water tank rehabilitation for a small community
DESCRIPTION
Presented at the Arizona Water Association (AZWA) Conference, Glendale, May 2010TRANSCRIPT
Water Tank Rehabilitation for a Small Community
Presented By:
Ajay Kashi
Gannett Fleming Inc.
Water Tank Rehabilitation for a Small Community
TOWN OF BOWIE LOCATION MAPTOWN OF BOWIE LOCATION MAP
Water Tank Rehabilitation for a Small Community
PRESENTATION OVERVIEW Introduction Objective Project Funding Project Execution Lessons Learned
Water Tank Rehabilitation for a Small Community
INTRODUCTION History & Background
Approximately 70 years old Privately owned until 1985 Currently Maintained & Operated by BWID
Existing Water System Two (2) Groundwater Wells One (1) 150,000 Gallon Storage Tank Two (2) Hydro-pneumatic Tanks 2”, 4” and 6” Waterlines
Water Tank Rehabilitation for a Small Community
CONDITION OF THE TANK Exterior
Water Tank Rehabilitation for a Small Community
CONDITION OF THE TANK Interior
Water Tank Rehabilitation for a Small Community
PROJECT OBJECTIVE Restore Health and Safety
Replace or Rehabilitate the Tank Eliminate Rust and Deterioration Safe Environment for the Operators
Water Tank Rehabilitation for a Small Community
PROJECT FUNDING Completely Funded by USDA-RD (United States
Department of Agriculture - Rural Development) Gannett Fleming Inc, was selected as Consulting
Engineers to prepare a Preliminary Engineering Report (PER)
Water Tank Rehabilitation for a Small Community
PER (Comprehensive Report) Thorough Site Investigation Discussions with the BWID to identify
Operations and Maintenance issues Financial Information Alternative Improvements Considered Engineer’s Estimate of the Costs Alternative Improvement Recommendation Rural Development Approved Funding for Tank
Rehabilitation
Water Tank Rehabilitation for a Small Community
PROJECT EXECUTION Construction Phase Services
Gannett Fleming provided
Project Representative
Services during Rehabilitation
Bypass Piping Modifications
Water Tank Rehabilitation for a Small Community
PROJECT EXECUTION Guardrail Installation according to OSHA
Standards
Water Tank Rehabilitation for a Small Community
PROJECT EXECUTION Tank Interior Cleaning
Water Tank Rehabilitation for a Small Community
PROJECT EXECUTION Interior after Blasting
Water Tank Rehabilitation for a Small Community
PROJECT EXECUTION Interior Inspection and Tank Floor Cost Evaluation
Water Tank Rehabilitation for a Small Community
PROJECT EXECUTION Tank Floor Installation
Water Tank Rehabilitation for a Small Community
VACUUM TEST Welded Joints were tested for
air-tightness
Water Tank Rehabilitation for a Small Community
PROJECT EXECUTION Interior Inspection Prior to Coating
Water Tank Rehabilitation for a Small Community
PROJECT EXECUTION Epoxy based NSF 61 Approved
Interior Coating Three Coat System
Prime Coat (4 mils) Intermediate Coat (5 mils) Finish Coat (5 mils)
Welds, seams and irregularsurfaces were coated with brush
Smooth surfaces were coatedwith rollers
Water Tank Rehabilitation for a Small Community
PROJECT EXECUTION NSF 61 Approved Interior Coating
Sealant (Polyurethane Elastomeric Adhesive) for Roof Plate Lap Joints
Water Tank Rehabilitation for a Small Community
Tests for Interior Coating System Dry Film Thickness Test Holiday Test (Low Voltage Wet Sponge Test)
Water Tank Rehabilitation for a Small Community
PROJECT EXECUTION Exterior Coating (Epoxy Based)
Pressure Washed According
to SSPC Standards Two Coat System
Prime and Finish Coat Total System Thickness
of 5 – 8 mils (DFT)
Water Tank Rehabilitation for a Small Community
PROJECT EXECUTION Disinfection
AWWA C652 Stds and ADEQ Bulletin No. 8 Interior Pressure Washed prior to Disinfection 200 mg/l Available Chlorine was Sprayed on the
Interior Surface Water allowed inside after 30 minutes of
Disinfectant Retention Time
Testing BAC-T for Coliform Organisms
Water Tank Rehabilitation for a Small Community
LESSONS LEARNED Thorough Tank Inspection is Critical Prior to start of
the Project Thorough Interior Surface Inspection after Blasting is
Essential Confined Space Entry
Entry Permit and Procedures were required for the Contractor and Site Inspectors according to OSHA
Water Tank Rehabilitation for a Small Community
ACKNOWLEDGEMENT USDA Rural Development Bowie Water Improvement District, Town of Bowie
Water Tank Rehabilitation for a Small Community
SAND BLASTING
• Dry Abrasive Blasting• The abrasive media was Silica Sand coated with
Resins to prevent creation of dust during blasting process.
• Abrasive Media Particle size range between 10 micrometer to 150 micrometers.
Vessel containing abrasive media
Power supply & Air-Compressor
From the Vessel media is pressurized through a pipe into a hand held nozzle in the end
HOLIDAY TEST INFORMATION
• For Holiday Tests, the Detector is set at 700 Micro-Amps (mA) to set off an audible indicator.
• Low Voltage Holiday Tests are conducted for metal surfaces which have coatings of 20 mils or less.
• High Voltage Holiday Tests are conducted for metal surfaces which have coatings of 20 mils or greater.
DISINFECTION
• Overflow piping need not be disinfected according to AWWA C652 standards for “Disinfection of Water Facilities.”
• Required Chlorine Residual in water according to AWWA C652 Standards is 2 mg/l.
USDA-RD FUNDING CRITERIA FOR BOWIE
• Bowie is a very poor rural community• The funding criteria for a Rural Community is based
on its Median Household Income (MHI). • If the MHI for a Rural Community is LESS THAN 50%
of the MHI for the State, that Rural Community is qualified for a 100% Grant by the USDA-RD.
• MHI data can be obtained from the Department of Labor Statistics.
ANOTHER OPTION FOR FIXING THE TANK FLOOR
• Apply 50 mils of a Solventless Elastomeric Polyurethane immediately after the Prime Coat on the Interior Surface of the Tank including Roof and Rafters.
• Estimated Cost for Applying the Coat was $30K