Soil Survey of Dallas County, Texas Page: 45
vii, 153 p., 70 fold. p. of plates : ill., maps ; 29 cm.View a full description of this book.
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DALLAS COUNTY, TEXAS
cial design, significant increase in construction costs,
and possibly increased maintenance are required.
This table also gives for each soil the restrictive fea-
tures that affect drainage, terraces and diversions, and
grassed waterways.
Pond reservoir areas hold water behind a dam or em-
bankment. Soils best suited to this use have low seep-
age potential in the upper 60 inches. The seepage po-
tential is determined by the permeability of the soil and
the depth to fractured bedrock or other permeable mate-
rial. Excessive slope can affect the storage capacity of
the reservoir area.
Embankments, dikes, and levees are raised structures
of soil material, generally less than 20 feet high, con-
structed to impound water or to protect land against
overflow. In this table, the soils are rated as a source of
material for embankment fill. The ratings apply to the soil
material below the surface layer to a depth of about 5
feet. It is assumed that soil layers will be uniformly mixed
and compacted during construction.
The ratings do not indicate the ability of the natural
soil to support an embankment. Soil properties to a
depth even greater than the height of the embankment
can affect performance and safety of the embankment.
Generally, deeper onsite investigation is needed to de-
termine these properties.
Soil material in embankments must be resistant to
seepage, piping, and erosion and have favorable com-
paction characteristics. Unfavorable features include less
than 5 feet of suitable material and a high content of
stones or boulders, organic matter, or salts or sodium. A
high water table affects the amount of usable material. It
also affects trafficability.
Drainage is the removal of excess surface and subsur-
face water from the soil. How easily and effectively the
soil is drained depends on the depth to bedrock, to a
cemented pan, or to other layers that affect the rate of
water movement; permeability; depth to a high water
table or depth of standing water if the soil is subject to
ponding; slope; susceptibility to flooding; subsidence of
organic layers; and potential frost action. Excavating and
grading and the stability of ditchbanks are affected by
depth to bedrock or to a cemented pan, large stones,
slope, and the hazard of cutbanks caving. The productiv-
ity of the soil after drainage is adversely affected by
extreme acidity or by toxic substances in the root zone,
such as salts, sodium, or sulfur. Availability of drainage
outlets is not considered in the ratings.
Terraces and diversions are embankments or a combi-
nation of channels and ridges constructed across a
slope to reduce erosion and conserve moisture by inter-
cepting runoff. Slope, wetness, large stones, and depth
to bedrock or to a cemented pan affect the construction
of terraces and diversions. A restricted rooting depth, a
severe hazard of wind or water erosion, an excessively
coarse texture, and restricted permeability adversely
affect maintenance.
Grassed waterways are natural or constructed chan-
nels, generally broad and shallow, that conduct surfacewater to outlets at a nonerosive velocity. Large stones,
wetness, slope, and depth to bedrock or to a cemented
pan affect the construction of grassed waterways. A
hazard of wind erosion, low available water capacity,
restricted rooting depth, toxic substances such as salts
or sodium, and restricted permeability adversely affect
the growth and maintenance of the grass after construc-
tion.
Community planning
This section briefly describes the factors to be consid-
ered in selecting a site for urban development, methods
to control runoff and erosion on construction sites, pre-
cautions to be taken to insure that public health is not
endangered in using the soils, and the most effective
methods of gardening and landscaping the soils.
Site selection
In selecting a site for urban development, careful
onsite investigation of the soil is necessary. Costly fail-
ures of buildings and other structures can occur unless
planners and builders select the proper soil for an in-
tended use. If a soil is poorly suited to the intended use,
site preparation can be very expensive and difficult. In
some cases, structures can be designed to overcome
the limitations of the soil, but only if the limitations are
known prior to design.
One of the main factors to be considered in selecting
a site is the susceptibility of the soil to flooding. The
alluvial Frio, Gowen, Ovan, and Trinity soils are subject
to occasional or frequent flooding and should not be
selected as sites for permanent structures. These soils
are best suited to use as green belts, sound barriers,
wildlife habitat, or recreation uses such as hike and bike
trails or picnic areas.
Other factors that affect site selection are soil perme-
ability, slope, texture, available water capacity, drainage,
reaction (pH), shrink-swell potential, strength, corrosivity
to uncoated steel and concrete, erosion and runoff char-
acteristics, hydrologic classification, suitability of the soil
to use as septic tank absorption fields, suitability for
foundations and local streets and roads, and potential
for recreation uses. Many of these soil properties, fea-
tures, and suitabilities are given in the sections "Engi-
neering" and "Recreation." The most important of these
factors are described in the following sections. Additional
information is given in tables 12, 13, and 14.
Foundations
The soils in Dallas County require careful examination
before they are used as sites for foundations. Through-
out most of the county, the soils are clayey and have a
high content of the clay mineral montmorillonite. Soils of
this kind swell when they are wet and shrink and crack
when they dry. This action creates such movement and
pressure that walls and foundations will crack unless45
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General Soil Map, Dallas County, Texas (Map)
Map displays soil types along with creeks, towns, schools, churches, power transmission lines, oil and gas pipelines, roads, and railroads. Includes legend and symbols. Scale 1:253,400
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Coffee, Daniel R. Soil Survey of Dallas County, Texas, book, 1980; Washington D.C.. (https://texashistory.unt.edu/ark:/67531/metapth130211/m1/55/: accessed July 16, 2024), University of North Texas Libraries, The Portal to Texas History, https://texashistory.unt.edu; crediting UNT Libraries Government Documents Department.