prevent injurious straining of the cable. Where two parallel cables cross,
provide a separation of 100 feet (30.5 m) to avoid fouling and to permit work
space (refer to criteria in the Underground Systems Reference Book).
Burying Cable. In addition to laying cables on the bottom, consider
burying them by the jetwater method. By this technique, the cable is
installed simultaneously with the trenching operation. Several cables or
cables integrally installed in plastic conduits can be installed at the same
time. The installation of cable integrally installed in plastic conduit
provides cable protection and facilitates future replacement.
Anchors. Where a cable crossing is subjected to flow or tidal
currents, anchors are usually required to prevent excessive drifting or
shifting of the cable along the bottom. These anchors can be made fast to the
cable by a series of U-bolts that pass through a common base plate, thus
affording a multiple grip. Either U-bolts, eyebolts, or other means may be
provided for attachment of the anchor cable or chain. Ordinarily, anchors are
masses of concrete large enough to resist current drag.
Warning Signs. Provide suitable warning signs to indicate the
locations of the shore ends of a submarine cable. These signs should state
that ship anchoring is prohibited in the immediate vicinity of the cable.
Signs are required for every submarine cable crossing.
Pile Clusters. Frequently clusters of piles are driven on the
upstream side of important cables where they enter and leave the water. These
clusters supply visual aid in locating the points where the cable is anchored.
Clusters also provide a certain amount of mechanical protection for
the cables, and furnish platforms on which to mount warning signs.
Maps. The development of accurate maps is one of the most important
steps in an extension of a submarine cable installation. Maps indicate the
exact location of the cable at various points along its length, as established
by surveying instruments. To estimate cable movement or drifting on the
bottom, the maps must also indicate the exact length of the cable installed
between any two reference points.
Cable Types. Lead-sheathed cable is generally used for submarine
installations and is usually armored. Insulations shall be Cross-linked
Polyethylene (XLP) or Ethylene-Propylene-Rubber (EPR) except where the paper-
insulated type is justified because it has qualities neither XLP nor EPR
Metallic-Sheathed Cable. Cables usually are sheathed with copper-
bearing lead, but other alloys may be required where special conditions
warrant nonstandard sheathing.