PRACTICE SPECIFICATION

Anionic Polyacrylamide (pam) EROSION CONTROL

1.  MATERIAL

The polyacrylamide used for reducing surface erosion shall meet the
following requirements:

-   be used only if officially labeled for the intended use (e.g.
    labeled for irrigation erosion control or wind erosion control).

-   be of the anionic type meeting acrylamide monomer limits of 0.05
    percent (%).

-   have a charge density of 10 to 55%, by weight.

-   have a molecular weight of 6 to 24 Mg/mole.

-   be designated as "water soluble", "linear", or "non-crosslinked."

-   be mixed and/or applied in accordance with all Occupational Safety
    and Health Administration (OSHA) Material Safety Data Sheet
    requirements and the manufacturer's recommendations for the
    specified use.

-   conform to all federal, state, and local laws, rules, and
    regulations.

2.  POLYMER APPLICATION RATES

For furrow irrigation.

-   Maximum application rate shall be at 10 ppm of pure form
    polyacrylamide, applied on a total product basis.

-   Application shall occur only during the advance phase of surface
    irrigation.

-   Dry or "patch" treatments of PAM shall be placed over an area of the
    first five (5) feet of each irrigated furrow. A starting application
    rate per furrow of 1 ounce per 1000 feet of furrow length is
    recommended. Field adjustment (increase or decrease) to this
    application rate is required. The rate should be adjusted until no
    visible erosion occurs. Do not exceed 3 pounds/acre of active PAM
    per single application event.

For sprinkler irrigation.

-   Application rate shall be 4 pounds/acre of active PAM or less per
    single application event.

For Targeted Wind or Precipitation Areas.

-   The maximum application rate of pure form polyacrylamide shall not
    exceed 200 lb./ac per year.

3.  GENERAL RECOMMENDATIONS

Follow a recommended irrigation water management plan.

Use polyacrylamide on each irrigation that follows a soil disturbance
operation, particularly the first irrigation of the season. Reapply the
polymer when erosion is noted.

Based upon soils, slope, and stream size, the necessary concentration of
polyacrylamide may be reduced. For the best and most economic
concentration, back off on the amount of polymer used until soil
movement is noted, then increase slightly.

Turbulent mixing of the polymer is critical. The following are general
mixing recommendations for granular, liquid and solid PAM for irrigation
applications:

-   Application of PAM should be sufficiently upstream from the
    irrigation set that thorough mixing has occurred. In open ditches
    let water pass over at least one drop or ditch obstruction. In
    earthen ditch a drop dam is recommended. If drop of obstruction is
    not feasible place PAM 100 to 300 feet upstream of first set. This
    may be reduced to 25 to 50 feet if liquid PAM is used.

-   Lack of adequate turbulence is generally indicated by jellying and
    deposition of polymer material downstream of the application point

-   In gated pipe the swirling action of 2 to 3 pipe sections is usually
    enough turbulence to adequately mix PAM. If unable to obtain these
    lengths use inline drop structure or install baffles in the first
    pipe.

-   For closed/pressurized systems liquid application is recommended.
    Ensure that adequate length (100') for the smoother delivery pipe is
    available for mixing. Inline elbows, valves etc. will decrease the
    length required.

-   Solid formulation of PAM should be placed in areas where turbulence
    is occurring. The action of the water dissolves the PAM. Control of
    the concentration is difficult, as location and time are the only
    variables for control. A trial and error approach should be used to
    adjust the amount and location while visually monitoring furrow
    erosion.

For pressurized sprinkler and gated pipe systems, before and after
injecting concentrated liquid PAM (30 to 50% active ingredient) into
irrigation systems, it is a good practice to pump a surfactant (crop
oil) through the injection system (pump, tubing, valves, etc.).
Surfactants provide a buffer between PAM and water so non-flowing PAM
does not contact water and form a gelatinous mass that can plug pumps,
valves and tubing.

For pressurized sprinkler and gated pipe injection, the injection pump
should be started after water is flowing in the sprinkler system and/or
gated pipe system and stopped when the irrigation pump stops.

For PAM injection system a check valve should be installed between the
irrigation supply line and the injection system to prevent water from
entering the injection system and/or PAM supply container.

Always place PAM downstream of screens or filters.

For liquid or granular PAM application to open ditch place the discharge
point at least 2 feet from flowing water. Small splash droplets can
cause the PAM to clog the outlet.

If irrigation water is high in sediment, application of PAM to the head
ditch or lateral may cause excessive sedimentation within the
ditch/lateral and reduce flow capacity. Consideration should be given to
settling out the sediment in a settling pond with increased PAM
application rates or by decreasing flocculation potential by applying
smaller application rates (e.g. 5 ppm) while still controlling erosion.

4.  IRRIGATION STREAM SIZE

Irrigation infiltration can be increased with the application of
polyacrylamide on undisturbed soils. Stream sizes should be increased to
assure reasonable advance times and decrease potential for deep
percolation. Initial stream sizes during advance can be increased (as
much as double or triple) over untreated water while still preserving
most of the erosion reducing effect of PAM. Visual observation should be
made to ensure that erosion at these increased rates is not occurring.

If stream size are increased and re-use systems are not in place,
consideration should be given to cutback irrigation techniques (e.g.
cutting stream flow after completion of the advance phase) in order to
maintain a high irrigation efficiency.

For the most uniform water application, advance streams containing
polyacrylamide should reach the end of the field according to the
following table. Cutoff ratio is defined as the average advance time
(average time it takes the furrow to reach the end of the field) divided
by the set time (total time of irrigation).

  -------------------- ---------------- ---------------- ----------------
                       Recommended                       
                       Cutoff Ratio                      
                       (CR)                              

  System Type          Sandy Soils      Loamy soils      Clayey Soils

  No Re-Use            0.45             0.60             0.70

  With Re-Use          0.25             0.35             0.45

  Blocked Ends         0.85             0.80             0.75
  -------------------- ---------------- ---------------- ----------------

With larger stream sizes and increased infiltration, irrigation water
management adjustments must be made. Set times should be shortened or
irrigation frequency adjusted to reduce deep percolation.

5.  For Targeted Wind or Precipitation Areas

-   Emulsion batches shall be mixed with pure form polyacrylamide not
    exceeding 200 pounds per batch.

-   Application method shall insure uniform coverage to the target area,
    minimizing drift to non-target areas.