Method Statement for Silt Curtain Installation

method statement for silt curtain installation

Description of Works

This Method Statement for Silt Curtain Installation defines the sequence and the control procedures to be followed during its execution on the construction project.

Definitions

CM: Construction Manager
QC: Quality Control
HSE: Health Safety & Environment
PPE: Personal Protective Equipment
PMV: Plants, Machinery & Vehicles
CAT: Cable Avoidance Tool

Reference

Information sources may include, but not be limited to, verbal or written and graphical instructions, signage, work schedules/drawings/specifications, work bulletins, charts and hand sketches, and Material Safety Data Sheets (MSDS).

  • Excavation Specifications
  • Health and Safety Guidelines
  • Silt Curtains as a Dredging Project Management Practice
  • Illinois Urban Manual Practice Standard
  • Revised Material Approval Submission for Supply, Assembly & Installation of Type-II
  • Silt Curtain System
  • MS–Bathymetric Survey
  • Silt Curtain Shop Drawings

Responsibilities

1. Project Manager
Responsible for accomplishing the stated project objectives which include creating clear and attainable project objectives, building the project requirements, and managing the constraints of the project management triangle, which are cost, time, scope, and quality.

2. Construction Manager
Responsible for overall construction activities ensuring that all quality and safety procedures are implemented and required approved permits are obtained.

3. Temporary Works Manager
To support the project delivery teams, to support and lead the management and delivery of temporary works engineering whilst ensuring program, cost, quality, and safety objectives are achieved.

4. Site Engineer
Supervise operations in accordance with the approved Method Statement, shop drawings, specifications, material submittals, and schedules to achieve the acceptance of the project deliverables.

5. Site Supervisor
Supervise closely, the activities designated to them and ensure that all instructions and safety procedures are followed and strictly adhered to.

6. Site Foreman
To liaise with the Site Engineer and Supervisor for the work execution.

7. QA/QC Engineer
Ensure the proper implementation of the quality system and monitor the overall quality of the work is maintained. Conduct inspection and monitor tests. Determine and report any nonconformance and recommended corrective actions. Ensure that all personnel is aware of the quality requirement. Training of relevant personnel. Conduct surveillance and inspection duties at various stages to ensure compliance with QA/QC Plan.

8. HSE Manager
Health, safety, and environmental (HSE) managers generally plan, coordinate and implement issues and directives within the organization. They ensure safe environmental working conditions for all employees.

9. HSE Engineer
Ensure enforcement of safety procedures in accordance with the approved HSE Plan. Will be closely monitoring the site engineer’s strict implementation of the Method Statement for Silt Curtain Installation and Risk Assessment, the use of proper tools and equipment to maintain safety, certifications of equipment and their adherence to safety regulations, reporting of any unsafe work, or stopping work that does not comply with ES&H procedures. Will advise on Health & Safety requirements and monitor the Hazard controls implemented on site as per the Method Statement/Risk assessment.

10. Chief Surveyor
Carry out pre-construction surveys to fix the locations and corresponding elevations as per the approved shop drawings. Ensure quality and compliance during phases of surveying works and the regular checking of the surveying equipment or periodic calibration from third parties. Ensure the validity and the serial number of calibration certificates are available and posted in the survey equipment. Ensure proper safety guarding of surveying equipment. To maintain the records of all surveying equipment handled.

11. Survey Aide
Maintain and use Surveying equipment. Assist surveyors in taking measurements, record measurements manually or electronically, and peg out boundaries.

Interfacing with Other Operations

All activities within the immediate area are to be ceased to ensure emergency access can be maintained for additional equipment and resources.

Duration, Phasing with the Subcontractors

Assembly of silt curtains – 1 day (onshore)
Installation of silt curtains and anchors – 1-2 days
Periodic inspection every month up to 8 months from the date of installation

Resources

Plant and Equipment

Workboats for installation
100-Ton mobile crane
Access ladder
Onboard emergency lifebuoy/life-raft

Note:
All 3rd Party Certificates shall be inspected prior to commencing work.
All machines shall fulfill project requirements if required.

Work Force

Installation team
Boat Operator
Laborers
Foreman
Crane Operator
Rigger

Light Tools

Loose tackles for assembly
Scaffold pipes and clamp
Lifebuoys with 30m PP rope (throw lines)

Materials

  • Warning Signs
  • Curtain, floatation pockets, buoys, anchors, connection gears, skirts, etc.
  • Warning Tapes
  • Pins and Pegs
  • Emergency Kits
  • Concrete Barriers
  • 6mm PP rope for furling

Site Planning

Duration of Works is initially scheduled to be completed within 20 working days.
However, the duration can be indeterminate but not critically affect the program of work.

Preparation

The contractor shall ensure that all gate passes, permits, tools, materials for safety precautions, manpower, and equipment are available before the commencement of work.

