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 47-60-10 - Filter Packs

Current through Register Vol. XLI, No. 28, July 12, 2024
10.1. All
				permanent monitoring wells installed in unconsolidated material and used for
				the collection of water quality samples shall be constructed with filter packs,
				except as provided in subsection 10.4 of this rule. Permanent monitoring wells
				installed in bedrock may be constructed with filter packs. When used, the
				filter pack shall be the only material in contact with the well screen. All
				commercially prepared filter packs installed in permanent monitoring wells
				shall meet the requirements in subsection 10.2 of this rule. All other filter
				packs shall meet the requirements in subsection 10.4 of this rule.
10.2. Specifications. -- The filter pack
				shall be a silica based sand or gravel. The sand or gravel used for filter
				packs shall be hard and durable and shall have an average specific gravity of
				not less than 2.50. The sand and gravel shall be visibly free of clay, dust and
				micaceous and organic matter. Not more than five percent (5%) of the sand or
				gravel shall be soluble in a ten percent (10%) hydrochloric acid solution.
				Uniformity coefficients for filter pack material shall range from one (1) to
				three (3). All filter pack material should be purchased from a reputable
				supplier who has properly cleaned and bagged the material. In lieu of a sieve
				analysis, for unconsolidated material that is predominately silt and clay, the
				filter pack shall be a fine sand. In bedrock, the filter pack shall be a medium
				or coarse sand or gravel, except in karst or highly fractured bedrock
				formations where fine sand filter packs may be used. Crushed limestone,
				dolomite or any material containing clay or any other material that will
				adversely impact on the performance of the monitoring well may not be used as
				filter pack.
Note: When installing a monitoring well in karst or highly
				  fractured bedrock, a pre-packed or double sleeved screen may be necessary to
				  hold the filter pack material in place.
10.3. Installation. -- The filter pack shall
				generally extend from six (6) inches beneath the bottom of the well to between
				two (2) and five (5) feet above the top of the well screen. For water table
				observation wells constructed in areas where the depth to water table is less
				than seven (7) feet or where discrete monitoring is desired, the required
				filter pack height above the top of the well screen may be reduced to six (6)
				inches to allow for the required amount of annular space sealant to be placed.
				To ensure that the filter pack is installed evenly surrounding the well screen
				and casing over the proper depth interval, a tape measure, measuring rod or
				similar device shall be used to measure the height of the filter pack. The tape
				measure, measuring rod or similar device shall be carefully raised and lowered
				while the filter pack is being installed to identify bridging. If bridging
				occurs, the filter pack material shall be tamped into place surrounding the
				well screen and riser, using a measuring rod or similar device. Pre-packed
				screens may be used if necessary.
10.4. Collapsed Formation. -- Collapsed
				formation may be used as filter pack material, if the collapsed formation will
				limit the passage of formation fines into the well screen and either an
				artificial filter pack cannot be installed or the formation grain size is
				greater than or equal to fine sand sized grains. The grain size distribution of
				the collapsed formation shall be such that at least ninety percent (90%) of the
				formation will be retained by the well screen.