access roads & structure pads sesp12211

ACCESS ROADS

AND STRUCTURE PADS

Approved by the Engineering Standards Committee (ESC) on

18 Rajab 1423 ( September 25, 2002)

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SEC-ERB ENGINEERING STANDARDS SES-P-122.11

SEC-ERB – 16344-1 ( 11/07 ) SEP12211R2/SZA PAGE 11: 1 OF 22

ORGINATED

By: FSP

DATE: 10/08/28

CERTIFIED

By: RRB

DATE: 10/08/28

APPROVED By: ASA/KK

DATE: 10/08/29

T/L

DES

IGN

STD

S

فــرع المنطـقـة الشـــرقيــةEastern Region Branch

الشـرآة السعـودية للكهرباءSaudi Electricity Company

SEC-ERB ENGINEERING STANDARD SES-P-122.11

PAGE 11: 2 OF 22 SEP12211R2/SZA


ة للكهرباءالشـرآة السعـوديSaudi Electricity Company

TABLE OF CONTENTS

1.0 SCOPE 2.0 GENERAL 2.1 Requirements 2.2 Geotechnical Information 2.3 Plan and Profile Drawings 3.0 TRANSMISSION LINE ACCESS ROADS 3.1 Geometric Design Criteria 3.2 Access Road - Earthwork Requirements 3.3 Road Intersections 3.4 Routes 3.5 Pipeline Crossings 4.0 STRUCTURE PADS 4.1 Design Criteria 4.2 Finger Roads and Pads 5.0 SLOPE PROTECTION AND SAND CONTROL 5.1 Oil or Emulsified Asphalt 5.2 Rip-rap or Concrete Barrier 6.0 BIBLIOGRAPHY FIGURE 1: ACCESS ROAD AND PAD FOR STEEL TOWER (TT, SA,LA TYPE) FIGURE 2: ACCESS ROAD AND PAD FOR STEEL TOWER (MA, HA, AS TYPE) FIGURE 3: ACCESS ROAD AND PAD FOR H-FRAME STRUCTURES FIGURE 4: ACCESS ROAD AND PAD FOR MONOPOLE STRUCTURES FIGURE 5: ACCESS ROAD AND PAD FOR GUYED H-FRAME STRUCTURES FIGURE 6: ACCESS ROAD AND PAD FOR GUYED MONOPOLE STRUCTURES FIGURE 7: TYPICAL INTERSECTION FIGURE 8: UNPAVED CROSSING FOR ABOVE GRADE PIPELINES FIGURE 9: FINGER ROAD AND PAD FIGURE 10: FINGER ROAD ALONG MAIN ROAD / HIGHWAY





1.0 SCOPE This Standard establishes the specific parameters and procedures for the design of

unpaved access roads, structure pads, and slope protection from erosion/ encroachment of transmission line right-of-ways.

2.0 GENERAL 2.1 Requirements Access to the transmission line right-of-way and along the transmission line

requires various operations including construction of road approaches, filling of ditches, dozing trails, and other works depending on the type of terrain. Suitable road approaches are required for safe access of equipment and vehicles. Proper surface drainage shall be provided. For easier accessibility during construction and later for inspection, operation and maintenance of the transmission lines, unpaved access road shall be located as near as possible to transmission lines.

All access roads, finger roads and structure pads shall be permanent for Company

maintenance and operation purposes. 2.2 Geotechnical Information Detailed soil investigation conducted along the centerline of the proposed

transmission line shall serve as reference in the design of access road. The soil report, based on the investigation shall include the following:

2.2.1 Soil boring logs, sampling and testing 2.2.2 Ground surface and Ground Water observations 2.2.3 Moisture-Density relationship (Compaction details) 2.2.4 CBR Test plots including CBR vs Dry Density 2.2.5 Recommendations 2.3 Plan and Profile Drawings The design of unpaved access roads and structure pads shall make use of the

transmission line plan and profile drawings which show the left or right profile at 15-20 meters away from the transmission line centerline.





