Washington Administrative Code
Title 246 - Health, Department of
SEWER SYSTEMS
Chapter 246-272B - Large on-site sewage system regulations
Part 6 - DESIGN AND TECHNICAL STANDARDS
Subpart A - General Requirements
Section 246-272B-06050 - Horizontal setbacks

Universal Citation: WA Admin Code 246-272B-06050

Current through Register Vol. 24-18, September 15, 2024

(1) The design engineer shall design the LOSS and verify it is installed in compliance with the minimum horizontal setbacks shown in Table 3 of this section.

(2) The design engineer shall increase the separation distance between the LOSS and a public drinking water well, spring, or surface water supply if required by the water purveyor's source water protection program, prepared under chapter 246-290 WAC, Group A public water supplies.

(3) The department may require greater horizontal setbacks than the minimum values shown in Table 3 when needed to protect public health and the environment. Such areas include, but are not limited to, those with:

(a) Highly permeable soils;

(b) Unconfined aquifers;

(c) Locally identified and state-identified areas of concern such as critical aquifer recharge areas or shorelines;

(d) Shallow soils;

(e) Saturated soils; and

(f) Hand-dug or improperly abandoned wells.

(4) The department may approve a sewer line placed less than ten feet from a water line only:

(a) With the written approval of the owner of the water line; and

(b) When the water line is protected from leakage and contamination consistent with the department of ecology "Criteria for Sewage Works Design," August 2008, or the department of ecology and department of health publication "Pipeline Separation Design and Installation Reference Guide," July 2006.

Table 3: Minimum Horizontal Setbacks

Items requiring setback

From edge of drainfield and reserve area

From sewage tank and distribution box

From building sewer, and nonperforated distribution pipe

Well or suction line

100 ft.

50 ft.

50 ft.

Public drinking water well

100 ft.

100 ft.

100 ft.

Spring used as a drinking water source

200 ft.

200 ft.

100 ft.

Surface water (measured from ordinary high water mark)

100 ft.

50 ft.

10 ft.

Pressurized water supply line

10 ft.

10 ft.

10 ft.

Decommissioned well: Decommissioned according to chapter 173-160 WAC

10 ft.

N/A

N/A

Lined storm water pond located:

.

Down-gradient from LOSS component:

75 ft.

10 ft.

10 ft.

Up-gradient from LOSS component

30 ft.

10 ft.

10 ft.

Unlined storm water pond (up or down-gradient from the LOSS component)

100 ft.

50 ft.

10 ft.

Building foundation and in-ground swimming pool located:

Down-gradient from LOSS component

30 ft.

5 ft.

2 ft.

Up-gradient from LOSS component

10 ft.

5 ft.

2 ft.

Property or easement line

5 ft.

5 ft.

N/A

Interceptor, curtain drains, foundation drains, lined drainage ditches located:

Down-gradient from LOSS component

30 ft.

5 ft.

N/A

Up-gradient from LOSS component

10 ft.

N/A

N/A

Other site features that may allow effluent to surface located:

Down-gradient from LOSS component

30 ft.

5 ft.

N/A

Up-gradient from LOSS component

10 ft.

N/A

N/A

Down-gradient cuts or banks with at least 5 ft. of original, undisturbed soil above a restrictive layer

25 ft.

N/A

N/A

Down-gradient cuts or banks with less than 5 ft. of original, undisturbed, soil above a restrictive layer

50 ft.

N/A

N/A

Down-gradient subsurface storm water infiltration or dispersion component

30 ft.

N/A

N/A

Up-gradient subsurface storm water infiltration or dispersion component

100 ft.

N/A

N/A

Other adjacent drainfields, including individual OSS beds or dispersal sectors

10 ft.

N/A

N/A

Statutory Authority: RCW 70.118B.020. 11-12-035, § 246-272B-06050, filed 5/25/11, effective 7/1/11.

Disclaimer: These regulations may not be the most recent version. Washington may have more current or accurate information. We make no warranties or guarantees about the accuracy, completeness, or adequacy of the information contained on this site or the information linked to on the state site. Please check official sources.
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