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Amy Eschberger Reference No. 20144265-REV1 <br /> Colorado Division of Reclamation,Mining and Safety September 4,2020 <br /> It is assumed that excess drill cuttings will be non-hazardous and can be disposed at a nearby solid waste landfill. <br /> However, this disposal method may require sampling and chemical analysis of the cuttings prior to disposal. If <br /> necessary, the cuttings may be temporarily stockpiled on Site pending the laboratory analysis. <br /> The Golder hydrogeologist/engineer will prepare a Iithologic log of each borehole as drilling progresses. In addition <br /> to this geologic information, the Golder hydrogeologist/engineer will pay close attention to the depth at which <br /> groundwater is first encountered, if discrete intervals of saturation exist at various depths, and changes in lithology. <br /> 2.3 Well Installation <br /> Consistent with MW-6 and MW-7, wells will be installed directly (approximately 5 feet) above the Niobrara-Codell <br /> contact. Since the contact will be encountered during drilling, the bottom of the borehole may need to be filled with <br /> bentonite. Coated bentonite pellets will be used and will be allowed to hydrate for a minimum of one hour prior to <br /> proceeding with the well installation. <br /> The wells will be constructed with 4-inch diameter,flush threaded, Schedule 80 PVC screen and riser pipe, such that <br /> they can be sampled for water quality. The screen in each well will be perforated with 0.010-inch slots and may be up <br /> to 20 feet in length. Final screen lengths will be determined in the field based on geology and actual groundwater <br /> conditions observed during drilling. PVC casing will be added to the top of the screen as it is lowered in the borehole <br /> until the screen reaches the desired depth and the casing extends 2 to 3 feet above the ground surface. Centralizers <br /> will be installed in the center of the screen and approximately every 50 feet below ground surface. <br /> The annular space around the screen and end cap will be backfilled with clean,washed,well-rounded silica sand (#10- <br /> 20 or equivalent).The sand pack will be tremied from the bottom of the borehole to approximately 2 feet above the top <br /> perforation.Water will not be used to assist in placement of the sand pack unless conditions require the use of water.A <br /> minimum of 2 feet of medium bentonite chips or coated bentonite pellets will be fed into the annular space above the <br /> screen and filter pack to provide a seal. Grout will be placed in the annular space above the bentonite seal to within <br /> approximately 3 feet of the ground surface. The grout will be mixed and placed in accordance with the State of <br /> Colorado Division of Water Resources(DWR)Water Well Construction Rules 2 CCR 402-2. <br /> Once the grout has cured, a protective steel casing will be placed around the PVC riser such that the bottom <br /> extends into the annual space to the top of the grout and the top rises above the PVC casing several inches. The <br /> protective casing will be equipped with a locking cover to prevent unauthorized entry and allow access for water <br /> level measurement. A concrete pad, approximately 3-foot square, sloping away from the well, will be constructed <br /> around the protective casing. <br /> 2.4 Surveying <br /> Surveying will be performed following well construction so that groundwater elevations can be established for <br /> monitoring flow directions and calculating hydraulic gradients. Surveying activities will be performed by a licensed <br /> surveying subcontractor to Golder and will be tied into the same coordinate system used for other surveying at the Site. <br /> 2.5 Well Development <br /> After the grout has set for a minimum of 48 hours and there has been sufficient time for the groundwater to enter the <br /> well, the wells will be developed to improve water flow into the wells and reduce turbidity by removing fines from the <br /> screen and sand pack. Development will be conducted using a combination of surging and bailing/pumping and/or <br /> air lifting methods.Water will not be added to the well during development and the volume of water purged will be <br /> documented. During development, field parameters of pH, specific conductivity, and temperature will be measured <br /> GOLDER 3 <br />