Concern Worldwide

Geotechnical Investigation Bentiu, Unity State, South Sudan

Concern Worldwide

Job Description

1. Background

In Rubkona County, Concern jointly with UNICEF and State Ministry of Lands, Housing and Public Utilities[1] operates a water supply network serving the community of Rubkona and Bentiu towns through communal water points, water kiosks, individual tap stands and commercial business connections. Private people are using donkey carts as well as water tankers to access water from the Bentiu water treatment plant and the Rubkona emergency SWAT system. The two towns have in the recent past seen an influx in the number of families settling in these locations due to the signed peace agreement in South Sudan. This has exacted pressure to the existing system.

Concern has secured funding from OFDA and DFTAD for installation of additional storage tanks and improve the network system through construction of water kiosks, water line extension and metering of existing individual and institution connections.

The scope of work comprises of conducting detailed study of ground investigation, laboratory testing, conducting and estimation of safe bearing capacity for a proposed work on installation of two elevated 50m3 tanks. The location is Bentiu, Rubkona County, and Unity State in South Sudan.

B. Objectives

  1. To characterize the soil in the tank foundation area based on their physical properties
  2. To find out the bearing capacity of the soil
  3. To find out more evidence on the strength of the soil around the tank construction area based in the human activities presently and in the past.
Nature of Investigation Work

The nature of all investigation consists of the following: provide all necessary equipment, tools and conduct the following;-
  • Visual reconnaissance of the site.
  • Field Work-Drilling of one test boreholes up to the required depth of 15m-
  • One trial pit close to the existing water tower pad foundation to determine the depth and dimensions of the base of the existing pad foundation
  • Laboratory experiments, determination of soil parameters.
  • Analysis of field and Laboratory data
  • Arriving at the conclusive decision on foundation system to be adopted in the present case using appropriate engineering standards i.e BS (British Standards), South Sudan National standards, based on the current practice.
The detailed geo-technical investigation work that needs to be carried out consists of two parts.

  1. Field Investigation:
The field investigation consists of the following parameters and methods
  • Drilling one 15m deep borehole at the location of the newly proposed water towers. Work shall include:
  • Standard penetration test (SPT) every 1.0m depth
  • Bulk samples (10-20kg) taken every 1.0m depth
  • Pictures of the soil samples taken every 1.0m depth
  • Recording of any groundwater strikes
  • Conducting a Unified soil classification system (USCS) tests for every sample including all accompanying tests to determine soil type USCS shall be performed every 1 meter. Soil type profile throughout depth at an interval of 1m, including cohesiveness, density, particulate matter. The field boring log shall be included in the geotechnical report submittal. The depth of water table shall also be recorded if found and reported on the log.
  • Conducting tests including:
  • Consistency test
  • Settlement test
  • Plasticity Index (cohesive soils) or grading (non-cohesive soils) if possible
  • Moisture content shall be determined and reported for every sample.
  • Estimation of strength at various proposed foundation levels;
  • Recording of any other contaminants seen during the investigations.
  • Study of local site conditions and surroundings
  • Verifying the state of any structure that has performed satisfactorily or failed on the local soils
  • Consultation of geological maps (if available) and any other uses of the site.
  • Taking observation of surrounding structure to observe any deficiency in safety
  • Consider the impact on the environment and any risks to life or adjacent property
  • Transportation of all soil samples to laboratory, where possible, for analysis with proper care.
  • Undertake a trial pit next to the existing water tower to inspect the depth, dimensions and founding material of the existing foundation:
  • Base of trial pit should be deep enough such that the depth of base of the existing pad foundation can be determined, it should not be excavated any deeper than required.
  • Trial pit to include 0.5m steps every 0.5m depth. The trial pit should be made stable with shoring where appropriate. On no account should anyone enter the trial pit unless it has been properly shored.
  • Pictures to be taken frequently, including the condition of the foundation with an appropriate scale.
  • Length and width of the foundation should also be determined, via additional trial pits if required.
  • Descriptions of encountered soil including soil consistency/ density (soft, firm/ loose, dense etc.), colour, structure and discontinuities, principle soil type and secondary constituents.
  • Laboratory Tests:
The Consultant should conduct a soil test on the collected samples. The Laboratory tests required for the sample collected are given below
  • Determination of Grain size analysis
  • Determination of soil moisture content
  • Determination of liquid limit
  • Determination of plastic limit
  • Determination of specific gravity
  • Determination of Allowable Bearing Pressure of the soil using the BS 8004.
  • Particle Size Distribution (PSD) with sedimentation via pipette
  • Atterberg limits and moisture content
  • Ground/groundwater aggressivity, including: pH, total sulphate (SO4), water soluble sulphate and total sulphur
Deliverables

