NICHU-T-87 003 C3
Loi'!N !.r !PY O!,.l y
DIQER EDUCATION SERIES
Tethered Scuba Diu»g
l.ee H. Soakers
Michigan Sea Grant College Program
MiCHU-SG-87-503 DIVER EDUCATION SERiES
Tethered Scuba Diving
lee H. Somers
Michigan Sea Grant Coilege Program
MICHU-SG-87-503 Nichigan Sea Grant is a cooperative program of The University of Nichigan and Nichigan State University. It is part of a national network of Sea Grant programs of fering marine and Great Lakes research, education> and extension services. In addition to diving and water safety programs< Michigan Sea Grant conducts research' produces publications, and provides extension assistance on shoreline erosion> waterfront development, commercial and sport fisheries> toxic substances> and marine transportation and engineering. Contact the address on the last page for a publications catalog or other information.
Lee 8. Soeers is an Associate Research Scientist+ Department of Atmospheric and Oceanic Science; Assistant Professor, Division of Physical Education; and Diving Safety Coordinator> Department of Occupational Safety and Environmental Healthy The University of Nichigan. He is also Nichigan Sea Grant's Ex tension Specialist in diver education< diving technology< and aquatic accident management. Dr. Somers' 30-year diving career has included commercial< research, search and rescue~ saturation, polar, cave and ocean diving, and directorship of a hyperbaric chamber facility. He holds recreational diving instructor certifications from the National Association of Underwater Instructors and Professional Association of Diving Instructors.
This publication is the result of work sponsored by the Michigan Sea Grant College Program with grant NA85AA-D-SG045 from the National Sea Grant College Program, National Oceanic and Atmospheric Administration NOAA! r U.S. Department of Commercer and funds from the State of Michigan. Price $2.25 TABLE OF CONTENTS
I NTRODUCTION ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ e e ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ e ~ e e e ~ ~ e ~ ~ e e e ~ ~ ~ ~
P ERSONNEL ~ ~ ~ ~ ~ ~ se ~ ~ ~ ~ ~ ~ e ~ ~ ~ ~ ~ ~ ~ ~ e ~ ~ ~ ~ ~ ~ ~ eess ~ ~ ~ ~ ~ ~ ~ ~ es ~ ~ ~ ~ ~
Instructor of Tethered Scuba Diving Trainee Qualif ications Tender 45 45 Diving Supervisor Stand-by Diver Other Personnel 6 6 Dive Team
E QUIPNENT s e s ~ s ~ ~ ~ ~ s s s ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ e e ~ e ~ ~ ~ ~ ~ e e e e e e s s ~ ~ ~ ~ e e e
Nask ~ e ~ ~ ~ ~ ~ e ~ e ~ ~ ~ ~ ~ ~ ~ ~ ~ e ~ ~ ~ ~ ~ ~ ~ ~ ~ s ~ ~ ~ ~ ~ ~ ~ esses ~ ~ ~ ~ e ~ ~ ~ 7 T ether Commun1ca talons Un] t ~ ~ ~ s e ~ ~ ~ ~ ~ ~ ~ s ~ ~ ~ ~ ~ ~ ~ ~ ~ e 8 9 Emergency Self-Contained Air Supply Options 10 Safety Harness/Tether Attachment 12 Standard Scuba Equipment 12
TETHERED SCUBA DIVING PROCEDURES AND TECHNIQUES 12
Preliminary Dive Planning 13 Survey of Nission or Task 14 Evaluation of Environmental Conditions 14 Selection of Diving Techniques s ~ e ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 16 Selection of Divers/Support Personnel a nd Assignment of Task 18 Selection of Equipment 18 Fulfillment of Safety Precautions 18 Establish Procedures and Brief Personne 1 s ~ s ~ ~ ~ ~ ~ ~ e e e e ~ 19 Diving Vessels ... e ~~ ~~ ~~ ~~ ~~ ~ ' ~~ ~~ ~ 19 Assemble Equipment 21 Diver Dressing Procedures 21 The Delve ~ ~ ~ ~ ~ ~ ~ ~ ~ e ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ i ~ ~ ~ ~ ~ ~ 22 Tending the Diver 24 AsCent ~ e ~ ~ ~ ~ e ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 27 Post-Dive Procedures 27
UNDERWATER ENERGENCY PROCEDURES ...... ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 29
Loss of Primary Air Supply 29 Flooded Full-Face Nask 31 Entanglement ~ s ~ ~ ~ ~ ~ e e e e e e ~ ~ ~ 32 Loss of Communications 33
S UNWARY ~ ~ ~ s e s s ~ ~ e ~ ~ ~ e e s ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ e e ~ ~ s ~ ~ ~ ~ e ~ ~ e ~ ~ ~ ~ ~ 33
REFERENCES APPENDIX I: Tethered Scuba Diving Training Program ...... 35
APPENDIX II: Estimating Diver Air Consumption & Available Ai r Supply ...... 37
APPENDIX III: Tethered Scuba Diving Equipment List ...... 39 DIVER EDUCATION SERIES
TETHERED SCUBA DIVING
Lee H. Somers, PhD
INTRODUCTION
Swimming and working underwater using self-contained underwater breathing apparatus scuba! is a standard practice in military< scientific< and recreational diving. Accepted safety procedures for scuba diving operations generally require deployment of divers in pairs i.e., use of the buddy system!. On the other hand, commercial divers more commonly use surface- supplied or umbilical! di ving equipment and procedures. This mode of diving usually implies deployment of a single diver to accomplish the underwater task. The diver is supported by a tender on the surface or in a diving bell.
A less commonly used mode of diving is tethered scuba diving. This generally involves the deployment of a single scuba diver who is tended from the surface by means of a safety line or tether. Safety and operational requirements for this mode of diving are addressed in the U. S. Navy Diving Nanual and in the U. S. Depar tment of Labor Occupational Heal th and Sa fety Administration! and U. S. Coast Guard requirements for commercial diving operations , 3, 43.
Tethered scuba diving is probably one of the most under- rated and misunderstood of all diving modes. The procedures and equipment used for tethered scuba diving by some commercial divers are considered to be haphazard by many diving safety authorities. Search and rescue teams commonly use a single line tended mode of scuba diving Ll]. However, very few dive teams actual ly use the equipment and procedures that are described in this publication. Tradition, lack of state-of-the-art equipment, inadequate training, economic constraints> and narrowly-scoped recreational diving influences have compromised advancements and, in some respects, safety in search/rescue and scientific diving.
Tethered diving has never been officially accepted by the recreational diving community in the United States. Furthermore, only a limited number of scientific divers currently use tethered scuba techniques, probably because most scientists have been trained by recreational diving instructors. Critics of tethered scuba diving include the following concerns:
* Scuba diving without a buddy is unsafe;
* The diver could be at high risk if the safety line or te ther became en tang 1 ed; * The diver would not have the assistance of a buddy in the event of air supply failure or depletion; and
* The diver would surely drown in the event of loss of consciousness.
On the other hand> advocates of tethered scuba diving consider the following factors in support of the practice:
* Tethered scuba div ing may only be used for selected underwater activities< not as a complete substitute for all conventional scuba diving or surface-supplied diving;
The tethered scuba diver is not diving alone since the surface tender, in realityr functions as a buddy;
* modern diving practices include the use of voice communications between the diver and tender, thus providing a means of constantly monitoring the diver's status;
Use of a single tethered scuba diver is probably a safer practice for diving in very limited visibility water than free swimming scuba diving where buddy separation is more probable and underwater emergency assistance requi rements such as sharing air are extremely dif ficult at best> if not impossib le;
Loss of air supply or primary regulator malfunction emergencies can easily be resolved by using scuba fitted with dual regulators or a compact secondary scuba; and
If a diver loses consciousness underwater, the full face mask would prevent immediate drowning and loss of communications/line response would prompt the tender to immediately recover the diver and/or deploy a stand-by diver.
The equipment and procedures for present day tethered scuba diving presented in this publication are significantly different from those used in past years. Commonly< tethered scuba diving has implied attaching a rope to a solo diver using a conventional mouthpiece-style scuba regulator. There was no full-face mask security, no emergency air supply alternatives, no communications except line-pull signals!, and, generally, no specific training.
The fol lowing conditions and limitations are recommended for modern te thered scuba di v ing opera t ions: Depthisgenerally limited to 60 ft. except in standby diver deployment emergency!;
Communications/streng th member tether must be secured to the diver's scuba or safety harness;
A full-face mask must be used;
* An emergency or secondary air supply and/or regulator system must be used; and
* The diver must surface when cylinder pressure is reduced to no less than 500 psi 00 psi for twin cylinder scuba!.
Although tethered scuba diving is not considered as acceptable as surface-supplied diving by most researchers and commercial divers, it has proven satisfactory and safe for selected diving operations and stand-by diver application. It has been especially useful for very limited to zero visibility shallow water research where the dive team does not have a surface-supplied system available. Under such conditions the presence of a second diver is of little or no safety benefit and may even constitute additional risk.
Tethered scuba diving has also been effectively used for extremely cold weather diving from smal 1, open boats where the deployment of two divers would have greatly complicated logistics and increased the surface exposure time. This mode has been successfully used for under ice diving.
This publication has been prepared to serve as an inforaational document for individuals/groups who are considering the use of tethered scuba diving in scientific, rescue< and commercial diving. Qualified instructors may use it as an instructional aanual for training tethered scuba divers. For economic reasons illustrations have been excluded from this printing. The instructor must support the written information with appropriate visual aids and actual tethered scuba diving equipment. A sample course is included in Appendix I.
PERSONNEL
Any competent scuba diver can be trained in tethered scuba diving techniques. Establishment of an acceptable training and operational tethered scuba diving program simply requires some special equipment in addition to conventional scuba diving equipment!, a slight modification of scuba diving philosophy, and a respect for both the advantages and limitations of this mode of diving. Furthermore, most competent scuba diving instructors can develop the knowledge and skill to teach tethered scuba. Since tethered scuba diving is more likely to be applied in working operations such as search/rescue and scientific research< the instructor should have a thorough understanding of the type of diving operations for which the diver is being trained.
