Lewes CCD Pilot Study Working paper

[From the U.S. Government Printing Office, www.gpo.gov]

F577

Coastal Zone
information
Center
LEWES CCD PILOT STUDY

ju'@J, v

WORKING PAPER NUMBER 10

SOILS AND THEIR IMPLICATIONS
FOR DEVELOPMENT

MARCH 1976

PREPARED BY
DELAWARE STATE PLANNING OFFICE

GB PREPARED UNDER COASTAL ZONE MANAGEMENT
459.4 PROGRAM DEVELOPMENT GRANT
C48 NUMBER 04-6-158-44014; WORK ELEMENT 1506
no.10
1976
4

INTRODUCTION

Any effort to guide urban and rural development at the state,
county, or local level of government in the public interest
must recognize the existence of a limited natural resource
base to which both urban and rural development must be
adjusted if serious environmental and developmental problems
are to be avoided. This is particularly true in the Lewes-
Rehoboth area where an increasing number of urbanites are be-
coming year-round residents of outlying areas, seeking not
only the varied recreational opportunities offered.by these
areas but also the feeling of open space, which these areas
lend to urban development.

The soil resources of an area are one of the most important
elements of the natural resource base, influencing both urban
and rural development. Much that is of importance to mankind
takes place in.the@soil; and soil is, directly or indirectly,
the foothold for much of the life on earth. It is the natural
medium for the growth of plants; its properties and life serve
to stabilize wastes and purify water; it serves as the founda-
tion for buildings, roads, and all other man-made land-based
structures.

Soils are an irreplaceable resource; and mounting development
pressures upon land are making this resource more and more.
valuable. The soil resource has been subject to misuse through
improper land use and transportation facility development.
Such misuse has often led to,severe environmental problems,
V which are very expensive to correct, and to the deterioration
and ultimate-destruction of the resource base itself. To
avoid further misuse of this important element of the.natural
resource base, then, it is necessary to acquire definitive
data about this element and then to utilize such data to the
greatest extent possible in guiding both urban and rural
development.

In 1968 the State Plann-Ing Office negotiated a cooperative
agreemeAt with the Soil Conservation Service for the completion
of a detailed soil survey for Sussex County, together with the
provision of interpretations for planning and engineering purposes.
The work was completed in 1971 and published in 1974. The
purpose of this report is to assist local governmental officials
and citizens in.becoming familiar with the soil survey and its,
various applications in local planning and development programs
in order that further misuse of soil resources of the county
I can be avoided.

..Soil scientists made this survey to learn what kinds of soil
are in Sussex County, where they are located, and how they
can be used. They observed the steepness, length, and shape
of slopes; the size and speed of streams; the kinds, of native
plants or crops; and many facts about the soils. They dug
many holes to expose soil profiles. A profile is the sequence
of natural layers, or horizons in a soil; it extends from the
surface down into the parent material that has notbeen changed

2 -

much by leaching or by the action of plant roots.

The soil scientists made comparisons among the profiles@
they studied, and they compared these profile.s.with those
in counties nearby and in places more distant. They
classified and named the soils according to nationwide,
uniform procedures.

Soils that have profiles almost alike make up a soil
series. Except for different texture in the suface layer,
all the soils of one series have major horizons that are
similar in thickness, arrangement, and other important
characteristics'. After a guide for classifying and naming
the soils had been worked out, the soil scientists drew the
boundaries of the individual soils on aerial photographs.

While a soil survey is in progress, soil scientists take
soil samples needed for laboratory measurements and for
engineering tests. Laboratory data from the same.kind,of
soil in other places are also assembled. Data on yields of
crops under defined practices are assembled from farm
records and from field or plot experiments on the same kind
of soil. Yields under defined management are estimated for
all the soils.

Soil scientists observe how soils behave when used as a
growing medium for native and cultivated plants and as
material, foundations, or covering for structures. They
relate this behavior to properties of the soils. For
example, they.observe that filter fields for onsite disposal
of sewage fail on a given kind of soil, and they relate this
to slow permeability or a high water table. They see that
streets and pavement crack on a given kind of soil, and they
relate this failure to frost action. Thus, they use
observation and knowledge of soil properties, together with
available research data, to predict the limitations or
suitability of a soil for present and potential uses.

The soil survey is designed to give the alternative uses for
each kind of.soil and to predict the outcome of these uses
under alternative practices. These alternatives are for the
consideration and decision of individuals and local planning
agencies.

Community planning commonly proceeds along two different but
interrelated lines: First, a general soil map shows the
areas where most of the land tracts are suitable for certain
uses, structures, or combinations of them; and second, the
detailed soil map in the soil survey is a guideto specific.
operations for the individual tracts. This does not mean
that the soil survey can be followed blindly. Even a detailed
soil map has'limitations of scale. Because of these limitations,
a mapping unit' of one kind of soil may include tiny areas of
a different kind. The text with the soil map explains the

potentials.and the hazards, but the soil survey does not
eliminate the need for onsite study for the best design
and location within a small tract fora building or for a
sewage filter field. Then, too, although soil examinations
are normally made to a depth of 5 or 6 feet, deeper material
beneath the soil may influence some kinds of construction or
other soil uses.

INTERPRETATION OF SOIL SURVEY DATA

Urban development requires planning and engineering programs
designed to guide and shape urbanization in the public
interest and thereby to avoid costly developmental and environ-
mental problems. In turn, these planning and engineering
programs require not only detailed information on the physical,
chemical., and biological properties of the soils but also
analysesof the suitability of such soils for residential,
commercial, industrial, recreational, transportation, and
other urban land uses, as well as for agricultural,
conservation and other rural land uses.

Interpretive ratings are usually written in terms of limitations
for use. This isbecause there are few soil limitations that
cannot be overcome if the user is willing and able to pay the
cost of the measures necessary to overcome the limitations.