3.0 TRANSMISSION LINE ACCESS ROADS The unpaved transmission line access roads shall be designed for adequate traffic

volumes to assure the safe movement of construction and maintenance equipment along the right-of-way. Design of access roads shall take into account the grade and topographical conditions of the terrain to be traversed and shall be in accordance with the following requirements:

3.1 Geometric Design Criteria 3.1.1 Design Speed The geometric design features shall be consistent with a design speed of

48 km/h for the Transmission line access road for all types of terrain conditions.

3.1.2 Sight Distance The minimum stopping sight distance shall be 61 meters based on the

design speed. Coefficient (K) values of 28 for crest vertical curve and 35 for sag vertical curve shall be used in determining the length of vertical curves.

K value is a coefficient by which the algebraic difference in grade shall be

multiplied to determine the length of the vertical curve which will provide smooth transition between tangent grade changes.

3.1.3 Maximum Grades The maximum grades for different types of terrain based on the specified

design speed shall be the following: Type of Terrain Maximum Grade a. Flat 10.5% b. Rolling 13.5% c. Mountainous 15.0% 3.1.4 Roadway Width The minimum width of the unpaved access road shall be 5.00 meters.





3.1.5 Side Slopes The maximum side slope shall be 4 horizontal to 1 vertical. The

intersection of fill slope and cut slope planes shall be well rounded. The cut slope shall be designed with adequate and well rounded ditches.

3.1.6 Minimum Clearances a. The minimum horizontal distance from the centerline of transmission

line to the nearest edge of the access road shall be 15 meters as indicated in Figure 1.

b. The minimum vertical clearance between the highest point on the road

surface and the lowest conductor of the overhead transmission lines shall conform to SES-P-122.09.

3.1.7 Path Required by Company Vehicle (10-meter long truck for line wash) a. Turning radius 14.0 m b. Max. angle of approach and departure 30 degrees c. Max. ramp breakover angle 10 degrees 3.2 Access Road - Earthwork Requirements The typical cross-section of access road shall consist of subgrade, subbase, and

surface (base) courses. The requirements are given below: 3.2.1 Subgrade a. Clearing site and rough grading shall be per SCS-Q-002. An average

of about 200 mm top soil shall be removed from the subgrade, and transported to and disposed off from the site at SEC-ERB designated dumping grounds.

b. Any depressions below subgrade level due to removal of un-suitable

material shall be filled with general fill per SCS-Q-002. c. The original ground (subgrade) shall be scarified and compacted to

200 mm depth. Compaction shall be per SCS-Q-002 as specified for Light Traffic roads.





The compacted California Bearing Ratio (CBR) at laboratory for subgrade material after four days of soaking as determined by ASTM D1883 shall not be less than 15.

d. The subgrade shall be finished to conform to the required alignment,

grade and cross-section of the access road. e. In areas where the existing subgrade material has a CBR value of less

than 15, subgrade modification shall be done to improve the CBR to a minimum of 15 after 4-days soaking.

3.2.2 Subbase a. Subbase material shall be Class C per SCS-Q-002. It shall be clean,

free of organic and other deleterious substances. The CBR value of the material shall not be less than 50.

b. Compaction shall be per SCS-Q-002 as specified for Light Traffic

roads. Thickness of each layer shall not exceed 150 mm after compaction.

c. The thickness of the subbase material shall be a minimum of 1.5 m in

Sabkha area to protect the wearing surface from detrimental effects of capillary movement of the ground water. The thickness of the subbase material in areas other than Sabkha shall vary depending on the type of terrain to avoid abrupt changes in the finished grade and to provide smooth riding surface.

3.2.3 Surface (Base) Course a. Material Surface course material shall be Class C per SCS-Q-002. It shall be

free of organic matter, rubbles, cobbles, boulders and other deleterious substances. CBR value for surface course (base course) material shall not be less than 50.

b. Placement and Compaction Surface course shall be minimum 300 mm thick and the material shall

be placed in layers of uniform thickness with approved spreaders. Layer thickness generally shall not exceed 150 mm after compaction. Compaction shall be per SCS-Q-002 as specified for Heavy Traffic roads. The water content of the material shall be maintained during





placement at the optimum percentage (± 1½%) as determined by ASTM D 1557. Vibratory compactor or other approved types of special compacting equipment may be used.

c. Finish The surface of the compacted material shall be finished by blading or

with automated equipment specially designed for this purpose and rolled with a steel-wheeled roller. Thin layers of fine materials shall never be added to the top layer of the surface course in order to meet the grade.

d. Tolerances The top of the completed Surface course shall not show any deviation

in excess of 20 mm when tested with a 3-meter straightedge. The completed thickness of the surface course shall be with in ± 20 mm of the design thickness of 300 mm.

