Abstract: An apparatus for dispersing chemicals into an underwater pipe comprising first and second chemical feed pipes, the feed pipes being mounted to an intake pipe forming part of the underwater pipe, the first feed pipe extending along the length of the intake pipe and being connected to the second feed pipe, the second feed pipe being mounted to the intake pipe at that portion of the intake pipe adjacent an intake pipe opening, the second feed pipe including a plurality of inwardly extending releasing valves for dispensing chemicals into the intake pipe, the chemicals being delivered to the second feed pipe through the first feed pipe. A cone-shaped device is also disclosed for inserting the first chemical feed pipe into the intake pipe, the cone-shaped device having first and second cone elements coaxially spaced apart to form an air pocket therebetween.

Abstract: A process and apparatus for forming a wood grain simulation pattern on surfaces of synthetic articles such as synthetic lumber planks. The articles are fed along a predetermined path on a conveyor surface. A plurality of cutting blades are disposed about the periphery of a rotatable cylindrical element supported on a drive shaft. As the synthetic article is fed under the rotatable cylindrical element which is in rotation, the blades which are disposed across an outer surface of the article on which a grain simulation is desired, cut a plurality of short slits spaced laterally from one another in an offset pattern. These slits extend along the feed axis of the article and simulate a wood grain in the outer surface thereof.

Abstract: The invention relates to an apparatus for laying pipe and/or drainage tile at a desired depth below ground, and a preferred level grade within a trench. The invention maintains the placement of the pipe and, upon substantial completion of backfilling operations of the trench, may be removed for reuse. The invention includes a shaft having an adjustable sleeve and an adjustable pipe-grasping sleeve adapted for engagement to a variety of sized pipes and/or drainage tile. The invention may be securely placed into a trench by manual manipulation of the handles and/or by striking of the strike plate with a hammer. The invention is designed for fast and convenient removal from a trench.

Abstract: To rehabilitate an internally corroded underground pipeline, excavations are made at its opposite ends to which launching and receiving pipe structures are then secured. Various pig member sets, with appropriate treatment fluids carried thereby, are air-driven through the entire length of the pipeline to successively acid clean, etch, and neutralize its interior surface. The interior pipeline surface is then thoroughly dried by flowing dehydrated air through the pipeline. Specially designed leading and trailing extruder pigs, with 100% solid, high viscosity, solvent-free epoxy coating material therebetween, are then air-driven through the pipeline to extrude a first protective coating layer onto its interior surface. The first layer is then dried with dehydrated air.

Abstract: A cut-off material is provided, which includes an impermeable cutoff member (10, 70) provided with an expandable hose portion (18, 72) and a flange portion (20, 74) formed integrally with one end of the hose portion. The cutoff member is disposed in first and second pipelines, so that the flange portion is positioned within the first pipeline (12) and that the hose portion is positioned within the second pipeline (14). The cut-off member is maintained, for example, by a base (24,54,82) that is wound to be radially expandable, so that the flange portion is brought into liquid tight contact with the inner surface of the first pipeline and the hose portion extends within the second pipeline.

Abstract: Both a system and a method are provided which allows an eddy current probe to accurately determine both the proximity and dimensions of non-conductive structures which are normally invisible to such probes. The system includes a portable target medium that is movable into a known position with respect to the non-conductive structure, and that includes a conductive material that couples strongly with a fluctuating magnetic field, and a movable eddy current probe that emanates a fluctuating magnetic field and which generates a signal indicative of the magnitude of the interaction between the field and the portable target medium from which the distance between the two may be computed. The system may be used to determine the proximity of non-conductive structures such as plastic pipes that have been buried under ground, as well as the dimensions of such non conductive structures.

Abstract: A concrete or the like mattress for laying over a pipeline on the seabed comprises an elongate recess or tunnel (5) having an insulating material (6) located therein. The mattress is laid over a subsea pipeline so that the pipeline is received within the insulant-containing tunnel. The pipeline is thus physically protected and thermally insulated. The mattress can comprise a plurality of concrete or like members (1,2,2',3,3') articulated together.

Abstract: Pipelines are maintained in subterranean location by a plurality of weighting devices which include an elongate central raised region enclosing the pipeline and generally planar flanges extending outwardly from the central raised region in a common plane. Backfill overlaying the flanges provides an increased resistance to upward movement of the buried pipeline under the influence of an encompassing fluid medium or other force.

