Like many divers, Mike Lynch anticipated his venture into
the great blue beyond following his open water certification would be peaceful,
serene and quiet.
Well, two outta three ain’t bad.
While scuba diving is peaceful and serene, it’s not always
quiet, thanks to the never-ending pulse of expelled breaths and the resulting
bubbles escaping past the diver’s ear. Breathing air in from a pressurized tank
and expelling used air into the water column has always been a part of diving
in general and scuba diving in particular.
But for serious divers, and those with both the skills and
the disposable income, rebreathers offer a panacea of underwater enjoyment.
In the past year, Lynch, a diving friend of mine who works
with Bruno’s Dive Shop in Clinton Township and Titan Dive Group, became a
certified rebreather diver, and the stories he has to tell are amazing.
Four-hour cave dives with an average depth of 120 feet and such quiet
tranquility that he can hear the water moving around in the cave system and
rocks cracking on each other as they roll around in moving water. Fish swimming
right up to his mask to see their reflection because they aren’t scared away by
expelled bubbles.
“It brings you into a whole new world of diving,” Lynch
said.
Lynch, repping Titan at the Great Lakes Shipwreck Festival
in March, gave me an up-close and personal explanation of how the rebreather
works.
In the most basic terms, the rebreather uses two tanks, one
containing pure oxygen, and the other containing regular air used as “filler.”
Each tank is smaller than a traditional scuba tank. With each breath, the used
air is recirculated using a scrubber to remove the carbon dioxide, and
additional oxygen is added to the “filler” air. The system is constantly
evaluating the user’s gas needs based not only upon their own metabolic rate,
but also things like the dive depth. According to Lynch, it creates a perfect
nitrox mix for the entire dive.
It is a much, much more efficient way to use gas, since it
is all recycled and reused. A typical “open circuit” scuba unit, with expelled
bubbles, wastes a significant amount of oxygen. In a typical breath, only about
4-5 percent of the oxygen is used, and the rest is expelled into the water. With
a rebreather, that unused oxygen is pushed back in the system and mixed with
the filler air and oxygen. Lynch said that during his four-hour cave dive at an
average of 120 feet, he only used eight cubic feet of oxygen.
While the idea and the concept of rebreathers have been
around for more than 200 years, mass-produced recreational rebreathers have
only been around for a little more than 20 years. The last 10-15 years have
seen significant technological advancement.
Nevertheless, cost remains an issue. Lynch said a diver
looking to get into rebreather technology can expect to spend about $10,000 for
the equipment, the training and the gas to get started.
In the video above is my interview with Mike Lynch and our discussion about rebreathers.
Michigan State Police Sgt. Bill House admits he has seen a
lot and “been in a lot of bad places” in his 13 years as a member of the
force’s underwater rescue and recovery unit.
But one incident still gets to him and chokes him up nearly
three years after it occurred: That is the case of a Cessna 206 that crashed in
Lake Michigan about four miles off the coast of Ludington on the morning of
July 23, 2010. The crash killed four of the five passengers. But it was the way
that two of the victims were killed that House acknowledges bothers him to this
day.
“I think of it now and the thought of them and what went on,
yeah, it still bothers me. I can still see their faces as clear as the day it
happened,” House said.
The tragic story began on July 23, 2010, when pilot Jerry
Freed, co-pilot Earl Davidson, medical doctor James Hall, cancer patient Donald
Pavlik, who was superintendent of the Alma Public Schools, and his wife Irene
set out on a flight from Ludington to the Mayo Clinic in Rochester, Minn.,
where Pavlik was to receive cancer treatment. The aircraft developed engine
trouble, eventually determined to be a faulty fuel filter. The pilot turned
around in the hopes of making it back to Ludington.
They never made it.
The aircraft crashed into the lake that morning. While
attempting to land the plane in the lake, the pilot lowered the flaps to flare
the plane out. The Cessna hit the water, the engine was ripped off, and the
fuselage flipped upside down. The pilots and the doctor, who were all sitting
in the front seat, got out. Pavlik and his wife remained inside. Because the flaps were locked into their
extended position, blocking the rear door, they were prevented from opening it.
The flaps couldn’t be moved because the engine was ripped off the plane.
“They were basically trapped in the plane,” House said.
