1. (a) Pipe Embedment.

   1. (1) A rigid pipe must be laid with the adequate bedding, haunching, and initial backfill to support the anticipated load. The bedding classes that are allowed are A, B, or C, as described in American Society for Testing and Materials (ASTM) C 12, American National Standards Institute (ANSI) A 106.2,Water Environment Federation Manual of Practice No. 9 or American Society of Civil Engineers (ASCE) MOP 37.
   2. (2) A flexible pipe must be laid with the adequate bedding, haunching, and initial backfill to support the anticipated load. The bedding classes that are allowed are IA, IB, II, or III, as described in ASTM D-2321 or ANSI K65.171.
   3. (3) Debris, large clods, or stones that are greater than six inches in diameter, organic matter, or other unstable materials are prohibited as bedding, haunching, or initial backfill.
   4. (4) Backfill must not disturb the alignment of a collection system pipe.
   5. (5) If trenching encounters significant fracture, fault zones, caves, or solutional modification to the rock strata, an owner must halt construction until an engineer prepares a written report detailing how construction will accommodate these site conditions.

2. (b) Compaction.

   1. (1) Compaction of an embedment envelope must meet the manufacturer's recommendations for the collection system pipe used in a project.
   2. (2) Compaction of an embedment envelope must provide the modulus of soil reaction for the bedding material necessary to ensure a wastewater collection system pipe's structural integrity as required by §217.53 of this title (relating to Pipe Design).
   3. (3) The placement of the backfill above a pipe must not affect the structural integrity of a pipe.

3. (c) Envelope Size.

   1. (1) A minimum clearance of 6.0 inches below and on each side of the bell of all pipes to the trench walls and floor is required.
   2. (2) The embedment material used for haunching and initial backfill must be installed to a minimum depth of 12 inches above the crown of a pipe.

4. (d) Trench Width.

   1. (1) The width of a trench must allow a pipe to be laid and jointed properly and must allow the backfill to be placed and compacted as needed.
   2. (2) The maximum and minimum trench width needed for safety and a pipe's structural integrity must be included in the report.
   3. (3) The width of a trench must be sufficient to properly and safely place and compact haunching materials.
   4. (4) The space between a pipe and a trench wall must be wider than the compaction equipment used in the pipe zone.
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Source Note:The provisions of this §217.54 adopted to be effective August 28, 2008, 33 TexReg 6843.