11-2 OPERATIONS PLANNING

OPERATIONS PLANNING

Normal diving procedures generally apply to diving in extremely cold environments. However, there are a number of significant equipment and procedural differences that enhance the diver’s safety.

Planning Guidelines. The following special planning considerations relate to diving under/near ice cover or in water at or below a temperature of 37°F:
                   

• The task and requirement for ice diving should be reviewed to ascertain that it is operationally essential.

• Environmental conditions such as ice thickness, water depth, temperature, wind velocity, current, visibility, and light conditions should be determined. Ideally, a reconnaissance of the proposed dive site is performed by the Diving Supervisor or a person with ice-covered or cold water diving experience.

• The type of dive equipment chosen must be suited for the operation.

• Logistical planning must include transportation, ancillary equipment, provisioning, fuel, tools, clothing and bedding, medical evacuation procedures, communications, etc.

NOTE:
            The water temperature of 37°F was set as a limit as a result of Naval Experimental Diving Unit’s regulator freeze-up testing. For planning purposes, the guidance above may also be used for diving where the water temperature is above 37°F.

 

Navigational Considerations. Conditions in cold and ice-covered water affect diver underwater navigation in the following ways:
                   

• The proximity of the magnetic pole in polar regions makes the magnetic compass useless.

• The life of batteries in homing beacons, strobes, and communication equipment is shortened when used in cold water.

• Surface light is so diffused by ice cover that it is nearly impossible to determine its source.

• Direct ascent to the surface is impossible when under the ice and determining return direction is often hindered.

• In shallow ice-covered waters, detours are often required to circumvent keels or pressure ridges beneath the ice.

• With an ice cover, there are no waves and therefore no ripple patterns on the bottom to use for general orientation.

Scuba Considerations. Scuba equipment has advantages and disadvantages that should be considered when planning a cold water dive.
                   

 The advantages of using scuba are:

• Portability

• Quick deployment

• Minimal surface-support requirements

 The disadvantages of using scuba are:

• Susceptibility of regulator to freezing

• Depth limitations

• Limited communications

• Severely limited ability to employ decompression diving techniques

• Duration limitations of CO2 removal systems in closed-circuit UBA

Scuba Regulators. Refer to the ANU for selection of proper regulator. The single-hose regulator is susceptible to freezing. The first and/or second stage of the single-hose regulator may freeze in the free-flow position after a few minutes of exposure in cold water. The single-hose regulator should be kept in a warm place before diving. It is important that the diver test the regulator in a warm place, then refrain from breathing it until submerging. When returning to the surface, the regulator should remain submerged and the diver should refrain from breathing from the regulator until resubmerging. The diver’s time on the surface should be kept to a minimum. Once under the water, chances of a freeze-up are reduced. However, if a regulator is allowed to free-flow at depth for as little as five seconds, freeze-up may occur. The diver should therefore avoid purging the second stage of the regulator when diving in cold water. If water needs to be purged from the mouthpiece, the diver should do so by exhaling into it (Figure 11-1).

Special Precautions. Single-hose regulators should be equipped with an antifreeze cap, which is a special first-stage cap that can be filled with liquid silicone available from the manufacturer. Correct maintenance and application of an approved lubricant to the appropriate points are also essential. Extra precautions must also be taken to make sure that scuba cylinders are completely dry inside, that moisture-free air is used, and that the regulator is thoroughly dried prior to use.

Octopus and Redundant Regulators. Where water temperature is at or below 37°F, a redundant scuba system (twin scuba bottles, each having a K-valve and an approved cold water regulator) or twin scuba bottles with one common manifold and an approved cold water regulator (with octopus) shall be used.

Life Preserver. The use of life preservers is prohibited only when diving under ice. The accidental inflation of a life preserver will force the diver upward and may cause a collision with the undersurface of the ice. Should the diver be caught behind a pressure ridge or other subsurface ice structure, recovery may be difficult even with tending lines. Also, the exhaust and inlet valves of the variable volume dry suit will be covered if a life preserver is worn. In the event of a dry suit blowup, the inability to reach the exhaust dump valve could cause rapid ascent and collision with the surface ice.