The various interpretive analyses available to users of the
soil survey are presented and discussed below. There are
four general groups of interpretive analyses that contain
useful information for soil survey users. These four groups
are:

1. Interpretations for engineering purposes, such as the,,
chemical and physical properties of soils, water management
characteristics of soils, and the limitations of soils for
road construction and other specific engineering applications.

2. Interpretations for planning purposes, such as the limita-
tions of soils for residential development with or without
public sanitary sewer service; for light industrial and
commercial buildings; and for highway, railroad, and airport
location.

3. Interpretations for agricultural purposes, such as the
limitations of soils for cultivated crops, pasture and wood-
lands; the capability of soils for irrigation and drainage;
and estimates of cropland and woodland yields.

4. Interpretations for aesthetic and recreational purposes,
such as the limitations of soils for wildlife habitat or
the maintenance of greens, shade trees, and ornamental shrubs.

The system used in rating soils for specific uses or
characteristics con Isists of three degrees of "limitations":
slight, moderate, and severe. These are discussed below in
order to clarify the range of each.

SLIGHT LIMITATIONS

A slight limitation means that the soil may be.safely used
for the specified purpose with only normal care in construction
or installation and in maintenance.

MODERATE LIMITATIONS

A moderate limitation means that the soil may be used for a
specified purpose, but use will commonly be accompanied by
some difficulties that can be prevented or overcome by
relatively easy special planning, special treatment, or
both.

SEVERE LIMITATIONS

A severe limitation for a particular use does not necessarily
mean that thesoil cannot be put to that use, but it would
require extensive and costly measures in order to overcome
the limitations. In fact, the limitations for these areas
are usually so severe that it is presently not economical or
feasible to correct them.

SOIL INTERPRETATIONS FOR PLANNING PURPOSES

Almost all soil properties and their limitations for various
urban and rural uses are of substantial interest to regional
and local planning agencies en aged in comprehensive planning
for the physical development of new urban areas and for the
conservation of natural resources. Particularly tailored to
the regional and local planners' needs are the limitations of
soils for certain urban and rural uses given in Table 1. The
degree of limitation reflects the most significant single
limitation, but more than one kind of limitation may be listed.
For example, a soil may have a moderate limitation for a
certain use because of both a moderately high water table and
slope. A soil may have a moderate limitation for a certain
use because of permeability, but a steeper soil of the same
series may have a severe limitation because of slope alone.

Following are the soilproperties that affect the uses
specified in Table 1.

Disposal fields for septic-tank systems. --Permeability, depth
to seasonal high water table, natural drainage, slope, and
hazard of flooding or ponding.

Sites for sewage lagoons.-- Permeability, slope and hazard
of flooding or ponding.

Foundations for houses of three stories or less, without basements.--
Depth to water table, natural drainage, stability of the soil
slope, and hazard of flooding or ponding. For larger or heavier
buildings, a special investigation should be made at each site.

Foundations for houses with basements, -- Depth to water table,
natural drainage, stability of the subsoil (especially when
wet), slope and hazard of flooding or ponding.

Streets and parking lots. --Depth to water table, stability,
slope and hazard of ponding or flooding.

Sites for sanitary land fills. -- Permeability, depth to water
table, natural drainage, slope, hazard of flooding or ponding,
and plastic properties. For trench-type landfills deeper than
5 or 6 feet, onsite studies are needed of the underlying strata,
the water table, and the hazards of aquifer and ground water
pollution.

Home gardens and landscaping. --Available moisture capacity,
natural.fertility, depth to water table, natural drainage,
texture of the surface layer, slope, degree of erosion*, and
hazard of flooding or ponding.

RESIDENTIAL DEVELOPMENT WITH PUBLIC SANITARY SEWER

Figure 1 shows those soils recommended by Soil Conservation
Service to be left in their natural state. All of these soils
are subject to severe flood hazards. Included in this category
are coastal beach sands, tidal and fresh water marshes, flood-
plains and muck. In addition to flooding, most of these soils
have stability or bearing strength problems that require expensive
measures, such as pilings, for structural support. Slab construction
or similar techniques used on filled marsh or coastal sand often
suffer toundation settlement problems. Complete foundation
failure resulting from flowing water across coastal beaches is
a common occurrence with conventional techniques.

Figure 2 shows those upland soils with severe limitations for
development. This category includes those soils that have
severe wetness or ponding problems. Buildings constructed on
these soils will suffer wet basements or accessibility
limitations. The land surrounding a home built on soils with
a high water table is often useless during the wet season.
Moreover, soils of this type often have foundation problems and
excavations are unstable. The wet conditions severely limit
the use of construction equipment and access by Automobile.

The combination of Figures 1 and 2 show those soils within the
study area that,despite the provision of public utilities,
have severe limitations for residential or other development.
Most of the soils in this category border directly on Delaware
and Rehoboth Bays or their estuaries and the Atlantic Shore.
The remainder are associated with the h eadwaters of most streams
or are located in poorly drained areas on the northern side of
Rehoboth Bay and in the west-central portion of the CCD.

The extension of public utilities into or near these areas must
be considered carefully, because development pressures will
eventually create hardships for future residents. On the other

owl too' =A, 4W MO.

TABLE 1

LIMITATIONS OF SOILS FOR RESIDENTIAL AND RELATED USES

Degree and Kind of Limitation for-

Foundations for Houses of Three
Stories or Less- Sites for Sanitary Landfills
Soil Series and Disposal Field For - Streets and
M"_S]tq*oft Sellitic-tank Syae s w L .1 Wittiout Baseriverm With Basements Parking_Lots Trench Method Area Mediod

