6009.1 A release detection method that monitors or tests for vapors within the soil gas of the excavation zone shall meet the requirements of this section.

6009.2 The owner or operator shall assess the excavation zone to ensure compliance with the requirements set forth in this section.

6009.3 The materials used as backfill (such as gravel, sand, crushed rock, or similar materials) shall be sufficiently porous to readily allow diffusion of vapors from releases into the excavation zone.

6009.4 The stored regulated substance, or a tracer compound placed in the tank system, shall have a volatility that is sufficient to result in a vapor level that is detectable by the monitoring devices located in the excavation zone in the event of a release from the tank.

6009.5 The measurement of vapors by the monitoring device 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.

6009.6 The level of background contamination in the excavation zone shall not interfere with the vapor monitoring method used to detect releases from the tank.

6009.7 The vapor monitor used shall be designed and operated to detect any significant increase in concentration above the background concentrations in the excavation zone of any one (1) of the following:

(a) The regulated substance stored in the tank system;

(b) A component or components of the regulated substance; or

(c) A tracer compound placed in the tank system.

6009.8 Before using vapor monitoring, the owner or operator shall assess the excavation zone to ensure compliance with §§ 6009.3 through 6009.6 of this section, and to establish the number and positioning of monitoring wells that will detect releases within the excavation zone from any portion of the tank that routinely contains product.

6009.9 Monitoring wells shall be clearly marked and secured to avoid unauthorized access and tampering. Monitoring wells shall not be marked in any way that could be associated with a regulated substance stored at the facility.

SOURCE Final Rulemaking published at 40 DCR 7835, 7873 (November 12, 1993); as amended by Final Rulemaking published at 46 DCR 7699 (October 1, 1999).