Method Statement for Dewatering System

Method Statement for Dewatering System

1. Introduction

This Method Statement for Dewatering System defines the sequence and the control procedures to be followed for the dewatering of the project.

What is dewatering?

Dewatering is described as the control of surface and subsurface hydrologic environments so as to permit the construction of the structure in suitable and safe working conditions.
In the construction project, this is also described as the removal of groundwater below the normal water table to attain a safe workplace during site activities.

2. Definitions

CM: Construction Manager
QC: Quality Control
HSE: Health Safety & Environment
PPE: Personal Protective Equipment
PMV: Plants, Machinery & Vehicles
PSC: Power Station Control

3. 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).
Project Specifications-Dewatering of Excavation
Dewatering Design: xxxxxxx
General Lifting Plan: xxxxxx
Project Specifications-Health and Safety
Spill Prevention and Response Plan: xxxxxx
Procedure for Delivery, Dispensing, and Storage of Fuel on Site: xxxxx

4. Responsibilities

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.

Construction Manager

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

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 non-conformance 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.

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.

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 MS 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 for Health & Safety requirements and monitor the Hazard controls implemented on site as per the Method Statement/Risk assessment.

Environmental Manager

Responsible for entire environmental matters and preparing Environmental Risk Assessments (ERA) in line with method statements for a particular activity.
Liaise with Engineer and Engineer’s Assistant for environmental issues. Monitoring the environmental requirements as per Project Specifications and Engineer/Engineer’s Assistant requirements.

Environmental Engineer

Monitoring works implementation as per the project’s environmental requirements. Advice for environmentally sound operations and provide adequate instructions, training, and supervision to enable employees to work avoiding environmental impacts.
The report determines & analyzes the cause of any environmental incidence and recommends measures for preventing recurrence.

Dewatering Engineer

Coordinates activities with all engineering personnel, Project Managers, and outside consultants and/or contractors.
Develops engineering/dewatering site action plans to guide the timely and cost-effective development of projects. Maintains the system of budget and schedule control.
Does Engineering services for preparation and drafting of drawings, schematics, product specifications, bill of materials, operation service manuals, assembly manuals, and other documentation.

 Chief Surveyor

Carry out a pre-construction survey 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 serial number of calibration certificates are available and posted on the survey equipment.
Ensure proper safety guarding of surveying equipment.
To maintain the records of all surveying equipment handled.

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.

Site Foreman

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

Workforce

Carry out their work under direct supervision by their Foreman and Charge Hand and under instruction from the Site Engineer to ensure all works are undertaken in a safe manner.
The workforce is to attend daily Tool Box Talks and morning task briefs prior to starting any new work.
The workforce shall receive a full Project briefing and site rules induction prior to commencing any work on site.

5. Interfacing with Other Operations

Location & Level of Intersecting Roads
Location & Level of Temporary Fence
Excavation
Shoring Works

6. Duration, Phasing with the Subcontractors

Duration for the Dewatering System is indeterminate since the work will be stopped and or removed only upon completion of the necessary works and upon approval of the Consultant.

7. List of Subcontractors

Main Contractor:
xxxxx

Subcontractor for Dewatering:
xxxxx

II. Resources

1. Plant and Equipment

Note:
3rd Party Certification for Plant and Equipment will be available and checked to ensure validity prior to commencing work.
All machines shall fulfill the client’s requirements if required.
Refer to the attached Survey Equipment Calibration Certificate in Appendix F.

