Case Study: Closure of an Earthen Lagoon
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http://www.extension.org/67664 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
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Case Study: Closure of an Earthen Lagoon
- 3. Background Information Caged egg-laying operation with 6 houses Lagoon size – unknown 11 to 12 acre-ft of storage (size of football field 10 feet deep) Operation began in late 1970’s Operator chose to shut-down facility in May 2006 Demonstration project Determine costs for other lagoons across the state Address concerns in an impaired watershed Properly close to mitigate water quality impacts
- 5. Methodology Survey of existing site Determine extents of lagoon Approximate volumes Utilities Soil sampling to determine in-situ materials and check for leakage Construction Specifications Site-specific Compilation of appropriate portions of NRCS national construction standards
- 6. Methodology (continued) Draft Closure Plan and approval Construction Plans Contracting Construction Oversight Final Check-out
- 8. Digging for Information Field Engineer Technician Located the contractor that originally built the facility Confirmed that there were two lagoons No plans available Found out when water was hooked up for the site 1978
- 10. Surveying Attempts Tried to use Sludge Judge – nothing went into the tube Tried pacing and using a range pole to establish depth Used Survey Grade GPS unit Took Surface Shot Used range pole to probe and determined Depth of sludge Depth of wastewater
- 11. Aerial Photo Reconnaissance Source: 1960 Aerial Photo
- 12. Don’t Forget Power Lines
- 13. Survey Data Collected & CAD Approximately 2,000 data points were collected or calculated (34 different field codes were used) Approximately 200 points were taken on the surface and probed to obtain bottom of pond elevation and wastewater level Modeled Existing Pond with Sludge Bottom of Pond Wastewater Level in Pond Proposed Final Grade Existing Concrete Slabs
- 14. Closure Plan Meetings with TCEQ Review of draft plan approved by TCEQ Final closure plan to be completed after vegetation is established
- 15. Site Specific Construction Specifications – March 2008 Overview Scope & Location Utilities Safety Pollution Control SWPPP Mobilization and Demobilization
- 16. Site Specific Construction Specifications – March 2008 Overview (continued) Removal of litter, sludge and wastewater Structure Removal Earthfill and Excavation Seeding and Mulching Construction Survey
- 18. Contracting – Turn Key Sludge to be removed and land applied – 18,500 CY Removal of Concrete Slabs Earth moving – compacted fill estimated at 27,000 CY Final Seeding of Site Bids received began around $1.8M and exceeded $3M
- 19. Contracting – Phase 1 Modified to only include removal and stockpiling of sludge in windrows on-site Awarded Bid $3.25 per CY of sludge removed $10 per 1,000 gallons of water for pumping to neighbor Local SWCD found neighbor to take water Total cost $58,500 Completed September 2009
- 20. Bid Closes and what happens
- 25. Phase 2 – Sludge Hauling and Land Application Local SWCD, NRCS and TSSWCB and found a landowner that wanted the material Landowner receiving sludge contracted out of their own pocket to have sludge hauled and spread on their property Sludge hauler was from the Texas Panhandle Some of the cost was for mobilization/demobilization Application started January 2011 and was postponed because of rainfall until April 2011
- 27. Slabs to be removed
- 28. Phase 3 – Final Grading Contract Awarded August 2011 Final grading completed September 2011 DOES NOT INCLUDE SEEDING AND REVEGETATION – currently in a drought Silt fencing is in place
- 29. Challenges for Final Grading Power poles on-site Agreement was from 3 years ago when initially bid Had to renegotiate cost with power company
- 30. Photo of finished grade Photo of work in progress
- 31. Phase 4 – Vegetation and Paperwork Vegetate the site – Indian Grass, Klein Grass, Switch Grass, Sideoats Grama, Plains Bristlegrass, Wild Rye, Rye Grass Landowner deed recordation Final Closure Plan
- 32. SLUDGEANALYSIS 2006 Range Average Nitrogen (%) 1.2-2.8 2.11 Phosphorus (%) 4 - 4.7 4.4 Potassium (%) 1.6 - 3.8 2 Calcium 16.6 - 38.9 21.8 Magnesium (%) 1.7 - 2.4 2.1 Sodium ($) 0.5 - 0.7 0.6 Zinc (%) 0.06 - 0.19 0.14 Iron (%) 0.45 - 1.0 0.6 Copper (ppm) 61 - 261 197.7 Manganese (%) 0.1 - 2.2 1.8 pH 7.0 - 7.3 7.2 Conductivity 6280 Total Carbon (%) 19.7 Dry Matter (%) 24 - 53 33.6 P2O5 (lbs/dry ton) 185 210 200 P2O5 (lbs/wet ton) 48-103 67
