Originally published Sept. 6, 1998
For several summers in the late 1970s and early ‘80s, geologist Susan Winkler regularly got down on her knees in the low-tide mud of Knik and Turnagain arms. She dug holes and scooped up soil samples. She estimated water saturation. She noted size and direction of the mud ridges and other surface forms.
Working for the U.S. Geological Survey, Winkler wrote several technical papers about how the mud flats continually reshape themselves.
As a scientist, Winkler understands how the mud’s tiny grains of silt and sand work with one another and with the droplets of water that fill the tiny spaces between. She appreciates how ‘’unpredictable and scary’' the mud is.
She knows this in her guts, too.
Once, in the early 1980s, she was taking measurements on the Knik Arm mud a quarter-mile beyond the mouth of Eagle River. Without warning, the ground had a seizure.
‘’I had been out there walking around for four or five minutes, and all of a sudden it liquefied,’’ said Winkler, now retired and living in Colorado.
Imagine the ground being solid underfoot one minute and undulating like a water bed the next.
‘’The whole surface was rolling, and I got up immediately and jumped into the (nearby) helicopter.’’
The pilot kept the rotors turning while she was out there -- unwittingly sending a steady pulse of vibrations into the soil. Winkler said she believes those vibrations disturbed the balance between the grains of silt and their watery filling.
‘’That may have caused the liquefication,’’ she said.
‘’The particles rearrange, and the water runs out, and little channels form. That was the only time that happened, and I was out there four years.’’
Once was enough, however.
‘’I wouldn’t venture out on the mud under any circumstances,’’ Winkler said. ‘’Unless you’re an engineer and know what’s going on, it’s not a place to be.’’
Genuine dangers
Many people fear the coastal mud flats around Anchorage, just as Winkler does. Rescue authorities and tour guides religiously warn about the hazards. Guidebooks print cautions.
The dangers are genuine. In the past 37 years, two people are known to have gotten stuck in the mud and drowned when the tide came in. Many others, however, have been trapped but freed before it was too late, rescue officials said.
Because the flats’ dangers are so well publicized, all it takes to bring out rescuers, an Anchorage firefighter said, is for a passing motorist to spot people hiking on the flats at low tide.
That’s happened several times this summer, including once in early July when three young tourists were evacuated from a Turnagain Arm sandbar by a National Guard helicopter. At the time, a state trooper said the visitors had less than 30 minutes to live. It wasn’t the mud that was about to get them but the advancing tide.
Despite the known dangers -- fast, powerful flood tides and what Winkler and others see as the unpredictable nature of the mud -- people still venture onto the flats.
To some, going out on the mud flats -- whether to hike, bike or race the bore tides -- is akin to an extreme sport.
To others, walking on the flats is less dangerous than climbing mountains, kayaking swift water or hang-gliding from cliffs because of the clocklike regularity of the tides. The most extreme tidal swing in Turnagain Arm is nearly 40 feet, the second highest in North America.
‘’There are very few negative surprises that can happen out there compared with anything else,’’ said George Lukens Jr., a resident of Oceanview in South Anchorage who has been visiting the flats below his home for 27 years. ‘’Talk about skiing -- you’ve got wind conditions, snow conditions changing every day. Mountain climbing has vagaries of the weather. Go (float) down a stream -- there are different rocks and narrows.
‘’Everything in this state is risky,’’ Lukens said.
And as with other risky pursuits, Lukens and others say, those walking the mud flats must know the terrain and respect its dangers.
Winkler agrees. ‘’I have plenty of respect out there,’’ she said.
When told that Lukens and his family regularly walk about on the flats, she said: ‘’I think he’s just been lucky and he’s in an area where maybe (the mud) is older and ... more compacted. But I still would not ever recommend anybody going out there.’’
Safe to some
Lukens agrees the mud flats aren’t for everyone.
‘’It’s not a playground for the masses,’’ he said.’’It shouldn’t be the Anchorage Coastal Mud Flats Park.’’
