W. Va. Code R. § 47-60-10

Current through Register Vol. XLI, No. 45, November 8, 2024

Section 47-60-10 - Filter Packs

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.

W. Va. Code R. § 47-60-10