Table IV
Minimum Horizontal Separations
Items Requiring Setback | From edge of soil dispersal component and reserve area | From sewage tank and distribution box | From building sewer, and nonperforated distribution pipe |
Well | 100 ft. | 50 ft. | 50 ft. |
Public drinking water well | 100 ft. | 100 ft. | 100 ft. |
Nonpublic drinking water well | 100 ft. | 50 ft. | 50 ft. |
Public drinking water spring or surface water measured from the ordinary high-water mark | 200 ft. | 200 ft. | 100 ft. |
Nonpublic drinking water spring or surface water measured from the ordinary high-water mark1 | 100 ft. | 50 ft. | 50 ft. |
Nonpublic, in-ground, drinking water containment vessel3 | 20 ft. | 10 ft. | 10 ft. |
Pressurized water supply line or easement for water supply line | 10 ft. | 10 ft. | 10 ft. |
Closed geothermal loop4 or pressurized nonpotable water line | 10 ft. | 10 ft. | 10 ft. |
Decommissioned well (decommissioned in accordance with chapter 173-160 WAC) | 10 ft. | N/A | N/A |
Surface water measured from the ordinary high-water mark | 100 ft. | 50 ft. | 10 ft. |
Building foundation/in-ground swimming pool | 10 ft. | 5 ft. | 2 ft. |
Property or easement line | 5 ft. | 5 ft. | N/A |
Lined5 stormwater detention pond6 | |||
Down-gradient7: | 30 ft. | N/A | N/A |
Up-gradient7: | 10 ft. | N/A | N/A |
Unlined8 stormwater infiltration pond6 (up or down-gradient)7 | 100 ft. | 50 ft. | 10 ft. |
Irrigation canal or irrigation pond (up or downgradient) | 100 ft. | 50 ft. | 10 ft. |
Interceptor/curtain drains/foundation drains/drainage ditches | |||
Down-gradient2: | 30 ft. | 5 ft. | N/A |
Up-gradient2: | 10 ft. | N/A | N/A |
Subsurface stormwater infiltration or dispersion component6 | |||
Down-gradient7: | 30 ft. | 10 ft. | N/A |
Up-gradient7: | 30 ft. | 10 ft. | N/A |
Other site features that may allow effluent to surface | |||
Down-gradient2: | 30 ft. | 5 ft. | N/A |
Up-gradient2: | 10 ft. | N/A | N/A |
Down-gradient cuts or banks with at least 5 ft. of original, undisturbed soil above a restrictive layer due to a structural or textural change | 25 ft. | N/A | N/A |
Down-gradient cuts or banks with less than 5 ft. of original, undisturbed soil above a restrictive layer due to a structural or textural change | 50 ft. | N/A | N/A |
Soil dispersal components serving a separate OSS | 10 ft. | N/A | N/A |
1 If surface water is used as a public drinking water supply, the designer shall locate the OSS outside of the required source water protection area.
2 The item is down-gradient when liquid will flow toward it upon encountering a water table or a restrictive layer. The item is up-gradient when liquid will flow away from it upon encountering a water table or restrictive layer.
3 Any in-ground containment vessel used to store drinking water.
4 A network of underground piping carrying fluid under pressure used to heat and cool a structure.
5 Lined means any component that has the intended function of detaining the stormwater with no intention of dispersal into surrounding soil.
6 OSS components take precedence in cases of horizontal setback conflicts between OSS and stormwater components.
7 Down-gradient means that subsurface water flows toward and is usually located lower in elevation. Up-gradient means subsurface water does not flow toward and generally flat, or flows away from and generally located higher in elevation.
8 Unlined means any component that has the ability to or intended function of infiltrating the stormwater.
Wash. Admin. Code § 246-272A-0210
Statutory Authority: RCW 43.20.050. 05-15-119, § 246-272A-0210, filed 7/18/05, effective 7/1/07.