Se"land: Bd Severe: high water Severe: rapid Severe: high water Severe: high water Severe: high water table. Very severe: high water Severe: high water table;
table. 3 permeability,3 table. table. table; verf poo, very poor traffi-
drainage. cability when wet3
Borrow pits: Bo.
No interpretations.
Material too
variable.
Coasluil beach and dune Severe: fluctuating Very severe: rapid Severe: fluctuating Severe: fluctuating Severe: fluctuating water Very severe: rapid Very severe: rapid
land: Co. water table; tidal permeability; tidal water table; tidal water table; tidal table; tidal flooding; poor permeability; tidal permeabil ; tidal
floodin%3 flooding.3 flooding; poor flooding, poor stability. floWir43 floodinq3
stability; storm stability; storm
hazard. hazard.
Elkton: El, Em Severe: high water Slight Severe: high water Severe: high water Severe: high water tabld Very severe: high water Severe: high water table;
table; slow table. table. table, poor drainage; poor drainage., plastic
permeability. plastic subsoil. subsoil.
Evesboro:
E08 Slight/Severe2 Severe: rapid permea- Slight Slight Slight to moderate: 0 to 5 Severe: loose; caving; Severe: rapid permea-
bility.3 Percent slope- rapid permeability.3 bility.3
EoD, EsD Moderate: 5 to 15 Severe: rapid permea- Moderate: 5 to 15 Moderate: 5 to 15 Severe: 5 to 15 percent Severe: loose; caving; Severe: ragid permea-
percent slope-3 bility; 5 to 15 percent percent slope. percent slope. slope. rapid perMeability.3 ability.
slope.
EvA Slight/Severe2 Severe: rapid perrnea- Slight Slight Slight Severe: rapid permea- Severe: rapid permea-
bility.3 bility.3 bility-3
EvB Slight/Severe2 Severe: rapid permea- Slight Slight Moderate: 2 to 5 percent Severe: rapid permea- Severe: rapid permea-
bility.3 slopes. bility.3 bility.3
Fallsington: Fa, Fs Severe: high water Moderate: moderate Severe: high water Severe: high water Severe: high water table. Very severe: high water Severe: high water table.
table- permeability. table. table. table.
Fill land: Ft.
No interpretatiorm
Material too
variable-
Johnston: 30 Severe, high water Severe. flood hazard.3 Severe: high water Very severe: high water Severe: high water table; Very severe: high water Very severe: high water
table; flood hazard.3 table; flood hazard. table; flood hazard. flood hazard. table; flood hazard.3 table; fk)od hazard.3
Kalmia: Ka slight Moderate: moderate Slight Slight slight Slight Slight
permeability.

See tootrbotes at arid ot table.

AN am go, M Ws M) MW No on) go; Aft

TABLE I (continued)

Degree and Kind of Limitation for-

Foundations for Houses of Three
Stories or Less- Sites for Sanitary Landfills

Soil Series and Disposal Field For Streets and
map symbols Septic-tank Systems Sewage Lagoon Without Basements With Basements Parking Lot Trench Method Area Method

Keanansville:
KbA Slight/Severe2 Severe: rapid permea- Slight Slight Slight Severe: rld permea- Severe: rapid permea-
bility.3 ability. bility.3
KbB Slight/Severe2 Severe: rapid permea- Moderate: 2 to 5 percent Severe: rapid permea- Severe: rapid permea-
bility.3 slope. bility,3 bility.
Keyport:
KfA Severe: slow permea- Slight Slight Moderate: moderately Moderate: moderately high Severe: moderately high Moderate: moderately
bility; moderately high water table. water table. water table. high water table.
high water table.
KfB2 Severe: slow permea- Moderate: 2 to 5 Slight Moderate: moderately Moderate: moderately high Severe: moderately high Moderate: moderately
bility; moderately percent slope, high water table. water table; 2 to 5 per- water table. high water table.
high water table. cent slope.
Klej: KI Moderate: moderately Severe: rapid Slight Moderate: moderately Moderate: moderately high Severe: rapid permea- Severe: rapid permea-
high water table.3 permeability.3 high water table. water table. bility.3 bility; moderatel
high water tab15

Matawan:
Mm Severe: slow permea- Slight Slight Moderate: moderately Moderate: moderately high Severe: moderately high Moderate: moderately high
bility; moderately high water table. water table. water table. water table.
high water table.
Mn Severe: slow permea- Slight Slight Moderate; moderately Moderate: moderately high Severe: moderately high Moderate: moderately high
bility; moderately high water table. water table. water table. water table.
high water table.
Muck, shallow: Mu Very severe: high water Very severe: organic Very severe: high water Very severe: high water Very severe: high water Very severe: high water Very severe: high water
table; ponding.3 material; ponding.3 table; ponding; table; ponding; no table; ponding; organic table; ponding.3 table; ponding.3
organic material; no stability when wet material; no stability
stability when wet. when wet.
Osier: Os Severe: high water Severe: rapid permea- Severe: high water Severe: high water Severe: high water table. Very severe: high water Severe: high water table;
table.3 bility@3 table- table; wet excava- table; rapid permea- rapid permeability.3
tions unstable. bility. 3
Pocomoke: Pm Severe: high water Moderate: moderate Severe: high water Severe: high water Severe: high water table. Very severe: high water Severe: high water table.
table. permeability. table. table. table.
Portsmouth: Pt Severe: high water Moderate: moderate Severe: high water Severe: high water Severe: high water table. Very severe: high water Severe: high water table.
table. permeability. table. table. table.
Rumford:
RuA Slight/Severe2 Severe: rapid permea- Slight Slight Slight Severe: rapid permea- Severe: rapid permea-
I bility.3 bility.3 bility.3
RuB Slight/Severe2 Severe: rapid permea- Slight Slight Moderate: 2 to 5 percent Severe: rapid permea- Severe: rapid permea-
bility.3 slope. bility. 3 bility.3
RuC_ Slight/Severe2 Severe: rapid permea- Slight Slight Severe: 5 to 10 percent Severe: rapid permea- Severe: rapid permea-
b i I ity; 5 to 10 percent 'slope. bility. 3 bility.3
slope.

