2013-08-13_HYDROLOGY - M1977348 (2)

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w August 2013 No 103- 81640A 3.1.1 Monitoring Well MW -5 Borehole The borehole to install monitoring well MW -5 was drilled using 3'/4 -inch inside diameter (ID) HSA to the termination depth of 60 feet below land surface (bls). Continuous 2 -foot long split -spoon sampling was conducted within the string of HSA from land surface to final spoon refusal at 58.2 feet bls. Representative samples from each two -foot interval were collected and placed in one - gallon capacity plastic zipper locked bags for storage. Spoon refusal was first encountered at 56 feet bls. Auger refusal was not encountered before reaching the termination depth of 60 feet bls. Groundwater was encountered at 39.45 feet bls as observed in a split -spoon sample collected from 38 to 40 feet bls. The boring was terminated 20 feet below first encountered groundwater level. Consequently, rock coring was not conducted at monitoring well MW -5. An estimated 10 gallons per minute of groundwater discharge was observed during the subsequent air lift pumping conducted to clear drill cuttings from the borehole prior to setting the well. 3.1.2 Monitoring Well MW -6 Borehole The borehole to install monitoring well MW -6 was drilled using a 7% -inch air -rotary roller bit through a string of 8'/4 -inch ID HSA set at 19.5 feet bis to case off the fill. A diverter was installed at the head of the HSA to divert cuttings and dust generated from the drilling to a covered roll -off. Water was added to the air stream to help lift drill cuttings and to control dust. Little groundwater was observed to be produced from the borehole during drilling. Most of the added water was observed to return to the surface. The encountered lithology at monitoring well MW -6 was interpreted from drill cuttings collected at 5 -foot intervals. To obtain representative samples at specific depths, the samples were collected when drilling resumed after the borehole was cleared of most cuttings between runs and placed in 1- gallon plastic bags. Obvious sandstone drill cuttings were first observed at a depth of about 230 feet bls. The borehole was terminated at a depth of 231.1 feet bls. 3.1.3 Monitoring Well MW -7 Borehole The NQ corehole at monitoring well MW -7 was drilled within a string of 3'/4 -inch ID HSA drilled through the fill to the top of bedrock. A 5 -foot long, 2 -inch diameter sampler was used to collect continuous samples through the HSA to a depth of 33.8 feet bls, where refusal was encountered. From this depth to the termination depth at 271 feet bls, NQ rock coring was conducted through the 3'/4 -inch ID HSAs to obtain a continuous core sample of the bedrock to the top of the Codell sandstone. The core was immediately boxed, described, photographed and inventoried upon retrieval from the 10 -foot long wireline standard core barrel. From a depth of 33.8 feet bls to 61.3 feet bls, the coring was conducted using air to more easily observe the first occurrence of groundwater. Groundwater was encountered at a depth of 57.83 feet bls, and was observed to rise to a depth of 55.65 feet over 30 minutes after first encountering this water - bearing zone. Following the first encounter of groundwater, the remainder of the boring was i \10 \81640a\ 0400\ gwcharwellinstallfieldrep_ 09aug13\ gwcharwellinstallfieldrep _09aug13 docx Golder Associates