UNDERGROUND STORAGE TANK PERMANENT CLOSURE
PART 3 EXECUTION 3.1 EXAMINATION
A. Evaluate site to determine the potential for encountering contaminated backfill, soil, or groundwater that may require special handling.
B. If during the tank closure process product or product contaminated soil or ground water is discovered, stop closure process and alert Owners representative.
1. If petroleum is present in the soil then it must be reported as a spill to the DEC within two hours. The presence of product may require the installation of one or more ground water monitoring/recovery wells or removal of the tank to take remedial action to clean up the site. Comply with all NYSDEC requirements for contamination remediation.
C. Coordinate with the Owner and the Owner’s Representative to identify an area for stockpiling excavated backfill and soils.
3.2 EARTHWORK
A. Comply with requirements in Section 31 20 00 "Earth Moving" for excavating, trenching, and backfilling.
3.3 PREPARATION
A. Notify the Regional NYSDEC office a minimum of 30 days prior to commencing with tank closure work. This is done by modifying the registration information for the facility on the bulk storage registration application forms supplied by the. Call the regional office to inform the regional bulk storage staff at least three (3) days before commencing with the closure and notify them of the actual date and time of the work.
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C. Comply with NFPA 30 and NFPA 31 requirements for prevention of accidental ignition. D. Drain all usable product from piping back into tank.
E. The Owner shall remove usable product in tank to its lowest draw-off point. Remove any residual fuel from the tank.
F. Flush supply and return piping into the tank with a minimal amount of water. No more than 1 gallon of water per 10-feet of NPS 1-1/2 piping or 2 gallons of water per 10-feet of NPS 2 piping should be used.
G. Clean the tank interior with a high pressure rinse using as little water as possible to remove loose scale, corrosion and residual product. In the case of a fuel oil storage tank where large amounts of sludge and/or tar may be present, it may be necessary to enter the tank and manually remove such wastes. Cleaning by brushing, shoveling and/or scraping may also be required to clean the inside of the tank.
H. Take all necessary safety precautions while cleaning the tank interior and recovering the wastes and drumming them for proper disposal.
I. Pump out any remaining liquid below the draw-off point by use of a hand pump or a vacuum pump (non-sparking) and dispose of the waste water generated by this process in accordance with solid and/or hazardous waste regulations.
J. Modify the existing tank vent to ensure the displacement of tank vapors caused by purging and inerting process are at least 12 feet above grade and 3 feet from any adjacent roof area.
K. Excavate to expose the entire top of the tank. Stockpile excavated materials for backfilling in designated location. Separate and concrete, asphalt and piping from the excavated backfill and soil.
L. Disconnect the fill pipe, gauge pipe, vapor recovery truck connection, submersible pumps or other tank fixtures and all product lines. Cap or plug open ends of lines which are not to be used further to ensure so all vapors exit through the vent line during the vapor-freeing process.
M. Leave the vent line connected until the tank is rendered vapor free and filled. N. Ensure the work area is free of any ignition sources.
3.4 PURGING AND INERTING PROCESS
A. Purging: Use one of the following methods to render the tank safe. In all methods, the tank atmosphere should be checked to ensure that petroleum vapors have been satisfactorily purged from the tank.
1. Dry Ice; 1.5 pounds per 100 gallons of tank capacity. The dry ice should be crushed and distributed evenly over the greatest possible area of the tank’s interior. As the dry ice vaporizes flammable vapors will flow out of the tank. Therefore, observe all safety precautions regarding flammable vapors.
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2. Carbon Dioxide (CO2); an alternative to dry ice is to introduce CO2 gas directly into the tank (via the fill line) to purge flammable vapors. A minimum of one 75 pounds cylinder of CO2 gas per 2,000 gallons of tank volume should be used. Care must be exercised to prevent buildup of any static charge. The nozzle must be bonded or grounded and the gas introduced slowly to reduce static.
3. Nitrogen; the use of a nitrogen gas is an acceptable method for inerting a tank. Vapors within the storage tank must be displaced with an amount of nitrogen gas equal to or greater than the volume of the tank atmosphere. Bond or ground the nozzle or hose to prevent static buildup.
B. Inerting: Ventilate the tank with compressed air through a diffused air blower pipe. Properly bond the air-diffusing pipe to prevent the discharge of a spark. Ensure compressor is providing a clean air supply that is free of volatile vapors. Air pressure in tank shall not exceed 5 psig per square inch gauge.
