** This day in Diving History -- 01 February 1966 -- Harbor Clearance Unit ONE Established **

01 February 1966; Harbor Clearance Unit ONE established at Subic Bay, Philippines. The establishment of HCU ONE was authorized by the Secretary of the Navy to fill the need for harbor clearance of any waterway or port in Vietnam. While the idea of a harbor clearance team harkened back to successful clearance operations by various units in WWII, this new operational concept gave Navy Salvage an additional capability. The missions of HCU ONE in Vietnam would call for committing small and highly mobile teams of well qualified salvage specialists to a job rather than relying on large salvage ships. While deep heavy salvage was and is very necessary; the waterways, rivers and deltas of certain geographic areas (like Vietnam) simply won't support large vessels just as open ocean doesn't do well with small ones.

The original crew of HCU ONE consisted of a hand-picked cadre of five officers and sixty-five enlisted men. The unit's headquarters started out as a barge specifically converted to a salvage tender that was outfitted with all the shop facilities, storage, and accommodations necessary to support various salvage operations. The team would later acquire adequate medical, office and armory facilities. A typical diving team consisted of an officer and 18 enlisted men. These Divers were all a colorful and confident bunch (as would be expected) even giving their teams nicknames. For example, HCU ONE Team FIVE was originally known as Bennett's Bastards after their OIC LT John Bennett. HCU ONE Team ONE was known as Naquin's Nitwits again after the OIC LT John C. Naquin. HCU ONE grew in men and equipment during its years of existence and amassed a huge record of success. During its tenure in the Philippines, the unit was awarded two Navy Unit Commendations, a Meritorious Unit Commendation and a Vietnamese Unit Cross of Gallantry. Eventually, HCU ONE would move its homeport to Hawaii and later be renamed Mobile Diving and Salvage Unit ONE where it continues operations today. Its east coast counterpart Harbor Clearance Unit TWO would be stood up 8 months later on October 1, 1966 and will be covered in a future email.

Note: To see more HCU ONE photos and sea stories than could possibly be attached to this email check out the following website: http://www.seastory.us/hcu1/

H/Y

Probabilistic models of decompression sickness (DCS)

Probabilistic models of decompression sickness (DCS) were developed to combine the data from laboratory run decompression trials with controlled depth, time, temperature and exercise profiles with DCS as the measured outcome. The parameters of the models are found through an iterative process that search for the values that provide the best fit between the models prediction and the measured outcomes.

The US Navy's development of probabilistic decompression models starts with Dr Weathersby Paper:

Weathersby PK, Homer LD, Flynn ET. On the Likelihood of Decompression Sickness. J Appl Physiol: Respir Environ Exercise Physiol 1984; 57:815-825 Available from: http://jap.physiology.org/

The model was expanded to use the time of occurrence of the DCS outcomes as part of the fitting process:

Weathersby PK, Survanshi SS, Homer LD, Parker E, Thalmann ED. Predicting the Time of occurrence of decompression sickness. J Appl Physiol 1992; 72:1541-1548 Available from: http://jap.physiology.org/

Most of the Navy's technical reports issued out of NEDU, NMRC, and NSMRL (and other diving labs) that have been deemed to be suitable for public release (distribution statement A) are available for free download through the Rubicon Foundations website. The research that was behind the above two papers was documented in greater detail in a series of Technical Reports entitled "Statistically Based Decompression Tables" Numbered I through XII that should be easier to access. Eleven of the Statistically Based Decompression Tables" Technical reports are available from Naval Medical Research Center (NMRC) Collection on the Rubicon site: http://archive.rubicon-foundation.org/dspace/handle/123456789/3126

The links for these technical reports are:
I http://archive.rubicon-foundation.org/3402
II http://archive.rubicon-foundation.org/3403
III http://archive.rubicon-foundation.org/3404
IV http://archive.rubicon-foundation.org/3405
V http://archive.rubicon-foundation.org/3406
VI http://archive.rubicon-foundation.org/3407
VII http://archive.rubicon-foundation.org/3408
VIII http://archive.rubicon-foundation.org/3409
IX http://archive.rubicon-foundation.org/3410
X http://archive.rubicon-foundation.org/3411
XI http://archive.rubicon-foundation.org/3412
XII unable to find online at this time

