OSP Fiber Optics Civil Works: A Comprehensive Guide to Outside Plant Construction and Installation
The deployment of fiber optic networks across vast geographic distances requires far more than the optical cable itself. The civil works that underpin every outside plant (OSP) fiber optic installation — the trenching, ducting, manhole construction, aerial pole erection, cable blowing, hauling, and reinstatement — collectively determine whether a network will deliver decades of reliable service or succumb to premature failure. Drawing on the Fiber Optic Association's (FOA) authoritative Civil Works Guide, this article presents a scientifically rigorous and practically detailed examination of every phase of OSP fiber optic civil construction, from the fundamental properties of optical fiber through to the most advanced installation techniques in use across the telecommunications industry today.
Optical Fiber Fundamentals for OSP Applications
Since the introduction of optical fiber in the 1970s, glass-based communication has revolutionized telecommunications by transmitting more information over greater distances than copper conductors could ever achieve. The operating principle is elegantly simple: a laser source switches on and off at extraordinary speeds, with each flash representing a bit of information. Modern networks typically transmit at a minimum of 10 gigabits per second from a single laser, and laboratory demonstrations have achieved 31 terabits per second over 7,200 kilometers on a single fiber using 155 channels at 200 gigabits per second each, with optical amplifiers spaced every 100 kilometers. This capacity, combined with immunity to electromagnetic interference, absence of electromagnetic emissions, corrosion resistance, inherent security against eavesdropping, and effectively future-proof scalability, explains why fiber has become the universal medium for high-capacity data transport.
Optical fiber is manufactured in two primary types: single-mode (SM) and multimode (MM). Fiber dimensions are expressed using two numbers, such as 9/125 or 62.5/125, where the first number denotes the core diameter in microns and the second denotes the combined core and cladding diameter. Both single-mode and multimode fibers share an overall cladding diameter of 125 microns, making them visually indistinguishable — only the core size differs. The core, typically composed of silica doped with germanium, carries the light signal. The cladding, made of pure silica with a slightly lower refractive index, traps light within the core through total internal reflection. A buffer coating, removed only during splicing or connectorization, serves as a shock absorber protecting the core and cladding from mechanical damage.
Cable Construction for Outside Plant Environments
OSP cable jackets are predominantly manufactured from polyethylene (PE), chosen for its durability in buried and aerial environments. Because raw PE degrades under ultraviolet exposure, carbon black is compounded into the material to absorb UV radiation and dissipate it harmlessly. Jacket colors other than black may be used for identification purposes, though black remains the standard for outdoor applications. Cable jackets must be marked with the manufacturer's name, month and year of manufacture, sequential meter markings, fiber type, fiber count, and a telecommunications handset symbol. Cables lacking these markings will not pass quality inspections and should not be installed.
Strength members within fiber optic cables serve critical mechanical functions. Aramid fibers, commonly known by the DuPont trade name Kevlar, provide tensile strength when cables are pulled into ducts. During installation, tension is applied to the Kevlar rather than to the optical fibers themselves, preventing stress-induced damage. In some cable designs, fiberglass or steel rods serve as stiffening members, improving impact resistance and controlling bending behavior. The choice of strength member depends on the cable's intended application, with factors including impact resistance, flexing characteristics, and bending performance all influencing the design.
Moisture and water blocking is achieved through loose tube cable designs incorporating filling compounds, water-swellable yarns, or gel substances within the cable structure. These materials minimize the penetration of water along the tube in the event of damage. This protection is particularly important in climates where freeze-thaw cycles occur, as water expands by approximately nine percent upon freezing, and repeated cycling can cause cumulative mechanical damage to the cable structure.
Microtechnology and High-Density Fiber Solutions
The evolution of microduct and microcable technology has dramatically increased the fiber density achievable within a given duct cross-section. Microducts, manufactured from high-density polyethylene (HDPE), are typically installed as bundles within larger ducts, providing multiple independent pathways for future cable installations without the need for additional civil works. This approach represents an economically sensible strategy, as the marginal cost of installing additional microducts during initial construction is far lower than the cost of reopening trenches at a later date.
