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TECHNICALREQUIREMENTS

Part n° 03

Pipeworks

CTI - 28/10/98 AR/SR 1/4

TECHNICAL SPECIFICATION

PART N° 03

PIPEWORK

CONTENTS

Page

REQUIREMENTS OF APPLICABLE REGULATIONS 2

GENERAL 2

1. BURIED PIPES 2

1.1 REQUIREMENTS GOVERNING EXECUTION OF THE WORKS1.2 INSPECTION

2. DRAINPIPES 3

3. MAIN DRAINS 3

4. DRINKING WATER PIPES 4

5. ADDITIONAL REQUIREMENTS CONCERNING GRAVITY DRAINS 4

6. PIPE INSPECTION PITS 4

7. CULVERTS 5

8. SEPTIC TANKS 5

CTI - 28/10/98 AR/SR 2/4

REQUIREMENTS IN CURRENT REGULATIONS

The Contractor will be required to comply with all Mexican Building Codes applying to civilengineering works, insofar as these do not contradict the present list of technicalrequirements.

In general, the Contractor will be required to build the structures covered by the presentcontract in line with normal rules of practice.

GENERAL

This section concerns:

− gravity drainpipes for waste water, sewage, rainwater and industrial waste water;

− pipes for various services: drinking water supply pipes and culverts, water forfirefighting, fuel oil, electric cables, compressed air, industrial water.

The section includes the apparatus and parts necessary for satisfactory operation of thesystems.

Depending on the type of material chosen (reinforced or unreinforced concrete or PVC), theContractor must specify its source, nature and quality, the type of connection and jointing,and if appropriate the extent of resistance to acids or bases.

Pipes and culverts will be supplied and installed in accordance with the standards. Joints willbe made in accordance with the suppliers' instructions.

The water reserve for firefighting must be calculated.

1. BURIED PIPES

1.1. REQUIREMENT GOVERNING EXECUTION OF WORKS

All pipes will be:

- either buried at least 80 cm below finished ground level;- or laid inside inspectable reinforced concrete culverts.

All works related to execution of the trenches are included in the "Earthworks"section.

A 100 mm thick layer of sand will be spread at the bottom of each trench andadjusted to the definitive gradient.

Pipe sections will be fitted together in such a way that the inside surface is perfectlysmooth at the joints.

Backfilling will take place only after joints are fully set and the tightness of the pipeshas been checked.

CTI - 28/10/98 AR/SR 3/4

If the soil is particularly poor or where there is a risk of settlement or movement, areinforced or non-reinforced concrete slab will be laid on the sand bed, on which thepipe will be laid with appropriate concrete cradles.

If the loadings exceed the normal strength of the pipe, it will be coated with concreteto a thickness equal to at least 25% of the diameter and not less than 50 mm, aboveand below, and at each side to a thickness at least equal to half the diameter.

At wall penetrations, a sleeve will be provided; no pipe must be sealed in the wallstructure.

An inspection pit will be provided at all changes of direction and at branches.

1.2. INSPECTION

The tightness check on pipes will be done with the pipes fully exposed, to allow thejoints to be inspected.

Pipes will be clean and free of waste matter or earth.

Pipes to be used under pressure will be subjected to a pressure of 150% of theservice pressure for a period of 4 hours with no change.

Other pipes will be subjected to a pressure of 0.3 bar for a period of 2 hours andmust not show a loss of more than 0.3 l/m_ of inside surface area per hour.

These results will be subject to the approval of the Employer.

2. DRAINPIPES

Drainpipes will be in clayware, concrete or PVC. They will be laid level and covered withfiltration materials to a depth of 500 mm. Backfilling will be done carefully without crushing thedrain. Above the filtration material, the backfill must be free of clay, mud, vegetable matter,etc.

3. MAIN DRAINS

The main drains will be in cement, clayware or PVC.

They will be laid carefully, flat, on a 50 mm thick bed of sand.

They will be covered, up to their mid-point, by compacted clay. The trench will then bebackfilled with dry stone or draining material to a minimum depth of 500 mm.

Backfilling will be carried out carefully, to avoid crushing the main drain.

Above the filtration material, the backfill will be free of clay, mud, plant debris, etc.

An inspection pit, if necessary with parapet, will be provided at each change of direction, andon straight sections every 40 m at the most (inspection pits are dealt with under "Concrete").

CTI - 28/10/98 AR/SR 4/4

4. DRINKING WATER PIPES

The drinking water system will be designed for a minimum dynamic pressure of 4 bar. Pipesmust withstand a pressure of 1.5 times the maximum pressure.

The materials and constructional details of pipes, valves, joints and hydrants will be subject tothe approval of the Employer, who may request laboratory tests to be carried out at theContractor's expense to verify the quality of the materials.

5. ADDITIONAL REQUIREMENTS CONCERNING GRAVITY DRAINS

These pipes will be made of concrete or PVC. An inspection pit will be provided at eachchange of direction or gradient (at least every 40 m).

Joints must be leakproof. All sewage pipes must undergo pressure tests.

No pipes will have a diameter of less than 150 mm and their gradient will always be morethan 0.5% (1 in 200). Gradients must be adequate to ensure satisfactory operation of thesystem.

When full, the pipes must be capable of carrying 150% of their design flow for a speed notexceeding 3 m/s. The minimum speed will not be less than 0.6 m/s. A design note will beprovided to the Employer in respect of all pipes in the works.

6. PIPE INSPECTION PITS

Their foundations will consist of a reinforced or non-reinforced concrete raft. Their walls willbe in reinforced concrete with a recess for fitting the cover slab. A metal angle iron will begrouted into the concrete as a base for the slab.

They will be made watertight by a smooth waterproof cement grout 20 mm in thickness.Connections to the incoming and outgoing pipes will be perfectly leakproof.

When the depth of the inspection pit so requires, galvanised iron steps 25 mm in diameter willbe grouted into the wall at vertical intervals of 150 mm. A 25 mm galvanised iron pit laddermay also be executed with split grouting, with 25 mm diameter steps with shoulder.

7. CULVERTS

For services supplied through culverts, please see the requirements given in chapter 5:"Additional requirements for gravity drains".

8. SEPTIC TANKS

Septic tanks will comply with local health regulations.

They will be either prefabricated, or in waterproof reinforced concrete with two compartments.The inlet pipe will discharge at least 300 mm below the surface of the liquid and they will beventilated by a stench pipe leading to roof level.

They will be perfectly leakproof and must be followed by a purification system.