To demonstrate the flats can be safe and pleasurable, Lukens and his 19-year-old son Matt invited two journalists for a walk on the mud below Oceanview. They were joined by two of Matt’s friends on a cloudless day in late July.
The group walked down the bluffs of Oceanview and crossed the marsh of the Anchorage Coastal Wildlife Refuge on a firm foot trail. After removing their shoes, they entered the flats, passing through a line of trees that died in the 1964 earthquake before reaching the outer flats. Those flats become submerged with every high tide.
Matt Lukens and his friends continued walking another mile and a half on a vast beach as the tide ebbed, walking so far out it seemed they might cross the Inlet.
The mud glistened wet and dark. In most places, it supported the foot like soft ground anywhere, yielding a bit with each step -- a quality that makes walking on the flats ‘’therapy for the feet,’’ Lukens said.
In slight depressions and especially in the watery bottoms of ‘’guts’' -- the gullies or ravines that can be 8 feet deep or more -- the ground was often sloppy. There, a foot might disappear immediately in brown goo up to the ankle.
Occasionally, a patch of seemingly firm mud the size of a kitchen tabletop jiggled like a huge cake of Jell-O.
Two days before this excursion, Matt Lukens, his 17-year-old brother Jonny and two of their friends achieved notoriety after they mooned National Guard aircrews flying overhead and gave flippant replies to the helicopter airmen who landed on the flats and admonished the boys.
The aborted rescue -- set in motion by a rifle-range manager and the Anchorage Fire Department -- embarrassed and angered George Lukens and his sons. Lukens concedes his boys acted immaturely. But he adamantly denies they were in any danger of being overrun by the tide or getting a leg trapped in the silty mud.
‘’The mooning thing is something no adult would even think about,’’ Lukens said. ‘’But the kids are thinking, ‘What the hell is this? We’re doing the same thing we always do.’ ‘’
Lukens estimates that he and his boys have visited the flats 500 times without incident.
‘’We know this by experience,’’ he said, ‘’just the way a farmer knows his field.
‘’We haven’t even had the mildest kind of a scare. It’s just a case of everybody using good judgment. We don’t flirt with it; we don’t push it.’’
‘’I don’t want to lay claim to knowledge of the Arm, but I know this place,’’ he said.
Despite all the visits, no one had ever called the National Guard or any other agency before, Lukens said.
Lukens’ three sons -- the third is George Lukens III, 27 -- have visited the flats since they were kids. They play Frisbee and football, slide and slosh in the mud, and swim where two 8-foot-deep guts intersect. The ‘’lake,’’ as they call it, fills with each incoming tide.
They also wade into the water on a broad, level beach beyond the ‘’lake.’’ Anchorage is not supposed to have such a beach, and the astonishing scene looks like it could be anywhere but here.
Dan Short, an Anchorage fire captain, called in the 210th Air Rescue Squadron on July 28 when the Lukens boys and their buddies were so far beyond shore that he needed binoculars to see them. He would not have called for help if he knew then what he knows today.
‘’I’m fully willing to allow people liberties to enjoy themselves,’’ Short said. ‘’If I had known the father and children had been doing that for years and knew the risk, I’d have said nothing. But how could I know that? They were a mile out.’’
Bad memories
George Lukens believes he knows why a rescue was launched for his sons: The public, he said, remains spooked by the horrible death 10 years ago of Adeana Dickison, an 18-year-old newlywed who had just moved to Eagle River.
‘’The mud flats have that dark, treacherous, savage image because of what happened (to Dickison) at Ingram Creek,’’ Lukens said.
On the morning of July 15, 1988, Dickison and her husband rode an all-terrain vehicle on the flats. They pulled a small trailer with a dredge, intending to go placer mining. Near Ingram Creek, across Turnagain Arm from Portage, they crossed a shallow, 15-foot-wide gut and got stuck.
Dickison hopped off and tried pushing as her husband gave the ATV gas.
