B Liquid and slurry waste storage

Liquid and slurry manure can be stored in waste storage ponds or in aboveground or below-ground tanks. Solids separation of manure and bedding is a problem that must be considered in planning and design. Solids generally can be resuspended with agitation before unloading, but this involves a cost in time, labor, and energy. Another option allows solids to accumulate if the bottom is occasionally cleaned. This requires a paved working surface for equipment.

Earthen storage is frequently the least expensive type of storage; however, certain restrictions, such as limited space availability, high precipitation, water table, permeable soils, or shallow bedrock, can limit the types of storage considered.

Storage ponds are earthen basins designed to store wastewater and manure (figs. 10-14, 10-15, 10-16). They generally are rectangular, but may be circular or any other shape that is practical for operation and maintenance. The inside slopes range from 1.5 to 1 (horizontal to vertical) to 3 to 1. The combined slopes (inside plus outside) should not be less than 5 to 1 for embankments. The soil, safety, and operation and maintenance need to be considered in designing the slopes. The minimum top width of embankments should be 8 feet; however, greater widths should be provided for operation of tractors, spreaders, and portable pumps.

Storage ponds should provide capacity for normal precipitation and runoff (less evaporation) during the storage period. Appendix 10C provides a method for determining runoff and evaporation volumes. A minimum of 1 foot of freeboard is provided.

Inlets to storage ponds can be of any permanent material designed to resist erosion, plugging, or, if freezing is a problem, damage by ice. Typical loading methods are pipes and ramps, which are described in section 651.1005. Flow of wastes away from the inlet should be considered in selecting the location of the inlet.

Figure 10-14 Cross section of waste storage pond without a watershed

Freeboard (1.0 minimum)

Depth of 25-year, 24-hour storm event on pond surface

Depth of normal precipitation less evaporation on the pond surface accumulated during the storage period

Required volume \ Volume of manure (TVM), clean water (CW)

and wastewater accumulated (TWW) during the storage period

Volume of accumulated solids (VSA) for period between solids removal t

Crest of spillway or other outflow device if used

Pumpdown stake

Figure 10-15 Cross section of waste storage pond with watershed

Freeboard (1.0 minimum)

Depth of the 25-year, 24-hour storm on the pond surface i---(ROV) - -

Required volume

Volume of runoff from the 25-year, 24-hour storm event Volume of normal runoff accumulated during the storage period

Depth of normal precipitation less evaporation on the pond surface accumulated during the storage period

Volume of manure (TVM), clean water (CW) and wastewater accumulated (TWW) during the storage period

Volume of accumulated solids (VSA) for period between solids removal t

Crest of spillway or other outflow device if used

Pumpdown stake

*or other outflow device

Figure lO-l6 Waste storage ponds

Slurry Pipe Ramps

Cross-section earth embankment

Chapter 10 Agricultural Waste Management System Part 651

Component Design Agricultural Waste Management

Field Handbook

Gravity pipes, pumping platforms, and ramps are used to unload storage ponds. A method for removing solids should be designed for the storage pond. If the wastes will be pumped, adequate access must be provided to thoroughly agitate the contents of the pond. A ramp should have a slope of 8 to 1 or flatter and be wide enough to provide maneuvering room for unloading equipment.

Pond liners are used in many cases to compensate for site conditions or improve operation of the pond. Concrete, geomembrane, and clay linings reduce permeability and can make an otherwise unsuitable site acceptable. See Appendix 10D, Geotechnical design and construction guidelines for waste impoundment Liners, for detail on clay liners. Concrete also provides a wear surface if unloading equipment will enter the pond.

Figures 10-17, 10-18, and 10-19 represent various kinds of storage ponds and tanks.

Liquid manure can be stored in aboveground (fig. 10-18) or below-ground (fig. 10-19) tanks. Liquid manure storage tanks can be constructed of metal, concrete, or wood. Below-ground tanks can be loaded using slatted floors, push-off ramps, gravity pipes or gutters, or pumps. Aboveground tanks are typically loaded by a pump moving the manure from a reception pit. Tank loading can be from the top or bottom of the tank depending on such factors as desired agitation, minimized pumping head, weather conditions, and system management.

Storage volume requirements for tanks are the same as those for ponds except that provisions are normally made to exclude outside runoff from waste storage tanks because of the relative high cost of storage. Of course, if plans include storage of outside runoff, accommodation for its storage must be included in the tank's volume.

Tanks located beneath slatted floors can sometimes be used for temporary storage with subsequent discharge into lagoons or other storage facilities. Recycled lagoon effluent is added to a depth of 6 to 12 inches in underslat pits to reduce tendency for manure solids to stick to the pit floor. Wastes are allowed to collect for several days, typically 1 to 2 weeks, before the pits are gravity drained.

Figure 10-17 Layout of waste storage pond

Optional paved bottom (needed if unloaded with bucket/scraper)

Plan

X- Paved j 1' Freeboard

Optional paved pump-out location

X- Paved j 1' Freeboard

Cross section along ramp

Optional paved bottom (needed if unloaded with bucket/scraper)

Plan

Cross section along ramp

Freeboard

—Paved access ramp

Cross section AA

Note: Dimensions and slopes shown for example purposes only.

Chapter lO

Figure 10-18 Aboveground waste storage tank

Figure 10-18 Aboveground waste storage tank

Figure 10-19 Below-ground waste storage structure

Slats

Concrete block walls

Pushoff ramp

Fence

Cast in place or precast concrete walls

Fence

Transfer pipe

Circular cast in place or precast concrete walls

Transfer pipe

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