Abstract: A groundline stabilizing device for stablizing in-ground pipes in their original in-ground relationship has a spacing bar with clamp members fixed to its ends for receiving the pipes in transverse alignment with respect to the bar, and a plate fixed to the bar in parallel relationship to a plane passing through the bar and the pipes received in the clamps which responds to shifts in the earth to stabilize the position of the pipes relative to the surrounding earth, minimizing radial shifts on one pipe in relation to the other.

Abstract: For gasketing slip joint applications, a method is disclosed for clean pipe laying involving shrink wrapping the bells and spigots of pipes and conduits prior to their installation in the field and circumferentially cutting an aperture in the shrink wrap at the end of the pipe to permit insertion of the end of a mating pipe. The above procedure provides a clean environment so that contaminants do not enter the pipe and eliminates the cleaning step normally necessary when joining or connecting water, sewer, or drainage pipe in an excavated trench. In the case of water, sewer, or drainage pipe, the O-ring seal of the bell is lubricated and then this end of the pipe is shrink wrapped, as is the mating tapered pipe to be inserted into the bell. The shrink wrap prevents contaminants from the excavation or otherwise from entering into either of the pipes to be joined, thereby eliminating joint failure due to contamination during installation as well as pipeline contamination in general.

Abstract: Apparatus for laying pipe in a trench includes a housing with a bottom, side walls, a leading end wall and a trailing end wall, with a tapered nose at the leading end, the nose being designed to be pulled along a trench by a backhoe. The nose is hinged to the leading end wall and can be pivoted up and down when the housing is moved along the trench. The housing includes a trough which receives and orients a pipe and a pusher which moves the pipe along the trough and into assembled relationship with an end of a previously-laid pipe. A hopper near the trailing end of the housing has a chute which deposits fill material around the pipe. The trailing end wall has an opening with a slidable door to strike off the top of the fill material. Mechanism is connected to the trough and door to simultaneously move them up and down to maintain the pipe on grade and to maintain the depth of fill material constant relative to the pipe.

Abstract: A marker tape for location of a buried conduit, having a plurality of electronic markers spaced thereon at predetermined intervals. The distance between the markers encodes information about the buried conduit. The tape may be a nonconductive ribbon or cord, and the markers are preferably passive circuits tuned to a specific frequency. The tape ribbon embodiment may include slots therein for receiving the markers. The markers may be oriented in a predetermined pattern to encode additional information.

Abstract: An external pipe protector for protecting steel or plastic pipe against damage is disclosed. The protector includes a flexible sheet of shock absorbing material which is shaped and sized to encircle at least part of the length of the pipe. Opposite ends of the shock absorbing material are positioned and secured in overlapping relationship to one another by fastening elements provided on the opposite overlapping ends of the shock absorbing material. The fastening elements are confronting adhesive surface attached to the opposite overlapping ends of the shock absorbing material. Strippable covers are initially attached to the adhesive surface prior to use thereof, and are easily removed to enable the adhesive surfaces to be brought into confronting relationship to one another.

Abstract: A method for preventing water leakage into and out from a pipeline utilizes an injection material and a liner. The injection material exhibits fluidity and hardenability. The liner includes an elastically deformable sleeve having an outer diameter smaller than the inner diameter of the pipe and a plurality of elastically deformable and successively circumferentially extending projection portions formed at axial intervals on the circumferential surface of the sleeve; a sheetlike base placed inside the sleeve in a radially expandable, wound cylindrical form; fixing means for maintaining the base in a substantially cylindrical form when the base is radially expanded inside the sleeve; and check valve means defined by the sleeve and the base when the base is radially expanded. The check valve means permits the injection material to flow from the inside of the base into the space between the projection portions in the axial direction.

Abstract: The present invention relates to a method and an arrangement for influencing the interaction between a layer of earth and a structure situated in association with the layer of earth. What is characteristic of the invention is that a casing filled with a medium and introduced into a layer of earth is introduced into a material surrounding the casing, which material preferably consists of a bentonite or a bentonite mixture.

Abstract: A concrete or like articulated mattress for protection of seabed installations comprises a plurality of concrete elements (31, 32, 33, 34, 35) articulated together, the mattress having a relatively thick central block (33) from which its thickness tapers through side blocks (31, 32, 34, 35) to side edges (36, 37). In the central block (33) a tunnel (60) is provided to accomodate a seabed installation such as a pipeline to be protected. Prior to installation on a seabed, the side blocks (31, 32, 34, 35) may be folded over and stored on the top of the central block (33).