See footnotes at end of table.

low

TABLE I (continued)

Degree and Kind of Limitation for-
Foundations for Houses of Three
Stories or Less- Sites for Sanitary Landfills
Soil Series and Disposal Field For Streets and
MaRSymbols Septic-tank System Sewage Lagoonsi Without Basements With Basements Parking Lot Trench Method Area Method
Rutlege: Fly Severe: high water Severe: rapid permea- Severe: high water Severe: high water Severe: high water table. Very severe: high water Severe: high water table;
table.3 bility.3 table. table; wet excava- table; rapid permea- rapid permeability.3
tions unstable. bility.3
Sassafras:
SaA, SfA Slight Moderate: moderate Slight Slight Slight Slight Slight
permeability.
SaB, SfB Slight Moderate: moderate Slight Slight Moderate: 2 to 5 percent Slight Slight
permeability; 2 to 5 slope.
percent slope.
SaC2 Slight Severe: 5 to 10 percent Slight Slight Severe: 5 to 10 percent Slight Slight
slope. slope.
SaD Moderate: 10 to 15 Severe: 10 to 15 per- Moderate: 10 to 15 Moderate: 10 to 15 Severe: 10 to 15 percent Moderate: 10 to 15 Moderate: 10 to 15
percent slope. cent slope. percent slope. percent slope. slope. percent slope. percent slope.
Swamp: Sw Very severe: ponding. Very severe: ponding. Very severe: ponding. Very severe: ponding. Very severe: ponding. Very severe: ponding. Very severe: ponding.
Tidal marsh: Tf, Tm Very severe: tidal Very severe: tidal Very severe: tidal Very severe: tidal Very severe: tidal Very severe: tidal Very severe: tidal
flooding. flooding. flooding. flooding. flooding. flooding. flooding.
Woodstown: Wo, Ws Moderate: moderately Moderate: moderate Slight Moderate: moderately Moderate: moderately Severe: moderately Moderate: moderately
high water table. permeability. high water table. high water table. high water table. high water table.

It is assumed that any surface layer or other horizon that contains appreciable amounts of organic
matter will be removed and that the floor of the Lagoon will be constructed on the least permeable
layer in the profile. if it is constructed on a more permeable layer, the limitation will be greater.
2 The slight limitation shown here is merely a rating of the ability of the soil to carry away septic
tank effluent. The use of these soils for septic tanks would present only minor problems at very
low, rural densities as long as wells or streams are not located nearby. The use of these soils for
subdivisions, however, presents severe problems with regard to pollution of nearby wells, springs,
ponds, streams or other sources of water.

3 Probability of polluting nearby wells, springs, ponds, streams, or other sources of water.

hand, if these hazards are recognized, utility extensions
into these areas may not be cost effective due to the limited
development potential of the land.

Figure 3,conversely, shows those areas that are suitable for
development with provision of public services, such as central
sewer and'water. The soils shown here are those rated as having
slight limitations for houses without basements. Some of these
soils have moderate limitations for houses with basements, due to
minor water table problems, but they can be overcome, as long as
they are recognized and properlydealt with.

RESIDENTIAL DEVELOPMENT WITH ON SITE SOIL ABSORPTION SEWAGE
DISPOSAL

The successful use of the soil for on-site absorption sewerage
systems is dependent on the ability of the soil to remove
harmful substances and transmit sewage effluent. The relative
amelioration of substances harmful to human and animal life by
reduction of bacteria and filtering is the basis for determin-
ing the limitations of soils,for septic tank filter fields.
Until recently the operation of septic tanks and septic tank
filter fields was considered successful if the soil transmitted
effluent away from the soil surface. With increaseduse of
septic tanks.in lieu of public sewerage systems in many urban
expansion areas or in resort areas near bays and streams, it has
been found that rapid passage of sewage effluent through the
soil contributes to pollution of ground water. Conversely,
very slow movement of effluent through the soil will result
in saturation of the soil. The effluent ponds on the soil
surface or flows across it and eventually enters and pollutes
surface waters. In either event, the presence of effluent on
the surface of the soil causes a- public nuisance and is hazard-
ous to the public health. The danger of ground water contamina-
tion where,sandy,.rapidly permeable soils are used for septic
tank filter fields is recognized as a severe limitation for
residential subdivisions or commercial establishments. This
is particularly important where housing concentrations using.
septic systems also obtain their drinking water from on-side
or nearby shallow wells. A case in point is the Coverdale
Crossroads area near Millsboro, where nitrate and bacteriological
contamination of drinking water has been measured.

Slow or very slow permeability is also considered.a severe or very
severe limitation because most households produce more effluent
than this kind of soil can transmit. The moderate and moderately
rapid permeability classes impose a slight limitation for sewage
disposal'because effluent is transmitted rapidly enough to prevent

surface flow.but slow enough to remove harmful substances
by filtering. This is not always the case, however, when
large concentrations of houses are involved. In the Moores
Lake area of Kent County there is a group of about 100 homes
on half-acre lots. These homes are located on Sassafras soils
which are rated as having slight limitations for septic systems.
There is no public water system, so they must depend upon individual
on-site shallow wells located in the same geologic horizon as the
septic tank tile fields. Well water sampling was conducted by
the State in 1971 as a result of reports that nitrate concentrations
double and treble the drinking water limits had been recorded
by private laboratories. The State confirmed these findings and
noted that higher nitrate concentrations were found downslope
topographically and hydrologically from the lower concentrations.
Furthermore, it is very likely that the concentration of nitrate
in ground water from wells constructed in permeable sands overlain
by Sassafras and similarly well-drained soils is cyclic and
dependent upon an absence of diluting rainfall during the
summer dry period when the downward percolation of rain water is
least and water tables fall (June through August). Any ground
water withdrawn by means of wells is simply returned to the
water table after use by means of the septic system, thus,
constantly building up the nitrate concentration. An additional
hypothesis to be made regarding the contamination of water
supplies in areas where soils and underlying sediments are very
permeable is that pesticides, herbicides, fungicides and
fertilizers applied to lawns and plants, particularly in the
vicinity of.s.hallow wells, could pose an even greater health
threat than the nitrates.

The State study concluded that the practice of constructing wells
and septic tanks in the same geologic horizon, regardless of the
Soil Conservation Service septic tank rating, should be abandoned,
particularly in crowded urban and suburban areas. Moreover, it
was concluded that the percolation test alone did not seem to be
adequatefor evaluating the effectiveness of septic tank systems.