Microcables exploit 200-micron coated fibers, whose cross-sectional area is approximately 46 percent smaller than conventional 250-micron coated fibers. This reduction enables a cable with an 8-millimeter outer diameter to contain 144 fibers, whereas a few years ago a 12-millimeter cable was required for only 48 fibers. Microcables are specifically designed for jetting installation, with HDPE outer sheaths that minimize friction against the inner surface of microducts. Their stiffness properties are engineered to prevent buckling while allowing negotiation of modest directional changes along the jetting route. Central tube microcable designs provide the highest fiber density, with individual fibers bundled into groups of twelve within the cable's central tube, identified by colored binders in accordance with EIA/TIA-598B color coding standards.
Environmental Management and Planning
Every OSP construction project must begin with a site-specific Environmental Management Plan (EMP), prepared by the contractor and submitted for approval prior to commencement. Each site presents unique environmental challenges, and the EMP must address activity-specific issues including storm water management, dust and air pollution control, noise mitigation, traffic management, tree protection, and archaeological preservation. An Environmental Control Officer (ECO) should be appointed to oversee compliance, conduct weekly site visits, review rehabilitated areas, maintain incident logs, and produce monthly compliance reports. The ECO possesses authority to issue non-compliance reports and, in cases of serious environmental infringement, to institute temporary work stoppages.
Wayleaves and Rights of Way
A wayleave — known in some jurisdictions as a right-of-way or easement — constitutes permission to use another party's property for infrastructure deployment. No telecommunications equipment may be installed without a valid wayleave agreement, and copies must be maintained on site at all times during construction. Contractors must familiarize themselves with all standards and special conditions stipulated in the permit. Given that wayleave documentation may not perfectly reflect actual ground conditions, a pre-build survey to verify the exact location of existing services is essential. This verification process has repeatedly proven its value in identifying discrepancies before trenching commences, preventing costly and potentially dangerous encounters with unrecorded utilities.
Health and Safety in OSP Construction
The inherent hazards of OSP construction — deep excavations, heavy machinery, aerial work, confined space entry, and proximity to existing utilities — demand rigorous health and safety management. Before any construction work begins, a competent person must perform a written risk assessment identifying activity-specific hazards, evaluating and ranking each risk, and determining the most effective mitigation strategy. The hierarchy of risk control dictates that hazards should be eliminated where possible, and where elimination is not feasible, minimized through engineering controls, administrative procedures, and personal protective equipment.
All personnel on site must wear appropriate PPE including protective overalls, steel-toed safety boots, hard hats, safety glasses, work gloves, and high-visibility vests when working near roadways or at night. A comprehensive site safety file must be maintained, containing the notification of construction work, health and safety policies and plans, environmental policies, emergency plans, risk assessments, induction records, inspection registers, and incident records. Every employee, manager, and visitor must undergo site-specific induction training before entering the work area, with records maintained for the project's duration.
Trenching Methodology and Standards
Pre-Build Survey and Route Verification
The pre-build survey represents the single most effective risk mitigation activity in OSP civil works. Using the information presented on pre-build drawings, the survey team walks the pegged-out route on foot to verify soil classifications through visual and manual testing at one-kilometer intervals, confirm the location of above-ground and below-ground utilities, note changes in gradient and direction, identify landmarks at directional changes, photograph all obstacles, verify handhole (HH) and manhole (MH) positions, and record all crossings with other services. The survey equipment includes a digital camera, GPS with tracking functionality, Dynamic Cone Penetrometer (DCP) tester, tape measure, measuring wheel, and route drawings from the client. This information forms the basis of the build plan, enabling the contractor to ensure that necessary equipment and resources are mobilized before trenching begins.
