23.5.G Irrigation

Sprinkler irrigation systems are required for landscaped areas when natural systems are not available or are not part of a stormwater BMP. The type of plant material, the condition, and growing medium where they are installed, and sun exposure shall dictate the type of sprinkler irrigation system(s). All irrigation systems shall be designed to minimize the use of water and shall be approved as part of the landscape plan. When irrigation is installed, it shall comply with the following standards:

1. Automatic controllers shall be set to water between 7:00 p.m. and 10:00 a.m. to reduce evaporation.

2. Irrigation systems shall be designed to avoid runoff, low-head drainage, overspray, or other similar conditions where water flows or drifts onto adjacent property, non-irrigated areas, walks, roadways, or structures.

3.  Irrigation equipment shall comply with the following standards.

a. Low-volume irrigation systems with automatic controllers are required. Low-volume irrigation systems include low-volume sprinkler heads, drip emitters, and bubbler emitters.

b.  Drip, trickle or other low-volume irrigation shall be provided on at least ninety percent (90%) of the landscape areas except for those areas devoted to turf and flat groundcover plants. If a licensed landscape architect or landscape contractor verifies that a drip or trickle system is not feasible due to location, the required percentage of drip or trickle irrigation may be reduced by  technical decision of staff approving the landscape plan.

c. Integral, under-the-head, or in-line anti-drain valves shall be installed as needed to prevent low-head drainage.

d.  Automatic control systems shall be able to accommodate all aspects of the design. Automatic controllers shall be digital, have multiple programs, multiple cycles, and sensor input capabilities.

e.  Soil moisture sensors and rain or moisture-sensing override devices are mandatory.

f.  Sprinkler heads shall be selected and spaced for proper area coverage, application rate, operating pressure, and adjustment capability. Sprinklers shall have matched precipitation and application rates within each control valve circuit.

g.  Drip irrigation systems are permitted if commercial or agricultural grade materials are used. Components shall be installed below the soil except for emitters.

h.  Backflow prevention devices are required.

i. Rainwater harvesting and/or dedicated landscape water meters are recommended on all landscape areas to facilitate water management and cost reduction.