CONSTRUCTION SPECIFICATIONS

for

North Raccoon Batch and Build Project Calhoun County, Iowa

List of Specifications

Specification Number Title Pages IA CS-001 Site Preparation (2013) 2 IA CS-003 Structure Removal (2011) 2 IA CS-005 Pollution Control (2011) 3 IA CS-006 Seeding and Mulching for Protective Cover (2011) 2

CS-008 Mobilization and Demobilization (2001) 2 IA CS-009 Subsurface Drain Investigation Removal and Repair (2014) 3 IA CS-011 Removal of Water (2011) 2 IA CS-021 Excavation (2013) 2 IA CS-023 Earthfill (2015) 3 IA CS-026 Topsoiling (2011) 2 IA CS-045 Plastic Pipe (2011) 4 IA CS-046 Tile Drains for Land Drainage (2013) 3 IA CS-051 Corrugated Metal Pipe Conduits (2011) 4 IA CS-095 Geotextile (2018) 5 IA PS-604 Saturated Buffer (Code 604) (2022) 4 IA PS-605 Denitrifying Bioreactor (Code 605) (2022) 4

IA CPS-606 Subsurface Drain (Code 606) (2013) 9 IA PS-620 Underground Outlet (Code 620) (2024) 5

These specifications are part of the construction plans. The work shall be performed in accordance with the drawings and specifications unless otherwise approved, in writing, by the Design Engineer. For items of work requiring inspection, it is the responsibility of the contractor to keep the Design Engineer (or representative) informed of the progress of work so that timely inspections may be performed. Work installed without inspection will not be certified as meeting standards.

This specifications packet also includes site-specific seeding plans (see IA CS-006), construction inspection plans, and operation/maintenance plans.

Site-Specific Seeding Plans

NRCS, IA SPECIFICATION - Page 1 of 4 April 2022

Practice Specification

Saturated Buffer (Code 604)

SCOPE

The work consists of furnishing materials, installing all components, and performing all clearing and grubbing, excavations, grading, and earthfill required to construct the Saturated Buffer as shown on the plans or as staked in the field.

It is the Landowner’s responsibility to locate any existing subsurface drains that may be under, along, or crossing the saturated buffer prior to construction. The NRCS is not responsible for any subsurface drains damaged during construction.

MATERIALS

Earth materials used in backfilling around the structure and pipe must be suitable material obtained from excavated material or from other approved sources as shown on the plans, described in Section 8, or approved by the Inspector. The fill material must be free from brush, roots, frozen material, sod, stones over 6 inches in diameter, or other undesirable material.

All disturbed areas must be finished so they are suitable for the planned use after construction is completed. If needed, stockpile topsoil and spread over excavations and other areas to facilitate establishment of vegetation.

Pipe, pipe sizes, fittings, and other appurtenances must be as specified on the plans. These items must conform to the “materials” section of Practice Specification IA-620, Underground Outlet, or as shown in

Section 8 of this specification.

Structures must be fabricated and installed as shown on the plans. Structures must be of durable material, structurally sound, and resistant to damage by rodents or other animals. Structures must be of rigid material which does not require supplemental support to remain in a vertical position. Materials which meet these requirements include the following:

Corrugated metal pipe, galvanized or aluminum, 16 gauge minimum,1.

Smooth steel pipe, with 3/16-inch minimum wall thickness,2.

Smooth plastic pipe, polyvinyl chloride (PVC), with an SDR of 43 or less,3.

High-density polyethylene pipe (PE). Round pipe shall have an SDR of 43 or less. Square intakes4.

shall have minimum wall thickness as shown in the following table:

Square PE Intake

All plastic and polyethylene structures must include ultra-violet stabilizer to protect them from solar degradation.

Appurtenances (i.e. tees and elbows) for polyvinyl chloride (PVC) inlets must be schedule 40 or heavier.

EXCAVATION

Remove all trees, stumps, roots, brush, and other undesirable materials from the work area as shown on the plans or as agreed upon with the Landowner and Inspector. Burning of trees and brush must comply with all applicable state and local regulations.