The Site Team shall make sure that access roads are always clear from any obstruction and site is always accessible.

Site Clearance

Proper coordination with the authorities shall be done all throughout the activity.

Traffic Management

The Site Team with the assistance of the Safety Officers shall coordinate logistics and materials movement through the site following the direction and road signs displayed on site.

The Work Permits and Operator Certificates shall be compiled and filed for reference by authorized personnel.

The Logistic Department shall be contacted/coordinated regarding all access needed starting from the mobilization of equipment, materials, and manpower at the site.

Details of access from land and marine shall be reflected on the Site Logistic Plan and shall be submitted for approval.

Preconstruction Safety Meetings:

A meeting shall be scheduled prior to the beginning of the work and before any Subcontractor starts on the project.

Safety awareness meetings will be conducted every working day morning/every other day to brief the workforce on the safety prevention measures. The equipment check for safety shall be recorded/ documented during the daily Safety Awareness Meeting.

Traffic safety will be discussed to emphasize these meetings.

Each worker will be instructed to follow specific safety requirements related to his trade. They will be required to follow installed safety signs, observe barricades and use opens.

The contractor safety team will perform hazard risk analysis by identifying all steps, and hazards identified in those steps, with a focus on the relationship between the work task, the tools, and the work environment. After identifying uncontrolled hazards; The contractor will take steps to eliminate or reduce them to an acceptable risk level.

General contractual Safety, Health, and Environmental requirements.

Roles of the contractor, subcontractors, authority representatives, and all project workers.

Accident reporting requirements.

Specific details of the work to be performed along with the use of personal protective equipment.

Emergency procedure.

Operating Procedures:

A site investigation has to be carried out to develop safety precautions and measures prior to the commencement of the work. After such investigation, relevant sign boards will be displayed and barricades will be installed where and as necessary, such as but not limited to the following:

  • The contractor shall ensure that all personnel performing work activities on or within 5 meters of bodies of water are provided with and wearing approved life preservers in addition to all PPE required.
  • Lifebuoys shall be provided for each worker with exposure to drowning. Lifebuoys shall be located on land and be provided with a minimum of 30 meters of the lifeline.
  • All personnel exposed to drowning hazards shall be trained on the use of life preservers and procedures for working near water.
  • Main vessels shall be sea-worthy and used for their intended purpose only. Vessels shall be operated only by trained, qualified operators who are approved by the contractor.
  • Ensure vessels are provided with suitable lifesaving equipment, lighting, communications, and firefighting equipment.
  • Means of adequate and appropriate communication between the vessel and land shall be provided.
  • Vessels are to have occupancy requirements that shall never exceed the manufacturer’s recommendations and the contractor shall ensure these are adhered to.
  • Spill prevention controls and countermeasures shall be in accordance with the HSE Plan.
  • A thorough inspection of marine equipment, tools, and emergency equipment shall be conducted prior to commencing any activity.

Methodology

1 General

Silt curtains are designed to suit almost all conditions. There are a number of different models tailored to suit specific site conditions, requirements, and budgets. As a result, installation and anchoring methods may vary from the generic guidelines below.

The guideline below is for installation from shore for short distances of curtains only; however, it can be easily adapted to installation from a barge or boat.

All works shall be as per approved shop drawings.

1.1 Force

  1. Based on a discharge rate of 2,000l/s per area will exert a force of 4kN/m2.
  2. Type II silt curtain is manufactured with 100kN tensile strength geotextile.
  3. Refer to the Calculation Sheet – Appendix.

1.2 Model: Type II

  1. Further to the analysis carried out in the post-bathymetric survey, for Depth: 4m with the exception of the first 25m panel on each side, where we would recommend a tapered curtain from 2m-4m. This ensures there is minimal curtain sitting on the seabed in the shallower areas close to the quay wall.
  2. Length: 700m to cover the area from North to South Discharge pipe.
  3. Anchoring: 24 units total x 25kg, Danforth Anchors.

1.3 Specification of materials to be used for installation

  1. Floatation pockets – 150 mm dia, closed cell EPS floats with high visibility, reinforce 650 gsm PVC membrane float pockets and 100 kN PE woven geotextile liner.
  2. Skirt – 100 kN PET woven geotextile
  3. Ballast – 8 mm Hot Dipped Galvanized chain
  4. Anchor – 25 kg Danforth Anchors pre-assembled. Typical painter line system comprising of the market buoy, galvanized chain, rope, and shackles.
  5. Tension & Connectors – 2 x 38 mm polyester webbing at the top of the floating pocket and 2 x 50 mm at the bottom. Galvanized steel D-ring anchor plate every 25 m.