Abstract: A magnetically detectable plastic, e.g., polyethylene, polyvinyl, etc., pipe for underground use comprises a hollow tubular plastic pipe having particles of magnetic material embedded in plastic and secured integrally with the wall of the pipe. The magnetic particles are of iron oxide or barium ferrite and of a size, shape, distribution and proportion such that the plastic pipe may be easily detected by magnetic detection apparatus on the surface when the plastic pipe is buried at a selected depth under the ground. The magnetic particles are uniformly distributed throughout the thickness and uniformly distributed around the entire circumference of the plastic pipe or the magnetic particles may be distributed in discrete portions of the plastic pipe, as for example, a uniform outer layer of the pipe or in stripes or strips extending along the pipe.

Abstract: A marked conduit allowing electronic location of the conduit after burial, having a plurality of electronic markers spaced thereon at predetermined intervals. The distance between the markers encodes information about the buried conduit. The markers are preferably passive circuits tuned to a specific frequency. The markers may be oriented in a predetermined pattern to encode additional information, and may be attached to the outer or inner surface of the conduit, or imbedded in the wall of the conduit.

Abstract: A conduit marking device including one or more strips of flexible material coupled adjacent one end to a fastening member configured for coupling to a conduit member. The strips, when coupled to the conduit member, extend in a vertical direction, with the strength and flexibility thereof being sufficient to avoid severing during the screeding process. The length of the strips is sufficient to extend above the surface of the poured concrete floor to provide visual indication of the location of the conduit member after curing of the concrete. The strips may be color coded, or may be provided with indicia, either or both of which may be used to indicate the type of conduit member, as well as the direction, depth or the like.

Abstract: A magnetically detectable plastic, e.g., polyethylene, polyvinyl, etc., pipe for underground use comprises a hollow tubular plastic pipe having particles of magnetic material embedded in plastic and secured integrally with the wall of the pipe. The magnetic particles are of iron oxide or barium ferrite and of a size, shape, distribution and proportion such that the plastic pipe may be easily detected by magnetic detection apparatus on the surface when the plastic pipe is buried at a selected depth under the ground. The magnetic particles are uniformly distributed throughout the thickness and uniformly distributed around the entire circumference of the plastic pipe or the magnetic particles may be distributed in discrete portions of the plastic pipe, as for example, a uniform outer layer of the pipe or in stripes or strips extending along the pipe.

Abstract: A method and apparatus for conducting a survey to determine the location and elevation of a buried pipeline located in a shallow water environment. The method includes determining whether submerged obstacles are located between the ends of that portion of the line being measured and measuring the depth of the line by taking magnetic sounding of the buried line at spaced intervals by crossing the line at longitudinally spaced points with the magnetic survey apparatus. The apparatus includes a towed sled for carrying the magnetic sensing device.

Abstract: A flexible hosing for circulation of a heat transfer fluid to effect heat exchange within a concrete or other type of slab. An inner wall comprising nylon, rayon or other similar material forms an inner wall of the hosing to resist corrosive attack by the heat transfer fluid. A locator wire is embedded within the hosing for transmission of a locating signal so that the position of the hosing within the slab may be accurately determined. The wire may also serve as an electrical resistance heating element should the heat transfer fluid become frozen, or should it be desired that the heat exchange system be operated without an external boiler or other heat source.

Abstract: A marker tape for location of a buried conduit, having a plurality of electronic markers spaced thereon at predetermined intervals. The distance between the markers encodes information about the buried conduit. The tape may be a nonconductive ribbon or cord, and the markers are preferably passive circuits tuned to a specific frequency. The tape ribbon embodiment may include slots therein for receiving the markers. The markers may be oriented in a predetermined pattern to encode additional information.

Abstract: In order to locate, trace, and identify hidden elongated objects, such as buried fiber optic cables, the objects are provided with elongated permanent magnet identifier devices having magnetic fields that may be detected at a distance from the objects. In one embodiment the identifier device comprises an elongated strip magnetized in the direction of its width and formed into a long-pitch helix, producing a characteristic "magnetic field signature" that enhances detection and identification of the object, as by a portable gradiometer that is moved over the surface of the earth along a line generally parallel to the length of the object. This embodiment may provide a magnetic field that diminishes as the square of the distance from the identifier device (rather than the usual cube of the distance), thereby enabling detection at substantial distances.