Trench Depth and Width Specifications
Trenches must be excavated to a depth that provides at least 800 millimeters of backfill cover over the crown of the uppermost duct in all soil conditions, except where hard rock is encountered. In hard rock conditions, the minimum cover may be relaxed to 300 millimeters, but this reduced depth requires protection through a concrete slab — either pre-cast or cast in situ — placed on top of the padding material before backfilling. The standard protection slab measures 75 millimeters thick by 300 millimeters wide by 900 millimeters in length, with a strength of 20 megapascals reinforced with high-tensile wires. Before pouring any concrete, a slump test must be performed and documented photographically. For dry concrete mixes, the acceptable slump range is 25 to 50 millimeters, while wet concrete may exhibit slump values of 150 to 175 millimeters.
Trench width is determined by the duct diameter and the number of ducts to be installed. Trenches that are too narrow prevent proper duct installation and compaction, while excessively wide trenches increase costs unnecessarily and allow excessive duct snaking from reel memory. When no specific width is prescribed, typical dimensions based on duct count and diameter should be applied.
Pilot Holes and Utility Location
Pilot holes, dug at 30 to 50 meter intervals along the pegged-out route — particularly at points where the new trench crosses existing services — represent one of the most effective methods for locating underground utilities and determining the trench position relative to other services. These pilot holes should be at least 150 millimeters deeper and wider than the proposed trench. Ground Penetrating Radar (GPR) provides an additional fail-safe method for identifying underground services and geological formations before excavation begins. Cable locators can find the exact path and estimate the depth of utility services, and hand excavation must be used to uncover known services before mechanical excavation commences. The contractor bears full liability for any damage to existing services, and such damage must be reported immediately to the project manager.
Trench Shoring and Deep Excavation Safety
Where trench depth exceeds 1.2 meters and workers must enter the excavation, adequate protective measures are mandatory. Three basic methods protect against cave-ins: sloping the trench walls, using trench boxes, and shoring. A ladder must be provided as a safe means of access, and barricades with warning signs must be placed at safe distances from excavation edges to protect unattended openings. No person may work alone in a trench exceeding 1.2 meters in depth, and machinery must never be positioned near excavations where exhaust fumes could contaminate the below-ground atmosphere.
Special Trenching Conditions
Trenching near kerbs, guttering, paving, and driveway crossings requires proper support for these structures until tunneling and backfilling are completed. Where tunneling is not feasible, existing concrete paving must be neatly cut with an angle grinder to produce smooth, uniform edges. Paving blocks must be carefully removed for reuse, re-laid on a sand bedding, and reinstated to original condition or better.
Road crossings require notification of the relevant road authority 48 hours before work begins, with directional drilling being the preferred method. The crossing angle should be as near to a right angle as possible, the minimum depth under any road is 800 millimeters, and ducts must extend at least 0.5 meters beyond the road edge. Stream and river crossings traditionally use 100-millimeter galvanized steel duct to accommodate sub-ducts, with cement blocks cast at both ends to prevent washout. Bridge crossings should first explore the use of existing ducts or service culverts, with any attached ducts not affecting the bridge's load-bearing capacity or clearance.
Where trenching occurs near power cables, a minimum horizontal separation of 600 millimeters and vertical separation of 300 millimeters from any high-voltage cable must be maintained. Where this separation cannot be achieved, concrete protection slabs must be installed between the duct and the power cable. On steep gradients, sandbags placed at five-meter intervals prevent backfill washout, and the risks of land instability on embankments require specialist geotechnical investigation.
Duct Installation and Backfill
Duct Uncoiling and Placement
Ducts must never be uncoiled without the use of a vertical or horizontal de-coiler, which prevents twisting, bending, and kinking during installation. The de-coiler allows the duct to unwind in a single plane, with containment straps on the coil only cut after the coil is secured within the de-coiler. Two methods are commonly employed: the moving trailer method, where a trailer moves slowly along the trench route while unwinding and placing the duct, and the pulling method, where the duct is pulled by hand or mechanical pulling machine using a pulling grip or basket grip.
