The following are additional recommendations, which may enhance the use of, or avoid problems with the practice.
A. Adding seed to the anionic PAM mixture may provide additional erosion protection beyond the life of the anionic PAM.
B. Mulching is typically needed to protect the seed from the effects of wind and sun. Seed germination is not enhanced or impeded by the anionic PAM mixture.
C. Using a minimum 30 ft setback when applying anionic PAM mixture near surface waters of the state is recommended.
D. Applying anionic PAM mixture to soil may provide benefits of improved water quality, infiltration, soil fertility, and visibility by reducing wind and water erosion.
E. For erosion control, the anionic PAM mixture may be applied upgradient of lands planted in food crops.
F. Application of anionic PAM mixture may be particularly effective in the following situations:
• During rough grading operations
• Phased construction projects
• Stockpiles
• After final grading and before paving or final seeding and planting
• Sites having a winter shutdown
• Agricultural lands where plant residues are inadequate
• Sites receiving final landscaping, but where adequate vegetation cannot be established prior to winter.
G. Application of anionic PAM mixture may not be as effective in the following situations:
• When the soil surface is pure sand or gravel with no fines.
• When applied over snow cover.
H. Visible tracer or colorant to visually track application is recommended.
I. Anionic PAM mixtures may be applied in liquid and granular forms.
J. Application rates of anionic PAM mixtures may need to be adjusted based on soil type, slope, and type of erosion targeted (ie. wind or water). Based on manufacturer's recommendations, higher application rates may be necessary when applied in granular form.
K. Anionic PAM mixtures combined with water are very slippery and can be a safety hazard. Care must be taken to prevent spills of anionic PAM mixtures onto paved surfaces. During an application of anionic PAM mixture, prevent over-spray from reaching pavement, as pavement will become slippery.
L. Care should be taken when applying anionic PAM mixtures in liquid form on saturated slopes due to the possibility of slope structural failure. Anionic PAM mixtures may be applied to steeper slopes when used with other erosion control BMPs such as seed and mulch or erosion mat.
VII. Specifications
Erosion control and stormwater plans specifying anionic PAM mixtures for erosion control shall be in keeping with this standard and shall describe the requirements for applying the practice to achieve its intended purpose.
VIII. Operation and Maintenance
Maintenance will consist of reapplying anionic PAM mixtures to disturbed areas, including high use traffic areas, which interfere in the performance of this practice. Anionic PAM mixture may lose its effectiveness in as little as two months due to weather conditions. Anionic PAM mixtures should be reapplied in areas where wind or rill erosion is apparent and whenever an area has been graded, driven upon, or otherwise disturbed since the anionic PAM mixture was last applied.
IX. References
Bubenzer, G.D., and Patterson, A.E.,
Intake Rate: Sprinkler Infiltrometer, Method of Soil Analysis, Part 1 Physical and Mineralogical Method, Second Edition, Chapter
33, pp. 845-870. (Agronomy Monograph Series #9, 1982).
Managing Irrigation-Induced Erosion And Infiltration With Polyacrylamide, Proceedings From First Conference, University of Idaho Miscellaneous Publication No. 101-96, (Kimberly, Idaho, USDA-ARS Northwest Irrigation and Soils Research Lab, 1996).
Roa-Espinosa, A., Bubenzer, G.D. and Miyashita, E., Sediment and Runoff Control on Construction Sites Using Four Application Methods of Polyacrylamide Mix, National Conference on Tools for Urban Water Resource Management and Protection, Chicago, February 7-10, 2000, pp. 278- (EPA, 2000).
Roa-Espinosa, A., Bubenzer, G.D. and Miyashita, E., Determination of PAM Use in Erosion Control on Construction Sites, 1st Inter-Regional Conference on Environment-Water: Innovative Issues in Irrigation and Drainage, Lisbon, Portugal, September 1998 (Portuguese National Committee of ICID, 1998).
Roa- Espinosa, A., Are there Safety Concerns or Environmental Concerns with PAM? (Dane County Land Conservation Department, 1997).
Sojka, R.E. and Lentz, R.D., “A PAM Primer: A brief history of PAM and PAM related issues,"
http://kimberly.ars.usda.gov, (Kimberly, ID: USDA-ARS Northwest Irrigation and Soils Research Lab, 1996).
Special recognition goes to Steve Decker of Construction Fabrics & Materials Corp. (CFM). Steve was invaluable during the development of this technical standard because of his extensive field experience, his personal commitment to funding the research for toxicity testing, his vision and his steadfast determination to find an environmentally safe and effective erosion control product.
Mulching For
Construction Sites
1058 (06/03)
Wisconsin Department of Natural Resources
Conservation Practice Standard
Note: Words in the standard that are shown in italics are described in X. Definitions. The words are italicized the first time they are used.
I. Definition
Mulching is the application of organic material to the soil surface to protect it from raindrop impact and overland flow. Mulch covers the soil and absorbs the erosive impact of rainfall and reduces the flow velocity of runoff.