Six days later, Sgt. House and his dive team’s side-scan
sonar s made contact with the plane, finding it in 173 feet of water, about
three to four miles from the shore between Big Sable Point and Ludington harbor.
The Pavliks were still in the back seat -- Don Pavlik still strapped in his
seat belt, Irene Pavik resting on his lap.
“It looked like he was hugging her. And it looked like she
was trying to get the door open,” House said, his voice choking at the memory.
House and his dive team were actually fairly close to the
accident scene when the plane went down. Normally based in Coldwater, House and
other rescue team divers were training in Rodgers City when they got the call
and immediately headed toward Ludington. They gathered information from the ELT
(emergency locator transmitter) that was activated when the plane hit water.
Within six hours of the plane going down, the dive team was on the water,
setting up a square-mile perimeter grid around the beacon and began side-scan
sonar searching. The search came up empty.
The team headed back to shore, talked to a charter boat
captain who had seen the plane go down, looked at the FAA flight path that had
been recorded prior to the plane dropping below radar and received information
from the pilot, who had been picked up by a nearby boat. The team went back out
and set up a two-square-mile grid with two crews working 24-hour shifts in an
attempt to locate the aircraft. In addition to the difficult environment, the
search was hampered by the sonar equipment becoming tangled in commercial
fishing nets.
Finally, in the early evening hours of July 29, the crew
found the plane upright on the bottom of the lake and the engine nearby. The
first recovery dive took place at 7:20 p.m. That’s when divers found the
Pavlik’s bodies still seated inside the plane and the reason why they couldn’t
open the rear door.The following
morning, the dive team cut the flap actuator rod that held the flaps in the
open position and recovered Irene Pavlik. The resulting silt from removing Mrs.
Pavlik left zero visibility. That, combined with floating luggage, entangled
medical equipment, the width of the diver’s double tanks and the narrowness of
the doorway made it impossible to remove Mr. Pavlik. He was recovered later
that day.
On July 31, Dr. James Hall was recovered nearby the plane,
and on Aug. 1, Earl Davidson’s body was recovered, also near the plane.
Presumably, both men drowned sometime after exiting the plane. Only the pilot
survived the accident.
It was the deepest recovery dive since the inception of the
Michigan State Police underwater rescue unit in 1957, and House’s deepest
personal dive. It was also fraught with difficulty, dealing with the
environment, the lack of visibility, the wind and the waves and its location so
far offshore.
But as is the nature of his job, each day has its rewards
and its heartbreak.
“It’s one of those bittersweet things. I love diving. I love
state police diving and the recovery work because somebody’s got to do it,”
House said. “I’ve been told ‘this is a gravesite, shouldn’t you leave it
alone?’ But people want their loved ones back, and so that’s part of it you
feel good about. You are excited when you got them out of the plane, but it’s
also very tragic.”
Dr. John O’Shea has a bottle of Scotch whiskey on the desk
in his office, a gift from a colleague. The problem is, he’s not allowed to
open it.
Not allowed, that is, until the colleague who gave it to him
gives him the OK.
Since the summer of 2009, O’Shea, the curator of Great Lakes
Archaeology in the Museum of Anthropology at the University of Michigan, has
led a study of the Alpena-Amberley ridge, a 72-square mile post-Ice Age land
bridge that once connected what is now Michigan’s northeastern Lower Peninsula
near Alpena, with Point Clark in southwest Ontario about 9,000 years ago.
Today, that ridge sits 100 feet below the water line at the bottom of Lake
Huron.
In the 3-1/2 years his team has been studying the area, it
has found compelling evidence that both caribou and mastodon used the ridge as
a semi-annual migration path, and that humans, categorized as Paleoindian and
Early Archaic hunters, devised ways to hunt and kill the animals on the ridge.
But a skeptical colleague, that’s right, the one bearing the gift of Scotch,
won’t be convinced until the group finds an arrowhead or a spearpoint, thereby
in his mind confirming O’Shea’s theory.
“I want to be out there until I find that spearhead and I
can open that bottle of Lagavulin,” O’Shea said with a laugh. “We’ve convinced
a lot of skeptical critics that this probably is what was going on. The dates
(carbon dating of wood poles found to be about 9,000 years old) are coming in,
the simulation is working. Science is incremental, you’re always adding things
together. But the pieces are falling together in a really nice way. So I’m very
enthusiastic about this summer’s work that we will collect even more stuff.”