An additional probabilistic decompression model that was developed at Duke University is BVM3, a bubble volume model. BVM3 changes the risk function from being a function of the gas content of the tissues, to being a function of the volume of a bubble that is created in the compartment as a result of the decompression. The shape of the resulting risk function shift the maximum instantaneous risk to later after the diver has surfaced compared to the gas content models. This was a desired feature as DCS symptoms are observed to have a latency after surfacing. The reference for BVM3 is: Gerth WA, Vann RD. Probabilistic gas and bubble dynamics models of decompression sickness occurrence in air and nitrogen-oxygen diving. Undersea Hyer Med 1997; 24(4):275-292
http://archive.rubicon-foundation.org/2258

The proceedings of the fifty-first workshop of the Undersea and Hyperbaric Medical Society summarizes the techniques behind probabilistic physiological models (including decompression sickness). The proceedings can be downloaded from:
http://archive.rubicon-foundation.org/8027

Two good overviews of the state of US Navy decompression research and the use of probabilistic decompression models are available in proceedings of recent conferences. The first presentation was given at the DAN Technical Diver Conference with a presentation aimed at Technical Divers (pg 138-158):
http://www.dan.org/FastAccess/2008TechnicalDiving.aspx
The second is found in a chapter in the "Decompression and the Deep Stops Workshop Proceedings" June 24-25th, 2008 Undersea and Hyperbaric Medical Society (pg 165-185) which includes the documentation of a dive trial conducted to attempt to differentiate between the two leading probabilistic models.
http://underseaandh960.corecommerce.com/ALL-PUBLICATIONS/Decompression-and-the-Deep-Stop-Workshop-Proceedings-p13.html

** This Day in Diving History -- November 21, 1891 -- Edward Ellsberg born **

"It never pays to quit until you're dead."......Edward Ellsberg

NAVY ACADEMY
Ned Ellsberg was born on November 21, 1891 in Colorado and decided at a young age that he wanted to become a Naval Officer. He was not a large man physically; in fact he barely met the height and weight requirements for admission to the Naval Academy. He even went as far as changing his name, Ned, to Edward as he thought it would be more befitting a naval officer. Despite his diminutiveness, he won two medals in fencing, wrote two prize essays, and won top honors in seamanship and navigation. Although he was the top student in ordinance, two gunnery awards went to rival classmates, the predominant theory being that those prizes were diverted deliberately, lest Ellsberg run off with every honor for the Class of 1914. Ellsberg would graduate from Annapolis in 1914, at the head of his class academically but low in "military efficiency".

EARLY CAREER
Following his initial assignment aboard the battleship Texas, he was reassigned to the Brooklyn Navy Yard during WWI. There he would excel in the field of engineering and although highly encouraged to remain a line officer, decided to transfer into Naval Engineering and Construction. His first two commands serving in his new role would be at the Boston and New York Navy Yards. Here he would prove to be an active, take-charge officer who did not avoid confrontation or controversy when he knew he was right.

S-51
Ellsberg's first public success and introduction to Navy Salvage would occur in September 1925 when the submarine USS S-51 (SS 162) sank after being struck by the steamer City of Rome, losing all but three of her sailors. At the time, the Navy had little to no deep-water salvage capability and few Navy Divers. Despite this, Ellsberg convinced Navy leadership that he could raise the S-51 with existing personnel and equipment. After great public outcry, the Navy began to realize that it needed to have the capability to salvage its own; vice relying solely on contractors. The successful salvage of S-51 would take 10 months during which Ellsberg and the salvage team battled against inadequate resources, a shortage of experienced deep-sea divers, primitive equipment, and uncooperative weather. In the process they would develop such salvage items as pontoons, underwater cutting torches and jetting nozzles. Ellsberg would even start an on site school to train more divers, including himself, thereby becoming the first Construction Corps officer to qualify as a Deep-Sea Diver. In the words of Ellsberg:

"If I was going to control the diving operation on the bottom of the sea, the bottom of the sea was where I belonged."