II. Purpose
This practice may be used to:
• Reduce soil erosion
• Aid in seed germination and establishment of plant cover
• Conserve soil moisture
III. Conditions Where Practice Applies
This practice may be applied on exposed soils as a temporary control where soil grading or landscaping has taken place or in conjunction with temporary or permanent seeding. Mulching is generally not appropriate in areas of concentrated flow.
IV. Federal, State, and Local Laws
Users of this standard shall comply with applicable federal, state and local laws, rules, regulations or permit requirements governing mulching. This standard does not contain the text of federal, state, or local laws.
V. Criteria
This section establishes the minimum standards for design, installation and performance requirements.
A. Site Preparation:
Soil surface shall be prepared prior to the application of mulch in order to achieve the desired purpose and to ensure optimum contact between soil and mulch. All areas to be mulched shall be reasonably free of rills and gullies.
B. Materials:
Mulch shall consist of natural biodegradable material such as plant residue (including but not limited to straw, hay, wood chips, bark and wood cellulose fiber), or other equivalent materials of sufficient dimension (depth or thickness) and durability to achieve the intended effect for the required time period.
Mulch shall be environmentally harmless to wildlife and plants. Materials such as gravel, plastic, fabric, sawdust, municipal solid waste, solid waste byproducts1, shredded paper, and non-biodegradable products shall not be used.
Mulch shall be free of diseased plant residue (i.e. oak wilt), noxious weed seeds, harmful chemical residues, heavy metals, hydrocarbons and other known environmental toxicants.
Marsh hay shall not be used as mulch in lowland areas but may be used on upland sites to prevent the spread of invasive, non-native species (i.e. reed canary grass) commonly found in marsh hay.
Straw and hay mulch that will be crimped shall have a minimum fiber length of 6 inches.
Wood chips or wood bark shall only be used for sites that are not seeded.
C. Application Rate:
1. Mulch shall cover a minimum of 80% of the soil surface for unseeded areas. For seeded areas, mulch shall be placed loose and open enough to allow some sunlight to penetrate and air to circulate but still cover a minimum of 70% of the soil surface.
2. Mulch shall be applied at a uniform rate of 1½ to 2 tons per acre for sites that are seeded, and 2 to 3 tons per acre for sites that are not seeded. This application results in a layer of ½ to 1½ inches thick for seeded sites, and 1½ to 3 inches thick for sites not seeded.
3. Wood chips or wood bark shall be applied at a rate of 6 to 9 tons per acre to achieve a minimum of 80% ground cover. This application should result in a layer of wood chips or wood bark ½ to 1½ inches thick.
D. Mulch Anchoring Methods
Anchoring of mulch shall be based on the type of mulch applied, site conditions, and accomplished by one of the following techniques:
1. Crimping
Immediately after spreading, the mulch shall be anchored by a mulch crimper or equivalent device consisting of a series of dull flat discs with notched edges spaced approximately 8 inches apart. The mulch shall be impressed in the soil to a depth of 1 to 3 inches.
2. Polypropylene Plastic, or Biodegradable Netting
Apply plastic netting over mulch application and staple according to manufacturer's recommendations.
3. Tackifier
Tackifier shall be sprayed in conjunction with mulch or immediately after the mulch has been placed. Tackifiers must be selected from those that meet the WisDOT Erosion Control Product Acceptability List (PAL). Asphalt based products shall not be applied.
The tackifiers shall be applied at the following minimum application rates per acre:
a. Latex-Base: mix 15 gallons of adhesive (or the manufacturer's recommended rate which ever is greater) and a minimum of 250 pounds of recycled newsprint (pulp) as a tracer with 375 gallons of water.
b. Guar Gum: mix 50 pounds of dry adhesive (or the manufacturer's recommended rate which ever is greater) and a minimum of 250 pounds of recycled newsprint (pulp) as tracer with 1,300 gallons of water.
c. Other Tackifiers: (Hydrophilic Polymers) mix 100 pounds of dry adhesive (or the manufacturer's recommended rate which ever is greater) and a minimum of 250 pounds of recycled newsprint (pulp) as a tracer with 1,300 gallons of water.
VI. Considerations
A. Wood products typically absorb available soil nitrogen as they degrade, thus making it unavailable for seed.
B. The use of mulch behind curb and gutter may not be desirable unless anchored by netting, because air turbulence from nearby traffic can displace the mulch. Consider the use of erosion mat or sod as an alternative.
C. In areas where lawn type turf will be established, the use of tackifiers is the preferred anchoring method. Crimping will tend to leave an uneven surface and plastic netting can become displaced and entangled in mowing equipment.
D. A heavier application of mulch may be desired to prevent seedlings from being damaged by frost.
E. It may be beneficial to apply polyacrylimide in addition to mulch. Refer to WDNR Conservation Practice Standard (1050) Erosion Control Land Application of Anionic Polyacrylamide for information about the advantages and proper use of polymers.
F. Concentrated flows above the site where mulch is applied should be diverted.
G. Mulch should be placed within 24 hours of seeding.
H. Mulching operations should not be performed during periods of excessively high winds that would preclude the proper placement of mulch.
I. Materials such as gravel may be effective for erosion control but are not considered mulches.
VII. Plans and Specifications