O’Shea has been a frequent visitor at the annual Great Lakes
Shipwreck Festival, and once again spoke to a packed room, updating listeners
on scientific findings in 2012.
On older nautical charts, the area including the ridge is labeled as the
Six Fathom Shoal, and it once divided the Lake Huron basin into two distinct
lakes, the largest of which is called Lake Stanley. Scientists believe the
ridge exists because it is composed of limestones and dolomites, materials so
hard that even the mighty glaciers that destroyed everything their path
couldn’t cut into it.
While the ridge area includes the prehistoric Lake Stanley, Lake
Chippewa, the forerunner to Lake Michigan sat to the west. Prior to the ice
melt that eventually covered the Alpena-Amberly ridge, those two lakes did not
connect at the Straits of Mackinac like they do today.
A computer rendering of the Alpena-Amberley land ridge, a 75-square mile ridge that once connected Michigan's Lower Peninsula to southwest Ontario. The green area represents the current water line of Lake Huron.
In years past, the team had found wooden poles, perhaps used
to hang meat, that date to about 9,000 years ago. They found stone structures
probably used as hunting blinds, caches or pits and “drive lanes” made by a
linear path of rocks that would bring the animals close enough that hunters
could attack them with spears and lances.
In 2012, the team discovered additional wood samples,
potential fireplaces, charcoal, and in core samples flakeage or micro-debitage,
stone microfragments made when chipping away at stone or rock to make tools,
weapons or other implements. The microfragments are determined to be manmade
since the way they are shaped couldn’t have happened naturally. The team is
also transitioning from discovering artifacts to determining how the people of
that time period lived.
Since it was during the post-Ice Age time period, the
climate was milder than the Ice Age, but still bitterly cold with miserable
conditions along the ridge. Those "warmer" conditions were comparably pleasant
for the caribou and their thick hides. The subarctic tundra would have had
developing grass areas, intermittent marshes and a scatter of coniferous trees,
while the water’s edge would have provided various types of vegetation. The
windy conditions would have given them relief from flies that bothered them during the warmer
seasons. As for the hunters, the confined nature of the ridge would have
provided a substantial element of predictability regarding herd movement which
would have been of great value to them.
“These people probably lived in the Lower Peninsula, closer
to the middle of the modern-day lake since the lakes were so much shallower
then,” O’Shea said. “They probably only came out to the ridge to hunt. Maybe
they would come out by sled in the winter to retrieve the meat that had been
cached from the fall hunt.”
While many of the hunting blinds at the bottom of Lake Huron
are set up to attack caribou moving in both migrational directions (southeast
in the autumn to rut and northwest in the spring to calve) some are V-shaped,
giving the impression that they would work for movement in only one direction.
Based upon which direction they are facing, scientists can determine whether
they were used for fall or spring migration. In addition, some blinds are
minimal, suggesting their location didn’t work, while other blinds are more
extensive and updated, indicating they are in better locations and fortified to
allow for more hunters.
“A number of the structures are located on high ground at
the break of the crest of a hill, so that the animals coming up the hill don’t
really see (the hunters) until they are upon them,” O’Shea said. “They did
things that make a lot of sense to a modern hunter’s eye.”
As for the final smoking guns, such as large pieces of bone
or spear or arrowheads that would remove all doubt of hunting activity on the
ridge, O’Shea said large or macro bone pieces almost certainly have dissolved
over time. The microbone fragments that have been found were discovered in core
drilling samples. Larger pieces of bone would only be found in holes or caches
within the limestone.
The spear or arrowheads are still on the agenda and will
hopefully be discovered, if only so O’Shea can uncork his whiskey.
When asked
if his team has made enough discoveries to certainly prove the existence of
hunting on the ridge, his answer is one you may expect of a scientist.
“We’ve gone a long way towards ‘certainly,’ but I wouldn’t
say absolutely … yet,” he said.
This summer, O’Shea’s team has plans to look for additional
campsites, devise better means of collecting bulk sediment samples and search
for cultural debris, expand the search to natural migration choke points and
expand acoustic coverage.