Cuts and fills should be made in such a manner that topography will be enhanced. Excess spoil material must be placed, spread, leveled, shaped, or hauled away as shown on the plans or as staked in the field.

Nominal Size Maximum Thickness

6 inch 0.16 inch

8 inch 0.21 inch

10 inch 0.26 inch

12 inch 0.31 inch

Natural Resources Conservation Service

All excavations must conform to the lines, grades, elevations, bottom width, and side slopes shown on the construction plans or as staked in the field. The conduit trench bottom must be smooth and free of exposed rock. If rock is encountered in the trench bottom, over-excavate the trench and place at least 6 inches of compacted fill or sand bedding in the trench to bring it up to the conduit grade.

If not otherwise shown on the plans, trench width at the top of the conduit must have a minimum clearance of 3 inches from outside edge of the conduit. The trench width at the top of the conduit must have a maximum clearance of 6 inches from the outside edge of the conduit unless an approved bedding material is used.

Plow installation is allowed. The minimum trench width must be 2 inches wider than the conduit on each side. Grade control and bedding conditions must be closely monitored during the plow installation.

All excavation for structure installation must be sloped to no steeper than 2:1.

STRUCTURE INSTALLATION

Install structures according to the lines, grades, and elevations shown on the plans and as staked in the field. Prefabricated structures must be handled in accordance with manufacturer recommendations to ensure the structure’s integrity after installation.

Place backfill around the structure in 9-inch lifts and hand compacted. The moisture content of the fill material must be such that a ball formed with the hands does not crack or separate when struck sharply with a pencil and will easily ribbon out between the thumb and finger.

The finished surfaces must present a workmanlike appearance.

PIPE INSTALLATION

Install pipe as shown on the plans and/or as staked in the field.

Unless otherwise specified, no filter or envelope is required around the distribution pipe. In stable soils, shape the bottom of the trench to form a semicircular, trapezoidal, or 90-degree “V” groove in its center.

Shape the groove to fit the size of tile. The 90-degree “V” groove must not be used on conduits greater than 6 inches in diameter.

If the bottom of the trench does not provide a sufficiently stable or firm foundation for the distribution pipe, use a sand-gravel mix or other approved material to stabilize the bottom of the trench.

When a filter is specified, the shape of the bottom of the trench and the gradation and thickness of the filter or envelope material to be placed around the conduit will be as shown on the plans. Place the filter or envelope material in the bottom of the trench. Install the conduit as shown on the plans. Place the filter or envelope material over the conduit.

The slope of the distribution lines is critical. Extra care must be taken to ensure that these lines are laid on a uniform grade throughout the length of the line or as shown on the plans. Anchor the pipe or place a vertical load on it, while exposed, at regular intervals to prevent uplift and separation from the bedding during backfill. Backfill the trench above the ground surface and round the top of the earthfill over the trench.

The minimum depth of backfill over the distribution conduit is 2.4 feet.

Make lateral connections with manufactured appurtenances (wyes, tees, couplings, etc.) comparable in strength and durability with the type of conduit being used. Pipe connections to the structure must be watertight.

OUTLET

Use a continuous section of non-perforated conduit at least 20 feet long at the outlet. Bury at least two-thirds of the outlet pipe in the ditch bank with the end of the pipe placed above the toe of the ditch, or protect the side slope from potential erosion due to discharge of the pipe. Acceptable materials for use of the outlet conduit include the following:

NRCS, IA April 2022SPECIFICATION - Page 2 of 4

Corrugated metal pipe, galvanized or aluminum, 16 gauge minimum;1.

Smooth steel pipe with a minimum wall thickness of 3/16 inch;2.

Smooth plastic pipe, polyvinyl chloride (PVC), with a SDR of 26 or less or schedule 40 or heavier;3.

or

Corrugated profile wall (dual wall) polyethylene pipe (PE).4.

