River Training Works -
Method Statement
1.0 THE PROJECT SYNOPSIS
The Works to be constructed under this Contract form part of the Padma Multipurpose Bridge Project in Bangladesh. The Padma River separates the southwest of Bangladesh from other parts of the country, in particular the north-central region where the national capital of Dhaka is located. Although there have been improvements to, and development of, the road network in the southwest, links with the rest of the country across the Padma river are still only possible by ferry. The only alternative is via the newly constructed Lalon Shah bridge at Paksey, connecting southeast Bangladesh with the northwest. The capacity of ferry services is very limited and waiting time at ferry crossings is about one hour for buses and light vehicles and more than two hours for trucks – although trucks can wait for more than a day.
In addition the riverbanks of the Padma are very unstable and the river width changes frequently, leaving approaches to the ferry crossing seasonally inoperative. The expansion of existing ferry terminals is made difficult by these conditions. Moreover, there is an urgent need to replace dangerous ferry and launch operations between Dhaka and the southwest by safer and more reliable surface transport, as overloaded vessels frequently sink in this waterway when passing through the treacherously turbulent confluence of the Padma and Meghna rivers. The social, economic, and industrial underdevelopment of the southwest region, is due in part to difficult access across the Padma River to the rest of the country. A bridge across the Padma River will strengthen links between the southwest and north-central regions. A combined highway and railway bridge will enhance freight and passenger transportation between Dhaka and major points in the southwest of the country and contribute substantially to the development of the region as well as national economic growth.
The Padma Multipurpose Bridge Project comprises a new fixed crossing of the Padma River in Bangladesh. It will consist of a new bridge approximately 6.15km long across the Padma River; approach viaducts; major river training works; approximately 13.6 km of approach roads; and bridge end facilities, including toll plazas, service areas and offices. The main bridge is to carry a 4-lane highway, single-track rail and other facilities including gas and telecommunication services. The Project is divided into five separate construction contracts: Main Bridge, River Training Works (RTW), Janjira Approach Road and Selected Bridge End Facilities, Mawa Approach Road and Selected Bridge End Facilities and Service Area 2.
2.0 EXTENT AND SCOPE OF RTW WORKS
The Works to be constructed under the Contract No.PMB/RTW/01 of BBA form the river training works required to ensure that the Padma River will flow under the Padma Bridge and protect it from erosion for the entire life span of the project. The river training system consists of a guiding revetment along both banks of the Padma River, extending upstream and downstream from the bridge axis. The proposed revetment along the north bank - Mawa side, is about 1.5 km long and extends the erosion resistant clay layer that forms the bank for many kilometres upstream in the bridge area, while the guiding revetment along the unstable south bank -Janjira side, is about 11.5 km long. The main function of the guiding revetments is to guide the flow under the bridge and ensure that the approaches to the bridge will be protected against erosion by outflanking river channels. In addition, the revetment protects the approach road on the south bank and other infrastructure such as two large resettlement villages. On the north bank, the above water portion of the revetment forms an embankment that sits above the floodplain elevation and the works include drainage on the land side of the embankment. On the south bank the upstream approximately 7.5 km of the revetment has the crest at the existing flood plain elevation with the 3.5 km downstream portion in the region of the bridge alignment being an embankment sitting above the floodplain. Located in the south bank revetment upstream of the embankment are 5 offtake structures. These are located at existing distributaries which become active (flowing water) during the rising limb of the annual flood hydrograph and dry out after the monsoon season. The khals are connected with major bridges in the south approach road. The scope of works of RTW, includes:
Construction of the guiding revetments consisting of above and below water bank, preparation and protection cover, and placement of launching apron;
Ground Treatment on the north and south banks required for the main bridge (Provisional Item);
All Protective and Temporary Works, and other required consequential work;
Additional work as BBA may direct for the purpose of construction, completion and maintenance of the Works including upgrading of launched apron sections during construction.
3.0 SITE AREAS, ACCESS AND USE
3.1 Boundaries of the Site
The Site comprises the areas of land allocated to Contract No.PMB/RTW/01 as shown in the drawings. This land already acquired by the Employer shall be made available to the Contractor for the execution of the Works free of charge. The Subcontractor will specifically demarcate their portion of the site as well.
3.2 Adjoining Sites
We (the subcontractor) understand that the Contractor shall permit the personnel, workmen, materials, vehicles, plant and equipment of the other contractors for adjoining contracts access and movement over and through the Site without charge for purposes in connection with the execution of their works as far as practical. Accordingly, we (SINAMM, the subcontractor) shall cooperate in this respect.
3.3 Contractors' Working Areas
Part of the Site available to the Contractor for his temporary use may be utilized to provide space for storage, offices, workshops, prefabrication facilities and the like. Hyundai shall provide, erect, construct, and equip and remove on completion all offices, accommodation, workshops, stores, berthing loading and unloading facilities, weigh bridges, prefabrication and other areas for the Contractor's staff, personnel and construction equipment required by the Contractor directly or indirectly for the execution and completion of the Works and the remedying of any defects therein.
3.4 Security
The Contractor shall ensure include a security control system which shall consist of sufficient equipment and personnel to prevent unauthorized access 24 hours per day, 7 days per week and which can meet the prevailing circumstances to ensure the safety and security of persons and property on the site. In this respect, the subcontractor shall cooperate with the Contractor.
3.5 Cleanliness and Reinstatement
The subcontractor shall maintain throughout the period of construction the whole of the area of his operations in a clean, tidy and safe condition by arranging his materials and construction equipment in an orderly manner. All rubbish, waste material, debris and the like shall be systematically cleared off the working areas and removed directly off the site for disposal in authorized tips or other proper disposal facilities.
4.0 MATERIALS AND PRODUCTS FOR RTW AND AREA OF USES
4.1 Primary Materials And Products For Rtw And Area Of Uses Subcontractor's Concern
The primary materials and products required for the construction of the RTW Works and the uses are:
Geotextile and Geobags – filter, slope protection and launching apron
Rock Rip Rap – slope protection
Cast Concrete (CC) Blocks –slope protection and crest treatment
Bricks – roadways and bedding material
Open-Celled Concrete Pavers – road sides
Sands – fill, land reclamation, geobag filling and bedding material
Aggregates for Ground Treatment works ("stone columns") [Provisional Item]
4.2 Subcontractor's Concerned Areas
The subcontractor (SINAMM) gives method statement of items of RTW they are interested in and accordingly they have submitted the Quotation as per Quotation Inquiry Sheet issued by Hyundai. The related work components include:
Supply and stockpile of Geobag
Sand filling and placing of Geobag
Supply and stockpile of Geotextile filter
Placing of Geotextile
Production of CC blocks
Placing of CC blocks
Bedding layer for CC Blocks
RC Anchor Beam
Pavement around the Embankment
Supply and stockpile of Rock
Placing of Rock riprap
Land restoration (Vetiver Plantation)
5.0 GEOTEXTILES, GEOBAGS AND ACCESSORIES
The basic raw material which is used in geo-textile is polymer and the most widely used polymers are polypropylene and polyester. Based upon the manufacturing process, geo-textile is often categorized as woven or non-woven. Woven geo-textile are manufactured by weaving weft thread through warp thread. While non-woven geo-textile is produced from randomly distributed continuous or staple fibers which are bonded together chemically, thermally or mechanically .
Geotextile filter sheets are designed to be used for the separation of the fine subsoil and a protective armour layer, concrete blocks above water, and possibly as an alternative under rock armour below water. The filter cloth must be able to provide filtration parallel and perpendicular to the plain. The cover layers consist of (i) concrete blocks either placed as single armour layer or dumped in multiple layers or (ii) rock under water if a fascine mattress is approved as an alternative to 125 kg geobags. The filter cloth is either placed on a 10 cm thick sand layer or directly on the subsoil under water. Generally where concrete blocks are dumped loosely on the filter, broken bricks are provided as cover layer to dampen the impact of the concrete blocks and reduce the risk of puncturing of the geotextile filter. Where broken bricks have not been specified for placement under dumped blocks, appropriate measures to be taken ensuring the non-puncture of filter cloth.
Geobags are designed to be filled with selected local sand (processed as necessary) which are to be used for riverbank protection either as filter layer under rock armour (125 kg filter geobags) or as multilayer slope/bed coverage (800 kg geobags). Geobags are subject to hydrodynamic river forces either temporarily (125 kg filter bags) or during the lifetime of the RTW when exposed to river flows. It is important that the geo-textile is sufficiently robust to retain the specified sand-fill. In addition, the geotextile bags must withstand loads resulting from filling, handling, transporting, and dumping on the underwater slope and apron.
5.1 Geobag Yards
The Geobag production will require an assembly yard with (i)sand screening facilities, (ii) hoppers for the filling, and (iii) scales for measurement of weight. In addition, a covered area will be required for the storage of unfilled bags to protect them from the weather action and any damage.
All of these facilities are to be located in a relatively compact assembly area on the site at a location. The Storage of the filled bags can be located adjacent to the assembly area..
5.2 Physical, Mechanical and Hydraulic Properties
All geotextile material and accessories such as bags, geotextile filter sheets and sewing thread shall fully satisfy the requirements of the technical specifications. In general, testing of Geo-Textile fabric material for Geotextile bags, Geotextile Filter Sheets and Sewing Thread shall follow ISO standards in their latest version. The geotextile materials shall undergo autoclave test and abrasion resistance test at specified laboratories.
