13.20.510 Gravelless systems.
Gravelless drainfield pipe may be used when there are no other options and prior approval from the city is obtained, it shall:
A. Be constructed of commercially fabricated corrugated pipe completely encased by the manufacturer in a geotextile wrap specific to this purpose;
B. Be an 8-inch or 10-inch nominal ID pipe that conforms to subdivisions 1. and 2. below, and meets the requirements of American Society of Testing Materials (ASTM) F667:
1. The pipes must be marked with an alignment stripe visible through the geotextile wrap, and installed with this stripe at top center; and
2. The pipes shall contain a row or rows of cleanly cut 3/8-inch- to 1/2-inch-diameter holes located in such a manner to provide storage of solids. Each row shall contain a hole in every other corrugation valley, staggered such that every corrugation valley contains 1 hole.
C. Be wrapped in geotextile fabric specifically designed and tested for use with gravelless pipe and for installation and use in onsite wastewater systems, and designed to transmit sewage at a rate that corresponds to the sizing factor prescribed in subdivision I. below;
D. Be protected from heat and ultraviolet rays prior to installation;
E. Be excavated to a width in accordance with the manufacturer’s recommendations;
F. Have all joints secured as recommended by the manufacturer;
G. Not be loaded above the natural ground surface. The entire pipe must be below the original grade, and gravelless drainfield pipe with gravity distribution must be designed to fill the entire pipe;
H. Be backfilled so not to crush or damage the medium; and
I. Have the following size allotments:
1. An 8-inch-inside-diameter pipe shall be equivalent to a 2-foot-wide, rock-filled trench, with 6 inches of drainfield rock below the distribution pipe; and
2. A 10-inch-inside-diameter pipe shall be equivalent to a 3-foot-wide, rock-filled trench, with 6 inches of drainfield rock below the distribution pipe.