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RULE §285.32 Criteria for Sewage Treatment Systems

Published: 2015

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(a) Pipe from building to treatment system.
  (1) The pipe from the sewer stub out to the treatment
system shall be constructed of cast iron, ductile iron, polyvinyl
chloride (PVC) Schedule 40, standard dimension ratio (SDR) 26 or other
material approved by the executive director.
  (2) The pipe shall be watertight.
  (3) The slope of the pipe shall be no less than 1/8
inch fall per foot of pipe.
  (4) The sewer stub out should be as shallow as possible
to facilitate gravity flow.
  (5) A two-way cleanout plug must be provided between
the sewer stub out and the treatment tank. Only sanitary type fittings
constructed of PVC Schedule 40 or SDR 26 shall be used on this section
of the sewer. An additional cleanout plug shall be provided every
100 feet on long runs of pipe and within five feet of 90 degree bends.
  (6) Additional cleanout plugs shall be of the single
sanitary type.
  (7) The pipe shall have a minimum inside diameter of
three inches.
  (8) Pipe that crosses drainage easements shall be sleeved
with American Society for Testing and Materials (ASTM) Schedule 40
pipe; the pipes shall be buried at least one foot below the surface,
or buried less than one foot and encased in concrete; the outside
pipe shall have locater tape attached to the pipe; and markers shall
be placed at the easement boundaries to indicate the location of the
pipe crossing. Crossings shall be designed and constructed in a manner
that protects the pipe and the drainage way from erosion.
(b) Standard treatment systems.
  (1) Septic tanks. A septic tank shall meet the following
    (A) Tank volume. The liquid volume of a septic tank,
measured from the bottom of the outlet, shall not be less than established
in §285.91(2) of this title (relating to Tables). Additionally,
the liquid depth of the tank shall not be less than 30 inches.
    (B) Inlet and outlet devices. The flowline of the tank's
inlet device in the first compartment of a two-compartment tank, or
in the first tank in a series of tanks, shall be at least three inches
higher than the flowline of the outlet device. For a configuration
of the tank and inlet and outlet devices, see §285.90(6) and
(7) of this title (relating to Figures). The inlet devices shall be
"T" branch fittings, constructed baffles or other structures or fittings
approved by the executive director. The outlet devices shall use a
"T" unless an executive director approved fitting is installed on
the outlet. All inlet and outlet devices shall be installed water
tight to the septic tank walls and shall be a minimum of three inches
in diameter.
    (C) Baffles and series tanks. All septic tanks shall
be divided into two or three compartments by the use of baffles or
by connecting two or more tanks in a series.
      (i) Baffled tanks. In a baffled tank, the baffle shall
be located so that one half to two thirds of the total tank volume
is located in the first compartment. Baffles shall be constructed
the full width and height of the tank with a gap between the top of
the baffle and the tank top. The baffle shall have an opening located
below the liquid level of the tank at a depth between 25% and 50%
of the liquid level. The opening may be a slot or hole. If a "T" is
fitted to the slot or hole, the inlet to the fitting shall be at the
depth stated in this paragraph. See §285.90(6) of this title
for details. Any metal structures, fittings, or fastenings shall be
stainless steel.
      (ii) Series tanks. Two or more tanks shall be arranged
in a series to attain the required liquid volume. The first tank in
a two-tank system shall contain at least one half to two thirds the
required volume. The first tank in a three-tank system shall contain
at least one-third of the total required volume, but no less than
500 gallons. The first tank in a four or more tank system shall contain
no less than 500 gallons, and the last tank in a four or more tank
system shall contain no more than one third of the total required
volume. Interconnecting inlet and outlet devices may be installed
at the same elevation for multiple tank installations.
    (D) Inspection or cleanout ports. All septic tanks
shall have inspection or cleanout ports located on the tank top over
the inlet and outlet devices. Each inspection or cleanout port shall
be offset to allow for pumping of the tank. The ports may be configured
in any manner as long as the smallest dimension of the opening is
at least 12 inches, and is large enough to provide for maintenance
and for equipment removal. Septic tanks buried more than 12 inches
below the ground surface shall have risers over the port openings.
