Site investigation Desk study phase and Site reconnaissance Q1

Ref:

Own account.

Another answer is provided by

Necessity of site investigation

Site investigation is done for obtaining the information about the surface and subsurface conditions at the site of proposed construction.

The information is essential for the design of structure and for planning of construction technique.

Site investigation are generally done to obtain the information useful for the following purposes:

1. To select the type and depth of foundation for the given structure.
2. To determine the bearing capacity of the soil.
3. To estimate the probable maximum and differential settlement.
4. To establish the ground water level and to determine the property of water.
5. To predict the lateral earth pressure against retaining walls and abutments.
6. To select suitable construction technique.
7. To predict and to solve potential foundation problem.
8. To ascertain the suitability of soil as construction material.
9. To investigate the safety of existing structure and to suggest remedial measures.

Ref:

Pirpasha Ujede, Engineer-Projects at Rheaa Civitech Pvt Ltd, in Slideshare, available at,

https://www.slideshare.net/PIRPASHA/siteinvestigation-before-construction-of-structure

b) Desk study & site reconnaissance

This question is worth 20 marks. Indeed, there are details needed. However, the question only asked two phases within 'site investigation'. Thus, we need to understand what are the different phases of site investigation. It did not ask all the phases, it only asked these two phases.

The different phases of Site Preparation are listed below:

1. Desk Study
2. Site Reconnaissance
3. Detail site exploration and sampling
4. Field test/in-situ test
5. Laboratory testing
6. Report

Desk Study - maps and other relevant records - drawings, details of existing or historic development, local authority records, geological maps, memoirs, details of utilities, services, restrictions, right of way, ownership of adjacent properties, aerial photography.

Site Reconnaissance - early study by experts like geologist, land surveyor, soil engineer, hydrologist, Information should be collected on overall site layout, topography, basic geology, detail of access, entry and height restriction.

Benefits of a Desk Study

• Mitigate/minimise risk
• Understanding of potential variations in ground conditions
• Can lead to economical design of foundations / geotechnical structures
• Reduce likelihood of unforeseen ground conditions
• Reduce chances of delays on site
• Quantify / qualify risk
• Accurate forecast of budgets

Ref:
http://www.soilconsultants.co.uk/desk-study/

The following extract from EURSSEM is about Site Reconnaissance:

The objective of the site reconnaissance or site visit is to gather sufficient information to support a decision regarding further action. Reconnaissance activity is not a risk assessment, or a scoping survey, or a study of the full extent of contamination at a facility or site. The reconnaissance offers an opportunity to record information concerning hazardous site conditions as they apply to conducting future survey work. In this regard, information describing physical hazards, structural integrity of buildings, or other conditions, defines potential problems that may impede future work. This section is most applicable to sites with less available information and may not be necessary at other sites having greater amounts of data, such as licensed facilities.

To prepare for the site reconnaissance, begin by reviewing what is known about the facility or site and identify data gaps. Given the site-specific conditions, consider whether or not a site reconnaissance is necessary and practical. This type of effort may be deemed necessary if a site is abandoned, not easily observed from areas of public access, or discloses little information during file searches. These same circumstances may also make a site reconnaissance risky for health and safety reasons – in view of the many unknowns – and may make entry difficult. This investigative step may be practical, but less critical, for active facilities whose operators grant access and provide requested information. Remember to arrange for proper site access and prepare an appropriate health and safety plan, if required, before initiating the site reconnaissance.

Investigators should acquire signed consent forms from the site or equipment owner to gain access to the property to conduct the reconnaissance. Investigators are to determine if Governmental or local officials, and local individuals, should be notified of the reconnaissance schedule (stakeholder involvement). If needed, local officials should arrange for public notification.

It is advised to prepare a study plan before the site reconnaissance to anticipate every reconnaissance activity and identify specific information to be gathered. This plan should incorporate a survey of the site’s surroundings and provide details for activities that verify or identify the location of: nearby residents, worker populations, drinking water or irrigation wells, foods, and other site environs information.

Preparing for the site reconnaissance includes initially gathering necessary materials and equipment. This may include a camera to document site conditions, health and safety monitoring instruments including a radiation detection meter for use during the site visit, and extra copies of topographic maps to mark target locations, water distribution areas, and other important site features. A logbook is critical to keeping a record of field activities and observations as they occur. For documentation purposes EURSSEM recommends that the logbook should be completed in waterproof ink, preferably by one individual. Furthermore, each page of the logbook should be signed and dated, including the time of day, after the last entry on the page. Corrections should be documented and approved.