ss-c104 stormwater drainage

Asset Management SS-C104 – Stormwater Drainage

RTIO-AM-0017821 Printed copies are Uncontrolled

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© 2010, Held within Rio Tinto Internal Use Only

Last Reviewed: 16 March 2010

Document Attributes As a Standard Specification, this document has the following attributes (refer to RTIO-IT-0002760 for document type definitions):

Authoriser: Superintendent

Reviewer: Supervisor

Document Controller: Department Coordinator

Audience: Department

Document Type: Specification

References Reference No. FDMS Reference Title

1 RTIO-IT-0002760 Document Management Standards and Guidelines



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Contents

Section 1 - Scope..............................................................................................................................................5

Section 2 - Applicable Documents .................................................................................................................6

2.1 Rio Tinto Standard Specifications ............................................................................................................6

2.2 Australian Standards ................................................................................................................................6

Section 3 - Materials.........................................................................................................................................7

3.1 Precast Reinforced Concrete Pipes .........................................................................................................7

3.2 Box Culverts .............................................................................................................................................7

3.3 Corrugated Steel drainage Pipes .............................................................................................................7

3.4 Helically Corrugated Lock Seam Pipe......................................................................................................7

Section 4 - Setting Out.....................................................................................................................................8

Section 5 - Clearing and Grubbing .................................................................................................................9

5.1 Trees, Scrub and Roots ...........................................................................................................................9

5.2 Clearing Limits..........................................................................................................................................9

Section 6 - Existing Services and Facilities ................................................................................................10

6.1 Reinstating Fences, Structures, Grassed Areas and Pavements..........................................................10

6.2 Roadways...............................................................................................................................................10

6.3 Drains .....................................................................................................................................................10

Section 7 - Notice for Inspection ..................................................................................................................11

Section 8 - Excavation of Trenches..............................................................................................................12

8.1 Excavation Requirements ......................................................................................................................12

8.2 Dimensions.............................................................................................................................................12

8.3 Subsidence.............................................................................................................................................12

8.4 Excavation in Rock.................................................................................................................................12

8.5 Use of Explosives...................................................................................................................................12

8.6 Unlined Drainage Channels ...................................................................................................................12

8.7 Spoil Material..........................................................................................................................................12

Section 9 - Diverting Water and Dewatering................................................................................................13

9.1 Contractor Requirements .......................................................................................................................13

9.2 Ponding ..................................................................................................................................................13

9.3 Dewatering and Disposal .......................................................................................................................13

Section 10 - Inspection..................................................................................................................................14

10.1 Inspection and Approval.........................................................................................................................14

10.2 RC Pipes and Box Culvert Damage.......................................................................................................14



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10.3 Pipes.......................................................................................................................................................14

Section 11 - Bedding .....................................................................................................................................15

11.1 Material...................................................................................................................................................15

11.2 Compaction ............................................................................................................................................15

11.3 Pipes.......................................................................................................................................................15

11.4 RC Pipes ................................................................................................................................................15

Section 12 - Laying and Jointing..................................................................................................................16

12.1 RC Pipes ................................................................................................................................................16

12.2 Manufacture of Circular Pipes................................................................................................................16

12.3 RC Box Culvert.......................................................................................................................................16

12.4 Cement Mortar........................................................................................................................................16

12.5 Corrugated Steel Pipe ............................................................................................................................16

12.6 Pipe Invert Levels...................................................................................................................................16

Section 13 - Backfilling..................................................................................................................................17

13.1 Trenches.................................................................................................................................................17

13.2 Excavated Material .................................................................................................................................17

Section 14 - Rip-Rap......................................................................................................................................18

14.1 Location and Thickness..........................................................................................................................18

14.2 Placing and Dumping .............................................................................................................................18

14.3 Rip-rap Sizes ..........................................................................................................................................18

14.4 Areas of Use...........................................................................................................................................18

14.5 Dumped Rip-rap .....................................................................................................................................18

14.6 Segregation Prevention..........................................................................................................................19

Section 15 - Drainage Pits Headwalls and Inlets ........................................................................................20

15.1 Construction Requirements....................................................................................................................20

15.2 Inlet Pipes...............................................................................................................................................20

15.3 Lids, Covers and Gratings......................................................................................................................20



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Section 1 - Scope This Specification applies to Iron Ore Operations in the Pilbara operating under the Rio Tinto (RT) banner, including Pilbara Iron, Hamersley Iron, Robe River Mining and Hamersley HMS.

It specifies the technical requirements for the construction of stormwater drainage facilities, including the excavation, bedding, laying and jointing of reinforced concrete drainage pipes, box culverts and corrugated steel drainage pipes. It includes the construction of drainage pits, headwalls, inlet and outlet structures, placement of rip-rap and associated works.



