R655-4-15. Monitor Well Construction Standards

  15.1 Scope.

  15.1.1 Certain construction standards that apply to water wells also apply to monitor wells. Therefore, these monitoring well standards refer frequently to the water well standard sections of the rules. Standards that apply only to monitor wells, or that require emphasis, are discussed in this section. Figure 7 illustrates a schematic of an acceptable monitor well with an above-ground surface completion. Figure 8 illustrates a schematic of an acceptable monitor well with a flush-mount surface completion. Figures 7 and 8 can be viewed in the publication, State of Utah Administrative Rules for Water Wells, most recent edition, available at the Division of Water Rights, 1594 West North Temple, Salt Lake City, Utah.

  15.1.2 These standards are not intended as a complete manual for monitoring well construction, alteration, maintenance, and abandonment. These standards serve only as minimum statewide guidelines towards ensuring that monitor wells do not constitute a significant pathway for the movement of poor quality water, pollutants, or contaminants. These standards provide no assurance that a monitor well will perform a desired function. Ultimate responsibility for the design and performance of a monitoring well rests with the well owner and/or the owner's contractor, and/or technical representative(s). Most monitor well projects are the result of compliance with the Environmental Protection Agency (EPA), Federal Regulations such as the Resource Conservation and Recovery Act (RCRA), Comprehensive Environmental Response, Compensation and Liability Act (CERCLA or "Superfund"), or specific State Solid and Hazardous Waste requirements. The contracts governing their installation are tightly written containing specific requirements as to site location, materials used, sampling procedures and overall objectives. Therefore specific construction requirements for monitor well installation shall be governed by applicable contracts and regulations providing they meet or exceed state requirements and specifications. Guidelines and recommended practices dealing with the installation of monitor wells may be obtained from the state engineer upon request. Additional recommended information may be obtained from the Environmental Protection Agency (EPA), Resource Conservation and Recovery Act (RCRA), Groundwater Monitoring Enforcement and Compliance Document available from EPA's regional office in Denver, Colorado and from the Handbook of Suggested Practices for the Design and Installation of Groundwater Monitoring Wells, available from the National Groundwater Association in Dublin, Ohio.

  15.2 Installation and Construction.

  15.2.1 Materials and Equipment Contaminant-Free. All material used in the installation of monitor wells shall be contaminant-free when placed in the ground. Drilling equipment shall be clean and contaminant free in accordance with Subsection R655-4-11(11.6.4). During construction contaminated water should not be allowed to enter contaminant-free geologic formations or water bearing zones.

  15.2.2 Borehole Integrity. Some minor cross-contamination may occur during the drilling process, but the integrity of the borehole and individual formations must then be safeguarded from permanent cross connection.

  15.2.3 Casing and Screen. The well casing should be perforated or screened and filter packed with sand or gravel where necessary to provide adequate sample collection at depths where appropriate aquifer flow zones exist. The casing and screen selected shall not affect or interfere with the chemical, physical, radiological, or biological constituents of interest. Screens in the same well shall not be placed across separate water bearing zones in order to minimize interconnection, aquifer commingling, and cross contamination. Screens in a nested well can be placed in separate water bearing zones as long as the intervals between the water bearing zones are appropriately sealed and aquifer cross connection and commingling does not occur. Monitor well casing and screen shall conform to ASTM standards, or consist of at least 304 or 316 stainless steel, PTFE (Teflon), or Schedule 40 PVC casing.

  15.2.4 Gravel/Filter Pack. If installed, the gravel or filter pack should generally extend two (2) feet to ten (10) feet above screened or perforated areas to prevent the migration of the sealing material from entering the zones being sampled. Gravel or filter pack material shall meet the requirements of Subsection R655-4-11(11.5.2). Gravel/filter pack for monitoring wells does not require disinfection. Drill cutting should not be placed into the open borehole annulus. The well driller shall ensure that a bridge or voids do not occur in the annular space during the placement of the gravel pack by means of a sounding device or other mechanism.

  15.2.5 Annular Seal. All monitor wells constructed shall have a continuous surface seal, which seals the annular space between the borehole and the permanent casing, in accordance with the provisions in Section R655-4-11. The surface seal depth requirements of Section R655-4-11 do not apply to monitor wells. The surface seal may be more or less than 50 feet depending on the screen/perforation and/or gravel pack interval. Seals shall also be constructed to prevent interconnection and commingling of separate aquifers penetrated by the well, prevent migration of surface water and contaminations into the well and aquifers, and shall provide casing stability. The seal shall have a minimum diameter of four inches larger than the nominal size of the permanent casing, and shall extend from land surface to the top of the filter pack. After the permanent casing and filter pack (optional) has been set in final position, a layer of bentonite or fine sand (e.g., mortar sand) shall be placed on top of the filter pack to maintain separation between the seal material and the screened interval in order to insure that the seal placement will not interfere with the filter pack. The remaining annular space shall be filled to land surface in a continuous operation with unhydrated bentonite, neat cement grout, sand-cement grout, or bentonite grout. Only potable water should be used to hydrate any grout or slurry mixture. The completed annular space shall fully surround the permanent casing, be evenly distributed, free of voids, and extend from the permanent casing to undisturbed or recompacted soil. All sealing materials and placement methods shall conform to the standards in Section R655-4-2 and Subsection R655-4-11(11.4). The well driller shall ensure that a bridge or voids do not occur in the annular space during the placement of the seal.

  15.2.6 Cuttings, Decon Water, Development Water, and Other IDW. Drill cuttings, decontamination (Decon) water, monitor well development water, and other investigation derived waste (IDW) shall be managed and disposed of in accordance with applicable state and federal environmental regulations. It is the responsibility of the driller to know and understand such requirements.

  15.3 Minimum Surface Protection Requirements.

  15.3.1 If a well is cased with metal and completed above ground surface, a locking water resistant cap shall be installed on the top of the well.

  15.3.2 If the well is not cased with metal and completed above ground surface, a protective metal casing shall be installed over and around the well. The protective casing shall be cemented at least two feet into the ground around the nonmetallic casing. A water tight cap shall be installed in the top of the well casing. A locking cap shall be installed on the top of the protective casing.

  15.3.3 Monitor wells completed above ground and potentially accessible to vehicular damage shall be protected in the following manner. At least three metal posts, at least three inches in diameter, shall be cemented in place around the casing. Each post shall extend at least three feet above and two feet below ground surface. A concrete pad may be installed to add protection to the surface completion. If installed, the concrete pad shall be at least four (4) inches thick and shall slope to drain away from the well casing. The base shall extend at least two (2) feet laterally in all directions from the outside of the well boring. When a concrete pad is used, the well seal may be part of the concrete pad.

  15.3.4 If the well is completed below land surface, a water tight cap with a lock shall be attached to the top of the well casing. A metal monument or equivalent shall be installed over and around the well. The monument shall serve as a protective cover and be installed level with the land surface and be equipped with a waterproof seal to prevent inflow of any water or contaminants. Drains will be provided, when feasible, to keep water out of the well and below the well cap. The monument and cover must be designed to withstand the maximum expected load.

  15.4 Abandonment.

  15.4.1 Abandonment of monitor wells shall be completed in compliance with the provisions of Section R655-4-14. The provisions of Section R655-4-14 are not required for the permanent abandonment of monitor wells completed at a depth of 30 feet below natural ground surface.