2013-08-13_HYDROLOGY - M1977348 (2)

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August 2013 11 103- 81640A Due to the initial volume of water in monitoring well MW -7 (about 140 gallons), MW -7 was developed by air lift pumping on January 22, 2013 when about 100 gallons were removed before "lift' was lost. Following this, Golder instructed Drilling Engineers to surge and bail the well to complete development. About 10 gallons were removed by bailing. On March 5, 2013, six hours of additional development was conducted by surging monitoring well MW -7 with a 3'/8 -inch diameter surge block and bailing until the well went dry after about 41 gallons were removed. Field parameters were measured during development (Appendix D). As with monitoring well MW -6, low recharge impeded the flushing of the well screen that is necessary to considerably reduce turbidity. 3.5 Well Hydraulic Testing After development, rising and falling head (slug) testing was conducted in monitoring well MW -5 by monitoring the water level changes created by rapidly submerging and removing a solid cylinder (slug) into and out of the water column of the well. Slug testing was not performed in monitoring well MW -7 because hydraulic conductivity estimates were obtained from borehole packer injection tests (Section 3.2) and in monitoring well MW -6 due to the long recovery times observed during development. In monitoring well MW -5, a 5 -foot long, 1.25 -inch ID PVC slug was used to displace water in the well, which was monitored with an In -Situ Troll 300 electronic pressure transducer and data logger. However, the initial displacement was insufficient considering a minimum of about 6 inches is required for high conductivity formations (Butler 1998) and recovery to static conditions occurred too rapidly (within one second) to record during several attempts to perform the slug test. Consequently, analyses of these tests could not be performed to estimate hydraulic conductivity. Previous hydraulic testing of monitoring wells MW -1 through MW -4 have yielded hydraulic conductivities in the range of 10 -7 to 10 -10 centimeters per second (cm /sec) (Table 2). Based on the outcome of the hydraulic testing in monitoring well MW -5, it is likely that the hydraulic conductivity there is significantly greater than at monitoring wells MW -1 through MW-4 and is the reason the slug testing was unsuccessful. 3.6 Surveying Surveying of the seven monitoring wells was performed on January 10, 2013 to establish groundwater elevations for monitoring flow directions and determining hydraulic gradients. Surveying activities was performed by KRW Consulting, Inc., a Colorado licensed surveyor, and was tied into the same coordinate system used for other surveying at the Site. At each well location, the elevations of the surface of the concrete pad and top of PVC well casing were surveyed to an accuracy of 1/100 foot. The results of the survey of each monitoring well location, and the elevations of each PVC well head casing top and concrete pad are provided in Table 1 and in each monitoring well construction diagram in Appendix D. 920Golder i \10 \81640a\ 0400\ gwcharwelhnstallfieldrep_ 09aug13\ gwchanvelhnstallheldrep_09aug13 docx Associates