- 33. Sludge Analysis - 2009 % (dry basis) N 1.5 P 5.7 K 1.6 Dry Matter 74%
- 34. WASTEWATER ANALYSIS2006 N % 0.099 P ppm 172.4 K ppm 3171 Ca ppm 479.7 Mg ppm 147.7 Na ppm 901 Zn ppm 5.76 Fe ppm 7.04 Cu ppm 1.079 Mn ppm 4.967 pH 7.8 Conductivity umhos/cm 16580 Total Carbon % 0.282 NH4-N % 0.1525 Date Received 2/24/2006 Color Brown/ Pink P2O5 ppm 391.348
- 35. EFFLUENT ANALYSIS2007 N % 0.0174 P % 0.0073 K % 0.1619 Ca % 0.0051 Mg % 0.0098 Na % 0.0327 Zn ppm 0.13 Fe ppm 2.66 Cu ppm 0.05 Mn ppm 0.30
- 36. Cost Component Quantity Cost per unit Cost Sludge and Water Removal – stockpile on-site 18,000 CY $3.25/CY $58,500 Wastewater None $10/1,000 gallons N/a Sludge Hauling and Application 12,103 Tons $7.484/Ton $90,580 (basically $5.03/CY) Subtotal for removal $149,080 Concrete Slab Removal 1,800 CY $11.60/CY $20,880 Earthwork 27,200 CY $2.50/CY $68,000 Miscellaneous $2,100 Seeding 10 acres $180/Acre $1,800 Subtotal for Site Work $92,780 TOTAL TO DATE $241,860
- 37. Additional Costs Engineering – Surveying, Civil 3D, Drawings, Specifications, Design Report Closure Plan Development Contracting Time and Expenses Meetings, coordination, and other communication time Soil, Waste, and Wastewater Analysis Moving Power Lines Final Establishment of Vegetation
- 38. Thank you!
Notas do Editor
- I will be presenting some information on the closure of a poultry lagoon in Texas
- This is a photo of the facility with the full lagoons in the foreground taken in Spring 2006.
- This was a caged egg-laying operation which utilized 6 houses. It had converted to a dry waste management system. The lagoon size was initially unknown, but held approximately 11-12 acre-feet of storage, or 14,800 cubic meters of wastewater, which is one of the smaller lagoons in the area. The initial operation began in the late 1970’s and the operation shut-down in May 2006. This was a demonstration project between the Natural Resources Conservation Service (NRCS), the state soil conservation agency, Texas State Soil & Water Conservation Board (TSSWCB) and the local Soil & Water Conservation District. The purpose of the demonstration was to: establish costs for this practice as there are numerous similar situations across the state and remove a potential source of contamination from an impaired water shed.
- After taking samples, we did some digging at the local field office. From this aerial photo, we were able to determine that there were two lagoons and one mini pond.
- Now moving back to the actual methodology for the project. This consisted of surveying the existing site, soil sampling, construction specification and much more.
- Sampling of Sludge material that was sent to Texas A&M for evaluation
- This is a plan view of the operation. When the site was constructed initially the lagoon was built at the top of the hill, dirt for the lagoon was excavated and used as a building pad for the slab thus eliminating all outside drainage. The initial grade of the site prior to the installation of the facility is shown with green arrows. The grade is approximately 0.2% over the entire site.The entire site is less than 11 acres or 44,515 square meters, and the system was likely designed as a total evaporation system. The wastewater was recycled to flush the concrete alleys. The only freshwater was from the drinking nozzles.
- The use of a local technician allowed us to track down the original contractor, water hook-ups and so forth. However, the contractor could not recall any of the dimensions or details on the construction of the lagoon.
- Samples were taken to determine if the material was the same as indicated on the soils maps and to determine if there was any seepage into the surrounding soil at the sampling locations. The sampling indicated that the soils were acceptable for an in-situ lining material and there was not any indication of seepage from the lagoon.
- In order to establish the boundaries of the lagoons under the sludge and wastewater, we tried several methods until we came up with one that worked. The sludge judge did not work because the waste was too thick and would not go into the tube. Attempted to pace and use a range pole to establish the depth while dragging a raft, but did not have an accurate surface elevation or horizontal control. Finally, utilizing a survey grade GPS unit, along with a range pole, we were able to obtain a surface elevation, probed to the bottom with the range pole and took readings for the depth of the sludge and the wastewater level.
