This item shall consist of furnishing, hauling, placing, and securing mulch on surfaces indicated on the plans or designated by the ENGINEER. The mulch is used to conserve moisture, prevent surface compaction or crushing, reduce runoff and erosion, control weeds, and help hasten establishment of plant cover.
1204-2.1 MULCH MATERIAL. Acceptable mulch shall be the materials listed below or any approved locally available material that is similar to those specified. Low graded, musty, spoiled, partially rotted hay, straw, or other materials unfit for animal consumption will not be acceptable. Mulch materials which contain matured seed of species which would volunteer and be detrimental to the proposed over seeding, or to surrounding farmland, will not be acceptable. Straw or other mulch material which is fresh and/or excessively brittle, or which is in such an advanced stage of decomposition as to smother or retard the planted grass, will not be acceptable.
(a) Hay. Hay shall be native hay, Sudan grass hay, broomsedge hay, legume hay, or similar hay or grass clippings. Average length shall be 10 inches. Leguminous plants shall not exceed 25 percent of the dry weight of the mulch.
(b) Straw. Straw shall be the threshed plant residue of oats, wheat, barley, rye, or rice from which the grain has been removed. Average length shall be 6 inches if anchored by asphalt or netting or 10 inches if anchored mechanically.
(c) Stalks. Stalks shall be the whole or shredded stems of corn, cane, sorghum, flax, sunflowers, potato vines, or other coarse stemmy material.
(d) Manure. Manure shall be fresh or partially decomposed strawy stable manure containing not over 25 percent of solid material by volume.
(e) Hay Mulch Containing Seed. Hay mulch shall be mature hay containing viable seed of native grasses or other desirable species stated in the special provisions or as approved by the ENGINEER. The hay shall be cut and handled so as to preserve the maximum quantity of viable seed. Hay mulch which cannot be hauled and spread immediately after cutting shall be placed in weather resistant stacks or baled and stored in a dry location until used.
(f) Manufactured Mulch. Cellulose-fiber or wood pulp mulch shall be products commercially available for use in spray applications. Wood cellulose fiber mulch shall consist of wood cellulose fiber pulp and fiber coatings which shall contain no germination or growth in inhibiting factors. This mulch shall be free of contamination from noxious weed seed, seed from other competitive plants, mold, or fungus. It shall be dyed an appropriate color to allow visual metering of its application, and shall have the property of becoming dispersed and suspended when agitated in water. When sprayed uniformly on the surface of the soil, the fibers shall form a blotter-like ground cover that readily absorbs water and allows infiltration to the underlying soil.
Weight specifications from suppliers, and for all applications, shall refer only to air-dry weight of the fiber, a standard equivalent to 10 percent moisture. Each package of the cellulose fiber shall be marked by the manufacturer to show the air dry weight content. Suppliers shall certify, upon request of the ENGINEER, that laboratory and field testing of their product has been accomplished and that it meets the foregoing requirements and intent. Sampling and testing for moisture content will be in accordance with ASTM D2016, Over Drying Method.
(g) Asphalt Binder. Asphalt Binder material shall conform to the requirements of ASTM D977, Type SS-1 or RS-1, as appropriate.
(h) Mulch Blanket.
The excelsior blanket shall consist of a machine produced mat of curled wood excelsior of 80 percent 6-inch or longer fiber length with consistent thickness and the fiber evenly distributed over the entire area of the blanket. The tope side of each blanket shall be covered with a 2-inch by 1-inch biodegradable mesh. The blanket shall be smolder resistant. The blanket shall be secured to the ground with wire staples .091-inch diameter or greater. Staples will be "U" shaped with legs 6 inches in length with a 1-inch crown.
The excelsior erosion blankets will be equivalent to the "Curlex" (trademark) blanket manufactured by the American Excelsior Company, Arlington, Texas.
Paper fabric blanket shall consist of a knitted construction of yarn interwoven with strips of biodegradable paper as manufactured by Gulf States Paper Corporation or equal. The paper strips and yarn shall degrade without residue. Staples shall be high carbon iron 6 inches to 12 inches long. Paper fabric shall be 0.05 to 0.30 pounds per square yard (10%) per manufacturer's recommendation for fabric degradation timing to produce grass stand specified.
(i) Mulch Net. Mulch net shall consist of a biodegradable net made from extruded oriented polypropylene as manufactured by American Excelsior Company or equal. Mulch netting shall be stranded with approximately 5/8-inch by 3/4-inch mesh opening (maximum 1½ inches by 3 inches) to hold loose straw, hay, bark, wood chips, and other loose mulches in place.