2 Sequence of installation

2.1 Connection

For ease of transport and handling, curtains are typically packed and wrapped in individual bundles of 20-30m section. All curtains are supplied with the necessary connection equipment to join any length of curtain once it arrives on site. Guidelines for connecting curtains are detailed below:

  1. Curtain bundles should be unpacked close to the ashore in a location that allows for the curtain to be towed off-shore using an appropriate boat. If being deployed further out to sea or from the tug, this procedure may be adapted to suit the deck of the vessel.
  2. Curtain bundles should be situated end-on-end so that each section can be connected together. In curtains with Velcro end connections, please ensure curtains are the correct way around, as ends will only join one way.
  3. Cut/untie the last furling strap at each end and stretch out the end of the curtain. For deeper drop curtains multiple furling straps may need to be cut. At this stage it is
    important to only cut the furling lines at the ends and not along the rest of the curtain as this should only be done once the curtain is securely anchored in position.
  4. Each silt curtain is delivered with approximately 18x1m floats pre-inserted into the float pocked (for 25m panels) to allow curtains to be folded and bundled for freight purposes. An additional 6-7 floats per panel are delivered separately. These floats need to be inserted into the floating pocket to create a solid float pocket with minimal gaps. Remove zip ties from the floating pocket, insert 6-7 floats, and close the floating pocket with new zip ties.
  5. The floating pocket also contains a rope tension line which needs to be connected between panels. Thread this line through the webbing loop and tie it together. It is important that this rope also be used when connecting anchors as it provides additional strength.
  6. Starting from the top and working down, align the eyelets and in the case of Velcro connections, press together firmly so the eyelets line up. In some cases, the Velcro will need to be bunched to allow for the eyelets to overlap. This is normal as there can be some small variations in the spacing of eyelets.
  7. Once all the eyelets are overlapped and the Velcro securely pressed together, loop a cable tie/zip tie through each pair of eyelets and pull tight. Cut off any excess. In curtains without Velcro or for a strong connection, cable ties may also be supplemented with 6-8m rope, which has a higher breaking strength and better UV resistance over time.
  8. The chain pocket should be connected using the shackles provided, making sure they are connected through the webbing loop.
  9. Once the connection of curtains is completed, re-furl the curtains by retying the cut furling straps.

2.2 Deployment

When deploying silt curtains please note the following advice:

  • For ease of installation, a silt curtain should be deployed in calm weather at the turn of the tide (slack water).
  • Curtain furling straps should all be securely tightened between every float section and on endpoints to reduce towing friction.
  • Where possible always tow with anchor connection and the chain ballast pocket.
  • Limit curtain towing lengths and tow distance as much as possible. Curtains’ length should not exceed 400m in one tow.
  • Tow curtain in a straight line at 1 knot. Avoid sudden acceleration or surging throttle. The silt curtain will be towed from the staging area to the water using a workboat.
  • Workmen will get into the boat with an access ladder. Later the curtain will be dragged using a boat hook.
  • No need for floating works platform.

2.3 Deployment Procedure

  1. Determine the appropriate location for deployment. If shore anchored, pre-arrange the necessary anchor point. This can be done using driven posts, concrete blocks, or anchors.
  2. Deploy by towing the seaward end of the curtain into position. Curtain furling straps should remain in place until anchored in the required position.
  3. If anchored to the shore, shore personnel should be ready to connect the final section to the shore anchor point.
  4. Once in the desired position, deploy the anchor system by the manufacturer or engineer.
  5. Ensure anchor ropes are attached to the top of the curtain under the floating pocket and joined to the anchor point.
  6. Anchors should be placed from the end section working backward towards land. It is important anchors are placed on both sides of the curtain to allow for tide and water movement.
  7. To place anchors, attach the anchor rope after the orange/red buoy to the designated anchor point on the curtain. Attach the anchor retrieval line at the yellow buoy to a suitable bow cleat on the boat. Reverse slowly letting the anchor line play out until the anchor itself is suspended midway between the curtain and the boat. Once the curtain is in position quickly release the rope at the cleat and allow it to fall. The curtain may drift once the anchor is released as it takes some time to dig into the seabed so readjustment may be necessary. This can be done either by readjusting the anchor with the same procedure or by shortening the rope at the curtain itself.
  8. Once the curtain is securely anchored, it may then be unfurled by cutting the furling straps for each section.
  9. The curtain should be monitored for up to 24 hours. Once lowered, the skirt will catch the water which may change the position of the curtain.
  10. Readjust anchoring if required.

