708.14 Subsurface Gray Water Irrigation Systems
|C = (A × B) - D||(Equation 7-1)|
|A||=||Number of occupants:|
Residential—For dwelling units regulated by this code in accordance with Section 101.3, the 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.
Commercial—Number of occupants for buildings without dwelling units shall be determined by the International Building Code.
|B||=||Estimated flow demands for each occupant:|
Residential— For dwelling units regulated by this code in accordance with Section 101.2, 25 gallons per day (94.6 Lpd) per occupant for showers, bathtubs and lavatories and 15 gallons per day (56.7 Lpd) per occupant for clothes washers or laundry trays.
|C||=||Estimated gallons (L) of gray water discharge based on the total number of occupants.|
|D||=||Estimated gallons (L) of gray water to be used within the interior of the building.|
- Water shall be added to a point not more than 6 inches (152 mm) above the gravel or coarse sand.
- Thereupon, from a fixed reference point, water levels shall be measured at 10-minute intervals for a period of 1 hour.
- Where 6 inches (152 mm) of water seeps away in less than 10 minutes, a shorter interval between measurements shall be used, but in no case shall the water depth exceed 6 inches (152 mm). Where 6 inches (152 mm) of water seeps away in less than 2 minutes, the test shall be stopped and a rate of less than 3 minutes per inch (7.2 s/mm) shall be reported.
- The final water level drop shall be used to calculate the percolation rate.
Soils not meeting the above requirements shall be tested in accordance with Section 708.14.2.1.3.
- Any soil sloughed into the hole shall be removed and the water level shall be adjusted to 6 inches (152 mm) above the gravel or coarse sand.
- From a fixed reference point, the water level shall be measured at 30-minute intervals for a period of 4 hours, unless two successive water level drops do not vary by more than 1/16 inch (1.59 mm). Not less than three water level drops shall be observed and recorded.
- The hole shall be filled with clear water to a point not more than 6 inches (152 mm) above the gravel or coarse sand whenever it becomes nearly empty. Adjustments of the water level shall not be made during the three measurement periods except to the limits of the last measured water level drop.
- When the first 6 inches (152 mm) of water seeps away in less than 30 minutes, the time interval between measurements shall be 10 minutes and the test run for 1 hour. The water depth shall not exceed 5 inches (127 mm) at any time during the measurement period.
- The drop that occurs during the final measurement period shall be used in calculating the percolation rate.
|ELEMENT||MINIMUM HORIZONTAL |
DISTANCE (feet) TO IRRIGATION
|Lot lines other than lot lines adjoining public ways||5|
|Streams, lakes, wetlands other bodies of water||100|
|Critical root zone (CRZ) of protected trees||2|
|Public water main||10|
DESIGN LOADING RATE
|PERCOLATION RATE |
(minutes per inch)
|DESIGN LOAD FACTOR |
(gallons per square foot per day)
|Less than 10||1.2|
|10 to less than 30||0.8|
|30 to less than 45||0.72|
|45 and greater||0.4|