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D.C. Municipal Regulations (Last Updated: September 13, 2017) |
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Title 20. ENVIRONMENT |
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Chapter 20-60. UNDERGROUND STORAGE TANKS - RELEASE DETECTION |
Section 20-6011. INTERSTITIAL MONITORING
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6011.1Interstitial monitoring between an UST system and a secondary barrier immediately around or beneath the UST system may be used, but only if the system is designed, constructed, and installed to detect a leak from any portion of the tank or piping that routinely contains product and also meets the requirements of this section which are applicable to the particular UST system.
6011.2For double-walled UST systems, the sampling or testing method shall be capable of detecting a release through the inner wall in any portion of the tank that routinely contains a regulated substance.
6011.3Where vacuum monitoring is utilized, the vacuum must be maintained at not less than five inches (5") of mercury and shall not exceed manufacturer's instructions. If the vacuum falls below five inches (5") of mercury, the owner or operator shall report a suspected release to the Director. A vacuum shall not be re-instituted more frequently than once every three (3) months without prior approval of the Director.
6011.4For tanks with an internally fitted liner, an automated device shall be used that is capable of detecting a release between the inner wall of the tank and the liner. The liner shall be compatible with the substance stored.
6011.5For UST systems with a secondary barrier within the excavation zone, the secondary barrier shall meet the following requirements:
(a)The barrier, around or beneath the UST system, shall consist of synthetic constructed material that is sufficiently thick and impermeable to direct a release to the monitoring point and permit its detection. The permeability shall be not greater than one millionth of a centimeter per second (10<-6> cm/sec) for the regulated substance stored;
(b)The barrier shall be compatible with the regulated substance stored so that a release from the UST system will not cause a deterioration of the barrier allowing a release to pass through undetected; and
(c)If the tank is cathodically protected, the barrier shall be installed so that it does not interfere with the proper operation of the cathodic protection system.
6011.6An UST system with a secondary barrier within the excavation zone shall use a sampling or testing method that is capable of detecting a release between the UST system and the secondary barrier. The testing or sampling method used shall not be reduced in effectiveness or rendered inoperative by ground-water, rainfall, soil moisture, or any other known interference to the point that a release could go undetected for more than fifteen (15) days.
6011.7The owner or operator of an UST system with a secondary barrier within the excavation zone shall assess the site to ensure that the secondary barrier is always above the ground water and not in a twenty-five (25) year flood plain, unless the barrier and monitoring designs are designed for use under those conditions.
6011.8The monitoring wells for each UST system with a secondary barrier within the excavation zone shall be clearly marked and secured to avoid unauthorized access and tampering.
6011.9 Interstitial monitoring shall be used to check for evidence of a release at least once every thirty (30) days on secondary containment systems on underground tanks and piping installed or replaced after February 8, 2007.