This article was provided to me by James Mott
of Unified Team Diving and Sea The World Scuba Center. I met James at the Great Lakes Shipwreck
Festival in which he spoke on the topic of gas management. James shared the
concept of “rock bottom” in which divers determine when is the best time to
begin an ascent from the deepest part of the dive to allow for a safe reserve
of 500 psi when reaching the surface. Also check out the video interview I did
with James at the festival.
By James Mott
Throughout the world, divers are told again
and again to return to the boat with 300-500 psi in their tanks.
Understandably, most competent divers stretch their bottom time out as long as
they can. They smile as they show their pressure gauges to the dive
master upon surfacing and then compare gauges with other divers in order to see
who the closest one to 301psi is. Getting the most bottom time underwater
is a fun game to play with buddies and I’m not saying that divers shouldn’t use
as much of their tanks as possible. However the question becomes, “Is
this the smartest way to plan gas?” What exactly is the goal of leaving some
air in our tanks? To help a buddy in need, to keep water out of our tanks,
to inflate our BCD’s at the surface? Many divers use the 1/3’s rule, but
even this plan has numerous flaws. So where do we start? Is there a
plan that works for deep-diving technical divers and shallow-water recreational
divers alike? What is wrong with the idea of surfacing with a safe amount
of gas, like 500psi? The answer to the 500psi problem is that
being on the surface at the end of the dive with 500psi does not answer the
more important question for scuba divers, which is, “When do I have to leave
the bottom? If we have an emergency and we need to share air, “How much
air will I need to bring me and my buddy to the surface safely? This is
the question that should start all gas planning. Doing It Right (DIR) education teaches the
unified team to plan for the worst possible emergency before the dive
starts. We always ask the question, “What happens if at the worst
possible moment, the deepest part of the dive, the furthest distance from home…
my buddy runs out of air… How much gas do I need to bring both of us to the
surface without any incident?” Calculating rock bottom is easy enough to do
in your head before the dive and it is taught in all entry level DIR
courses. How long will the ascent take, multiplied by two divers, then by
the average depth and then by a consumption rate, equals rock bottom.
Rock bottom is calculated by adding
up the time it would take to ascend from a given depth. For example, from
60 feet, we would normally ascend at 30 feet/minute and have a three-minute
safety stop. This normal ascent would take us four minutes. We then
add one minute for the air-sharing emergency to take place and have a
five-minute ascent, requiring 10 minutes of total air with two divers breathing
during that 5 minute time frame. We assume we have an elevated breathing
rate of about 1 cubic foot/minute. Our average depth during the ascent is
about 30 feet or 2 ATA (atmospheric pressure one ATA is atmospheric pressure at
sea level) where we consume gas at twice the surface rate.
SCUBA Math
5 minutes X 2 divers X 1 cfm X 2 ATA
= 20 cubic feet of gas
20 cf of gas on an AL 80 is about
750 psi.
Rock Bottom for 60 FSW on an AL80 is
750 or for most gauges, 800 psi.
Rock Bottom for 100FSW on an AL 80
is 1600psi. (Math is not provided but can be, just ask.)
Once rock bottom is determined, the remainder
of the useable gas is then divided into a logical plan. Maybe it is a
drift dive on a Caribbean reef where we can use everything. Maybe we are diving
on a shipwreck in the Great Lakes and need to get back to the mooring line, or
we might be doing a penetration on this shipwreck where we will need enough gas
to get out of the wreck plus enough to get to the surface. Different
dives will require different gas plans, but rock bottom must always be
accounted for, before the gas plan is made. DIR education teaches the
unified team to plan their gas in accordance for the specific dive, so that
each diver can get the most fun possible out of their diving and still be safe. Being at depth below rock bottom is
irresponsible and will not give us enough air to safely ascend. The only
emergency underwater is running out of gas, everything else is just an
inconvenience. Once the out of gas diver is breathing again, we move from
emergency to management. Just because someone ran out of air, does not
mean that we rush to the surface, exceed safe ascent rates, skip safety/deco
stops, or anything else we know about safe diving protocols. The only
option is to remain calm, think, communicate and finish the dive. For more information about rock bottom or
other gas management options, contact me at jm@unifiedteamdiving.com or www.unifiedteamdiving.com or Sea The World Scuba Center in Farmington Hills at 248-478-6400.
