SECTION 165:25-3-6.24. Testing or monitoring for liquids on the groundwater

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

(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)   That the backfill is sufficiently porous to allow migration of product from a release to the observation wells (i.e., sand, pea gravel or crushed rock).

(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. Groundwater monitoring may not be effective if the site has had prior spills or releases.

(4)   The location and historical levels of groundwater at the site. Groundwater monitoring cannot be used if the water table is less than three feet (3') below ground surface or more than twenty feet (20') below ground surface.

(5)   Fluctuation of groundwater. The well screen must intercept the water table at both high and low elevations. Free product floating on top of the water surface cannot enter a well if the water level is higher than the well screen, nor can free product enter a well if the water level is below the bottom of the well screen. It must be determined that groundwater conditions are such that a release would not go undetected.

(6)   The stored product's compatibility with the monitoring device that will be used. The detection device must be able to detect the presence of at least one-eighth of an inch (1/8") of free product on top of the groundwater in the monitoring wells. Groundwater monitoring is only effective if the stored product is lighter than water (i.e., has a specific gravity less than 1.0), which allows the product to float on the water surface. The stored product must not be soluble in water. Products that are highly soluble in water would not be detected as a separate liquid phase.

(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.

(c)   The groundwater observation wells must be installed in the tank excavation. Two (2) wells are sufficient for single tanks of 3,000 gallons or less capacity or for not more than two (2) 2,000 gallon tanks in one excavation. For multiple tanks, a minimum of three (3) wells must be installed with at least one of the wells placed on the downgradient side. A sufficient number of wells must be installed so that a release from any given tank within the tank excavation can be detected. Wells must be spaced such that any given well is capable of detecting a release from within at least at twenty foot (20') radius of that monitoring point and no greater. Under normal circumstances, groundwater monitoring on piping runs would not be appropriate due to the depth to groundwater and the associated time required to detect a leak.

(d)   Observation wells must be installed in accordance with OAC 785:35, Oklahoma Water Resources Board (OWRB) rules. OWRB rules allow a PSTD licensed UST Installer to install observation wells during tank installations only. An OWRBlicensed driller must perform all other well installations.

(e)   Groundwater observation wells must meet these minimum requirements:

(1)   Be constructed from two inch (2") or four inch (4") polyvinyl chloride (PVC) or stainless steel casing with factory milled well screen.

(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)   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 unless the tank and/or piping is backfilled with pea gravel.

(4)   The well screen must begin no less than eighteen inches (18") below ground surface. 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 monitoring well manhole. The remainder of the well above the well screen must be sealed with a cement-bentonite mixture or bentonite pellets.

(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)   The well(s) must be installed within manholes competent to withstand the 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 may also be identified with an equilateral triangle to identify the well as an observation well or site assessment observation well.

(f)   Records demonstrating compliance with this Section must be submitted to PSTD before a new groundwater monitoring system may be used or before an existing groundwater 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 monitoring wells, copies of the OWRB Multi-Purpose Completion Report for each well, name of the company and individual performing the assessment.

(1)   Any indication of free product floating on the water table must be reported to PSTD by telephone at [phone] within twenty-four (24) hours of the owner/operator or any of their employees or agents discovering the product.

(2)   If a monitoring report under the circumstances of above is not made within twenty-four (24) hours, the owner or operator, their employees or agents, may be subject to an enforcement action.

(g)   All groundwater observation wells must be checked at least every thirty (30) days by a PSTD Licensed Groundwater Monitor Well Technician and a copy of the results must be maintained at the facility and readily available to the PSTD Fuel Specialist.

[Source: Amended and renumbered from 165:25-3-5.4 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]