Figure 4 is a map depicting soils with a high potential for
ground water contamination from the disposal.of solid or'liquid
wastes. Soils in Classification I are those with very high water
tables. Septic tanks located in these areas will not function
during most of the year because the tile field is usually below
the water surface. Since there is no place for the effluent to
drain, it rises to the surface and ponds or runs off into the
nearest stream. Such conditions create hardships for homeowners,
as well and they are often required to,pump their septic tanks
out every few weeks. Moreover, such conditions create pressures
for the extension of public sewer and water systems, often over
great distances and expense to the general taxpayer. Prohibition
of on-site sewage disposal systems in such areas would be more
prudent, but to date few efforts have been made to do this.

Soils in Classification II present a more serious problem
because-they pass the percolation test; the widely used
method to determine the soil's ability to drain septic tank
effluent. In these areas, however, the percolation test is
not adequate, because the soils are too permeable. Effluent,
therefore, is passed-relatively unfiltered into the ground
water and creates contamination problems. The location of
septic tank developments in these areas will Also generate
personal and public hardships. Furthermore, depending upon
the extent of the contamination, it may take years or even
decades for the polluted water to be purged from the ground.
In the meantime this ground water is unavailable for public
or private supply.

Scattered houses at rural densities would not pose any,serious
problems as long as wells were located at a proper distance
from the septic tank to provide for effluent dilution or
drilled to a much deeper geologic strata. Subdivisions using
on-site disposal systems should be prohibited on these.soils.

Floodplain and marsh soils (not shown in Figure 4) are also
unsuitable for septic tanks due to slow permeability and high
water table. Enterprising developers and misinformed public
officials often believe that by simple filling, low-lying
wetlands can be made suitable for soil absorption sewage disposal
systems. This is a dangerous misconception, however. The most
common practice for development in marshland in Sussex County
is lagoon construction, where dredge spoil derived from the
lagoons is placed on the marsh surface to create fast land.-
The dredged material is usually the same type of soil and
possesses the same poor drainage characteristics as the marsh
itself. Septic systems installed under these Conditions are
almost certain to fail. In other instances "clean fill" is
brought in from another area and used to create fast land.
The.problemi of a poorly permeable subsoil remains, however, and
effluent will either rise to the surface or flow laterally
into the surface water. (For further information on the
adverse effects of filling, see Working Paper #9).

Some land developers also suggest larger lots when the capability
of a soil to handle sewage effluent is questionable. Larger
lots,however, will not in themselves ensure the proper operation
of soil absorption sewage disposal systems if the soils covering
the lots are unsuited to the proper operation of the system..
Often, "solutions", such as filling and larger lot sizes, are
only temporary in nature since the basic problem of-poor permeability
or high water@table remains and causes systems to fail after a
relatively short period of operation. Rather than attempting to
seek ways to.make soil absorption disposal systems temporarily
operable in such areas, local public officials should seek to
prevent the installation of systems on unsuitable soils and
encourage furture urban growth to take place in such areas only
if public sanitary sewer service can be provided.

LANDFILLS

One method of solid waste disposal is the sanitary landfill.
It is defined as a method of disposing of refuse on land with-
out creating nuisances or hazards to public health or safety by
utilizing the principles of engineering to confine the refuse
to the smallest practical volume, and to cover it with a layer
of earth at the conclusion-of each day's operation, or at such
more frequent intervals as may be necessary.
Ideally, the sanitary.landfill should conform to four ba@ic
requirements. These are:

1. The lowest point of the excavation should be twenty
to thirty feet above the shallowest aquifer (water-bearing zone)
at thehigh water point during the wet season.

The site should not be subject to flooding.

2. The site should be located in slowly permeable
material, such.as clay.

3. Refuse should be compacted and covered.daily with
at least 6 inches of medium-textured material. This soil,
or other suitable material, should be as impermeable as
possible.and should not crack on drying.

4. The site should be geologically and geographically
isolated from water wells, lakes, streams or any other body
of water.

These, of course, are the requirements for the ideal.
Sanitary Landfill, In more cases than not, however,
it is impossible to find a site that.fulfills them all.

Theentire surface area of Delaware's Coastal Plain is considered.
a source.6f,.aquifer recharge, and the surface streams which
originate on the Coastal Plain depend upon aquifer-supplied
groundwater for 75-90 percent of their flow. Obviously@, any
material that, is put onto the surface or into the soil must be
examined for possible pollution dangers to one of Delaware's
most abundant natural resources, its groundwater. Once an
aquifer is,contaminated, it is often difficult or impossible
to restore its purity.

Until recently, an evaluation of geologic and hydrologic conditions
was rarely.included among the various considerations that '
determined site selection for landfills in Delaware. Thus,
one environmental hazard created by past refuse disposal practices

is the possible effect on ground water quality. Existing
landfills or dumps invariably were placed on land that had
little or no value for other uses. The site chosen was located,
for example, in a marshland or an abandoned sand and gravel pit,
each of which is a favorable environment for the development of
ground-water..c,ontamination problems.

Landfills in the region are receiving a.wide variety of materials
including paper products, food wastes, septic-tank sludge,
demolition debris, tires, automobiles, leaves, plastics, textiles,
glass, aluminum cans, liquid chemicals, oils and hydrocarbons,
street sweepings, dead animals, and water and waste-water treatment
sludge. In municipal refuse, paper and paper products make up
the major category by weight.

The processes.that can lead to contamination of ground water
from the disposal of wastes in landfills are relatively simple.
The various organic compounds in refuse (with,the exception of
most plastics) are decomposed or stabilized by aerobic and
anaerobic organisms to simple substances that will decompose
no further. These products of decomposition include gases and
soluble organic and inorganic compounds. If sufficient water
is available from precipitation, or from surface drainage in
contact with the refuse, these compounds can be dissolved and
carried with the water that infiltrates the landfill and ultimately
recharges the ground-water reservoir or discharges into adjacent
surface-water bodies.