The Geo-textile fabric shall be manufactured from polypropylene fabric and shall be non-woven and needle-punched and not solely thermally bonded. Any thermal bond shall not influence the flexibility of the geobags, including their launching behaviour under water. The required porosity of Geo-Textile fabric shall be minimum 80%. Porosity is a calculated value based on tested material characteristics and the specific weight of the fibres. The properties of the Geo-Textile to be delivered to the site shall be tested according to the relevant standards in their latest version and the technical values given in the following Tables. Geotextile filter sheets and Geobags to be used at the site shall comply with the following specifications as per tender documents:
Properties
Test values of
Geotextile Filter sheet
Test values of
Geobags
Characteristic opening size O90
60 μm and 80 μm
60 μm and 80 μm
Mass per unit area:
400 g/m2
125kg bag 400 g/m2
800kg bag 600 g/m2
Thickness at 2 kPa
4.5 mm
-
CBR static puncture resistance
4000 N
4000 N
Tensile strength (machine direction or MD
and cross machine direction or CMD)
20.0 kN/m
20.0 kN/m
Elongation at maximum force (MD)
60% and 100%
60% and 100%
Elongation at maximum force (CMD)
40% and 100%
40% and 100%
Water permeability, (velocity index for a
head loss of 50mm – vH50)
2*10-3 m/s
Oxidation resistance
50% of original tensile
strength before immersion
50% of original tensile
strength before immersion
UV spectroscopy
For ongoing QA purposes
For ongoing QA purposes
UV weathering resistance
70% of original tensile
strength before exposure
70% of original tensile
strength before exposure
Abrasion
-
After abrasion test: tensile strength 75% of specified
tensile strength, O90 90 μm
The dimensions of the empty bags be optimized so that the bags can be filled fully, considering sand with some moisture content is usually used to fill the bags. The intention is to provide just enough space empty at the top of the bag, so that it can be closed easily and without need to stitch through the sand-fill.
Dimensions and dry weight of the geobags shall comply with the following table:
Properties
800 kg bag
125 kg bag
Unfilled Bag size (outside)
1700mm X 1250mm
1030mm x 700mm
Nominal side ratio
1.36
1.47
Min. filled dry weight
800kg
125 kg
Min. Seam strength
18 kN/m
18 kN/m
The minimum dry weight shall be as specified. To account for moisture, we shall determine the moisture content and calculate the filled dry weight. We shall confirm that the specified minimum filled dry weight is achieved using the filling equipment and methods employed. If the minimum weight cannot be achieved, the bag size may be adjusted.
Required properties of the thread used for stitching shall comply with the following specifications:
Properties
Test values of Stitching Threads
Oxidation resistance
50% of original tensile strength before immersion
UV spectroscopy
For ongoing QA purposes
UV weathering resistance
70% of original tensile strength before exposure
5.3 Delivered Quality of Geotextile fabric
Geotextile fabric in standard rolls used for the manufacture of Geo-bags or delivered as Geotextile Filter Sheets shall be clearly marked at regular intervals with the product name and grade and production lot number. The marking will be of such a density that this information is contained on every bag to identify the supplier of the bags in later years.
Each batch of Geotextile Filter Sheets and Geobags, shall be packed in lots or sub-lots (named bales) and marked with labels that identify:
brand and grade,
production lot number and date of production of Geotextile used to manufacture the bags,
the running number of the bags,
the size and capacity of bags, and
name and signature of the quality control person that certifies the compliance of the aforesaid specifications for all bags in each bale.
The Sewing Thread shall be packed in standard paper board/hard board cartons and marked with labels that identify:
brand and grade,
production lot number and date of production,
length of the thread per cone,
the number of cones in the carton, and
the running number of the carton.
5.4 Acceptance and Rejection of Geotextiles
Geotextile filter sheets and geobags not meeting the requirements of Technical Specifications shall be rejected. Upon completion of the contract and before final acceptance by the Engineer, the Contractor shall deliver complete documentation of all details related to the manufacturing, delivery processes adopted and all test results, including the documentation of fabrication and delivery of geotextile filter sheets and geobags, in a format acceptable to the Engineer/BBA.
5.5 Quality Assurance Requirement
Before starting production of Geobags and Geo-Textile Filter Sheets, the Contractor shall submit to BBA, a Quality Assurance (QA) Manual describing the supplier's quality assurance and control system in effect in the Geo-Textile and bag fabrication plants with specific details about quality assurance processes in effect during the production process under this contract. The Contractor shall submit test certificates from the supplier separately for each consignment/shipment of Geo-Textile fabrics and bags.
5.6 Plant and Pre-Shipment Inspection
We understand that BBA authority may inspect directly or through an independent inspection agent, the manufacturing plant(s) of Geo-Textile material prior to commencement of the production process, during the production of the Geo-textile fabrics and during the fabrication of geo-bags, to audit the Supplier's quality assurance process, testing of materials, and to confirm compliance with the Specifications.
5.7 Quality Control by Manufacturer/Supplier of Geotextile fabrics
Compliance with the technical specs, the supplier/manufacturer shall undertake sampling and testing of Geotextile fabrics manufactured for all mechanical and hydraulic properties frequently. The Supplier shall also undertake sampling and testing to determine UV and abrasion resistance of the Geotextile fabric in compliance with these specifications. The related testing reports shall be submitted to Employer. The supplier of the Geobags and geotextile shall undertake sampling and testing of the seams of the bag to ensure compliance with the specifications.
In addition, on being instructed to do so by the Employer, the Contractor shall take one approximately square sample of at least 4 m2 from each of two rolls, or 4 bags from each different delivered lots for the purposes of a "Control Test". The seam sample requires the full seam length of bags without cutting. The "Control Test" samples will be sent to a testing laboratory acceptable to by the Employer. A Control Test normally consists of the following individual tests:
mass per unit area;
layer thickness;
tensile strength at failure in longitudinal and transverse direction;
water permeability (velocity index VIH50 for a head loss of 50mm);
characteristic opening size, O90D
CBR,
abrasion test, and
UV spectroscopy (to confirm stabilizers)
5.8 Preparing and Sewing of Empty Geo-bags
We shall look after the following salient features in preparing geobags from geotextile fabrics:
The Geobags shall be prepared by sewing on the two longer longitudinal sides. The smaller transverse top side shall be kept open for subsequent closing. Sewing should be done by stitching machine. The folded Geo-textile sheets for a bag can be sewn at machine or cross-machine direction of the geotextile fabric.
The number of stitches per inch shall not be less than 5. The stitch shall be double thread (two rows of stitches) chain stitch type 401.
At the bottom end of each seam (at the folded side) the stitch shall be locked either by stitching one time back and forth for a length of minimum 2.5 cm from the end of the bag, or by joining the ends of the two threads e.g. by gluing, welding, knotting or other appropriate methods, acceptable to the Employer.
The two lines of stitches shall be within 5 mm distance with a margin of 2 cm from the outer edge of the Geo-Textile to the centerline between the two seams. The tolerance shall be 3 mm in each direction.
The thread used for stitching should be of the same material characteristics as the Geo-Textile or of material more durable than the material of Geo-Textile. The thread used must be of high quality and equivalent stability to UV exposure and with the same degree of stabilization as the Geotextile material.
5.9 Filling and Closing of Geobags
Salient features in filling the geobags are as follows:
Sand for filling Geobags must be taken from a source that has been tested and approved.
The geobags will be filled at least to the dry weights indicated in these specifications and the design drawings. Scales will be present at the filling area for the monitoring of the weight. It is preferred that the scale is part of the filling equipment such that the amount of sand is controlled by the scale.
It is expected that the geobag filling will be performed in a production yard to allow effective quality control. However, filling may be done on board the dumping vessel if the Contractor can satisfy the Engineer that specified quality and quantity control measures can be effectively maintained. Particular care is to be taken to ensure that each bag is sufficiently filled, and that the bags have been accurately counted and totals recorded in the registry. The Contractor's quality control system for ensuring all of the filled geobags meet the specified requirements for weight etc. shall be submitted to the Engineer for his review and acceptance at least 4 weeks before commencing the filling operation.
Geobag filling will be performed in a production yard to allow effective quality control. However, filling may also be done on board the dumping vessel. Particular care is to be taken to ensure that each bag is sufficiently filled, and that the bags have been accurately counted and totals recorded in the registry.
QC system shall ensure that the filled geobags meet the specified requirements for weight etc.
In addition, for audit purposes, filled bags shall be checked for weight at random.
Additional tests shall be performed to ensure that geobags are filled to the required weights. If a sample is found to be less than that specified, then the whole batch from which it was taken will be checked and any under-weight bags shall be opened and filled to the correct weight.
The bags will be closed immediately after filling by two lines of stitching. The stitching shall be the same as the side seam. The number of stitches per inch should not be less than 5. While one seam shall be straight with a distance of 2 to 2.5 cm from the edge of the bag, the second seam forms an arch, starting and ending below the top seam and crossing it about 5 to 10 cm inside the side seams.
Sufficient electric handheld sewing machines will be made available so that the production of filled geobags is not restricted. Arrangements shall be made for routinely servicing and repair of the sewing.
,
5.10 Storage of Geobags
Filled geobags shall be transported and stored in the stockpile yard/area assigned for this purpose. Any geobags damaged during transportation and handling will be emptied and removed from the Site.
6.0 ROCK RIP RAP
Rock is angular material obtained from a quarry, and will be required in the slope protection works. Here we present an anecdote that covers the requirements for collection, sorting, transportation, storing and handling of rock. The sources of rock must be dependable and provide adequate quantities, to ensure timely completion of all revetment work.
Rock used in the construction of the Temporary Works may subsequently be used in the Permanent Works, provided that the grading and properties of the rock recovered from the Temporary Works still conforms to the Specification. Prior to supplying any rock, we shall obtain all required permits and testing reports.
All material testing reports will be from suitably competent laboratories acceptable to the Engineer. The codes and standards to be followed are predominantly ASTM.
6.1 Rock Characteristics
The rock shall be hard, durable, angular in shape, resistant to weathering and to water action, free of defined cleavage planes, and shall not be adversely affected by repeated wetting and drying or by multiple handling.