Instructor of Tethered Scuba Diving
At present there is no recognized instructor or diver certification for tethered scuba diving. Tethered scuba diving training programs will have to be developed and conducted by competent scuba diving instructors with a knowledge of the type s! of diving for which the student is being trained. For scientific diving programs the instructor must be certified to teach scuba diving and authorized by the sponsoring organization's Diving Contxol Board.
The instructor will have to acquire specific knowledge in the design, use~ and maintenance of full-face masks< communications systems, tethers, and other support equipment through personal research/study, manufacturer sponsored training programs> and/or special tethered scuba diving workshops. As national interest in the application of tethered scuba diving develops, instructor training programs may also develop. To this author's knowledge, the only national ly recognized training organization providing instruction in modern tethered scuba diving techniques is Dive Rescue International of Ft. Collins, Colorado. Natural ly< some U. S. Navy and commercial diving schools also include this in their programs.
Trainee Qualifications
Candidates for tethered scuba diving training should be certif ied/authorized, competent scuba divers. Ideal 1yr the scuba diving training/authorization should be in accord with the standards of the American Academy of Underwater Sciences AAUS!, especially for scientific diving programs. Organizations adhering to the standards of the AAUS requalify their divers on an annual basis. Consequently, the trainees from these organizations already have a current medical examination on file, a record of at least 12 dives in the previous year> current CPR certificationr and diving authorization/approval from a Diving Con tro 1 Boa rd.
The trained scuba diver wi 1 1 have to make some adjustments in diving philosophy and technique in addition to learning to use new items of equipment. The di ver wil 1 have to adjust to working alone underwater and recognizing emotional and physical security in the tender above and special equipment. Consequently, competence and experience in scuba diving cannot be over emphasized. The instructor may require the candidate to complete a scuba skil 1 evaluation conf ined/open water! and knowledge examination as a pre-requisite for tethered scuba diving training, especially for individuals who have not been annually authorized in accord with AAUS standards.
A novice scuba diver can be easily trained in tethered scuba diving. However> competence develops with experience. The emotional adjustment to self-sufficient diving will probably be easier for an experienced diver. Ideal ly, a diver should have documentation of at least 30 open water scuba dives prior to acceptance into a tethered scuba diving program.
Tender
A tender is a member of the dive team who assists the diver in dressing, donning scuba, pre-dive equipment inspectionf deployment/retrieval, and post-dive activities. While the diver is under water the tender constantly tends the dive's tether to eliminate excess slack or tension. In the event of communications unit malfunction> the tender must exchange line pull signals with the diver> keep the diving supervisor informed of the diver's status, and remain alert for any signs of an emergency.
With few exceptions, the tender should also be a qualified tethered scuba diver. This insures that the tender will have a complete knowledge of all equipment and procedures. In addition, operational efficiency is highest if all members of the team can be included in a diver rotation plan. When circumstances require the use of a non-diver as a tender, it is the responsibility of the diving supervisor to assure that that individual is properly instructed in tender duties. Ideally, non-diver tenders should complete the same training course as tethered scuba divers except for in-water activities! plus be completely familiar with scuba and scuba diving procedures. They must also be trained in general and diving-related first aid and currently certified in CPR. It is evident that one cannot simply hand the tether to a bystander and say "Wil 1 you tend the diver today'P"
Diving Supervisor
The diving super v isor de signa ted person-in-charge or divemaster! is the person in immediate charge of the diving operation. He/she is general ly a highly experienced tethered scuba diver or former tethered scuba diver designated by the Diving Control Board or selected by diver team agreement. The diving supervisor has complete authority and foll responsibility for the diving operation. All dive team members are in turn responsible to the diving supervisor for carrying out their assigned task according to the operational plan and briefing and must adhere to specified safety requirements.
On major diving operations the diving supervisor wil 1 generally not function in the role of a diver. He/she will occupy a position at the diving station in order to control/ monitor the activities of all team members and to bp in a position to direct surface personnel and the standby diver in an emergency. On sma 1 1 di ve teams> the di v ing super v isor o f ten accepts the role of communicator and timekeeper/recordkeeper. Smal 1 dive teams often lack suf f icient personnel to al low for designation of a supervisor who will not participate as a diver. General ly, the most experienced and highly qualified individua 1 wi1 1 be in charge of the operation. However, since that person must be included in the diver rotation, the person serving as tender at any given time in the operation assumes diving supervisor responsibilities.
Stand-by Diver A stand-by diver is required for all tethered scuba diving operations. The diver must be fully qualified and equipped to enter the water in response to an emergency at any time. The diver shal l be appropriately dressed and have equipment assembled so that he/she can don al 1 equipment and be deployed within one ainute. This means that each tethered scuba diving team must have two coeplete tethered scuba outfits. Ideal ly, a second tender is also available to serve the stand-by diver.
The stand-by diver is deployed at the discretion of the diving supervisor. The stand-by diver functions in a lifeguard capacity ready to render aid to a distressed diver on the surface as well as under water. The stand-by diver is positioned at the diving station where he/she can observe the entire operational area and quickly deploy.
Other Personnel
Some larger dive teams wi1 l designate diver aides> an emergency medical person> and a timekeeper/recordkeeper. Zn addition, a boat operator or crew many also be present. The diving supervisor must assure that all persons invol ved ia the diving operation are qualified for their specific roles. He/she must also exercise his/her authority to control the diving station and all personnel in the vicinity in order to assure that team members are not distracted from properly performing their duties. Bystanders should be excluded from the dive station, if at all possible.
Di ve Teaja
The minimum tethered scuba dive team should consist of no less than three persons -- a tender/supervisor, a diver, and a stand-by diver. These individuals can develop an efficient diver rotation plan and work safely and comfortably from a small vessel. An additional qualified individual to serve as stand-by diver tenderI recordkeeper/timekeeper> and general diver aide is hig h 1 y recommended. EQU I P HEl4T
In addition Co standard scuba diving equipment and thermal protection, the following items shal 1 be included in a tethered scuba di v ing ki t:
Demand breathing mask with communications;
Twin 72, 80> or 100 cubic foot scuba unit with dual regulator manifold or a seperate 15 to 40 cu. f t. emergency scuba commonly cal led a pony cylinder in scuba diving! [single cylinder scuba may be used for short and/or shallow dives provided that a dual valving system with two regulatoes or an emergency scuba is included in the system];
An over-pressure relief valve must be used on any first stage regulator without a down-stream second stage;
Submersible pressure gauge on primacy regulator;
Communica tions/streng th membee te thee; and
Surface communications unit.
Mask
From a safety and communications standpointr it is necessary to use a ful 1-face diver's mask rather than a conventional mouthpiece-style scuba regulator. First> proper communications is very difficult with a mouthpiece-style regulator. Second< in the event that the di ver is injueed or loses consciousness, the mouthpiece-style regulator could easily be dislodged and lost. With a full-face mask, even if the diver is unconscious he/she could continue to rece i ve ai r.
Based on personal peeference, a diver or diving group may select one of several conventional surface-supplied "demand breathing" masks i.e., Heliox-18' KNB 10, DN 5 or equivalent! which have been standard equipment in scientific, commercial and military diving for more than a decade or a lightweight demand beeathing mask i.e., AGAi Widol f, DSZ EXO-26' or equivalent!.
The popular commercial and military divers' masks are built around a molded fiberglass or plastic frame upon which is mounted a rubber face seal/hood, a head harness, a face plate 1 ens made of high impact aceyl ic plastic, a side block ai r control assembly> a demand eegulatoe, an interior oral/nasal mask, a moveable nose pad to aid in ear/sinus pressuee equalization!, and speaker/earphone components. The demand breathing system is basical ly the same as that used in an adjustable scuba regulator second stage. The side block assembly is designed to accept an emergency or secondary air supply hose. A separate padded head proCector may be used if desired.
Although the diver will general ly use the demand breaChing mode, a valve on the side block assembly Heliox-18, KNB-10, etc.! al Laws for activation of free-flow air for clearing condensation fcom the face plate or for increased respiratory cequi rements associated with heavy work. In addition, another val ve on the side block assembly enables the diver Co acti vate air supply from an auxi 1 lacy ficst stage regulator oc separate compact scuba in the event that the primary supply ma 1 functions.
Many tethered scuba divers prefer to use a lighter weight, lower internal volume demand breathing full-face mask rather than the heavier, more complex commercial/military masks. These masks are constructed with either soft rubber full-face assembly or a solid support frame with a rubber face seal and are fitted with a high impact polycarbonate plastic wide-view faceplate. A largei flexible nose pocket facilitates pressure equaliztion in the ears. The mask is secured to the diver's face using a head ha mess or spider! assembly. A demand regulator is fitted to the front of the mask. Lightweight masks do not generally include the special side block assembly for attachment of a secondary air supply as described above. Communications components are fitted inside the mask with an earphone positioned in a pocket in the face seal or on a head strap An oral-nasal mask minimizes dead air space. The lightweight masks are generally less expensive than the conventional commercial surface-supplied divers' mask and scuba divers f ind them to be more corn f or tab le.
Since most scuba di ving instructors are not faai 1 iar wi th full-face aask design, function, and aaintenance, and standard scuba diving training manuals do not address these masks, tethered scuba diving instructors, divers< and trainees should be provided with a copy of the manufacturer's operations and eaintenance aanuai for the particular sask being used in training or operational diving.