This job would be the basis for his first book, On the Bottom, about the salvage of the S-51. It made him a popular public figure. This was unpopular with the Navy however who stated that he received too much public attention and was too outspoken. In 1926, he was denied a meritorious promotion and was told that he would have to wait another eight years for reconsideration. A frustrated Ellsberg gave his resignation and started work for the Tide Water Oil Company.

S-4
Ellsberg had hardly settled in his civilian job when in December 1927 the submarine S-4 was rammed off Cape Cod. Immediately, he was brought back into the Navy and rushed to the scene. The nation was horrified as six trapped men tapped their final messages on the steel hull, while Navy rescue ships tossed helplessly, prevented by storms from sending divers down. The Navy had shown once again that it had no means of rescue for downed submariners. S-4 was salvaged and brought to dry dock six months after she sank. The boat was then stripped and towed to Key West to be used as a platform to examine possibilities for submarine rescue and to practice salvage techniques. This platform would prove key in the development of the McCann Rescue Chamber and Momsen Lung. Ellsberg continued to warn that complacency and political penny-pinching were making further submarine disasters inevitable. He wrote a detailed report that served as a bible for future submarine salvage operations and revealed that the Navy's Salvage organization was simply inadequate. Again, him speaking with such candor was unpopular with Navy leadership.

MASSAWA/ORAN
In 1942 Ellsberg was sent to Massawa, Ethiopia, with the responsibility for clearing the port and returning the dry-dock and ship repair facilities to service. Massawa was a critically important regional repair facility for Allied Forces in the European theater during WWII. When compared to the conditions of the S-51 salvage, the situation in Massawa was almost beyond belief. The Italians had sabotaged/destroyed facilities and sunk ships as they exited the port prior to Allied capture. One of Massawa's key dry docks had been declared totally unsalvageable - Ellsberg had her afloat only nine days after his arrival. In eight months his crew would re-float four cargo ships, another dry dock, and a floating crane; refurbished more than 80 supply ships; and repaired three British cruisers. The press hailed his achievements as "the Miracle of Massawa."

Ellsberg went without a break from Massawa to become General Eisenhower's salvage officer for North Africa. He was tasked with clearing the blocked and sabotaged port of Oran, Algeria. Here he encountered many of the same problems of supply, equipment and personnel that he had experienced in Massawa. Ellsberg's team worked frenetically clearing harbors and salvaging torpedoed ships. His successes was again great but the physical strain was too much for a man in his fifties. Ellsberg was hospitalized and sent home in February 1943 after being diagnosed with incipient heart failure - it would take more than heart failure to stop him however.

NORMANDY
In 1944 he was again sent to Europe and was instrumental in preparing the artificial (Mulberry) harbors that helped make the Normandy landings a success. Sent to England to advise on preparations for the D-Day landings, he found that planners had not realized the scale of the problem or the resources required for deploying and setting up a mobile harbor in a wartime environment. He guided planners in recognizing and addressing what was needed to pump out and refloat over a hundred caissons in a matter of a few days -- without which the whole artificial port concept would have been a failure. Ellsberg rode one of the caissons to Normandy and helped unsnarl wrecked landing craft and vehicles on the beach in the wake of D-Day. When a storm two weeks later temporarily crippled the flow of supplies, he was called back to once again assess the damage at Omaha Beach. Ordered home in September 1944, he reported to Cleveland, Ohio, as Supervisor of Shipbuilding for the Lake Erie area. Fatigue had once again caught up with him, and ship construction was winding down, so Ellsberg asked to be relieved from active duty. On 3 April 1945 he returned to civilian life - permanently this time. He passed away in 1983 (age 91), having brought Navy Salvage leaps and bounds both in the minds of the Navy and civilians alike and attained the rank of rear admiral in doing so.