2. WorkForce

3. Light Tools

III. Materials

Dewatering Pumps 6” Nominal Diameter (S6S-60/11, 22KW, 30 HP)
500mm/250mm HDPE SDR17 Discharge Pipes
V-notch Weir Tank
HDPE Fusion Welding Materials
Gravel Backfill for Trench
Warning Tapes
Emergency Kits

IV. Site Planning

Duration for the Dewatering System is indeterminate since the work will be stopped and or removed only upon completion of the necessary works and upon approval of the Consultant.

a. 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.

b. Site clearance

• Before commencing the work, the area shall be cleared of all debris, materials, or other obstructions.

c. Traffic Management

• The Site Team with the assistance of the Safety Officers shall coordinate logistics and materials move through the site following the direction and road signs displayed on site. The required diversion routes shall be marked on drawings including the required traffic signs.
• The Work Permits and Operator Certificates shall be compiled and filed for reference by authorized personnel.
• Temporary traffic signs, barriers, and flagmen will be deployed to control traffic flow in accordance with Roadwork Construction, and Traffic Management of the HSE Plan.

d. Pre-construction Safety Meetings:

The 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 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.
• Contractor safety staff 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, authorized 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

e. 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 signboards will be displayed and barricades will be installed where and as necessary, such as but not limited to the following:

• Advanced signs e.g. “Work Area” signs will be placed ahead approximately 300 m before the activity zones on both sides of the road.
• Relevant information, warning, and mandatory signs such as Narrow Road Signs, One-Lane Traffic signs, etc. will be placed approximately 25 m from the last advanced signs.
• Buffer zones and working areas will be cordoned with highly reflective traffic cones/barriers to separate the survey team and workers from the main traffic flow.
• “One Way Traffic Ahead” signboards would be placed 90 m ahead of the working area in order to notify incoming drivers of the new road layout.
• Traffic Controllers would be deployed on both sides in order to control “One-way traffic”.
• Photographs would be taken for information to maintain traffic safety record-keeping.
• Radio Communication systems would be used where normal communication is impossible.
• After completion of the work, safety cones and barricades have to e removed accordingly.

V. Methodology

This how will the method statement for dewatering will be implemented during the construction stage of the project.

1. Procedure for dewatering

In order to control groundwater levels a hybrid system consisting of an array of 201 nos. deep wells interconnected with a perimeter trench will be used. The deep wells will be installed around the internal perimeter of the slope. The deep wells will then be connected by a perimeter trench and cross-trenching as required.

Electric sump pumps (Pump Model: SGS-60/07) will be installed in each well. The pumps will be powered from a Power Station Control (PSC) with power cables commonly following the line of the discharge pipework.

The pumps will feed to a header main which shall discharge at the sea via a discharge tank. The discharge tank should allow for visual inspection of the flows and water quality testing.
The monitoring of drawdown levels will be carried out using Standpipe Piezometers.

2. Permits

Permit to be obtained from the client to discharge in the adjacent lagoon.

3. Drilling and Installation of Deep Wells and Monitoring Wells

Prior to the drilling of deep wells and the monitoring wells, the locations of the proposed wells shall be set-out. Existing services in the areas shall be checked and verified that no conflicts occur with the drilling works.

Once the borehole is drilled, a Perforated PVC casing shall be installed using a Crane. A bottom plug shall be installed on the first 6m length of casing and further 6m lengths shall be added until the casing has reached the base of the borehole. The casing diameter for the deep wells will be 330 mm with machine-slotted screens.

The monitoring wells will have a casing diameter of 50 mm with machine-slotted screens. A 5-10 mm crushed gravel shall be installed in the annulus with the depth checked periodically to ensure bridging is not occurring during the installation.

Appendix A shows the drilling and installation steps and provides well details.

4. Development of Deep Wells

Following well drilling and installation of the good liner and gravel pack, well development will be performed.

An airline is placed down the well, approximately 1–2 m from the base, and will be connected to a compressor. The well will then be pumped by airlift for a minimum period of 1 hour or until the discharge water is free of drilling mud and/or fines.

The airline will then be lifted in 2.0 m intervals and pumped on for at least 15 minutes at each level to the top of the screened section of the well or for a minimum period of 2 hours.