Tether
The coaaunications cable commonly used in commercial surface-supplied diving is a thermoplastic coated, 4-conductor cable with a steel braid internal shielding. This cable is commonly termed "s pi ra 1-4 communication wire" in the commerc ia 1 diving industry. It has a tensile strength of about 1500 lbs. and is relatively inexpensive. Normal ly< only two of the four conductors are used at a time. The spares remain available in the event that one of the wires breaks or shorts during use. This increases the useful lifetime of the cable. The diver's end of the cable may be fitted with special underwater connectors compatible with the connector available on the mask or simply fastened directly to the mask/helmet post-type connectors. In this case< the wire ends are general ly prepared with solder for added strength and ease of connection. The surface end of the cable is fitted with a connector that is compatible with the communicator.
Some tethered scuba divees improve the strength and handling characteristic of this cable by threading it through the hol low core of a braided polylefin rope. In factr standard heavy-duty shield two, three, or four conductoe neoprene jacketed electrical cable may also be used in this fashion to construct a combination communications/strength tether. This makes an excel lent assembly; howeveeI caee must be taken in selecting the proper rope size for a given cable size.
An excel lent combination safety/communications 1 ine constructed of 7 mm nylon static kermantle rope with a tensile strength of 3000 lbs. is now available Dive Rescue Interna tional, Ft. Col 1 ins, Colorado!. The communications wi res are woven into the rope. This rope has the strength and handling characteristics of ordinary safety rope. Tying knots in the rope apparently has no adverse effects on the communications wires. Quick-connect electrical connectors are fi tted to each end and special adaptors are available. This special rope may be coiled oe conveniently stoeed in and dispersed from rope bags.
The diver's end of the umbilical assembly is fitted with a large stainless steel snap shackle or caribiner facilitate attachment to the diver's safety harness. This system allows any stress, on the tether to be transfeeeed to the diver' s harness. The shackle is secured to the tether with an appropria te knot or a clamp that a 1 lows most of the stress to be transferred to the strength member. A D-ring is secured to the sueface end of the assembly so that it may be secured at the diving station. This reduces the possibility of the tender and communicator being pul led overboard in the event of underwa tee stress.
The tether is maeked at 10-foot intervals starting at the diver's end using brightly colored tape or other appropriate marking system. This enables the tender to determine exactly how much te ther has been deployed.
Communications Unit
A standard compact push-to-talk divee communicator is used foe tetheeed scuba diving. Two wiees from the communicator are connec ted to the microphone /earphones in the di vee's mask. This enables the diver to communicate dieectly with surface peesonnel at al l times; the surface person must activate a push-to-talk switch in order to talk to the diver.
The communicator is powered by expendable or rechargeable batteries. Most compact communications units are of the "push- to-talk" type. The tender general ly wears the communicator on a belt or neck strap. A combination earphone/microphone headset is plugged into the communications box. This enables the tender to satisfactorily communicate with the diver in areas of high ambient noise levels and requires less power usage than loudspeaker systems. The tender can adjust both diver and tender volume. Some models are fitted with a tape recorder connection. Generally> any surface-supplied diver communicator may be used with a tethered scuba system: however, compact models are more convenient.
The large surface-supplied diver communications units include connections for two or more divers. This al lows for the same communicator to service both the primary and stand-by diver. The divers can actual ly speak to each other; ho~ever, in a two wire system a surface person must control the entire conversation by activeating the appropriate switches. A common talk or round robin system may be used to prov ide al 1 parties with simultaneously open line communications, as in telephone conference cal lsI without operating any controls. This system involves special wiring of the mask earphones and microphone and the use of a four conductor wire to the surface. Consult the communications unit manufacturer's manual for additional information and wiring instructions. As in the case of ful 1-face mask, most scuba di ving instructors and scuba divers are also unfamiliar with wire-type communica tions uni ts. I t is highly recoaweended tha t a 1 l personnel involved arith training or divinq operations be issued a copy of the manufacturer's instructional aanual for the particular unit being used in a given program.
Eaergency Self-Contained Air Supply Options The tethered scuba diver has several independent options for resolving an air supply depletion or regulator malfunction. The diver may activate a second or back-up regulator> switch to a secondary independent scuba< or make a control led emergency swimming ascent. Al 1 options have both advantages and di sadvan tages.
Keep in mind that the possibility of air supply depletion or regulator mal function should be absolutely minimal if equipment is properly maintained and the diver properly monitors his/her air supply pressure gauge. Naturally, the primary regulator must be fitted with a submersible pressure gauge to facilitate convenient air monitoring throughout the diving operation. Unlike surface-supplied diving, the diver is solely responsible for monitoring remaining air supply. However, as in scuba divingi the diver must be trained and prepared to resolve such an emergency.
Secondary First Stage Systems. I f the air supply from the primary first stage regulator is interrupted due to malfunction, the diver may activate the secondary or emergency air supply by
10 turning a valve located on the separate manifold block attached to the scuba harness lightweight diving mask! oe on the right side of a commercial diver's mask Hel iox L8< KAB-LO, oe equivalent!. standaed single-hose regulator first stage is connected to the side block assembly.
Keep in mind that this secondaey first stage eegulatoe hose leads to a closed valve during normal operation> not to a down- stream or fail safe! second stage regulator as in conventional scuba. In the event of a first stage over-pressure mal function in the secondary regulator> the complete cylinder pressure could be released into the low pressure hose causing a rupture and subsequent loss of air supply. Consequently, this regulator must be fitted with an over-pressure relief valve.
frost scuba di v ing instructors and scuba di vers are unfaailiar with these safety relief valves that Ilust be installed in a low pressure port on the regulator first stage. Consult full-face mask eanufacturers and coeeercial diving equipaent suppliers for acquistion of these special valves.
Host lightweight ful 1-face masks are not fitted with a side block manifold designed to accept a secondary aie supply fitting. In this caseI the tethered scuba diver may use an emergency air supply manifold assembly simi liar to those used to peovide emergency air supply to free flow air helmet divers. Hoses from two first regulators are attached to the manifold assembly which may be mounted on the scuba harness!. The air supply from the secondary regulator is secured by closing a valve on the assembly: the primary ai r supply passes through the assembly into a hase attached to the diver's second stage regulator. Zn the event of a primary first stage malfunction involving inteeeuption of air flow> the emergency air supply is activated by turning on the va 1 ve.
The secondary first stage is attached to one outlet on a single or twin cylinder scuba dual regulator outlet manifold assembly i e> Sherwood slingshot valve or dual outlet valves! or to a separate scuba cylinder i e.< l5 or 40 cu. ft. cylinder with standard valve!. Nanys diver prefer to use a separate scuba cyLinder rather than a dual regulator manifold assembly. In the event of primacy aie supply depletion, the diver has an emergency a ir supp 1 y.
Separated or Eeergency Scuba. Same tethered scuba divers use a separate emergency 15 or 40 cubic foot scuba or pony cylinder! with a conventional mouthpiece-style regulator and carry a compact scuba diver's mask in their BC pocket or in a special pocket attached to the scuba harness or emergency regulator hose. In the event of a aie supply loss from the primary system, the diver removes the ful 1-face mask, switches to the secondary scuba regulator, dons the mask, and surfaces.
This technique was successful ly used in the early years of
11 lightweight hei~et commercial diving. Natural ly, if this technique is to be employed, it must be taught and practiced in the training program. Somesurface-supplied divers fear that the scuba regulator may develop an undetected free-flow during the dive and deplete the emergencyair supply. A smal1 bal l-valve may be fit ted at the second-stage end of the low pressure hose. The scuba cylinder valve remains open during the dive and the baLl-valve is turned to activate the supply to the diver. If this special modification is used> the first stage of the regulator must be fitted with an over-pressure relief vaLve.
Safety Harness/Tether Attachaant The scuba backpack and harness assembly may also serve as the diver's safety harness. This harness is equipped with D- rings for attachment of the diver's umbilical assembly and is designed to withstand a minimumof l000 1 bs. pul l in any direction. Keepin mindthat the scubaharness must be securely attached to the diver. Zn the event of an emergency, stress placed on the harness by the tender could pull the scuba from the diver. Thus> although use of the scuba backpack and harness assembly far a safety harness appears to be a standard practice> many divers do question the safety of this method. For this reason, many tethered scuba divers prefer to use a separate body harness or safety belt worn under the scuba harness for attachment of the tether. The safety harness is secured with an non-quick release fastener.
Standard Scuba Diving Bquipeent Each diver will wear appropriate thermal protection garmentsi a buoyancy compensator with power inflator< fins' weight belt, a sharp knife, watch/time for timing ascent rate! and depth gauge consistent with accepted practices in conventional scuba di ving. Decompression tables may be considered optional since the supervisor/tender will monitor the dive time and inform the diver of his/her status. However, some tethered scuba divers prefer to use decompressionmicroprocessors to monitor their dive status. General ly, each diver on a team is required to provide his/her personal diving outfit excluding full-face mask, special scuba, tether> and communicator!. Depending on the dive depth, duration, and activity the diver mayuse standard single or twin cylinders taking into consideration the valving requirements discussed above for emergency or back-up air supply.
TETHEREDSCUBA DIVING PROCEDURESAND TECHNIQUES Careful and detailed planning and preparation is the key to diving safety. Thepre-dive activities involve all personnel and
l2 include the inspection and assembly of equipment, activation of air supply systems, and dressing the divers. This is, of course, in addition to survey of the task; evaluation of environmental conditions; selection of techniques, equipment, and divers; fulfillment of safety precautions; establishment of specific procedures; and personnel brief ing.
Dive planning and procedures is a topic that of ten receives 1imited attention in recreational scuba diving manuals and training programs. Since tethered scuba diving wil 1 probably most often be used by working scientists and rescue personnel who have received their initial scuba diving training in recreational or iented training programs, this topic wil 1 be covered in more detail in this publication. Working tethered scuba diving operations must be conducted at the highest possible level of efficiency and safety. it is necessary that all personnel have a knowledge o f' s ta nda rd opera t iona 1 procedures. The basic procedures gi ven in th is manua 1 are modi f ied f rom those used in commercial diving< rescue diving> and U.S. Navy surface-supplied diving for compatibility with research and other non-military tethered scuba diving operations [3j.