Although he achieved high rank and had scores of medals on his chest; when asked about his biggest military reward he would recall a comment he received from Deep-Sea Diver Francis Smith. At the end of the S-51 operation, Smith grabbed Ellsberg's hand and stated simply: "There isn't one of that bunch of divers, Mr. Ellsberg, who wouldn't go to hell for you!"

ELLSBERG the AUTHOR
Of all Ellsberg's talents and contributions to Navy Diving, one of his biggest was that of author. In the late 1920s Ellsberg began a long and distinguished career as a writer that showcased Diving and Salvage. His first book was titled "On the Bottom" (published in 1929); an account of the salvage of S-51, it became a best-seller. A subsequent book, Pigboats, published in 1931, was made into the movie Hell Below by MGM studios. He would become one of the most prolific authors ever to graduate from the U.S. Naval Academy, his 17 books included several award winners. His stories appeared in popular magazines throughout the 1930s and 1940s, introducing many a young reader to the adventures of the deep.

Website: http://www.edwardellsberg.com/

Reading: To many books/articles to list on this email. My personal favorite is "On the Bottom" but you can't go wrong with any of them. To see a list of all his books and publications, see http://www.edwardellsberg.com/pub.htm

H/Y

** Diving History -- Torpedo Town U.S.A.....Whales.....and Sheats (Part II) **

** Diving History -- Torpedo Town U.S.A.....Whales.....and Sheats (Part II) **

ROBERT SHEATS
Master Diver Robert (Bob) Sheats is one of many outstanding Navy Divers who have served at the Keyport Locker. He had many nicknames bestowed upon him during and after his career including "Master of the Master Divers". While this email showcases a few of his career highlights capturing everything he did would be impossible - the email would be pages upon pages in length. I had the opportunity recently to view his service record from the Navy Archives. To say that this man had an impressive career would be an understatement to say the least. The following outline merely three of his accomplishments.

POW
Master Diver Sheats enlisted in the Navy in 1935, qualified Second Class Diver in 1937 and within a few years became a First Class Diver. It was while serving aboard USS CANOPUS (AS-34) that he found himself in the middle of the Battle of Bataan (WWII -- Philippines). CANOPUS was pierside during one stage of the battle and was badly damaged by Japanese planes during one of the many bombing runs. Damage sustained prevented her from being able to get underway. Because CANOPUS was now a "sitting duck", her crew was forced to take refuge and fighting positions in the surrounding jungle - Sheats was placed in charge of a group of the crew now in defensive positions. Although they held out for quite a few weeks, eventually they were overrun and captured by the Japanese Imperial Army on May 6, 1942. Sheats wrote that while he had no desire to allow for his capture, he did so to preserve the lives of the men under him. Almost immediately he regretted it; due to the intolerable and brutal conditions WWII POWs faced when captured by the Japanese Army.

After being captured the team of Navy Divers (Sheats, along with 8 other Navy Divers), was forced at gunpoint to first build a diving air system (from scrap CANOPUS and submarine parts) and then dive for silver then worth over $8 million in 1942. This silver had been dumped overboard by a Navy ship in 120 feet of water when Japanese capture of the vessel was inevitable. The Japanese used the US Divers because they were the only ones that could build a diving system and had any knowledge of decompression procedures. The fact that the divers didn't have actual tables and was doing it based solely from memory was of no consequence to the Japanese; if the divers died they were only prisoners in their eyes. The silver was quickly found by the divers and was concentrated in one location. Sheats was smart enough to know that if the divers quickly recovered all of it (which they easily could have done), the Japanese would have no more use for them and would likely kill them all. He instructed the other divers to only recover small sums at a time - enough to make the guards demand more, but not so much that the well would "run dry". He also did this so he and his men would not be making large contributions to the Japanese war machine. All this occurred while he and his divers were suffering from starvation, dysentery and multiple injuries under the worst conditions imaginable. Additionally, Sheats and his men survived the Bataan death march, hell ship transport to Japan and forced slave labor in a Japanese mine until rescued after the Japanese surrendered.

His actions in keeping his men alive and focused unquestionably saved them until their eventual release on September 13, 1945 (3 years, 4+ months later). After his release he returned to duty as a Navy Diver without hesitation and would go on to achieve the qualification of Master Diver.

