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Abstract
The closure of earthen lagoons associated with a caged egg-laying operation was used as a case study. This case study presents information on the steps taken to close the lagoons, including topographic survey needs, analysis of sludge and wastewater at different times during the closure process, methods for excavating and removing the sludge, and the costs associated with the closure of earthen lagoons. The sludge has a high fertilizer value for P2O5 and other micro- and macro-nutrients. The cost of the closure for this case exceeded the expected cost for the earthwork for the construction of a new facility
Why Present a Case Study on Propoer Lagoon Closure?
Provide the steps taken to close the lagoons, including topographic survey needs, analysis of sludge and wastewater at different times during the closure process, methods for excavating and removing the sludge, and the costs associated with the closure of earthen lagoons. These steps will hopefully assist others in the future closure of lagoons.
What Did We Do?
Performed closure of earthen lagoons for a caged egg-laying operation that existed for over 35 years in Gonzales County, Texas. The 100 ft by 400 ft football field sized lagoon area with 5 – 12 ft deep sludge had accumulated approximately 20,000 cubic yards of sludge. The photo below depicts the three lagoon areas (Infrared photograph of site depicting two lagoons and smaller wastewater storage area (USDA-NAPP, 1983).
Multiple different options for closure of the lagoon were evaluated. Sampling in-situ materials to determine if the existing system had a realistic potential for seepage. Detailed analysis of the sludge and wastewater were performed throughout the project. A detailed survey of the site determined the existing volumes of sludge and wastewater. Civil 3D and Eagle Point software programs assisted in development of a final grading plan for the site.
Construction drawings and specifications were developed to place the site into pre-existing conditions. The construction project was split into four phases: Phase 1 – Sludge and Wastewater Removal; Phase 2 – Removal of Sludge to Nearby Agricultural Operation; Phase 3 – Demolition of Concrete Slabs and Final Grading; and Phase 4 – Establishing Vegetation on Site
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Site plan generated for construction plans depicting the natural grade compared to the constructed grade of the poultry houses. (USDA-NRCS, Poultry Lagoon Closure Construction Drawings, March 2008) |
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What Have We Learned?
Formal contracting potentially increases the cost of the project; however, observance of worker safety laws is more likely . Initially this project was sent for bid as a turn key project consisting of 18,500 CY of sludge to be removed and land applied, removal of concrete slabs, placement of 27,000 CY of compacted earthfill, final grading and establishment of vegetative cover. As part of the bid, the contractor was to secure a location for the sludge to be land applied or find another use for the sludge. The bids received ranged from $1.8M up to $3M. This level of funding was not available, so the project was split into different phases. By breaking into phases, the cost of the project was reduced by over 75%. Costs for application or hauling of sludge can be reduced by having an agreement in place prior to contracting.
The cost of the project was close to $250,000 for construction and sludge hauling without consideration of other costs, such as engineering design work, sample analysis, and staff time. The earthwork associated with the construction of this site for a new facility with the excavation and placement of 27,200 CY of compacted earthfill would have been completed for approximately $70,000.
With flexible scheduling, it was possible to find a landowner that was willing to pay for the hauling and land application of sludge, which reduced the out-of-pocket expenses for the closure by more than $90,000.
The amount of Phosphorus present in the sludge was compared to the cost of commercial fertilizer. As of February 2011, Rock Phosphate with 32% P2O5 was selling at $160/metric ton (Index Mundi, 11 June 2012), therefore P2O5 was $500 per metric ton. Using the hauled weight of 12,100 tons with a moisture content of 25.9% and 5.66% P and a conversion factor of 2.29 for P to P2O5, there was 1,160 tons (1,054 metric tons) of P2O5. At the rate of $500 /metric ton, the P2O5 in the sludge would have a value of $525,000. There is additional fertilizer value for the other constituents that are not included.
Future Plans
This case study provides much needed data for the closure of similar operations across the United States. The data collected will be used for future closures under the NRCS Environmental Quality Incentives Program (EQIP). The construction specifications that were developed for this project can be adapted into general specifications for future closure projects. Additional work is needed to compare the value of the sludge to a fertilizer value. The potential for a portable pelletizing and bagging system for recycling sludge from lagoons warrants further research.
Authors
Catherine Nash, Water Resources Engineer, USDA – Natural Resources Conservation Service Catherine.nash@tx.usda.gov
Additional Information
“Case Study: Closure of Earthen Lagoon”, An ASABE Meeting Presentation, Paper No. 1336921
Archived webinar – Poultry Lagoon Closure – Case in Progress
Acknowledgements
Contributions from Texas Poultry Federation, Gonzales Soil and Water Conservation District, Texas State Soil and Water Conservation Board (TSSWCB), USDA – Natural Resources Conservation Service (NRCS), Texas Water Resources Institute, Farm Pilot Project Corporation, Inc. (FPPC) and others made this project possible. A special thanks to: John Foster, TSSWCB, and James Grimm, Texas Poultry Federation, for initiating the project and keeping it moving forward; Lee Munz, TSSWCB for assistance with surveying and taking the lead on his first construction project; John Mueller, NRCS for his support and guidance through the process; Ace Fairchild, NRCS, for his enthusiasm and support throughout the project; Wayne Gabriel, NRCS, for assistance with soils identification; Tom Beach, NRCS, for evaluating feasibility of other options for closure; Shawn Higgins for assistance, endurance and encouragement with the development of Engineering Drawings and Specifications. Thanks to Gonzales County Soil and Water District Employees who helped throughout the project, including: Jeremiah Ford, Abigail Lindsey, Shari Johnson, Jessi Goodson and Wain Fairchild. Thanks to TSSWCB staff including: Lawrence Brown, Jeff Cerny, Amy Devereaux, TJ Helton, Dawna Winkler, and Kenny Zajicek. Thanks to USDA-NRCS staff including: James Davis, Andria Heiges, Jeff Porter, Doug Sharer, James Smith, and Millie Stevens. Thanks to AgriLife Extension members: Saqib Mukhtar, Biological and Agricultural Engineering Department; and Sam Feagley, Department of Soil and Crop Sciences. Every person that was asked for assistance responded graciously and enthusiastically in a timely manner.
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