Boiling Spring on the Big Piney

Texas County, MO

January 2003

Ethan Brodsky

(Underwater Photos by Tami Thomsen)

Sometimes the caves are easy to find.


We had been planning to survey a series of three unmapped springs in the Missouri Ozarks, in order of increasing difficulty. We started with the "easiest" project, Morgan Big Spring, in February 2002. This shallow spring gave us an opportunity to develop our team survey technique and our map was published in NSS-CDS Underwater Speleology (Vol. 29, No. 3:10-12). Next was Boiling Spring on the Gasconade, which we considered more difficult because of its length, depth, and the fact that it was not yet entirely explored. We have mapped 1800+ feet of passage at depths exceeding 175 feet, and the project is ongoing, with the next push dive scheduled for August 2003. An account of our progress to date is published in Underwater Speleology 30 1:9-13. The third cave was to be Boiling Spring on the Big Piney, which we considered the most difficult to map. With several rooms, complex passage geometry, a cork-screw funnel with significant depth ranges, and quite a bit of flow, we expected it to be a major undertaking.

In surveying these three caves, we have assembled a team of divers familiar with sidemount and comfortable in smaller caves. Each is able to work at depth and experienced with mixed gasses. Each individual brings along additional specialized skills, which include underwater photography and videography, computer-aided cartography, and detailed sketching.

Normally Missouri has relatively mild winters, but, to our surprise, on the drive down, the forecast was for 4-7 inches of snow and we were hearing about school closings on the radio. The state has already had twenty inches of snow this winter, and it was so cold that we suited up in our hotel room in Licking before driving to the dive site. The air was so cold that the pressure relief valve in our compressor kept freezing and had to be warmed with a thermos of hot water so we could continue filling tanks. The upside however, was that when we put our tanks into the 58 degree spring water, the pressure jumped and we were rewarded with "Florida fills", even though our compressor only pumps to 3200 psi.

The river, however, was in the low 40s, and the the google-eye and bass decided they'd be better off in the warm spring water. This is not as easy as it sounds, entering the spring requires jumping over a dam that raises the spring pool. However, there are hundreds of fish in in the cave, all the way back to the gravel choke. Fortunately, they are better behaved than the fish in Big Spring - usually they'll stay out of your way and not silt out the cave.
The spring is surrounded by private property, across the Big Piney River from the Boiling Spring public access, a gravel easement normally used for launching canoes and small fishing boats. We clipped on our tanks and waded across the river to the spring. Because of the cold weather, the edges of the river iced up overnight, and we were forced to break away sheets of ice before we could get started each morning.


Five divers participated in this survey project over a series of twelve dives. Tami Thomsen and Keith Meverden were the first team into the cave. Keith installed the survey line and Tami followed behind and put in survey stations. Tami made an attempt at the gravel choke restriction, but the flow was too high and she ended up eating rocks. On the way out, they recorded station distances and depths and sketched some cross-sections.

Ethan Brodsky came through next and took depth/floor/ceiling measurements at stations A1-A7 and azimuths for all 23 stations. Micki Feakes sketched the entrance and passage cross-sections at stations A1-A4. That evening, Ethan archived data and plotted a 3D stick map on the computer. Unfortunately, Keith had to leave before he could contribute further, as his Army Reserve unit was called up. We cut his hair before he left.

The next day, Tami and Ethan pulled tape and measured left/right data for stations A1-A7 and A13-A18 and took additional cross-sections in the gravel slope. Micki sketched A5-A7 and added detail to the A1-A4 sketches. Marvin Zaske joined the group and sketched cross-sections of the pit at A9-13 and estimated wall distances. Due to insomnia, Tami began work on a preliminary map that night.

The next dives were devoted to cross-checking some confusing data, taking measurements to complement sketches and detailing particularly interesting parts of the cave. Tami took still photos to document the cave and the survey effort. She also sketched additional detail at A0a, A7-A9, and the air bells. Ethan and Marvin pulled tape to measure distances for the A9-A13 cross-sections.

A final dive was devoted to photography and clean-up. Tami took pictures, while Ethan and Marvin went back to double-check data on the air bells. Finally, Marvin began pulling the station markers while Tami removed the entire survey line. Marvin also removed an ancient tattered line tangled in the cave at 120 feet depth. The original gold line remains.

Marvin and Ethan head in to survey the lower tunnel.

At each station, we used the survey tape to measure the passage geometry. We took turns working the dumb end of the tape. In previous projects, the passage geometry was fairly regular, and we just took left/right/up/down measurements. Here, the passages were much more complex, and we first sketched the cross-section and then took quantative measurements with the tape.

Marvin and Ethan confirm measurements.


Each night, we entered the survey data into a computer and plotted a 3D stick map of the cave. These stick maps helped us visualize the cave and aided in planning our survey efforts. With earlier projects, a plan view (top view) was sufficient to understand the layout of the cave, but this time, we found it difficult to convey the geometry of the "chute" with just a plan view. Tami drew an isometric 3/4 plan/profile view of the corkscrewing passage that made the layout clear.

(L) Profile stick-map, viewed from South.

Profile stick-map, viewed from East (R)

The map was submitted to the Missouri Speleogical Survey and exibited alongside our other two maps in the Map Salon at the National Speleological Society - Cave Diving Section 2003 Workshop.

The Boiling Spring on the Big Piney survey concludes a year-long effort to map three long-unappreciated sidemount springs in Missouri. The effort yielded not only three maps, but also an understanding of the investment in time and resources required to produce top-quality maps. Along the way, Tami took a bunch of great pictures, and Eric Parker Andersen and Richard Dreher produced a documentary film about the effort.

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Ethan Brodsky <brodskye at>