This is a two part series of my TDI Decompression Procedures class. The reason that this class is broken into two parts is because my check out dives are in two different dates as we can only do two dives per day because of our nitrogen loading. Part 1 covers our classroom and first two dives of the class.
The classroom and first two dives were on July 21, 2006 at the Blue Hole in Santa Rosa, NM. The classroom portion mainly consisted of dive planning and gear configuration. For dive planning we planned our dives to 120 feet based on U.S. Navy Dive Tables. For those who have dove the Blue Hole you know that the maximum depth was 82 feet. (Yes, I know I said “was”. You’ll find out.) So you may be thinking “WTF?!?!?! There is a huge difference between 82 feet and 120 feet!!” The reason that we planned the dive to 120 feet is because we had to take altitude and water temperature into account. We planned the first dive to be at 120 feet for 20 minutes. So going by the U.S. Navy Air Decompression Tables we would have to do a deco stop at 10 feet for two minutes and our ascent rate from our max depth to 10 feet would need to take a minimum of 6 minutes. My instructor informed me that he also practices a deep stop at half the maximum depth for a minute during our ascent. We know had all the information from the dive tables that we needed. We now went through and calculated what our maximum partial pressure of oxygen and nitrogen would be at 120 feet. After we calculated this information and wrote it all down we reviewed all the information again to make sure we didn’t miss anything. Once we started had our plan we then started gearing up where the instructor critiqued my hose routing a bit and then had me do valve drills on while on the surface. After this we donned our drysuits and geared up and walked to the water.
In the water we did a buddy check and bubble check on each other’s gear, and reviewed our dive plan one last time before going underwater. At first I was a little apprehensive about the dive. This was the first time I was going to be on a dive where I had a manditory decompression stop and I didn’t know what to think about it at first. Shortly after the dive started I started to relax and we just swam around looking at all the different features of the Blue Hole. This was the first time that I would really go to the bottom and spend any kind of noticable time looking around at the bottom of the Blue Hole. I looked back behind the grate covering the cave entrance where I found the deepest depth that I have ever found at the Blue Hole. It was 86 feet! Back behind the grate was cool. Part of the cave entrance was exposed and you could see down in it and really get a sense of how much water the aquifer is really pushing through the hole. Soon enough our bottom time was up and my instructor signaled to make our ascent to our deep stop, where we would hang for a minute before making our way to our 10 foot decompression stop.
Once out of the water we took off our gear and the instructor walked over to me and said that he was going to pull my bottom eye lid down and look between the eye lid and the eye for bubbles. If there are bubbles they will be nitrogen bubbles. He informed me that during any dive if a diver has more than three bubbles in any eye then the diver should be placed on oxygen and monitored for signs and symtoms of Decompression Sickness. He checked my eye’s and I checked my instructor’s eye’s. Neither one of us had any bubbles.
Here is the dive profile from dive 1:
Maximum Depth: 86 feet
Bottom Time: 20 minutes
Run Time: 28 minutes
Water Temperature: 62 degrees
Visibility: 30 - 40 feet
After a six hour surface interval we met back at the Blue Hole to get ready for our second dive. For this dive we planned a 25 minute bottom time at 120 feet using the U.S. Navy Air Decompression Tables. This dive would have the same deep stop, but the 10 foot decompression stop would be 6 minutes and the total ascent time would take 10 minutes. Once geared up we walked down to the water and did a buddy check and bubble check on each other and reviewed our dive plan one last time before making our descent. On this dive my instructor wanted me to relax as much as possible and didn’t want me to create a work load for myself. This was because he wanted to go through and calculate my SAC rate for our future dives. This dive was very relaxing and I felt much more comfortable on this dive then I did on the second dive. At 25 minutes we started making our ascent to the deep stop for one minute and then made our way slowly to our 10 foot deco stop. On this stop I really got a sense of what deco stops where all about. I was litterly dusting silt off the side of the hole with my hand waiting for the time to pass. Several minutes later we made our way up and were out of the water.
Here is my dive profile for dive 2:
Maximum Depth: 85 feet
Bottom Time: 25 minutes
Run Time: 39 minutes
Water Temperature: 62 degrees
Visibility: 30 - 40 feet
Later that evening we completed our dive logs and reviewed our dive profiles and talked briefly about our next two dives. I can’t wait for the next two dives and we are planning those dives and working out a location that is deep enough for the next two dives. I’ll write about those dives after they have been completed.
Part 2:
After my first two dives as part of the decompression procedures class I went ahead and asked my instructor if we could go ahead and throw in the advanced nitrox class and work on it as well. He agreed to do so and ordered the book for me. In hind site it would have been more advantageous to take the advanced nitrox class first. The reason being is that the advanced nitrox class answered allot of my questions that I would have thought would have been covered in decompression procedures. Overall this was a good class and I feel comfortable planning and executing basic staged decompression dives. I will definitely put the skills to use in the future for staged decompression dives.
We originally were going to dive at a site called Rock Lake, but the lake is on private property and the owner of the property only leases out the lake to one dive shop at a time and another shop already had the lake leased. It was fine with me because one of the disadvantages to the decompression procedures class is that it advocates deep air, which I don’t like the idea of being impaired for such a serious dive. I will however dive Rock Lake sometime in the future and hopefully it will be on a trimix based gas.
Below are my profiles from my dives from September 29-30, 2006. The dives were executed at the Blue Hole in New Mexico and were planned out using Buhlmann air decompression tables for 120ft for 25min. As stated in the previous blog the reason the dives were planned for 120ft is to compensate for altitude and the cold. In all reality I didn’t mind having the conservatism built into the dives as these are some of my first staged decompression dives.
Dive Profile from Dive 1:
Maximum Depth: 87 feet
Maximum Bottom Time: 25 minutes
Run Time: 48 minutes
Water Temperature: 62 degrees
Visibility: 80+ feet
Dive Profile from Dive 2:
Maximum Depth: 87 feet
Maximum Bottom Time: 25 minutes
Run Time: 49 minutes
Water Temperature: 62 degrees
Visibility: 80+ feet
Dive Profile from Dive 3:
Maximum Depth: 86 feet
Maximum Bottom Time: 25 minutes
Run Time: 45 minutes
Water Temperature: 62 degrees
Visibility: 60+ feet
Dive Profile from Dive 4:
Maximum Depth: 87 feet
Maximum Bottom Time: 25 minutes
Run Time: 46 minutes
Water Temperature: 62 degrees
Visibility: 60+ feet
