closure of animal waste lagoons john w. worley. lagoon closure u what is required? u what are...

Closure of Animal Waste Lagoons

John W. Worley

Lagoon Closure

What is required? What are options for

managing an inactive lagoon?

What does an inactive lagoon contain?

What Is Required?

New or existing CAFO’s (1,000 Animal Units or more)

Notify EPD within 3 months of the date lagoon ceases to be used.

Close within 24 months (18 if closed involuntarily)

What Is Required?

Remove all waste from lagoon Land apply at agronomic rates Do not allow discharge to surface

waters

What Is Required?

Rules refer throughout to the NRCS Field Office Technical Guide for guidance in acceptable practice.

Conservation Practice Standard 360, Closure of Waste Impoundments

Options for Closing a Lagoon

Complete Closure and Fill (reclaim land surface)

Breach the Lagoon Berm Convert to Farm Pond

– Livestock Watering– Irrigation Storage– Fish Pond

All Options Remove conveyances (Fill pipes) Remove as much waste as practical by

conventional pumping methods– Agitate, pump, refill, repeat– Use dredge or similar device to remove

sludge– Pump liquid, remove sludge mechanically

Some sludge may remain if it “will not pose a threat to the environment”

Close and Fill

Remove berms and restore land to approximate original shape

Excavated (Cut) Impoundments– Mound soil inside pond to allow for settling

and encourage surface water runoff– Establish vegetation to prevent erosion

Breach the Berm

Embankment (Fill) Impoundments– Breach berm (embankment) with side

slopes of breach no more than 3:1( or more depending on soil material)

– Deep enough to prevent ponding– Establish vegetation in all areas to prevent

erosion.

3

1

Conversion to Pond Must meet structural requirements for

final use Must remove “all” sludge Test water for safety. For livestock

watering, Nitrate N below 30 ppm, Dissolved Oxygen more than 3 ppm (3 mg/L).

Other Considerations

If sludge is allowed to dry, it will decompose releasing odors and nutrients (can last for years)

Safety (fencing, signage) should be considered throughout the process

Poultry lagoons will contain oyster shells that are very difficult to remove by agitation

What does an Inactive Lagoon Contain?

Liquid Layer– Initially relatively high rates of N, P, K,

organic matter (i.e. 500 ppm nitrogen)– Low nutrient and OM levels after 2 to 3

years (usually less than 100 ppm nitrogen)

What does an Inactive Lagoon Contain?

Sludge Layer– High nutrient content, especially P, K– Fairly high organic matter– High ash (undigestible material)– relatively unchanged over time as long as it

remains wet

What does Sludge Removal Cost?

Wide variation Ranges from $0.01 to $0.05/gal For 1-million gallon lagoon (1/2 acre 6-feet

deep)- $10 to $50 thousand Average Cost $42,000 per acre to close

lagoon by NRCS standards (Based on 1995 North Carolina Data)

2-acre swine lagoon recently converted for approx. $15,000 in South Georgia

Recent estimate for 4-acre lagoon - $100,000

Agitate and Pump

Floating Pump or Dredge

Geotubes for Sludge Removal(Filling)

Geotubes for Sludge Removal(Dewatering)

Geotubes for Sludge Removal(Removal of Solids)

Geotubes for Sludge Removal(Removal of Solids)

Geotubes for Sludge Removal Provides flexibility in time and space

– Solids can be stored in tube until ready to use– Solids are more transportable

Liquid can be returned to lagoon to remix and repump

More expensive than pumping on a nearby field IF that is an option

Questions?