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Section 2 - Applicable Documents The applicable documents for this Standard Specification are listed below.

2.1 Rio Tinto Standard Specifications

Specification No. Title

SS-C101 Earthworks

SS-C107 Concrete Supply

SS-C120 Bedding for Services

2.2 Australian Standards

Standard No. Title

AS 1554 Structural Steel Welding Set

AS 1597.2 Precast Reinforced Concrete Box Culverts-Large Culverts

AS 1646 Elastomeric Seals for Waterworks Purposes

AS 1761 Helical Lock-Seam Corrugated Steel Pipes

AS 1762 Helical Lock-Seam Corrugated Steel Pipes - Design and Installation

AS 2041 Buried Corrugated Metal Structures

AS 3725 Design for Installation of Buried Concrete Pipes

AS 4058 Precast Concrete Pipes (Pressure and Non-Pressure)



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Section 3 - Materials 3.1 Precast Reinforced Concrete Pipes

Precast reinforced concrete (RC) pipes shall be of the various classes as shown on the Drawings or as specified in the Contract Specifications and shall conform in all respects to the relevant Standard specified in Section 2 of this Specification. Spigot and socket joints shall be used for pipes up to and including 600mm diameter and rebated joints for pipes greater than 600mm.

3.2 Box Culverts

Box culverts shall be precast, reinforced concrete, inverted U-type in accordance with the relevant Standard specified in Section 2 of this Specification. Internal dimensions shall be as shown on the Drawings and shall be supplied in 1200mm lengths with plain butt joint ends.

3.3 Corrugated Steel Drainage Pipes

Corrugated steel drainage pipes shall be in accordance with the relevant Standards specified in Section 2 of this Specification and shall be supplied with a hot-dip galvanised finish including all fittings and couplings.

3.4 Helically Corrugated Lock Seam Pipe

Helically corrugated lock seam pipe shall have a continuous folded lock-seam extending from end to end of each length of pipe section. Folded lock-seam shall be formed with sufficient pressure to prevent any seam slippage that would seriously effect the load carrying capacity of the pipe, but without damaging the metal to such an extent that a plane of weakness is created.

The metal used in fabricating helically corrugated lock seam pipe shall be selected to permit cold forming without damage.



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Section 4 - Setting Out Setting out shall be in accordance with the General Conditions for Construction Contracts. Before any peg is disturbed the Contractor shall transfer its position and level to an offset peg at a convenient distance clear of the work and the Contractor shall keep available a complete list of such transfers of position and levels. Offset pegs shall be left intact until the completion of the Contract.



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Section 5 - Clearing and Grubbing 5.1 Trees, Scrub and Roots

All trees, scrub, and roots shall be removed and disposed of as specified in RT Standard Specification SS-C101.

5.2 Clearing Limits

The Contractor shall ensure that no clearing is undertaken outside the limit of the works unless authorised in writing by the RT Company Representative.



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Section 6 - Existing Services and Facilities 6.1 Reinstating Fences, Structures, Grassed Areas and Pavements

The Contractor shall reinstate fences, structures, grassed areas, and pavements to the same condition as before commencement of the works.

6.2 Roadways

The Contractor shall leave all roadways in the same condition as before the commencement of the work. The contractor shall replace and compact all fine crushed rock or gravel, disturbed in the conduct of these works to the satisfaction of the RT Company Representative

6.3 Drains

The Contractor shall connect existing drains to new work where directed by the RT Company Representative . Any existing road culverts, pipe drains, etc. which are interfered with or replaced by these works shall be removed. Timber, pipes etc. from such existing culverts and pipe drains, shall remain the property of the company and the cost of removal of such shall be included in the work.



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Section 7 - Notice for Inspection The Contractor shall give 24 hours’ notice to the RT Company Representative in the following activities:

a) Placing of concrete in drainage pits or other major drainage structure; and

b) Backfilling over any drainage pipe. Any work carried out without the prior approval of the RT Company Representative shall be liable to rejection.



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Section 8 - Excavation of Trenches 8.1 Excavation Requirements

All excavation for pipe trenches and drainage pits etc. shall comply with the relevant requirements of RT Standard Specification SS-C101.

8.2 Dimensions

Trenches shall be excavated to the widths and depths shown on the Drawings. Trench widths shown on the Drawings shall not be modified without written approval of the RT Company Representative

8.3 Subsidence

In the event of any subsidence of trench walls, the RT Company Representative may direct the Contractor to lay higher strength pipes or perform extra works to improve the load bearing capability of the pipe, bedding or surround. The cost of such works shall be borne by the Contractor.