Abstract: In order to locate, trace, and identify hidden elongated objects, such as buried fiber optic cables, the objects are provided with elongated permanent magnet identifier devices having magnetic fields that may be detected at a distance from the objects. In one embodiment the identifier device comprises an elongated strip magnetized in the direction of its width and formed into a long-pitch helix, producing a characteristic "magnetic field signature" that enhances detection and identification of the object, as by a portable gradiometer that is moved over the surface of the earth along a line generally parallel to the length of the object. This embodiment may provide a magnetic field that diminishes as the square of the distance from the identifier device (rather than the usual cube of the distance), thereby enabling detection at substantial distances.

Abstract: An anti-corrosion sealing assembly for use between a protective casement sleeve and a pipe to be protected is disclosed. The pipe extends through the protective casement sleeve such that an annular casement cavity is formed therebetween. The sealing assembly includes a muff arrangement secured between outer surface portions of the casement sleeve and the pipe at each end of the casement sleeve. More particularly, inner and outer muffs are secured about outer perimeter portions of the pipe and the casement sleeve at each end of the casement sleeve such that the outer muff totally encompasses the inner muff thereby forming a mold cavity therebetween. Each outer muff further includes a pouring spout into which a sealing compound may be poured. Furthermore, an injection tube extends through the inner and outer muffs and opens into the annular casement cavity to permit a corrosion inhibitor to be injected therein.

Abstract: A polymeric tape intended for use underground near service lines with a biocide incorporated into the polymer. The biocide's presence in the tape after burial discourages vegetative, fungal or other biological growth near the tape. Specifically tree root growth destructive to pipes is prevented. The biocide is incorporated into the plastic tape or the plastic coating on the metallic layer of a detectable tape. The biocide is incorporated in an effective amount to have biocidal activity on the surface of the tape or in increased amounts which leach form the tape.

Abstract: The locating of structural members disposed within the interstices of a concrete member can be accomplished by employing at least one indicator capable of showing the position of the structural member. The indicator also can show the directional location of the support members. The indicator of the present invention generally connects to a post member. This post member provides vertical support for the indicator system. A clamping assembly is attached to the post member and connects the structural member to the indicator system for fixing the location of the structural member. The clamping system can also identify the location of the structural member, and the indicator can then be provided to show the directional line of the structural member. Typically, the post member is sized to a predetermined length so that the longitudinal dimension of the indicator system corresponds to the thickness of the concrete member.

Abstract: In a subterranean heat insulated pipe system as laid with angellike bendings between straight pipe lengths, i.e. a district heating pipe underneath a street angle, the conventional bending elements are substituted by pipe elements joined so as to form a bending run of a relatively large bending radius, which, depending of the pipe size, has a minimum value, by which the pipe bending by itself and by interaction with the earth is able to take up the expansion and contraction forces, which are created in the pipe in response to temperature changes therein. The said minimum value has been found to be so low that in many instances it is hereby possible to avoid the sharp bending elements with their associated heavy problems due to expansion effects.

Abstract: For heat insulation of pipeline bundles under water the invention proposes to fill the space between one or more gas or fluid conducting lines and a surrounding carrier pipe with a crude oil fraction, preferably a kerosene fraction, with gelling chemicals, so that the oil is viscosified in the bundle on or near the destined location. The dynamic viscosity after gellation is preferably between 10 and 1.000 Pa.S. The oil is preferably a kerosene fraction. The invention also relates to the way of filling the said space and to means for keeping pressure on the gel by a duct in the carrier pipe, filled with gas and having a pig movable therein and in contact with the gel so that the gas keeps the pig pressed onto the gel.

Abstract: In a pipeline crossing, a carrier pipeline is annularly surrounded by a casing with the ends of the casing vented to the surface and sealed with the periphery of the pipeline to minimize corrosion of the pipeline wall. Access and pressure relief valves are provided on the casing vents at opposite sides of the crossing. This permits purging of the casing injecting an inert gas under pressure into the casing annulus through the valve equipped vents to provide a protective fluid, and periodically monitoring the gas pressure. The gas is maintained at a low pressure which is substantially less than the pressure of product materials within the pipeline.

Abstract: In a pipeline road crossing a pipeline is loosely surrounded by a casing under the roadbed with its ends vented to the atmosphere and sealed with the periphery of the pipeline to minimize oxidation of the pipeline wall within the casing. Access and pressure relief valves are connected with the casing vents at opposite sides of the road. This permits injecting gas under pressure into the casing annulus through the valve equipped vents and periodically monitoring the gas pressure.