Solid inorganic refuse, such as tin cans and metal pipes, can
also be slowly dissolved by percolating waters, resulting.in a
solution with'an increased concentration of metallic ions. Finally,
disposal of liquid industrial wastes, septic-tank pumpings, and
waste-water treatment sludges, can contribute to an overall
increase in dissolved solids concentration of water pas.sing
through the@landfill. The term "leachate" has been applied to
highly contaminated water contained in or directly associated
with a refuse disposal site.

The concentration-of chemical and biological pollutants travelling
through soil decreases with 'distance from.the landfill.,. The
effectiveness, however, of such processes as adsorptionjon
exchange, dispersion, or dilution varies considerably with the
type of pollutant involved, the characteristics of the soil
underlying thelandfill, and geologic and hydrologic conditions
at the site. Thus, no broad generalizations can be made.
The volume of 'leachate developed by any particular landfill is
a function of its absorptive capacity and areal extent, and
the amount of recharge water available for infiltration. Most
landfills assume a relatively flat surface with no vegetation,
which is more conducive to infiltration than to runoff and
evapotranspiration (a combination of surface evaporation and the
removal of soil moisture by plants)., They are normally.covered
with a relatively coarse-grained material, again increasing
infiltration efficiency. Therefore, it is reasonable to assume

that at least one-half of the annual precipitation can become
recharge to the ground-water reservoir, after it has come in
contact with the solid waste contained in the landfill. Average
annual rainfall in the region is 42 inches per year. Thus, a.
100-acre site would be capable of producing 57 million gallons
of leachate per year after field capacity of the refuse has been
reached.

Research on the question of how long after abandonment a landfill
can be expected to generate leachate has been minimal. However,
one investigation under a grant from the U.S. Public Health
Service to the Pennsylvania Department of Health sheds some light
on this question. A study was made of a landfill in southeastern
Pennsylvania, part of which had been closed in 1950 but was still
producing leachate.

In 1972 geology students at the University of Delaware conducted
a survey of landfill practices at nine locations in Delaware,
five of which were in Sussex County. The study found leachate
seepage at all sites and concluded that there was imminent. danger
of groundwater pollution at each site observed due to the high
water table levels and permeable nature of the Coastal Plain
soils in which they are located.

The most serious example of leachate contamination of groundwater
in Delaware is occurring in New Castle County near Llangollen.
Between 1960 and 1968 solid waste was deposited in an old sand
and,gravel pit near the intersection of Routes 40 and 13.
Apparently unknown at the time, the landfill was located on the
outcrop of the.Potomac aquifer, northern Delaware's most
important source of groundwater. Water moving through the
aquifer came.in contact with the bottom of the landfill. This.
and precipitation percolating through the waste created large
volumes of contaminated water which first appeared in a domestic
well south,of the landfill in 1972.

During the 1960's major wells were'developed in this aquifer
approximately 3,000 to 4,000 feet south and east of the land-
fill.by Artesian Water Company and Amoco Chemical Corp. Without
prIompt action, the 16achate would have reached these wells and
contaminated them. This would have resulted in loss of the most
productive aquifer in the State--capable of producing 6..5 million
gallons per day.

A counter.pumping program@close to the landfill to remove the
contaminants and reverse the direction of contaminant,mov,emen.t
away from the well field was initiated. The polluted water is
now being discharged directly into Army Creek.

Eventually, the entire landfill will be removed to a site
specially.designed to accept the waste. The cost will be
between six and eight million dollars.

As a result of this experience Delaware now has regulations
governing landfill practices and designed to eliminate potential

leachate problems so that situations like this do not occur
again.

.Figure 4 shows those soils especially unsuited for landfills.

PRIME AGRICULTURAL LAND

Soil surveys can be used as a guide to the suitability of
soils for cropland, the kind of crops the soils can support,
and the management needed to maintain their productivity1from
year to year. To simplify the information being collected and
to promote understanding of soil problems, a system of land
capability groupings was devised. The system is basedon the
limitations of soils for use as cropland. Yield information
and woodland suitability groupings also aid in determining the
best agricultural use for soils. Drainage and irrigation guides
are helpful in solving problems of excess water or ina'dequatd@
water supply.

CAPABILITY GROUPS OF SOILS

The soils of Sussex County have been classified into capability
groupings that indicate their general suitability for most kinds
of farming. These are practical groupings based on limitations
of the soils, the risk of damage when they are used, and the
way they respond to treatment. In this system all soils are,
grouped at three levels: the capability class, subclass, and
unit. The eight capability classes in the broadest grouping
are designed by roman numerals I through VIII. In Class I are
the soils that have few limitations, the widest range of use,
and the least risk of damage when used. The soils in the.other
classes haveprogressively greater natural limitations. In
Class VII are soils and land forms so wet, sandy or otherwise
limited that they do not produce economically worthwhile yields
of crops, forage, or wood products.

The subclasses indicate major kinds of limitations within the
classes. Within most classes there are up to threesubclasses.
The subclass is indicated by the addition of-a lower case letter,
e, w. or s, to the class numeral, for example,IIe. The
letter "e" indicates that the main limitation to the use of the
soil for cultivated crops is risk of erosion; "w" indicates.that
water in or on' the soil will interfere with plant growth or
cultivation (in some soils the wetness can be partly corrected
by artificial drainage); and, "s" indicates that use of the
soil.for cultivated crops is restricted because it is shallow,
droughty, stony or has some other soil induced limitation.

