2010-02-15_HYDROLOGY - M2007044 - Laserfiche WebLink

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Page 2 November 12,2008 are 12S 0670075mE,4278968mN,+6 in;elevation of 7,065 ft above mean sea level. The final surveyed coordinates for the completed well as provided by EFR are N1314621.40,E1987519.84; ground elevation 7042.53 ft AMSL. The elevation of the top of the PVC well casing is 7045.20 ft AMSL(Bruce Norquist,EFR,personal communication). These coordinates are based on NAD27 and NAVD29. Drilling was conducted using air and air-mist rotary methods with a 5 5/8-inch bit from 3 ft to 120 ft below ground surface(bgs)and an 8 5/8-inch bit for the surface casing from 0 to 3 ft bgs. Air rotary drilling of MW-W 1 was used to a depth of 110 ft. Air-mist was used from 102 to 120 ft. Surface casing consisted of 6 5/8-inch OD'/4-inch steel from 3.0 ft(bgs)to+3.0 ft above ground surface. Well casing consisted of Johnson 2-inch ID(2 3/8-inch OD)schedule 40 flush joint PVC with 0.020-inch slot size. Figure 1 shows the well construction diagram for MW-W 1. The well was constructed as shown in the table below. MW-W1 Well Construction Summary Depth Depth ft bgs) Well Casing ft bgs) Annulus Materials +2.7-60.3 Johnson 2-inch ID(2 3/8-inch +1.5- 1.0 No.8-12 Colorado Silica Sand OD)schedule 40 flush joint PVC +1.0-40.5 Bentonite grout 60.3-110.3 2-inch ID(2 3/8-inch OD) 40.5-�44.0 Bentonite pellet seal(hydrated) schedule 40 flush joint PVC with -44.0-59.3 Potential void or borehole slough 0.020-inch slot 110.3-115.3 2-inch ID(2 3/8-inch OD) -59.3-115.3 No. 8-12 Colorado Silica Sand schedule 40 flush joint PVC sump with end cap 115.3-120 115.3-120 Washed'/4-inch gravel Gordon Smith reported damp conditions(cuttings)at approximately 30 ft and 78 ft. No water was produced at the surface while penetrating these damp strata. At a depth of 80 ft,the hole was allowed to set for 5 minutes followed by air injection which produced between 10 to 50 gallons of water on the surface. This process was repeated with the same result. Drilling proceeded to a depth of 102 ft and the hole was allowed to set again followed by air injection. A similar volume of water was produced at the surface. WWL concluded that the borehole yielded a sufficient quantity of water to serve as a suitable monitoring well. EFR(Frank Filas)was contacted and informed of the recommendation to complete the well in this interval,and EFR concurred. The well was drilled to a total depth of 120 ft to increase the overall screen length for the well. Water was injected beginning at the 102 ft depth to facilitate cutting removal and conditioning of the borehole. Well completion work was conducted on October I&and I I th. Installation of the well casing proceeded without problems. As shown in the table above,Johnson 2-inch Schedule 40 well casing with 0.020-inch slot was used. The screen interval was 50 ft in length,from 110.3 ft to 60.3 ft bgs. Five stainless steel centralizers were used and installed on the casing at locations of 10,30,50,70,and 90 feet(ft)from the bottom of the casing. A 5-ft sump with an end cap was installed,followed by 50 ft of screen and 63.2 ft of solid casing to the surface. A total of 118.2 ft of casing was initially installed and later shortened to approximately 118 ft. Stick-up(PVC casing above ground surface)was 2.7 ft. Sand pack installation was conducted with a 1-inch steel tremie pipe. Initial tremie pipe length was 80 ft and shortened as sand pack was added. Colorado Silica Sane No.8-12 was used for sand pack and was added to the tremie line with fresh water. Washout in the borehole consumed more sand than anticipated and resulted in an insufficient amount of sand to complete the sand pack on October 10'}'. FRas111208.doe