Ducts are laid in a straight line between manholes and handholes, with directional changes kept to a minimum. Where directional changes are unavoidable, the bending radius must be as large as possible, and offsets must be in the same direction to avoid creating S-bends. Individual duct lengths may be offset by no more than 35 millimeters, and the maximum overall deviation between MHs or HHs must not exceed 15 degrees. Spacers should be used when placing multiple ducts in a trench to prevent twisting and maintain straight alignment, which reduces cable jetting and pulling tensions.
Bedding, Padding, and Backfill
Bedding material forms the even floor of the excavated trench onto which ducts are laid. Both bedding and padding materials should pass through a sieve and consist of granular, non-cohesive material graded between 0.6 and 19 millimeters. Padding is compacted manually using a hand tamper, as inadequate side support from poorly compacted padding significantly increases the probability of duct buckling.
After padding compaction, backfilling proceeds using excavated material provided it contains no stones larger than 150 millimeters in diameter, trash, or organic matter. Backfill is installed in layers not exceeding 300 millimeters, with each layer compacted before the next is added. After compacting the first backfill layer, warning tape is placed approximately 300 millimeters below the eventual ground surface, directly above the cable, and this procedure must be photographed as proof of compliance. Manual compaction continues until ducts are covered by 150 millimeters of padding and 300 millimeters of backfill, after which a vibratory plate compactor may be used. The final backfill layer must be compacted to a density at least equal to that of the surrounding virgin soil.
Dynamic Cone Penetrometer Testing
Upon completion of backfilling, a DCP test must be performed and documented. Testing frequency is every 15 meters for standard trenches, increasing to every 5 meters for trenches in road reserves or under footpaths. The benchmark for acceptance is penetration of less than 100 millimeters, with blow count thresholds varying by location: verges require 2 blows, footpaths 3 blows, and roadways 5 blows per 100-millimeter penetration increment. Subject to consistent satisfactory results, testing frequency may be reduced following consultation with the relevant authority.
Direct-Buried Installations
Direct-buried installations require armored cable to provide crush and rodent protection. In open or rural areas with few obstacles, ploughing represents the most economical installation method, while urban environments with numerous underground utilities favor hand trenching. A trench no wider than 375 millimeters suffices for armored cable alone, excavated to 1.2 meters depth or as specified in the wayleave. The plough tractor must start slowly, increasing speed only after cable slack is taken up, and operations must be continuously monitored for obstructions, proper cable feeding, specified depth, and route adherence. Each plowed section must be checked with an Optical Time-Domain Reflectometer (OTDR) for potential damage before further work proceeds.
Earthing, Bonding, and Surge Protection
The armor of optical fiber cables must be lugged and bonded to an earth bar using a soft multi-stranded 6-square-millimeter green/yellow insulated bonding cable, with bonding cables kept as short as possible and free of sharp bends. Bonding — the multiple connections to metallic parts at every joint forming a continuous electrical path — and grounding — connecting that path to earth — together ensure the safe dissipation of unwanted electrical current. While optical fiber cables do not carry electrical power, the metallic components of conductive cables can transmit current induced by nearby power lines or fault conditions. Proper grounding and bonding protects personnel, property, and equipment, and is required by electrical codes and equipment manufacturers.
The grounding procedure involves scoring the outer sheath of the armored cable approximately 25 millimeters with a cable knife, sliding the base plate under the armor, placing the top plate over the base plate and tightening the lock nut, then covering the grounding clamp and exposed sheath with vinyl tape before connecting to the ground system.
Manholes and Handholes
Manholes and handholes must be positioned as far from road junctions as possible and constructed to prescribed dimensions and specifications. Before concrete placement, shuttering must be examined for firmness and correct positioning, and all foreign matter removed. The concrete mix must achieve 20 megapascals strength at 28 days, using a 2.5:2.5:1 ratio. Duct entry points must be drilled without cracking the surrounding structure, with ducts entering and exiting in line with the route direction to allow through-coupling without effort. Ducts must never enter and exit on the same wall.
Where brick construction is permitted, only baked quality clay bricks from approved manufacturers may be used, with every third layer reinforced, double brick wall thickness minimum, external waterproofing, and approved frame and cover fittings. External labeling must be on the coping rather than the lid, as lids may be damaged and replaced. GPS coordinates of all MHs and HHs must be recorded for as-built documentation.
