Altitude change

General banter about diving and why we love it.
Post Reply
kalailyliani
Just Settling In
Posts: 17
Joined: Sun Jul 24, 2016 12:06 pm

Altitude change

Post by kalailyliani »

I'm diving clear lake next weekend near Sisters, OR. The surface elevation of clear lake is 3,012′. Our dives will be <60' and we are planning a 2 tank dive.

Can someone direct me to a dive table or some info to calculate how long I must wait before going up to McKenzie observatory, which is 5,325 feet?

I'm new to diving and I know not to fly right after diving, but what's the rule on local elevation changes? Like, what if I lived 2000' above the dive site? Would i technically not be able to return home? :/
User avatar
Scubie Doo
I've Got Gills
Posts: 3027
Joined: Mon Oct 26, 2009 3:13 pm

Altitude change

Post by Scubie Doo »

I've never dove at altitude. But while in Hawaii it is easy to dive and drive up to altitude without thinking. A lot of people live at elevation in Hawaii and dive. However, that doesn't mean it is "safe". You should really take a course or get some training on diving at altitude. I have over 700 dives and I would take a course, even a private course just to ensure I was doing everything correctly. I know you can research online, but elevation is not something I would ever mess with unless I was 100% sure what I was doing. Just my opinion.
User avatar
Nwbrewer
I've Got Gills
Posts: 4620
Joined: Fri Jul 21, 2006 10:59 am

Re: Altitude change

Post by Nwbrewer »

This book covers all the theory stuff about the physiology of diving at altitude, though it's not an easy read -

When I looked a few years ago there weren't many classes available for altitude diving locally, and non from any of the instructors that I trust.

After all the reading I did on the subject, and discussing it with a few instructors, for anything in the 3K feet and under range, I've just done my dives with 32% on air NDL's and padded my stops by a bunch and called it good.

Jake
"Screw "annual" service,... I get them serviced when they break." - CaptnJack (paraphrased)


"you do realize you're supposed to mix the :koolaid: with water and drink it, not snort the powder directly from the packet, right? :smt064 " - Spatman
User avatar
WylerBear
I've Got Gills
Posts: 1293
Joined: Thu Aug 24, 2006 10:29 am

Re: Altitude change

Post by WylerBear »

Check the DAN website. There's got to be at least one or two articles about going to elevation after diving. Also, you know you also have to adjust your dives for the altitude as well, right? There is a table in the PADI AOW manual with adjustments. Probably in other manuals as well. And assuming you are driving there from a lower elevation, when you get to Clear Lake you may already be a G (I think, it may be H)diver without ever having submerged so you need a surface interval before diving too. It seems like the last time I dove there by the time we looked around a bit and slowly set up our gear, we had killed at least an hour and were good to go. Have a fun and safe time. I've dove there twice now and probably won't ever do it again but it is a cool dive.
Georgia

NOT diving is NOT an option
defied
I've Got Gills
Posts: 2057
Joined: Wed Sep 17, 2008 8:14 pm

Re: Altitude change

Post by defied »

Your theoretical depth will be around 65ffw. You'll be fine. Safety stop at 15ffw.

Dive like usual, go slow on ascent.

D
kalailyliani
Just Settling In
Posts: 17
Joined: Sun Jul 24, 2016 12:06 pm

Re: Altitude change

Post by kalailyliani »

Thank you all - I did do a bit of research yesterday and watched a few videos on dive tables and know about the additional +2 pressure grade per 1000 ft of elevation (yay! learning :) ) I am actually driving down the night before the dive so I should be ready to go for the first one. I've just never been to the area and really would like to see what I can while I'm there when someone started questioning me about DCS and what nots for a change of 2k altitude so it made me all paranoid.

I'll be sure to do the safety stops and do slow ascents. I'm sure we'll discuss it more while we're there to determine if it's a good idea or not, but I just didn't want to go in blind.

Appreciate all the help!! :)
User avatar
60south
Pelagic
Posts: 985
Joined: Sun Aug 10, 2008 1:24 pm

Re: Altitude change

Post by 60south »

The easiest way is often to plan your dive as if you're doing it at the maximum elevation. That way you don't have to worry about surface interval times and altitude. This also adds some conservancy to the plan.

