Construction Surveying Procedure

This Site Layout Staking phase typically begins with those features that are underground such as sanitary sewer lines, storm drain lines, water lines, electrical lines etc. Once all underground utilities are installed the above ground features are staked for construction. The building corners are staked along with any interior grid lines throughout the building, as well as onsite items such as fire hydrants, curb and gutter, walls/planters, catch basins and area drains.

Site Layout Survey is the process of interpreting construction plans and marking the location of proposed new structures such as roads or buildings. Construction staking is performed to ensure a project is built according to engineering design plans. The staked reference points guide the construction of proposed improvements on the property, and will help to ensure the construction project is completed on schedule, on budget and as intended.

Scope

This Procedure prescribes the requirements for Topographical Surveys, objective of surface investigation is aimed to obtain information of topographical condition at survey location. This Topographical Survey procedure covers the following works (unless specified otherwise):

(1) Installation of Benchmark.

(2) Topographical survey 

Applicable Code and Standards

The following Codes and Standards are identified for specific or additional requirements in relation to this Procedure,supplemented by the latest issue and addendum at time of the project’s execution unless noted otherwise. All work included in this Procedure shall conform to applicable provisions of these publications, except as modified by the requirements specified herein or the details of the drawings:

1. OSHA Occupational Safety and Health Administration : OSHA Construction Industry Standards
2. ASME Gas Distribution Infrastructure Expansion Piping System
3. UTM WGS 84 Ellipsoid

Methodology And Execution Plan

Installation of Benchmark

The purposed of Benchmark establishment is intended to be used as a permanent point over the field, that point in future particularly during the construction stage can be used as reference point within stake out stage.

The Benchmark shall be installed on the stable area, easily identified and reachable. Shape and size of benchmark are planned to have dimensions or 20 cm x 20 cm x 70 cm, buried approximately 55cm below the ground level and the rest of 15 cm shall be clearly appeared above the ground level.

Traverse Survey

1. The position of traverse stations shall be determined based on a full study using topographical maps and reconnaissance of the site.
2. Traverse stations shall be established at the places where observations of intersecting angle and measurement or distance can be easily carried out without interfering with traffic.
3. Provide the determined traverse station with wooden stakes or similar objects, which shall not entail displacement and settlement. The existing structures regarding which there are no possibilities of displacement and settlement may be used as traverse stations.
4. A traverse route shall be a closed traverse.

Azimuth and Coordinates

1. The azimuth of traverse shall be the clockwise angle measured from the solar north.
2. Existing coordinate system of the site shall be used.

Observation of Horizontal Angles

1. Horizontal angles shall be measured using. Theodolite total station TOPCON N235 with tripod and EDM (Electronic Distance Measurement).
2. The number of observation shall be two or more.
3. When observed angles do not fall within the maximum allowable value of 40 seconds, carry out re-surveying. When the observed value fall within the above limit, the arithmetic mean value thereof shall be taken as the determined value.

Measurement of Distance

1. Two-way measurement shall be made using with tape measure and electronic Distance Measurement recording distance shall be made in millimeter.
2. When the measured value fall within 1/10000, the arithmetic mean value thereof shall be taken as the determined value.

Calculation

1. After the completion of traversing, distances, direction angles, and coordinate shall be computed.
2. If the error of closure of the direction angle as well as the ratio or errors of closure of the coordinates fall within the limit shown below, the error of closure shall be distributed equally over the traverse stations.

• Error of closure 0 direction sec angle
• Ratio of error of closure of 1/3000 or less coordinates

N : Number of sides of a traverse route.

Elevation of Benchmarks

Elevation of benchmarks shall be decided by direct leveling survey. A leveling route for measuring benchmarks shall be selected in such a way that the route starts from existing benchmark, and return either to the original benchmark or another existing benchmark in the area.

Observation 

1. Two way observations by level using a pair of staff shall be carried out. Lengths of fore sights and back sights shall be kept very nearly equal. As a rule, the length shall be not exceeding 50 m.
2. Reading of observation values shall be made in millimeters.