Preliainary Dive Planninq
Preliminary planning is vital for the success of any diving operation. Without adequate preparation, the entire diving operation may fail; and> even more seriouslyi the safety and well-being of the divers may be jeopardized. The diver must be placed in the water under optimum conditions, including suf f icient knowledge> trai ning, experience> equipment and safety. Surface support must be capable and wel l-organized. Although the diving supervisor is responsible for preliminary planning and organization> the entire dive team and ship's crew must render al 1 possible assistance.
The preliminary planning phase of a di ving operation is di v ided into the fo 1 1 owing s teps:
Survey of mission or task.
Evaluation of env i ronmenta1 conditions.
Selection of diving techniques.
Selection of divers and support personnel and assignment of tasks.
Selection of equipment.
Fulfillment of safety precautions.
Establishment of procedures and briefing of personnel.
13 Survey of Mission or Task The first step in planning a diving operation is to assess the mission or task and to formulate a general approach. It should be determined if the underwater task is feasible and if the proper equipment and personnel are available to undertake the task. All factors that might constitute a specific hazard should be noted.
Evaluation of EnvironIIental Conditions Diver safety is influenced considerably by environmental conditions. Careful consideration must be given to both surface and underwater conditions and appropriate arrangements made for diving under these conditions. Surface conditions to be considered include sea state> weather present and predicted!, tides> currents, ship traf fic> etc. Underwater conditions include depth, bottom type or condition, visibility, and tempera ture.
Weather conditions wi1 1 general ly be the first factor to consider in planning a dive. When possible> diving operations should be cancelled or delayed during bad weather. Generally, rough seas can be expected during storms and high winds. Weather forecasts must be reviewed to determine if proper weather conditions will last for a sufficient amount of time to complete the mi ssion. Cri tica 1 wea ther changes and a wind shi f t can jeopardize safety of personnel and vessels. Conditions must be such that adequate mooring may be maintained for the duration of the opera t ion. Do not attempt tethered scuba diving in rough seas Sea State 4: 5- to 8-ft waves!, and when possible> avoid or limi t d i v ing in moderate seas Sea S ta te 3: 3- to 5- f t waves!. Naturally, sea-state limitations will be dependent to a large degree on the type and size of diving vessel. Diving operations may be conducted in rougher seas from properly moored, larger vessels or fixed structures.
Current or tidal conditions must be considered before commencing with diving operations. Current direction and magnitude are important considerations when mooring a div ing vessel. When currents exceed 1 knot> tethered scuba diving operations should be avoided unless absolutely necessary and adequate provisions are made for diver control and safety. Heavily weighted surface-supplied divers are often more ef fective for stationary tasks in currents. Tidal currents may prohibit diving at some locations except when the tidal current changes direction slack water!. Consult tide tables when necessary and determine magnitude of tidal currents prior to diving. Tethered scuba diving is more desirable than self-contained diving operations during periods of low visibility fog> snow, rain, etc.!. Self-contained divers are particularly vulnerable
14 during periods of low visibility since they may lose orientation and be unable to relocate the diving vessel or support structure base. Alsoi the diving vessel may be in greater danger when anchored during periods of limited visibility. Tethered scuba diving is permissible under limited surface visibility conditionsi providing the diving vessel can safely anchor.
Ship traf f ic may constitute a hazard to diversi particularly self-contained divers. Et is necessary to display proper visual signals in a prominent location on the diving vessel during operations in order to notify approaching vessels that divers are in the water. The United Nations Naritime Group International Divers Flag is the single-letter signal "A" or alpha flag blue and white! ~ This flag is recommended for diving in all navigable wa ters and is currently used by the U.S. Navy and the ma jor nations of the world. The standard United States diver's flag red and white! should also be displayed.
Divers and support personnel must be protected from excessive exposure to adverse surface weather conditions. When working in tropical areas, the staging area should be shaded to prevent overexposure to sun. During cold weather in northern watersi divers and surface personnel must be protected from cold air temperatures and wind. Divers should not be expected to dress in an open> unprotected vessel. When working from small craf t, divers should dress prior to leaving the shore base. If under-ice dives are required, dress in heated shore facilities or heated portable structures on the ice. Do not subject divers to excessive exposure prior to the dive. Heated quarters should be available immediately after surfacing.
The selection of diving dress and equipment wil 1 depend on the mission, weather conditions, and type of vessel. For examplei even though water temperatures may permit the use of wet suits, cold air temperatures and wind would necessitate use of a variable-volume dry suit or equivalent! when diving from an open or unhea ted vessel.
The type of bottoa affects the diver's abi 1 ity to work and is a factor in determining visibility. Consequentlyi this must be considered in the preliminary dive plan and certain precautionary measures may be necessary to ensure the diver' s safety and efficiency. Mud si1 t and clay! bottoms are generally the most restrictive for divers. The slightest movement wi 1 1 stir sediment into suspension and restrict the diver' s visibility. The diver must orient himself so that the current> if any, will carry the suspended sediment away from the work area> and he must use a distance line. Since the self-contained diver is more hampered by the limited visibi lityi tethered scuba diving techniques should be considered for such work. For general survey work, self-contained or tethered scuba diving techniques have certain advantages. The diver can be weighted to be neutrally buoyant at survey depth and move about without touc hi ng the bo t tom. Sand bottoms present little problem for divers. Visibility restrictions from suspended sediment are less and footing is firm. In marine areasI the diver must be alert for stingrays buried in the sand.
Coral reefs are solid with many sharp protrusions. The di ver should wear gloves and coveral ls or a wet suit for protection if the mission requires considerable contact with the coral. Survey divers and photographers have to be cautious to avoid injury. Learn to identify and avoid corals and any marine organisms that might inflict injury.
Water depth is a basic consideration in the selection of personnel > equipment> and techniques. When possible, determine the depth accurately prior to diving and plan the dive duration, air requirementsi and decompression schedule accordingly. Although no standard rules have been established for civilian tethered scuba divingi a depth liait of 60 feet appears to be reasonable. Beyond 60 feet the use of conventional surface- supp 1 ied d i v ing is recommended.
Water teoperature is a major factor to be considered in dive planning since it will determine the type of equipment diving suits! and> in some cases< the practical dive duration.
Underwater visibility depends on local ityi water conditions> season> bottom type> weather> and currents. Dark or murky water is a disadvantage in all underwater operations. Self-contained diving should be avoided under zero to limited visibility conditions when possible and a tethered scuba or surface-supplied di ver used.
Tethered scuba and surface-supplied divers are at a considerable advantage, if decompression is required.- In addition to a descent shot! line, a distance line carried on a reel is required. This enables the divers to return to the shot line for controlled ascent.
Selection of Diving Techniques
The proper diving technique, scuba, tethered scubaI or surface-supplied, is based on the mission/task requirements, environmental conditions, and available personnel,. Zt is the responsibility of the diving supervisor and divers to review the situation and determine which technique to use. The advantages and limitations of each technique are important to know.
The advantages of scuba diving include equipment availabilityi simplicity of operation< portabilityI underwater mobility, cost> and numerous training facilities. To gain these advantages over conventional surface-supplied diving, the diver has sacrificed dive duration, reliable surface-to-diver communications, and, in some diving situations, safety. In addition< operational and economic efficiency is comparatively
16 lower for scuba diving opeeations. Conventional scuba diving safety practices require that at least two scuba divers work together as a team and stay in visual/physical contact throughout the dive. Most underwatee research and seaech/rescue tasks can be effectively accomplished by a single diver. Furthermore, in limited to zero visibility two scuba divers can easily become sepaeated and be of little or no assistance to each other in an emergency. In fact, scuba diving under limited to zeeo visibility may actual ly constitute a hazardous situation.
Each institution's Diving Control Board and on-site diving supervisors will ultimately determine the appropriate and inappropriate situations for use of a tetheeed scuba diver. In addition to limited visibility situations, tethered scuba diving has been found effective for under ice tasks< conducting diving opeeations feom small vessels under extremely cold sur face conditions, and when working in the vicini ty of numerous sensitive instruments where diver movement must be minimial. In cold water/surface diving situations from open vessels, the complete dressing, coordination, and deployment of two divers to perform a simple observation oe col lection task in 20 feet of unobstructed water seems a bit excessive when the task can be safely and effectively performed by a single diver. However> since tetheeed scuba diving may be a new operational mode for many divers and organizations,
ALL APPLICATIONS OF TETHERED SCUBA DIVING NUST BE EVALUATED AND APPROVED BY THE INSTITUTION'S OR ORGANIZATION'S DIVING CONTROL BOARD AND ALL PERSONNEL ADUST BE SPECIFICALLY TRAINED IN PROPER USE OF THE EQUIPNENT AND DIVING PROCEDUREf
Tethered scuba diving is a reasonable compeomise between scuba and surface-supplied diving. A single divee can-work safely and efficiently in limited visibility water. Safety is maintained through a direct connection to the surface and voice coamunication. The status of the diver can be monitored at a 1 1 times. Operational efficiency is greatly improved since only one divee is deployed at any given time. An efficient diver rotation schedule can be prepared to achieve maximum underwater time with minimum personnel. Scientific observations can be easily transmitted to the surface and eecorded on tape. The diver' s time, physical status> and emotional status cari be monitored by sur face peesonne l.
Tethered scuba diving cannot be considered as a replaceaent for either scuba or surface-supplied diving in all situations. The tethered scuba diver is effective within the distance limitations of the tether generally, not more than 200 feet long! and up to a depth of 60 feet. As in scuba di v ing < dive duration is limited by the amount of air contained in the breathing apparatus. On the other hand, the surface-supplied diver is more effective for deeper work, under more extreme environmental conditions, and in higher eisk situations. In the event of entrapment or entanglement< air supply duration is
17 unlimited. The scuba di ver is more effective for swimming great distances under water and performing tasks requiring extensive lateral and vertical mobility.
