A Push on Cannonball

August 18, 1996

Lake Wapepello, Missouri

Kurt Olson and Robert Laird

Jump to the Cannonball Push Gallery . (Beware: a lengthy download)

Cannonball's official name is Blue Spring (Lake Wapepello, near Greenville, Missouri) [originally, Davidson's Blue Spring or Blue Hole, or Blue Spring Hollow], and was first discovered as divable by cave divers in the mid 1980s. The first explorations were very promising with reports of a massive cave no deeper than 60 feet. These reports were quickly found to be incorrect as within the first year of exploration all the shallow leads had been walled out leaving only the giant, seemingly bottomless funnel-shaped main conduit to be explored. Kurt Olson and Mike Heusack conducted several trimix dives to explore Cannonball's great depths in the fall of 1991. Their final push dive was aborted when mike's drysuit flooded (a serious problem when the water temp is 56F) attempting to pass through the deep restriction. This attempt, while only adding 50 feet of line beyond the restriction, did show that Cannonball appeared to be leveling out and further exploration on trimix was feasible.

In the Nov. '92 to summer '93 time frame, many survey dives were made in Cannonball by Mark Hermerding, Bob Foster, Ralph Walter and Greg Schmoll. The result of their hard work was a terrific story and map published in the Sept/Oct 1995 Underwater Speleology (Vol. 22, No. 5). Their penetration was limited to 240 ffw while surveying the funnel-shaped room. The importance of their survey work, however, far overshadowed any interest in penetration.

On August 17th, 1996, Kurt Olson and I did a work up dive to prepare for a push dive on Cannonball Springs. With the assistance of Mike Heusack, Marvin Zaske and Sharon Jones, we placed oxygen at 30 ffw just outside the cave and deco bottles inside the cave at 60 ffw on the thick down line that descends into the depths of the great funnel shaped room. At the bottom of the funnel was a restriction at 285 ffw, and only a couple of people had ever been through it. So, Kurt had laid 50' of line on the other side of the restriction, but nothing else was known about what lay beyond.

Most of the time, the flow in Cannonball made this deep restriction similar - but much smaller - than the one at Devil's Ear, Ginnie Springs, FL. Such high flow made crawling through the restriction difficult and time consuming. On August 18th, however, the fates were with us for the flow was minimal. Visibility in the cave was about 40 feet (better, the further we got into the cave), and the water temperature was a bone-chilling 56F. We were ready.

Mike provided in-water/in-cave support, Marvin acted as the open-water safety diver, and Sharon provided shore support (most helpful to me when my 50w bulb burned out just as we were about to start the dive).

Our back gas was 16/40 trimix, and as we began the dive we carried a Nitrox 32 stage. We scootered into the cave opening and proceeded to the funnel room. At the 60' point on the down line hung bottles of Nitrox 45. We stopped long enough at that depth to hang our scooters on the line. We then dropped down to 120' where we hung the Nitrox 32 bottles and switched to back gas. At that point, we signaled our ok's to each other and the clock started. Based on identical fills and mixes, we had agreed upon a turn at 1900psi or 16 minutes, whichever came first. Exceeding either would result in either not enough gas or too much time for the tables we had cut with Abyss.

I dropped like a rock and moments later found myself at the restriction, waiting for Kurt whom we had agreed would enter first. After one or two attempts at a straight-on approach to the restriction, he finally slipped a bit to the right and popped through. I followed immediately, and too found slipping a bit to the right helped. I immediately saw the line and we followed it to the end, 50' beyond the restriction. We again signaled our pre-agreed upon ok's, Kurt tied off the reel, and we proceeded into a low but very wide bedding plane.

There was a thin layer of silt and a few hand-sized rocks strewn about, but little else to describe the traverse of the bedding plane. It didn't take long before we found the flat bottom beginning to slope down to a large bowl-shaped depression. Looking up from that, just beyond the depression, was another big room! I could see about 60 feet across to part of the room. Large boulders were poking up from all sides and the bottom, and it appeared to be about 40 feet to the bottom (we were at about 300'). Kurt found a ledge upon which to tie off the line -- having added about 150' -- while I poked my head below the ledge to see what I could see... just more of the big room. The ledge to which the line was tied forms the ceiling of the next large room at 300 ft deep. Both of our Aladdin Pros showed 301 ft. Further exploration in excess of that depth was prohibited by the restrictions of our decompression profile.

By that time, I was at 1900psi and almost 16 minutes, so as Kurt cut the line from the reel, I gave him the thumbs up, which he returned. The exit was completely uneventful, as were most of the deco stops.

The mouth of the cave is at about 35 feet so our 30 foot stop was done just outside the major restriction which marked the entrance. The 20 foot stop occurred at the interface between the murky - but warm - lake water, and the colder but much clearer cave water. It was the 10 foot stop, fully in the lake water, with 10-inch visibility (if you didn't stir anything up), where the shivering is replaced by sweating. Air breaks were often taken by finding your way back to the clear, cold water, to cool off for a moment.

For any further penetration to occur at Cannonball, at least two setup dives will have to take place, and many more bottles will be needed. Logistics are a nightmare since there is no dive shop within 45 miles, and that one is not open very often. (We used our own small compressor at Sharon Jones' house in Rolla, so many hours were spent each day filling and mixing tanks.) Access to the dive site is only by way of a fire trail (although it's better now than it was even two years ago). The water entry is either a 100 yard swim from a boat ramp, or a hill climb that would test even an British SAS bloke. We chose the former method.

No doubt about it, we were extremely lucky that the flow was as low as it was. Next time may be a different story. But there is obviously a lot more to explore, so we'll be back!

-- Robert Laird

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Two days after this push, we also did a push on Roubidoux Springs near Waynesville, Missouri.

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