Face Mask. The diver’s mask may show an increased tendency to fog in cold water. An antifog solution should be used to prevent this from occurring. Saliva will not prevent cold water fogging.

Scuba Equipment. The minimum equipment required by every Navy scuba diver for under-ice operations consists of:

• Wet suit/variable volume dry suit

• Open-circuit scuba with cold water modification or closed-circuit UBA

• Face mask

• Weight belt and weights as required

• Knife and scabbard

• Swim fins

• Wrist watch

• Depth gauge

• Submersible scuba bottle pressure gauge

• Harness such as an Integrated Divers Vest (IDV), MK 12 jocking harness, etc.

• Lifelines

A variety of special equipment, such as underwater cameras and lift bags, is available to divers [see the NAVSEA/00C Authorized for Navy Use (ANU) list for specific identification of authorized equipment]. However, the effect of extreme cold on the operation of special equipment must be ascertained prior to use.

Surface-Supplied Diving System (SSDS) Considerations. Using SSDS in icecovered or cold water requires detailed operations planning and extensive logistical support. This includes thermal protection for an elaborate dive station and recompression chamber and hot water heating equipment. In addition, dive equipment may require cold climate modification. Because of logistical considerations, scuba is used in most ice diving situations. However, SSDS may be required because of prolonged bottom times, depth requirements, and complex communications between topside and diver. When diving in cold water that is not ice covered, logistic and equipment support requirements are reduced; however, very cold water poses many of the same dangers to the surface-supplied diver as ice diving.

Advantages and Disadvantages of SSDS.
                   

 The advantages of using SSDS are:

• Configuration supports bottom-oriented work.

• Hot water suit and variable volume dry suit offer diver maximum thermal and
  environmental protection.

• Communications cable offers audio communications.

• Gas supply allows maximum duration to the maximum depth limits of diving.

 The disadvantages of using SSDS are:

• Manifold/panel may freeze up.

• Low-pressure compressors do not efficiently remove moisture from the air which may freeze and clog filters or fracture equipment. This is more likely when the water is very cold and the air is warm. Banks of high-pressure cylinders may have to be used.

• Buildup of air or gas under the ice cover could weaken and fracture thin ice, endangering tenders, other topside personnel, and equipment.

• Movement of ice could foul or drag diver’s umbilical.

• Battery life of electronic gear is severely reduced.

• Carbon dioxide removal recirculator components may have to be heated.

• Decompression under extreme cold conditions may be dangerous due to water
  temperature, ice movement, etc.

Effect of Ice Conditions on SSDS. Ice conditions can prevent or severely affect surface-supplied diving. In general, the ice field must be stationary and thick enough to support the dive station and support equipment. If the dive must be accomplished through an ice floe, the floe must be firmly attached to land or a stable ice field. Severe ice conditions seriously restrict or prohibit surface-supplied diving through the ice (i.e., moving, unstable ice or pack ice and bergs, and deep or jagged pressure ridges could obstruct or trap the diver). In cases where a diver is deployed from a boat in a fixed mooring, the boat, divers, and divers’ umbilicals must not be threatened by moving ice floes.

Suit Selection. Custom wet suits designed for cold water diving, variable volume dry suits, and hot water suits have all been used effectively for diving in extremely cold water. Each has advantages and disadvantages that must be considered when planning a particular dive mission. All suits must be inspected before use to ensure they are in good condition with no seam separations or fabric cuts.

Wet Suits. Custom wet suits have the advantages of wide availability, simplicity and less danger of catastrophic failure than dry suits. Although the wet suit is not the equipment of choice, if used the following should be considered:

• The wet suit should be maintained in the best possible condition to reduce water flushing in and out of the suit.

• Wearing heavy insulating socks under the boots in a wet suit will help keep feet warm.

CAUTION     In very cold water, the wet suit is only a marginally effective thermal protective measure, and its use exposes the diver to hypothermia and restricts available bottom time. The use of alternative thermal protective equipment should be considered in these circumstances.