The rock shall be free from soft, weathered or decomposed parts, overburden, spoil and organic material; and shall meet the gradation requirements specified in Technical Specifications.
Material that is not suitable includes but is not limited to shale and rocks that are laminated, fractured, porous, or otherwise physically weak.
Not more than 25% of rock, distributed through the size gradation, shall have a length more than twice the breadth or thickness. Neither breadth nor thickness of a single stone shall be less than one-third of its length. Rounded stones or boulders will not be accepted unless authorized by the Employer.
A set of 10 Nos. individual D50 (450 mm) size stones (randomly selected by the Engineer) are to be individually dropped from a height of 1.0 m on to a rigid surface (or second stone of comparable size) without breaking or cracking.
Table 6.1a - Properties and Testing of Rock Rip Rap
Rock Property/Test
Reference or Test
Standard
Requirements
Bulk Specific Gravity (saturated surface dry basis)
ASTM D6473
Minimum of 2.65
Absorption
ASTM D6473
Less than 2%
Soundness (Sulphate)
ASTM D5240
Weight loss in 5 cycles shall be less than 12% when magnesium sulphate is used or equivalent when sodium sulphate is used.
Abrasion and Crushing Resistance
STP 7.7
STP 7.8
Aggregate Crushing Value shall be less than 35%. Ten Percent Fines Value shall be minimum 125KN.
Gradation
particle size analysis defined in ASTM D5519
The rock material shall have the following target size distribution: D100 700 mm, D50 450mm, and
D15 300 mm and comply with the gradation limits presented in Table below.
The rock provided for riprap shall comply with the gradation limits presented in the Table below.
Table 6.1b – Gradation Limit for the rock provided for riprap
% Finer
Lower Boundary
(mm)
Target Gradation
(mm)
Upper Boundary
(mm)
Mass (kg)
100
650
700
765
600-1000
85
550
600
680
350-700
50
400
450
500
150-275
15
285
300
325
50-75
3
240
260
280
30-50
0
250
265
25-40
6.2 Supply Sources
All proposed sources of rock material are to be approved in writing by the Engineer. The written approval shall include the names of the suppliers and of individual rock quarries.
Prior to such approval, up to 2 No. staff of the Engineer shall inspect each proposed source accompanied by the Contractor.
Rock shall be obtained from quarries that are already operational, with material that complies with specified requirements and that is available in sufficient quantities.
At least two alternative sources of rock; each capable of supplying at least 50% of the total contract rock quantities are required, preferably in different countries.
Details of all proposed rock sources shall be submitted to the Engineer within 30 days of receiving the Letter of Acceptance for his approval. Within 3 months of receiving the Letter of Acceptance, the Contractor shall submit a comprehensive plan for alternative sources of rock, including designation of the quarry, test data on the rock, permits, means of quarrying, and equipment required for crushing and transportation.
6.3 Testing of Rocks
All tests on rock materials shall be carried out by the Contractor. Generally it is expected that rock intended to be used in the permanent works will be placed in designated stockpiles at the site, and samples for testing will be taken from those stockpiles.
The Contractor may propose an alternative quality assurance process including stockpiling, sampling and testing at the quarry site which may be accepted by the Engineer. However, such a process shall still involve sampling from materials delivered to the site and testing for audit purposes. The Contractor shall carry out such tests to the satisfaction of the Employer to ascertain compliance with the Specifications. Test results shall be recorded and issued on standard test forms as approved by the Employer.
One complete set of rock tests including gradation tests, as defined above, shall be performed for every 10,000 m3 of riprap to be placed. Each test sample shall be selected at random by the Engineer's representative and have a volume of at least 50 m3. The entire sample shall be used to determine rock gradation, and representative subsamples taken from the main sample will be used for all other required tests.
Where practicable, testing shall be done in the Project Laboratory, otherwise at a laboratory approved by the Employer. Results from all the tests stipulated above shall meet the applicable requirements specified above.
Should the contractor elect to re-use rock from any Temporary Works for inclusion into the Permanent Works, then such rock shall be tested for compliance with the Specification after it has been recovered from the Temporary Works.
6.4 Rock Riprap Storage
The contractor will establish areas for the stockpiling of rock rip rap. The Contractor may make arrangements to the stockpiling outside of the site; there shall be a stockpile area established within the site as well in a location accepted by the Employer. The stockpile areas should be positioned and any access routes upgraded such that they are accessible all year round, as delivery of material will have to occur outside of the dry season construction period. At the completion of the construction, any off Site storage yards shall be decommissioned and returned to the condition agreed upon between the owner and the Contractor.
7.0 CONCRETE
Here we give an anecdote covering specifications for concrete, including materials, mix designs, batching, mixing, delivering, inspection, and testing. Concrete shall be composed of Portland cement, fine aggregate, coarse aggregate, and water, with or without admixtures as per requirement of the Employer and technical specifications. The concrete shall be used in the manufacture of Cast Concrete Blocks and in the construction of In-situ Concrete features of the Works.
ASTM standards shall be followed in sampling and testing of concrete materials and products.
7.1 Materials and Handling
i. Portland Cement
The cement used in the Works shall be ordinary Portland cement Type I complying with ASTM C150 or other equivalent standards accepted by the Employer.
The cement shall be delivered to the site in properly sealed bags and sealed bulk containers. Tests shall be performed from each consignment of cement delivered to the site.
For cement delivered by bags we shall
Ensure each bag in the consignment is labelled with the supplier's name, date of manufacture and batch number.
Provide waterproof and well-ventilated sheds or go-downs at an approved location at the Site, having a raised floor of wood or concrete, for storage of cement. The sheds shall be large enough to store sufficient cement to ensure continuity of work.
Stack each consignment separately to permit easy access for inspection.
Ensure the cement is placed in the sheds immediately upon delivery and that it is used in the order in which it has been delivered. Any cement in bags which have been opened shall be used within 24 hours after opening.
For bulk deliveries, we shall
Ensure that each on site storage silo or container is labelled with the supplier's name, date of manufacture and batch number.
Ensure there is no mixing of cement from different consignments or batches during transfer to storage silos or containers.
Ensure the cement is used in the order in which it has been delivered and there is no mixing of cement from different consignments or batches during the production of concrete for use in the Works.
ii. Aggregates
Aggregate shall be hard, durable, dense, and free of adherent coatings such as clay lumps, dust, soft or flaky particles, shell, mica, alkali, organic matter and other harmful substances and conform to the requirements of ASTM Specification C33 for the specified sizes. Aggregates shall be derived from crushed rock or stone. Aggregate shall be mechanically washed to remove salts and other impurities in order to meet the requirement specifications.
Aggregate shall be stored on hard and dry ground with adequate partitions to ensure the separation of different types and grading. Care shall be taken in storage to avoid inclusion of any harmful material in the aggregates. Each batch of aggregate delivered to the Site shall be kept separate from previous batches and shall be stored un-used for a period sufficient to allow inspection and testing to be carried out. The aggregate shall be handled by methods that prevent segregation of particle size.
The various sizes of particles of which an aggregate is composed shall be uniformly distributed throughout the mass and not gap-graded. Sieve analysis of fine and coarse aggregates shall be performed in accordance with ASTM C136.
Coarse Aggregate
The coarse aggregate shall be 19.0 mm downgraded stone chips (ASTM C33 Size No. 67) with the size distribution as shown in Table 7.1 ii-a. The amount of deleterious substances shall not exceed, by dry weight, the limits shown in Table 7.1 ii-b. Coarse aggregate shall conform to the requirements in Table 7.1 ii-c.
Table-7.1iia: Coarse Aggregate Size Distribution (19 mm downgraded stone chip)
Mesh (mm)
Percent
25
100
19
90-100
9.5
20-55
4.75
0-10
2.36
0-5
Table 7.1ii-b: Limits for Deleterious Substances for Coarse Aggregate
Material
Max. % by Weight
Material finer than 75 micron (Sieve No. 200) (ASTM C117)
1
Shale or other material having specific gravity less than 1.95 (ASTM C123)
1
Clay lumps and friable particles (ASTM C142)
2
Other deleterious substances
2
Total of all deleterious substances
3
Table 7.1 ii-c: Coarse Aggregate Properties
Property
Reference
Requirements
Bulk Specific Gravity on basis of saturated surface dry aggregate
ASTM C127
2.6
Absorption
ASTM C127
2%
Resistance to Abrasion (wear as determined by the Los Angeles Test)
ASTM C131/
C535
40% after 500 revolutions
Soundness (Weighted average loss after 5 cycles when tested with Magnesium sulphate)
ASTM C88
12%
Potential Reactivity (AAR)
ASTM C33/
C289
Only aggregates considered innocuous shall be used in the work
Fine Aggregate
Fine aggregates shall be uniformly graded from 3/8-inch (9.5 mm) to fines, washed clean in accordance with ASTM C 33. The specified size distribution and limits of deleterious substances in fine aggregates and fine aggregate's requirements are shown in below:
Table 7.1 ii-d: Fine Aggregate Size Distribution
Sieve No.
Sieve Size
Percent by weight passing
3/8 inch
9.5mm
100
4
4.75mm
95-100
8
2.36mm
80-100
16
1.18mm
50-85
30
600 micron
25-60
50
300 micron
5-30
100
150 micron
0-10
Table 7.1 ii-e: Limits for Deleterious Substances for Fine Aggregate
Material
Max. % by Weight
Material finer than 75 micron (Sieve No. 200) (ASTM C117)
3
Shale or other material having specific gravity less than 1.95
(ASTM C123)
1
Clay lumps and friable particles (ASTM C142)
2
Other deleterious substances
2
Total of all deleterious substances
5
Table 7.1 ii-f: Fine Aggregate Properties
Property
Reference
Requirements
Bulk Specific Gravity on basis of saturated surface dry aggregate
ASTM C128
2.6
Absorption
ASTM C128
2%
Soundness (Weighted average loss after 5 cycles when tested with Magnesium sulphate)
ASTM C88
12%
Fineness Modulus
ASTMC33
2.3 to 3.3 variation not exceed 0.20
Potential Reactivity (AAR)
ASTM C289
Only aggregates considered innocuous shall be used in the work
iii. Sampling of aggregates:
Sampling of aggregate shall be in accordance with ASTM C33 and D75.
