Administrative Rules of Montana
Department 17 - ENVIRONMENTAL QUALITY
Chapter 17.36 - SUBDIVISIONS/ON-SITE SUBSURFACE WASTEWATER TREATMENT
Subchapter 17.36.3 - Subdivision Requirements
Rule 17.36.323 - SETBACKS

Universal Citation: MT Admin Rules 17.36.323

Current through Register Vol. 18, September 20, 2024

(1) Minimum setback distances, in feet, shown in Table 2 of this rule must be maintained, except as provided in the table footnotes or as allowed through a deviation granted under ARM Title 17, chapter 38, subchapter 1. The setbacks in this rule are not applicable to gray water irrigation systems that meet the setbacks and other requirements of ARM 17.36.319.

TABLE 2

SETBACK DISTANCES

(in feet)

From

To

Drinking Water Wells

To

Sealed Components (1) and Other Components (2)

To

Drainfields/Soil Absorption Systems (3)

Public or multiple-user drinking water wells/springs

-

100 (4)

100

Individual and shared drinking water wells

-

50 (18)

100 (18)

Other wells (5)

-

50 (4)

100 (4)

Suction lines

-

50

100

Cisterns

-

25

50

Roadcuts, escarpment

-

10 (6)

25

Slopes > 35 percent (7)

-

10 (6)

25

Property boundaries

10 (8)

10 (8)

10 (8)

Subsurface drains

-

10

10

Water mains

-

10 (9)

10

Drainfields/Soil absorption systems

100

10

-

Foundation walls

-

10

10

Surface water (10), springs

100 (4) (11) (12)

50 (4) (11)

100 (4) (11) (13)

Floodplains

10 (4) (11)

- Sealed components

- no setbacks (1)

Other components - 100 (2) (4) (11)

100 (11) (14)

Mixing zones

100 (4) (18)

-

-

Storm water ponds and ditches (15)

25 (4) (16)

10 (4)

25 (4)

Sewage Lagoons

1000 (17)

-

-
(1) Sealed components include holding tanks, sealed pit privies, raw wastewater pumping stations, the components addressed in chapters 4 and 5 of Department Circular DEQ-4, and those components completely contained within a sealed vessel. Sealed components must meet the requirements of ARM 17.36.322(4). Drainfields do not have to meet setbacks to effluent transport pipes, manifolds, drop boxes, and distribution pipes as described in section 4.3 of DEQ-4.

(2) Other components include the components addressed in Department Circular DEQ-4, Chapter 7, except those components completely contained within a sealed vessel.

(3) Absorption systems include the systems addressed in Department Circular DEQ-4, Chapters 6 and 8, subject to the limitations in ARM 17.36.321.

(4) A waiver of this requirement may be granted by the department pursuant to ARM 17.36.601.

(5) Other wells include, but are not limited to, irrigation and stock watering, but do not include observation wells as addressed in Department Circular DEQ-4.

(6) Sewer lines and sewer mains may be located in roadways and on steep slopes if the lines and mains are safeguarded against damage.

(7) Down-gradient of the sealed component, other component, or drainfield/soil absorption system.

(8) Easements may be used to satisfy the setback to property boundaries.

(9) Unless a waiver is granted by the department pursuant to ARM 17.36.601, sewer mains that cross water mains must be laid with a minimum vertical separation distance of 18 inches between the mains.

(10) For purposes of this rule, "surface water" does not include intermittent storm water.

(11) The department may require more separation from the floodplain or from surface water or springs if it determines that site conditions or water quality requirements indicate a need for the greater distance.

(12) Pursuant to Department Circular DEQ-20, the reviewing authority may require greater than a 100-foot horizontal separation between a well and surface water if there is a potential that the well may be influenced by contaminants in the surface water.

(13) A waiver may be granted by the department. In addition to the requirements of ARM 17.36.601, a waiver request from this setback must demonstrate that ground water flow at the drainfield site cannot flow into the surface water or spring. The setback between drainfields or soil absorption systems to irrigation ditches does not apply if the ditch is lined with a full culvert.

(14) After consultation with the local health department, a waiver may be granted by the department, pursuant to ARM 17.36.601. In addition to the requirements of ARM 17.36.601, a waiver request from this setback must:
(a) demonstrate that the surface water or spring seasonally high water level is at least 100-foot horizontal distance from the drainfield;

(b) demonstrate that the bottom of the drainfield will be at least two feet above the maximum 100-year flood elevation; and

(c) provide any required approval(s) from the local floodplain coordinator.

(15) Storm water ponds and ditches are those structures that temporarily hold or convey water as part of storm water management.

(16) The setback is 100 feet for public wells, unless a deviation is granted under ARM Title 17, chapter 38, subchapter 1.

(17) A lesser setback may be allowed in accordance with ARM 17.30.1702.

(18) This setback applies unless the department has approved a smaller source-specific well isolation zone under Department Circular DEQ-20, Standard 1.8. In that case, the source specific well isolation zone distance applies.

AUTH: 76-4-104, MCA; IMP: 76-4-104, MCA

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