Abstract: A process for repairing underground sewer lines by preventing the infiltration of groundwater into a leaking sewer line comprising determining the location of the leakage into the sewer line, vacuum excavating a bore into the ground to the sewer line in the vicinity of the leak, depositing a quantity of a water swellable material such as an argillaceous material selected from the group consisting of bentonite and attapulgite into the bore to a depth of at least about one foot above the sewer line, tamping the argillaceous material in the bore, depositing a quantity of gravel over the argillaceous material in the bore, and backfilling the excavation. The water-swellable material also contains a dye which will infiltrate into the sewer line until the leak is sealed. Through a downstream inspection, the presence or absence of the dye indicates whether water infiltration into the sewer line has stopped.

Abstract: In a method and apparatus for inhibiting ice mass formation around equipment housed in a chamber subject to water penetration, a plurality of compressible, non-absorbent, smooth-surfaced blocks are packed around the equipment to substantially fill the chamber. The blocks are provided with handles for their placement in and removal from the chamber. The blocks are particularly useful for inhibiting ice mass formation in shallow underground chambers housing telecommunications cable equipment.

Abstract: This conduit locator is designed to indicate the location of an end of a conduit after concrete is poured over the conduit. Primarily, it consists of an adhesive tape having a multiple number of spaced rods adhered so as to extend from an edge of the tape, and the tape is adhered to the open end of the conduit which may be plugged or covered with out interfering with the rods extending upward. The rods are of a springy plastic and protrude upward after the concrete is poured over the conduit enabling the end of the conduit to be located beneath the surface of the concrete.

Abstract: A method and apparatus for insulating a pipeline (1) which is more or less submerged in the sea bottom consists in that the insulation (3) is made directly at the pipeline (1): the substances for production of the insulating overing are transported to a mixing chamber (7) at the production site and are foamed around the pipeline (1). For this purpose may be used a flexible sheet (4) of material such as foil which is anchored to the sea bottom (2). Through the production of the insulation (3) in situ, the gas pressure in the insulating material (3) can be adapted to the outer pressure and thereby a compression of the material with loss of insulating effect can be avoided.

Abstract: The apparatus of the instant invention includes a surface traversing mobile frame which, in the preferred embodiment, transports the elements of the invention. Means for dispensing a continuous length of hollow sheath and for dispensing a continuous length of signal-transmitting cable are provided. An assembly table for inserting the cable into the interior of the sheath includes a device for dividing a side of the sheath. Devices for forming a subsurface trench and for training the assembly produced by the assembly are mounted on the frame.The method of the invention includes opening the side of a hollow sheath along its length, and directing a cable into the opening to produce an elongate, continuous assembly of sheath having the cable inside of it. The wall of the plastimer sheath is permitted to assume a non-joined, closed condition along the region previously opened.

Abstract: A buryable warning tape comprises a length of woven polyolefin fabric. Visible indicia are printed on a first face of the fabric in ink which is essentially nondegradable during burial, typically an ink with a carbon-based pigment. A transparent polyolefin coating is bonded to and covers the first face. Preferably a second polyolefin coating is bonded to and covers the side of the fabric which is opposed to the first face. Such warning tape can have greatly increased tensile strength and tear strength over the warning tapes of the prior art, and the indicia have significantly improved durability.

Abstract: Providing circumferential grooves in bracelet-type anodes on a pipeline provides for preservation of anode effectiveness during bending of the pipeline, such as in reeling operations.

Abstract: A leachate and pollutant drainage barrier system is formed by excavating a narrow slit or slot in the earth in the presence of a reversable slurry mud which changes from a highly viscous character after a predetermined period of time (approximately 5-7 days) needed to maintain the trench open to permit the laying of a drainage pipe at the bottom of the trench and the filling of the trench with a pervious fill, such as gravel, etc. After the fill has been installed, lateral support for the earth walls is provided by the pervious fill material and the slurry reverts to a liquid having a substantially lower viscosity which may be drained via the drain pipe in the bottom of the trench. In a preferred embodiment the slurry is a biodegradable polymer. In addition, a plastic film or layer can be installed in the trench.

Abstract: A pipe supporting dam assembly and method for pipeline construction employing a planar dam sheet with a collar and a flexible sleeve for receiving and supporting the pipe, and clamping means to seal the collar to the outside of the pipe to prevent fill material in the trench being washed away by groundwater along the outside surface of the pipe, particularly in the case of sloping pipeline construction.

