(A) Backfill materials.
(1) Granular material, where required, shall comply with Art. 211.02 of the INDOT Standard Specifications. Maximum stone size shall not exceed one inch or the maximum size recommended by the pipe manufacturer, whichever is smaller.
(2) Backfill and bedding for trenches shall consist of the various materials classified below as specified herein:
(a) Class I: angular, one-fourth- to one-half-inch graded stone such as crushed stone or #9 coarse aggregate as defined by Art. 904.02 of the INDOT Standard Specifications;
(b) Class II: coarse sands and gravel with maximum particle size of one and one-half inches, including various grades of seeds and gravel containing small percentages of fines, generally granular and non-cohesive, either wet or dry. Soil types GW, GP, SW and SP are included in this classification;
(c) Class III: fine sand and clay gravel including fine sands, sand-clay mixtures and gravel-clay mixtures. Soil types GM, GC, SM and SC are included in this class; and
(d) Class IV: silt, silty clays and clays, including inorganic clays and wilts of medium to high plasticity and liquid limits. Soil types MH, ML, CH and CL are included in this class.
(3) Crushed stone material shall be No. 53 complying with Art. 904,02 of the INDOT Standard Specifications.
(B) Pipe materials. For the purpose of these specification and as shown on the plans, RIGID PIPES AND CONDUITS shall include those made of steel, ductile iron, cast iron, concrete and vitrified clay. Flexible and semi-rigid conduits and pipes shall include those made of PVC, FRP, polyethlyne and other materials as determined by the Engineer.
(2004 Code, Art. I, § B, part 2)