Years after he retired; the binder that the group of Navy Divers had used to hand write the design and compute gas formulas in building the makeshift dive system from scrap parts was found and reviewed. It also contained makeshift dive logs from the entire Japanese silver recovery operation. There were over 10 pages of formulas, all drawn from memory using hand jammed math - all without a single error.

SEALAB I
In 1964, Master Diver Bob Sheats was selected from across the fleet to serve as the Master Diver for SEALAB I. SeaLab I was a bottom habitat, saturation diving experiment whose purpose was to evaluate human ability to work under the water at moderate depths for prolonged periods. It involved four divers who remained under pressure for 11 days at 195 ft off the coast of Bermuda. The mission was a total success and conclusively demonstrated the feasibility of open-sea saturation diving. This success would not have been possible where it not for Master Diver Sheats working side by side with "Pappa Topside" Captain George F. Bond. Its success would not only prove open ocean saturation diving, but would set the stage for SeaLab II.

SEALAB II
One year later Master Diver Sheats would be involved yet again in an even bigger and much more complex saturation diving mission. SEALAB II also known as the "Tilton Hilton" (because of the slope of its landing sight) would occur at a depth of 205 ft off the coast of LaJolla, CA and last for 30 days. Because of its complexity and length compared to SEALAB I, three teams would be used with Master Diver Sheats serving as team leader for one of them. Whereas SEALAB I tested and proved the concept of saturation diving, SEALAB II provided evidence that useful work could be done. The Navy conducted physiological and psychological studies to determine man's effectiveness underwater for an extended period and conducted many operational tests.

Much was learned about working in the ocean and contributions were made to a large number of undersea science and engineering disciplines. SEALAB II was no doubt a success and represented another large step forward in enabling human beings to live and work in a hostile environment. This program ultimately even had a huge impact on the global economy. The SEALAB program provided the commercial diving industry with its most important tool in the exploitation of offshore oil and gas reservoirs: the ability to dive deep and stay there for extended periods of time. In the process, the Navy medical community extracted a wealth of physiological data from their human subjects.

TMCM(MDV) Robert (Bob) Sheats would retire from active duty after thirty years of service on July 1, 1966 having accomplished in one career what most could not over the course of 4 lifetimes. Master Diver Sheats last eval write up that his record found in his record reads as follows:

"SHEATS, Robert Carlton, TMCM, U.S. NAVTORPSTA Keyport, WA.

"SHEATS has a long and varied career in diving with a well rounded background which he puts to use in most cases of diving. This aids in completing diving jobs in minimum times. His long career has made him set in his ways and sometimes his methods of sternness may be construed as belligerency towards his superiors but it is believed that his interests are for the good of the diving navy. During the last three months SHEATS has been assigned TAD with SEALAB II and received the Legion of Merit for his accomplishments. He also received special commendations from the Project Chief and the Navy Commendation Medal for SEALAB I. Because of SHEATS's long career his is extremely effective in all phases of diving and is capable of leading any team of divers on any assignment. He is demanding but gets the most out of his men."

Bob Sheats would continue to serve as a consultant in the Washington State area until he passed on March 9, 1995. His family still lives in the area.

Note: To read more about Master Diver Sheats POW experience, check out "One man's war: Diving as a guest of the Emperor, 1942" by Robert Sheats. I would personally call this required reading for all Navy Divers.

Attachments: Apologize for the small size of some of them. It seems Master Diver Sheats didn't exactly seek out cameras to get his photo taken. :)

H/Y

** Diving History -- Torpedo Town U.S.A.....Whales.....and Sheats (Part I) **

TORPEDO TOWN, U.S.A.

Navy Diving traces its roots back to the late 1800s as a collateral duty for Gunners Mates. This was mostly to support the recovery and development/testing of a new weapon of naval warfare known as the torpedo. Back then divers were simply instructed in things like how to dress out and hand crank an air pump as the program was in its infancy (any sort of diving science didn't exist). In these very early years of development the Navy's diving community mirrored that of the torpedo in many ways. This article will discuss a bit about both with focus on the Keyport, WA area. If you have ever been involved in diving in any way, shape or form and get the opportunity to visit this area; you will find some of the richest diving history out there - even if you were to exclude the undersea museum.

