192 
FLORIDA STATE GEOLOGICAL SURVEY. 
PICOLATA. 
Picolata is in the extreme western portion of St. Johns County, 
almost due west of St. Augustine, on the St. Johns River. A 
four-inch well, drilled about the year 1890, is now owned by 
R. H. Bohn. The depth was reported to be about 300 feet. The 
pressure of this well was taken January 10, 1910, and was found 
to be 15 pounds. The elevation of the well is approximately 8 
feet above the river. This, together with a pressure of 15 pounds, 
would give the well a head of 42.65 feet above the level of the 
water in the St. Johns River. 
RIVERDALE. 
Riverdale is a settlement along the St. Johns River, in south¬ 
western St. Johns 'County. At this place several artesian wells 
have recently been drilled. A well 302 feet deep was sunk in 
1909 by Mr. R. C. Walker for the Riverdale Land Company. 
This is a six-inch well and is cased 107 feet. The well is re¬ 
ported to have a head of 33J^ feet above the surface and the 
surface elevation above the St. Johns River is estimated to be 
8 feet, which gives the well a total head of 41J^ feet. The first 
rock encountered was at a depth of 175 feet, and at this depth 
the water was found to be under sufficient pressure to rise to 
the surface. An increase in the flow of water was reported at 
a depth of 190 feet. 
Mr. R. C. Walker completed on February 1, 1910, a well for 
Mr. J. D. Clark. This well is six inches in diameter, 318 feet 
deep, and is cased 136 feet. At the depth of 174 feet a one-foot 
stratum of bluish, clayey limestone was encountered. An in¬ 
crease in water is recorded at the depth of 200 feet, from which 
depth the first flowing water is reported. The well samples in¬ 
dicate that this flow comes from a very hard, bluish colored rock 
and water-worn small pebbles. Immediately on passing through 
this stratum, which was 19 feet in thickness, the Vicksburg Lime¬ 
stone was reached, as is shown by the presence of Nummulites. 
This determination was made from a very complete set of samples 
of the drillings from this well, kindly saved by the driller, Mr. 