Each subclass is further divided into capability units. These
consist of groups of soils that are very similar and, therefore,
suited to the same kind of crop and pasture plants, require
similar management, and have similar productivity and other
responses to management. Thus, the capability unit is a con-
venient grouping of soils for management purposes. Capability
units.are identified by the addition of an arabic numeral code

to he class and subclass code, for example, IIe-l or IIIe-2.
t

Soils are classified in capability classes, subclasses and units
in accordance with the degree and kind of their permanent limita-
tions, but without consideration of major and generally expensive
land-forming practices that would change the slope, depth or
other characteristics of the soil and without consideration of
possible but unlikely major reclamation projects. Most of the
deep, well-drained, moderately permeable loamy soils are..
classified as Class I where they are nearly level. Sloping
soils are susceptible to erosion because of runoff. The erosion
hazard is primarily related to steepness of slope, and the
soils are classed accordingly. Slowly permeable and very
slowly permeable soils generally restrict root growth and are
poorly aerated in the lower part of the soil. This restriction
is considered a soil or "s" factor. Other soils have low
available water capacity and are subject to wind erosion or
droughtiness. Most wet soils with high water tables have neither
an erosion hazard nor available water deficiency, but the
excess water deprives plant roots of oxygen.

The eight classes in the capability system and the subclasses
and units in Sussex County are described, in the list that .
follows. The units are not numbered consecutively within the
subclasses, because they fit into a.Statewide system,of.capability
classification and not all the capability units in the State are.
represented in this county.

CLASS I: Soils have few limitations that restrict their use
(no subclasses)

Capability unit 1-4. Deep, well-drained, moderately
permeable, nearly level soils that have a loam surface
layer and a high available moisture capacity.

Capability unit 1-5. Deep, well-drained, moderately
permeable, nearly level soils that have a sandy loam
surface layer and a moderate to high available moisture
capacity.

CLASS II: Soils have moderate limitations that reduce the
choice of plants or that require moderate conservation
practices.

Subclass IIe: Soils subject to moderate erosion unless
protected.

Capability unit IIe-4. Deep, well-drained, moderately
permeable, gently sloping soils that have a loam surface
layer and a high available moisture capacity.

Capability unit Ile-5. Deep, well-drained,moderately
permeable, gently sloping soils, that.have a sandy loam
surface layer and a high available moisture capacity.

Subclass IIw: Soils moderately limited because of
excess water.

Capability unit IIw-l. Moderately well drained,
moderately permeable, nearly level soils that have a
loam surface layer and a high available moisture
capacity.

Capability unit IIw-5. Moderately well drained,
moderately permeable, nearly level soils that have
a sandy loam surface layer and a high available-
moisture capacity.

Capability unit IIw-9. Moderately well drained,
slowly permeable, nearly level soils that have
a fine sandy loam surface layer and a high available
moisture capacity.

Capability unit IIw-10. Moderately well drained,
slowly,permeable, nearly level soils that have a
thick sandy loam surface layer and a high available
moisture capacity.

Subclass Ils- Soils moderately limited by droughtiness.

Capability unit IIs-4. Deep, well drained to somewhat
excessively drained, moderately rapidly permeable,
nearly level and gently sloping soils that have a loamy
sand surface layer and a low to moderate available
moisture capacity.

Capability unit IIs-5. Deep, moderately well drained
to well drained, slowly permeable, nearly level soils
that have a thick loamy sand surface layer and a moderate
available moisture capacity.

CLASS III: Soils have severe limitations that reduce the
choice of plants, require special conservation practices, or
both.

Subclass IIIe: Soils subject to severe erosion if they are
cultivated and not protected.

Capabi lity unit IIIe-5. Deep, well drained, moderately
permeable, moderately sloping, eroded soils that have a
sandy loam surface layer and a high available moisture
capacity.

Capability-unit IIIe-33. Deep, somewhat excessively
drained, rapidly permeable, moderately sloping soils
that have a loamy sand surface layer and a low to
moderate available moisture capacity.

Subclass IIIw: Soils severely limited for cultivation
because of excess water.

Capability unit IIIw-6. Poorly drained and very poorly
drained, moderately permeable soils that have a sandy
loam surface layer and a moderate to high available
moisture capacity.

Capability unit IIIw-7. Poorly drained and very poorly
drained, moderately permeable soils that have a loam
surface layer and a moderate to high available moisture
capacity.

Capability unit IIIw-9. Poorly drained, slowly
permeable soils that have a sandy loam surface layer
and a high available moisture capacity.

Capability unit IIIw-10. Moderately well drained to
somewhat poorly drained, rapidly permeable soils that
have a loamy sand surface layer and a low available
moisture capacity.

Capabil ity unit IIIw-11. Poorly drained, slowly
permeable soils that have a loam surface layer and
a.high.available moisture capacity.

Subclass IIIs: Soils severely limited for cultivation
by droughtiness.

Capability unit IIIs-'l. Excessively drained, rapidly
permeable, nearly level and gently sloping soils that
have a loamy sand surface layer and a low available
moisture capacity, but have a moisture-retarding layer
at some depth.

CLASS IV: Soils have very severe limitations that reduce the
choice of plants, require very careful management, or both.

Subclass IVe: Soils subject to very severe erosion if they
are cultivated and -not protected.
Capability unit IVe-5. Deep, well drained,:moderately
permeable, strongly sloping soils that have a sandy loam
surface layer and high available moisturecapacity.

Capability unit IVe-9. Moderately well drained,
slowly permeable, gently sloping, eroded soils
that have a fine sandy loam surface layer and a
high available moisture capacity.

Subclass IVw: Soils very severely limited by excess,
wetness.

Capability unit IVw-6. Poorly drained and very poorly
drained, moderately rapidly permeable to

to rapidly permeable soils that have a surface
layer of loamy sand and a low to very low available
moisture capacity.

Capability unit IVw-7. Very poorly drained,
organic soils that are subject to ponding.

CLASS V: Soils are not likely to erode but have other
limitations,,impractical to remove, that limit their use
largely to pasture, woodland, or wildlife. (None in Sussex
County.)

CLASS VI: Soils have severe limitations that make them
generally unsuited to cultivation and limit,their use largely
to pasture, woodland, or wildlife. (None in Sussex County.)

CLASS VII: Soils that have very severe limitations that
make them unsuited to cultivation and that restrict their
use largely to pasture, woodland, or wildlife.

Subclass VIIw: Soils very severely limited by excess
water.,
Capability unit VIIw-1. Ver'y poorly drained soils on
flood plains and very wet, unclassified soils materials,
more or less continually flooded or ponded.

