Waste Facility Construction Requirements

EARTHEN STORAGE POND

Earthen ponds may be constructed with onsite soils which meet the SNTC 716 specification previously mentioned or may be lined with 1' of acceptable soil meeting SNTC 716 (2' separation from ground water, rock or gravel is still required). If only a layer of acceptable soil was found during the soils testing, that material can be set aside for later use as a liner or the liner material may be imported from off-site. Another option is to mix bentonite or other high clay material with the onsite soil to create a soil with the acceptable clay content. The following storage pond requirements are the minimum values allowed by the ISDA (Soil type or site conditions may also warrant using more conservative requirements):

Inside slope of pond shall be 2 horizontal to 1 vertical or flatter. See Figure 2;
Outside slope of pond embankments shall be 3 horizontal to 1 vertical or flatter. See Figure 2;
The top width of the embankment shall be at least equal to the embankment height;
The embankments should have 2' of freeboard above the design water surface level (1' of freeboard is allowed if the winter precipitation falling on the pond is included in the pond sizing);
An armored spillway should be installed in the embankment in case of overtopping;
All surfaces should be compacted to 90% of maximum density - Tracked or tired equipment can usually obtain this level of compaction if soil moisture is appropriate (See page 11 for details of moisture content).

Figure 2. Lagoon Construction Diagram

STORAGE POND WITH SYNTHETIC LINERS

Synthetic liners are very fragile and require stringent quality control during the installation process. These liners cannot withstand any equipment traffic so cleaning and maintenance methods must be developed which will not damage the liner. The material must also be protected from livestock and burrowing rodents with proper management practices. An excellent use for a synthetic liner is on the embankments of an earthen pond with a concrete floor and "bucking walls" in a sandy soil area (see Figure 3). The ISDA has the following minimum requirements for ponds constructed with synthetic liners:

Manufacturer's specifications, installation instructions and the proposed pond design must be submitted to the ISDA for approval prior to beginning the project. A construction inspection schedule will be generated for the project at that time;
Liner should be located 6" above ground water level;
A 6" layer of compacted sand or clean soil should be placed below the liner material;
The liner must be factory-seamed or seamed by a factory authorized contractor if more than a single sheet of liner is required;
A minimum of 1' of soil or sand should be placed over the liner if it is not UV protected;
Inside slope of pond should be 2 horizontal to 1 vertical or flatter - see Figure 2;
Outside slope of pond embankments should be 3 horizontal to 1 vertical or flatter - see Figure 2;
The top width of the embankment shall be at least equal to the embankment height;
The embankments should have 2' of freeboard above the design water surface level (1' of freeboard is allowed if the winter precipitation falling on the pond is included in the pond sizing).

Figure 3: Typical Synthetic Liner Installation Detail

CONCRETE/ASPHALT STORAGE STRUCTURE

Concrete or asphalt ponds are arguably the best type of containment facilities when properly constructed. These facilities can be installed in high ground water areas and in soils not meeting the clay content requirement. There are many different types of concrete/asphalt storage ponds, including; concrete, gunite (concrete swimming pool lining material), or asphalt lined earthen ponds, above ground concrete tanks, below ground concrete vaults and partially buried concrete ponds (vertical walls). Concrete is also an excellent material to use in conjunction with other materials as shown in Figure 4. The following ISDA requirements for concrete/asphalt storage structures are minimums. Site conditions may warrant more stringent construction requirements.

Concrete facilities should be designed or reviewed by an engineer prior to construction
The minimum concrete thickness for reinforced slabs is 5"
Walls and footings must be reinforced with manufactured rebar
Minimum concrete cover over rebar is 1 ½" - Maximum rebar spacing is 18"
Slabs shall have a minimum of 6" of compacted sand or gravel below them
Walls requiring backfill must be backfilled with sand or gravel
Contraction joints must be placed in walls at 40' maximum intervals
Expansion joints must be placed in walls at 100' maximum intervals
All concrete joints must have a waterstop installed (see Figure 4)
Asphalt lined lagoons must have the ground below them sterilized with herbicide prior to construction
Concrete storage facilities do not have a minimum freeboard requirement. However, uncovered concrete storage facilities must be designed to include precipitation on the lagoon surface

Figure 4. Typical Concrete Slab/Wall Joint Showing Waterstop

PRE-MANUFACTURED STORAGE FACILITIES

All pre-manufactured waste containment facilities should be installed and constructed in strict accordance with the manufacturer's recommendations. The foundations for above ground installations should be designed or reviewed by an engineer prior to construction. Below ground installations should also be designed or reviewed by an engineer to prevent crushing or "floating" of the containment facility.

RUNOFF DIVERSION BERMS/CHANNELS

Contaminated precipitation runoff must be diverted to the containment ponds using berms or channels. Uncontaminated runoff or "runon" (precipitation runoff that has not been in contact with manure or feed) should be diverted away from corrals, feed areas and the containment facilities. Both of these cases require small berms or channels or a combination of the two to divert runoff. The ISDA recommendations for runoff diversion berms and channels are shown below:

Small Berms - Less than 30" high

Side slopes of berm should be at least 1 horizontal to 1 vertical, but 2 horizontal to 1 vertical may be required for some soil types
The top width of the embankment should be at least equal to the embankment height
The embankments should have 6" of freeboard above the design water surface level
The soil type should be at least 15% clay and free of manure
All surfaces should be compacted to 90% or greater of maximum density - Tracked or tired equipment can usually obtain this level of compaction if soil moisture is appropriate (See page 11 for details of moisture content)

Large Berms - Greater than 30" high

Side slopes of berm should be 2 horizontal to 1 vertical
The top width of the embankment should be at least equal to the embankment height
The embankments should have 1' of freeboard above the design water surface level
The soil type should be at least 15% clay and free of manure
All surfaces should be compacted to 90% or greater of maximum density - Tracked or tired equipment can usually obtain this level of compaction if soil moisture is appropriate (See page 11 for details of moisture content)

Channels or Swales

Side slopes of channel shall be at least 2 horizontal to 1 vertical, but 4 horizontal to 1 vertical should be used for grassed swales
The channel or swale should have 1' of freeboard above the design water surface level
The side slopes and bottom of channels may require rip-rap or other type of armoring if they are steep or subject to erosion

STORAGE POND SAFETY RECOMMENDATIONS

There are two primary safety issues involved in the use of livestock waste handling facilities. The first is the risk of asphyxiation or breathing toxic H₂S (hydrogen sulfide) when working in confined areas, such as manure storage or handling facilities. This risk is greatly increased when the waste is being agitated, such as an operator working on the facility. The second safety issue is the risk of drowning in the containment facility. Even very shallow containment facilities, such as gravity separators pose a risk to children and animals. Dairy and beef lagoons often crust over with manure, but the crust will not support the weight of a person or an animal. Because of these inherent risks with waste handling facilities, the ISDA strongly recommends the following precautions for the safety of humans and animals:

Enclosed storage facilities should be vented with an exhaust fan.
Enclosed storage facility openings should be guarded with grills or covers.
Ladders should not be installed on the outside of above ground storage facilities, unless they are terminated out of reach of children.
Fencing or railing should be installed around open manure storages that are below ground.
Warning signs should be installed around facilities and at all access points (Figure 5).
Electrical equipment should be guarded against explosion.

Figure 5. Typical Caution Signs for Waste Facilities

Note: USDA programs such as EQIP may have additional or more stringent requirements than those described on this page. Contact your local NRCS office for additional details.