12MB PDF - Association for Mexican Cave Studies

Diving the big springs of the Sierra MadreSheck ExleyOur 5-vehicle caravan crossedthe border at Matamoros on Sunday,18 March, 1979. While it wasn'tplanned that way, most of the topdeep cave divers in the U.S. werealong. This turned out to be avery good thing since most of thenacimientos that we visited werequite deep. Our team included TerryMore from Michigan, Dan Lenihanfrom New Mexico, Frank Fogarty fromKentucky, Paul DeLoach and Ken Fulghumfrom Georgia, and Dale Sweet,Steve Forman, Jamie Stone, CarolVilece and myself from Florida.Aside from a small mordida, theborder crossing wasn't much of ahassle, though the sudden appearanceof 87 scuba tanks did cause someconsternation among the Federales.The following is a summary of ourinvestigations in the underwatercaves of northeastern Mexico, duringwhich 32 scuba dives were made.The term "depth" refers to verticaldistance below the water surfaceunless specified otherwise, and theterm "penetration" refers to the onewayswimming distance from the underwatercave mouth.Nacimiento del Rio SabinasWe selected this spring for ourfirst dive not only because it wasthe northernmost, but also becausewe tlad an excellent description ofit from accounts of previous divesby Bill Stone and Norm Pace. Anticipatingdepths in excess of 55meters, we dived twin 100 cu. ft.steel tanks filled to 3000 psig(giving each diver approximately 227cu. ft. of air, enough for 7-1/2hours at the surface but only 70minutes at 55 meters) and put acouple of cylinders of pure oxygen inshallow water for decompression.Oxygen is much more efficient thancompressed air when decompressingto prevent the "bends", and we werevery mindful of the fact that thenearest recompression chamber fortreatment was in San Antonio, Texas.On the first dive Dan, Jamie,Carol, Paul and I quickly followedthe large, sloping conduit of thespring to the 55 meter level, wherethe slope steepened somewhat (as BillStone had described in AMCS ActivitiesNewsletter #9). Unfortunately,at this point the passage was lessthan 1/2 meter high - too low forus with twin lOa's on our backs -Opposite:1893 photo of Nacimiento del R10 Choy showing original railroad bridge.23