The minimum representative sample size for coarse aggregate shall be 25 kg and for fine aggregate shall be 10 kg.
All samples shall be taken from a single source, marked by sample date, location, and sampler's name.
At least one complete set of tests shall be performed for every 2,000 m3 of aggregate supplied, and gradation tests shall be done for every 500 m3 of aggregate.
iv. Water
Conforming to ASTM C94, water for concrete and its curing shall be potable, clean and free from oil, acid, alkali, organic or other deleterious substances and shall. No concrete shall be made with water that does not comply with ASTM C94.
v. Concrete Admixtures and Cementitious Materials
To improve water-cement ratio or water-cementitious ratio or workability of the concrete, accepted concrete admixtures and cementitious materials shall be applied in the mix, providing the strengths specified and other desirable characteristics of the concrete can be achieved and maintained.
7.2 Concrete Specifications
Concrete shall comply with the density and strength specifications in the Table below. The water/cement ratio and minimum cement content may vary based on the Contractor's design mix.
Table 7-2 : Concrete Specifications
Concrete Property/Test
Requirements
Density
2400 kg/m3
7 Day (or equivalent Strength)
15 N/mm2 cylinder compressive strength
28 Day (or equivalent Strength)
20 N/mm2 cylinder compressive strength
Maximum Water -Cement ratio
0.5
Minimum Cement Content
280 kg/m3
Curing period
21 days
Compressive Strength tests
The sampling of concrete using concrete cubes or cylinders shall be undertaken when the concrete is about to be placed into the formwork. Each sampling shall provide sufficient concrete to make a minimum of two standard cylinders or two cubes. Samples shall be taken for each 20 m3 of concrete batched or at a frequency accepted by the Employer.
Slump Test
The Contractor shall undertake slump tests of the freshly made concrete in accordance with ASTM C143 and the slump shall be within the range of 50 to 90 mm or other limits established for the selected and accepted concrete mix design. If the range does not comply with the requirement, it shall not be used. Slump tests shall be carried out on each batch of concrete of 5m3 or more frequently if directed by the Employer.
Non-destructive Test
Recently calibrated 'rebound' (Schmidt or similar) testing hammer will be provided at site for checking the strength of hardened concrete. Testing shall be carried out at the frequency and in the locations directed by the Employer. Field tests taken using the rebound hammer on concrete blocks shall indicate that the minimum allowable strengths specified after 7 days and 28 days after casting have been achieved.
7.3 Mix Design and Concrete Mixing
The design of the concrete mixes, including recommended amounts of admixture and water to be used in the mixes shall be done prior to concrete mixing. At least one month prior to the commencement of concreting operations a trial batch of concrete will be prepared complying with the recommended design mix, and prepare a set of at least five concrete test specimens. The trial batch shall produce average concrete cylinder strength at twenty-eight days after casting of not less than 20 N/mm2. If this design strength cannot be achieved, the design mix shall be done to satisfy the required concrete strength.
Mixing of concrete shall be done by machine mixing. Weight batching or volume batching may be taken up.
8.0 CAST CONCRETE BLOCKS
Cast Concrete block (CC block) is a revetment material constructed with a specific proportion of mixture of sand, cement and coarse aggregate to a specified size and strength after 28 days of curing.
Here we (SINAMM) delineate an anecdote of CC Block manufacturing and curing process, the handling and storage of blocks and the tracking of blocks. This includes the method used for the casting of the blocks including the size of area required for the casting, how curing shall be undertaken considering the expected daily volumes, and how blocks will be moved between curing, stockpile and loading areas in considering of the minimum curing time requirements. Blocks shall be cast or placed after casting on an evenly surfaced platform of brick soling and sand cement blinding or equivalently smooth surface.
The contract requires the construction of the cast concrete (CC) blocks in the river bank and placing of 13.425 million of blocks of different sizes.
8.1 Workmanship Requirements
Concrete blocks shall be manufactured using the concrete specifications of the Contract. In manufacturing we shall ensure that the blocks comply with the following workmanship requirements.
All concrete blocks shall meet the minimum density requirements.
Concrete blocks shall have smooth finished surfaces and sharp square edges. Plastering will not be acceptable.
During casting of the blocks, vibration shall be used to consolidate the concrete.
Shutters or formwork used in the casting of the blocks shall not be opened or removed until the concrete is sufficiently hardened to avoid damage during form release and handling.
Curing shall occur for a minimum of 7 days, protecting the surface from the effects of sunshine and drying winds by covering the block with hessian cloth or similar absorbent material, and keeping it constantly moist.
Handling of concrete blocks shall not be allowed before 7 days of curing strength has been reached.
Blocks shall not be moved to other stockpiles until they have been cured for at least 7 days. They should be stockpiled by casting date and in measurable stacks. The stacks shall not contain more than 6 layers.
A set of concrete blocks shall be selected by the Engineer from the first batches of blocks produced which will be used for reference purposes in defining the acceptable quality from visual inspection.
Concrete blocks containing cracks, broken edges, honeycomb or protrusions in excess of the approved standard reference blocks shall not be accepted, and must be removed from the site.
8.2 Block Dimensions
Concrete blocks shall be made to the dimensions shown on the Drawings:
400 x 400 x 200 mm
400 x 400 x 300 mm
400 x 400 x 400 mm
600 x 600 x 600 mm
The subcontractor may, subject to the approval of the Engineer and the Contractor, modify the geometry of the block slightly to facilitate its handling and placing e.g. by incorporating cylindrical holes or horizontal recesses. We shall, at our own cost, ensure that the finished weight of the block is the same as that of the blocks shown on the Drawings by adjusting the linear dimensions of the block accordingly.
8.3 Equipment for Batching Plant
The list of Equipment to be deployed in CC blocks manufacturing works shall include:
Batching Plant, 50 m3/hr productions with silos and all other accessories complete - 4 nos.
Pay Loaders for pouring to storage bins - 4 nos
Generator of adequate capacity – 4 nos
Transit mixer – 6 m3 capacity – 12 nos.
8.4 Materials for CC Blocks
Materials for casting Cast Concrete (CC) Blocks shall be supplied as per Technical Specification and after approval of concern authority.
Portland cement - Type I complying with ASTM C150 or other equivalent standards
Fine aggregates shall be uniformly graded from 3/8-inch (9.5 mm) to fines, washed clean in accordance with ASTM C 33.
The coarse aggregate will be 19.0 mm downgraded stone chips (ASTM C33).
Water for concrete and for curing shall potable, clean and free from oil, acid, alkali, organic or other deleterious substances and shall conform to ASTM C94.
8.5 Batching Plant
Four nos of batching Plant each with capacity of 50 m3/hr will be installed; 3 nos at south bank and 1 no at North bank. Approximate area for installation of each batching plant will be around 5000 m2 which includes storage areas of Aggregates for uninterrupted production of concrete at least for 5 days. Each plant will be operated by Diesel generator set to get an uninterrupted power supply for concrete production for a period of 600 effective days. Period considered is around 2 years from date of inception of land availability. All the four plants will be made accessible by Temporary Road for transportation of materials by Truck.
Each plant will have 3 nos. of Transit mixer for carrying concrete to the Block production yard. All the materials used for block production will be tested and submitted to HDEC/Employer for approval. After approval of materials mix design is submitted and trial mix is produced in the laboratory to achieve the desired strength of 20 N/MM2 at 28 days by varying the water cement ratio and cement content. From different trial mixes the economical and best fit trial mix will be selected for making concrete production. One no. of Tube-well will be installed at each yard for water which is to be used for concreting and also for use by the personnel. All four plant sites will be substantively fenced by concrete post and barbed wire fencing with lighting provisions.
Equipment in 4 nos batching plant area shall include the following items:
Batching Plant – 50 m3/hr productions with silos and all other accessories complete 4 nos.
Pay Loaders for pouring to storage bins 4 nos
Generator of adequate capacity – 4 nos
Transit mixer – 6 m3 capacity – 12 nos.
8.6 Casting Yard Area
The casting yard will be 14 nos for producing blocks of around 13.425 million of blocks. The area required for each yard is around 13,050 m2 for having around 22500 nos of blocks which is produced in 8 days' time plus curing period of 7 days. The size of yard would be linear size of 45mX260m having 64 nos of blocks per column and 352 nos of block in rows.
Hence total casting yard area to be procured along the river bank – 50m x 300m x 14 nos = 210,000 m2 for a period of 2 years to cast 13,425,000 nos of blocks of different size.
Please note that, each casting yard will produce around 1925 nos of blocks per day of different size to produce 13,425,000 nos of blocks in 500 days' time effective from period of 600 days. From the total of 58,500 formworks each yard will be allocated around 4180 nos of formwork sets to produce 22,375 nos of block per day, which will match the schedule of works.
Each casting yard will be administered by our engineers and foreman assisted by 100 nos form workers and concreting labors of around 60 persons for producing 1925 nos of blocks per day. Release of formworks will be done after 24 hrs of concrete placing and water will be spread over hessian cloths for curing for the period as per requirement (Min 7 days in the casting ) and another 7 days in stock yard. In each casting yard one Tube-well will be installed for curing water.