For instance, if you're diving at 3000ft but later ascending to 5300ft, just plan the dive as if you're already at 6000ft (rounded up). Do still use the 3000' safety stop depth (14ft).

http://www.divebuddy.com/calculator/altitude.aspx
User avatar
H20doctor
I've Got Gills
Posts: 4225
Joined: Fri Apr 18, 2008 12:13 pm

Re: Altitude change

Post by H20doctor »

The best way to learn about altitude diving is to take the class and get your altitude cert card...
That way you have the training you've taken the class and you know how to program your dive computer
NWDC Rule #2 Pictures Or it didn't Happen
User avatar
Norris
NWDC Moderator
NWDC Moderator
Posts: 4695
Joined: Wed Sep 03, 2008 2:31 pm

Re: Altitude change

Post by Norris »

Or ask divers about it like you have, and research what is out there. Either way will likely work.
**Pinch it, don't stick your finger through. You're just pinching a bigger hole.
CAPTNJACK - 2012**
Furnari
Aquaphile
Posts: 169
Joined: Tue Oct 19, 2010 12:54 pm

Re: Altitude change

Post by Furnari »

I've done several dives at Clear Lake; as I recall it barely meets the criteria for an altitude dive (I could be wrong , however). While everyone is different, taking it easy on the dive, using a generous safety stop, breathing nitrox, and other conservative measures make sense. If you take your time breaking down your gear and packing your vehicle after staying the night, you should be fine ascending a couple thousand feet to do some sight seeing. The more time you give yourself, the better off you'll be. Maybe plan on having lunch before leaving? Also, avoid strenuous hikes around the observatory.

Are you staying in the cabins? IMO, the best diving is located out and to the left (east) of the cabins as that's where a lot of trees are within recreational depths. The rangers are generally assholes to divers and will direct you to the gazebo area west of the lodge (they won't even let you park in the main parking lot- true story). From there, you'll have a fairly lengthy swim to see the a decent number of trees. They tend to give you more leeway if you stay in the cabins; if so, find an entry along the path in front of them (as far east as possible).
kalailyliani
Just Settling In
Posts: 17
Joined: Sun Jul 24, 2016 12:06 pm

Re: Altitude change

Post by kalailyliani »

No cabins... They were all booked. I'll make a note to go east of the cabins for the good stuff! Thank you :)! There will be a group of at least 8 of us diving. I can't wait! I bought a computer today and can't wait to use it :joshsmith:
User avatar
selkie
Submariner
Posts: 563
Joined: Thu Dec 04, 2008 12:30 pm

Re: Altitude change

Post by selkie »

Belknap Hot springs resort is just down the road from Clear Lake. http://www.belknaphotsprings.com/
"A man must have some wit to know he is a fool"

Maritime Archaeological Society (MAS)
http://maritimearchaeological.org/

Northwest Diving History Association (NWDHA)
http://www.divinghistory.org/
kalailyliani
Just Settling In
Posts: 17
Joined: Sun Jul 24, 2016 12:06 pm

Re: Altitude change

Post by kalailyliani »

we're just gonna camp in the middle of the woods... somewhere... out there.

Should be able to see the perseid meteor shower too :partydance:

i wish it was next weekend already!
Steiger
Avid Diver
Posts: 53
Joined: Wed Dec 16, 2015 4:50 pm

Re: Altitude change

Post by Steiger »

A lot of dive computers have an altitude function, check to see if you can set it for your current elevation.
User avatar
lamont
I've Got Gills
Posts: 1212
Joined: Thu Jul 20, 2006 7:00 pm

Re: Altitude change

Post by lamont »

Steiger wrote:A lot of dive computers have an altitude function, check to see if you can set it for your current elevation.
I'd agree with the suggestion made by 60south to plan and execute it like it was at 5,325ft instead of 3,012ft

Realistically that shouldn't matter much since you'll essentially be doing a "deco stop" of at least an hour or two between the time that you surface from the last dive to the time when you finally arrive at 5,325 ft -- and that elevation change is only 2.45 fsw of pressure change.

Although you want to keep in mind that at around 6,378 ft things will likely get a little bit riskier since if you ascend from sea level to that altitude you'll basically be starting out your day surfacing from a hugely long saturation 'dive' at sea level and could be pushing an overpressurization gradient in all your long compartments (pressure at that altitude is equivalent to 0.79 ATA) in addition to whatever you pick up on the dive.
kalailyliani
Just Settling In
Posts: 17
Joined: Sun Jul 24, 2016 12:06 pm

Re: Altitude change

Post by kalailyliani »

Thanks everyone! i'm excited for this weekend.
The dive computer will indeed commodate the change in elevation and i'll talk to the DM about the dive plan tomorrow.

This newbie diver appreciates all the help!
Post Reply