(1) Minimum horizontal setback distances (in feet) are as follows:

 

TABLE 1

SETBACK DISTANCES

 

	Sealed components (1) and other components (2)	Absorption systems (3)
Public or multi-user wells/springs	100	100
Other wells	50	100
Suction lines	50	100
Cisterns	25	50
Roadcuts, escarpments	10 (4)	25
Slopes > 25% (5)	10 (4)	25
Property boundaries	10	10
Subsurface drains	10	10
Water lines	10	10
Drainfields/sand mounds (3)	10	-
Foundation walls	10	10
Surface water, Springs	50	100
Floodplains	--(1) 100 (2)	100

 

(1) Sealed components include sewer lines, sewer mains, septic tanks, grease traps, dosing tanks, pumping chambers, holding tanks and sealed pit privies. Holding tanks and sealed pit privies must be located at least 10 feet outside the floodplain or any openings must be at least two feet above the floodplain elevation.

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

(3) Absorption systems include absorption trenches, absorption beds, sand mounds, and other drainfield type systems that are not lined or sealed. This term also includes seepage pits and unsealed pit privies.

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

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

 

(2) The reviewing authority may require greater horizontal separation distances than those specified in Table 1, if it determines that site conditions or water quality nondegradation requirements indicate a need for the greater distance.

(3) If the floodplain has not been designated and its level relative to a wastewater system is in question, the applicant shall submit evidence adequate to allow the reviewing authority to establish the location of the floodplain.

(4) Sealed components of wastewater treatment systems, if located within a 100-year floodplain, must be designed and constructed to prevent surface water and ground water inundation, and pump lines must be pressure tested prior to use. Pipes must have a pressure rating of at least two times the operating pressure or pump shutoff pressure, whichever is greater. Pipes must be tested at 1 1/2 times the operating pressure or pump shutoff pressure, whichever is greater, or must be tested as specified by the manufacturer.

(5) The setbacks in this rule are not applicable to gray water irrigation systems that meet the requirements of ARM 17.36.919.