5. Installation of Pumps

An Electric Submersible Pump (Pump Model: SGS-60/07) will be installed in each of the deep wells with the pump inlet located near the base of the well. The pump will be fixed by 2 nos. safety support ropes. The electric drop cable from the Submersible Pump will be connected at ground level to an isolator switch. The pumps will be lowered into the wells using the safety support rope and Crane.

An armored rubber flexible hose or UPVC riser pipe shall then connect the headworks to the discharge pipework. A check valve and automatic non-return valve will be fitted at ground level.

If the pumps need to be removed for maintenance or other reasons the pumps will be removed either using a Crane or other suitable lifting equipment.

6. Installation of Header Pipework and Discharge Pipework

The discharge pipework shall be installed around the excavation perimeter with takeoffs at each well location. A check valve and automatic non-return valve will be fitted at each pump head works.

Once installed the header pipework shall be suitably protected to ensure no damage can occur from site traffic or personnel.

Wherever the discharge pipework crosses haul roads/site access the pipework should have additional protection measures in place suitable to each site-specific condition. The discharge pipework shall be connected to a discharge tank. The discharge tank would allow for visual inspection of the flows, water quality testing, and flow rate monitoring via a V-Notch Weir.

7. Power Station Controls (PSC)

The electrical controls and protection for the pumping system shall be located in the Power Station Controls (PSC). The PSCs house the generator switchgear and alarm system.
All cables shall be steel-wire armored to provide protection against accidental damage. A changeover switch in each PSC connected to the duty generator and standby generator shall allow the standby to cut in automatically in the event of a power failure.

8. Monitoring of Discharge Water

Discharged groundwater will be monitored and tested in order to check the quality during the dewatering works. Monitoring of discharge water shall be carried out by Third Party Laboratory and to be submitted periodically to the Client, PM/CM, and Consultant.

It is the aim that the discharge water from the dewatering works complies with the requirements of the Ministry of Environment for the disposal of groundwater into the sea. Part of this test would be to take Groundwater samples to analyze the in-situ water quality.
Monthly test parameters are outlined below as per authority/government requirements (subject to change upon permit approval).

Item Description

1 TDL (mg/l)
2 Turbidity (NTU)
3 Dissolved Oxygen (mg/l)
4 Sulphide (mg/l)
5 Oil and grease (mg/l)
6 TSS (mg/l)
7 pH (mg/l)
8 Odour
9 Alkalinity (mg CACO3/L)
10 Metals (Cr, Pb, Ni, Zn, Cd, As, Se, Cu) mg/l and (Hg) ug/l
11 BOD5 (mg/l)
12 COD (mg/l)
13 TPH (Gasoline range hydrocarbons, Diesel range hydrocarbons, Heavy fractions) (mg/kg)
14 Total coliform bacteria (MPN/100ml)
15 Escherichia Coli (MPN/100ml)
16 Metals (Cr, Pb, Ni, Zn, Cd, As, Se, Cu) mg/l and (Hg) ug/l

The analysis sheet from the Lab should be stamped and signed. MOE has the right to add or delete parameters from the list.

The Test Result should show:

Item Description

1. Material tested
2. Date of sampling
3. Delivery date of sample to the lab
4. Reporting date
5. Lab where analysis was achieved
6. QA/QC procedures of the lab

VI. Risk Assessment of Method Statement for Dewatering

Please refer to the attached document in Appendix B.

VII. Permit and Licensing Requirements

Please refer to the attached “Permit to Work” in Appendix E.

VIII. Drawings, Diagrams, and Maps

Please refer to the attached document in Appendix A.

IX. Pre-Start Safety Briefing Arrangements

1. Risk Assessment

Refer to Risk Assessment Appendix B.

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.
Generated dust shall be controlled by periodic water spraying.
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.
No working at height issues anticipated.
In case of working at night, please refer to Method Statement for Night Works.

