Current through Register Vol. 39, No. 6, September 16, 2024
When designing an irrigation system, an irrigation contractor
shall:
(1) Design the layout of heads
and other emission devices to reduce evaporation loss, reduce surface run-off,
and limit overspray across or onto a street, public driveway or sidewalk,
parking area, building, fence, or adjoining property.
(2) Design sprinkler head spacing with an
approximate "head-to-head" coverage.
(3) Use separate stations or zones for areas
with dissimilar environmental conditions or dissimilar water or scheduling
requirements (hydrozones). These conditions or requirements include sun
exposure, plant type, soil type, varying wind conditions, grades, and
dimensional issues. When not practicable due to accessibility, dimensional
issues, or other constraints, practical modifications to this standard may be
acceptable.
(4) When selecting
system components:
(a) select components to
avoid surface runoff;
(b) select
components to keep the sprinkler precipitation rate below the infiltration rate
of the soil;
(c) specify the use of
repeat cycles to allow the water to soak into the root zone; and
(d) specify stations or zones for sprinklers
at the top and toe of sloped areas.
(5) Place sprinkler heads based on an
evaluation of physical, environmental, and hydraulic site conditions, including
typical wind conditions during the normal irrigation period.
(6) Select sprinkler heads and nozzles to
achieve an approximate matched precipitation rate within each zone.
(7) Plan to use the following water
conserving equipment:
(a) check valves to
minimize low-head drainage when grades exceed five percent;
(b) pressure regulators or pressure
compensating devices when pressures exceed manufacturer's
recommendations;
(c) rain sensors
to suspend irrigation during rain or other forms of precipitation;
(d) a controller that has multi-program
capability with at least four start times (for multiple repeat soak cycles) and
run time adjustments in one-minute increments;
(e) low-trajectory sprinkler nozzles and
modified head spacings to mitigate the effects of wind; and
(f) components that do not mist when
manufacturer's pressure specifications are met.
(8) Offset turf grass sprinklers a minimum of
two inches from pavement edges to allow for edging of the turf.
(9) Offset sprinklers from vertical walls to
limit spray on the walls.
(10)
Ensure that valves are located so as to allow reasonable access for maintenance
or service.
(11) Ensure that the
roots of existing trees are protected by:
(a)
Planning pipe system layout to limit its effect on existing trees and other
planting.
(b) When necessary to
trench into the root zone of an established plant in order to provide
irrigation within the root zone:
(i) planning
to dig the trench so as to minimize the effect on the roots (for example, by
digging the trench in a straight line towards the base of the tree or shrub
such that, if the line of the trench were extended, it would intersect with the
base of the tree or shrub); or
(ii)
planning to use direct boring or hand-trenching. An irrigation contractor shall
use hand-trenching techniques that dig a trench without damaging roots having a
diameter of one-half inch or more.
(c) In the event of trenching, maintaining a
distance of one foot from the tree trunk for every inch of tree diameter at a
height of four feet six inches above the ground. For example, piping shall be
kept at least 20 feet away from the trunk of a tree having a 20 inch diameter
at four feet six inches above the ground.
(d) In the event of boring, maintaining a
distance of at least one-half foot from the tree trunk for each inch of tree
diameter at a height of four feet six inches above the ground and, in any
event, maintaining a distance of at least five feet from the tree trunk. When
direct boring, an irrigation contractor shall bore to a minimum of 36
inches.
(e) Avoiding placing
sprinklers in a position to directly spray water on tree trunks of mature trees
by placing them no closer to a tree than one-third of the sprinkler spray
radius.
(12) With
respect to wiring:
(a) install control wires
in the same trench along the side of the main line piping;
(b) allow slack in the wiring;
(c) bundle an expansion coil for all wires at
each valve location;
(d) use the
appropriate size American Wire Gauge ("AWG") wire, as noted by the
manufacturer, to operate a valve;
(e) indicate common wiring (wire that runs
through the entire circuit of valves) by using a different colored wire from
all other wire connections;
(f)
provide additional wire along the irrigation wire path for future expansion or
replacement of damaged wires;
(g)
design irrigation systems with control wire splices made with a waterproof wire
splice kit that is UL listed for underground applications. For two-wire control
systems, the design shall specify the manufacturer's recommended splice kits;
and
(h) follow the manufacturer's
recommendation for all wiring and grounding, including two-wire control
systems.
(13) Use valve
boxes that are large enough to provide sufficient space for servicing the valve
housed inside. For single valve boxes, valve boxes shall be at least 10 inches
in diameter for both manual and automatic valves.
Authority
G.S.
89G-5;
Eff. August 1,
2011;
Readopted Eff. January 1, 2016;
Amended Eff.
November 1, 2016.
