West Virginia Code of State Rules › Agency 47 - Water Resources, Division Of Water And Waste Management › Title 47 - LEGISLATIVE RULE DEPARTMENT OF ENVIRONMENTAL PROTECTION DIVISION OF WATER RESOURCES › Series 47-60 - Monitoring Well Design Standards › Section 47-60-11 - Sealing Requirements

Current through Register Vol. XLI, No. 28, July 12, 2024
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.