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Beginning March 24, 2004, construction of
confinement operations with a one-time capacity of more than
500 animal units (1,250 hogs weighing more than 55 pounds or
5,000 pigs weighing between 15 and 55 pounds) must meet new minimum
concrete standards.
If a DNR construction permit is not required;
a structure constructed (defined in Iowa law as excavation for
the structure) before March 24, 2004 will be subject to the old
concrete rules and a structure constructed on or after March
24 will be subject to the new concrete rules.
If a construction permit is required but has
not been issued before March 24, a structure constructed pursuant
to the permit on or after March 24 will be subject to the new
concrete rules.
If a construction permit is issued before
March 24, but no construction on the site has occurred before
March 24; a structure constructed on or after March 24 will be
subject to the new concrete rules.
If a construction permit is issued before
March 24, and one or more structures is constructed on the site
pursuant to the permit before March 24; a structure constructed
after March 24 pursuant to the issued permit will be subject
to the old concrete rules.
The new rules provide two
options for liquid manure storage:
| 1. |
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The design may be certified by an NRCS or
professional engineer (an engineer is required for animal capacities
of more than 7,500 finishing pigs, 30,000 nursery pigs, 3,125
sows farrow to wean, and 6,875 sows farrow to finish) meeting
specifications in American Concrete Institute 318, 360 or 350;
Portland Cement Association EB075, EB001, or ISO72; or Midwest
Plan Service 36 or TR-9; and the following standards:
Floors must be 5 inches thick. DNR may require
only nondestructive methods to verify floor thickness. These
results must show at least 95% of the floor is 5 inches thick
with no portion being less than 4 1/2 inches thick.
No wire mesh as primary reinforcement in floors
of pits deeper than 4 feet. Wire mesh is allowed as primary reinforcement
in the floors of pits less than 4 feet deep. Fiber is not allowed
as the primary reinforcement in any pit floor.
Waterstops installed where fresh and hardened
concrete meet. Vertical rebar in walls must be extended into
the footings and bent at 90, or a separate dowel installed at
lest 12 inches into the footing.
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| 2. |
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If the structure's is not designed
and certified by a professional engineer, the design must meet
Midwest Plan Service specifications or specifications in tables
in the new rules and the following standards:
| (1) |
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Compacted subgrade to provide
a uniform (similar soils) and level base. |
| (2) |
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Be constructed above the groundwater
table or have a perimeter tile line installed within 3 feet of
the footings and covered with at 2 inches of gravel, granular
material, or fabric. |
| (3) |
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Meet compressive strength standard
ASTM C-94 and minimum as-placed psi (pounds per square inch)
of 4,000 psi for walls, floors, beams, columns, and pumpouts;
and 3,000 psi for footings. |
| (4) |
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Cement must be Portland cement
meeting ASTM C-150. Blended cements meeting ASTM C-595 are allowed
only between March 15 and October 15. Blast furnace slag blended
cements must contain 75% Portland cement. Aggregates must meet
ASTM C-33. |
| (5) |
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Concrete in walls must be consolidated
or vibrated in accordance with ACI-309. |
| (6) |
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Rebar must be at least 40 grade
steel. All rebar must be tied in place before concrete is placed,
with the exception of rebar dowels connecting the walls to the
footings. |
| (7) |
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Wall rebar in below ground storage
must have a 2 inch cover from the inside face. Vertical wall
rebar should be placed closest to the inside face. Wall rebar
placement must meet ACI-318. |
| (8) |
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Floors must be 5 inches thick.
DNR may require only nondestructive methods to verify floor thickness.
These results must show at least 95% of the floor is 5 inches
thick with no portion being less than 4 1/2 inches thick. Floors
of pits deeper than 4 feet must have primary reinforcement of
#4 rebar on 18 inch centers. Floors of pits less than 4 feet
deep shall have 6x6-W1.4xW1.4 welded wire fabric for shrinkage
reinforcement. All floor slab reinforcement must be placed in
the middle of the thickness of the slab. |
| (9) |
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Footings must be as thick as
the walls but no less than 8 inches thick, and have a width at
least twice the thickness of the footing. |
| (10) |
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Vertical rebar in walls must
be extended into the footings and bent at 90, or a separate dowel
installed at least 12 inches into the footing. |
| (11) |
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Walls must be placed with forms
ñ they cannot be earth-formed. |
| (12) |
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Concrete must be cured for at
least 7 days meeting ACI-308 by maintaining adequate moisture
or preventing evaporation. Curing must be done by ponding , spraying,
or fogging water; a curing compound meeting ASTM C-309; or using
wet burlap, plastic sheets or similar materials. |
| (13) |
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All construction joints in exterior
walls must prevent discontinuity of steel and have properly spliced
rebar through the joint. Waterstops installed where fresh and
hardened concrete meet. |
| (14) |
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Backfilling must be free of
vegetation, large rocks and debris and cannot start until the
slatted floors or permanent bracing has been installed. |
| (15) |
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A structure more than 12 feet
deep must be designed by a professional engineer. |
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Dry manure storage, which
includes confinement hoop buildings, must meet one of the following
two options:
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The design may be certified by an NRCS or
professional engineer (see #1 above for when an engineer is required)
meeting specifications in American Concrete Institute 318 or
360; Portland Cement Association EB075, EB001, or ISO72; or Midwest
Plan Service 36.
If the structure is not designed and certified
by a professional engineer, the design must meet the following
standards:
| Above ground: |
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meet requirements in (1), (3), (4), (5),
(6), (8), (12) above. |
Partially or completely
below ground: |
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meet requirements (1) through (15) above
and MWPS-36 or requirements in tables in the rules. |
Consideration must be given to internal and
external loads, including wind, building, manure pile and vehicle
loads.
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Concrete manure storage structures
located in Karst terrain or in an area that drains to a known
sinkhole must meet additional requirements as set out in the
rules. |
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