We will provide one no of 12mm dia rebar of appropriate shape which will be used as hook for lifting and placing the blocks properly in the stack yard. We will use the diesel vibrators for vibrating the concrete in the forms at the time of concreting.
Please note that, we will make roads around the periphery of casting yard for movement of Transit Mixer for concreting and excavators for lifting of blocks.
8.7 Storage Yard
The location of the storage yard should be along the river bank to minimize the carrying distance as far as practicable. From the drawing (Land acquisition), it is seen that around 100m to 150m width is available if possible we will use those areas for storage yard of CC block. Area required for storage will be around 550,000 m2 if we stack in 6 layers of block (as specified in specification). The yard is paved with BFS and mortar over the top for receiving the blocks.
The prepared blocks from casting yard are removed by excavator with an attachment made of steel I beam 8m to 9m long with S hooks for lifting each block, these "S" hooks will be engaged/attached with the previously placed hook in concrete blocks and the excavator will lift 10 of them at a time and move to stock yard area and place them in proper position by engaging manpower to place it in proper manner.
8.8 Fabrication of Formwork
The required nos of formwork sets (as mentioned in BOQ item 2.3) will be made of 40mm x 40mm x 6 mm Angels and 3mm thick sheet. Each form will be joined by 2 or 3 sets of wedge pins within the slotted punches in the angle frame for ease of releasing and hence increase of productivity. Each set will be used around 230 times for having the productivity of 13, 425,000 nos. of blocks. All these formwork will be fabricated in factory in an approved manner and a small workshop will be set for repair and maintenance at site. Appropriate releasing agents will be used before casting of each block. As mentioned before around 100 Form workers per yard will be required to have a productivity of 1925 blocks per day per yard.
8.9 Fabrication of Formwork
The subcontractor will maintain a register recording the total number of blocks cast each day, for each block size and casting plant, together with the signature of Engineer's and Contractor's representatives. Blocks will stockpiled by date of manufacture and we will maintain a map of the stockpiling yard that is updated daily, showing the location of each day's production. The map will be available to the Contractor's Engineer on demand.
9.0 IN-SITU CONCRETE
Some RTW items need placement of concrete in situ. These areas are as follows:
Construction of an anchor beam on the land side of the berm at elevation -2.4 m needs in-situ concreting. Anchor beam will be of reinforced concrete and be cast-in-situ.
Concrete will also be used for the filling of gaps where less than a full block is required in the revetment.
The Works also include the filling of voids in a portion of the area where CC Block dumping will occur.
The concrete used for these purposes will be of the same as that specified in Clause 2.4, having a minimum 28 days compressive strength of 20 N/mm2 (cylinder strength). The placement of concrete in these locations shall not occur underwater, unless otherwise accepted by the Engineer.
It may become necessary to modify the properties of the concrete used for filling of voids of dumped concrete blocks depending on a trial test. The trial test will be conducted jointly by Engineer and Contractor and, based on the degree of joint filling the concrete properties might be modified.
10.0 BRICKS
10.1 Areas of Brick Use
Bricks have been specified for the paving of road surfaces.
As a protective layer between geotextile and dumped CC Blocks, bricks shall be used.
Bricks are specified for the lining of the drainage channel on the north bank.
Bedding layer for CC blocks will have broken bricks beneath.
10.2 Sources of Bricks
Sources of bricks shall be proposed by the Contractor to the Engineer for his written approval. Not more than 4 No. different sources will be approved for simultaneous production. Bricks shall be produced and tested in batches or lots.
10.3 Type and Usage
Bangladesh standards are available for the grading of bricks and specifications. The specifications below reference the Road and Highways Department publication Standard Test Procedures (May 2001). Bricks utilized for the road surface are to be produced by gas firing and are to be of the highest quality locally known as "over burnt bricks" (OBB). These will be Grade A bricks that have been fired longer or at a higher heat. The specified size is 75x125x 250 mm. However alternative sizes may be proposed by the Contractor with the appropriate changes made to the sectional design without changing the thickness of the bedding material.
The bricks utilized in the protective layer between the geotextile and dumped blocks on the upper portion of the slope protection are of Grade A quality. These bricks are to be broken into pieces of approximately 75x125x125 mm size and can be either the same bricks used in the road construction which have been broken in half or the Contractor can arrange for this size to be manufactured.
Bricks that are deformed, broken or cracked shall not be utilized in the construction of the road surface and channel lining. Deformed and portions of broken bricks of the highest quality that are larger than half the original size may be redirected for use in the protective layer.
Brick Chips are specified in the bedding or sub layer for the construction the driving surface on the embankments. The Chips are to be 25 mm downgraded made from Grade A or B bricks.
All deliveries of bricks will be inspected by the Engineer and no unloading or stockpiling can occur without the consent of the Engineer. The Contractor will provide the Engineer with at least 2 days' notice of the expected delivery of bricks.
11.0 OPEN-CELLED CONCRETE PAVERS
Open Cell Concrete Block is one solution- concrete paving systems designed to take the load yet with enough open space that water can drain and grass can grow.
Open-Celled Concrete Pavers are to be utilized in the surface treatment on either side of the road along the crest of the protection works and the north bank drainage channel/swale.
Drawings of the channel/swale detail referred to these as Gobi/GB Blocks, which are proprietary products. The Block is a heavy-duty paved surface that is up to the task for high-traction requirements. Open Cell Concrete Block is one solution- concrete paving systems designed to take the load yet with enough open space that water can drain and grass can grow. It is ideal for places to retain a semi-grassed look; as the design allows grass to grow through, and water and nutrients to flow to root systems below. But the Contractor shall supply equivalent alternatives acceptable to the Employer. The pavers shall be of an interlocking type with maximum openings of 45 cm2 or equivalent void ratio of approximately 30%.
The pavers are to be manufactured, as a minimum, to the same specifications as the CC Blocks.
12.0 LAND RESTORATION AND VETIVER PLANTATION
Bank protection works may be classified as direct and indirect. Direct protection works includes work done on the bank itself such as providing vegetal cover, pavement, revetment, grading of slope etc. Indirect protection of slopes includes works constructed not directly on the banks, but in front of them for reducing the erosive forces of the current, either by deflecting the current away from the banks or by inducing silt deposition near the bank.
In the case of strong current, banks may be protected by pitching using stone/boulders, concrete blocks, sand filled geo-bags/geo-mattress. The bank pitching is provided along with the launching apron to prevent the scouring under the water and the consequent fall of pitching.
Bank can be protected by a vegetal cover using the shrubs and willows. Sometimes a special vegetal cover like vetiver can also be used for bank protection. The vetiver is a special type of grass having longer roots of length up to 3 m. These roots have an average tensile strength of 75MPa. This type of grass is a perennial type of grass which can grow under extreme and wide type of conditions. This grass can live up to 5 months under 14 m of water. Due to their long roots and high tensile strength this grass is resistant to the high velocity streams and checks the erosion.
The river bank before and after the implementation of vetiver is shown in Image 12-a and 12-b.
Image 12-1 : Vetiver not planted – Erosion occurring
Image 12-2 : Vetiver planted on the Riverbank
13.0 PERMANENT WORKS OF RTW
Permanent works include all preparations, excavation and construction/placement of materials to the lines, grades and elevations as per these specifications or identified in the Tender drawings.
The Works will include:
1. Land Clearing and Preparation
2. Excavation or Fill
3. Ground Treatment works (Provisional Item)
4. Placement of Protection Treatments
5. Final Dressing of the Site
6. Ancillary works, such as the installation of mooring bollards, boundary pillars
.
13.1 Containment Bunds
Hydraulic fill material is anticipated to be used for both Temporary and Permanent Works. The Temporary Works may include the construction of a temporary guiding bund along the south bank to allow the Permanent Works to be constructed in a current-free environment. The Permanent Works include construction of the body of the guiding revetment, and the upstream and downstream end treatments on both the north and south banks.
To retain the placed hydraulic fill material, containment bunds will have to be provided prior to filling.
As the water level will vary during the construction period, the height of the containment bund and number of steps will vary. The Contractor shall determine the size and shape of the containment bunds based on the material to be used and his accepted Method Statement. The Contractor shall be solely responsible for the stability of the outer slope of the containment bund during placement of the hydraulic fill.
The Contractor shall use materials for the construction of the containment bunds that have been approved by the Engineer. The Drawings indicate that the berm at the upstream and downstream end treatments on both the north and south banks is to be constructed using 125 Kg geobags. The geobags are intended to ensure that fines from the hydraulic fill cannot migrate through voids in the containment bund. These geobags are required to meet the specifications as outlined in Tender Document. The Contractor shall conduct slope stability calculations for containment bunds, the berm, and any hydraulic fill under water that comes in contact with the Permanent Work to demonstrate that containment bund, berms, and fill material are geo-technically stable during construction and thereafter and that no slope failure can occur that negatively impact on the slope treatment (protective works)/
13.2 Revetment Construction
The revetment shall be constructed to the lines, grade and dimensions using the materials indicated in the Drawings. The revetment zones and the materials to be used in the construction as indicated in Figure A are:
i. Lower Slope
a. Launching Apron – (800 kg Geobags)
b. Slope Protection – (800 kg Geobags along approach road on south bank, or 125 kg Geobag Filter under Rock Rip Rap)
ii. Upper and Embankment Slope (Sand and Geotextile Filter, CC Blocks)
iii. Low Water Transition - (Sand and Geotextile Filter, Half Bricks, CC Blocks)
13.2.1 Lower Slope
The lower slope is considered to be the portion of the revetment below elevations -2.4 m PWD and consists of the launching apron and slope protection. There are three (3) different regions of treatments for the lower slope which are referred to as Areas A, B, and C.