Geotechnical Report
  • Develop a summary paragraph of the scope of work as highlighted.
  • Give a summary of site location and description of the project site, indicating principal topographic features in the vicinity including site photos showing subsurface investigation methods at the project site.
  • Provide clear and precise tables that summarizes the geotechnical findings for easy reference by designers and reviewers including and not limited to:
  • Number of soil samples and location relative to foundations.
  • Soil classification for all collected samples including data from all tests mentioned above
  • Summary of design parameters, settlement analysis with calculations and references provided.
  • A comprehensive summary of allowable bearing capacity analysis with calculations and references provided. Calculations shall consist of the equation utilized, definition of all variables, values used for all variables, and the calculation (substitution of values for the variables). Every step of the analysis shall be included for verification. If assumptions are made, then those assumptions shall be clearly stated and supported with verifiable information contained within the report. Note: soils laboratories shall report the allowable bearing capacity values.
  • The Factor of Safety (FS) utilized for analysis shall be clearly stated within the report. It shall be obvious that the Factor of Safety was implemented in the calculations reported.
  • The report shall be presented in English, and shall be no longer than 30 pages, excluding annexes, drawings and appendices. It shall be in word format; font 12, calibri, double spacing, submitted electronically.
Personnel

The consultant’s staff should have extensive experience in geotechnical survey (preferably geotechnical surveys/investigations for vertical structures and associated infrastructure).

Team Leader;
  • Minimum BSc. Engineering in Geology or any other relevant field,
  • 2-year experience as a geotechnical survey/investigation team leader
  • 5 years of experience in buildings geotechnical studies
Geotechnical Engineer
  • Minimum BSc Civil Engineering or any other relevant field
  • 3 years’ experience in materials Engineering, and
  • 5 years in general construction
Safety:

  • Backfilling boreholes and excavations: All open boreholes, test pits or trenches, and accessible borings, must be covered or provided with suitable barricades, such as fences, covers, or warning lights, to protect pedestrians and livestock. Following the work, they must be fully filled in and compacted at regular intervals.
  • The Consultant shall ensure that all of his staff and workers are equipped with Personal Protection Equipment (PPEs). No worker or engineer will be allowed at site without having proper PPE.
  • All other safety aspects of working at height or working in excavations must be taken into account by the Consultant.
Quality Assurance

Concern will perform a quality assurance review of the contractor’s work to confirm that proper criteria, regulations, laws, codes, principles and professional procedures have been used. Concern will also review the work of contractor during each phase of geotechnical survey and return comments in writing.

1. Operational support:

· Concern will be responsible to arrange the logistics movement in Bentiu/Rubkona as required.

· Concern will provide basic accommodation in the Humanitarian Hub to the consultant when in Bentiu.

· All the travel from Consultants host country to Juba and back including the local travel will be paid by Concern.

· Consultant should be following the Covid-19 restrictions at all times laid by the Ministry of Health, South Sudan.

6. Lines of Communication

The consultant will report to WASH Programme Manager of Concern Worldwide South Sudan, but will work closely with the WASH Engineer, Bentiu Coordinator" id="link" class="link">Area Coordinator and the Base Manager.

General Conditions of the consultancy
  • The consultant must complete all formal administrative requirements of Concern like signing Concern’s Programme Participant Protection Policy.
  • Concern will provide transport to facilitate the work activities.
  • The Consultant should have their own laptop to complete the work activities.
  • In country flight/travel from Juba to project site shall be paid by Concern Worldwide
  • Accommodation will be provided by Concern Worldwide in Juba/field in compliance with Concern’s policy while the consultant will cover fully his/her food subsistence related costs.
  • The movement of the consultant and team to and from the field will be facilitated by Concern Worldwide.
  • Concern WASH team at Bentiu level, Programme Director and Concern WASH Advisor will review the report with comments before payment is made.
  • Payment will be subject to 10% withholding tax, as per South Sudan law unless the Consultant provides confirmation that s/he is exempted.
Security The Country Director as the person responsible for security will make the final decision on travel plans of the Consultant based on security assessments. The Consultant must accept the Country Director’s decision and must adhere to all Concern South Sudan security protocols while in-country.

7. Timeframe

Due to the nature of the proposed work, it is expected to take 15 days; travel days, field investigation, sample collection, laboratory analysis, report writing and final report submission to Concern.

[1] Formerly State Ministry of Water and Physical Infrastructure Qualified and interested individual/firm consultants can submit their sample of similar work done preferably within Africa, Technical and Financial proposals, including CVs of key personnel to southsudan.deskofficer@concern.net by 5 February 2021.

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