W. Va. Code R. § 47-60-11

Current through Register Vol. XLI, No. 50, December 13, 2024

Section 47-60-11 - Sealing Requirements

11.1. All materials and procedures used in the installation of seals for permanent monitoring wells shall meet the requirements of this section.

11.2. Installation of the Filter Pack Seal. -- A bentonite chip, pellet or a slurry seal shall be placed in the annulus between the borehole and the riser pipe on top of the secondary or primary filter pack. This seal will retard the movement of cement-based grout backfill into the primary or secondary filter packs. To be effective, the filter pack seal should extend above the filter packs approximately three (3) feet or more, but may be less depending on site-specific conditions, where discrete sampling is desired or where physical conditions prohibit a longer seal depending on local conditions. The filter pack seal should be installed using a tremie pipe lowered to the top of the filter pack and slowly raised as the bentonite pellets or the slurry fill the annular space. Bentonite pellets may bridge and block the tremie pipe in deep wells. In these cases, pellets may be allowed to free fall into the borehole. As a bentonite pellet seal is poured into the tremie pipe or allowed to free fall into the borehole, a tamper or weighted line may be necessary to tamp pellets into place. If the seal is installed above the water level, water from an uncontaminated source shall be added to allow proper hydration of the annular seal. The tremie pipe or a weighted line inserted through the tremie pipe shall be used to measure the top of the filter pack seal as the work progresses. Sufficient time should be allowed for the bentonite pellet seal to hydrate or the slurry annular seal to expand prior to grouting the remaining annulus. The volume and elevation of the filter pack seal material should be measured and recorded on the well construction diagram.

11.3. Annular Space Seal Specifications. -- All permanent monitoring wells shall be installed with an annular space seal designed to achieve a permeability of 10^-5 centimeters per second or less. For permanent monitoring wells constructed with filter packs, the annular space seal shall extend from the filter pack seal to the ground surface seal and should be at least two (2) feet in length. For monitoring wells constructed into bedrock formations and without well screens, the annular space seal shall extend from the bottom of the outer casing to the ground surface seal.

11.4. Annular Space Seal Installation. -- Bentonite chips, pellets or granules with a diameter of three-eighths inches (3/8") or less shall either be poured freely down the borehole or added through a tremie pipe to seal the annular space. When a tremie pipe is used to place the annular space sealant, the procedures in subsections 9.2.a and 9.2.b of this rule shall be followed.

11.4.a. When grouts or slurries are used to seal the annular space, the material shall be poured freely down a tremie pipe or pumped down a borehole with the use of a tremie pipe. When a tremie pipe is used to place the annular space sealant, the procedures of subsection 9.2 of this rule shall be followed.

11.4.b. When any slurry or grout is used, there shall be a twelve (12) hour period between the time the annular space seal is installed and the time the protective ground surface seal is installed. Any settling in the annular space seal shall be topped off before the ground surface seal is installed.

11.4.c. The top of the well casing shall be covered with a protective cap.

11.5. Excavated Wells. -- For excavated wells, the seal between the protective cover and the riser pipe acts as both the filter pack seal and the annular space seal.

11.6. Ground Surface Seal and Protective Cover Pipe.

11.6.a. Ground surface seal. -- All permanent monitoring wells shall be constructed with a bentonite cement grout, neat cement grout, or concrete ground surface seal. The ground surface seal shall extend to a minimum of thirty (30) inches below the land surface, and the top shall be sloped away from the well casing. If the monitoring well depth is such that both a minimum two (2) foot annular space seal and a minimum two and one-half (2.5) foot ground surface seal cannot both be placed, the ground surface seal may be shortened.

11.6.b. Protective cover pipe. -- The protective cover pipe shall consist of a casing at least two (2) inches larger in diameter than the well riser and have a locking cap. The protective cover pipe shall extend from the bottom of the ground surface seal to a minimum of twenty-four (24) inches above the ground surface, except as provided in subsection 11.5 of this rule. The protective cover pipe shall always extend above the top of the well riser. For water table observation wells constructed in areas where the depth to the water table is less than seven (7) feet, the required length (depth) of protective cover shall be reduced and may not extend into the filter pack.

11.7. Ground Surface Seal and Flush Mounted Protective Cover.

11.7.a. Ground surface seal. -- All permanent monitoring wells with a flush mounted protective cover shall be constructed with a concrete ground surface seal. The ground surface seal shall extend to, but not beyond, the total depth of the flush mounted protective cover. The ground surface seal shall be installed around the flush mounted protective cover and may not be placed between the flush mounted protective cover and the well casing.

11.7.b. Flush mounted protective cover. -- The flush mounted protective cover shall not be installed in areas subject to ponding or flooding. The flush mounted protective cover lid(s) shall indicate on its outer surface that it is a type of monitoring well as defined in section 3.35 of this rule. A black equilateral triangle inset in a white background is also an acceptable label. If an impervious surface does not exist, an apron shall be created that will support the weight of the traffic in the area. The flush mounted protective cover shall consist of a watertight metal casing with an inside diameter at least two (2) inches greater than the inside diameter of the monitoring well riser. The flush mounted protective cover shall be one continuous metal piece or two metal pieces that are joined with a continuous weld. The flush mount protective cover shall be a minimum of twelve (12) inches in length. There may be no more than eight (8) inches between the top of the monitoring well riser and the top of the flush mounted protective cover after installation. The flush mounted protective cover shall have an exterior flange or lugs. The flush mounted protective cover or the monitoring well shall have a locking mechanism. The monitoring well installed within any flush mounted protective cover shall have a watertight cap.

Note: After removing the watertight cap and prior to taking a head level measurement, a waiting period is recommended to enable the water level to stabilize.

W. Va. Code R. § 47-60-11