g) Subsurface Drip Irrigation
Systems. Subsurface drip irrigation systems shall be designed, installed and
maintained in accordance with the following:
1) The drip irrigation system shall be
designed, installed and operated as a subsurface seepage system, and no portion
of the drip irrigation system shall have a surface discharge.
A) Pre-treatment
i) The drip irrigation system shall be
preceded by a pre-treatment process designed to reduce the
CBOD5 (carbonaceous 5-day biochemical oxygen demand) to
a maximum concentration of 25 mg/L and total suspended solids to a maximum
concentration of 30 mg/L. Drip irrigation systems shall not be installed
following a septic tank without any pre-treatment process capable of meeting
this Part's requirements.
ii) The
total flow from the property plus the backwash water from the drip irrigation
system shall not exceed the treatment capacity of the pre-treatment
device.
iii) The installation
contractor, designer or homeowner, in consultation with the manufacturer or the
manufacturer's representative, shall assure that the pre-treatment process
meets the requirements of this Part.
B) Dosing Tank
i) A minimum liquid capacity of 1,000 gallons
shall be provided below the inlet in the dosing tank for a residential or
non-residential site.
ii) For homes
larger than three bedrooms and non-residential systems with a daily design flow
greater than 667 gallons/day, a dosing tank with a minimum capacity of
1.5 days design flow shall
be provided.
C) Dosing
Pump
i) A high head/low volume pump shall be
used.
ii) The pump shall be sized
based upon the design flow rate of the drip irrigation field, which shall be
based on the number of emitters times the flow rate of each emitter in gallons
per minute.
iii) The minimum head
requirement of the pump shall be based upon the pressure requirements for the
operation and flushing of the drip field plus the total static and friction
head requirements of the supply lines and manifolds.
iv) Pump specifications used for drip
irrigation systems shall be provided by the pump manufacturer.
v) The installation contractor, designer or
homeowner, in consultation with the manufacturer or the manufacturer's
representative, shall assure that the pump used is in compliance with this
Part.
D) Time Dosing
i) Drip irrigation systems shall be provided
with a timer to activate the dosing pump equally throughout a 24-hour
period.
ii) Systems shall be dosed
a minimum of 6 equal doses over a 24-hour period and shall be capable of
delivering the maximum daily design flow to the drip irrigation system in a
24-hour period. More frequent doses of 8 to 24 equal doses over a 24-hour
period are recommended and shall be required in soils that have a loading rate
of less than 0.5 gallons/square foot/day.
iii) The dosing frequency shall be such that
the soil surrounding the drip irrigation system does not become
saturated.
iv) The dosing
specifications shall be provided by the drip irrigation manufacturer or the
manufacturer's representative in accordance with this Part.
E) Effluent Filtration
i) Wastewater effluent shall be filtered to
the drip tubing manufacturer's specifications to ensure proper operation of the
distribution system.
ii) The
effluent filtration device shall be easily accessible for maintenance and
inspection.
F) Drip
Distribution System
i) The drip distribution
tubing manufacturer or the manufacturer's representative shall provide written
specifications for all components used in conjunction with the drip irrigation
system.
ii) The manufacturer or the
manufacturer's representative shall assure that all manufacturer specifications
for the drip irrigation system are in compliance with this Part.
iii) The manufacturer shall incorporate
measures to prevent root intrusion into the emitters.
G) Drip Emitters and Flow Rates
i) The manufacturer of the drip tubing shall
specify the number of drip emitters per lineal foot and the flow rates through
each emitter for different pressures.
ii) The installation contractor or homeowner,
in consultation with the manufacturer or the manufacturer's representative,
shall assure that the number of emitters to be used in a drip irrigation system
and the types of emitters used, flows and flow rates into the soil comply with
all of the manufacturer's specifications and requirements and with this
Part.
H) Absorption
Field Sizing
i) A soil investigation shall be
conducted in accordance with Section
905.55(a).
ii) The soil loading rate (gallons/square
foot/day) shall be based upon the least permeable soil condition encountered
within 24 inches below the proposed depth of the drip irrigation
tubing.
iii) The system size shall
be based upon Appendix A, Illustration M, Exhibits A and B.
