Bill and Andy’s Whirlpool Sink

 

 

 

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

 

 

 

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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.