Leach-Field / Trench Drainrock Volume
Washed drainrock for a septic leach field from the trench layout.
Example
You enter
- Number of trenches 3
- Trench length (ft) 60
- Trench width (in) 24
- Stone depth (in) 12
- Waste allowance (%) 10
You get
- Stone cf 360
- Drainrock volume 14.67
- Drainrock tonnage 20.5 tons
Details, formula, and sources
stone = trenches x length x width x depth / 27; tons = stone x ~1.4 ton/cy. Three 60 ft trenches, 24 in wide with 12 in of stone, is 14.7 cy (about 20 tons) at 10% waste; a deeper 18 in bed is 22 cy. The trench count, width, and stone depth come from the AHJ-approved septic design (the required length is septic-drainfield); the geotextile over the stone is taken off separately.
stone_cf = num_trenches x trench_length_ft x (trench_width_in/12) x (stone_depth_in/12); stone_cy = stone_cf / 27 x (1 + waste_pct/100); stone_tons = stone_cy x 1.4.
Leach-field drainrock identity by name (trench box volume to cubic yards with waste, then tonnage); first-principles volume arithmetic.
The volume arithmetic is public first-principles; the trench dimensions come from the AHJ-approved septic design.
Estimate. AHJ and licensed professional govern.
Field names used by the API: num_trenches, trench_length_ft, trench_width_in, stone_depth_in, waste_pct, stone_cf, stone_cy, stone_tons
- Trench dimensions count, width, and stone depth from the AHJ-approved septic designseptic design / AHJ
- Drainrock unit weight ~1.4 ton/cy for washed drainrock (3/4 to 2.5 in)aggregate supplier