The risers shall extend from the tank surface to no more than six
inches below the ground. The risers shall be sealed to the tank. The
risers shall have inside diameters which are equal to or larger than
the inspection or cleanout ports. The risers shall be fitted with
removable watertight caps and prevent unauthorized access.
    (E) Septic tank design and construction materials.
The septic tank shall be of sturdy, water-tight construction. The
tank shall be designed and constructed so that all joints, seams,
component parts, and fittings prevent groundwater from entering the
tank, and prevent wastewater from exiting the tank, except through
designed inlet and outlet openings. Materials used shall be steel-reinforced
poured-in-place concrete, steel-reinforced precast concrete, fiberglass,
reinforced plastic polyethylene, or other materials approved by the
executive director. Metal septic tanks are prohibited. The septic
tank shall be structurally designed to resist buckling from internal
hydraulic loading and exterior loading caused by earth fill and additional
surface loads. Tanks exhibiting deflections, leaks, or structural
defects shall not be used. Sweating at construction joints is acceptable
on concrete tanks.
      (i) Precast concrete tanks. In addition to the general
requirements in this subparagraph, precast concrete tanks shall conform
to requirements in the Materials and Manufacture Section and the Structural
Design Requirements Section of ASTM Designation: C 1227, Standard
Specification for Precast Concrete Septic Tanks (2000) or under any
other standards approved by the executive director. A professional
engineer shall verify in writing that the manufacturer is in compliance
with ASTM Standard C 1227. This verification shall be submitted to
the permitting authority from the tank manufacturer. If this verification
has not been previously submitted or accepted by the permitting authority,
a new verification shall be completed within 30 days of the effective
date of this section.
      (ii) Fiberglass and plastic polyethylene tank specifications.

        (I) The tank shall be fabricated to perform its intended
function when installed. The tank shall not be adversely affected
by normal vibration, shock, climate conditions, nor typical household
chemicals. The tank shall be free of rough or sharp edges that would
interfere with installation or service of the tank.
        (II) Full or empty tanks shall not collapse or rupture
when subjected to earth and hydrostatic pressures.
      (iii) Poured-in-place concrete tanks. Concrete tanks
shall be structurally sound and water-tight. The concrete tank shall
be designed by a professional engineer.
      (iv) Tank manufacturer specifications. All precast
or prefabricated tanks shall be clearly and permanently marked, tagged,
or stamped with the manufacturer's name, address, and tank capacity.
The identification shall be near the level of the outlet and be clearly
visible. Additionally, the direction of flow into and out of the tank
shall be indicated by arrows or other identification, and shall be
clearly marked at the inlet and outlet.
    (F) Installation of tanks. For gravity disposal systems,
septic tanks must be installed with at least a 12 inch drop in elevation
from the bottom of the outlet pipe to the bottom of the disposal area.
A minimum of four inches of sand, sandy loam, clay loam, or pea gravel,
free of rock larger than 1/2 inch in diameter, shall be placed under
and around all tanks, except poured-in-place concrete tanks. Unless
otherwise approved by the permitting authority, tank excavations shall
be left open until they have been inspected by the permitting authority.
Tank excavations must be backfilled with soil or pea gravel that is
free of rock larger than 1/2 inch in diameter. Class IV soils and
gravel larger than one-half inch in diameter are not acceptable for
use as backfill material. If the top of a septic tank extends above
the ground surface, soil may be mounded over the tank to maintain
slope to the drainfield.
    (G) Pretreatment (Trash) tanks. If an aerobic treatment
unit does not prevent plastic and other non-digestible sewage from
interfering with aeration lines and diffusers, the executive director
may require the use of a pretreatment tank. All pretreatment tanks
shall meet all applicable structural and fitting requirements of this
    (H) Leak Testing. At the discretion of the permitting
authority, leak testing using water filled to the inside level of
the tank lid or to the top of the tank riser(s) may be required.
