1. (a) Before installing a new vapor monitoring system or continuing to use an existing vapor monitoring system for thirty (30) day release detection a site-specific site assessment must be conducted to determine the following:

   1. (1) The exact location and total depth of the tank(s) and piping to avoid damage to the UST system during well installation and to determine the number and placement of wells.
   2. (2) That the backfill is sufficiently porous to allow diffusion of vapors from a release to migrate readily to the observation wells (i.e., sand, pea gravel or crushed rock).
   3. (3) That background levels of contamination or naturally occurring organic hydrocarbons are low enough to allow a release from the tank(s) or piping to be detected. To determine background concentrations, a temporary vapor well can be installed in the UST excavation area and the device that will be used for monitoring can be used to get an initial reading.
   4. (4) The location and historical levels of groundwater at the site. If the backfill is saturated with water, because of a perched water table, fluctuating water table, rainfall, etc. above the tank burial depth, a vapor monitoring system should not be used because dispersion of vapors would be restricted and a release could go undetected. Approval for the use of vapor monitor wells for thirty (30) day release detection at a location where there has previously been a confirmed release will be at PSTD's discretion.
   5. (5) Volatility of the stored product and its compatibility with the monitoring device that will be used.
2. (b) Individuals performing this site assessment must be a PSTD Licensed Environmental Consultant and a copy of the site assessment must be maintained at the facility.
3. (c) The vapor observation wells must be installed within the tank excavation. A minimum of two (2) wells are required for multi-tank excavations, with at least one (1) of the wells on the downgradient side. Wells must be spaced such that any given well is capable of detecting a release from within at least a twenty foot (20') radius of that monitoring point and no greater. One (1) well is acceptable for single tanks of 3,000 gallons or less capacity, or for not more than two (2) 2,000 gallon tanks in one excavation, provided the well is near the center of the excavation.
4. (d) Observation wells must be installed in accordance with OAC 785:35, Oklahoma Water Resources Board (OWRB) rules. OWRB rules allow a PSTDlicensed UST Installer to install observation wells during tank installations only. An OWRBlicensed driller must perform all other well installations.

5. (e) In addition to (a) through (d) above, vapor observation wells must meet these minimum requirements:

   1. (1) Be constructed from two inch (2") or four inch (4") polyvinyl chloride (PVC) or stainless steel casing with factory milled well screen.
   2. (2) The well screen section should begin approximately two feet (2') below ground surface (bgs) for tank excavations. The well screen must extend to a depth of two feet (2') below the tank bottom.
   3. (3) A filter pack of graded gravel or uncontaminated quartz sand, silica, or other material that will not affect the groundwater quality must be placed around the entire length of the well screen.
   4. (4) The area above the well screen must be sealed (annular seal) to prevent surface spills from contaminating the well, which would result in a false indication of a release. An anti-shrink concrete or grout seal must extend at least twelve inches (12") from within the observation well manhole. The remainder of the well above the well screen must be sealed with a cement-bentonite mixture or bentonite pellets.
   5. (5) A concrete or cement surface pad must be installed around the casing at the surface with minimum dimensions of three feet (3') in diameter by three and a half inches (3.5") thick. The surface pad must be sloped so to ensure that all surface water flows away from the well. The surface pad is not required if the well is completed in competent concrete or asphalt paving.
   6. (6) The well(s) must be installed within manholes competent to withstand anticipated traffic flow. The well casing must be secured with a tight fitting cap and the manhole cover bolted to prevent unauthorized tampering. The manhole cover must be clearly marked with appropriate identification such as "test well" or "monitoring well" and/or may also be identified with an equilateral triangle to identify the well as an observation well or site assessment observation well.
6. (f) Records demonstrating compliance with this Section must be submitted to PSTD before a new vapor monitoring system may be used or before an existing vapor monitoring system may continue to be used after July 15, 2005. At a minimum, these records must include a site map that includes the location of tanks, piping, dispensers and all observation wells, copies of the OWRB Multi-Purpose Completion Report for each well, name of the company and individual performing the assessment.
7. (g) All vapor observation wells must be checked at least every thirty (30) days by a PSTD Licensed Vapor Monitor Well Technician and a copy of the results must be maintained at the facility and readily available to the PSTD Fuel Specialist.
8. (h) The vapor monitoring equipment must be designed and operated to allow the threshold level to be preset specifically for the type of regulated substance stored in the tank system and be capable of detecting any significant increase in the concentration of regulated substance, component or components of that substance (in a range of 0 to 10,000 units/ppm) or a tracer placed in the tank system above background levels.
9. (i) Observation well readings above 4,000 units/ppm for gasoline and above 1,500 units/ppm for diesel, or above 1,500 units/ppm for a tank pit containing both gasoline and diesel tanks, must be reported to PSTD by telephone at (405) 521-4683 or toll free at 1-888-621-5878 within twenty-four (24) hours of the owner, operator, any of their employees, or agents knowing the reading.
10. (j) An increase in vapor levels of 500 units/ppm above background or historical levels detected by thirty (30) day monitoring, even though below twenty-four (24) hour reporting level, must be reported if the increase does not correct itself in the second month of monitoring. The report must be made within twenty-four (24) hours of the owner or operator, their employees or agents knowing the second month's monitoring results.
11. (k) If a monitoring report under the circumstances above is not made within twenty-four (24) hours, the owner or operator, their employees or agents, may be subject to formal enforcement action.

Amended and renumbered from 165:25-3-5.3 at 23 Ok Reg 2261, eff 7-1-06

Amended at 25 Ok Reg 1867, eff 7-1-08

Amended at 34 Ok Reg 935, eff 9-11-17

Amended at 35 Ok Reg 985, eff 10-1-18

Amended at 36 Ok Reg 551, eff 8-1-19