(j) Hydro-Mulch. Mulch to be used shall consist of a wood cellulose fiber that has not been treated with any germination or growth inhibitive substances. The mulch shall be treated with a tack and fiber to enhance seed and mulch placement and adherence to the soil. The mulch shall be free of contamination from noxious weed seed and seed from competitive plants.
1204-2.2 INSPECTION. Within five (5) days after acceptance of the bid, the ENGINEER shall be notified of sources and quantities of mulch materials available, and the CONTRACTOR shall furnish him with representative samples of the materials to be used. These samples may be used as standards with the approval of the ENGINEER, and any materials brought on the site which do not meet these standards shall be rejected.
1204-3 CONSTRUCTION REQUIREMENTS
MULCHING. Before spreading mulch, all large clods, stumps, stones, brush, roots, and other foreign material shall be removed from the area to be mulched. Mulch shall be applied immediately after seeding or within 24 hours. The spreading of the mulch may be by hand methods, blower, or other mechanical methods, provided a uniform covering is obtained. When spread by hand, the bales of hay must be torn apart, "fluffed up," and spread uniformly over the area. Mulches shall not be applied when velocities exceed 15 miles per hour. If excessive breakage of mulch occurs during spreading or anchoring, mulch shall be "wet down" with sprinkler or other suitable means.
Straw or hay shall be spread over the surface to form a uniform thickness to provide a loose depth of not less than 1½ inches nor more than 3 inches. Other organic material shall be spread at the rate directed by the ENGINEER. Mulch may be blown on the slopes, and the use of cutters in the equipment for this purpose will be permitted to the extent that at least 95 percent of the mulch in place on the slope shall be 6 inches or more in length. When mulches applied by the blowing method are cut, the loose depth in place shall not be less than 1 inch nor more than 2 inches.
TABLE OF MULCH APPLICATION RATES
Rate of Asphalt
Anchoring Emulsion Track
Mulch Method Rate (lbs/acre) Gal/Acre
Native or Tame Hay Mulch Tiller 3000-4000* -
Native or Tame Hay Asphalt or Resin
Emulsion 3000 300
Small Grain Straw Mulch Tiller 4000-5000* -
Small Grain Straw, Flax Asphalt or Resin
Emulsion 3000 300
Flax Mulch Tiller 3000-5000* -
Manure None 30,000-40,000 -
Manure Disk 60,000-80,000 -
Wood Cellulose Fiber Hydraulic Spray
Equipment 1500-2000 -
Hydro Spray Equipment 2000 -
*Other methods as hand anchorage, netting, and peg and string method use 3000 lbs/acre.
1204-3.2 SECURING MULCH. The mulch shall be held in place by light disking, a very thin covering of topsoil, small brush, pins, stakes, wire mesh, asphalt, binder, or other adhesive material approved by the ENGINEER. Where mulches have been secured by either of the asphalt binder methods, it will not be permissible to walk on the slopes after the binder has been applied. The CONTRACTOR is warned that in the application of asphalt binder material, he must take every precaution to guard against damaging or disfiguring structures or property on or adjacent to the areas worked and that he will be held responsible for any such damage resulting from his operations.
(a) If the "Peg and String" method is used, the mulch shall be secured by the use of stakes or wire pins driven into the ground on 5-foot centers or less. Binder twine shall be strung between adjacent stakes in straight lines and crisscrossed diagonally over the mulch, after which the stakes shall be firmly driven nearly flush to the ground to draw the twine down tight onto the mulch.
(b) Mulch Nettings – Staple paper, cotton, or plastic netting to the soil surface according to manufacturer's recommendations.
(c) Hand Anchorage – With a square pointed spade, punch mulch into the surface soil in contour rows 12 inches apart.
(d) Mechanical Mulch Anchoring or Crimping -
Tools – Use a heavy, straight coulter type mulch tiller (Imco). The coulters should be 1/4-inch thick and be of sufficient diameter to prevent the frame from dragging the mulch. The edges should be dull so as not to cut the mulch during the anchoring operation. The edges may be serrated or smooth; if serrated, the scallops should not be more than 3 inches in length and 3/4 inch in depth. The rows or furrows made by the mulch tiller shall be spaced 6 to 12 inches apart. Penetration depth should be 2 to 3 inches. The mulch should not be covered with excessive amounts of soil. Limit to no more than two (2) passes by the mulch tiller. All mulching operations will be done on the approximate contour.
2. Site Preparation – When using a mulch anchoring tool, the seed bed must be loosened to a minimum depth of 3 inches prior to placing and anchoring mulch material. This is necessary for the 2- or 3-inch preparation required for mulch anchorage. (Drill or seeding equipment used at this time must be equipped with depth bands as the ability to obtain a firm seed bed is improbable.)