All plastic (PVC) and polyethylene pipe (PE) outlets must include ultra-violet stabilizer. Do not use PVC and PE pipe outlets where vegetation on the ditch bank may be burned and will likely damage the pipe.

All outlet pipes must have a flap-gate type animal guard.

SEEDING

Establish a protective cover of vegetation on the entire soil saturation area and all surfaces disturbed by construction as shown on the plans or staked in the field. Plant species must be water tolerant and suitable for wet soil conditions. Seeding and mulching must be performed in accordance with the IA-CPA-

4, Seeding Plan, and Construction Specification IA-6, Seeding and Mulching for Protective Cover.

NRCS, IA April 2022SPECIFICATION - Page 3 of 4

NRCS, IA April 2022SPECIFICATION - Page 4 of 4

Specific Site Requirements

NRCS, IA SPECIFICATION - Page 1 of 4 October 2022

Denitrifying Bioreactor (Code 605)

SCOPE

The work consists of constructing a denitrifying bioreactor as required by the construction plans.

UTILITIES

The contractor is responsible for calling Iowa One Call at least 48 hours prior to beginning any excavation work. The landowner is responsible for locating other infrastructure such as tile lines and structures. The landowner will obtain all necessary permissions from regulatory agencies, or document that no permits are required.

GENERAL

Carry out construction operations in a manner and sequence that erosion and air and water pollution are minimized and held within legal limits.

The completed job must present a workmanlike appearance and conform to the line, grades, and elevations shown on the drawings or as staked in the field.

Carry out all operations in a safe and skillful manner. Observe safety and health regulations and use appropriate safety measures.

Save documentation of materials used (geotextile tags, seed tags, photographs of pipe labeling, etc.) and provide to NRCS.

Remove all trees, stumps, brush, and debris from the site and disposed of so they will not interfere with construction or proper functioning of the structure.

EXCAVATION

Unless otherwise specified, begin excavation for and subsequent installation of the pipe and structures at the outlet end and progress upstream.

Excess spoil material must be placed, spread, leveled, shaped, or hauled away as shown on the construction plans or as staked in the field. Finish the completed job to a degree so the surface can be traveled with farm-type equipment unless otherwise specified in the construction plans.

All excavations must conform to the lines, grades, elevations, bottom width, and side slopes shown on the construction plans or as staked in the field.

Trench shields, shoring, bracing, or other methods necessary to safeguard the workers and prevent damage to the existing improvements shall be furnished, placed, and subsequently removed by the contractor. Occupational Safety and Health Administration (OSHA) requirements relating to trench safety shall be followed.

MEDIA CHAMBER

Line the bottom and sides of the media chamber with plastic as shown on the construction drawings

Plastic must have a minimum thickness of 4 mil.

If a soil cap is to be constructed over the top of the chamber, use geotextile to separate the media from the soil. Geotextile must be non-woven, class II, and meet the requirements of Iowa Construction

Specification IA-95, Geotextile.

Carbon source media must meet the following requirements:

Wood material must be chipped, not shredded. At minimum, 90% of the chips by weight must be 1-1.

inch to 2-inch in length (longest direction).

Wood chips must be free from objectionable material such as dirt, fines, stones, leaves, long2.

stringy material, etc. Decomposed or partially decomposed wood chips shall not be used.

Wood must not be treated for ground contact.3.

Wood made from high tannin content species such as oak, cedar, or redwood is to be avoided. 4.

NRCS will reject any proposed wood chips with more than 50% by volume oak wood chip materials. The contractor is advised to check with NRCS in advance for acceptance of the media to be used in the bioreactor.

Spread the media evenly around the chamber. There must be no air pockets, bridging, or uneven surface of the media. Media must be placed in a manner that avoids damage to the distribution and collection pipes in the chamber.

Mound the top surface of the media chamber with the material specified in the plans to allow for settlement of the media and to shed water. Mound the center of the trench as shown on the plans but no less than 10% of the total depth of the media material.