In Area A, 800 kg geobags are the only material used in the construction of the launching apron and slope protection. In Areas B and C, the apron is to be constructed using 800 kg geobags and the slope protection consists of 125 kg geobag filter overlain with rock rip rap. A further difference between Areas A, B, and C is the launching apron width and depth.
In Areas B and C, the 125 kg geobags are placed on the slope to form a filter layer under the rock.
There is a small region on the lower slope just before the lower water transition zone where the design requires the placement of geotextile under the geobags.
a. Launching Apron
The launching apron, consisting of 800 kg geobags is to be placed at the toe of all dredged slopes. The dredged surface elevation prior to placement of the geobags varies from -12 m PWD to -25 m PWD and the width varies from 35 m to 65 m.
The minimum thickness of the apron shall be five (5) geobags. The bags will be made using 600g/m2 non-woven geotextile.
Care will have to be taken not to place excess bags in the launching apron that results in an undulating surface which could stimulate turbulence and river scour. Locations where the placed thickness is more than 125% of the design thickness will need to be rectified. Surveys shall be undertaken prior to and after the placement of the geobags to determine placement thickness and volumes.
After construction of one section, the river could erode the adjacent area and the apron could start to launch. If this happens and a certain threshold is surpassed (10 to 15 m vertical depth) the Contractor shall upgrade the launched slope to full thickness (adding three layers of geobags) and place a second 25 m wide apron in front of the launched slope during the next dry season. The upstream and downstream apron transitions would need to be reinforced with a single layer of geobags allowing some settlement during subsequent erosional attack and as such avoiding discontinuities in the protective levels.
b. Slope Protection
Area A – South Bank:
Four layers of 800 kg geobags shall be dumped on the underwater slope which extends from -1.0 m PWD down to the launching apron (which varies from -15.0 PWD to -20 m PWD).
Care will have to taken not to place excess bags on the underwater slope resulting in an undulating surface that stimulate additional turbulences and scour. Locations where the placed thickness is more than 150% of the design thickness shall be rectified by the Contractor at his own cost.
Surveys will be undertaken prior to the placement and after the placement of the geobags to assist in determining placement thickness and volumes.
Areas B and C – North and South Bank To ensure full filter protection, minimum three layers of 125 kg geobags shall be dumped on the underwater slope which extends from -2.4 m PWD down to the launching apron (which varies from El. -15.0 to -25 m PWD).
The 3 layers of geobags will be overlain by a 0.9 m (minimum) thick layer of dumped rock riprap.
Care will have to taken not to place excess bags on the underwater slope or excess rock riprap on the geobags that results in an undulating surface which could stimulate additional turbulences. Locations where the placed thickness of a material (geobags or rock riprap) is more than 150% of the design thickness will need to be rectified by the Contractor at his own cost.
Surveys shall be undertaken prior to the placement of the geobags and after the placement of each material to assist to confirm placement thickness and volumes.
13.2.2 Upper and Embankment Slope
On the north bank and the south bank in Areas B and C, the upper slope includes the embankment and extends from elevation +2.5 m PWD to +9.0 m PWD (excavation/fill elevations). At elevation 5.6 m PWD, there shall be a 3 m wide (excavation width) berm/bench which delineates the boundary between the upper slope and embankment. On the south bank within Area A there is no embankment. The upper slope starts at +2.5 m PWD on the riverside and on the landward side the elevation is dependent on the local ground elevation.
The river side boundary of the upper slope is the Anchor Beam. The anchor beam provides a stable reference for the placement of the concrete pitching. The Drawings show a 1000 x 400 mm cast in situ reinforced concrete wall partially buried in the excavated surface with geotextile filter material under it (no sand bedding). The concrete used in the anchor beam is to be the same as that used in the construction of the CC Blocks with construction joints placed at a maximum separation of 10 m along the length, with the reinforcing steel passing through the construction joints.
The Contractor may provide an alternative design acceptable to the Engineer such as 10 m long interlocking pre-cast reinforced concrete segments with the same sectional dimensions.
The anchor beam shall have to be constructed prior to finishing the landward portion of the Low Water Transition. Excavation of the trench required for the construction/placement shall be backfilled in accordance with filling specifications.
The geotextile filter from both ends shall end at the Anchor Beam and seepage water shall pass through a strip drain and drain holes in the anchor beam to the lower slope.
The upper and embankment slope protection consists of CC blocks overlying a geotextile filter. The manner in which the CC Blocks are placed is referred to as "Pitching". All components of the protection shall be placed on even and smooth ground. The surface of cut areas shall be lightly compacted before placing the filter consisting of sand and geotextile material. The placement of the geotextile is addressed in Clause 3.5.7. A 100 mm thick layer of sand will be placed over the excavated surface which shall be trimmed to an even finish so that when the geotextile underlayer is laid, it is in full contact with the slope.
Concrete block pitching shall be used for all upper and embankment slope protection above an elevation of +0 m PWD. When required, the embankment from El. +9.5 m to +5.6 m PWD shall have a slope of 1V:6H and be made up of 400 x 400 x 300 mm and 400 x 400 x 200 mm concrete blocks.
The lower slope from El. +5.6 to +0 m PWD shall have a slope of 1V: 6H and be made up of 400 x 400 x 400 mm and 400 x 400 x 300 mm concrete blocks. The berm at elevation 5.6 m PWD shall be covered by 400 x 400 x 300 mm blocks.
Placing of blocks on the upper slope of riverbank shall start only after the Low Water Transition protection and Anchor Beam have been completed and the blocks shall not be placed in the works until at least twenty-eight days after casting and proper curing has been done, or until the specified strength has been attained for the anchor beam.
Blocks shall be laid parallel to the direction of the river flow as per Drawings on the geo-textile filter.
The blocks shall be laid in a manner so as not to damage or displace the underlying sand filter and geo-textile. Any damage caused to the filter during placing of the blocks shall be repaired by the Contractor at his own cost and to the satisfaction of the Engineer Concrete blocks shall be laid with the down slope joints staggered. The blocks shall also be placed with alternating rows of blocks at different heights, to produce a pattern of projecting blocks that are efficient in dissipating wave energy. The blocks shall be accurately cast with smooth, parallel faces, such that when placed together they leave gaps of less than 10 mm. The gaps are to be filled up with stone pea gravels of 6mm down, graded and mixed with coarse sand, or alternative material approved by the Engineer.
On the embankments, the slope protection will be carried around both the upstream and downstream noses and extend along the landside of the structure for the distances shown in the Drawings. The alternating of blocks heights will be carried around the noses of the embankment. For the remaining length running parallel to the river side face, 400x400x400 mm blocks will be utilized to create a smooth surface.
Placed in-situ concrete shall be used to fill all gaps in the finished surface and to facilitate a continuous surface at locations where there is a transition in slope or block alignment. Typical areas are the transitions between the berms and sloped faces, the sloped faces and top of the embankments or crest protection, entrances to the offtakes, and slope transitions within the offtakes.
In order to create robust and stable transitions, CC-Blocks may have to be eliminated in an alternating pattern along the transitions with the void filled with the concrete. Such details shall be confirmed by the Engineer in consultation with the Contractor.
Blocks to be used in the Works from any stack or stacks will be counted, at the beginning of each day's work, by the Engineer's representative. After each day's work, any unplaced blocks in the counted stacks will be recounted and the net number of blocks used in the day will be recorded in a register, and signed by the Engineer's representative and the Contractor.
Any settlement or sloughing of the protective layer prior to the end of the Defects Notification Period shall be remedied..
13.2.3 Low Water Transition
The low water transition is considered to be the portion of the revetment between elevations +2.5 m and -2.4 m PWD, separating the Lower and Upper Slopes. The landward boundary of the treatment is an Anchor Beam that forms the start or lower boundary of the Upper Slope protection.
The protection consists of a geotextile which is overlain by a layer of half bricks and topped with CC Blocks. The geotextile is to be placed on either a sand sublayer or directly on the prepared surface as indicated below.
The placed thicknesses are indicated in the Drawings.
Most of the construction of the Transition region will have to be performed in water. The excavated ground within the region, which will have been trimmed to a uniform elevation or slope, is to be lightly compacted prior to the placement of the protection materials. As the majority of this is be performed underwater, the compaction can be performed using means similar to applying weight on the surface using the "cleaning" bucket of a large excavator.
Between elevations +2.5 m and +1.5 m PWD, the prepared excavation surface shall be covered by a sand sub layer (100 mm thick) prior to the placement of the geotextile.
Below elevation +1.5 m, the geotextile shall be placed directly over the prepared slope. The Contractor should note that a portion of the sand sub layer placement may have to be performed underwater, depending on the time of the working season. The Contractor shall adjust the placement procedures according when placement is performed underwater to ensure the specified thickness is achieved.
It is to be ensured that the geotextile is in full contact with the sand or prepared excavation surface prior to the placement of the protection materials. On the river side of the low water transition, the geotextile will extend under the geobags in the lower slope protection for 2 m (horizontal distance) and on the landward side, it will continue under the upper slope protection.
A layer of broken bricks with a thickness of approximately 0.2 m or approximately 100 bricks per m2 shall be placed over the geotextile. The placement can be done in a random or systematic manner as the purpose is to protect the geotextile from damage. See Clause 3.5.7 for details on the placement of the geotextile filter.
The CC blocks shall be placed by machine or hand in a random fashion to achieve a minimum thickness of 1.3 m (minimum 12.5 Nos. of 400 x 400 x 400 mm blocks per m2). The blocks will cover 2 m of the lower slope protection and extend landward to the Anchor Beam. The dumped CC Blocks (and half bricks) will cover the excavated slope between +2.5 m PWD and approximately -2.5 m PWD and the Lower Slope protection between -2.5 m PWD and approximately -2.8 m PWD (excavated slope elevations). The thickness and layout of the dumped blocks is indicated in the Drawings. When dumping the concrete blocks, the Contractor shall take all necessary measures to prevent damage to the underlying geotextile material (geotextile filter and geobags).