C. Control ignition sources during tank purging and inerting operations regardless of the chosen method.
D. Test the tank atmosphere with an oxygen meter to ensure that the tank is safe. The oxygen meter will give a reading of % oxygen per volume. A reading of 6 - 7% oxygen is considered a safe condition.
E. Repeat the purging and inerting processes until the tank tests safe. 3.5 ABANDON UNDERGROUND TANK IN PLACE
A. As soon as the petroleum vapors are satisfactorily purged from the tank, cut one or more large holes in the tank top. This can be accomplished by drilling a hole into the tank and using a backhoe to tear a “three-point” hole into the tank.
B. Make a visual observation of the tank interior; if any holes are discovered, then a soil sample from under the tank near the hole shall be taken for examination for the presence/absence of petroleum.
C. Tank Filling Process:
1. Fill the tank with a suitable solid inert material, such as sand or concrete slurry, through the hole in the top of the tank until full.
2. Disconnect and remove the vent line at the tank. Cap and abandon the buried vent pipe running back to the building.
3. Remove any exposed vent piping to 12 inches below grade and cap. 3.6 SITE ASSESSMENT
A. Perform a Phase I Site assessment of the installation in accordance with the NYSDEC SPOTS Memo No. 14 – Site Assessments at Bulk Storage Facilities.
B. Continuously observe the excavation work closely for signs of contamination; stained soil, smelling for chemical or petroleum odors, looking for signs of sheen on water surface. Document field observations and include in the site assessment record.
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C. Perform a bucket test or jar test on a sample of the excavated material. Mix a small quantity of excavated soil in a bucket or jar and clean water. Allow the mixture to settle. Observe the water surface for evidence of sheen. Document field observations and include in the site assessment record.
D. Utilize field instruments such as explosimeters, combustible gas indicators, photoionization detectors, flame ionization detectors, organic vapor analyzers, and/or colorimetric reading tubes as required for on-the-spot analyses for contamination.
E. Sampling for field analysis:
1. Take a minimum of three (3) borings around the tank to groundwater or bedrock. Take soil samples at each boring from a split spoon at 5 feet intervals to a depth of 3 to 6 feet below the tank bottom. Take additional samples at 10 feet intervals, starting at 10 feet below the tank bottom until ground water or bedrock is encountered. If ground water is encountered, take a groundwater sample from each boring. Take a final sample at the soil/water or soil/bedrock interface.
a. If the field instruments do not indicate any signs of contamination in the samples taken, then only send the final sample at the soil/water or soil/bedrock interface to the lab for analysis.
2. Take a sample every 20 feet along the pipe run (or at every joint, if known) and analysis with a field instrument.
3. Utilize headspace analysis for analyzing soil and water samples taken. This involves putting the samples in a jar or bag, sealing it, and after a period of time, analyzing the vapor space in the top of the jar or bag with the field instruments listed above. Document field observations and include in the site assessment record.
F. Sampling for lab analysis:
1. Coordinate lab sampling schedule with a State Certified Testing Laboratory well in advance of work to avoid delays in the schedule. Consult with the lab as to the number and types of samples required for the type of analysis to be done, type of report that is expected and how long it will take to get the results.
2. Ensure proper care and custody of the samples is taken. Sampling procedures including number, type, location, retrieval, care, custody, and analysis samples are thoroughly discussed in the API Publication 1628 “Assessment and Remediation of Underground Petroleum Releases”.
3. If the field instruments do not indicate any signs of contamination in the boring samples taken, then only send the final sample at the soil/water or soil/bedrock interface to the lab for analysis.
4. Prepare a site assessment report that documents how the site assessment was performed, where the samples were taken, dates they were taken, who took them, types of samples, depth of samples, field analysis results and lab analysis reports.
5. Include a photographic record of the site assessment work performed in the report.
6. Include in the report the date of tank closure in place, the method of conditioning the tank for closure in place and the material used to fill the tank.
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A. Backfill and fill excavation with stockpiled excavation material, clean sand or pea gravel in accordance with Section 31 20 00 "Earth Moving" after the NYSDEC Inspector has approved the hole as clean.
B. Restore disturbed grade to match existing in accordance with Section 31 20 00 "Earth Moving". END OF SECTION 02 65 00
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