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PDFWAC 480-75-400

Backfill and bed requirements.

(1) When a pipeline company constructs a new pipeline or conducts maintenance on an existing pipeline, the backfill and bed must provide firm support for the pipeline such that neither the pipe nor the pipe coating is damaged by the backfill material or by subsequent surface activities.
(2) If the backfill material contains rocks or hard lumps that could damage the pipeline coating, the pipeline company must take care to protect the pipe and the pipe coating from damage, such as using mechanical shield material.
(3) A pipeline company's backfill practices must not cause distortion of the pipe cross-section that would be detrimental to the operation of the piping, or the passage of cleaning devices, internal inspection devices, or other similar devices.
(4) A pipeline company must apply backfill material in such a manner as to prevent excessive subsidence or erosion of the backfill and support material. Where a ditch is flooded, the pipeline company must assure that the pipe is not floated from the bottom of the ditch prior to completing the backfill.
(5) For open trench installations that cross paved areas subject to vehicular loading, the pipeline company must compact the backfill in layers to a minimum of ninety-five percent relative density.
(6) The bedding and backfill material a pipeline company uses must consist of clean sand or soil and it must not contain any stones larger than one-half inch. The pipeline company must place the bedding and backfill material at a minimum depth of six inches under the pipe and six inches over the top of the pipe. The remaining backfill must not contain rock larger than six inches. The pipeline company shall not use organic material or wood for bedding or backfill.
[Statutory Authority: RCW 80.01.040, 80.04.060, 81.88.040. WSR 08-12-045 (Docket PL-070974, General Order R-548), § 480-75-400, filed 5/30/08, effective 6/30/08. Statutory Authority: RCW 80.01.040 and 80.04.160. WSR 02-18-032 (Docket No. TO-000712, General Order No. R-500), § 480-75-400, filed 8/26/02, effective 9/26/02.]
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