§ 15.11.980. Irrigation design plan criteria - System requirements.

For the efficient use of water, an irrigation design plan meeting the following design criteria for irrigation systems shall be included in the irrigation design plan and submitted as part of the landscape documentation package for any project that has a landscape area greater than two thousand five hundred square feet or that uses the water budget calculation option:

A.

Relevant information from the soil management plan, such as soil type and infiltration rate, shall be utilized when designing irrigation systems.

B.

All irrigation systems shall be designed to avoid run-off, low head drainage, overspray and other similar conditions where water flows onto adjacent property, non-irrigated areas, walks, roadways or structures.

C.

The design of the irrigation system shall conform to the hydrozones of the landscape design plan.

D.

Irrigation systems shall be designed, installed, and maintained to meet, at a minimum, an irrigation efficiency of 0.75 for overhead spray devices and 0.81 for drip system devices.

E.

All landscape areas in excess of ten thousand square feet shall be designed to allow for the current and future use of recycled water except as follows:

1.

Landscape areas in excess of ten thousand square feet do not have to be designed to allow for the current and future use of recycled water where the director grants an exemption to the requirement set forth in Subsection E of this section on the basis that recycled water is not available, and will not be available in the foreseeable future to serve the landscape project.

F.

In mulched planting areas, the use of low volume irrigation is required to maximize water infiltration into the root zone.

G.

Sprinkler heads and other emission devices shall have matched precipitation rates, unless otherwise directed by the manufacturer's recommendations.

H.

Head to head coverage is required at a minimum, with consideration for average wind conditions. However, sprinkler spacing shall be designed to achieve the highest possible distribution using the manufacturer's recommendations.

I.

Areas less than ten feet in width in any direction shall be irrigated with subsurface irrigation or other means that produces no runoff or overspray.

J.

Overhead sprinkler irrigation systems shall not be permitted within twenty-four inches of any non-permeable surface. Allowable irrigation within the setback from non-permeable surfaces may include drip irrigation, or other low volume irrigation technology. The setback area may be planted or unplanted. The surfacing of the setback may be mulch, gravel, or other porous material. These restrictions may be modified if:

1.

The adjacent non-permeable surfaces are designed and constructed to drain entirely to landscaping;

2.

The landscape area is adjacent to permeable surfacing and no runoff occurs; or

3.

The certified irrigation designer specifies an alternative design or technology, as part of the landscape documentation package and clearly demonstrates strict adherence to irrigation system design criteria in this section. Prevention of overspray and runoff must be confirmed during the irrigation audit required by Section 15.11.1040.

K.

Slopes greater than twenty-five percent shall not be irrigated with an irrigation system with an application rate exceeding 0.75 inches per hour. This restriction may be modified if the certified landscape designer specifies an alternative design or technology, as part of the landscape documentation package, and clearly demonstrates no runoff or erosion will occur. Prevention of runoff and erosion must be confirmed during the irrigation audit required by Section 15.11.1040.

L.

Each valve shall irrigate a hydrozone with similar site, slope, sun exposure, soil conditions, and plant materials with similar water use.

M.

Sprinkler heads and other emission devices shall be selected based on what is appropriate for the plant type within that hydrozone.

N.

Trees shall be placed on separate valves from shrubs, groundcovers, and turf, where feasible.

O.

Individual hydrozones that mix plants of moderate and low water use, or moderate and high water use, may be allowed if:

1.

The plant factor calculation is based on the proportions of the respective plant water uses and their plant factor; or

2.

The plant factor of the higher water using plant is used for calculations.

P.

Individual hydrozones that mix high and low water use plants shall not be permitted.

Q.

On the landscape design plan and irrigation design plan, hydrozone areas shall be designated by number, letter, or other designation. On the irrigation design plan, the areas irrigated by each valve shall be designated and a number assigned to each valve.

R.

If the water pressure is below or exceeds the recommended pressure for the specified irrigation devices, the installation of a pressure regulating device is required to ensure that the dynamic pressure at each emission device is within the manufacturer's recommended pressure range for optimal performance.

1.

If the static water pressure is above or below the required dynamic pressure of the irrigation system, pressure-regulating devices such as inline pressure regulators, booster pumps, or other devices shall be installed to meet the required dynamic pressure of the irrigation system.

2.

Static water pressure, dynamic or operating pressure, and flow reading of the water supply shall be measured at the point of connection. These pressure and flow measurements shall be conducted at the design stage. If the measurements are not available at the design stage, the measurements shall be conducted at installation.

(Ords. 29243, 29671.)