Excavation of drainage pits etc. shall be taken out only to dimensions necessary for construction of these structures to the details shown on the Drawings.

8.4 Excavation in Rock

Unless provision is made in Contract Schedules for payment for excavation in rock, no additional payment will be made. For excavation, rock shall be as defined in RT Standard Specification SS-C101.

8.5 Use of Explosives

The use of explosives if required shall be in accordance with the General conditions for Construction Contracts and RT Standard Specification SS-C101. Explosives shall not be transported after sunset or before sunrise.

The Contractor when using explosives in the vicinity of roads accommodation facilities or buildings or in any area where flying stones or other material may possibly cause damage to persons, animals or property, shall use approved blasting mats or other approved covering material.

8.6 Unlined Drainage Channels

Unlined drainage channels shall be constructed to the lines, levels and grades as shown on the Drawings. After completion of the excavation forming the drainage channel, all batters, inverts and embankments shall be uniformly graded to conform with profiles given.

8.7 Spoil Material

Spoil material excavated from trenches and open drains shall be removed and dumped in a disposal area nominated by the RT Company Representative within 5km of the site of the works.



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Section 9 - Diverting Water and Dewatering 9.1 Contractor Requirements

The Contractor shall do all things necessary to divert any water interfering with the progress of the Works, keep the trenches and excavations free from water while the Works are in progress and prevent any damage to the Works by water due to floods or other causes.

9.2 Ponding

Should ponding of water occur on the work site through the Contractor's negligence or inadequate sequencing or protection of the Works and if in the opinion of the RT Company Representative such ponding and/or water saturation of the strata may have caused softening, loss of bearing strength, heave or settlement of any other effect of a detrimental nature, then the Contractor shall, at his cost, excavate and remove the suspect strata and immediately replace, compact and trim same to level to the satisfaction of the RT Company Representative by using such material as the RT Company Representative may direct.

The Contractor shall have proper pumping equipment approved by the RT Company Representative for keeping the trenches and excavation constantly dewatered during the time the Works are in progress.

9.3 Dewatering and Disposal

The dewatering method and disposal arrangements shall not cause damage to or have any detrimental effect on adjacent structures, services or adjoining land. All damage caused by the disposal of water shall be made good at the Contractor's cost. Water shall not be discharged or conveyed onto the land or into any stormwater drain without the RT Company Representative’s permission.



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Section 10 - Inspection 10.1 Inspection and Approval

All materials, processes and finished pipe shall, before acceptance, be subject to inspection and approval by the RT Company Representative. Finished pipe shall be subject to inspection at the point of delivery, and any pipes that, independent of physical tests herein specified, fail to meet the requirements of the relevant Standards specified in Section 2 of this Specification may be rejected.

10.2 RC Pipes and Box Culvert Damage

RC pipes and box culverts damaged as an apparent result of handling and cracked in one or more places so as to show clearly visible cracks, as defined in the relevant Standards, inside or outside, shall be rejected.

10.3 Pipes

Corrugated steel pipes, pipe arches, bent, distorted, badly marked or with surface damage or not complying with the requirements of the relevant Standards, shall be rejected.



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Section 11 - Bedding 11.1 Material

Material for bedding pipe culverts shall be select material composed of clean durable sand, or approved granular material, in accordance with RT Standard Specification SS-C120.

11.2 Compaction

Compaction of bedding material shall comply with the Manufacturer's recommendations. However, in all circumstances bedding material shall be compacted to 95% modified dry density as determined by the relevant Standard specified in Section 2 of this Specification.

11.3 Pipes

Pipes shall be bedded with selected bedding material as defined in RT Standard Specification SS-C104 and in conformity with the sections shown on the relevant Standard Drawings.

11.4 RC Pipes

RC pipes shall be bedded on their barrels clear of sockets, true to line and grade with the sockets upstream.



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Section 12 - Laying and Jointing 12.1 RC Pipes

RC pipes shall be laid in accordance with the recommended pipe laying practice as set out in the relevant Standard specified in Section 2 of this Specification and in accordance with the Manufacturer's recommendations.

12.2 Manufacture of Circular Pipes

In manufacturing circular pipe with elliptical reinforcement, the Manufacturer is required to clearly stencil on the inside of the pipe the words "top" or "bottom" to indicate the correct position where laid. The pipes shall be laid with the tops and bottoms in the correct positions.

12.3 RC Box Culvert

The lower portions of the precast RC box culvert sections shall be laid on the approved bedding material true to line and grade. All edges to be jointed shall be thoroughly cleaned with a wet brush. Immediately prior to jointing, a thin layer of Portland Cement mortar (3:1) shall be spread over the joint. All joints shall be made in a workmanlike manner, and the interior of the sections shall be kept free of mortar.