Concrete shall be placed within the voids of the CC Blocks from the Anchor block into the river for 5 m as indicated in the Drawings. The concrete is to be placed through almost the entire thickness of the blocks such that the blocks are held together in a solid mass but the surface of the blocks remains rough.
13.2.3 Installation of Geotextiles
Geotextiles are required to provide an underlayer filter to the various slope protection (revetment) systems. Installation shall be handled in the following manner:
The underlayer separates the revetment from the foundation material, allowing the passage of water but resisting movement of the fine soils which make up the bed and banks of the river.
The geotextiles shall be installed as described in this Specification, in the positions and to the lines and levels shown on the Drawings. Concrete blocks shall be laid on a 400 g/m2 non-woven geotextile underlayer.
The method of installation shall not impose stresses or strains likely to cause damage to the geotextile. In this context, damage shall mean significant change in the specified properties, and/or puncturing or tearing of the fabric. The geotextile shall be free of folds and creases after placing.
The method of installation shall ensure that the geotextile is in continuous contact with the surface on which it is placed, without stretching or bridging over humps or hollows.
When the revetment material is being placed on the geotextile, it must be done in such a manner as to avoid the risk of the fabric being punctured or the overlaps being displaced. In particular, the Contractor shall limit the height from which CC blocks are dropped onto surfaces that have geotextile.
All areas where CC blocks are to be placed over geotextile will have a layer of Half Bricks placed on top of the geotextile. The Half Brick thickness shall be 200 mm.
There are no restrictions for rocks dropped through water, but the rocks shall be released as close to the water surface as is practical.
For above water work or in water depths less than 1 m, concrete blocks shall be placed rather than dropped on to the geotextile and the Contractor will ensure that the geotextile is not damaged during placement.
When geotextiles are placed under water, we shall demonstrate that method of placing shall achieve the quality of construction required by the Specification. Underwater diving inspections are expected to be regularly performed during construction.
In particular, installation shall ensure that:
minimum overlaps are maintained or adjoining sections are sewed to avoid overlapping
2. rocks are not placed between overlapping mattresses
3. geotextile is in contact with the foundation material
4. if utilized, fascines remain firmly connected to the bamboo lattice after sinking
Overlaps between geotextiles shall be sufficient to ensure that the filtration function of the geotextile is not compromised during the placing of the revetment. Overlaps shall be 0.75 m minimum when placed on land and 2.0 m minimum when placed in water. Where possible, it is recommended that adjoining sheets of geotextile are sewn together to eliminate or reduce overlapping.
Installation of the geotextile filter should proceed from downstream to upstream so that the upstream mattress overlaps the downstream one. This should help ensure that a strong river current does not displace the overlapped fabric before revetment is dumped on top.
The Contractor will have to monitor tidal influences and potential reverse flow when placing the geotextile filter.
13.2.4 Transporting and Dumping of Revetment Material
Equipment for Land-based operations:
dump trucks,
bulldozers,
wheel loaders,
excavators, and
wire-rope cranes or draglines.
Equipment for Water borne operations:
(for transport and direct dumping of revetment material)
pontoons with excavators or wheel loaders,
crane barges equipped with rocks trays,
split-hull barges and
side stone-dumping vessels.
It is likely that much of the sand, aggregate, rock riprap material will be transported to the Site by river, rather than by road. Transportation and dumping activities must fully comply with all national and international maritime safety regulations and with all Bangladeshi land and water safety standards.
Suitable Anchor
Suitable Anchor arrangements for vessels etc will need to be provided during dumping operations.
a. Preparation of Anchor Arrangements
Anchoring arrangements for vessels etc shall be capable of securing and positioning the dumping vessel, using bollards or winches. The Contractor shall also provide necessary lifting arrangements to place and salvage anchors. Anchors shall be positioned either on land or beyond the riverside launching apron, so that they do not displace revetment material during anchor placement or salvage. The Contractor shall provide all equipment, manpower, machinery, spare parts, etc. necessary to operate and maintain the anchor pontoons and land based arrangements during the entire duration of the works..
b. Dumping Aids
Dumping method should ensure that it is appropriate for all anticipated river currents and water levels. The correct volume of revetment material shall be dumped at the correct location to form the desired uniform coverage along the entire underwater area. This may require dumping aids in locations with strong currents or tidal influence.
Dumping aids may reduce flow velocities under the dumping vessels and thus reduce the displacement of dumped revetment material. Alternatively, the dumping aids may guide the revetment material to the bottom of the river (for example using a tremie system).
Dumping aids could lead to increased loads on the anchor arrangements and must be taken into account when designing the anchor system.
c. Dumping in Deep Water
The quality control measures used for transporting and dumping of all types of revetment material shall be identical in principle, unless otherwise specified. The revetment material may include rocks, concrete blocks or geobags.
Dumping must take into account displacement/dispersion of the material/objects by current. Field experience is required to assess the displacement and the ultimate location of the revetment material on the slope and bed.
The objective of the dumping operation is to evenly distribute revetment material over the entire revetment area. Dumping vessels must be accurately positioned prior to dumping to ensure excess placement is minimized.
At no time will anchors be positioned on the slope protection or within the limits of the dredged area unless it has been backfilled with sufficient material (sand) such that there is no possibility that the Works can be damaged.
Volume of rock shall be measured, or the number and size of concrete blocks and geobags shall be counted and registered prior to dumping. The registry shall also include details such as the location of the pontoon, the date and time, and water level and velocity.
The dumping coverage is to be continuously checked using the post-work bathymetric survey and the diving inspections. Any areas with gaps or non-uniform coverage shall be filled with additional revetment material, at the Contractor's own cost.
d. Video Recording
A comprehensive system of video recording will also be performed during each dumping operation to document, and to monitor and improve quality procedures. The video recording should be done from the land using a tripod, and with a complete view of the entire dumping operation. Both the date and time must be displayed on all video recordings together with GPS coordinates if possible.
At the end of each day, the video recordings will be attached to the site register book, certified by the Engineer and Contractor.
13.3 Crest Protection
The crest protection portion of the Works is intended to provide a driving surface suitable for light vehicles and weather protection on the embankments (Areas B and C – north and south bank) and protection from over bank flow on the banks above the upper slope bank on the south bank (Area A). In all locations, a geotextile filter has been specified.
a. Embankments
Two treatment configurations are specified for the embankments. At the upstream and downstream noses of the structures the crest protection consists of CC Blocks overlying a geotextile/sand filter layer. The block size is to be 400x400x400 mm and the sand layer below the geotextile filter is to be 100 mm. Between the treatments at the noses, the crest protection shall include a driving surface; constructed of bricks arranged in a herringbone pattern, flanked by open-celled concrete pavers.
Open-celled pavers shall be filled with top soil material (large organics removed) that has been stockpiled during the stripping of the site. Upon completion of the crest protection construction, native grass shall be established over the areas covered by the open-celled pavers. Inland from the end of the pavers, Vetiver (a native plant with long/deep root system) shall be planted at 0.15m spacing.
b. Top of Banks (Area A)
Apart from the offtakes, the top of the banks in Area A will be protected by CC Blocks placed on a geotextile filter and sand layer. The elevation and width of the crest protection varies as the excavation follows the general ground elevation. The sand layer is to be 100 mm thick and the geotextile is to be a continuation of that placed in the construction of the upper slope of the revetment.
Two sizes of blocks have been specified for the crest protection. Near to the upstream end of the embankment a thicker layer (larger blocks) is required. After placement of the CC Blocks, the gaps are to be filled in the same manner as the upper slope protection and then the landside shall be back filled with top soil (stockpiled during the stripping of the top soil).
Upon completion of the protection construction, a 50 m wide strip covered with Vetiver, a native grass shall be established from the landside edge of the protection, inland.
13.4 Offtakes
Five offtakes are included in the Works. The size and geometry (alignment) vary with location but all are the same basic configuration. Details and parameters for each of the offtakes are provided in the Drawings. All geotextile will be underlain with a 100 mm thick layer of sand and placed according to specifications.
It should be noted that the excavation and placement of materials in the central region of these offtake structures will take place in the wet. For the placement of the geotextile, a fascine may be required and/or ballast may be required to lower the material onto the bed.CC Blocks shall be placed manually in such a manner that the underlying geotextile is not damaged or punctured. Any damaged geotextile will be repaired or replaced.
Material removed during the excavation for construction can be used for backfilling as long as it complies with relevant environmental conditions. Placed in-situ concrete shall be used to construct or finish all transitions in slope where the CC Blocks are placed flat (pitching).
13.5 End Treatments
End treatments consist of the construction of a Berm across the dredged trench and the filling of the trench remnant on the landward side of the berm at all noses of the revetments and embankments. The berm is to reestablish the original bankline and to add additional reinforcement to these areas as per drawings.
Berm is to be constructed of 125 kg geobags. The placement of the bags shall be with a 1H:1V slope. This is the steepest slope. The area filled inland of the berm is to be filled to the original ground elevations using dredge sand. The sand may be dredged and placed directly into the area. The filled area will be planted with Vetiver after the Contractor and Engineer have determined that no significant settlement will occur.
The Contractor shall backfill against the berm on the river side with dredged sand. The slope of the backfill will be the natural angle of repose. In the design, a nominal angle of 1V:6H has been indicated. For upstream treatment on the north bank, additional surface protection is to be added to the top of the fill on the landward side of the berm.
13.6 North Bank Drainage
The design for the north bank calls for the construction of a drainage system on the landward side of the embankment. The system will consist of two channels/swales and the sloping of the surrounding ground to direct run-off into the channels. Both channels originate near the bridge alignment. One on the upstream side of the alignment will drain towards the upstream end of the embankment and around the upstream nose over the end treatment into the river. The channel on the downstream side of the alignment will drain downstream over the end treatment into the river.