Safe Manhole Entry Procedures
Entry into manholes requires strict safety protocols. At least two persons must be present, vehicles must be positioned to avoid creating traffic hazards, and barricades and cones must be clearly visible. Water is poured around the lid before opening to prevent spark generation. Before entering the confined space, testing at three levels — bottom, middle, and top — must check oxygen content, flammable or explosive gases, and hydrogen sulfide, with each level tested for a minimum of 60 seconds using an approved, calibrated gas detector. The gas detector must remain operational throughout the work period, constant ventilation is required, and fusion splicing inside a HH or MH is strictly prohibited.
Trenchless Installation Methods
Horizontal Directional Drilling
Horizontal directional drilling (HDD) provides the preferred method for crossing roads, highways, railway lines, rivers, and other services where conventional trenching would be dangerous or costly. The process involves three stages: pilot drilling along a steered path, reaming the pilot hole to the required diameter, and pulling back the duct through the reamed borehole. The back reamer is approximately 20 percent larger than the duct to be installed, and the duct is attached via a swivel connection. The entire operation uses pressurized drilling mud, which carries away spoil and supports the borehole against collapse.
Rigs capable of drilling up to 300 meters in a single operation are available. The minimum ground cover must be at least three times the final borehole diameter and not less than 1.5 meters. At river crossings, the distance between the water bottom and the drilling hole must be at least 10 times the pipe diameter and not less than 3 meters. If drilling accuracy is not specified in the wayleave, the borehole should not deviate more than 40 millimeters in diameter from the predetermined axis. The location and depth of all underground services must be established before drilling begins, as sudden deviations to bypass obstacles are not possible.
Hammerhead Mole
The Hammerhead Mole offers a cost-effective alternative to directional drilling for shorter bores. Both an entrance and exit hole must be dug at the allocated positions, and the mole is inserted in the boring direction. A duct-pulling attachment allows simultaneous boring and duct installation, making the method efficient for straightforward crossings where precision steering is not required.
Cable Installation: Air-Assisted Methods
Jetting and Blowing Principles
Air-assisted cable installation — jetting and blowing — has become the dominant method for deploying fiber optic cables into pre-installed microducts. Both techniques combine a pushing force from hydraulically or pneumatically driven tracks with a pulling force from compressed air, creating an efficient, low-stress deployment that achieves far greater distances than conventional hauling. The key distinction between the two methods lies in how the pulling force is applied: jetting uses a missile or parachute at the cable's leading end, where differential air pressure across the missile head creates a concentrated pulling force; blowing relies on fluid drag of air rushing along the cable length, distributing the pulling force continuously along the entire cable.
A blowing machine with pneumatic drive is recommended for cables up to 15 millimeters in diameter, while hydraulic drive machines suit cables from 14 to 32 millimeters. Typical blowing distances range from 1,000 to 2,000 meters, with installation speeds of 40 to 50 meters per minute under 10 bar air pressure. Smaller diameter and lighter weight cables enable longer blowing distances, while the maximum push force decreases as the duct inside diameter increases.
Duct Integrity Testing
Before any cable is blown, duct integrity must be verified through a four-stage DIT process. First, air testing checks microduct continuity by running the compressor at 10 bars for 5 minutes and confirming airflow at the far end. Second, foam sponge testing cleans the duct by blowing a slightly lubricated, tight-fitting sponge through at 10 bars, repeating if excess water or dirt emerges. Third, shuttle blowing checks for bends, kinks, or blockages using a shuttle with an outer diameter no more than 80 percent of the microduct inner diameter. Fourth, pressure testing checks for coupler leaks or microduct punctures by building pressure to 5 bars, closing the inlet valve, and confirming that pressure does not drop below 4.5 bars within 30 minutes.
