved oxygen may not fall below 8.0
mg/l as a 30-day mean minimum, 6.5 mg/l as a seven-day minimum mean, and may
not fall below 6.0 mg/l as an absolute minimum (Table 21);
(3) For water bodies identified by the
Department as providing cool-water aquatic life, the dissolved oxygen may not
be less than 6.5 mg/l as an absolute minimum. At the discretion of the
Department, when the Department determines that adequate information exists,
the dissolved oxygen may not fall below 6.5 mg/l as a 30-day mean minimum, 5.0
mg/l as a seven-day minimum mean, and may not fall below 4.0 mg/l as an
absolute minimum (Table 21);
(4)
For water bodies identified by the Department as providing warm-water aquatic
life, the dissolved oxygen may not be less than 5.5 mg/l as an absolute
minimum. At the discretion of the Department, when the Department determines
that adequate information exists, the dissolved oxygen may not fall below 5.5
mg/l as a 30-day mean minimum, and may not fall below 4.0 mg/l as an absolute
minimum (Table 21);
(5) For
estuarine water, the dissolved oxygen concentrations may not be less than 6.5
mg/l (for coastal water bodies);
(6) For ocean waters, no measurable reduction
in dissolved oxygen concentration may be allowed.