3 Anchoring and Connection to the Shore

  1. It is normal for silt curtain installation to use a site plan with designated anchor points denoted. If anchoring using a customized system, GPS coordinates may be used to place anchors accurately. The layout of the curtain and types of anchors used will depend on local conditions, currents, and waves. Typically either Danforth anchors or concrete blocks are used. Danforth anchors are the preferred choice due to their lightweight and heavy holding power.
  2. A 25kg Danforth anchor is equivalent to 200-400kg holding power (depending on the seabed) and is less likely to drag like concrete blocks. In rough or tidal conditions, curtains may be attached to shock-absorbent buoys via a short painter line which reduces the force placed on anchors and prevents the anchor point of the curtain from becoming submerged.
  3. The load design, layout, and attachment of the anchor system are typically performed by the contractor on-site with the assistance or input from the end customer. Anchors should be placed on both sides of the curtain to allow for tide and water movement in both directions.
  4. As per the given quay wall drawings/photos, there are no rings or fixing points on the wall. To avoid leakage attach the curtain to the chain link fence or place a temporary crash barricade on the quay wall.

4 Maintenance

  1. All curtains are designed and built to withstand local conditions however regularly scheduled maintenance inspections are recommended to detect normal wear and tear or damage from marine craft. Load-carrying components such as connectors and anchors should be inspected regularly and float pockets should be visually checked for damage or wear.
  2. A silt curtain is a non-reactive material to any kind of chemical/salt water which can be cleaned easily and can be reused after the completion of the project. Periodic maintenance and inspection shall be carried out to confirm the effectiveness of the installed silt curtain.
  3. In areas where there is a large volume of silt or dredged material in close proximity, the depth of the curtain should be regularly checked to ensure the skirt does not become buried on the seabed, which could lead to the submersion of floats and barrier failure.
  4. Installations with a longer time frame (>12 months) and skirts made from PVC should be regularly cleaned of marine growth to ensure curtains maintain their integrity and reduce weight. Whilst curtain can be cleaned in-situ by divers it is often better to be re-furled and towed into shore for ease of cleaning via pressure spray or brushes. Care should be taken not to damage curtains on removal by catching on seabed or shore and not to lift using anchor points, ballast chain, or tension ropes as the weight of the curtain may exceed loading in these areas. Lifting in sections using a wide lifting belt underneath the furled curtain is often the safest way to prevent any damage. Curtains can also be separated in situ prior to removal to reduce the risk of damage. Any damaged sections can also be removed and replaced as required.
  5. Any damage to the skirt or float pocket may be repaired using recommended repair methods. PVC float and skirt fabric may be patched using patches of the same material either heat welded or using an adhesive PVC glue such as Bondloc MV Superglue. Damage to woven and non-woven geotextile skirt fabric can be patched using patches of the same material sewn over the tear or glued using 3M 4200 or 5200 marine grade adhesive.

5 Navigation / Lighting

  1. We recommend marker buoys, navigational aids, and lights to warn other watercraft of hazards and to prevent vessels from damaging or becoming entangled in the curtain.
  2. Reflective Buoys are used which can serve the purpose of guide during navigation.

Risk Assessment and Job Hazard Analysis

Permit and Licensing Requirements

Drawings, Diagrams, and Maps

Pre-Start Safety Briefing Arrangements

1. Risk Assessment – Refer to Risk Assessment Appendix.

2. Protective and Safety Equipment

All workers involved shall be equipped with adequate PPE as stated below:

  • Safety Helmet with Company Logo
  • Safety Boots
  • High Visibility Vest
  • Safety Goggles
  • Hand Gloves
  • Coveralls

3. Information to Personnel

Safety Induction
Job training
Superintendents Notices/Memos
Toolbox talks
STARRT Card

4. Special Safety Requirements

All necessary personal/protective equipment (PPE), as well as harness, be provided.

Banksman, wearing distinctive vests, shall be assigned to help operators maneuver their equipment.

The equipment operators shall possess the required licenses and certificates.

The required permit to work shall be obtained prior to the commencement of work.

The required TSTI will be prepared prior to the commencement of work and positively implemented.

The project safety officer is responsible along with the project zone site engineer for ensuring that all operations are carried out with due regard to the safety of all project personnel & property.

In case of working at night, please refer to Method Statement for Night Works.

Environment and Quality Issues

1. Precautionary Measures

All precautionary measures shall be briefed to all workers prior to commencing the activity.

2. Disposal Requirements

All waste shall be disposed of as per Environmental Compliance and Management Plan and as per Government approved disposal areas.

3. Inspection, Test, and Sampling

a. Request for Inspection shall be done prior to and after completion of works.

4. Quality Assurance Requirements Table

Refer to Project Quality Plan

Attachments

Reference Documentation

Project Specifications

List of Appendices

Appendix:
Silt Curtain Design Sheet
Calculation Report
Cross Section Profile
Sketch and Drawings
Survey Limit Coordinates
Bathymetric Survey Result
Silt Curtain No Layout
Danforth Curtain System
Risk Assessment and Job Hazard Analysis
Permit to Work
Inspection and Test Plan
Survey Equipment Calibration Certificate
Bathymetric Survey Result Previous Project Experience List
Previous Project Experience List
Silt Curtain – Inspection Checklist
Workboat Certificate
Organization Chart
Material Submittal Approval Sheet

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