In the late 1800s the Navy was developing a weapon that would revolutionize warfare called the torpedo (then called a mine). As with any warfare device, it required extensive development and testing. Testing would be conducted at a controlled underwater range and test torpedoes would need to be recovered to see what went right and wrong with them; this signaled the Navy's first need for a diver. The Navy's first torpedo range was established in Newport, Rhode Island in late 1869. Soon there after, the Navy established its first diving school under Chief Gunners Mate Jacob Anderson to recover torpedoes in 1882. At the turn of the century, high demand for the torpedo and difficulty in getting them to the west coast showed need for a west coast torpedo station. In 1908 a special task force of officers was sent to the west coast to scout for a clear water site that had sandy bottoms, little tide and depths between 30 and 60 feet. This task force would search areas such as San Diego, Los Angeles, Tacoma and British Columbia. In 1913 the Navy would settle on a little populated peninsula that had recently been named Keyport, WA. The few Keyport land owners that existed did not want to sell to the Navy - for any price. Once condemnation proceedings were complete; each land owner was given a share of a $60,850 pot of money. The Pacific Coast Torpedo Station (PCTS) would be officially commissioned on November 11, 1914 although the base remained to be built. Building #1 would be completed in 1916 and base construction would quickly move forward from there.

The sixth building to be constructed was the base chapel but would not remain as such for long; it would be converted to the Diving Locker after a few years - no I'm not kidding. This coupled with a chamber room addition is what you see today. In 1919 Keyport would hold its first diving class (8-9 enlisted) under Chief Mickey Nolan. Again, in these early years of diving there were no safety procedures like we have today. It was common practice for divers to complete their job, fully inflate their suit and jet to the surface. This stopped after a few years of "strange unknown sickness" occurring in divers (likely the bends or a gas embolism). Initially there was no chamber in Keyport with the closest one being in British Columbia. Because time was at a premium to treat diving illness, those afflicted would usually be suited up and lowered into the deepest possible area, usually off Seattle (200fsw). The Keyport area would not have a chamber until one was built for them in the 1930s. This chamber was constructed at the Norfolk Navy Yard and is said to contain over 600 rivets - easy to believe for its sheer size (it has been nicknamed "The Whale"). The truly unique thing about this chamber is it is still in use today making it far and away the oldest certified recompression facility in the military and certainly one of the oldest active in the world. Testing and retrieving torpedoes was very different in the 1940s than it is today. Back then, torpedo speed and depth measurements were made by a visual system consisting of barges set at each 1000 yard range. Observers on the barges would time the torpedoes as they passed to access speed. Originally, a rough visual estimate was used to determine the torpedoes depth and eventual recovery location. Later depth was determined with the use of nets placed on the range; the hole the torpedo made as they passed through would show its depth for a given distance. Recovery location was solved by placing smoke pots in the torpedo. When it sank, the smoke pot would send up a stream of bubbles to the surface making location much easier for Navy Divers.

Part II of this article will focus on one of the many outstanding Navy Divers who served many years at the Keyport Dive Locker - TMCM(MDV) Robert (Bob) Sheats. His career is as impressive and varied as any in Navy history. Any write-up that showcases the history of the Keyport Diving program would simply be incomplete without including him. Below is a hyperlink that has a great detailed write-up about the development of what would be nicknamed "Torpedo Town, U.S.A." The first hyperlink is Chapter 6 which showcases its diving program - you will see a few old black and whites that include a short write up about Master Diver Sheats -- call it a sneak preview. The second hyperlink contains all chapters of the article.

http://www.hnsa.org/doc/torpedotown/chap6.htm

http://www.hnsa.org/doc/torpedotown/index.htm

Note: Earlier in this article, the Naval Undersea Museum (located at the Keyport Navy Base) was mentioned. If you are ever in the area, it is not to be missed. It contains diving displays such as the Trieste, the end bell of SEALAB II, diving equipment from its inception to present, torpedo and submarine exhibits to name just a few. Below is a hyperlink to the Undersea Museums website.

