Section 131.46 - Aquatic life criterion for cadmium in Oregon(a)Scope. This section promulgates an acute aquatic life criterion for cadmium in freshwaters in Oregon.(b)Criterion for cadmium in Oregon. The aquatic life criterion in Table 1 applies to all freshwaters in Oregon where fish and aquatic life are a designated use. Table 1-Cadmium Aquatic Life Criterion for Oregon Freshwaters
| Metal | CAS No. | Criterion Maximum Concentration (CMC)3 ([MICRO]g/L) |
| Cadmium1 2 | 7440439 | [e (0.9789 * ln(hardness) - 3.866)] * CF
Where CF = 1.136672 - [(ln hardness) * (0.041838)]. |
1 The criterion for cadmium is expressed as the dissolved metal concentration.
2 CF is the conversion factor used to convert between the total recoverable and dissolved forms of cadmium. The term (ln hardness) in the CMC and the CF equation is the natural logarithm of the ambient hardness in mg/L (CaCO3). The default hardness concentrations from the applicable ecoregion in Table 2 of paragraph (c) of this section shall be used to calculate cadmium criteria in the absence of sufficiently representative ambient hardness data.
3 The CMC is the highest allowable one-hour average instream concentration of cadmium. The CMC is not to be exceeded more than once every three years. The CMC is rounded to two significant figures.
(c)Estimated Values To Calculate Cadmium Criteria. The default inputs to calculate cadmium criteria in the absence of sufficiently representative ambient data are shown in Table 2. Table 2-Hardness Defaults Within Each Level III Ecoregion in Oregon
| Level III ecoregion | Hardness
(mg/L) |
| 1 Coast Range | 34.12 |
| 3 Willamette Valley | 32.39 |
| 4 Cascades | 28.39 |
| 9 Eastern Cascades Slopes and Foothills | 36.08 |
| 10 Columbia Plateau | 58.82 |
| 11 Blue Mountains | 43.49 |
| 12 Snake River Plain | 123.5 |
| 78 Klamath Mountains | 40.61 |
| 80 Northern Basin and Range | 98.62 |
(d)Applicability.(1) The criterion in paragraph (b) of this section applies to freshwaters in Oregon where fish and aquatic life are a designated use, and applies concurrently with other applicable water quality criteria.(2) The criterion established in this section is subject to Oregon's general rules of applicability in the same way and to the same extent as are other federally promulgated and state-adopted numeric criteria when applied to freshwaters in Oregon where fish and aquatic life are a designated use. (i) For all waters with mixing zone regulations or implementation procedures, the criterion applies at the appropriate locations within or at the boundary of the mixing zones and outside of the mixing zones; otherwise the criterion applies throughout the water body including at the end of any discharge pipe, conveyance or other discharge point within the water body.(ii) The state shall not use a low flow value that is less stringent than the values listed below for waters suitable for the establishment of low flow return frequencies (i.e., streams and rivers) when calculating the available dilution for the purposes of determining the need for and establishing Water Quality-Based Effluent Limitations in National Pollutant Discharge Elimination System permits: Acute
criteria
(CMC) | 1Q10 or 1B3 |
| Where: |
| 1. 1Q10 is the lowest one-day average flow event expected to occur once every ten years, on average (determined hydrologically). |
| 2. 1B3 is the lowest one-day average flow event expected to occur once every three years, on average (determined biologically). |