ETL 1110-1-163
30 Jun 96
B-2. Predesign Investigations
(5) Horizontal and vertical control. At a mini-
mum, three permanent control monuments need to be
established. The monuments should be strategically
a. General. Prior to preparing a design analysis
located so that they are not damaged during construc-
or plans and specifications for any type of vertical
tion. All monuments should be assigned state plane
barrier wall, it is necessary to conduct predesign
coordinates and/or tied into the horizontal grid used
surveys and investigations to fill data gaps. The
in previous studies. The vertical datum should be
existing database available from the remedial investi-
mean sea level, North American Datum of 1983.
gation (RI), feasibility study (FS), and other docu-
ments must be reviewed before scoping a predesign
(6) Monitoring baseline survey. To monitor
effort. The following information is often required in
design concerns, it is necessary to perform surveys to
the design of a vertical barrier wall.
establish a baseline for monitoring wells, piezometers,
and other instrumentation.
b. Field surveys and record searches.
(7) Utilities. All onsite above and below ground
(1) Aerial photography. Historic aerial photo-
utilities should be identified, located, and subse-
graphs can be used to preliminarily define the nature
quently shown on the project drawings. A utility
and extent of contamination at a site. The principal
search should consist of an onsite inspection, review
sources of aerial photographs are the U.S. Department
of as-built drawings, and contacts with utility com-
of Agriculture (USDA) Agricultural Stabilization and
panies. The project drawings should show the loca-
Conservation Service (ASCS) and the U.S. Geologi-
tion of onsite utilities including horizontal alignment,
cal Survey (USGS).
depth or height, type, and size.
(2) Design and operational data. Design and
(8) Boundary survey and property search. A
operational information such as as-built drawings,
boundary survey should be performed for all proper-
specifications, and design analyses may help in iden-
ties or parcels within project construction or access
tifying the nature and extent of contamination.
limits. The boundary survey should be tied to the
However, documents such as these are rarely avail-
site's horizontal control. A property search should
able for hazardous waste sites.
also be performed to identify property owners of all
affected and adjacent parcels of land. Prior to any
(3) Map database. The USGS, USDA, and other
investigation or construction activity, it is essential to
government agencies produce topographic, soils,
obtain construction easements and project rights-of-
groundwater, and other mapping that may be useful
way. This may take 12 to 18 months; therefore,
in the design of a vertical barrier wall.
coordination with real estate specialists should begin
as soon as possible.
(4) Topographic surveys. A current topographic
survey of the site is required. To allow for manipula-
c. Geological investigations. After the existing
tion of data and to expedite the design process, the
database has been reviewed, geological investigations
topographic survey should be mapped on a computer
can be scoped. The following items need to be
aided design and drafting (CADD) system. Ideally,
investigated in order to design a vertical barrier wall
topographic mapping will have 300 mm (1 ft) contour
system.
intervals. However, larger contour intervals may be
acceptable depending on site-specific conditions (e.g.,
(1) Limits of waste. The limits of the contami-
time, budget, and topography). Topographic mapping
nated area the vertical barrier wall will surround need
should be accurate to within 30.0 mm ( 0.1 ft) in
to be defined. Depending on the type and composi-
the vertical and horizontal directions. Elevations of
tion of the waste, the limits can be tentatively
piezometers, monitoring wells, or other instrumenta-
defined by geophysical methods such as electromag-
tion should be accurate to 3.0 mm ( 0.01 ft) to
netic conductivity surveys and soil gas surveys.
allow for accurate interpretation of data. All surface
Intrusive methods such as test pits, borings, and mon-
features such as buildings, utilities, ponds, fences,
itoring wells will also need to be used to verify the
trees, streams, ditches, and exploratory borings and
boundaries of the contaminated area. All test pits and
trenches should be delineated on the mapping.
B-2
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