(e) Asphalt Emulsion Mulch Tack – Asphalt emulsion shall be continuously applied with an emulsion spray system equipment with a mechanical mulch hay blower. Application temperature shall be 50F or greater (air temperature). The asphalt shall be applied with a mechanical mulch blower equipped with an emulsion sprayer system having a heating unit.
(f) Resin Emulsion Mulch Tack – The resin shall be applied with a mechanical mulch blower equipped with an emulsion spray system having a heating unit.
(g) Wood cellulose fiber mulch shall be applied with hydraulic spray equipment at the rate of 1,500 to 2,000 pounds per acre. The fiber shall be added to the water slurry in a hydraulic seeder along with the proportionate quantities of seed, fertilizer, and other approved materials. All ingredients shall be mixed to form a homogeneous slurry. Using the color of the mulch material as a metering agent, one shall uniformly spray the slurry mixture on the prepared seed bed.
A non-toxic, organic soil stabilizer may be included or added to the wood cellulose fiber where there is a high probability of wind or water erosion. Application rates of such soil stabilizers will be at the manufacturer's recommendation rates.
Since this method is basically a broadcast (surface) application of seed, the mulched area shall be kept moist by sprinkler or other means for a period of thirty (30) days. Under conditions of extreme winds, some peeling may occur. The mulch also is subject to washing away under intense or prolonged rains. These factors should be considered in selecting this method of mulching.
(h) Mulch blankets may be primarily used to mulch small critical areas (such as ditch bottoms and slopes greater than 3:1) and shall be applied in accordance with the manufacturer's recommendations. When the blanket is unrolled, the netting shall be on top and the fibers in contact with the soil over the entire area. In channels, the blankets shall be applied in the direction of the flow of water. On slopes, the blankets shall be applied across the slope. Ends and sides shall be butted snugly and stapled, in both instances.
The staples shall be driven vertically into the ground, spaced approximately 2 linear yards apart, on each side of the blanket, and one row in the center alternately spaced between each side. Use a common row of staples on adjoining blankets.
(i) If the "Asphalt Spray" method is used, all mulched surfaces shall be sprayed with asphalt binder material so that the surface has a uniform appearance. The binder shall be uniformly applied to the mulch at the rate of approximately 8.0 gallons per 1,000 square feet, or as directed by the ENGINEER, with a minimum of 6.0 gallons and a maximum of 10 gallons per 1,000 square feet depending on the type of mulch and the effectiveness of the binder securing it. Bituminous binder material may be sprayed on the mulch's slope areas from either the top or the bottom of the slope. An approved spray nozzle shall be used. The nozzle shall be operated at a distance of not less than 4 feet from the surface of the mulch and a uniform distribution of the bituminous material shall be required. A pump or an air compressor of adequate capacity shall be used to insure uniform distribution of the bituminous material.
(j) If the "Asphalt Mix" method is used, the mulch shall be applied by blowing, and the asphalt binder material shall be sprayed into the mulch as it leaves the blower. The binder shall be uniformly applied to the mulch at the rate of approximately 8.0 gallons per 1,000 square feet or as directed by the ENGINEER, with a minimum of 6.0 gallons and a maximum of 10 gallons per 1,000 square feet depending on the type of mulch and effectiveness of the binder securing it.
(k) If the hydro-mulch method is used, the mulch shall be uniformly applied at the application rate shown and shall cover a minimum of 95 percent of the seedbed area. After application, the mulch shall permit percolation of water to the underlying soil.
1204-3.3 CARE AND REPAIR
(a) The CONTRACTOR shall care for the mulched areas until final acceptance of the project. Such care shall consist of providing protection against traffic or other use by placing warning signs as approved by the ENGINEER, and erecting any barricades that may be shown on the plans before or immediately after mulching has been completed on the designated areas.
(b) The CONTRACTOR shall be required to repair or replace any mulching that is defective or becomes damaged until the project is finally accepted. When, in the judgment of the ENGINEER, such defects or damages are the result of poor workmanship or failure to meet the requirements of the specifications, the cost of the necessary repairs or replacement shall be borne by the CONTRACTOR. However, once the CONTRACTOR has completed the mulching of any area in accordance with the provisions of the specifications and to the satisfaction of the ENGINEER, no additional work at his expense will be required, but subsequent repairs and replacements deemed necessary by the ENGINEER shall be made by the CONTRACTOR and will be paid for as additional or extra work.
1204-4 MEASUREMENT AND PAYMENT
1204-4.1 MULCHING. Mulching shall be measured by the square yard (SY) and paid for at the unit price bid for "Mulching" complete in place and accepted by the ENGINEER.