5. For all activities but general precautions are outlined below;

PPE – employees are advised to wear a face mask during the dewatering work;

Plant operators must be competent & hold a current license for the plant being operated;

Signage –appropriate signage at the place of work – notifying the general public, i.e. Men at Work;

Safe Access / Egress shall be provided – allowing Site personnel and + General public to walk safely without causing injuries; Electrical Hazard – All electrical works shall be handled by qualified persons only;

Environment – For any activity that has the potential to cause an environmental issue, control measures would be put in place i.e. drip trays, spill kits, soak-up media;

Hot work – All hot works would be conducted under hot works permit and all control measures such as correct PPE, fire watcher, and fire extinguisher would be available prior to commencement;

Lifting operation – Lifting equipment and gear like cranes, slings, and shackles shall comply with construction standards.

5.1 Lock out tag out procedure

Lockout/Tag out for PSC shutdown and isolation.
1. Shut off points of operation switches and tag for isolation when:
a. Working on generators;
b. Working on electrical controls.
2. Shut off and lock and tag main power controls:
a. Shut off generators and tag ignition systems;
b. Tag PSC’s as to work being done;
c. Tag outside doors as to work being performed.
3. Lockout secondary power sources:
a. Dissipate any residual energy or pressure;
b. Bleed off pressure on cylinders and use jacks or blocks to hold;
c. Lock out or secure areas where employees may not be seen;
d. Lockout/Tag out.

Anyone placing a lockout device must:
1. Give prior notification when and where the lockout is being placed and who is placing it to their supervisor.
2. Tag locks with the following information:
e. Who placed the lock?
f. When the lock was placed?
g. What system the lockout is protecting?
3. Check that the entire system you are attempting to isolate is locked out.

5.2 Lock-out removal

1. When a lockout tag out is no longer required. The person, who placed it, is the only person permitted to remove it, and only after announcing that the equipment is back in service.
a. The work area has been secured;
b. Guards and safety shields have been placed;
c. The area has been visually checked to see if personnel are clear;
d. Know the equipment is ready for service.

6. Emergency Procedures

Please refer to Emergency Flow Chart in Appendix

X. Supervision and Monitoring Arrangements

Construction Manager

Overall in charge of Construction activities. Schedule the project in logical steps and budget the time required to meet deadlines. Inspect and review projects to monitor compliance with building and safety codes, and other regulations.

Site Engineer

The Site Engineer shall evaluate the number of materials consumed by each trade to be compared against the planned quantity.

Site Foreman

A construction foreman is responsible for supervising the workers and also doing actual construction work. The foreman monitors employees to ensure that the work is done efficiently and within quality standards.

QA/QC Engineer

The QA/QC Engineer shall monitor whether the installation works are conforming to the required quality otherwise he shall notify the Site Engineer should he find non-conformance to the ongoing activities. The Site Engineer shall immediately rectify the work to avoid receipt of NCR from the QA/QC Engineer.

HSE Engineer

The Safety Engineer shall be full-time at the site and shall frequently visit all the ongoing works at the site. All safety violations and on-conformance of the HSE Plan shall be registered and immediate action shall be done in coordination with the Site Engineer.

Chief Surveyor

A Chief Surveyor ensures that surveying data are collected and recorded accurately and that all company procedures are followed by crew members.

Environmental Manager

Responsible for entire environmental matters and preparing Environmental Risk Assessments (ERA) in line with method statements for particular activities.
Liaise with Engineer and Engineer’s Assistant for environmental issues. Monitoring the environmental requirements as per Project Specifications and Engineer/Engineer’s Assistant requirements.

Environmental Engineer

Monitoring works implementation as per the project’s environmental requirements.
Advice for environmentally sound operations and provide adequate instructions, training, and supervision to enable employees to work avoiding environmental impacts. The report determines & analyzes the cause of any environmental incidence and recommends measures for preventing recurrence.

Dewatering Engineer

Coordinates activities with all engineering personnel, Project Managers, and outside consultants and/or contractors. Develops engineering/dewatering site action plans to guide the timely and cost-effective development of projects. Maintains the system of budget and schedule control.
Does engineering services for preparation and drafting of drawings, schematics, product specifications, bill of materials, operation service manuals, assembly manuals, and other documentation.