I) Drip Tubing Installation and
Configuration
i) The drip tubing shall be
installed in the natural soil using installation equipment and procedures
specified by the manufacturer.
ii)
Drip irrigation tubing shall be installed at a depth of 6 inches to 12 inches
below the final graded surface.
iii) Drip irrigation tubing shall be
installed on a minimum of 2-foot centers.
iv) When the drip irrigation piping is
installed on slopes exceeding 20%, the spacing between the drip irrigation
piping shall be 3 feet or greater.
v) The drip irrigation system shall be
configured so that the length of the area of the drip irrigation tubing system
is at least two times its width. If this is not possible, the drip irrigation
tubing trench separation distance shall be doubled.
vi) The length of individual drip
distribution tubing shall not exceed the manufacturer's specifications and
shall be installed at a uniform depth that follows the contour of the
site.
vii) The drip irrigation
tubing shall be installed a minimum of 12 inches above a limiting
layer.
J) Considerations
to Prevent Freezing
i) The distribution and
return manifolds shall be installed to drain back to the pre-treatment tank
after the field has been dosed.
ii)
If the elevations of the pre-treatment tank and dosing tank do not allow
gravity flow to the pre-treatment tank, the lines shall be installed to drain
back to the dosing tank.
iii) All
piping and components shall be installed to allow water to drain back to the
pre-treatment tank or dosing tank.
iv) To allow for drain back, a check valve
shall not be installed in the supply and return lines.
K) Fill Soils
Fill soils may be used in accordance with subsection (a),
except that the soil surface shall not be plowed.
L) Pressure Requirements
i) The manufacturer of the drip tubing shall
specify the operating pressure requirements of the drip irrigation system and
provide the specifications of any pressure regulator that may be required with
the drip irrigation system.
ii) A
pressure gauge shall be provided or a method of connecting a pressure gauge
shall be provided on the distal end of the drip irrigation system to ensure
that field pressure can be checked during inspection, evaluation and
maintenance. The installation contractor or manufacturer shall ensure that the
irrigation system is operating at the required specifications.
M) Flush Valves
i) An automatic or manual flush valve shall
be provided on the filter and drip distribution system to allow for periodic
flushing of both the drip distribution system and the filter.
ii) The drip distribution system manufacturer
shall provide the specifications for the flush valves that are acceptable to
use with the system. The manufacturer shall also provide specifications on the
number of flush valves to be used and their location, with specifications about
how this is to be determined and the backwash velocity required to clean the
drip tubing piping.
iii) A chemical
injection port shall be installed to facilitate cleaning and flushing the drip
distribution system.
iv) Backwash
water shall be directed into the building sewer at the inlet end of the
pre-treatment system.
N)
Air Relief
i) The manufacturer of the drip
tubing shall specify the air relief requirements of the drip distribution
system and provide the specifications of any air relief devices that may be
required with the drip irrigation system to ensure that the distribution piping
can drain back to the dosing chamber when the system is not
pressurized.
ii) The air relief
device shall be installed at the highest point of the feed and return
manifolds.
O) Alarm
i) An audible and visual alarm shall be
provided to warn of a high water condition in the dosing tank.
ii) The alarm shall be on a separate
dedicated circuit.
iii) The alarm
control device shall be a sealed float or diaphragm switch and shall be located
to activate 2 to 3 inches above the pump turn-on level or siphon activation
level.
iv) The alarm shall be
located outside of the structure served by the system and shall be provided
with an electrical disconnect that is located within sight of and not more than
50 feet away from the device.
v) If
an alarm is being used by another component within the private sewage disposal
system, is compliant with subsections (g)(1)(O)(i) through (iv), and is able to
connect additional devices, it may be used without the need for an additional
alarm.
P) Access
i) Access openings to the pre-treatment
system, effluent filtration system, and dosing tanks shall have a minimum
inside dimension of 18 inches, shall be watertight and shall extend to 3 inches
or more above the ground surface.
ii) Access openings to all other system
components shall be large enough to allow easy access from the ground
surface.
Q) Maintenance
i) The manufacturer shall provide
specifications for the maintenance of all components within the drip irrigation
system.
ii) The manufacturer shall
provide a maintenance plan to ensure that maintenance is conducted as required
to achieve the proper function of the system.
2) The installation contractor or
manufacturer shall provide the following information to the owner of the
system:
A) An operation manual;
B) The maintenance plan for the drip
irrigation system;
C) The
manufacturer of the components and a description of the function of the
components;
D) The service contract
information;
E) A troubleshooting
repair guide;
F) A list of safety
concerns;
G) Manufacturer's cut
sheets for all electrical and mechanical components; and
H) An as-built drawing of the
system.