Subclass VIIs: Soils very severely limited by low
available moisture capacity, stones, or other soil
features.

Capability unit VIIs-1. Excessively drained, rapidly
permeable, gently sloping to strongly sloping soils that
have a loamy sand and sand surface layer and a very low
available moisture capacity.

CLASS VIII:. Soils and landforms have limitations that pre-
clude their use for commercial crop production and restrict
their use to recreation, wildlife, or water supply, or to use
for esthetic purposes.

.Subclass VIIIw: Extremely wet, marshy land.

Capability unit VIIIw-1. Marsh lands that are subject
to tidal flooding.

Subclass VIIIs: Stony land, coastal beaches, and other
areas that have little potential for commercial crop
production.

Capability unit VIIIs-2. Loose, incoherent sands of
beaches and dunes.

Capability unit VIIIs-4. Land where large amounts of
soil material have been removed.

Table 2 shows the agricultural capability rating for soils in
Sussex County.. It is apparent that both actual and potential
prime farmland may be recognized. Actual prime farmland is
land with qualities that permit it to be used for.farming with
no special treatment other than clearing of trees, or seedbed
preparation. Sussex County lands in this category fall into
capability groups I and He and are noted in Table 2. Potential
prime farmland, in contrast, is not prime in its natural condition.
This is usually because it is too wet or too dry. To move it
to the prime class requires expensive and sometimes difficult
alteration of soil climate by providing irrigation or drainage.
Potential prime, farmlands in need of drainage are in capability
groups IIw-l, IIw-5, IIIw-6, IIIw-7, and IIIw-10. Those in need
of irrigation are in capability groups IIs-4 and IIIs. Figure
5 shows the areal extent of natural and potential prime agricultural
land in the Lewes CCD.

If one compares the prime agricultural lands (Fig. 5) with the
lands suitable for development (Fig. 3) it is apparent that the
best soils for food and fiber production and also good for
housing and other types of urban use. Gradually other uses
hve preempted substantial areas of farmland, because farming
rarely, if ever, withstands the economic pressure that can be
applied by its competit ors in the land market.

These soils maps provide the basis upon which local decision
makers can evaluate the urban expansion consequences that result
from utility location and design and their effects on agricultural
land preservation.

SUMMARY

Serious health, safety, and pollution problems may be caused
by failure to take the capabilities and limitations of soils
into consideration during the planning stage of any urban or
rural development proposal. Such problems are usually very
costly to correct and may create personal hardship out of all
proportion to the. relatively simple steps required to avoid them.
Such problems include malfunctioning on-site soild absorption
sewage disposal (septic tank) systems, flood damages,.footing
and foundation failures, soil erosion and sedimentation, and
land@fill leachate. Moreover, corrections of these problems,
once they occur, may entail great public, as well as private
expense and may cause personal aggravation and inconvenience.
Knowledge of t'he soil resource and its ability to sustain
development can not only,help.in avoiding such problems, but
can also contribute to avoiding or reducing excessive land
development costs.

TABLE 2

AGRICULTURAL CAPABILITY

Map Capability
Symbol Mapping Unit Unit
(Symbol)

Bd Berryland loamy sand IVw-6
Bo Borrow pits VIIIs-4
Co Coastal beach and dune land VIIIs-2
El Elkton sandy loam IIIw-11
Em Elkton loam IIIw-9
EoB Evesboro sand, 0 to 5 percent slopes VIIs-1
EoD Evesboro sand, 5 to 15 percent slopes VIIs-1
EsD Evesboro loamy sand, 5 to 15 percent slopes VIIs-1
EvA Evesboro loamy sand, loamy substratum, 0 to 2
percent slopes IIIs-1(I)
EvB Evesboro loamy sand, loamy substratum, 2 to 5
percent slopes IIIs-1(I)
Fa Fallsington sandy loam IIIw-6(D)
Fs Fallsington loam IIIw-7(D)
Ft Fill land ----
Jo Johnston silt loam VIIw-1
Ka Kalmia sandy loam I-5(N)
KbA Kenansville loamy sand, 0 to 2 percent slopes IIs-4(I)
KbB Kenansville loamy sand, 2 to 5 percent slopes IIs-4(I)
KfA Keyport fine sandy loam, 0 to 2 percent slopes IIw-9
KfB2 Keyport fine sandy loam, 2 to 5 percent slopes,
eroded IVe-9
Kl Klej loamy sand IIIw-10(D)
Mn Matawan loamy sand IIs-5
Mn Matawan sandy loam IIw-10
Mu Muck, shallow IVw-7
Os Osier loamy sand IVw-6
Pm Pocomoke sandy loam IIIw-6(D)
Pt Portsmouth loam IIIw-7
RuA Rumford,loamy sand, 0 to 2 percent slopes IIs-4(I)
RuB Rumford loamy sand, 2 to 5 percent slopes IIs-4(I)
RuC Rumford loamy sand, 5 to 10 percent slopes IIIe-33
Ry Rutlege loamy sand IVw-6
SaA Sassafras sandy loam, 0 to 2 percent slopes I-5(N)
SaB Sassafras sandy loam, 2 to 5 percent slopes IIe-5(N)
SaC2 Sassafras sandy loam, 5 to 10 percent slopes,
eroded IIIe-5
SaD Sassafras sandy loam, 10 to 15 percent slopes IVe-5
SfA Sassafras loam, 0 to 2 percent slopes I-4(N)
SfB Sassafras loam, 2 to 5 percent slopes IIe-4(N)
Sw Swamp VIIw-1
Tf Tidal marsh, fresh VIIIw-1
Tm Tidal marsh, salty VIIIw-1
Wo Woodstown sandy loam IIw-5(D)
Ws Woodstown loam IIw-l(D)

(N) Prime agricultural land in its natural state.
(I) Prime agricultural land with irregation.
(D) Prime agricultural land with drainage.

11
-1 3 6668 14109 7891
r