Dane County Stormwater Manual

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====== Polymer and Other Additives ======

The land application of additives, such as polyacrylamide (PAM) and other polymers, can temporarily reduce erosion through the bonding of soil aggregates.  The resulting soil surface is significantly more resistant to erosion than untreated soil.

Additives are 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. This practice is typically used on construction sites where land disturbing activities or winter shutdown prevent establishment of [[seeding|vegetation]]. The use of additional practices, such as [[mulching]], may significantly increase the effectiveness of the additive.

**Advantages**
  *Effective in preventing erosion
  *Cost effective
  *Reduces erosion during winter months, when vegetation cannot be established)

**Disadvantages**
  *Must be reapplied whenever the soil is disturbed and after moderate rainfall
  *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
  *Cannot be used within 30 feet of state water bodies)

=====Selection=====
There are many commercially available additives in a wide variety of formulations. In addition to polymers, there are products including cellulose, starch, vegetable-based gums or rubber materials used as mulch tackfiers, and pre-mixed products containing natural or synthetic binding agents combined with a fibrous or mulch component (e.g., bonded-fiber matrix). Additives shall be utilized according to all manufacturers’ instructions and specifications.

The Wisconsin Department of Transportation (WDOT) maintains a list of approved additives, which can be found on the [[https://wisconsindot.gov/Documents/doing-bus/eng-consultants/cnslt-rsrces/tools/pal/pal.pdf|Product Acceptability List]] under "Tackifier" and "Soil Stabilizer".

=====Application=====
As application rates will vary depending upon the product used, the time of year, and the individual site characteristics, additives 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, additives may not be applied within 30 feet of any state water bodies.

Reapplication is required after any site disturbance and moderate storm events.  Because additives breaks down over time, reapplication is necessary to maintain effectiveness.

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

=====Documentation=====
Those utilizing additives as an erosion control practice must maintain an inspection log that is readily attainable by Dane County Erosion Control Inspectors.  Site documentation requirements include:

  *Product Type
  *Method of Application
  *Date, rate and area of application
  *Dates and amount of rainfall
  *Name of applicator

=====Maintenance=====
  *Applied areas shall be inspected weekly and after each rainfall event for evidence of rill erosion, requiring reapplication
  *Reapplication per manufactures’ specifications
  *Reapplication after any site disturbance

=====Method to Determine Practice Efficiency=====
The efficiency of additives depends on the individual site characteristics, the type of additive used, the rate of application, the time of year applied, and the use of additional practices.  Any disturbance to the application area, such as vehicle traffic, grading, and moderate storm events greatly reduces the efficiency of the practice and requires reapplication to prevent soil loss.  However, when properly applied, additives have the ability to reduce soil loss by 50%.

==References==
  *[[https://dnr.wisconsin.gov/sites/default/files/topic/Stormwater/1050LandApplAdditives.pdf|Wisconsin DNR Land Application of Additives for Erosion Control Technical Standard 1050]]