## 5 EARTH WORKS, PIPE WORKS AND GROUND IMPROVEMENT 

## 5.1 Site Investigations 

## 5.1.1 General 

The geotechnical assessment report given with the tender documents provides an outline of the ge- otechnical status of the site based on measurements at the wastewater treatment plant site, and there is a need for additional investigations. 

The geotechnical assessment is subject to change according to the plant structures and layout in the Contractor detailed plant design. The survey is given only for information purpose. The Contractor shall conduct new soil investigations according to the locations, dimensions, foundation depths and weights of the structures in his detailed design. The Contractor is responsible to design and build the plant including soil improvement if necessary. The foundation, ground stability should be complied with Section 5.4 and 5.5. If the Contractor finds it necessary for the execution of the Contract to per- form more geotechnical or topographical surveys and site investigations, such costs shall be deemed to be included in the Tender. 

After the commencement of the Works, the Contractor shall update the surveys according to the gen- eral layout and hydraulic profile of the plant structures in the contractor's detailed design. 

The fieldwork to be carried out by the Contractor shall comprise: 

 vertical test borings 

 disturbed & undisturbed sampling and laboratory tests 

 penetration tests (S.P.T. and/or C.P.T.) 

 plate bearing tests 

 permeability tests 

 ground water table and ground water quality determination 

 geophysical investigations (where required by Code for Infrastructure Works in Disaster Are- as). 

The site investigation work shall be carried out using modern methods and equipment and by fully competent staff under the supervision of a qualified Contractor’s Representative. The equipment em- ployed shall be such as to provide the necessary data. 

In the wastewater treatment plant, the number of vertical test borings shall be a minimum of 10 and the borehole depths shall be 30 m or bedrock depth plus 5 m penetration into sound bedrock, whichev- er is smaller. 

## 5.1.2 Standards and rules 

The Contractor shall carry out the investigations, tests and reports according to the following codes, standards and specifications. 

 Ministry of Public Works and Settlement, Code for preparation of geological and geotechnical investigation reports, 2005 

 Ministry of Public Works and Settlement, Code for infrastructure works in disaster areas, Earthquake code for infrastructure 

