Laserfiche WebLink
ABC,INC. ID~303-698-9241 FEB 19'98 14:51 No .007 P.07 <br />Work Ptan for Alluvial Groundwater Characterization, Big Elk Mine AdrienBrown <br />4.3 Install Monitoring Welle <br />Monitoring wells will be installed at 201ocations within the study area, at the locations shown on Plate <br />1. The program will involve a combination of 2-inch and 3/4-inch internal diameter (ID) monitoring <br />wells. A total of 24 wells will be installed at the 20 locations; <br />8 3/4-inch monitoring wells <br />8 2-inch monitoring wells <br />4 paired 2-inch and 3/4-inch monitoring wells <br />]each of the major drainages hoc been targeted for baseline alluvial groundwater cheracteri~ation. live <br />of the proposed locations are tributary to the Williams Fork, to the south. The remainder are tributary to <br />the Yampa River to the north. Ten of the monitoring wells will be located near existing surface water <br />monitoring stations. Project-related surface facilities such as the load-out area will be equipped with <br />upgradient and downgradient monitoring wells. Minor modifications of the exact well locations may be <br />made in the field, based on access and hydrologic understanding on site, <br />The paired wells will be individual completions, located approximately ] 5-25 feet apart. 1'he paired <br />wells will 6c installed for the purpose of 1) determining water quality cotnparability between the 2-inch <br />and 3/4-inch completions, and 2) having a nearby observation well for hydraulic property (storage) <br />determination from pump testing. <br />Wells will he installed acing alight-weight (12,000 lb., six-wheel) Hurricane drill rig. The drilling and <br />installation of the 2-inch and 3/4-inch wells ate described briefly below, anal ere outlined in detail in the <br />Standard Operating Procedures (attached). <br />Drilling end Completing 2-inch Wells <br />Tho 2-inch wells will be drilled using 8-inch Oll hallow stem auger. At the discretion ai' the on-site <br />hydrogeologist, samples may be collected continuously, or intermittently (nut to exceed ten feet without <br />collecting a sample). The samples will be logged according to standard geologic nomenclature, <br />Satrrples will not be retained. <br />'1'Ite wells will be completed using 2-inch ID, !lush-threaded, 10-slot, PVC screen and blank casing, <br />Wells will he screened below the water table, with 20 feet of screened section in the bottom of the <br />borehole and blank casing to the surface. A filter pack of 20-30 Colorado silica sand will installed <br />through the inner tube of the augers, end the augers will be pulled back to expose the screen. In this <br />manner, the filter pack will he placed around the well screen, to a height of 2-3 feet above the top of the <br />screen. Enviroplug (or comp¢rable brand) bentonite chips will be placed in the annular space, from the <br />top of the sand to approximalcly fow feet below ground surface. <br />The surface conrpleliott will consist of a 6-inch diarrtctcr steel surface casing, with locking aluminum <br />cap. 'this casing will be set 2.5-3 feet into a concrete monument, and will extend 2-2.5 feet above <br />growrd surface. The surface casing will be painted, end the well ]l~ will be painted or stomped on the <br />casing or will be carved into the concrete monument. <br />Prols~t 1409C.99O208 q <br />