Fill Ratio and Lubrication
For optimum blowing performance, the cable-to-duct diameter fill ratio should not exceed 76 percent, as specified by the microduct supplier. Adding a small amount of blowing lubricant to a tight-fitting foam carrier sponge before blowing it through the duct creates a lubricated pathway that yields better results than coating both the duct and cable directly. This counterintuitive finding arises because lubricant on the cable jacket makes it too slippery for optimal laminar-flow jetting — the air pushes on the jacket through friction, and excessively low friction reduces the air's ability to push the cable. Typically, only 0.25 liters of lubricant suffices to coat 2 kilometers of cable.
Cable Slack Management and Bend Radius
Cable bend radius must never exceed specified limits: 10 times the cable outer diameter when installed (no tension) and 20 times the cable outer diameter during installation (under tension). For microducts, the minimum bend radius follows the formula: radius minimum equals 10 times the outer diameter. A total of 17 meters of cable slack — 15 meters for slack plus 2 meters for splicing — is required in each HH or MH housing a splice enclosure. Slack must be coiled clockwise with minimal back tension, tied at 1-meter intervals with tie wraps or PVC tape, and secured to slack brackets on HH or MH walls. The slack of one splice closure must not become intertwined with that of another, and cable slack typically adds approximately 2 percent to the overall link distance.
Figure-Eighting Technique
The figure-eight technique enables bidirectional cable installation from a single drum placement. A figure-eight approximately 5 meters in length, with each loop about 2.5 meters in diameter, is created by paying cable off the top of the reel and loosely weaving it around two traffic cones spaced 5 meters apart on a ground sheet. The large, relaxed loops prevent tangling, and the figure-eight pattern introduces a half-twist on one side that is removed on the other, preventing twist accumulation. After completing the figure-eight, it must be flipped over by a minimum of three people — one at the center and one at each end — to bring the required cable end to the top for the second blowing direction.
Cable Installation: Hauling Methods
While air-assisted installation offers superior performance, cable hauling remains necessary in many situations, particularly with heavy-duty ducts designed for long-haul applications. Before hauling, the maximum allowable pulling tension, minimum bending radii (both during and after installation), cable length, and splicing slack requirements must all be confirmed from the cable specification sheet.
Duct Rodding and Preparation
Duct rodding clears the passage and installs the pulling rope using fiberglass pushrods. The rod is pushed through the duct until it reaches the adjacent HH or MH, the pulling rope is attached, and the rod and rope are pulled back through. Alternatively, the pulling rope can be blown through using air pressure. Duct cleaning follows rodding, using a cylindrical brush or close-fitting mandrel attached to a second rope and pulled through the duct.
Centre-Pulls and Back-Feeding
For long cable runs where installing an entire drum in one operation is impractical, centre-pull and back-feeding techniques provide effective solutions. In a centre-pull operation, the cable reel is positioned near the centre of the duct run, and cable is pulled in one direction to the intended HH or MH. The remaining cable is then figure-eighted, flipped, and pulled in the opposite direction. Back-feeding provides a series of shorter, lower-tension pulls in one direction, utilizing figure-eighting where necessary. Both techniques require synchronized communication directed by a team leader, with members positioned at each HH or MH along the route.
Pulling Tension and Equipment
Pulling tension must be monitored using a dynamometer, with a breakaway swivel serving as a fail-safe to prevent exceeding the cable's maximum tension rating. Cable lubricant is recommended for most hauling operations to reduce friction. An 8-millimeter polyester or polyaramid pull rope is used for hand pulling, while winch hauling requires 12.5-millimeter or thicker rope. Ski ropes manufactured from nylon are unsuitable due to excessive stretch and potential duct damage, and steel hauling rope must never be used. For hauling applications, the cable-to-duct fill ratio should not exceed 65 percent — more conservative than the 76 percent limit for blowing — to account for the higher friction characteristics of pulling installation.
Aerial Installation
Pole Handling and Erection
Aerial fiber optic installation requires careful pole handling, transportation, and erection. Poles must not exceed 0.5 meters vehicle overhang during transport, with a red flag secured on the overhanging end. Pole handling ratios specify minimum crew sizes: 7-meter poles require 4 people, 8-meter poles require 6, 9-meter poles require 8 people or mechanical aid, and poles of 10 meters or more require mechanical assistance. A pole must never be dropped, as impact can damage both the pole and personnel.
