SECTION SLUDGE HOLDING TANK DEWATERING

Transcription

1 SECTION SLUDGE HOLDING TANK DEWATERING PART 1 GENERAL 1.01 SUMMARY A. Section Includes: Dewatering and cleaning of sludge holding tank and sludge disposal. Contractor shall pay for all sludge removal, sludge dewatering, testing and sludge disposal costs. See Section for cleaning and repair of tank interiors SUBMITTALS A. Plan: Proposed dewatering and cleaning plan including work sequence, equipment types and location, and disposal arrangements. B. List of contractor experience in cleaning municipal sludge holding tanks or anaerobic digesters including references (name, location, and phone number) of 5 recent projects within the last 5 years QUALITY ASSURANCE A. Regulatory Requirements: Comply with applicable codes, OSHA, NFPA, and California Regional Water Quality Control Board. B. Experience: Sludge holding tank cleaning contractor shall have recent experience cleaning sludge holding tanks or anaerobic digesters for at least lw municipal facilities of similar or larger size and capacity within the last 5 years.> PROJECT CONDITIONS A. Sludge Holding Tank headspace consists of flammable methane gas. 1. Sludge Holding Tanks are permit-required confined space subject to OSHA requirements. B. Sludge Holding Tanks contain digested sludge with a total solids concentration between 1 to 4 percent. C. Digested sludge typically contains sludge, grit, rags, sand, plastic material, and other debris. D. OWNER will drain the Sludge Holding Tank to approximately to elevation leaving approximately 50,000 gallons of digested sludge remaining for CONTRACTOR to dispose of. E. Sludge Disposal: 1. CONTRACTOR may provide portable dewatering equipment to be located at staging areas as indicated on the Drawings. CONTRACTOR shall be responsible for disposal of digested sludge contents or sludge cake (if using dewatering equipment) off-site to an approved disposal facility permitted by the California Regional Water Quality Control Board. SLUDGE HOLDING TANK DEWATERING pw.//carollo/documents/clienuca/livermore/77coa12/specifications/13215 (Final) SECTION PAGE 1

2 2. Plant will accept clear decant (centrate or filtrate) from the portable dewatering process at the Emergency Holding Basin indicated on the Drawings. Any temporary pumps, piping, and appurtenances required to transport decant to the Emergency Holding Basin area shall be provided by CONTRACTOR. Contractor shall notify plant staff 48 hours in advance of discharging filtrate to the Emergency Holding Tank. 3. Roadways at the plant are frequently used by trucks and must not be impeded. Temporary piping must be protected and maintained for the duration of its use SEQUENCING AND SCHEDULING A. Observe restrictions as specified in Section Work Restrictions. PART 2 PRODUCTS Not Used. PART 3 EXECUTION 3.01 INSTALLATION A. Provide submersible pumps, piping, and trucks as required to remove digested sludge from the Sludge Holding Tank. B. Maintain between 0-inch to 6-inch positive air pressure within Sludge Holding Tank at all times. Provide adequate fresh air to meet requirements of OSHA and NFPA 820. C. Provide a clean and safe work area in the emptied Sludge Holding Tank as needed for other trades after sludge dewatering and disposal is completed. END OF SECTION SLUDGE HOLDING TANK DEWATERING pw://carllo/documents/client/ca/livermore/7700a12/specifications/13215 (Final) SECTION PAGE 2

3 2.05 FINISHES A. Steel Plates, Structural Shapes, and Fabricated Assemblies: Bare, but prepared for coating as specified in Section PART 3 EXECUTION 3.01 INSTALLATION A. Weld structural framework together. B. Center radial joints between roof plates on radial arched steel beams. C. Continuously weld roof plates to radial arched steel beams. Seal weld faying surfaces between roof plates and radial arched steel beams. D. Continuously butt weld or lap weld circumferential joints between roof plates. Seal weld faying surfaces between roof plates. E. Continuously seal weld faying surfaces between structural framework and roof plates. F. Continuously weld roof plates together to provide gastight and watertight cover. G. Do not drill, cut, or punch bolt holes in roof plates. H. Seal weld bolt heads and nuts. I. After dome has been erected, very slowly and carefully remove temporary dome erection supports. Do not eccentrically load erection supports. J. After Erection, Welding, Testing, and Final Inspection: 1. Coat covers as specified in Section FIELD QUALITY CONTROL A. Testing may be done in conjunction with testing specified in Section B. After field erection is complete, but before painting and insulating, test cover for gastightness. C. Carefully clean welds with wire brushes. D. Fill Tank with Water and Trap Air Under Cover. 1. Contractor shall fill the tank with secondary effluent from the secondary clarifier effluent box and dispose off the water back to the secondary clarifier effluent box after testing. E. Provide 20 inches water column air pressure underneath dome during testing for the entire duration of the soap suds test. F. Check welded seams and appurtenances for leaks with soap suds solution. pw://carallo/documents/client/ca/livermore/7700a12/specificatinns/13233 (Final) SECTION PAGE 4