Variable Volume Dry Suits. Variable volume dry suits provide superior thermal protection to the surface-supplied or scuba diver in the water and on the surface. They are constructed so the entry zipper or seal and all wrist and neck seals are waterproof, keeping the interior dry. They can be inflated orally or from a lowpressure air source via an inlet valve. Air can be exhausted from the suit via a second valve, allowing excellent buoyancy control. The level of thermal protection can be varied through careful selection of the type and thickness of long underwear. However, too much underwear is bulky and can cause overheating, sweating, and subsequent chilling of the standby diver. Dry suit disadvantages are increased swimmer fatigue due to suit bulk, possible malfunction of inlet and exhaust valves, and the need for additional weights for neutral buoyancy. Furthermore, if the diver is horizontal or deployed with the head below the rest of the body, air can migrate into the suit lower extremities, causing overinflation and loss of fins and buoyancy control. A parting seam or zipper could result in a dramatic loss of buoyancy control and thermal shock. Nevertheless, because of its superior thermal protection, the dry suit is an essential component of extremely cold water diving. 

CAUTION     Prior to the use of variable volume dry suits and hot water suits in cold and ice-covered waters, divers must be trained in their use and be thoroughly familiar with the operation of these suits.

Extreme Exposure Suits/Hot Water Suits. Hot water suits provide excellent thermal protection. If their use can be supported logistically, they are an excellent choice whenever bottom times are lengthy. They are impractical for use by standby divers exposed on the surface.

A hot water system failure can be catastrophic for a diver in very cold water since the hot water is a life support system under such conditions. Hot water temperature must be carefully monitored to ensure that the water is delivered at the proper temperature. When using the hot water suit, wet suit liners must be worn. The hose on the surface must be monitored to ensure it does not melt into the ice. When not in use, the heater and hoses must be thoroughly drained and dried to prevent freezing and rupture.

Clothing. Proper planning must include protecting tenders and topside support personnel from the environment. However, bulky clothing and heavy mittens make even routine tasks difficult for topside personnel. Waterproof outer gloves and boots may also be considered. Regardless of the type of clothing selected, the clothing must be properly fitted (loosely worn), and kept clean and dry to maximize insulation. In planning operations for such conditions, reduced efficiency resulting in longer on-site time must be considered. Refer to the Polar Operations Manual for complete information on thermal protection of support personnel and equipment.

Ancillary Equipment. A detailed reconnaissance of the dive site will provide the planner with information that is helpful in deciding what ancillary equipment is required. Diving under ice will require special accessory equipment such as a line with lights for underwater navigation, ice-cutting tools, platforms, and engine protection kits.

The method of cutting the hole through the ice depends on ice thickness and availability of equipment. Normally, two or more of the following tools are used: hand ice chipper, ice handsaw, ice auger, chain saw, thermal ice cutter or blasting equipment. In addition, equipment to lift the ice block, remove the slush, and mark the hole is required. Sandbags, burlap bags, or pallets for the tenders to stand on are also needed. Ladders should be in place in case a tender falls into the hole.

If there is a possibility of surface support personnel falling through the ice, floatable work platforms, such as an inflated Zodiac boat, should be used. With such flotation equipment, the operation could be continued or safely concluded if the ice breaks up.

Gasoline and diesel engines must be cold-weather modified to prevent engine freeze-up. Vibrations of engines running on the ice can be a problem and vibration dampening platforms may be required.

Dive Site Shelter. Tent equipment including framing and flooring material may be required to construct a dive site shelter and a windbreak. Depending on the severity of the climate, remoteness of the site, and duration of the mission, shelters can range from small tents to steel sea-land vans and elaborate insulated huts transported to the site and erected from kits. Dive site shelters should have storage areas for dry items and a place for drying equipment. Benches should be provided for dressing divers, flooring should be installed for insulation, and heating and lighting should be adequate. In an extremely cold and dry climate, fire and inadequate ventilation are ever-present dangers. A carbon monoxide detection kit should be available and periodic checks made of all living and working spaces. Fire extinguishers shall be available in each shelter.