TM 5-814-7
(2) Sedimentation controls should be established
areas and active disposal units should be confined, and
for onsite borrow areas and construction areas. Where
operations effectively controlled, to enable collection and
possible, facilities for control of sediment transport
retention of the minimum volume of run off which may
should be located near the source, so that only
best be treated for release, or discharged back to an
sediment-laden waters need be handled. The near-
approved hazardous waste facility.
source system requires less extensive structures than
(2) The conveyance systems developed to carry
the downstream sedimentation control basin alternative
run off from active areas of waste units, and the retention
for intercepted run-on flows.
facilities developed to contain run off, must prevent any
(3) Sediment control facilities for source areas
release of liquid. Closed pipes or ditches with synthetic
include:
liners should be considered for waste piles and landfills.
(a) Temporary Sediment Basins-At construction
(3) Conveyance systems within land treatment
units may include unlined terraces and grass waterways
areas, where run off is usually confined to ditches or
for both application of liquid waste, and for intercepting
depressions in the topography, basins can be
flows and minimizing erosion within the land treatment
constructed by excavating shallow depressions and
area.
placing berms or sandbags to contain water for
(4) Retention facilities designed for all waste
sedimentation.
(b) Silt Barriers-Where sheet flow occurs (on
units should meet either storage or surface
impoundment requirements. However, a lower area of
perimeter construction slopes, and in large excavations),
either waste unit might be developed and used for the
silt fences or hay bales placed in a shallow trench can be
retention and treatment of run off from active areas. The
positioned to intercept run off and remove sediment. Silt
adequacy of the retention basin size should be
fences normally consist of filter cloth fastened to wire
demonstrated, based upon a monthly tabulation of run-
fencing.
(c) Vegetation-Completed borrow areas, inactive
off storage requirements, and the methods for emptying
the basins and dispersing of the accumulated waters,
stockpile areas, and final cover areas can be seeded,
(i.e., treatment and discharge, evaporation, spray
fertilized or hydroseeded to establish a vegetative cover
irrigation, solidification, etc.).
which will provide erosion and sediment control. When
(5) Procedures which may be required to
vegetation has become established, downgradient silt
minimize the active area from which run off must be
fences or other sedimentation control structures may be
collected could include internal berms, synthetic cover,
removed.
encapsulated wastes, and restrictions during wet-
(4) Sedimentation control basins (figure 6-9),
weather periods.
used for settling out sediment being carried by surface
e.
Sizing run-on/run-off control systems.
flows, are often established at discharge locations by
Methods used to predict run-off volumes and peak flow
constructing containment dikes and excavating a basin
rates include the Rational Formula, empirical
area. To discharge surface water, emergency overflow
expressions and charts of the USDA's Soil Conservation
spillways and pipe drains are typically provided.
Service (SCS), and various hydrographic procedures.
(5) The principal maintenance requirement for
Both the Rational Formula and the SCS charts provide
sedimentation basins is removal of accumulated
predictions which can be used in sizing surface water
sediment by draglines or loaders during dry-weather
control systems at disposal facilities.
periods.
(eq 6-1)
d. Run-off control systems. Run-off control
(1) For the Rational Equation: Q = CiA
systems which handle surface water flows from active
where: Q = flow rate (cfs)
portions of hazardous waste units and any site staging
C = run-off coefficient (assumed)
areas that might contain wastes residue must include
i =intensity of rainfall
collection and holding facilities (figure 6-9). These
(inches/hour) for the selected
facilities retain run off for treatment before its release,
design duration and frequency
evaporation, or discharge back to an approved
A = tributary area, in acres
hazardous waste facility.
(2) The value of C for sizing run-off control
(1) For large sites located in semi-arid regions, collection
systems should be 0.8 to 1.0 when the active areas are
and holding facilities might be developed to receive run
barren or lined. The same factor should also be used to
off from the majority of the site, rather than specific
determine the volume of run off into holding facilities over
waste units. Such facilities could easily be sized to retain
the specified period of time. Run-off coefficients for
and effect evaporation of run-off volumes much larger
other surface conditions applicable to land disposal
than those from the required 24hour, 25-year storm,
facilities are available in TM 5-820-4.
ensuring full containment while minimizing operational
(3) The SCS method provides empirically based
requirements. For sites located in more humid areas,
the
immediate
waste
handling
6-19
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