Pole holes, approximately 400 millimeters in diameter, must position the survey peg at the center. In rocky conditions where specified depth cannot be achieved, poles may be set in concrete using a 1:3:3 mix (cement:sand:crushed stone) at 15 megapascals strength, with at least 85 millimeters of concrete between the pole and undisturbed ground. Backfilling and ramming during pole planting occurs in 300-millimeter intervals, with plumbness maintained throughout the process.
ADSS Cable Installation
All-Dielectric Self-Supporting (ADSS) cable installation employs two methods. The conventional method fits cable pulley boxes to every pole, feeds a pulling rope through the pulleys, and hauls the cable using a breakaway swivel and hauling eye constructed from the cable's Kevlar strength members. The drum is positioned at least 50 meters from the first pulley to prevent excessive bending, and cable lengths up to 6,000 meters can be erected in a single haul with appropriate terrain. The figure-eight method is used when terrain prevents conventional installation, though it should not be employed for cables longer than 4,000 meters due to the risk of managing coils exceeding 2,000 meters.
ADSS sagging uses the line-of-sight method, with installation sag typically set at 1 percent of span length. The exact distance between poles is established, the far-side pole is marked with colored tape at the appropriate mid-span sag distance, and the installer sights from the first pole to align the cable's belly with the mark on the opposite pole. One or two spans between dead-end locations should be checked using this method. When removing a pulling grip, 3 to 5 meters of adjacent cable must be cut off and discarded to eliminate any portion that may have been damaged during pulling.
Power Crossings and Ground Clearance
Where aerial routes cross power lines, the crossing angle should be as near to 90 degrees as possible, with maximum allowable deviations of 45 degrees for routes below 48 kilovolts and 30 degrees for routes at or above 48 kilovolts. Ground clearance requirements vary by location: 6.1 meters for non-electrified railways and public roads, 6.5 meters for national roads, 7.5 meters for abnormal provincial roads, 4.9 meters for private roads near towns and cultivated farmlands, and 3.7 meters for country roads and private railway lines.
Pre-Installation Cable Testing and Inspection
All optical fiber cables must be tested with an OTDR while still on the drum, prior to deployment. Testing is performed on all fibers in one direction at 1550 nanometers using a 30-nanosecond pulse width, with traces stored and submitted electronically to the project manager. A bullet or divot bare fiber adapter connects the fibers to the OTDR. If a cable is installed without a pre-installation OTDR test, the supplier will typically not accept returns, as the installer is deemed to have assumed liability upon installation.
Cable drum inspection verifies that the correct cable has been procured, checks for weathering or damage, confirms that battens are intact, and ensures that nails, bolts, or screws on drum flange interiors are countersunk. Drums must be chocked to prevent movement, cable ends must be sealed with pre-formed or heat-shrinkable end caps (tape is unsuitable), and the plastic foil wrap must remain in place until installation. Drums rolled for any reason must follow the direction indicated by the arrow marked on the flange.
Reinstatement and Project Closure
Upon completion of backfilling and compaction, all surfaces must be reinstated to their original condition or better. Grassed areas use original turf, replacement turf, or equivalent seed. Footways must be reinstated with the same surfacing materials, reused if undamaged or replaced with similar material. A 12-month guarantee period applies to permanent reinstatement by the wayleave holder, while temporary reinstatement carries a 2-week maintenance period. Any excavation left unattended for more than 5 days may be made safe by the road authority at the contractor's expense. Remedial work is required for depressions causing standing water, humps or crowning, edge depression, or cracking.
Underground routes must be marked with identifiable markers not less than 1.8 meters in length and 100 millimeters in diameter, planted 600 millimeters deep opposite each MH or HH and well compacted. GPS coordinates of all MHs and HHs must be recorded and documented as part of the as-built drawings. Passive electronic markers may be buried at key points during construction to facilitate future locating of underground facilities.