- Double decker rows of buzzards are missing now!
- Using old aerial photos and the United States Geological Survey quadrangle map which provides contours , we were able to determine what the site looked like prior to the installation of the poultry operation.
- It is important to remember both above ground and below ground utilities. In this case, the contractor had to obtain permission from the utility company in order to work under the line and this had to be address in the plans and specifications
- After all surveying work was completed, there were approximately 2,000 data points that were used to model using Eagle Point at the time the various levels of sludge, wastewater and then develop a final grading plan and associated quantities.
- Additionally, a draft closure plan was developed prior to any work for TCEQ review and approval. The final closure plan will be completed after vegetation is established on-site.
- These construction specifications addressed typical items that would be seen in most construction projects for NRCS.
- Additionally, the specifications included requirements for the removal of litter, sludge and wastewater, structure removal, earthfill and excavation, seeding and mulching, and final construction survey
- A design report, along with engineering drawings and construction specifications were prepared. I have included a handout with sample construction specifications for the entire project.
- Once all the engineering and technical work was completed, the initial thought for contracting the work was to have a turn key package where the contractor took care of all sludge hauling and land application, including finding the land to apply the sludge. The bids started at $1.8 million….. since there was not that much funding available, the project was split into various phases with our local offices doing much of the legwork.
- The project was broken into three phases initially; however, it is in its fourth phase at this time. Phase 1 consisted of removing the litter and stockpiling on-site
- As soon as the bid was closed, the site received 5-6 inches of rain. The contractor was responsible for all costs associated with this water; however, a stipulation was added that the contractor would be paid $10/1000 gallons if there was any additional rainfall.
- Here are some photos of the dewatering of the lagoon in phase 1
- The contractor used multiple types of equipment and conveyors to remove and stack the material on-site. Note: The sludge looks like a typical clay soil.
- Initially, a stationary hopper as shown on the left was used. The contractor switched after the first couple of days to a vibrating hopper to address the material sticking to the sides of the hopper.
- Here are some photos of the sludge stockpiled on-site and the empty lagoons.
- For phase 2, the local offices were able to find a landowner that wanted the material and was willing to pay for the transportation and spreading of the material. There was a significant amount of time spent finding this landowner, as the local applicators in the area were accustomed to poultry litter, but did not have equipment for spreading the sludge.
- The sludge applicator did a terrific job of removing all of the sludge from the site.
- The only thing remaining was the slabs to be demolished in Phase 3.
- Phase 3 was initially to include final grading and vegetation establishment. However, with the current drought situation in Texas, it was decided to remove the vegetation requirements from the contract. The site has an average slope of 0.2%, and silt fence was installed to reduce the possibility of erosion.
- One of the challenges for the final grading was moving the power poles that were on-site to avoid miniature islands around the poles. The agreement was from 3 years prior and the costs for moving the poles had more than tripled. With some good notes and negotiating skills, the local technician was able to reduce the cost to close to the original quote from 2008.
- This is a photo of the final site after grading and a close-up of the silt fence.
- The last phase consists of establishing the vegetation on-site. Since the site received some rainfall earlier this month. We decided to go with a native mixture for the site and planting should be completed by the end of the day. Additionally, the landowner will need to deed record the location of the lagoon as the designed earthfill and compaction requirements were not intended to support a structure and some shrinkage is expected. After vegetation is established, a final closure plan will be documented.
- Saqib Mukhtar from Texas A&M had agreed to perform the analysis of the sludge along with one of his graduate students. There were 8 samples taken. The sludge resembled dirt and had very little odor to it. This chart shows an average of the samples for the sludge.
- As the sludge was stockpiled, the local office took samples of sludge and had them analyzed. This is the average of approximately 20 samples that were taken, which is approximately 1 sample for every 1,000 CY.
- There were a few samples of wastewater that were collected and analyzed at the same time as well. This shows the results from the analysis in 2006.
- There were a few samples of wastewater that were collected and analyzed at the same time as well. This shows the results from the analysis in 2006.
- Here are the contractor costs to date… the $90,580 for sludge hauling and application was paid by the landowner receiving the sludge. The total spent by NRCS and TSSWCB to date is approximately $150k
- There is a significant amount of time and staff resources spent on this project that correlate to additional costs that are not included in the contracting costs.