(1) Minimum horizontal setback distances (in feet) shown in Table 3 of this rule must be maintained.

(2) A waiver of the setback distance for a cistern may be granted by the department, pursuant to ARM 17.36.601, if the applicant demonstrates that the elevation of the cistern is higher than the elevation of the septic tank, other components, or drainfield/sand mound.

(3) A waiver of the setback distance between drainfields/sand mounds and surface waters, springs, and floodplains may be granted by the department, pursuant to ARM 17.36.601, only if:

(a) the applicant demonstrates that ground water flow at the drainfield site cannot flow into the surface water or spring; or

(b) the surface water or spring seasonally high water level is a minimum of 100 feet horizontal distance from the drainfield and the bottom of the drainfield will be at least two feet above floodplain elevation.

(4) The department may require more than 100 feet of separation from the floodplain or from surface water or springs if it determines that site conditions or water quality nondegradation requirements indicate a need for the greater distance.

 TABLE 3

 SETBACK DISTANCES

 

	Water Supply Wells	Sealed Components (1) and Other Components (2)	Drainfield/ Sand Mounds
Public or Multi-user Wells/Springs	-	100	100
Other Wells	-	50	100
Suction Lines	-	50	100
Cisterns	-	25	50
Roadcuts, Escarpment	-	10 (3)	25
Slopes > 25% (4)	-	10 (3)	25
Property Boundaries	10	10	10
Subsurface Drains	-	10	10
Water Lines	-	10	10
Drainfields/ Sand Mounds	100	10	-
Foundation Walls	-	10	10
Surface Water, Springs	100 (5)	50	100
Floodplains	10	- (1) 100 (2)	100

 

(1) Sealed components include sewer lines, sewer mains, septic tanks, grease traps, dosing tanks and pumping chambers.

(2) Other components include intermittent and recirculating sand filters, package plants and evapotranspiration systems.

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

(4) Down-gradient of the sealed component, other component, or drainfield/sand mound.

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