Natural Resources Conservation Service s65

NATURAL RESOURCES CONSERVATION SERVICE CONSERVATION PRACTICE SPECIFICATION

356 - DIKE

I. SCOPE IV. COMPACTED EARTHFILL AND BACK- FILL The work shall consist of excavating and placing earth materials for the construction of dikes to the lines, Material grades, elevations, and cross-sections as shown on the drawings or as staked in the field. All fill material shall be only suitable material obtained from selected areas as shown on the drawings. Fill II. SITE PREPARATION materials shall contain no sod, brush, roots, or other perishable or unsuitable material. Cobbles and rock The foundation area shall be cleared of all trees, fragments over six inches in diameter shall be removed stumps, roots, brush, rocks, sod, debris and other from the material prior to compaction. The suitability objectionable material. All channel banks and sharp of fill material shall be as determined by the Engineer. breaks shall be sloped to no steeper than 1:1. All topsoil shall be removed. Loose earth shall not be left Placement on the foundation area to a depth in excess of six inches above approved undisturbed foundation The placing and the spreading of the fill material shall material. The surface of the foundation area shall be be started at the lowest point of the foundation and the thoroughly scarified before placement of the fill shall be brought up approximately horizontal embankment material. layers, of such thickness that the required compaction can be obtained with the equipment used. The sites of the borrow area shall be stripped to sufficient depth to remove all vegetation, roots, brush, Fill placed around structures will be brought up at sod and other objectionable material. approximately uniform height on all sides of the structure. Clearing and disposal methods shall be in accordance with applicable state and county laws with due regards The distribution and gradation of materials throughout to the safety of persons and property. the fill shall have no lenses, pockets, streaks or layers of material differing substantially in texture or III. EXCAVATION gradation from the surrounding material. The surface of the finished dike shall be graded smooth. Cutoff Trench Moisture The cutoff trench, when specified, shall be excavated to lines and grades as shown on the drawings or as The moisture content of the fill material shall be staked in the field. Backfill shall not be placed in the adequate to obtain the required degree of compaction trench until the Engineer has inspected and approved with the equipment used. the trench. The trench shall be kept free of standing water during backfill operations. The proper moisture content will be determined by inspection during the placement operation. The soil Conduit should contain sufficient moisture so that the soil will maintain a ball shape when squeezed in the hand. Trench excavation for installation of a conduit, where Material that is too wet for proper compaction shall shown on the drawings, shall be made in original either be removed or allowed to dry prior to ground. Excavation in compacted fill may be allowed compaction. As far as practicable, the material shall be provided the bottom of the trench is at or near brought to the proper water content in the borrow pit undisturbed foundation. The trench shall conform to before excavation. Supplemental water, when lines and grades shown in the drawings. required, may be applied by sprinkling the materials in the fill. Uniform distribution of the moisture shall be

NRCS, CA November 2009 356-2 obtained by discing, blading, or other approved meeting the specified requirements shall be reworked methods prior to compaction. or removed and replaced with acceptable fill.

Compaction V. CONDUITS

Compaction shall meet the requirements of one of the All conduits shall be placed on a firm foundation to the Method specified on the Practice Requirement sheet lines and grades and in the location(s) shown on the and as described below. drawings. Selected backfill material shall be placed in layers around the conduit and component parts and Method A. Sheepsfoot roller - The maximum layer each successive layer shall be thoroughly compacted. thickness shall be eight inches before compaction. The roller shall have staggered, uniformly spaced VI. ADDITIONAL REQUIREMENTS FOR tamper feet and be equipped with suitable cleaners. CLASS III DIKES WITH ORGANIC SOILS The weight of the roller shall not be less than 2,500 pounds per foot of width. The maximum In addition to the requirements stated within this speed of the compaction equipment shall be three specification, the following specification applies to miles per hour. The entire surface of each layer Class III Dikes with organic soils. Fill material may be placed should receive six passes of this equipment organic soils with low coarse fiber content, free of all to obtain the necessary compaction. Adjustment in roots, brush and other objectionable materials, obtained the number of passes may be necessary during from borrow areas by dredge or dragline. Fill shall be construction. placed so as to permit free drainage. Shaping of the dike shall be such to break up lumps and clods to yield Method B. Pneumatic tired equipment - The maximum a smooth surface and finish to the lines and grades layer thickness before compaction shall be six specified. Compaction shall be by Method C. inches. A loaded carryall may be considered a pneumatic roller. The wheels of this equipment VII. VEGETATIVE COVER must pass over 90 percent of the surface of each lift before a new lift is placed. Unless otherwise specified, a protective cover of vegetation shall be established on all exposed surfaces Method C. Track laying equipment - (bulldozer) - The of the embankment and borrow areas. Vegetative maximum layer thickness before compaction shall plantings shall conform with the requirements of be four inches. The tracks of the equipment must Practice Specification 342 - Critical Area Planting. pass over 90 percent of the surface of each lift When specified, the embankment shall be fenced before a new lift is placed. where necessary to protect the vegetation.

Method D. Compaction shall result in densities equal VIII. SPECIAL MEASURES to or greater than 95 percent of the maximum obtained by laboratory compaction at optimum Measures and construction methods shall be moisture of like soils in accordance with the incorporated as needed and practical that enhance fish procedure given in ASTM D-698, Procedure A. and wildlife values. Special attention shall be given to protecting visual resources and maintaining key shade, Heavy compaction equipment shall not be operated food and den trees. within two feet of any structure. Hand directed tampers or compactors shall be used on areas not IX. CONSTRUCTION OPERATIONS accessible to heavy compaction equipment, and within two feet of any structure. Fills compacted in this Construction operations shall be done in such a manner manner shall be placed in layer not greater than four that erosion and air and water pollution are minimized inches in thickness before compaction, and shall meet and held within legal limits. The owner, operator, the same density requirements as adjacent areas. Contractor or other persons will conduct all work and operations in accordance with proper safety codes for Compliance with compaction requirements will be the type of construction being performed with due determined by the procedure given in ASTM D-1556 regards to the safety of all persons and property. or D-2167 for Method D and by observation of performance for Methods A, B, and C. Fill not The completed job shall be workmanlike and present a good appearance.

NRCS, CA November 2009