  (2) Intermittent sand filters. A typical layout and
cross-section of an intermittent sand filter is presented in §285.90(8)
of this title. Requirements for intermittent sand filters are as follows.

    (A) Sand media specifications. Sand filter media must
meet ASTM C-33 specifications as outlined in §285.91(11) of this
    (B) Loading rate. The loading rate shall not exceed
1.2 gallons per day per square foot.
    (C) Surface area. The minimum surface area shall be
calculated using the formula: Q/1.2=Surface Area (Square Feet), where
Q is the wastewater flow in gallons per day.
    (D) Thickness of sand media. There shall be a minimum
of 24 inches of sand media.
    (E) Filter bed containment. The filter bed containment
shall be an impervious lined pit or tank. Liners shall meet the specifications
detailed in §285.33(b)(2)(A) of this title (relating to Criteria
for Effluent Disposal Systems).
    (F) Underdrains. For gravity discharge of effluent
to a drainfield, there shall be a three inch layer of pea gravel over
a six inch layer of 0.75 inch gravel, that contains the underdrain
collection pipe. When pumpwells are to be used to pump the effluent
from the underdrain to the drainfield, they must be constructed of
concrete or plastic sewer pipe. The pumpwell must contain a sufficient
number of holes so that effluent can flow from the gravel void space
as rapidly as the effluent is pumped out of the pumpwell to the drainfield.
Refer to §285.90(9) of this title.
(c) Proprietary treatment systems. This subsection
does not apply to proprietary septic tanks described in subsection
(b)(1) of this section.
  (1) Tank sizing. Proprietary treatment systems that
serve single family residences, combined flows from single family
residences, or multi-unit residential developments shall be designed
using Table II in §285.91(2) of this title unless there is an
equalization tank preceding the aerobic treatment unit. If there is
an equalization tank preceding the aerobic treatment unit, the equalization
tank shall meet the requirements set forth in §285.34(b)(4) of
this title (relating to Other Requirements) and the aerobic treatment
units can be sized using the wastewater flows in Table III in §285.91(3)
of this title. Proprietary Treatment systems for non-residential facilities
shall be sized using the wastewater flows in Table III in §285.91(3)
of this title. Leak testing shall be performed in accordance with
subsection (b)(1)(H) of this section.
  (2) Installation. Proprietary treatment systems shall
be installed according to this subchapter. If the manufacturer has
installation specifications that are more stringent than given in
this subchapter, the manufacturer shall submit these specifications
to the executive director for review. If approved by the executive
director, the treatment systems may be installed according to these
more stringent specifications. Any subsequent changes to these manufacturer's
installation specifications must be approved by the executive director
before installation. Inspection, cleanout ports, or maintenance ports
shall have risers installed according to the riser installation provisions
in subsection (b)(1)(D) of this section. Tank excavations shall be
backfilled according to the backfill provisions in subsection (b)(1)(F)
of this section. At the discretion of the permitting authority, leak
testing using water filled to the inside level of the tank lid or
to the top of the riser(s) may be required.
  (3) System maintenance. Ongoing maintenance contracts
are required for all proprietary treatment systems except those systems
maintained by homeowners under the provisions of §285.7(d)(4)
of this title (relating to Maintenance Requirements). The maintenance
contract shall satisfy §285.7(d) of this title.
  (4) Electrical wiring. Electrical wiring for proprietary
systems shall be according to §285.34(c) of this title.
  (5) Approval of proprietary treatment systems. Proprietary
treatment systems must be approved by the executive director prior
to their installation and use. Approval of proprietary treatment systems
shall follow the procedures found in this section. After the effective
date of these rules, only systems tested according to subparagraph
(A) or (B) of this paragraph will be placed on the list of approved
systems. The list may be obtained from the executive director. All
systems on the list of approved systems on the effective date of these
rules shall continue to be listed subject to the retesting requirements
in paragraph (6) of this Cont'd...