SCOPE OF WORK
The
scope of work under this section includes furnishing labor, technicians,
qualified professional surveyors, surveying equipment and materials required to
perform all surveying work, setting out and calculations necessary to establish
the accurate location of all plant facilities.SERVICES PROVIDED BY THE OWNER (NA)
A
basic survey based on fixed triangulation, polygon points and bench marks has
been performed by the Owner. The Contractor may use it for his surveying and
setting out as reference only.
The
Contractor will obtain plans containing the basic survey with all necessary
information. Should the Contractor has any objection to this basic survey and
the relevant drawings, he shall inform the Owner in writing within one week of
this handling over by the Owner.
SERVICES TO BE PROVIDED BY THE CONTRACTOR
GENERAL
The
Contractor shall, as described in this section, perform all surveying and
setting out and calculations necessary to establish the accurate location of
all plant facilities and shall carry out a continuous survey during
construction.
The
Contractor shall set out, construct and establish bench marks in stable areas
at the Site for his work. The survey for his bench mark grid shall only be
based on approved triangulation points of the national grid. The Contractor
shall submit calculations and drawings for the triangulation work done to
establish the benchmarks.
The
Contractor shall submit in sufficient advance, for approval by the Owner, the
methods he intends to apply for the surveying work.
PROTECTION
OF BENCH MARKS
The
Contractor shall protect, preserve and keep accessible the benchmarks of the
basic survey and any provided by himself. Any damage or removal of benchmarks
shall be avoided as far as possible. Any accidental damage to any benchmark
shall immediately be brought to the attention of the Owner. It is expressly
understood that the Contractor shall held responsible for damage to the
benchmarks and the resulting consequences. He shall thus take preventive
measures subject to approval in order to minimize the possibility of destroying
benchmarks. Benchmarks must be of stainless steel or cast iron.
The
steel bolt shall be embedded in an absolutely stable concrete block of suitable
size subject to approval of the Owner. Inscriptions shall be durable and
clearly legible. Intermediate points of the Contractor's triangulation survey
used in establishing bench marks may be marked by steel pipes or other pegs,
subject to the Owner's approval. Every new bench mark shall be double checked, as far as possible in relation to
points other than those which served to establish the point in question.
PERSONNEL
AND EQUIPMENT
The
Contractor shall entrust the surveying only to such persons whom by their
training and experience have sufficient qualification and knowledge to ensure
proper fulfillment of the survey tasks assigned to them. If requested, they
shall give the Owner any information relating to the survey. For the
performance of the survey, the Contractor shall have a sufficient number of
reliable, accurate and well adjusted instruments, the type and quality of which
shall be subject to the approval of the Owner.
AUXILIARY
WORK
The
auxiliary work of this section shall include, but not be necessarily limited to
the following:
Performing
all necessary survey calculations with clear presentation of calculations and
results in order to facilitate verifications
Exposing
covered Fix Points
Removing
machinery and obstructions from the required sight lines
Stopping
all machinery, drilling and blasting, pile driving and other work causing
ground vibrations, stopping all smoke, dust, gas etc. hindering view causing
refraction.
Restricting
or stopping traffic of persons and vehicles near instruments or in sightliness
during instrument observations
Providing
an adequate number of laborers experienced as surveying aides and materials as
deemed suitable by the Owner for the control and auxiliary surveys.
Removing
all obstructive accumulation of water
Taking
all necessary safety precautions
Furnishing
and marking materials required in connection with control surveys
Providing
fix points in lieu of or in addition to the Owner's or Contractor's fix-points
in accordance with the instruction of the Owner
Making
all necessary topographic for the verification of lines and grades and quantity
takeoff.
ACCURACY OF SURVEYING
Horizontal
distance shall normally be measured with optic or electronic distance measuring
devices. Chaining with metallic tape shall be restricted to the measurement of
short distances (maximum 30 m) and will be rejected for use in horizontal
distance surveys for traverses.
Angles
shall be measured by theodolite.
Elevations
shall be determined by differential horizontal leveling.
STANDARDS OF ACCURACY - TRAVERSE
|
|
Traverse for additional fixed
point
|
Traverse for setting out
|
|
Number of azimuth courses
between azimuth checks not to exceed
|
25
|
50
|
|
Astronomical azimuth
Probable error of result
|
2”0
|
5”0
|
|
Azimuth closure at azimuth
check points not to exceed*
|
10 sec (N)1/2 or 3.0
sec per station
|
30 sec (N)1/2 or 8.0
sec per station
|
|
Distance measurements accurate
within
|
1 in 15.000
|
1 in 7.500
|
|
After azimuth adjustment,
closing error in position not to exceed*
|
1.67 ft (M)1/2 or 1
in 10.000
|
3.34 ft (M)1/2 or 1
in 5.000
|
N is the
number of stations for carrying azimuth
M is the
distance in miles
* The expressions for closing
errors in traverse surveys are given in two forms.
The expression containing the
square root is designed for longer lines where higher proportional accuracy is
required. The formula which gives the smaller permissible closure shall be
used.
Leveling shall be made as
forward and backward running, between fixed elevations of the basic survey loop
closure on the same bench mark. The difference of the two measurements or of
the measured and fixed elevation shall not exceed 12 mm (K)1/2, where K is the
total leveling distance in kilometers.
VERIFICATION OF WORK
All
relevant elements of survey and setout may be checked by the Owner. The
Contractor shall notify Owner for this check sufficiently in advance of
performing the work. In addition, the Contractor shall assist, if required, the
Owner at any time in the performance of the verification work. The Contractor
shall keep clear all marks and sightliness required for this purpose.
Checks
shall usually be made during work breaks, but in cases of urgency, the
Contractor shall restrict or stop affected work without being entitled to extra
payment. Any control by the Owner shall not relieve the Contractor of his full
responsibility for the accuracy of the position and dimensions of the work and
parts thereof.