WATER CONTROL STRUCTURE AND PIPE

The materials and manufacture of the water control structure, pipe, anti-seep collars, coupling bands, coatings, and other appurtenances must be as shown on the construction drawings and conform to materials and applicable reference specifications as shown in Iowa Construction Specification IA-620, Underground Outlet.

Place the water control structure and pipe couplers on a stable base. The stable base may be compacted earth, compacted sand, or a concrete pad. Extend the stable base no less than 1 foot around the structure.

Install the structure with all stop boards in their tracks. Place impervious backfill material around the structure and appurtenances by hand and in layers not more than 6 inches thick before compaction.

Thoroughly compact each layer, by means of hand tamping, to the same density as the surrounding materials. Increase the height of fill at approximately the same rate on all sides of the structure.

Lay the pipe to the lines, grades, and elevations shown on the drawings. Bed the pipe firmly and uniformly throughout its entire length. Use hand tamping methods around pipes that are within 20 feet of the water control structure. Beyond that distance, the pipe may be laid with a tile plow or trencher designed for proper bedding of the pipe, and the disturbed soil allowed to naturally subside back into place.

OUTLET

Where the construction plans call for a free outlet, use a continuous section of non-perforated conduit at the outlet, unless a headwall is used. All outlets must have an animal guard, installed to allow passage of debris.

The continuous section of non-perforated conduit must be long enough to satisfy all requirements of

Conservation Practice Standard 606 – Subsurface Drain:

At least two-thirds of the pipe must be buried in the ditch bank. •

The cantilever section must extend to the toe of the ditch side slope or to the side slope protected • from erosion.

The continuous section must be at least 20 feet long. •

Acceptable materials for use at the outlet include the following:

Corrugated metal pipe, galvanized or aluminum, 16-gauge, minimum thickness, •

Smooth steel pipe with 3/16 of an inch minimum thickness, •

Smooth plastic pipe, polyvinyl chloride (PVC), with a SDR of 35 or less or schedule 40 or heavier, • and

Dual wall corrugated polyethylene pipe. •

All plastic and polyethylene pipe outlets must include an ultra-violet stabilizer.

VEGETATION

NRCS, IA October 2022SPECIFICATION - Page 2 of 4

Establish a protective cover of vegetation on all surfaces of the areas disturbed by construction. Perform seeding and mulching in accordance with the Seeding Plan, IA-CPA-4, and Construction Specification IA-

6, Seeding and Mulching for Protective Cover.

Establish vegetation as soon after construction as possible.

NRCS, IA October 2022SPECIFICATION - Page 3 of 4

NRCS, IA SPECIFICATION - Page 1 of 5 August 2024

Underground Outlet (Code 620)

SCOPE

This work consists of installation of underground outlets and any appurtenant water control structures in accordance with an approved plan and design.

MATERIALS

Materials for underground outlets must meet the requirements as shown in the plans and specifications.

They must be field inspected for any deficiencies such as thin spots or cracking prior to installation.

Conduit

The following reference specifications pertain to products currently acceptable for use as underground outlets:

Plastic Pipe

Clay Pipe

Concrete Pipe

Other Pipe

Inlet

Fabricate and install the inlet as shown on the plans. Inlets must be of durable material, structurally sound, and resistant to damage by rodents or other animals. Inlets must be of rigid material, which does not require supplemental support to remain in a vertical position. Materials, which meet these requirements, include the following:

3 through 24 inch Corrugated Polyethylene (PE) Pipe and Fittings ASTM F667

12 to 60 in. Annular Corrugated Profile-Wall Polyethylene (PE) Pipe ASTM F2306

2 to 60 in. Annular Corrugated Profile Wall Polyethylene (PE) Pipe ASTM F2648

3 to 24 in. Lined Flexible Corrugated Polyethylene Pipe ASTM F3390

Poly (Vinyl Chloride) (PVC) Corrugated Sewer Pipe With a Smooth Interior and Fittings

(4-36 inch)

