Section P3009 Subsurface Landscape Irrigation Systems
The system shall be sized in accordance with the sum of the output of all water sources connected to the subsurface irrigation system. Where gray-water collection piping is connected to subsurface landscape irrigation systems, gray-water output shall be calculated according to the gallons-per-day-per-occupant (liters per day per occupant) number based on the type of fixtures connected. The gray- water discharge shall be calculated by the following equa-tion:
A = Number of occupants:
Number of occupants shall be determined by the actual number of occupants, but not less than two occupants for one bedroom and one occupant for each additional bedroom.
B = Estimated flow demands for each occupant:
25 gallons (94.6 L) per day per occupant for showers, bathtubs and lavatories and 15 gallons (56.7 L) per day per occupant for clothes washers or laundry trays.
C = Estimated gray-water discharge based on the total number of occupants.
The surface grade of soil absorption systems shall be located at a point lower than the surface grade of any water well or reservoir on the same or adjoining lot. Where this is not possible, the site shall be located so surface water drainage from the site is not directed toward a well or reservoir. The soil absorption system shall be located with a minimum horizontal distance between various elements as indicated in Table P3009.9. Private sewage disposal systems in compacted areas, such as parking lots and driveways, are prohibited. Surface water shall be diverted away from any soil absorption site on the same or neighboring lots.
LOCATION OF SUBSURFACE IRRIGATION SYSTEM
|ELEMENT||MINIMUM HORIZONTAL DISTANCE|
|Lot line adjoining private property||5||5|
|Streams and lakes||50||50|
|Public water main||10||10|
For SI: 1 foot = 304.8 mm.
The total absorption area required shall be computed from the estimated daily gray- water discharge and the design-loading rate based on the percolation rate for the site. The required absorption area equals the estimated gray-water discharge divided by the design loading rate from Table P3009.10.1.
DESIGN LOADING RATE
|PERCOLATION RATE |
(minutes per inch)
|DESIGN LOADING FACTOR |
(gallons per square foot per day)
|0 to less than 10||1.2|
|10 to less than 30||0.8|
|30 to less than 45||0.72|
|45 to 60||0.4|
For SI: 1 minute per inch = min/25.4 mm, 1 gallon per square foot = 40.7 L/m2.
|Polyethylene (PE) plastic pipe||ASTM F405|
|Polyvinyl chloride (PVC) plastic pipe||ASTM D2729|
|Polyvinyl chloride (PVC) plastic pipe with a 3.5-inch O.D. and solid cellular core or composite wall||ASTM F1488|