‘’As she’s pushing, she’s pushing up on the machine, at a fairly steep angle, but then she’s also pushing her feet down into the mud,’’ said Mike Opalka, the state trooper who was the first to answer the call to help Dickison.
Opalka said that when Dickison hopped off the ATV, about 18 inches of water remained in the gully after the tide had ebbed.
Dickison sank to her knees, and the muck would not release her. Her husband freed one leg using the suction dredge, but then the dredge quit, Opalka said.
Rescuers worked for hours but failed to free her. Nor could they keep her breathing through a tube as the 40-degree water rose over her head.
‘’It had such a lasting impression on people that to this day it is such a legend,’’ said Mike Tumey, a Girdwood firefighter and one of those who tried to save Dickison.
‘’It was the worst thing in the world you could ever dream of,’’ Lukens said. ‘’The ultimate horror.’’
But Lukens sees a critical difference: Dickison died at the head of Turnagain Arm some 40 miles from his home and far from the flats he and his family know.
‘’I’ve gone all over (below Oceanview) and kind of tested the mud, especially after that incident. I did different things to see how susceptible the mud was. I never found anything that came close to it’' in terms of sinking.
Experts agree that there’s no uniformity to the mud flats.
‘’You cannot generalize that it’s all dangerous or that it’s all safe,’’ said Keith Mobley, a geotechnical engineer with a private firm in Anchorage.
No map or detailed list of the dangerous areas exists, Winkler said.
‘’The problem is that the channels shift,’’ she said. ‘’Any map you make in any given time would be different in a number of years.’’
Stuck sportsmen
One other person is known to have died like Dickison, according to authorities and newspaper files. A 33-year-old soldier, Roger Cashin, was duck hunting from a tidal channel near the Knik River 37 years ago. He got stuck in the mud and drowned on the incoming tide despite rescue efforts.
Others -- mostly hunters or anglers -- have been caught by the mud and rescued.
In 1981, duck hunter Knox ‘’Tony’' Chain ‘’stepped in a hole’' after unloading his boat in a channel near the mouth of the Knik River. ‘’I just kept sinking,’’ Chain told the Daily News 10 years ago. ‘’One leg went down and, trying to push myself up, both went down. I ended up chest deep. It seemed like it didn’t take any time at all.’’
The crew of an Air Force rescue squadron helicopter pulled Chain out of the viselike mud while the copter hovered a few feet overhead.
A year ago, fisherman Dan Dildine got caught in Ship Creek. Dildine stepped into a thigh-deep pocket of mud that held him solid. ‘’I know about the dangers. But I guess it was just the lure of the silvers,’’ he said at the time.
The Anchorage Fire Department freed Dildine with a mud tool, a long nozzle with small holes that rescuers stick into the mud beside a trapped leg. Water forced through the holes floods the mud and loosens its grip, said Capt. Ken McCoy, head of water operations for the department’s rescue company.
Because of Ship Creek’s popularity as an urban fishery, it may be the biggest mud trap around, rescuers said.
In 1996 and 1997, the Anchorage Fire Department, which includes the volunteer departments of Girdwood and Chugiak, pulled 10 people out of the mud, a department spokeswoman said.
Department records don’t show where those rescues occurred, inspector Kayle Foster said, but McCoy said most happened at Ship Creek. ‘’That’s where all the use is now,’’ he said.
In 1995 and so far this year, the department hasn’t rescued anyone from the mud, Foster said. Figures before 1995 are unavailable.
Opalka, a Girdwood trooper of 16 years, remembers seven or eight deaths ‘’attributable directly to Turnagain Arm’' during his tenure. Most of those were wind surfers or canoeists who drowned, he said. Dickison is the only one who died after getting mired in the mud.
Water is the enemy
Dickison’s foot got stuck, according to Lukens and others, for a good reason.
‘’She worked it in there,’’ Lukens said. ‘’If you picked a spot and tried to get your foot down, you might.’’
Three conditions have to be met for someone to get trapped in mud, experts say.
