GROUND WATER IN NORTH-CENTRAL TENNESSEE
GROUND WATER IN NORTH-CENTRAL TENNESSEE
GROUND WATER IN NORTH-CENTRAL TENNESSEE
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180 <strong>GROUND</strong> WATEK <strong>IN</strong> <strong>NORTH</strong>-<strong>CENTRAL</strong> <strong>TENNESSEE</strong><br />
No. 435, which, is about 200 feet southeast of the boiler room, derives<br />
most of its water from a cavernous zone in the Murfreesboro limestone<br />
between 50 and 65 feet below the surface, although several water<br />
bearing beds of small capacity were penetrated between this cavernous<br />
zone and the bottom of the well, at a depth of 217 feet. The well is<br />
pumped by air lift. It is reported by the driller that when first<br />
tested in May, 1927, the well yielded about 400 gallons a minute for 24<br />
hours, the drawdown indicated by the difference between starting and<br />
running pressures in the air line being approximately 70 feet. Hence<br />
the specific capacity is rather small about 6 gallons a minute for each<br />
foot of drawdown. During this first test at least 1 cubic yard of fine<br />
silt and corroded fragments of limestone as large as 2 inches in diame<br />
ter were discharged from the well, indicating that the solution chan<br />
nels that transmit the water are partly clogged with such debris.<br />
During the period July to September, 1927, the well was pumped<br />
almost continuously, and its yield ranged approximately between 75<br />
and 150 gallons a minute. A part of this variation was perhaps due<br />
to changes in the efficiency of the air4ift pump as the water level<br />
declined, but most of the variation was presumably due to seasonal<br />
fluctuations in the ground-water supply. This presumption is<br />
strengthened by the fact that the yield of the well increases about 24<br />
hours after a heavy local rain. It is noteworthy that this well is<br />
approximately on the projected trace of prominent joints that cut the<br />
Murfreesboro limestone at the orifice of the Murfreesboro city spring<br />
(No. 439, p. 187), about a mile to the southeast. Another well (No.<br />
434), about 150 feet northwest of No. 435, passed through the same<br />
water-bearing zones; its ultimate capacity is only about 5 gallons a<br />
minute. A third well (No. 433), which is 650 feet deep, penetrates a<br />
small water-bearing channel in the Murfreesboro limestone at a depth<br />
of 80 feet; a small amount of water may also be derived from a depth<br />
of about 350 feet. The rocks at the projected horizon of the St.<br />
Peter (?) sandstone were probably penetrated, although little if any<br />
water was found in them. The total capacity of this well, when<br />
pumped continuously, is about 12 gallons a minute, with a drawdown<br />
of about 180 feet. A fourth well (No. 436) comprises a sump 18 feet in<br />
diameter and 23 feet deep and an 8-inch drilled hole extending 63 feet<br />
below the bottom of the sump. Water-bearing zones in the limestone<br />
were penetrated 46 and 55 feet below the surface. Even after the<br />
well had been shot with dynamite at the bottom, its total capacity<br />
was only about 10 or 15 gallons a minute, of which about 5 gallons<br />
seeped from fractures in the walls of the sump and presumably<br />
originated in a near-by perennial creek. In general, the greatest<br />
likelihood of wells of large capacity exists where the course of a cavern<br />
ous zone in the limestone is indicated at the surface by a linear<br />
arrangement of sink holes or along a line parallel to master joints