http://www.navalunderseamuseum.org/

H/Y

** Diving History -- John Scott Haldane "Father of Modern Decompression"....and a bunch of other stuff **

** Diving History -- John Scott Haldane "Father of Modern Decompression".....and a bunch of other stuff **

STAGED DECOMPRESSION
In 1905 shortly after the publication of the first dive manual, British admiralty adopted decompression procedures to depths of up to 180fsw based on British Professor John Scott Haldane's staged decompression theory. Haldane's staged decompression model had a diver leave bottom at a relatively fast rate followed by decompression stops at shallower depths. This was in sharp contrast to continuous-ascent (liner) decompression procedures developed by French physiologist Paul Bert that was being used at that time. Bert's liner decompression model usually recommended a slow but continuous ascent in the area of 3 feet per minute. The problem with liner decompression vs. staged is the very slow/continuous ascent rate which allows the diver to still on-gas while at the deeper depths. While liner decompression works well for saturation type diving (because you cannot possibly on-gas anymore......you are saturated), it posed serious problems for non-saturation type diving.

ACCEPTANCE BY THE U.S.
The U.S. was slow to adopt Professor Haldane's stage decompression procedure, but had great interest. In 1912, George D. Stillson set up a program to test Haldane's diving tables and methods of stage decompression in the Long Island Sound. Prior to these tests, Navy Divers rarely went deeper than 60 fsw. Throughout a three-year period, first diving in tanks ashore and then in open water from the USS WALKE (DD 34), Navy Divers went progressively deeper, eventually reaching 274 fsw (all on air). Before this the believed safe diving limit was 120 feet but these experiments pushed that limit to around 200 feet. Mixed gas diving would not be discovered for another 27 years but would push this depth limitation well beyond that of air.

ASCENT RATES
Haldane's original staged decompression model recommended ascent rates between 5 and 30 feet per minute dependant upon depth. This was later modified to a rate of 25fpm which remained in effect from 1920-1957. Then in 1958, while revising the U.S. Navy Diving Manual, this rate of ascent came under review. Commander Fane of the U.S. Navy West Coast Underwater Demolition Team wanted rates for his frogmen of 100 feet per minute or faster. The hardhat divers, on the other hand, considered this impractical for the heavily suited divers who were used to coming up a line slowly (usually 10 feet per minute). Thus, a compromise was reached at 60 feet per minute, which was also a convenient 1 foot per second for time/record keeping. This 60 feet per minute rate lasted in the Navy from 1957 until 1993, based on this purely empirical decision, with many recreational diving tables and even early computers following suit. In recent years the ascent rate has been slowed to 30 feet per minute as research has shown this rate helped to better guard against illnesses associated with diving such as decompression sickness and gas embolism...it seems Mr. Haldane had it pretty close to start with.

Haldane's basic staged decompression model formed the basis for what all divers (military and civilian) use world wide for non-saturation type diving. Bert's liner decompression procedure became and remains the basis for saturation type diving decompression.

A few other notable FAQ about John Scott Haldane:

1. He was heavily involved in experiments involving the effects of certain gases on the body. One of these gases; Carbon Monoxide affected not only divers but miners and other workers. He was the first to research the effects of CO on the body by breathing it in himself until it saturated his blood, nearly costing him his life. "At the end I could hardly stand and could not walk alone without falling down" he noted. His research revealed the mechanics behind CO poisoning which became known and "the Haldane effect".

2. During the First World War (1914-18) Haldane was asked to identify the type of gas that the Germans had used in the first gas attack of the war. Haldane found it was chlorine. In order to protect the soldiers, Haldane designed the first gas masks, which proved better than the urine-soaked handkerchiefs that the soldiers had used at first. Haldane also demonstrated the value of oxygen in treating soldiers when they were gassed.