• The mud is water-saturated.
• Your weight and movements enable your leg to displace most of the water.
• The soil is a type that easily locks around your leg once the water is displaced.
Water, everyone agrees, is the enemy.
‘’The strength of the soil has to do with how much water is in it,’’ said Jerry Raychel, a geotechnical engineer with the Army Corps of Engineers in Anchorage. ‘’If it drains out very well, it has higher strength.’’
‘’The most dangerous parts (of the mud flats), I think, are the parts near the channels, because they have the most water and so are the most liquifiable,’’ Winkler said.
The finer the particles, the more pores available to be filled by water.
‘’Silt-sized material is highly saturable,’’ Winkler said.
The huge tides of upper Cook Inlet ‘’are constantly resaturating the sediment with water,’’ said Bob Swenson, a petroleum geologist. ‘’If it were allowed to drain, it wouldn’t be as dangerous. (The water) keeps the grains somewhat suspended.’’
Another factor affecting the strength of the soil is how tightly the particles are packed together, said Mobley, the geotechnical engineer.
‘’If you have them very tight together so the particles touch each other in a lot of places, then there’s grain-to-grain friction which will hold (the soil) together,’’ he said.
Some minerals attract water molecules better than others, Mobley said.
The problem all of these variables create for mud-flat walkers is that it is rarely possible to tell how much water is in the soil.
Some areas drain better than others. Some have more of the dangerous fine-grained silt than course-grained sand. In other parts the grains lie together more tightly than in others.
In general, higher ground will usually stay solid. The sandbar from which the helicopter picked up the three tourists in July is a long spine in the middle of Turnagain Arm that the tide covers last, after filling in the sides.
The flats closest to the base of the bluff at Oceanview are covered by high tide only three or four times a year, Lukens said.
Once soil conditions are prime for failure, it takes only a downward weight or vibration to set off collapse. When the particles are at least partly suspended in water, the weight load of a person stepping there is transferred to the water and the water can’t hold it, the scientists said.
‘’The soil loses its ability to support the extra load because the load is being transferred to the water and not grain-to-grain contact,’’ Raychel said.
Once the leg displaces the water, mud tightens around the leg.
‘’The foot is acting as a piece of sand or a boulder,’’ Swenson said. ‘’When people start moving to get out, they’re just getting rid of more water, collapsing more sand and going down further.’’
Winkler said, ‘’The water goes out between the grains, and the grains tighten up, and ... it molds around your foot.’’
Watch the tides
Getting trapped in mud may not be what people should fear most. What scares experts even more are the tides.
‘’People who actually get stuck in the mud (are) extremely rare. It seldom happens,’’ Opalka said. ‘’What happens is that someone will be way out there and they can’t get back in’' ahead of the tide.
Even that is rare, Opalka said. He could not remember anyone who died in such a case.
George Lukens said his family times mud-flat visits to the tides, usually starting back 21/2 hours before high tide, he said.
‘’It’s not a habit to be out there when the tide comes in,’’ he said.
David Swendiman, a 30-year-old outdoors educator from Girdwood who visits the flats once a week, characterizes the mud as ‘’dangerous, very dangerous and extremely dangerous. I can be on dry, solid, hard ocean floor. You can stomp on it, and I can be sunk up to my thighs in minutes if I work it in.’’
Swendiman sometimes sinks up to his thighs deliberately to demonstrate how to pull free. The basic rule: Lean over, try to make yourself prone, don’t vibrate or wiggle. And relax.
‘’I discovered that if I relaxed and pull out slowly, it released,’’ he said. He can do it in less than five minutes.
Mike Tumey, the Girdwood firefighter who saw Adeana Dickison drown, often rides his mountain bike on the flats.
‘’I wish, personally, I could enjoy the Arm without causing other people alarm, but to regard the Arm as a recreational opportunity for others is to set them up for disaster,’’ Tumey said. ‘’They need to become informed, through experience, of the dangers, just like (those who venture into) the high mountains.’’