ASTM F949

Poly (Vinyl Chloride) (PVC) Sewer Pipe and Fittings ASTM D2729

Type PSM Poly (Vinyl Chloride) (PVC) Sewer Pipe and Fittings ASTM D3034

Poly (Vinyl Chloride) (PVC) Plastic Pipe (Sch Series) ASTM D1785

Poly (Vinyl Chloride) (PVC) Pressure-Rated Pipe (SDR Series) ASTM D 2241

Clay Drain Tile ASTM C4

Vitrified Clay Pipe, Extra Strength, Standard Strength and Perforated ASTM C700

Concrete Drain Tile (4-36 inch) ASTM C412

Concrete Pipe for Irrigation or Drainage ASTM C118

Nonreinforced Concrete Sewer, Storm Drain and Culvert Pipe ASTM C14

Reinforced Concrete Culvert, Storm Drain and Sewer Pipe ASTM C76

Perforated Concrete Pipe ASTM C444

Styrene-Rubber (SR) Plastic Drain Pipe and Fittings ASTM D2852

Corrugated Aluminum Pipe for Sewers and Drains ASTM B745

Corrugated Steel Pipe, Metallic-Coated for Sewers and Drains ASTM A760

Corrugated metal pipe, galvanized or aluminum, 16 gauge minimum,1.

Smooth steel pipe, with 3/16-inch minimum wall thickness,2.

Smooth plastic pipe, polyvinyl chloride (PVC), with an SDR of 43 or less,3.

High-density polyethylene pipe (PE). Round pipe shall have an SDR of 43 or less. Square intakes4.

shall have minimum wall thickness as shown in the following table:

Square Intake Wall Thickness

All plastic and polyethylene inlets must include ultra-violet stabilizer to protect from solar degradation.

Perforations in the inlet must be smooth and free of burrs. Unless otherwise specified, the above ground portion of the inlet will have holes evenly spaced around the perimeter of the inlet in accordance with the following table:

Minimum Number of Holes

If slots or round holes other than 1 inch in diameter are provided, the total cross sectional area of the openings per foot will be equivalent to that provided by 1 inch diameter round holes meeting the above criteria.

The below ground portion of the inlet may be perforated with holes 5/16-inch in diameter or less to provide drainage around the inlet.

Appurtenances (i.e. tees and elbows) for polyvinyl chloride (PVC) inlets must be schedule 40 or heavier.

Additional subsurface drainage tubing or tile may be used in conjunction with the surface inlet to improve access and farmability around the inlet. These underground extensions (when used) will have a minimum length of 10 feet.

The inlet must be offset from the main conduit except as noted below. A minimum of 8 feet of non-perforated conduit will be installed between the inlet and the main conduit. The minimum diameter of the offset line is 3 inches. When conduit capacity is based on orifice flow from the inlet, fabricatethe inlet so that an orifice can easily be installed.

Only the top inlet in a terrace system may be placed directly on the main conduit. If the topmost inlet in a terrace system is placed directly on the main conduit, the conduit must be non- perforated from the inlet to the toe of the terrace back slope.

Outlet

Use a continuous section of non-perforated conduit at least 20 feet long at the outlet. Two-thirds of the outlet pipe must be buried in the ditch bank, and the cantilever section must extend to the toe of the ditch side slope or protect the side slope from erosion. Acceptable materials for use at the outlet include the following:

Nominal Size Minimum Thickness

6 inch 0.16 inch

8 inch 0.21 inch

10 inch 0.26 inch

12 inch 0.31 inch

Inlet Size Minimum Number of 1” Diameter Holes per Foot of Inlet

4 inch 20

5 inch 24

6 inch 30

8 inch 40

10 inch 50

12 inch 60

NRCS, IA August 2024SPECIFICATION - Page 2 of 5

Corrugated metal pipe, galvanized or aluminum, 16 gauge minimum; 1.

Smooth steel pipe, with 3/16-inch minimum wall thickness; 2.

Smooth plastic pipe, polyvinyl chloride (PVC), with a SDR of 26 or less or schedule 40 or heavier; 3.

or

Corrugated profile wall (dual wall) polyethylene (PE) pipe meeting or exceeding the requirements 4.

of ASTM F 2648 (2” to 60”), ASTM F 2306 (12” to 60”). Pipe conforming to AASHTO M 252 (3” to

10”), or AASHTO M 294 (12” to 60”) is acceptable.

