P03_SD_CS-07S_Earthfill-Class_S_2022.docx
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- NRCS South Dakota Easement Restoration IDIQ
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- 12FPC124Q0011
About this file
This document is the Natural Resources Conservation Service (NRCS) Construction Specification SD-07S for Earthfill - Class S. It outlines the requirements for the construction of compacted earth fills where the amount of compaction is to be controlled by specifying a construction method. The specification covers the materials to be used, foundation preparation, placement procedures, moisture content control, and compaction requirements for both earthfill and earth backfill. The key details include:
- Fill materials must meet certain criteria and cannot contain frozen soil, sod, roots, or rocks larger than 8 inches in diameter.
- Foundation surfaces must be prepared by scarifying or plowing prior to compaction.
- Fill must be placed in horizontal layers not exceeding 9 inches for large machines or 4 inches for small hand-directed tampers.
- Moisture content must be controlled to achieve proper compaction.
- Compaction methods are specified, including routing of hauling equipment or use of a tamping roller.
- Compaction requirements are provided for earth backfill adjacent to structures.
- Restrictions are included for the passage of heavy equipment near concrete structures.
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Natural Resources Conservation Service
Construction Specification SD-07S Earthfill – Class S
1. Scope The work shall consist of the construction of compacted earth fills where the amount of compaction is to be controlled by specifying a construction method.
Earthfill is composed of natural earth materials that can be placed and compacted by construction equipment operated in a conventional manner.
Earth backfill is composed of natural earth material placed and compacted in confined spaces or adjacent to structures (including pipes) by hand tamping, manually directed power tampers or vibrating plates, or their equivalent.
2. Materials All fill materials shall be obtained from required excavations and designated borrow areas. The selection, blending, placement, and compaction of fill will be subject to approval of the Natural Resources Conservation Service inspector.
Fill materials shall contain no frozen soil, sod, roots or other perishable material, or rocks larger than eight inches in diameter. Earthfill shall not be placed upon a frozen surface nor shall snow, ice, or frozen material be incorporated in the earthfill.
3. Foundation Preparation All foundation (including abutment) surfaces shall be shaped one horizontal to one vertical or flatter except as otherwise specified.
After stripping (see stripping specification), the foundation shall be loosened thoroughly by scarifying or plowing to a minimum depth of four inches. The foundation shall then be compacted by the process specified for the fill.
4. Placement All foundation excavation and preparation shall be completed and the foundation shall be free of standing water before placing fill. Except as required by the drawings, fill material shall be mixed and uniformly placed throughout the entire fill without lenses, streaks, pockets, or layers of material that differ significantly from surrounding material.
Placement and compaction methods must prevent damage to structures and allow the structure to assume backfill loads gradually and uniformly. Within 2 feet of any structure, fill layer thickness must not exceed 4 inches and equipment loads must not exceed 400 pounds.
Fill shall be placed in approximately horizontal layers. Except as described above, fill layer thickness shall not exceed nine inches for compaction by large machines or four inches for small hand directed power tampers.
Earthfill and earth backfill operations in dams, levees, and other structures designed to restrain the movement of water shall be placed parallel to the axis of the fill in continuous layers from abutment to abutment as site condition will allow. The top surface of embankments shall be maintained approximately level during construction.
If the surface of any layer becomes too hard and smooth for proper bond with the succeeding layer, it shall be scarified parallel to the axis of the fill, to a depth of not less than two inches, before the next layer is placed.
Except as otherwise specified, openings temporarily left in dam fills (for pipe installation, stream flow, etc.,) shall have side slopes three horizontal to one vertical or flatter. When filling the opening, the bonding surface of the fill in place shall be stripped of all material not meeting the requirements of this specification and shall be scarified, moistened, and recompacted as new earthfill is placed.
5. Control of Moisture Content At the time of compaction, earth fill materials shall have a moisture content that when kneaded in the hand will form a firm ball that does not easily crumble when pressed between the hands. If the soil is too wet, it will yield free water when kneaded in the hand.
Fill materials must be wetted or dried and mixed as needed to achieve proper moisture prior to compaction.
6. Compaction (Class S) Earthfill Earthfill layers shall be compacted by one of the following methods.
| a. | By routing the hauling and spreading equipment such that all points of the fill are traversed by at least one tread track of the loaded equipment traveling parallel to the centerline of the fill. |
| b. | By at least 2 passes of a tamping (sheepsfoot) roller weighing at least 100 pounds per square inch of bearing area. |
Earth Backfill Earth backfill adjacent to structures shall be compacted to a density equivalent to that of the surrounding inplace earth material or adjacent required earthfill or earth backfill. Compaction shall be accomplished by hand tamping or manually directed power tampers, plate vibrators, walk-behind, miniature, or self-propelled rollers. Unless otherwise specified heavy equipment including backhoe mounted power tampers or vibrating compactors and manually directed vibrating rollers shall not be operated within 3 feet of any structure. Towed or self-propelled vibrating rollers shall not be operated within 5 feet of any structure. Compaction by means of drop weights operating from a crane or hoist is not permitted.
The passage of heavy equipment will not be allowed:
| • | Over cast-in-place conduits within 14-days after placement of the concrete |
| • | Over cradled or bedded precast conduits within 7 days after placement of the concrete cradle or bedding |
| • | Over any type of conduit until the backfill has been placed above the top surface of the structure to a height equal to one-half the clear span width of the structure or pipe or 3 feet, whichever is greater, except as may be specified in the construction plans. |
Compaction of fill adjacent to concrete structures shall not be started for at least the following number of days after placement of the concrete.
| Concrete Structure |
| Days After Concrete Placement |
| Vertical or near-vertical walls with earth load on one side only |
| 14 |
| Walls backfilled on both sides simultaneously |
| 7 |
| Conduits and spillway risers, cast-in-place (with inside forms in place) |
| 7 |
| Conduits and spillway risers, cast-in-place (forms removed) |
| 14 |
| Conduits, pre-cast, cradled |
| 2 |
| Conduits, pre-cast, bedded |
| 1 |
| Anti-seep collars and cantilever pipe supports (backfill both sides simultaneously) |
| 3 |
| NRCS, SD | CONSTRUCTION SPECIFICATION SD-07S – Page 2 of 2 | October 2022 |
| NRCS, SD | CONSTRUCTION SPECIFICATION SD-07S – Page 1 of 4 | October 2022 |
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