12.4 Cement Mortar

The cement mortar used for making joints both in rebated pipe and box culvert sections shall consist of one part cement by volume to three of sand. The consistency of the joint mortar shall be such that it will adhere readily to the pipe and can be easily squeezed out at the joints. The mortar shall be used within thirty (30) minutes after the ingredients are mixed with water. The completed joints shall be immediately protected from air and sun with an initial covering of moist earth, sand, canvas or burlap. If not backfilled at once, the joint mortar shall be cured for 48 hours.

12.5 Corrugated Steel Pipe

All corrugated steel pipe shall be installed in accordance with the Manufacturer's recommendations and the relevant Standards specified in Section 2 of this Specification.

12.6 Pipe Invert Levels

All pipes shall be laid such that the invert levels at both the upstream and downstream ends are not more than +20mm from the corresponding levels shown on the Drawings. Notwithstanding these tolerances, the pipes shall be laid such that backfall never occurs and a minimum gradient of 1 in 500 is achieved.



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Section 13 - Backfilling 13.1 Trenches

Backfilling and compaction to trenches unless otherwise specified shall conform to the relevant requirements of RT Standard Specification SS-C101 and with the Manufacturer's recommendations.

13.2 Excavated Material

Excavated material not required for backfilling shall be disposed of as directed by the RT Company Representative in accordance with this Specification.



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Section 14 - Rip-Rap 14.1 Location and Thickness

Rip-rap shall be placed in the locations and to the thicknesses shown on the Drawings or as directed by the RT Company Representative. Rip-rap shall be bedded on a prepared base of natural earth or compacted fill.

14.2 Placing and Dumping

Unless otherwise shown on the Drawings or directed by the RT Company Representative, rip-rap shall be machine placed or dumped. All rip-rap shall be well graded within the sizes specified below and so far as is practicable shall be placed with the smaller stone against the earthworks to be protected, so as to prevent loss by scour through the interstices.

Stones for dumped rip-rap shall be angular and irregular shape having a thickness not less than one fourth of the length.

The source of material for rip-rap shall be oversized material available from approved borrow areas or cut to fill earthworks. The rip-rap shall be approved by the RT Company Representative prior to placement.

14.3 Rip-rap Sizes

Rip-rap to be used in any location shall be as shown on the Drawings or directed by the RT Company Representative. Rip-rap stone shall have graded sizes in accordance with the following tabulation:

Rip-rap Size (mm) % Passing

500 100

400 85-95

300 60-75

200 30-40

100 10-15

14.4 Areas of Use

Areas on which rip-rap is to be placed shall be trimmed and dressed to conform to the cross sections shown on the Drawings within an allowable tolerance of ±100mm from the theoretical slope lines and grades. Where such areas are outside the allowable minus tolerance limit they shall be brought to grade by filling with compacted material. Immediately prior to placing rip-rap, the prepared base will be inspected by the RT Company Representative and the placement of material shall not be commenced without the approval of the RT Company Representative.

14.5 Dumped Rip-rap

Dumped rip-rap shall be placed to produce a reasonably well graded mass of rock with the minimum practicable percentage of voids.



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The larger stones shall be well distributed and the entire mass of stones in their final position shall be roughly graded to conform to the gradation specified. The finished rip-rap shall be free from pockets of small stones and clusters.

14.6 Segregation Prevention

Rip-rap shall not be placed in layers or by dumping into chutes or by similar methods likely to cause segregation of the various sizes.

Rearranging of individual stones by mechanical equipment or by hand may be carried out if necessary to obtain a reasonably well graded distribution of stone.



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Section 15 - Drainage Pits Headwalls and Inlets 15.1 Construction Requirements

Drainage pits, headwalls and inlets shall be constructed to the details shown on the Standard Drawings or as directed by the RT Company Representative. The concrete used in the Works shall be Grade 20/20 in accordance with RT Standard Specification SS-C107.

15.2 Inlet Pipes

Where shown on the Drawings, inlet pipes of the diameter shown are to be cast in to the drainage pits. Such pipes shall consist of three lengths of pipe, the first neatly cast into the drainage pit, in such a position that a pipe drain may be connected thereto at a future date. The other pipes shall not be jointed, and shall be laid so that the invert of the last pipe is level with the ground surface or as directed by the RT Company Representative.

15.3 Lids, Covers and Gratings

Lids, covers and gratings to drainage pits shall be installed in accordance with the Manufacturer's recommendations. Each lid, cover or grating shall be designed to carry, without damage, traffic loads applicable to the installation.