3.2.4 Fill materials, including water used during compaction, shall have

chloride and sulfate contents equal to or less than the existing soil. Sea water shall not be used for compaction.

3.3 Road Intersections Road intersections or access road crossings are locations where roads cross each

other at a common elevation. The typical plan layout of intersection shall be as shown on Figure. 7. Adequate advanced warning of the intersection and traffic directional arrows and signs shall be provided as below:

3.3.1 Warning Signs The STOP or YIELD sign shall be installed to control traffic. These shall

be per Ministry of Communications signs and shall be placed on the access road at least 100 meters before the intersection.

3.3.2 Caution Signs The caution signs "WARNING ROAD CROSSING AHEAD, SLOW

DOWN", shall be provided at least 100 meters before the intersection and "SEC-ERB RIGHT-OF WAY; DO NOT ENTER" shall be provided at the barriers. The Sign boards shall be of 2.0 m x 1.0 m X 3 mm thick anodized aluminum plate, supported suitably by two 50 mm galvanized schedule 40 pipes. The top level of the sign boards shall be 2.0 m from the





ground level. The lettering shall be in English and Arabic languages of 50 mm height in reflective Aluminum color in blue background.

3.3.3 Chain and Barrier Post (with locking arrangement) Chains and barrier posts shall be located as shown in Figure 7. Chains and

barrier posts shall be painted with Zinc Yellow (RAL 1018) and Traffic Black (RAL 9017) stripes of reflective paint, to be visible at night, to prevent any untoward incident. Barrier post shall be steel pipe filled with concrete of minimum 400 mm diameter and 2.5 meters length. This shall be embedded one (l.0) meter in depth. Chain shall be of 6 mm size and grade 43 Steel. The chain shall be fixed at one end of the barrier. A closed hook to be provided at the other end of the barrier post for locking purposes.

3.3.4 Crash barriers Crash barriers shall be provided to protect any fence, boundary wall,

culvert, or any other utilities which are close to the transmission line structures. Crash barriers shall be per SES-P-119.19.

3.4 Routes Access roads shall be routed within the right-of-way of the proposed transmission

lines.

3.4.1 If an access road already exists within 30 meters from the proposed transmission line, only finger roads need to be constructed to get access to the new transmission line tower.

3.4.2 The existing access road shall be upgraded per requirements of this

standard. Precautionary measures to be taken to avoid any damage to the existing access road. Any damage during construction shall be repaired/ rectified without any cost to SEC-ERB.

3.4.3 Existing MOC and Municipality roads shall not be used as transmission

line access roads.





3.5 Pipeline Crossings Pipeline crossings shall be designed to provide safe passage of vehicular traffic.

The design of the crossing shall meet the following requirements unless otherwise specified by the owner of the pipeline to be traversed.

3.5.1 The minimum basic wheel load for the pipeline crossings shall be seven

(7) metric tons. 3.5.2 The crossing shall be made perpendicular to the pipeline as much as

possible. However, if such perpendicularity could not be met as dictated by the site condition, the crossing angle shall not be less than 45 degrees.

3.5.3 The pipeline shall be protected against damage from vehicle collision by

means of at least 1 m high stabilized earth berm over the pipe and extending 30 meters beyond both edges of the road (measured perpendicular to the road).

3.5.4 Backfill material shall be the same material as that of access road (as

specified in section 3.2) and shall be free of material that may damage coatings of steel pipe. Backfill shall be placed in layers of 300 mm or less and the degree of compaction shall be same as for the access road.

3.5.5 Unless otherwise specified, the minimum cover over steel pipes shall be

1500 mm for unpaved road crossing. 3.5.6 The minimum width of the crossing shall be 5.00 meters, excluding the

side slopes. The typical pipeline crossing details are shown on Figure 8. 4.0 STRUCTURE PADS 4.1 Design Criteria The standard earthwork requirements of the subgrade, subbase and surface (base)

course for the design of transmission line structure pads shall be same as for access roads, (as stated in section 3.2 of this Standard) along with the following requirements:

4.1.1 The edge of the pad shall have a minimum distance of fifteen (15) meters

from any point of the structure foundations and / or guy anchors.





