020-11 Wyo. Code R. § 11-56
(a) Surface water protection. Discharge from a land treatment system to a surface water body will be regulated by the NPDES permit process.
(b) Groundwater protection. Percolation water from land treatment of waste or wastewater shall not degrade groundwater quality to the point at which it is no longer suitable for its current or potential use as described in Chapter 8 of the Wyoming Water Quality Regulations.
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IRRIGATION WATER QUALITY
Permissibility Classes for Salinity
Class C1, low salinity: --
Good water with little or no likelihood of salt accumulation under the leaching provided by average irrigation practices, except where subsurface drainage is inadequate.
Class C2, medium salinity: --
Can be used if a moderate amount of leaching occurs. Plants with moderate salt tolerance can be grown in most cases without special practices for salinity control.
Class C3, high salinity: --
Cannot be used on soils with restricted drainage. With adequate drainage, considerable excess water must be applied to each irrigation; irrigations must be made more frequently, and plants with a good salt tolerance should be selected.
Class C4, very high salinity: --
Not usable under ordinary conditions. On very light and permeable soils with excellent drainage, water may be usable with a large amount of excess leaching water, frequent irrigations, and very salt-tolerant crops.
Permissibility Classes for Alkalinity
Class S1, low sodium: --
Good for almost all soils and all Wyoming crops.
Class S2, medium sodium: --
Can cause alkali problems on heavy clayey soils, with low leaching, unless gypsum (or equivalent soil amendments) are present or added to the soils.
Class S3, high sodium: --
May create harmful levels of exchangeable sodium in all soils and will require special management--good drainage, high leaching, and organic matter additions. Soils containing natural gypsum may not develop alkali troubles. Chemical amendments may be necessary, but are not feasible with waters of very high salinity.
Class S4, very high sodium: --
Generally unsuited for irrigation. Special conditions of low salinity water, favorable gypsum content of soils, tolerant crops, and special management may permit use of these waters.
These water classes are based on recommendations of the United States Regional Salinity Laboratory and numerous state agricultural experiment stations.
TABLE I - Boron Class Limits
| Limits -- parts per million | Description | |||
| Class | Sensitive crops | Semi-tolerant crops | Tolerant crops | |
| 1 | Below 0.33 | Below 0.67 | Below 1.00 | Very low. No effect on crops. |
| 2 | 0.33 to 0.67 | 0.67 to 1.33 | 1.00 to 2.00 | Low. Very slight effect on crops. |
| 3 | 0.67 to 1.00 | 1.33 to 2.00 | 2.00 to 3.00 | Moderate. Significant yield depression. |
| 4 | 1.00 to 1.25 | 2.00 to 2.50 | 3.00 to 3.75 | High. Large yield depression anticipated. |
| 5 | Over 1.25 | Over 2.50 | Over 3.75 | Very high. Non-usable. |
TABLE II - Selenium Class Limits
| Class | Limits -- parts per million | Description |
| 1 | 0.00 to 0.10 | Low. No plant toxicity anticipated. |
| 2 | 0.11 to 0.20 | Medium. Usable -- possible long-term accumulation under particular conditions and should be watched |
| 3 | 0.21 to 0.50 | High. Doubtful -- probably toxic accumulation in plants except under especially favorable conditions |
| 4 | Over 0.50 | Very High. Non-usable under any conditions. |
TABLE III.
CHLORIDE AND SULFIDE LIMITS FOR THREE CLASSES OF IRRIGATION WATERS
| Chlorides | Sulfates | ||||
| Class | meq/L | mg/L | meq/L | mg/L | |
| I- | Excellent to good; or suitable for most plants under most conditions | less than 2-5.5 | 71.1 - 195.5 | 4 - 10 | 192 - 480 |
| II- | Good to injurious; harmful to some under certain conditions of soil, climate and practices | 2 -16 | 71.1 - 568.0 | 4 - 20 | 192 - 960 |
| III- | Injurious to unsatisfactory; unsuitable under most conditions | 6 -16 | 213 - 568 | 12 - 20 | 576 - 960 |
020-11 Wyo. Code R. § 11-56
Amended, Eff. 6/29/2018.