Bill and Andy’s Whirlpool Sink




Location: Sec. 9 Montreal Quad.  UTM  X=4210530 Y=537270 Z=935.45’





Elevation in Sink from Raster Topo =  895







Aerial Photo





Detailed Aerial Photo







Digital Contour Map  C.I.= 10’  Depth Measured at 55’ going northwest



Color Fill Contour Map  C.I.= 10’


Area of Collapse = .8 acres



Drainage Area =  23.8 acres






Strike Collapse Amount = 13 m (41.6’)




Dip Collapse Amount Max = 18 m (57.6’) Min= 7 m (22.4’)







Surface Geology – Collapse in Lower Gasconade





Depth to Possible Cave about 50’  C.I. = 20’








General Comments


Excellent example of cavern collapse in the lower Gasconade formation in a hillside setting.  Large, well defined sinkhole accepts a large surface flow after heavy rains.  The sinkhole was observed to have tree limbs and other debris lying in a circular



1967 Detail Map of Sinkhole



pattern at the base of the sinkhole, indicating high flow rate into the sink.  The sink supposedly has been dye traced to Toronto Spring.  A temperature survey was conducted but was inconclusive.  High probability of cavern in connection with sinkhole.  Only negative is large amount of soil and debris to excavate. There is quite a range of potential depths to the cave depending on whether the digital topo data or the raster topo data is used.  My geologic intuition says that we are less than 20’ from a sizable cave.  Plans are to resurvey (temperature) the sink in wintertime to predict depth to the cave.  An elevation measurement at the low point in the sink would also be helpful.