All plastic and polyethylene pipe outlets must include ultra-violet stabilizer. PVC and PE pipe outlets must not be used where burning vegetation on the outlet ditch bank is likely to create a fire hazard.

Connections with the outlet pipe must be made watertight.

Equip the outlet with a flap gate rodent guard.

TRENCH EXCAVATION

Trench excavation must be sufficient to provide required cover after other construction is completed.

The trench bottom will be smooth and free of exposed rock. If rock is encountered in the trench bottom, over-excavate the trench and place at least 6 inches of compacted earth or sand bedding in the trench to bring it up to the conduit grade. In stable soils, shape the bottom of the trench to form a semicircular, trapezoidal, or 90-degree “V” groove in its center. Shape the groove to fit the size of conduit. Do not use the 90-degree “V” groove on conduits greater than 6 inches in diameter.

Unless otherwise shown on the drawings, use a trench width at the top of the conduit the minimum required to permit installation and provide bedding conditions suitable to support the load on the conduit, but with not less than 3 inches of clearance on each side. Use a maximum trench width of the conduit diameter plus 12 inches measured at the top of the conduit, unless approved bedding is installed.

Plow installation is allowed except under the base width of the terrace or embankment. Trench width will be at least two (2) inches wider than the conduit on each side to allow sufficient bedding to support the pipe.

INSTALLATION

Install the underground outlet system to the line and grade shown in the plans or as staked in the field.

Install and properly blind or bed conduit lines prior to placement of any other earthfill over the lines.

Join conduit lines with standard factory couplers, if applicable, to produce a continuous system. Use internal couplersif they do not cause excessive flow restrictions. Protect conduit ends during installation.

Install all appurtenant structures, including trash and rodent guards, promptly and make provisions for protecting them during installation. Cap all conduit ends except the outlet and inlets with screens with standard factory end caps or concrete. When corrugated plastic tubing is used, no more than 5% stretch will be allowed.

Orifice plates, when specified, must have smooth edges and fit tightly.

TRENCH BACKFILL

Bed an backfill conduits throughout the base width of the basin embankment or terrace ridge. Place friable soil material in 4 inch layers and hand tamped to a depth of 2 feet above the conduit. Slope the sides of the remaining trench no steeper than 3 horizontal to 1 vertical and place backfill in 9 inch layers and machine compacted.

Water packing may be used as an alternative to mechanical compaction. If the conduit is non- perforated, fill it with water during the water packing procedure. The initial backfill, before wetting, must be of sufficient depth to ensure complete coverage of the pipe after consolidation has taken place. Perform water packing by adding water in such quantity as to thoroughly saturate the initial backfill without inundation. Allow the wetted fill to dry until firm before final backfill is begun. Perform final backfill by placing friable soil material in 4 inch layers and hand tamping to a depth of 2 feet above the conduit.

NRCS, IA August 2024SPECIFICATION - Page 3 of 5

Slope the sides of the remaining trench no steeper than 3 horizontal to 1 vertical and backfill placed in 9 inch layers and machine compacted.

Backfill conduit which is not under the embankment or terrace ridge with select bedding material containing no hard objects larger than 1½ inches in diameter to a minimum depth of 6 inches over the conduit. Hold the conduit in place mechanically while select backfill material is placed around and over the conduit. This is to ensure that the proper conduit grade is maintained. Place all backfill material so that deflection or displacement of the conduit will not occur. Backfill the remainder of the trench above the conduit as rapidly as consistent with the soil conditions. Extend backfill above the ground surface and be well rounded over the trench. Large stones, frozen material, and large clods are not allowed in the backfill material.

FINISH

Smooth work areas and leave in a workmanlike manner. Establish vegetation or other protective cover as specified.

NRCS, IA August 2024SPECIFICATION - Page 4 of 5