Where the channel/swale is excavated in original natural material, the ground shall be compacted prior to the placement of the lining material. Where the channel is formed or excavated in fill, a 100 mm layer of sandy loam will be placed on the cut surface and compacted prior to the placement of the lining material. The channel/swale shall be lined with open-celled concrete pavers.
14.0 WORK PLAN
We include a detailed Gantt chart of all tasks with their start and completion dates, plus all resource requirements. The Program identifies subcontractor's tasks that are on the critical path, and also includes non-critical tasks and milestone of the project.
Gantt chart is annexed as Appendix 1.
15.0 PROJECT PERSONNEL
We shall deploy highly experienced technical key personnel for the project rendering project management, technical superindence for the project. We are adding a list of workmen by category as well.
List project personnel is enclosed as Appendix 2.
16.0 QUALITY CONTROL PLAN (QCP)
Our firm – SINAMM is renowned construction firm of Bangladesh. We have carried out activities with reputation. We never compromise with quality. WE have an established QCP for construction projects. Beside abiding by the stipulation of QC requirements in the Tender Documents for Padma river RTW, we shall render services as per our QCP as well.
16.1 Quality System
It is understood the Contractor (Hyundai) shall document and operate a Quality Control Plan (QCP) complying with ISO 9001:2008. SINAMM shall abide by the Contractor's Quality Control Plan (QCP) for the Works. The Quality Control Plan shall specifically address the procedures for maintaining the project quality requirements with respect to the use of subcontractors, vendors and suppliers. The subcontractor shall cooperate with the Contractor and shall provide all necessary access to works and records to enable them to assess the quality system and to audit the implementation of the Quality Control Plan and associated procedures.
16.2 Procedures
The subcontractor shall not commence any item of permanent works until the Contractor has submitted to the Engineer a written statement of his proposed procedure for his own inspections of that item, recording such inspection and obtaining the Engineer's written approval thereof. Each detailed procedure shall be formulated following detailed discussions with the Engineer and Contractor.
Every such statement shall identify the individuals on the Contractor's or Sub-Contractor's staff or Engineer's staff who are responsible for inspecting the workmanship and/or testing the materials for the item in question, the place of inspection, the stages at which inspections and tests are to be made, the detailed aspects to be verified or measured in each inspection. Each inspection shall be recorded.
16.3 Tests and Inspection Records
The record shall identify the Contractor's and Engineer's staff involved, the place, the date and time when the inspection was completed, the section of the Works and the materials tested or inspected, and its state of completion. Reference shall be made to the relevant working drawings and the specific aspects or properties which were checked or measured shall be recorded. One copy of each record of inspection shall be submitted to the Engineer. The records of inspections and tests shall be stored in an orderly fashion on the Site..
16.4 Testing and Inspection
We understand the Contractor shall be responsible for ensuring that all specified testing (in the laboratory, in the field and off site) and inspections of materials and workmanship are carried out. We also understand that no work shall be covered up without the written approval of the Engineer.
All items of work concealed in the finished work shall be inspected by the Contractor and Engineer immediately before they are covered up.
It is intended that the majority of the laboratory testing required will be undertaken in the Engineer's laboratory. Some specialist testing is to be carried out in suitable laboratories off-site.
16.5 Engineer's Testing and Inspection
In addition to the Contractor's testing and inspection described above, the Contractor shall afford and facilitate access at all times for the Engineer's inspection and testing of materials and workmanship. The Contractor shall provide means of access and assistance as may reasonably be required by the Engineer.
16.5 Standards
Certain materials such as geotextile are specified and tested using Eurocode (EN) or ISO standards, while other materials such as aggregate and rock are predominantly specified using ASTM (American Society for Testing and Materials) standards. Except where otherwise specified or authorized by the Engineer all materials and workmanship shall conform to the latest edition of the relevant standard current at the date of Invitation to Tender.
16.5 Proprietary Products
Where a proprietary or brand name or the name of a supplier or manufacturer is indicated on the Drawings or in the Specification this is in respect of items which are not otherwise adequately described by Eurocode, ASTM or equivalent recognized standards. Alternative items based on recognized national standards of the country of origin may be accepted.
16.6 Materials to be New
All materials used in the Permanent Works shall be new unless otherwise specified or agreed to by the Engineer in writing.
No materials to be incorporated in the Permanent Works shall have previously been used in temporary or reclaimed works unless otherwise specified or agreed to by the Engineer in writing.
16.7 Orders for Materials
Before orders are placed for any materials of any description to be used in the Permanent Works the Subcontractor shall submit to Contract who in turn shall submit to the Engineer the names and addresses of the manufacturers or suppliers proposed, together with details of their QA systems. Following approval by the Engineer, the materials will purchased in bulk quantity.
16.8 Samples
In accordance with the provisions of the Conditions of Contract, the Contractor shall as directed by the Engineer supply samples of materials to be incorporated in the Works. The samples required for approval shall be submitted by the Contractor in labeled boxes suitable for storage, and in sufficient time for testing, due allowance being made for the fact that if samples are rejected, further samples and testing will be required.
16.9 Certificates
All manufacturer's certificates of tests, proof sheets, mill sheets, etc. showing that the materials have been tested in accordance with the requirements of the relevant Eurocode or ASTM Standard, other approved standard, or this Specification, shall be supplied to the Engineer/Contractor..
17.0 HEALTH AND SAFETY PLAN
As a subcontractor to Hyundai for the RTW Contract, we shall make ourselves familiar as well with the 'Public Health Action Plan' prepared by BBA for the Padma Multipurpose Bridge Project and implement all recommendations found therein for safeguarding the health of the workers and project affected persons living in the immediate vicinity.
We shall ensure sufficient screening on health issues in the recruitment of workers. Precautionary measures are to be taken against spreading of communicable diseases through information campaigns and orientation aimed at both the Contractors employees and local residents.
The Contractor shall ensure adequate sanitary facilities for all the employees at all construction and camp sites.
We shall take all reasonable steps, including training and safety drills, to ensure that the safety of all persons on the Site, whether in his employment or not, is properly maintained. Appropriate protective clothing and equipment will be provided and maintained for the work to be done and its proper use ensured. Where required, PPE, safety nets, belts, harnesses and lines, shall be provided.
Where work is in, over or near water, life preserving and rescue boats shall be provided. All personnel working over water shall be required to wear life preservers. The Contractor shall provide and maintain in prominent and well-marked positions all necessary first-aid equipment, medical supplies and other safety facilities. Trained personnel will be required to be available at all times to render first aid.
We shall take all reasonable steps including training and drills to ensure the safety of all project related personnel on the site at all times promote the merits of safety awareness.
The Safety Plan shall address the following issues:
The organizational structure through which all construction safety issues will be implemented and managed
Health and safety risks on the Site
Relevant legal, contractual and other requirements
Appropriate controls and measures to reduce safety risks to an acceptable level
Requirements for monitoring, recording, communication and reporting
Specific induction and training needs for Contractor's personnel working on the Site
We shall inform the contractor regarding any accident at site; the Contractor shall report to the Engineer promptly and in writing particulars of any accidents or unusual or unforeseen occurrences on the site, whether likely to affect progress of the work or not.
In fine, we will look after following factors at the site in order to ensure Health & Safety at the site:
Only competent operator can operate all heavy equipment.
Competent lifting personal to oversee all lifting jobs.
All personnel shall wear proper PPE in line with their respective job.
Jobsite security shall be posted during working hour and non-working hour
Access permission shall be obtained from HYUNDAI, the work area for access to SINAMM stating conditions & purpose of access, inclusive of topographical & terrace soil compaction results, and highlighting all known existing services and hazards.
Warning sign shall be provided and warning sign shall be written in English
Safety Induction shall be carried out for all before start of the work and necessary safety information shall be circulated and implemented during the execution of the works.
All formwork related to above activities shall be fabricated and erected as designed and to conform to design parameters to prevent the danger of collapse. Safe access to reach the bottom of trench to carryout works and also for inspection purpose.
All work permits (as applicable) shall be secured prior to commencing any work.
18.0 ENVIRONMENTAL ASPECTS
We understand the Contractor shall have to document and operate an environmental management system (EMS). We shall work in strict compliance with the Contractor's principles of the Environmental Management Plan for the Project. No part of the work shall be started, or if defects are found later, continued or restarted before complying with all conditions of this Environmental Management Plan.
We shall remedy any damages resulting from non-compliance of any stipulation in the Environmental Management Plan. All work shall be stopped until compliance is assured.
Air and Noise
We shall regularly spray water on dry surfaces to control any dust problems. We shall regulate vehicle emissions and noise in accordance with current legislation of Bangladesh. We shall avoid unnecessary noise, especially at night.
Land Use
Prior to construction, the Contractor shall remove, and store all topsoil at the construction site. After construction completion, the Contractor shall restore the top soil and surface vegetation in his work areas to the level found before starting the work.
iii. Disposal and Pollution
We shall not dispose of any waste, rubbish or offensive matter in any place not approved. We shall not discharge into any watercourse oil, solids, noxious, floating materials or untreated waterborne effluent, and take reasonable precautions to prevent their accidental spillage, contact with soil or discharge into water course. We avouch here that we shall strictly follow ECP 1: Waste Management in worksite.
We shall take all reasonable precautions to keep public or private roads clear of any spillage or droppings from his vehicles. Any spillage or droppings which occur shall be cleared without delay.
iv. Prevent Pollution from Spills
We shall prevent spills of oil and lubricants from vehicles, engines, etc. Used engine oil must be disposed of in an environmentally acceptable manner, in accordance with the current legislation of Bangladesh.