4.1.2 The maximum side slope shall be 4 horizontal to 1 vertical. Side slopes shall be as flat as possible, to increase safety by providing additional maneuver area in emergencies and maintenance work.

4.1.3 Structure pads shall be graded to drain water away from structure

foundations with slope of 1.5 to 2 percent. 4.1.4 For concrete foundation, top elevation of concrete footings shall be 450

mm above finished grade of the structure pads. 4.1.5 Wherever the transmission line is passing through Sabkha, water logged,

flooded or swamp areas; the filling shall be done to get structure pad at minimum elevation of 1.5 meters above the surrounding area.

4.1.6 The typical design drawings of structure pad for different transmission

line towers shall be as shown in Figure 1 to 6. 4.2 Finger Roads and Pads The typical details of finger road and structure pad are as shown in Figure 9.

Finger roads shall not be taken from existing MOC and Municipality roads. In cases where it is unavoidable, finger roads shall be developed as shown in Figure10.

5.0 SLOPE PROTECTION AND SAND CONTROL Protection of slopes adjacent to structure pads to be done where such slopes are liable to

be washed away or eroded by wind. Erosion control is required when slope or excavation is steeper than 1½ horizontal to 1 vertical. Slopes shall have contour trenches for each 2.0 meters change in elevation. These shall be 0.4 meters deep and of rough construction.

The following are the recommended methods of slope protection and sand control. 5.1 Oil or Emulsified Asphalt Sand encroachment/ erosion on the structure pads and access roads shall be

prevented by spraying the specified areas along the right-of-ways with crude oil or other approved compound such as slow setting asphalt emulsion meeting the requirements of ASTM D 2397 for CSS-IH, to stabilize the surface.

The crude oil shall penetrate a minimum of 12 mm which requires approximately

8.0 liters/sq. m, of surface. Emulsified asphalt shall be applied per manufacturer's recommendations.





5.2 Rip-rap or Concrete Barriers In Wadi areas where ground water level is high, or in areas submerged with

water, rip-rap or concrete barrier/lining shall be constructed within right of way to protect access roads and structure pads from erosion.

5.2.1 Rip-rap shall be placed on the slopes of structure pads and in places along

the slopes of access roads where erosion control is required, and shall be of durable stones or hard rocks. Rip-rap shall be uniformly distributed to produce a compact rip-rap with a minimum thickness of 300 mm. The minimum specific gravity of stone shall be 2.5 and the maximum absorption shall be six (6) percent. The loss by abrasion shall not be greater than 45% when subjected to 500 revolutions in a Los Angeles Abrasion Machine in accordance with ASTM C131.

5.2.2 Concrete barriers shall be designed to protect the slopes of structure pads

from erosion. 5.2.3 For small stretches of access roads which are lower than the normal level,

and where there is difference of levels on two sides of access road, box or pipe culverts with wing walls shall be used. The concrete shall be severe exposure type per 71-SMSS-5. The design to be done based on site conditions and shall be approved by SEC-ERB.

6.0 BIBLIOGRAPHY 6.1 Highway Engineering Standard Handbook for Civil Engineers by Frederick S.

Merritt 6.2 Geometrical Design Guide American Association of State Highway and

Transportation Officials (AASHTO) 6.3 ASTM D 1241 Specification for Materials for Soil aggregate Sub-base,

Base and Surface Courses 6.4 ASTM D 2397 Specification for Asphalt Emulsion 6.5 SAES-L-046 SAUDI ARAMCO Engineering Standards for Pipeline

Crossings under roads and rail roads. 6.6 SCS-P-122 SEC-ERB Transmission Line Construction Standards 6.7 SES-H-001.01 Paint Color Codes and Standards





6.8 SES-P-122 SEC-ERB Transmission Line Design Standards 6.9 SCS-Q-001 SEC-ERB Standard for Paving Asphalt Concrete 6.10 SCS-Q-002 SEC-ERB Standard for Earthwork

access roads & structure pads sesp12211

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