GROUND WATER IN NORTH-CENTRAL TENNESSEE

SOI
hydrogen sulphide and contains so much dissolved matter as to bfe
Unfit for boost purposes. To judge from conditions in other parts of
the Highland Hun plateau it is likely that all strata underlying the
Chattanooga stale or much more than 200 feet beloW tfe'e surface are
dry or c6ntain only highly concentrated brine such as that repress&nted
by analysis 120. Hence in the upland areas deep driilling for water fe
generally inadvisable.
Along the Highland Rim "escarpment and iii other deeply dissected
parts of t!(l« county ground-water conditions are most variable, for
channeled zones in the limestone have not adjusted themselves to the
present erosion cycle. Hence water-bearing £ones are discontin-
u6us atod are not likely to occur far below the level of the perennial
streams. Most successful drilled wells in these areas are less than
50 feet deep. Fortunately, perennial seepage aM tubular springs
(pp. 90-95) are numerous and constitute an idequate and reliable
source ol water in many places. Seepage springs are especially
abundant along the weathered outcrops of extremely cherty members
in the Fort Payne formation and at the top of the Chattanooga
shale, an impermeable stratum that prevents i&OwnwBrd perco­
lation of ground Water. The larger of the tubular springs generally
occur at the perennial heads of the tributary streams, about 75 o£
100 'feet below the Highland Rim peneplain, such as No. 115 (p. 206).
The aggregate discharge from such springs constitutes the ground-
water drainage from the peneplain tracts. Generally, the Water from
the mtermittent springs and from those perennial springs that dis­
charge several gallons a minute or more is suitable for any ordinary
use. On the other hand, tne water from some of the smaller seepage
springs is unsuitable for many uses, that wnich issues from the Chat­
tanooga shale feeing generally high in iron and in hydrogen sulphide.
Furthermore, the water that issues from some of the earthy beds of
the Fort Payne 'formation is extremely high "in hohcarbonate or per­
manent hardness and contains appreciable quantities of hydrogen
sulphide, as is represented by analysis 126. Ba some plates along
the lower slopes of the Highland Rim escarpment and near its base
the Silurian and Ordovidan rocks contain hard hydrogen sulphide
water or highly concentrated brine only 50 feet below stream level,
so that potable water may hot be obtainable from drUted wells. Iii
the vicinity of Bethpage, for example, well 123 derives water of good
quality from the Leipers limestone or the Catheys formation 38 feet
below the surface. Of two wells on the D. Beard property, a quar­
ter of a mile southwest of well 123, one encounters "black sulphur"
wfeter and the other "whifce sulphur" water^watefs containing hy­
drogen sulphide with and without an appreciable quantity of
respectively. Itt the same vicinity wells more tha:n 50 feet