Final lyI equipment costs becomes a factor. Ideal ly, most diving tasks performed by a tethered scuba diver could be performed by a lightweight surface-supplied diver. However, the cost of outfitting a surface-supplied diving team is somewhat higher than for a tethered scuba div ing team, assuming that the team is already completely outfitted for scuba diving. tethered scuba upgrade involves purchasing two tethers, two compact communicators or one larger two-diver model!, two light~eight demand-type ful 1-face masks, and the necessary components to convert to an appropriate independent secondary regulator/air supply system. The surface-supplied diving outfit would require additional expense for an air supply and control system and a more expensive umbilical assembly.
Selection of Divers/Support Personnel and Assignaent of Task
The diver must be qualified and designated in accordance with the depth and equipment rating required for the mission or task. The diving supervisor is responsible for determining the qualifications of a diver before assigning him/her to a mission or task. In addition to the diver, the diving supervisor must designate qua 1 i f ied tenders, timekeepers/recordkeepers, and stand-by divers.
Selection of Equipaent
The diving supervisor and divers will determine whether to use scuba, tethered scuba or surface-supplied diving equipment for a particular mission based on a review of the mission requirementsi personnel available< and environmental conditions. The diver must be outfitted with the proper equipment to complete the task assigned. When selecting equipment, the diver should not be overburdened with accessories. Use only the equipment required for safety and completion of the task. When the diver is encumbered with excess equipment, the possibility of entanglement and fatigue increases.
Since the tethered scuba diver's dive duration is limited by the volume of air contained in the scuba, it may be necessary to estimate the amount of dive time available with a given air supply or the amount of time and air that will be required to perform a particular task. Standard air consumption procedures are given in most scuba diving training manuals. A simple method of calculating air supply duration is given in Appendix II.
Pulf illaent of Safety Precautions
All personnel associated with the diving operation are responsible for maintaining proper safety standards. Ul timately, the diving supervisor or team leader! must assume responsibility for the safety of the di vers. He/she must evaluate every aspect of the operation. Safety is considered in al1 aspects of preliminary planning. Divers must not be committed to a mission or task which is unreasonably hazardous or for which they are not suf f iciently trained or equipped. In evaluating environmental conditions and the dive site, the diving supervisor must train himsel f/herself to anticipate potentia1 hazards and take appropriate measures to protect the divers from these conditions. Natural ly, all hazards cannot be eliminated from any di ving operation but, they can be minimized. If a particular hazard is foreseeable, it can usually be eliminated. The diving supervisor may wish to prepare a list of potential hazards> including precautionary measures to use when setting up the operation and brief personnel.
The diving supervisor must verify that there are appropriate first aid supplies including oxygen inhalation equipment! available. He/she must establish an emergency protocol for diver and/or tender injuries that includes transportation, communications, medical attention personnel and source!, and recompression facilities location and availability!.
Establish Procedures and Brief Personnel
The diving supervisor or team leader< after careful evaluation of the above factors< wil 1 establish theoperational procedure and brief all personnel. The procedure and briefing should include> but not necessarily be limited to, the fallowing:
Objectives and scope of the operation;
Conditions in the diving area;
Dive plans and schedules;
Assignment of personnel: divers, tenders, etc., and speci f ic tasks for each;
Safety precautions; and
Special considera tions.
Diving Yessels
Research and rescue divers wil 1 be required to dive from vessels of various sizes and descriptions, ranging from small, inflatable, rubber boa ts< such as the Zodiac> to large 300-400 foot research vessels. The type and magnitude of diving operation and environmental conditions wil1 determine the type of vessel.
19 For example, nearshore diving in relatively calm water may be accomplished without much difficulty from a good rubber inf latable boat or smal 1 wood, metal, or fiberglass boat equipped with a dependable outboard engine. Nore extensive offshore diving operations must be undertaken from a largervessel with adequate deck space and seaworthiness. The fol lowing factors must be considered relative to the mission requirements: Adequa te si ze to corn for tab 1 yaccommodate di vers < surface personnel, and equipment; Sufficient stability and seaworthiness to function as a platform for diving operations;
Vessel well maintained, in satisfactory operating condition, and equipped with proper safety equipment as required by sta te and/or federal laws;
Largei open work area; Adequate protection from sun or cold; Nooring capability - or 4-point moorings may be requi red !; Suf ficient storage space to accommodatediving equipment when not in use; and An adequate ladder to facilitate entering and leaving the water. The diving ladder is a very important part of the boat' s equipment. Nost boats> unless speci f ical ly designed and equi pped for diving, will not have a ladder that is safe for use by divers. Serious injuries have resulted from the use of inadequa te ladders. The ladder should include the fo 1 lowing fea tures:
Neta 1 construction;
Extension 4-5 feet below the ~ater line; Rungs wide enough to al low comfortable use with bare feet and f ins; Handrail extending the ful 1 length of the ladder to give the diver a "hand hold" until he/she is completely on deck;
Inclination of about 10-15 degrees relative to the side of the vessel; and Secure enough to avoid movement when the diver is on it.
20 Assemble Equipment
The first step in actually preparing for the dive, as conteasted with planning, is to assemble and check the equipment. The most acceptable proceduee is to use a careful ly peepared checklist. This list wi11 cover all items and equipment that must be on hand at the diving station. It includes diving masks, suits> accessories< tools< first aid supplies> decompression tables< tethers> communicators> and> in general, everything known to be needed or likely to be needed during the planned dive. A sample list that a scientific tethered scuba diving operation might include is in Appendix I1I. Natural ly, each diver and supervisor will have special eequirements based on the type of equipment, diving conditions> and personal prefeeences.
The diving station should be neatly organized with all diving and support equipment in a designated location. Deck space should not be cluttered with gear> especially items that can be easily damaged> be kicked overboard> or injure personne1. A standard layout should be established and followed so that all members of the diving team will know where to find any item of equipment. Each item must be inspected and determined acceptable prior to the dive. Scuba< both primary and secondary, must be activated to assure that they aee in satisfactory operating condition peioe to the dive.
If air compressoes are used to fill scuba cylindees in the field, al 1 diving peesonnel must be familiae with the opeeation of the compressor. Prior to charging scuba cylinders, be ceetain to check oil> aie intake location relative to wind and exhaust!i fuel supply, and general condition. A complete compressor operation instruction manual should be available at the dive site. Monitor the compressor during operation and drain filter and moisture separators as indicated in the insteuction manual. Check air for objectionable odor. Ideally> assign a member of the team to monitoe the system while cylinders are being charged. Check air cylinders< filling mani folds> hoses> and filters for leaks. Periodical ly analyze the aie to insure that it meets purity standards.
Verify that the mask regulator is operating satisfactorily. Check the hose and fitting for leaks. Open cylinder valve and flow air through mask. Next~ attach communications cable to mask and diving station communications unit and check for proper transmission.
Diver Dressing Procedures
The dressing procedures will depend upon the type of diving dress or suit and mask used. Specific instructions for donning various types of diving suits are included in manufacturer's instruction booklets. Instructions foe preparation of specific masks must be obtained from the manufactueer's manual; a manual or copies of appropria te sections should be inc luded in the
21 diving supervisor's kit. Prior to starting dressing procedures, the air supply system should be operational and the mask completely prepared for diving. The following is a generalized dressing procedure applicable to most tethered scuba diving outfits:
Don diving dress or suit with assistance from the tender s! i f necessary;
2. Don diver's harness, secure, and adjust;
3 ~ Don buoyancy compensa tor if separa te f rom scuba !;
4. If ankle weights are used< they are placed on the di ver by the tender and secured. Fins may be donned later with the assistance of the tender;
5. Don, ad j us t, and secure scuba;
6 ~ Connect BC hose and verify operation for separate ac!;
7. Don and adjust weight belt;
8. Secure knife to harness< leg, or arm diver' s preference!;
9. Don mask and secure mask harness;
10. Secure the tether to harness;
11. Veri f y proper opera tion of scuba and communica tions; and
12. The tender ensures that the diver is properly dressed, that all equipment is functioning properly, and that the diving supervisor is informed that the diver is ready.
The Dive
When all personnel have completed dressing diver and stand- by diver!, checking equipment, and final briefings, the captain if diving from a vessel! is notified that the diver is ready to enter the water. He/she must give clearance before the diving operation can commence. Entry technique will depend upon staging area or type of vessel. The diver should enter the water using a ladder or use an appropriate scuba diving entry. Upon entering the water> the diver should stop a few feet underwater to make a final equipment check. The dive procedure is as fol lows:
l. Adjust buoyancy i f necessary. Whether the diver is weighted neutral or slightly negative wil 1 depend on the mission requirement.
22 Ensure tha t air supply, mask, and communications are functioning properly. If not, corrections must be made prior to descent. Check for leaks in air supply fittings and suit. The tender should look for air bubbles. Never dive with ma l f unc tioning equipment.
The tender should also verify that all equipment is functioning satisfactorily.
The diver is given permission to descend by the di v ing super v isor/ tender.
The diver descends down a descent or "shot" line, if available. A timer is started when the diver begins his/her descent. Descent rate wil1 depend on the diver; however> it should generally not exceed 75 f t/min. NOTE: Shot 1 ines or descent lines are commonly used in surface-supplied diving. Most tethered scuba divers consider this to be optional or useful for only specific diving situations. They are concerned about entangling the tether in the descent line when actively moving around on the bottom. This is a potential problem for most beginning tethered divers. Proper tether management is achieved through experience.
The diver must equalize pressure in his/her ears and sinuses during descent. If equalization is not possibles the dive must be aborted.
When descending in a tideway or current, the diver should keep his/her back to the current so he/she. wil 1 be forced against the descent line.