Abstract: Deep sea shark cable protectors of the invention are lengths of pipe which encircle the cable, having a plurality of spaced apart spikes extending outwardly around the circumference of the pipe to prevent the shark from gripping the cable in its mouth. The lengths of pipe are hinged and have closures for securing the pipe sections, and the pipe lengths may be made of brass or other materials. The spikes may extend from around the outer surface of the pipe or may extend from the outer perimeter of clamps which encircle the cable or which encircle and/or join pipe sections.

Abstract: In a trench is disposed a closed flexible envelope filled with a fluid having a density or pressure greater than that of the surrounding fluid, movable by itself under the effect of the pressure exerted at its end by said pipe, which envelope is in the form of a cylinder each end of which has been turned in concentrically to its longitudinal axis, in the direction of the opposite end, the two central portions of this turning in being welded together so as to form a central envelope web turned in along its axis.

Abstract: A culvert having a corrosion resistant composite coating and a method of producing the corrosion resistant composite coating. The coating method is for use in a coventional hot dip coating line of the type wherein a steel strip, having been appropriately pretreated so as to be at or above the coating temperature and have its surface free of oxides, is caused to pass through a bath of molten coating metal. A fibrous aramid paper is bonded to the surface of the steel strip by pressing the fibers into the molten coating layer immediately after the steel strip exits the coating bath. The steel strip may be fabricated into construction products such as culvert which may be further protected with bituminous type coatings.

Abstract: A flexible hose suitable for use in seawater contains a small amount of copper dust in its elastomeric cover. The copper dust, even though present in a small amount, inhibits marine growth on the hose and prevents marine creatures boring very far into the hose. The hose is particularly suitable for the transportation of corrosive fluid such as crude oil.

Abstract: A detectable tape including a ductile metal foil layer which is enclosed in a sheath of thermoplastic coating which provides a sealed edge along the length of the tape. The thermoplastic coating sheath protects the foil from corrosion when the detectable tape is placed underground above a nonmetallic body such as plastic pipe. The sealed edge detectable tape can also include a reinforcement layer which provides additional tensile strength.

Abstract: A marking tape that is positioned underground above utility lines wherein the marking tape carries a pair of closely spaced, parallel, insulated conductors that extend the length of the tape and at least one other insulated conductor extending the length of the tape which is separated from the pair of conductors at a distance that is greater than the distance between the conductors of the pair of conductors. Passive markers having a resonant circuit can be selectively placed along the tape wherein the resonant circuit is electromagnetically coupled to the pair of conductors and the other conductor. The other insulated conductor can be one of a pair of conductors similar to the other pair of conductors. A method is disclosed whereby the making tape can be electromagnetically traced with the position of the passive markers established. A method is also disclosed for determining the distance to a break in the tape which causes the pair of conductors to be severed.

Abstract: A reinforced metallic and polymer tape which has a light reflecting metallic layer and can have a color coating. The reinforcing material is usually a nonwoven clear resin through which the color is clearly visible. The combination of the metallic layer and reinforcing layer produces a high tensile strength, tear resistant tape. The combination also produces a tape that does not have the tendency to curl.

Abstract: A method for installing a pipeline for transporting a warm fluid, such as newly-produced oil, across arctic seafloor underlain by a permafrost zone without danger of rupture of the pipeline caused by thawing in the supporting permafrost zone comprises (1) drilling a series of boreholes along the seafloor through a thawed zone of subsea soil so as to penetrate a distance into a zone of permafrost lying thereunder, (2) circulating a warm fluid through each borehole so as to cause a zone of prethawing in the permafrost zone and thereby create a slump trough on the surface of the seafloor along a path marked by the series of boreholes; and (3) installing a warm fluid bearing pipeline along the bottom of the slump trough. Usually a temperature differential between the warm fluid and the bottom of the borehole of at least 2 degrees Fahrenheit is required to assure economical prethawing of the permafrost zone.

Abstract: A pipeline or other subterranean structure is protected by burying above it a signaling material in the form of a continuous support of a material having low resistance to rupture by carrying at least one row of spaced apart strip sections of a high resistance to rupture. Because the strip sections form a discontinuous band, when encountered by the excavator, the support ruptures and the strip sections can only be pulled and remain unsevered so that free ends of the sections are readily visible to the excavator operator.