Limits in Observation Value

1. Limits in observations value in leveling shall be as follows : Error of two way observation 20 mm or less for each 1 km, Error of closure mm or less, Where S is one way distance in kilometer.
2. When the error of closure falls within the specified limits, it shall be distributed equally over the survey points in proportion to the distance between survey points.
3. When the error of closure has exceeded the specified limits investigate the causes thereof and carry out re surveying.

Construction of Station and Benchmarks

(1) The stations and benchmarks shall be carefully constructed after approval by the COMPANY.

(2) The Stations and benchmarks shall be provided with adequate protective fences to preserve them during construction terms.

(3) The stations and benchmarks shall be clearly marked with item number, elevation and / or coordinate.

Control Point Survey

Control point survey shall be carried out to produce fixed coordinates of each control point referred to the reference point subjected by the COMPANY Engineer.

Survey Procedure

• All benchmark (both existing and new installed) in the survey area shall be measured and made connected to the reference point.
• Network map survey shall be made as loop or close route.
• Survey method for this control point survey shall be carried out by Geodetic GPS or Traversing and Leveling survey.
• Traversing survey shall be carried out by using Theodolite total station TOPCON N235 with tripod and EDM (Electronic Distance Measurement). Horizontal angle shall be observed by a double series of Theodolite reading. Whenever discrepancies exist between mean value and its series of reading of more than 5”, the next double series shall be carried out. Vertical angle shall be observed by face left and face right reading into consideration the error of collimating line. Slope distance shall be observed at least 3 times display. Horizontal distance shall be obtained from forward and backward slope distance and it’s respective to vertical angle. Section accuracy of network scheme shall be : Angle close error =  and linear Error =  1/10000 or better n = number of point observation.
• Leveling survey shall be carried out by using Automatic Level. Double stand leveling shall be introduced where fully optical means shall be read off during the first stand while for the second stand shall be 3 mm. all of data reading shall be recorded to the field note for further processing. Minimum of line or sight shall be 5 m while the farthest not exceed than 60 m. to maintain the accuracy, total backward and forward distance shall be balanced and also the staff shall be supported by foot-staff. 
• All field data shall be carefully recorded for further processing and description or each control point shall be taken for documentationan completed with clear sketches how to reach.

Topographical Survey

1. Topographical survey shall include horizontal control survey, vertical control survey and survey of the whole site using cross section in every 25 meters.
2. Topographical map shall show horizontal detail and elevation of the ground.

Horizontal Control Survey

1. Sufficient number of control benchmarks for detail shall be installed.
2. Location of the control benchmarks shall be decided by site reconnaissance
3. All coordinates of control benchmarks shall be decided according to the existing benchmark by means or traverse survey.
4. Accuracy of coordinate of existing benchmark shall be confirmed by traverse survey.

Vertical Control Survey 

1. Sufficient number of temporary benchmarks shall be installed for the whole site survey of areas.
2. All elevation of the temporary benchmarks shall be decided according to the existing benchmark by means of direct leveling survey.

The Whole Site Survey, Cross / Longitudinal Survey 

1. Horizontal and vertical detail of areas shall be surveyed based on the control benchmarks.
2. Cross section shall be surveyed by direct leveling at 25 m intervals.
3. Theodolite total station TOPCON N235 with tripod and EDM (Electronic Distance Measurement). shall be used to collect data of cross section.
4. Beginning Point (BP), Intersection Point (IP) and Ending Point (EP) shall be set out for each cross section line from the nearby control point.
5. Wooden peg or concrete marker shall be established for each marking BP, IP and EP.
6. Traversing and leveling work shall be carried out to preserve coordinates and elevation of BP, IP and EP referred to existing BM.
7. The measuring intervals of cross section shall be 25m and all notable changes of topography shall be measured.
8. All fields shall be carefully recorded for further processing.

The Process Plant 

The details for Process Plant shall take less then 50m. The results shall be processed and shown with 0.5 m contour intervals on maps 1 : 1000. The details of buildings, roads, tracks, vegetation, agricultural areas, fences lines and any water courses or wetlands shall be set out on the drawings provided. Such contour maps shall also contain:

1. Any reference points or monuments
2. True north and the grid system adopted
3. The nature of the terrain and features identified
4. Cross sections of areas of interest, as specified by COMPANY.

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