When the diver reaches the bottom, he/she should inform the tender of his/her status and ensure that the tether is not fouled in the descent line.
Regulate buoyancy if necessary before releasing descent li ne.
Attach distance line, if used, and proceed to work area. A distance line is useful when visibility is extremely poor and the diver cannot see his descent line from a distance. This is a surface- supplied diver's technique that may or may not be as necessary for the tethered scuba diver. Returning to the descent 1 ine could be exceptional ly useful if decompression is required.
Upon leaving the descent line, proceed slowly to conserve energy. Zt is advisable to carry one
23 Curnof the CeCherin yourhand. 12.Pass over, not under, wreckage andobsCruction. 13.If movingagainst a curcenti it maybe necessary vto eryassume near thea crawling boC tom.position oriat least, swim 14.If thedi ver is required to enter wreckage> tendtunnels,his/her etc.,tether a secondatthe diverentrance. should Naturalbedown ly,to priortake thisplanning into consideraandpersonnel tion. assignments would 15.monitorAvoid excessivebreathing exertion.raCeand call Thefor Cenderthe diver shouldto avoid"atop+excessiverest> andexci ventilate"tement. Thisasrequired. can enhance Also,the alwaysonsetofbes fatigue.t in anemergency. Slow methodical efforts are 16.The tender mustkeep thediver conatantly informed offewhis/her minutes bottomin advancetime. Alwaysof terminationnotify the timediver soa ascent.he/shecancomplete his/her task and prepare for 17.theDiver environmental movements andconditionprocedures and depend Cask. Largely upon Tending the Diver experiencedTendingdiversis anor art.persons Surfacespeciallytenders trained should astenders. alsoThe be mostfamiliareffectivewith theassistance equipmenti canprocedures,begiven onlysafety bya precautions,tender who is conditions>thetender's andresponsibilitydifficulties tothatsee arethat inherent the diver inreceivesdiving. properIt is equipmentcarewhile beforeboth topsidesending theand diverunderwater. down. He/shemust check al1 checkingWhenequipmentithediver and isassistsready, thethe divertender tohelpsthe ladderwith dressingor entry i strainpoint.onThethe tenderdiver handlesas he/she thedescendstether andthemaintainsladder. Fora scubaproper divingfreely. typeentries thetender assures thatthe tether plays out maintainsWhilecommunications,thedi ver is submerged,' andmonitors theairtender usage handlesby periodical the tether, ly communicationsrequestingpressurebetweenreadings diverfrom andthe tender di ver. isby The voice usual inCercom;means of practicedhowever,itso istheyimportant wil 1 thatberecognizedbasic line instantlysignals bein memorizedthe event andof
24 intercom failure or if apparatus not fitted with an intercom is used. The fol loving are line or hand signals given by the U.S ~ vavy for air di ving [3 j:
Tender to Diver *
l pu 1 1 ------Are you a 1 1 right? When the diver is descending, 1 pu 1 1 means stop!.
2 pul ls-----Go down. During ascent< you have come up too far. Go back down until I stop you.!
3 pul 1 s-----S tand-by to come up.
4 pulls-----Come up.
2-1 pulls----I understand, or answer the telephone.
Diver to Tender ~
1 pull---- I am all right.
2 pulls-----Give me slack or lower me.
3 pulls-----Take in my slack.
4 pulls-----Haul me up.
2-1 pulls----I understand, or answer the telephone.
Eaergency Signals: Diver to Tender
2-2-2 pulls--I am fouled and need the assistance of another diver.
3-3-3 pulls--I am fouled but can clear myself.
4-4-4 pulls--Haul me up immedia tely.
Special signals may be prepared to meet mission requirements. Re s c u e d i v e r s may wish t o c o n s u 1 t the Dive Rescue ~Ss c i a 1 i s t Teainince manual for line signal information Tl j.
In tending the diver's tetherf the tender must not hold the tether so taut as to inter fere with the diver's work or movements. The diver should be given 2 or 3 f t of slack when he/she is on the bottom, but not so much that he/she cannot be felt from time to time. Signals cannot be received on a slack line; consequently, the diver's tether must be kept in hand with
25 proper tension at a 1 1 times. Line-pul1 signals consist of a series of sharp, distinct pul 1 s,strong enough for the diver or tenderto feel but not so strongas to pul1 thediver away from his/her work. When sending signals,take al 1 of theslack out of the line first. Repeat signal until answered.The only signal not answeredwhen receivedis theemergency "haul me up", and "come up" is delayed until the diver is ready. Continuedfailure to respondto signalsmay indicate that thereis toomuch slack in the line, the line is fouled 2. If voice communicationis lost' it is best to terminatethe dive immediatelyin order to resolve the problemor reorganize the dive plan. 3. If the tender receives no immediateline-pull signal reply from the diver< he/sheshould take a greater strain on the tether and signal again. Considerableresistance to the tender'spul 1 may indicate that the tether is fouled or the diver is trapped and unconscious. A stand-by diver should be dispatched as soon as possible. 4. If the tender feels sufficient tension on the line to conclude that it is stil 1 attached to the diver, yet receives no signals, he/shemust assume that the diver is unconscious. In this event> he/she should dispatch a stand by diver immediately. If a stand-by diver is unavailable< or it is considered unwise to use one, the diver must be pul led very slowly to the surface. Prepare to administer first aid and recompression.Note: If the diver is wearing a closed-dress or variable- volumedry suit, this procedureis usedonly as a last resort. Subsequent blow-up is almost unavoidable without the assistance of another di ver. The tender should continuously monitor the diver' s underwatertimer andair supplypressure. He/sheshould inform the diver severalminutes before the expiration of bottomtime so that the diver canmake necessary preparations for ascent.The tenderkeeps track of the diver's positionby observingbubbles rising to the surfaceand informs the diver of his/herposition relative to the boat/diving station. In addition 26 tender can frequent Ly evaluate the diver's exertion by counting the number of breaths per minute. Experienced tenders will learn the di ver's normal brea thing ra te. S igni f icant. increase in breathing rate may indicaCe potential over-exertion. The tender may ask the diver to sCop work> rest, and ventilate. The tender may also have Co serve as timekeeper. This job includes keeping an accurate record of the dive time and details of the dive. When possible, a separate timekeeper should be used or the timekeeper duties handled by the diving supervisor. Ascent When the diver has reached his/her bottom time limit, the task is completed> or the air supply pressure has reached a predetermined level> the diver will return to the ascent line if available! and notify the tender that he/she is beginning ascent. The ascent procedure is as fol lows: The tender wil 1 pull in excess tether and take a slight strain on it. He/she wil 1 pull slowly and steadily at the prescribed rate not to exceed 60 feet per minute!. The tethered scuba diver of ten controls his/her ascent and swims to the surface; the tender simply keeps the tether taunt. The diver must regulate his/her BC and suit buoyancy. The diver must be careful to avoid overinf lation of dress and subsequent blow-up. 3. The diver should not let go of the ascent line if used!. He/she should maintain neutral buoyancy or may "climb" the line to aid the tender. Scuba divers accustomed to free swimming ascents may initial ly find the use of ascent lines and management of the tether awkward. However, these techniques add an element of sa fety and control in most diving situations. 5. The tender or dive supervisor must inform the diver well in advance of any decompression requireme n ts. 6. When decompression is completed< the diver is taken on board via the ladder. Post-Dive Procedures The diver shouLd be helped from the water and aided wi th removal of equipment by surface personnel. The fol lowing procedure is recommended: 27 Remove weight belt, ankle weights, and fins. 2 Disconnect air supply hose to dry suit and sepa ra te BC. Rema ve mask. 4. Di sconnec t te ther f rom harness. 5. Remove scuba. 6. Remove buoyancy compensa tor if separa te from scuba ! ~ 7. Remove diving suit as appropriate! . If the equipment is not to be used again that day: 1. Disconnect tether communications wires from mask. 2 ~ Close scuba valve> vent mask< and remove regulator from cylinder valve. 3 ~ Repeat procedure for secondary regulator ~ 4 ~ Coil or bag tether and secure for transport or storage. 5. Place mask in upright position, rinse external surface with fresh water> and wipe dry. 6. Clean interior of mask and > i f necessary, wash wi th a damp sponge and wipe dry. 7. Rinse other equipment with fresh water > dry< and stow. Preventive maintenance on equipment should be undertaken as soon as possible following the dive. Specific instructions are given for masks and suits in appropriate manufacturer's manuals. The divers and tenders must report any defects noted during or after the dive and the defective equipment must be tagged for correc ti ve ma in tenance. The warming process should be commenced as soon as the diver surfaces. The diver must be continuously observed for signs of sickness or injury resulting from the dive. The diver should be debriefed as soon as possible and the dive log completed. The timekeeper and diving supervisor are responsible for the diving log. The diver should receive a copy of the deck log or be given appropriate information in a formal debriefing so he/she can complete his/her personal di v ing log. 28 UNDERNATER ENERGENCY PROCEDURES The tethered scuba diver wil 1 deal with undeewater emergency situations in much the same manner as a conventional scuba diver, however> he/she will not have the benefit of assistance from another diver unless a stand-by diver is deployed. Aie supply depl e Cion or regula Cor mal func Cion is probably the mos C threatening to Che diver. The diver must also be trained in purging water from a flooded ful 1-face mask, dealing with loss of communications, and freeing a fouled Cether. Such topics as diver rescue on the surtace, stress managementi accidental ascent resulting feom BC oe dry suit overinflation< and so on will not be addressed in this publication. Divers entering tethered scuba diving training should already be familiae with these procedures through basic scuba diving training. Natuea1 ly, peoper diving procedures and common sense peecautions can prevent mostI if not al 1 > underwater emergencies from developing. t.ops of Peiaary Air Supply A tethered scuba divee need never be faced with the loss of the primary air supply if proper precautions are taken to monitor the available air throughout the dive, to observe a policy of arriving back at the surface with no less than 300 to 500 psi of air remaining depending on the scuba used and the diving conditions!, and to use properly maintained equipment. A diver' s air supply