4 2.03 A. Type: All welded construction, steel dome consisting of top steel plates, radial arched steel beams, purlins, peripheral tension ring, and center compression ring. B. Vertical Dome Radius: Approximately 1.5 times cover horizontal diameter. C. Spacing of Radial Arched Steel Beams: Maximum 8 feet apart at dome perimeter. D. Connect radial arched steel beams at perimeter to peripheral tension ring and at center to circular compression ring. E. Use of Shell Plates as Part of Tension or Compression Rings: Prohibited. F. Dome Supports: 1. Dome shall be supported by radial supports equally spaced around periphery of dome and welded to edge of dome. Radial supports shall be supported on top of concrete wall. 2. Radial supports shall be free to move radially. Support on low friction polytetrafluoroethylene (TFE) bearing, or other bearings acceptable to ENGINEER. 3. Wind and seismic loads from the steel dome shall be transmitted to the top of the wall through the radial supports in a direction tangent to the wall at each support. 4. Hold downs shall be provided at each radial support to prevent uplift of the dome. G. Tie Rods: Prohibited. H. Vertical Skirt Plate: Able to trap digester gas underneath cover. 1. Liquid seal laundered manufactured by cover manufacturer to work together with cover as shown on the Drawings. J. Structural Members: 1. Able to allow cover to be self-supporting when tank is empty. 2. Arranged and located to not interfere with cover appurtenances. K. Welding: 1. Shielded arc in accordance with AWS D1.1 gastight welding standards. 2. Minimum Weld Size: 1/4 inch. 3. Minimum Seal Weld Size: 1/4 inch APPURTENANCES A. Center Gas Collection Domes: Manufacturer's standard, unless otherwise indicated on the Drawings. B. Gas Safety Devices, Manholes, Sample Wells, and Flanged Nozzles: Manufacturer's standards unless otherwise indicated on the Drawings or specified elsewhere. pw://carolloldocuments/client/ca/livermore/770oa12/specifications/13233 (Final) SECTION PAGE 3

5 B. Shop Drawings: 1. Detailed construction sequence. 2. Materials, members, supports, attachments, location and size of nozzles, and appurtenances. 3. Layout of structural members and appurtenances. C. Calculations: 1. Design data and design calculations, including wind and seismic calculations, performed by a registered civil or structural engineer registered in state where Project is located. 2. Detailed analysis of anchorage, cover to concrete connection, and top angle design QUALITY ASSURANCE A. Welder Qualifications: Certified by AWS for required welding PROJECT CONDITIONS A. Digester Contents: Mixture of pre-thickened primary sludge and thickened waste activated sludge from municipal wastewater treatment plant, including organic and inorganic solids, grit, grease, scum, gas, and industrial solvents; heated normally to 95 degrees Fahrenheit; with the following characteristics: 1. Average Solids Concentration: From 1 and 4 percent by weight. 2. Optimum Operating ph: Near neutral but may vary at times from 4 to 11. B. Digester Gas: Between 30 and 50 percent by weight hydrogen sulfide, hydrogen, and nitrogen concentrations; between 50 and 70 percent by weight methane; containing significant quantities of fine particulate matter, moisture, and greasy oils; with following characteristics: 1. Specific Gravity: Approximately Net Heating Value: 550 British thermal units per standard cubic foot. PART 2 PRODUCTS 2.01 MANUFACTURERS A. One of the Following or Equal: 1. Eimco Corporation, Salt Lake City, UT. 2. WesTech, Salt Lake City, UT MATERIALS A. Structural Steel: In accordance with ASTM A 36. B. Minimum Thickness of Structural Steel Members Including Plate: 1/4 inch. C. Anchor Bolts and Other Bolts, Nuts, and Washers: Type 316L stainless steel. pw.1/caralla/documents/client/ca/livermore/7700a12/specifications/13233 (Final) SECTION PAGE 2

6 SECTION PART 1 GENERAL 1.01 SUMMARY A. Section Includes: Steel dome digester cover. B. Related Sections: 1. Section Quality Control. 2. Section Seismic Design Criteria. 3. Section Wind Design Criteria. 4. Section Structural Steel. 5. Section Coatings REFERENCES A. American Institute of Steel Construction (AISC): Steel Construction Manual. B. American Society for Testing and Materials (ASTM): 1. A 36 - Standard Specification for Carbon Structural Steel. C. American Welding Society (AWS): 1. D1.1 - Structural Welding Code - Steel DESIGN CRITERIA A. Design cover in accordance with AISC 360 using allowable stress design. B. Design for the Following Loads: 1. Dead Load: According to the manufacturer's design. 2. Uniform Live Load: 40 pounds per square foot. 3. Vacuum Load: 2 inches of water column. 4. Internal Gas Pressure: 14 inches water column. 5. Concentrated Live Load: 1000 pounds on cover framework located at rafter mid span. C. Seismic Design Criteria: As specified in Section D. Wind Design Criteria: As specified in Section E. Structural Steel: As specified in Section SUBMITTALS A. Product data. pw://carclo/docurments/clientca/livermocrs/7700ai2/specifications/13233 (Final) SECTION PAGE 1

7 G. Carefully chip out welds at leaks to good metal, and then reweld and retest MANUFACTURER'S FIELD SERVICE A. Require manufacturer to check complete installation and inspect testing of covers. END OF SECTION pw://carallo/documents/clien/ca/lvermore/7700a12/specificatonsl/13233 (Fina) SECTION PAGE 5

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