3. He introduced the use of small animals for miners to detect dangerous levels poison gases underground, using either mice or canaries. The reason for this (aside from their portability) was that they have a faster metabolism. This faster metabolism causes them to show symptoms of poisoning before gas levels became critical for workers, giving an early warning sign. The use of canaries was used until 1986 when the method was replaced by the electronic gas detector.

4. Haldane led an expedition to Pikes Peak in 1913 to examine the effects of low atmospheric pressure on respiration. His work here also revealed that decompression sickness was not limited only to divers and miners. He also discovered that the respiratory reflex is triggered by an excess of carbon dioxide in the blood rather than a lack of oxygen.

5. Like his experiments involving Carbon Monoxide, Haldane would routinely experiment with toxic and non-toxic gases on his own body. Despite all the benefits these experiments would yield, years of doing them would eventually take its toll on his lungs. John S. Haldane would die of Pneumonia in 1936 and is still remembered as the father of modern decompression theory.

Note: To learn more about John Scott Haldane and his work check out "Suffer and Survive: The Extreme Life of JS Haldane" by Martin Goodman.

H/Y

** This Day in Diving History -- 15 October 2001 -- Diving operations begin on the Ehime Maru **

February 9, 2001 -- 13:43......about 9 nautical miles off the south coast of Oahu, Hawaii; while conducting an emergency surfacing maneuver, the USS GREENVILLE (SSN-772) collided with the Ehime Maru Japanese fishing vessel. This was part of a demonstration for some civilian visitors, onboard USS GREENVILLE. As the submarine surfaced, it struck Ehime Maru, slicing her hull wide open from starboard to port. Within minutes of the collision, Ehime Maru quickly sank and hit the bottom at 2,000 fsw. A total of 35 people were on board Ehime Maru; 20 crewmembers, 13 students and two teachers. Coast Guard vessels quickly responded and rescued 26 crewmembers. These crewmembers were taken to Oahu for immediate medical treatment, but the remaining nine crewmembers remained missing.
On 16 February 2001, the Supervisor of Salvage and Diving (SUPSALV) and Submarine Development Squadron 5 (SUBDEVRON 5), using the Scorpio remotely piloted underwater vehicle (ROV), located Ehime Maru in 2,000 feet of water. After assessing the technical feasibility and environmental impact of raising Ehime Maru from the ocean bottom, the U.S. government decided to proceed with its recovery. The decision was made not to raise Ehime Maru all the way to the surface but to lift and carry it underwater to a shallow location (115 ft) one mile away from Oahu. Once there, Navy Divers could enter the ship, on 15 October 2001 they did just that. Divers were tasked with five specific mission objectives:
1. Recovery of the 9 mission crewmembers
2. Collection of personal effects

3. Recovery of unique shipboard items
4. Performing hazardous liquids and material removal
5. Rigging the ship for movement to the final relocation site after 1-4 was complete

In order to accomplish this volume of work in a timely manner, divers ran two deep sea dive stations simultaneously. Inside the ship there was sharp metal, destroyed bulkheads, fuel, wire and debris fouling any sort of passage. Despite this and low-to zero visibility, divers located and recovered eight of the nine missing crew members. In the course of searching four of her decks, they also cleared 120 compartments recovering over 2,500 personal and unique shipboard items. A technique called a "hot-tap" was used to drain the ships fuel tanks completely of 45,000 gallons of lube oil and diesel fuel. This prevented any loss of hazardous pollutants to the environment. An estimated two tons of debris would be removed by divers in order to rig the Ehime Maru prior to moving her back out to her final deepwater resting place. After the recovery was complete, on 25 November, Ehime Maru was lifted, towed back out to sea, suspended about 90 feet below the towing barge, and scuttled in over 6,000 feet of water 12 nautical miles south of Oahu where she rests today.
All in all Navy Divers conducted over 650 dives during the course of 29 days. This operation not only gave closure to families and recovered sensitive items but it also only helped avoid future ecological damage due to the fuel. The use of military assets to complete this also went a very long way in public support and U.S./Japanese relations in that it showed genuine concern vice simply throwing money at the problem.

H/Y