can be depleted and lost with little or no warning theough carelessness and equipment mal function. If a diver does not routinely monitor his/her air pressure gauge, air can be depleted without warning, especially if the diver is working hard or is extremely cold. The tethered scuba diver has an advantage over the average scuba diver in that the tender and supervisor can periodical ly remind him/her to check the pressure gauge. A prudent tender/supervisor will monitor the diver's air consumption. Using simple calculations, the supervisor can estimate the rate of consumption. Through expeeience the tender and supervisor can make judgments with regard to the diver's physical status and air consumption by listening to breathing sounds and patterns. In addition, obseeving bubble patteens at the surface will give some indication of the diver's status. For example> if breathing is deep and rapid hyperventilation! the diver is probably either working extremely hard or experiencing stress. A pattern of large bubble bursts at the surface also suggest the same. In either case the tender/supervisor must talk to the diver and help him/her correct the situation. If the situation cannot be resolved< the supervisor must order termination of the dive. On the other hand, if the tender observes a continuous stream of bubbles arriving at the surface and hears constant air flow over the communicator, this can indicate that the diver is operating his/her mask in a free-flow mode. The diver may be so involved in a woek task that he/she is unaware of the free-flow. 29 In this case the tender will request that the diver check for improper valve adjustment and correct the situation. If the free flow cannot be corrected by the diver, the dive is termina ted. In another case, the diver's breathing pattern and communic~ tions sounds may be normal, but the tender observes a steady stream of bubbles coming to the sur face in addition to normal breathing bubbles. This could be an indication of secondary regulator leakage. The diver must be notified< equipment checked>and the condition resolved. Again> if the situation cannot be resolve on the bottom by the diver< the dive must be terminated. The role of the tender/superv isor in preventionof diving eeergenciescannot be over-emphasized. Regulator Free Flow. I f the regu la tor begins to f ree f low as a result of freezing or other mal function, the diver simply continues to breath and attempts to reduce the free flow by manipulating the second stage pressure adjustment valve if so equipped!. If the free flow can not be resolved> the diver must begin ascent immedia te 1 y. Excessive ai r wi l 1 be discharged through the exhaust valves and around the face seal. In regulator freezing situations the free flow wil 1 general ly increase with time. Do not attempt to switch to an alternate air source unless the extent of free flow makes breathing impossible an unlikely situation!. Voice communication to the tender may be severely compromised by the sound of the rushing air. However, the tender wil 1 be aware of the situation when he/she hears the rush of air in the earphones and will general ly start. to take in slack on the tether. Line signals may be used. Breathinq Resistance. If the diver begins to experience increased breathing resistance, he/she must first check the scuba air pressure. If the pressure gauge is at or near zero, the diver should immediately notify the surface and begin a control led ascent. If possible< breath lightly and avoid deep, rapid breathing. If resistance is so great that the diver can not receive sufficient air for breathing> he/she must activated the emergencyair supply if using a separate scuba emergencyair supply system! and continue a controlled ascent. Always notify the tender if such actions are necessary. Keep in aind that air supply depletion negates the use of an secondary regulator attached to the saae air source i e.< dual aanifold or slingshot val ve systea! l For this reason manytethered scuba divers wi 1 1 elect to use a separate compact scuba system. Let's assume that the air supply pressure gauge indicates that there is signif icant remaining air, yet the diver is experiencing breathing resistance. In this case the diver can quickly operate the second stage adjustment valve in order to determine if that will temporarily correct the restriction. In addition> the diver may push the regulator purge button to increase air flow. If there is sti 1 1 breathing restriction, the 30 diver should assume that the air supply is depleted or primary regulator is malfunctioning! and immediately begin ascent. Pressure gauges have been known to malfunction and give false readings. Even if the situation is corrected, notify the surface and terminate the dive. The abnormal function of the regulator must be corrected or the regulator must be replaced. Instant Regulator Failure. Although regulator failure resulting in immediate loss of air supply is seldom, if ever, heard of in modern scuba diving> it is possible. Generally, a regulator malfunctions to a free-flow mode. In the past< the author has observed first stage malfunction resulting in immediate loss of air supply as a result of internal high pressure air leakage into a secondary low pressure chamber in a diaphram type balanced first stage. On another occasion> one of the author's scuba diving students experienced instant air supply loss when the swivel part where low pressure hoses are attached! of a piston first stage regulator seperated from the rest of the regulator. In such an event the properly equipped tethered scuba diver could immediately activate the emergency air supply regulator, either dual manifold/slingshot valve type or separate scubaI and surface. If air is obviously escaping from the primary regulator as in the above mentioned example, an effort should be made to turn off the valve to that regulator. However, the diver should not remain on the bottom for a lengthy time attempting to turn off the valve> especial ly if the malfunction occurs near the end of the dive when the air supply is a 1 ready low. If all other options for resolving a loss of air supply situation fail, the diver can still make a controlled emergency swimming ascent. Plooded Full-Pace Nask In the event that a demand type full-face mask is accidental ly flooded partially or completely! water can be evacuated by positioning the head so that the exhaust valve is at the lowest point and depress the purge button on the face of the regulator. Air wi1 1 rush into the mask and displace the water through the exhaust valve and around the face seal. Gently pressing the mask against the face will help prevent additional water from seeping in around the face seal. Nask flooding is rare. If the mask is not properly fitted and adjusted the diver may experience leakage immediately upon entering the water. Standard diving practice includes stopping a few feet below the surface for a final equipment check before descending to the bottom. I f the face mask is leaking> the di ver should take immmediate measures to correct the problem or return to the surface for assistance. It is possible for the face mask to flood or leak underwater if it is dislodged by impact or if one or more spider head harness! straps were to break. 3l, If the mask floods or begins to leak without warning or obvious cause> the diver should check the spider by feeling with his/her hand. After purging the mask< the diver should hold it against his/her face with one hand while checking for the cause with the other. If leakage continues, the diver should notify the tender and immediately begin ascent. CONSULT THE NANUPACTURER' S OPERATIONS AND NAINTENANCE MANUAL POR SPECIFIC NASK PURGING PROCEDURES ' En tang leaent A tethered scuba diver's tether may become fouled or entangled in mooring line, propel lers, wreckage, debris, natural bottom formations i.e., reef or rock! > kelp or manmade underwater stuctures. Entanglement can usually be prevented though proper management of the tether by both the diver and the tender. The tethered scuba diver has both advantages and disadvantages compared to the surface-supplied diver. The primary disadvantage is the limitation of air supply. If the entanglement occurs near the end of the dive< the air supply may be too limited for a lengthy untangling procedure or for waiting for a stand-by diver. This is one reason for establishing a policy of planning to arrive at the surface with at least 500 psi remaining; this extra air could provide the margin needed to resolve the situation. 1 In the event of suspected tether entanglementr the diver should ! remain calm> ! think, ! inform the tender/ supervisor of the situation, and ! systematically attempt to determine the cause and to free himself/herself. If efforts to free himself f/herse 1 f fa i 1, the~e are two possible options. Firsti the stand-by di ver may be deployed to correct the situation from the other end. In this case the di ver simply remains calm and waits. The tender/supervisor should remain on the communicator to reassure the diver that proper action is being taken and to discuss other options available. Secondly, the diver may elect to disconnect the tether from the safety harness/mask and swim freely to the surface using a normal scuba diving ascent. Prior to disconnectingi the diver and the tender/supervisor should discuss the situation completely and make a joint decision. The tether can be retrieved later or discarded. Keep in mind that some tethers will float and the floating portion of the discarded tether could foul in a boat propeller. Consequently< this practice is discouraged. The diver may also become entangled in fishing line or nets or be trapped by shifting objects around manmade structures or wreckage!. The action on the part of the diver is basical ly the same as above. In this case the diver may carefully use his/her knife to cut away the entangl ing material. If trapped under 32 heavy objects or hopelessly entangled< a stand-by diver will have to be deployed. If a dive team must use tethered scuba instead of conventional surface-supplied diving equipment in an area where entrapment is considered to be of greater than normal potential > extra scuba cyl inders should be a vai lable. The stand-by diver could supply the trapped diver with additional air while the si tua tion is being resol ved. In any tethered diving activity, the diver should proceed cautiously underwater and attempt to recognize obstructions which might cause entanglement or entrapment. The diver should pass over or around an obstruction, not under it. proper precautions can usually avert entanglement. K ass of Coamunications The procedures for tenders if communication is lost have been discussed. If the diver is unable to maintain voice communication with the tenders he/she should immediately terminate the underwater task and signal the tender by line pull that he/she is ready to surface. If there is no response from the surface, the tether is probably entangled or snagged and the diver should attempt to untangle the tether or wait for a stand- by diver. If the tether is clear and no resistance is felt when pulling on iti the diver should proceed to surface. SUNNARY Tethered scuba diving is an acceptable alternative to conventional scuba and surface-supplied diving for performing selected underwater tasks. This mode of diving can provide the rescue and scientific diver with a method to increase economical and operational ef ficiency while maintaining optimum safety. The additional equipment required for tethered scuba diving is readily available from commercial and rescue diving equipment suppliers. Most competent scuba divers can be easily trained in tethered scuba di ving techniques. The tethered scuba diving procedures and equipment discussed in this publication are used on a limited basis at present. As this mode of diving gains popularity among rescue and scientif ic divers, techniques, equipment, and procedures for safer and more efficient diving wil1 no doubt evolve. All divers and organizations are encouraged to use this mode of diving with a high respect for diver safety. Diving Control Boards are encouraged to evaluate diving operations on an individual basis before approving the use of tethered scuba diving. In addition, Boards must monitor tethered scuba diving training programs and acti v i ties to insure safe ty. 33 REPERENCES Linton, S., Rust, D ~, and Gi 1 lman, T., The Dive Rescue S ecia list Trainin Nanua 1 Fort Col 1 ins, CO.: Concept Systems, Inc., 1986T. 2 ~ U. S. Department of Labor< Occupational Health and Safety Standards, Part 1910' Subpart T> Commercial Diving opera tions washing ton< D.c.y 1977!. 