Section 49(7) in Assam Notified Urban Areas (Other than Guwahati) Building Rules, 2014
(7)When the disposal of septic tank effluent is to seepage pit, may be of any suitable shape with the least cross- sectional dimension of 90 cm and not less than 100 cm in depth below the invert level of the inlet pipe . The pit may be filled with stone, brick or concrete blocks with dry open joins, which should be backed with at least 7.5 cm of clean coarse aggregate. The lining above the inlet level should be finished with mortar. In the case of pits of large dimensions, the top portion may be narrowed to reduce the size of the RCC cover slab, where no lining is used, specially near trees, the entire pit should be filled with loose stones. A masonry ring may be constructed at the top of the pit to prevent damage by flooding of the pit by surface run off. The inlet pipe may be taken down a depth of 90 cm from the top as an anti mosquito measure.
