7.4　Pipeline As-built Survey

7.4.1　Pipeline as-built survey shall be made for above ground/underground pipelines in new construction，reconstruction and extension projects，and as-built documents including pipelines coordination as-built diagrams and pipelines coordination as-built deliverables shall be compiled.The as-built survey for pipeline shall use digital mapping method，and the compilation of pipelines coordination as-built diagrams and pipelines coordination as-built deliverables shall comply with requirements in Chapter 10 of this Code.

7.4.2　Before earth coverage for all types of underground pipelines of direct burial or in pipe trench，pipeline as-built survey shall be made.When that survey cannot be done before earth coverage，pending points for pipeline shall be set up with their positions led to the ground accurately，and the description of station shall be kept，and pipeline as-built survey shall be done after earth coverage according to the specifications in Article 3.0.21 and 3.0.22 of this Code.

7.4.3　In as-built field survey for underground pipelines，the spatial data of pipeline points shall be measured，the attribute data of the pipeline points shall be investigated on site according to the specifications in Section 8.2 of this Code and in combination with construction diagram.The pipelines coordination as-built deliverables shall be filled item by item according to results of investigation according to the specifications in Table E.0.1 in Appendix E of this Code.The contents of pipelines coordination as-built deliverables should be compiled according to Table D in Appendix D of this Code.

7.4.4　The pipeline attribute data and spatial data gathered in underground pipeline as-built survey shall comply with the specifications in Article 11.3.3 of this Code.

7.4.5　The pipeline as-built survey shall include control survey，pipeline point connection survey，section survey and topographic survey between pipeline and the BL of process unit，utilities，storage &transportation facilities or adjacent first row of architecture/structure，facilities.

7.4.6　Pipeline as-built survey shall conduct control survey according to the technical specifications in Section 9.2 of this Code，or the control points of the original setting-out survey may be used.

7.4.7　For pipelines laid on the ground and the pipelines on sleeper and pipe rack，the plane position，ground elevation and the width of pipe sleeper of pipeline laid on the ground，pipe sleeper or pipe rack footing shall be actually measured.

7.4.8　When overhead pipeline crosses the road，railroad，architecture/structure，the elevation of the road surface，top of railroad，top of the architecture/structure at the crossing point and the elevation at the lowest point of pipe rack clearance shall be actually measured.

7.4.9　For overhead electric power cable，the height，plane position of electric pole（tower）and the ground elevation of the corresponding point shall be actually measured，and the voltage class shall be specified in the as-built diagram.

7.4.10　The as-built survey for pipe trench and protection pipe or conduit for underground pipelines or cable/optical cable laying shall comply with the specifications in Article 8.2.6，8.2.7 and 8.2.8 of this Code.The underground pipeline in road-crossing protection conduit，pipe trench or pipe-jacking construction site shall be measured for the elevation of its external bottom.

7.4.11　The as-built survey for pipeline branch points，crossing points and different wells shall meet the following requirements:

1　For pipeline points including pipeline branch points and crossing points，all the pipeline center coordinates，and the burial depth and elevation of the pipeline orifice center or internal bottom shall be measured respectively.

2　For wells，the pipeline center coordinates，burial depth of the pipeline orifice/internal bottom against the edge of well，elevation of the pipeline orifice center/internal bottom for all the pipelines in the well shall be surveyed/mapped，and the coordinates of the well cover center and elevation of the well edge shall be measured.In case of elevation difference between the well edge and the ground near the well，the elevations of the well edge and the ground near the well shall be measured at the same time.

3　For the pipeline section under the control of valves，instruments and water meter in the well，the attribute data of all the branch pipelines shall be found out，and the record shall be kept.

7.4.12　The technical specifications for coordinate and elevation survey for underground pipeline points shall comply with the specifications in Section 9.3 of this Code.

7.4.13　The plane position of underground pipeline points should be measured by using total station instrument with polar coordinates method or GPS-RTK technology method.Leveling survey should be used for measuring the elevation of pipeline points，or the EDM trigonometric leveling survey may be used.The survey accuracy shall comply with the specifications in Article 3.0.22 of this Code.

7.4.14　The topography and ground objects surveyed/mapped along both sides of the pipeline include:side line of road，railroad and rainwater trench and contour line of architecture/structure and facility.The structure，level and name shall be specified，and the ground position and elevation of all types of feature points on ground surface shall be measured.

7.4.15　Cross-section survey should be done at pipe trench or main road crossings where pipelines are centralized，and the cross-section survey shall include the following:

1　Cross-section size and elevation of road，railroad，pipe sleeper，pipe rack，pipe trench and rainwater trench.

2　Coordinate and elevation of pipeline point.

3　Change in ground elevation.

4　Elevation of the feature point of road.

5　The contour line of architecture/structure and facilities at both sides，and the BLs of process unit，utilities and storage & transportation facilities.