3 U. S. Navy, U.S. Navy Divan Nanoal, Navsnlps 0994-001- 9010, ~Washington, D.C.: U.S. Government Printing 0 f f ice, 1978!. 4 ~ U. S. Department of Transportation, Coast Guard, Title 46, Chapter 1P Subchapter 5> Part 197P Subpart 8> commercial Diving Operations washington, D.C., 1978!. 34 APPENDIX I TETHERED SCUBA DIVING TRAINING PROGRAM Orientation 6 Adainistration Classroom 2 hours! Introduce staff; give overview of tethered scuba diving course and applications: provide historical information; discuss OSHA or AAUS! regulations; verify student's scuba diving certification and experience, complete Acknowledgement of Risk and Health Status forms; col lect fees; distribute manuals and handou ts Equipeen t Classroom 2 hours! Review basic scuba equipment as required!; introduce full-face masks, tethers< and communications units design~ use< and maintenance!: discuss dual manifold and secondary scuba systems; describe preparing a diving station Diving Procedures Classroom 3 hours! Teach dive planning; tethered scuba div ing operationa 1 procedures; personnel requirements and responsibi 1 i ties supervisor, recordkeeper/timekeeper, diver, tender, stand-by diver!; tending procedures and techniques; emergency procedures Specialized Water Training I Conf ined Water - 2 hours! Establish a diving station; prepare equipment; perform pre-dive inspections; deploy, tend, and retrieve divers; connect> check> and use communica tions uni ts; ma inta in equipment Specialized Water Training II Conf ined Wa ter 2 hours! Practice Water Session I activities; demonstrate and practice emergency procedures flooded face maskI loss of communica tions, air supply failure, and entanglement!; stand-by diver deployment; emergency ascent S peciali zed Water Trai ning I I I Openwa ter - 3 hours! Same as Water Session I but in openwater< maximum depth 25 feet/ f rom dock or pier! Specialized Water Training IV Openwa ter 3 hours! Same as Water Session II but in openwateri maximum depth 25 feet, from dock or pier! Specialized Water Training V Openwater 4 hours! Same as Water Session I but in openwater> maximum depth 40 feet, from boat!; demonstrate and practice rigging and anchoring boat SpecializedMater Training VI Openwater- 4 hours! per form an underwa ter research, search, or rescue simula tion using boat Specialized Water Session VII Openwater - 4 hours! Same as Water Session VI; include a problem solving emergency situation Additional training sessions and supervised on-the-job training dives maybe required at the discretion of the instructor prior to final qualification/authorization of a student as a tethered scuba diver. 36 APPENDIX II ESTINATINC DIVER AIR CONSUNPTIOM & AYAILABLE AIR SOPPLY The diver must be supplied with sufficient air to complete the underwater task. In many cases the dive and task wil 1 be planned in accord with the available air supply. Air consumption is a function of depth, exertion> water temperature> thermal protection, scuba performance< and individual physiological/ psychological variables. In some situations high air supply requirements will preclude the use of scuba or tethered scuba! and surface-supplied equipment will be required. In the past< considerable emphasis was placed on "exact" calculation of diver air requirements. Today' many authorities find such precise calculations impractical because of the wide range of variables. Realistical lyi the diver can only roughly estimate the amount of underwater time for a given amount of air on a basis of theoretical calculation and/or past experience. Ultimately> the actual dive duration will be limited by no- decompression time or planned dive time! and monitoring the scuba pressure gauge to assure that the air supply is not depleted or reduced below a safe level. As a general rule, tethered scuba divers are instructed to return to the surface with approximately 300 to 500 psig air remaining in the scuba depending on the scuba and diving conditions!. Approximate air requirements for a given depth and exertion level may be calculated using the formula Pa x Cs = Cd, where P is absolute pressure at the diver's ~orking depth expressed in terms of the nearest atmosphere, C is the diver' s surface air consumption at a given exertion leve > and Cd is the consumption of air at depth expressed in standard units volume of air consumed from scuba converted to measurement at one atmosphere ! . The average surface air consumption C ! expressed in cubic feet per minute cfm! for various exertion levels is approximately: Light exertion/warm water 0. 5 cfm Nodera te exer tion/warm wa ter 1 cfm Heavy exertion/warm water 2 cfm Moderate exertion/cold ~ater 2 cfm Heavy exertion/ cold water 3 cfm 37 For example, air consumption for an aveeage diver performing at a moderate work level in cold water at a depth of 60 feet is estima ted to be 3 x 2 = 6 cfm. The amount of air available to the diver depends upon the size of the scuba cylinder s!, the initial cylinder pressure< and the amount of aie that wil 1 be held in eeserve for surfacing and possible emergency. The amount of air available in a cylinder expressed in cubic feet V ! may be determined using the formula P X K = V I where P rated volume divided by rated peessure! is the measured cylind%e pressure and is a "constant" for a given sized cylinder. The constants K! for standard scuba cylinders are: 72. 0 cf/3000 ps i a 1uminum .0240 71. 2 cf/2475 psi steel . 0288 80.0 cf/3000 psi aluminum .0267 94.6 cf/3300 psi steel . 0287 95 ~ 1 cf/2640 psi steel .0360 75.8 cf/2640 psi steel .0287 71.4 cf/3300 psi steel 0216 Iet's assume that a tethered scuba diver plans to perform at a moderate work level in cold water at a depth of 60 feet using a twin 80 cf aluminum cylinder scuba filled to a pressure of 3000 psig. The diving supervisor indicates that the diver must surface with approximately 300 psig air remaining in the scuba and should plan to complete all work by the time the pressure gauge reads 500 psig. The amount of air available in cubic feet may be deteemined as follows: 000 - 500! x .0267 x 2 = l33. 5 cf As previously determined> an average diver working at this depth undec these conditions wi1 1 consume approximate 6 cfm. Theeefoee ~ the diver can expect to have 133.5 cf or 22.3 minutes 6 cfm to descend to the work site and complete the task. In reality> the diver in the above example would peobably have more time than indicated by this calculation, especially if the di ver is wearing a good thermal peotection system. However, a diver who is already cold at the surface wearing a wet suit in very cold water might be foetunate to have even 22 minutes to complete the task before the available air supply is depleted. 38 APPENDIX III TETHERED SCUBA DIVING EQOIPNBNT LIST 2 Masks with regulators including pressure gauges diver and stand-by diver! 2 Tethers 50 to 200 f t long! 2 Wet or dry suits complete! 2 Dive timers for divers to control ascent! 2 Depth gauges 2 Scuba complete wi th secondary regulators or compac t emergency scuba 2 Safety harnesses 2 Weight belts; leg weights as required 2 Diver's knives 2 Swim fins pairs! 2 Buoyancy compensators with hoses 1 High-pressure air compressor alsoI second compressor if working at sea or in remote location! Note: maybe considered op ti ona 1 i f air ref i 1 1 s are acquired from a commerical outlet on shore 2 Compact communica tions units 1 First aid kit including oxygen inhalation unit! 1 Decompression tables comple te se t! 1 Field log and pencils on clipboard! 2 Diver's flag Alpha and American Diver! 1 Tool and repair kit including: Assorted open end and adjustable wrenches Knife Wire cutter pliers Tape duct and electrical plastic! Screwdriver 39 Suit repair kit cementi seals> etc. ! Communica tions connec tor Ba t te ry f or communicator ex tra ! Mask de fogging compound Zipper lubricant Nylon or cotton cord general purpose, l00 ft! Silicone spray WD-40 lubricant Mask speaker/earphone extra set! Assorted spare parts for equipment l Diving manual l Safe Practices manual l Descent line/weight 2 Gloves for tender pa irs! l Distance line Equipment chest and bags use chest for seat! Sufficient number of extra scuba cylinder units to comple te assigned task Each dive team should prepare list of both team and individual diver equipment requirements. 40 Michigan Sea Grant College Program DIYER EDUCATION SERIES Under Ice Scuba Diving MICHU-SG-86-500! $4.00 Selecting a Personal Thermal Protection System M ICHU-SG-86-501! $0.75 Thermal Stress and the Diver MICHU-SG-86-502! $1.00 Physiology of Breath-Hold Diving MICHU-SG-86-503! $1.50 Introduction to Scuba Di ving M ICHU-SG-86-504! $1.25 Yoluntary Requalification NICHU-SG-86-505! $1.00 Recordkeeping for Divers M ICHU-SG-86-506! $1.00 Buoyancy and the Scuba Diver MICHU-SG-86-507! $1.50 Oceanography for Divers: RIavesi Tides, and Currents M ICHU-SG-86-508! $2.00 Respira tion and the Diver M ICHU-SG-86-509! $0.50 Ocea nogra phy f or Divers: Hazardous Marine Life MICHU-SG-86-510! $2.00 Drinking and Diving: If You Can't Spit< Don't DiveR MICHV-SG-86-511! $1.00 The First Responder M ICHU-SG-86-512 ! $2.50 The Diver's Knife MICHU-SG-86-513! $0.75 Selecting a Scuba Diving Buddy NICHU-SG-87-501! $1.50 Oceanography for Divers: Nearshore Hydrographic Survey Using Divers NICHU-SG-87-502! $2.50 Tethered Scuba Diving NICHU-SG-87-503! $2.25 To order any of the above or for information on bulk prices or additional titles< contact: Nichigan Sea Grant Publications 2200 Bonisteel Blvd. The University of Michigan Ann Arbor, Michigan 48109 313/764-1138