Mississippi Administrative Code › Title 11 - Mississippi Department of Environmental Quality › Part 5 - Underground Storage Tank Regulations › Chapter 2 - Mississippi Commission on Environmental Quality Underground Storage Tanks Regulations Technical Standards and Corrective Action Requirements for Owners and Operators of Underground Storage Tanks (UST) (Adopted March 22, 1989; Amended August 25, 2011, Last Amended August 23, 2018) › Appendix 11-5-2-280.4 - GUIDELINES FOR THE PERMANENT CLOSURE OF PETROLEUM UNDERGROUND STORAGE TANK SYSTEMS › Section 11-5-2-280.4-5 - SAMPLING LOCATIONS FOR DISPENSER ISLANDS & PIPING › Section 11-5-2-280.4-5.3 - Piping Trenches › Section 11-5-2-280.4-5.3.3 - Closure in Place of Piping

Current through June 25, 2024
Since potentially contaminated soils cannot be seen
						  during closure in place activities as when excavating, the sampling
						  requirements for closure in place are more conservative. All sampling schemes
						  must follow the exact guidelines given in this document unless special
						  circumstances do not allow such. Any alternative sampling plan must be
						  submitted to the UST Branch for approval.
When piping is to be closed in place, sampling along
						  the piping trench is not required if the location of the dispenser island
						  sample is within 25 feet of the nearest tank excavation sample. The 25 foot
						  distance is measured in a straight line as depicted in Figure 12.
If you are conducting a piping closure in place but the
						  tanks are remaining active, the 25 foot distance referenced above has no
						  significance. Under these circumstances, a sample must be collected from the
						  dispenser island and from the end of the piping trench where it enters the tank
						  bed. If there is more than 25 feet of piping trench located between these two
						  sampling points, additional samples must be collected such than no more than 25
						  feet exists between any two sample points.
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If the distance between the dispenser island sample and
						  the nearest tank bed sample is greater than 25 feet, soil samples must be
						  collected along the piping trench such that no more than 25 feet of piping
						  exists between any two sampling points as shown in Figure 13. This means that
						  some excavation is required in order to locate the piping trench since sampling
						  must occur underneath or immediately adjacent to the trench. All soil borings
						  must extend to a depth of at least one foot below the bottom of the piping
						  trench and into the native soil. Samples must be collected from each boring
						  following the field screening practices as described in Section 4.4.4.
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If "true" groundwater (refer to Section 3.2) is
						  encountered during soil boring activities, groundwater samples must be
						  collected from each boring that contains groundwater and each sample must be
						  analyzed separately. Soil sampling must be conducted from those borings that do
						  not have groundwater. In addition, regardless of whatever soil and/or
						  groundwater sampling that is conducted, one soil sample must be collected from
						  the boring that exhibited the highest level of petroleum contamination during
						  the field screening process.