Presentation on theme: "Closure of Animal Waste Lagoons John W. Worley. Lagoon Closure u What is required? u What are options for managing an inactive lagoon? u What does an."— Presentation transcript:
Lagoon Closure u What is required? u What are options for managing an inactive lagoon? u What does an inactive lagoon contain?
What Is Required? u New or existing CAFO’s (1,000 Animal Units or more) u Notify EPD within 3 months of the date lagoon ceases to be used. u Close within 24 months (18 if closed involuntarily)
What Is Required? u Remove all waste from lagoon u Land apply at agronomic rates u Do not allow discharge to surface waters
What Is Required? u Rules refer throughout to the NRCS Field Office Technical Guide for guidance in acceptable practice. u Conservation Practice Standard 360, Closure of Waste Impoundments
Options for Closing a Lagoon u Complete Closure and Fill (reclaim land surface) u Breach the Lagoon Berm u Convert to Farm Pond –Livestock Watering –Irrigation Storage –Fish Pond
All Options u Remove conveyances (Fill pipes) u 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 u Some sludge may remain if it “will not pose a threat to the environment”
Close and Fill u Remove berms and restore land to approximate original shape u Excavated (Cut) Impoundments –Mound soil inside pond to allow for settling and encourage surface water runoff –Establish vegetation to prevent erosion
Breach the Berm u 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 u Must meet structural requirements for final use u Must remove “all” sludge u Test water for safety. For livestock watering, Nitrate N below 30 ppm, Dissolved Oxygen more than 3 ppm (3 mg/L).
Other Considerations u If sludge is allowed to dry, it will decompose releasing odors and nutrients (can last for years) u Safety (fencing, signage) should be considered throughout the process u Poultry lagoons will contain oyster shells that are very difficult to remove by agitation
What does an Inactive Lagoon Contain? u 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? u 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? u Wide variation u Ranges from $0.01 to $0.05/gal u For 1-million gallon lagoon (1/2 acre 6-feet deep)- $10 to $50 thousand u Average Cost $42,000 per acre to close lagoon by NRCS standards (Based on 1995 North Carolina Data) u 2-acre swine lagoon recently converted for approx. $15,000 in South Georgia u Recent estimate for 4-acre lagoon - $100,000
Geotubes for Sludge Removal u Provides flexibility in time and space –Solids can be stored in tube until ready to use –Solids are more transportable u Liquid can be returned to lagoon to remix and repump u More expensive than pumping on a nearby field IF that is an option