XI. Environment and Quality Issues

Hazards/Precautions:

1. Environmental Criteria

The project management and environmental team shall plan their work prior to commencing any work in environmentally sensitive areas;
1. Plant and equipment shall be maintained regularly preventing spillage on site;
2. Risk of spillage of fuel/oils etc. would be prevented;
3. All spillages would be cleaned up immediately and reported to supervisors.
2. Environmental Spills
Spills / Leaks into the ground;
Spills into nearby drainage systems;
Over spilling when re-fuelling plant;
Lack of supervision;
Improper storage & fire;
Person’s fuelling up plant equipment shall not overfill;
Store / Fill equipment far away from water courses;
Keep drip tray under re-fuelling tank;
Persons in charge of plant equipment shall monitor these activities – ensuring no such incidents occur, and if any spills – reporting/cleaning up shall be carried out immediately.

3. Emergency Response Procedures to an Environmental Incident

The following steps shall be followed in the event of an environmental incident.

Step 1 – Contamination

Identify specific environmental/safety hazards such as contaminants in dewatering water (oil any chemicals) if found;
Close off areas to prevent traffic or public access;
Locate and use personal protective equipment (PPE) such as gloves, glasses, helmet, and safety footwear;
In the case of dewatering water contaminants (fuel or any chemicals) pose a significant risk to the community;
Take other actions as necessary to create safe conditions (for example, stop all smoking and remove ignition sources) if dewatering water contaminants are flammable; and Consult Environmental Manager / Engineer for further advice.

Step 2 – Stop the Source

Where simple, ongoing incidents are continuing to cause environmental impacts, identify the cause, and if it is safe to do so, stop or limit the incident from occurring (for larger, dangerous, or complex incidents go straight to Step 3),

Step 3 – Notify Relevant Parties

It is mandatory to notify the following parties immediately (after or as part of making the incident site safe):
Notification site management, as per any EMP requirements;

Step 4 – Control the Incident

Take immediate action (determine personnel, materials, and equipment necessary) to prevent or limit environmental harm that has occurred or that may occur as a result of the incident.

Where warranted due to the severity or nature of the incident, work would be halted at incident scenes in order to begin the incident investigation in an un-tampered environment;
Deploy fuel spill clean-up materials (from spill kits), such as absorbent particulate matter or absorbent mats if any oil/chemical contaminants from dewatering water are found.

Get extra waste skips delivered, for the temporary storage of contaminated soil or other waste associated with the clean-up.

Step 5 – Reporting the Incident

When the incident is under control, and initial clean-up or prevention measures have been implemented, the main contractor would complete the following:

• Monitor any controls that have been put in place for the incident, for example, absorbent materials used in fuel spill clean-up would require changing when fully saturated;
• Carry out an incident investigation and document it. The basic cause of the incident would be identified, and the corresponding preventative actions determined;
• All incidents would be thoroughly investigated to determine all root and supporting cause(s). All witnesses to the incident would provide statements and all data, monitoring records, medical reports, etc. pertinent to the incident or the suspected cause(s) would be taken into account and included in the investigation report;

XII. Attachments of Method Statement for Dewatering

1. Reference Documentation

Project Specifications

2. Appendices

Appendix A: Sketch and Drawings

1. Dewatering Layout

2. Discharge Pipeline

3. Cross Sections

4. Well Casing Installation

5. Well Development

6. Piezometer Layout

7. Monitoring Sheet for Piezometers

8. Table and Monitoring Sheets

Appendix B: Risk Assessment and Emergency Response Procedure

Appendix C: Material and Equipment Data Sheet

Appendix D: Inspection and Test Plan

Appendix E: Permit to Work

Appendix F: Survey Equipment Calibration Certificate

Appendix G: Emergency Flow Chart

tag: method statement for dewatering, groundwater, dewatering method statement