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Polymer Application

General

Polymers, or anionic polyacrylamides (PAMs), are non-toxic, organic chemicals that can be applied to soil or water and will temporarily bond soil aggregates. The resulting soil surface is significantly more resistant to erosion than untreated soil. Water application of polymers promotes sediment flocculation and coagulation, thereby increasing settling velocity.

PAM is applicable on a wide variety of sites, especially those with steep slopes where traditional practices, such as mulching, are rendered ineffective when used by themselves. PAM may also be used to improve the efficiency of devices that rely on settling of particles in water. This practice is usually used during and after site grading activities, prior to and during the establishment of seed, (refer to Permanent Seeding and Temporary Seeding) or in situations where other practices are unavailable or ineffective due to weather conditions. The use of additional practices, such as mulching, (refer to Mulching) may significantly increase the effectiveness of the practice.

For water application, polymers may only be applied to runoff that has been captured in sediment control devices. Application of polymers in these devices helps sediment suspended in the water to settle out. Polymers may not be applied directly to any surface waters of the state, such as lakes or rivers. When used for water application, polymers should comply with Wisconsin Department of Natural Resource Technical Standard 1051, Interim Sediment Control Water Application of Polymers.

Advantages

  • Effective in preventing erosion
  • Cost effective
  • May reduce turbidity
  • Reduces erosion during winter months, when vegetation cannot be established

Disadvantages

  • Must be reapplied whenever the soil is disturbed and after large storm events
  • May increase the pH of runoff
  • Limited life span
  • Does not provide protection for seed in the summer months
  • Over application may result in negative effects on plants and wildlife
  • Must be approved by WDNR and WDOT before use
  • Cannot be used within 30 feet of state water bodies

Selection

Polymers are available commercially in both granular and liquid forms in a wide variety of formulations. However, both the Wisconsin Department of Natural Resources (WDNR) and the Wisconsin Department of Transportation (WDOT) must approve the polymer before it may be used. Polymers shall be utilized following all manufacturers’ instructions and specifications. A current listing of approved polymers is available from the Product Acceptability List

Application

As application rates will vary depending upon the product used, the time of year, and the individual site characteristics, PAM shall be applied following the WDNR and the manufacturer’s specifications. Over application may result in reduced effectiveness and may have adverse effects on local plant and wildlife communities. As a result, land applied PAM may not be applied within 30 feet of any state water bodies. Reapplication is required after any site disturbance and after large storm events. In addition, because PAM breaks down over time, reapplication, based on manufactures specifications, is required for the practice to remain effective.

Additional practices, such as mulching, are strongly encouraged for use with polymers. The combination of these practices results in enhanced erosion protection, while increasing the success of germination by providing protection for seed.

Documentation

Those utilizing PAM as an erosion control practice must maintain an inspection log that is readily attainable by Dane County Erosion Control Inspectors. Documentation requirements include:
  • Date of application
  • Rate of application
  • Rate of PAM applied (including manufacturer, product name and concentration)
  • Specific area of the site that the practice has been applied
  • Date of inspection
  • Date of construction activities on the application site
  • Dates and amounts of rainfall on the site

Maintenance

  • Applied areas shall be inspected weekly and after each rainfall event for evidence of rill and gully formation
  • PAM shall be reapplied necessary per manufactures’ specifications
  • PAM shall be reapplied after any site disturbance and after large rainfall events

Method to Determine Practice Efficiency

The efficiency of PAM is dependent upon the individual site characteristics, the type of polymer used, the rate of application, the time of year applied, and the use of additional practices. PAM efficiency is also dependent upon site disturbance. Any disturbance to the application area, such as vehicle traffic, grading, large storm events, etc., greatly reduces the efficiency of the practice and requires reapplication to prevent soil loss. However, when properly applied, PAM has the ability to reduce soil loss by 40%.

References