(1) Except as provided in ARM 17.36.916, all wastewater treatment systems must be designed and constructed in accordance with the applicable requirements in ARM 17.36.913 and in department Circular DEQ-4, 2004 edition.
(2) Department Circular DEQ-4, 2004 edition, which sets forth standards for subsurface sewage treatment systems is adopted and incorporated by reference for purposes of this subchapter. Copies are available from the Department of Environmental Quality, P.O. Box 200901, Helena, MT 59620-0901.
(3) Wastewater treatment
systems must be located to maximize the vertical separation distance from the
bottom of the absorption trench to the seasonally high ground water level,
bedrock, or other limiting layer, but under no circumstances may this vertical
separation be less than four feet of natural soil.
(4) A replacement area or
replacement plan must be provided for each new or expanded wastewater treatment
system. Replacement areas and plans must comply with the requirements of this
subchapter.
(5) A site evaluation must
be performed for each wastewater treatment system. As determined by the
reviewing authority, the site evaluation may include the following:
(a) soil descriptions for
proposed wastewater treatment systems. Soil descriptions must be based on data
obtained from test holes within 25 feet of each wastewater treatment location.
Test holes must be at least eight feet in depth unless a limiting layer
precludes digging to eight feet;
(b) percolation test
results within the boundaries of the proposed wastewater treatment system; and
(c) if the applicant or the
reviewing authority has reason to believe that ground water will be within
seven feet of the surface at any time of the year within the boundaries of the
system, the applicant must provide data to demonstrate that the minimum
separation distance required by (3) between the absorption trench bottom and
the seasonally high ground water level can be maintained. The reviewing
authority may require the applicant to install ground water observation wells
to a depth of at least eight feet to determine the seasonally high ground water
level. The applicant shall monitor the observation wells through the
seasonally high ground water period. Measurement must occur for a long enough
period of time to detect a peak and a sustained decline in the ground water
level.
(6) If a
department-approved public collection and treatment system is readily available
within a distance of 200 feet of the property line for connection to a new
source of wastewater, or as a replacement for a failed system, and the owner or
managing entity of the public collection and treatment system approves the
connection, wastewater must be discharged to the public system. For purposes
of this rule:
(a) a public system is not
"readily available" if there is evidence demonstrating that
connection to the system is physically or economically impractical, or that
easements cannot be obtained; and
(b) a connection is "economically impractical" if the cost of connection to the public system equals or exceeds three times the cost of installation of an approvable system on the site.
(7) Wastewater treatment systems, except for sealed components that are designed, constructed, and tested as set out in ARM 17.36.918, may not be located in drainage ways.
SUBSURFACE WASTEWATER TREATMENT