POWER PLANT: CIVIL WORKS OF FUEL GAS PIPELINE

POWER PLANT

 CIVIL WORKS OF FUEL GAS PIPELINE

CIVIL WORKS

Site Grading

a]         The work shall be carried out to grade the area roughly in such a way so that an ideal grade that requires as little as possible cut and fills is achieved all over the site for construction of the metering station

b]         The grading shall mean to produce the final grade levels after the construction of the facilities.

 The grading may require reshaping by way of cut and fill required to match the final levels of roads and other structures for drainage and other purposes. 

The grading of the site shall be carried out as per approved engineering drawings.

c]         The material used for fill shall be coarse granular material of approved type and classification.

 The material shall be composed of in-organic material and shall have 100% passing the 2-inch sieve with a maximum of 20 % passing 200-micron sieve and having a maximum PI of 6. 

The fill material shall be free from any organic matter, garbage, or any other undesirable material. 

The fill shall be provided with a 150mm thick top layer of marl cap.

d]         Fill material shall be placed in less than 20 cm layers and thoroughly compacted with approved self-propelled rollers weighing at least 10 tons.

 Areas inaccessible to rollers shall be compacted with approved mechanical tampers.

 Sufficient water shall be added to fill material when required to obtain maximum compaction.

 Each fill layer shall be compacted to 95 percent of maximum dry density as per ASTM D-1557 or to 85% of relative density as per ASTM D-4253/4254, as determined by the Modified Proctor Density method. 

e]         Unsuitable soil shall be wasted in authorized designated disposal areas and as directed by the delegated authorities, disposal on the Owner’s property shall not be permitted.

 While preparing the site for the proposed construction, a suitable drainage network shall be planned so as to remove the water from rains and from the other sources effectively away from the main structures. Areas receiving cut shall be proof rolled

    Paving

a]         The work shall consist of pavement or concrete floors composed of Portland cement concrete, with or without reinforcement as specified, constructed on a prepared subgrade or base course in accordance with the specifications.

 These pavements and concrete floors shall be used where a working platform is required for doing maintenance of various equipment, parking areas, footpaths, etc.

b]         The design and construction of concrete floors and pavements shall be carried out in accordance with the requirements

Equipment Foundations

a]         The purpose of the foundation is to support the equipment, which shall be installed on it, and transfer the equipment load to the required foundation bed.

 The equipment foundation shall be made of reinforced concrete foundation block.

 The concrete foundation block will be isolated from the adjacent concrete floor. All penetrations, cut-outs for piping and electric conduits, etc. shall be provided.

b]         The dimensions of the foundations shall be as per the vendor requirements.

 Foundation shall be placed at a level where the foundation soil is having the required bearing capacity and the Contractor shall be fully responsible to check and verify the required soil bearing capacity at the formation level.

 The foundation concrete shall be placed to produce as far as practical, a monolithic structure while minimizing the susceptibility of the foundation to shrinkage cracks and distortion.

 All concrete block foundations shall be placed on a firm foundation bed, free from any loose material.

 Any loose material under the equipment foundations shall be removed and replaced with selected backfill material placed in the controlled lift.

 Any over-excavation carried out inadvertently shall be brought up to the required elevation by mass concrete.

c]         The foundation shall be protected against the salts and chlorides present in the soil with membrane or coating as per the geotechnical recommendations or relevant Saudi Aramco standards.

d]         The Contractor shall provide all the necessary design calculations and drawings and submit the same for the review and approval of the Owner/Engineer.

 The Contractor shall submit full structural details for all the works.

e]         Equipment foundation blocks shall be designed and constructed as per-OWNER

                Lighting Pole Foundations / Pipe sleepers / Pipe supports

a]         Lighting pole foundations, pipe sleepers,

 and pipe supports shall be provided wherever required.

 These shall be made of concrete with at least 1.0m embedment depth and shall be provided with proper footings.

 The top of concrete shall be at least 500mm above the adjacent FGL in case of pipe sleepers and at least 150mm in case of lighting poles.

b]         The Contractor shall provide structural steel sections, tubes to support pipes, and other miscellaneous structures as required. 

These supports shall be supported on concrete pedestals with the top at least 150mm above grade.

Security Fence

            The fence shall be SSD type-1 and 105 with a total height of fence including any cranked extension of 2.9 m measured from the finished ground level to the top of the line of the barbed wire attached to the cranked extension.

 The chain-link fence shall be PVC-coated.

Drainage

            The area within the metering station shall have an FGL higher than the adjacent grade and area shall be graded in such a way so that all the rainwater is the surface drained to the outside

Access Roads

            The access roads shall be constructed. If the sub-grade material does not meet the requirements, it should be removed up to at least a depth of 300mm and replaced with suitable material.

 A sub-base layer of at least 200 mm depth shall be provided over the sub-grade, which shall be compacted to a maximum dry density of 95%. Asphalt concrete pavement shall be provided on top of the sub-base.

Access Platforms

            Access platforms shall be provided for access to equipment/valves etc.

 wherever required.

 The platform supporting structure shall be made of carbon steel structural framing, channels, angles, supporting column sections. 

The platform including access stair treads shall be made of grating with main and cross flat bars, stringers, clips, toe boards, and expansion bolts as required for valves, gas separators/filters, scraper stations, and similar equipment. 

These platforms shall be provided with a railing with a top and mid-handrails with fittings.

 The steel structure supports shall support concrete pedestals, the top of which shall be at least 150mm above the finish grade level.

 All steel sections including fittings used for manufacturing of these platforms shall be hot-dip galvanized.

   Control Room

  The control room shall be made of a pre-fabricated cabin of adequate size to house all control, monitoring, communication equipment, electrical panels, and batteries, etc.

 The cabin shall be placed over steel beams resting on concrete foundations. 

The cabin shall be at least 300mm above the finish grade level. The cabin shall be manufactured

Gas Pipeline

a]         Excavation & Backfill

i.          Trench excavation for pipeline shall be performed to required sub-grades. Trenches in non-cohesive or soft cohesive soils shall be sloped to 60 degrees.

 All trenches shall be sheeted and braced adequately to maintain the site safe to life and property.

 The bottom of the trenches shall be well-graded and compacted to provide uniform bearing and support for each section of the pipe at every point along its entire length. 

In case the rock is encountered, the base shall be excavated to exceed the foundation bottom by 150 mm, and the over depth shall be filled with load-bearing material

ii.          In areas of fill, all required fill material shall be placed and compacted before performing trench excavation and shall be kept free from water.

iii.         After the inspection and the required tests have been performed and found satisfactory by the Engineer, the trenches shall be backfilled carefully with the approved materials.

 A minimum half (1/2) meter berm shall be provided over the pipeline in addition to one (1) meter cover, and shall be stabilized with suitable material

b]         Road Crossing
            Wherever the pipeline is crossing the existing road, properly designed road crossing (thrust boring type etc.