2019-01-23_HYDROLOGY - M2002004 - Laserfiche WebLink

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Mr.Alex Alarcon January 21,2019 Page 2 As described in the above:-referenced CCG report on well completions,MW-6 was completed as a Fort Hayes Limestone well in what was obviously a low water producing zone. The bottom of the well is at the base of the Fort Hayes,approximately 57 feet below ground surface. The drilling rig was then repositioned approximately 25 feet southwest of MW-6 with_the original intention of installing MW-7 in the underlying Codcll Sandstone. The lithology was essentially the same as that encountered in MW-6,until water was encountered in a%vatcr-producing fractured zone at approximately 47 feet below ground surface. Therefore.. MW-7 eras also completed as a Fort Hayes %veil at approximately the same depth as MW-6. TR-06 requires quarterly monitoring of MW-6 and MW-7. The initial and subsequent 2018 quarterly monitoring activities and results for MW-6 and MW-7 are summarized below. Wei!.Sampling After development by surging and bailing right after installation, new monitor wells MW-6 and MW-7 were secured and left undisturbed for 27 days before the initial sample collection on January 3,2018. Additional quarterly monitoring evenLs occurred on April 27.September 26,and December 12. 2018. The April and December events were conducted by CCG in conjunction with GCC staff. Preliminary April sampling results were transmitted to DRMS by GCC on May 7. 2018(cover letter included in Attachment Q. The September event was conducted by GCC and documented in a letter to DRMS dated November 19,2018 (Attachment Q. 'GCC reported that in September neither MW-6 or MW-7 yielded enough water after being purged to provide representative groundwater samples. Monitoring,and sample collection from MW-6 and MW-7 were performed applying guidance from Colorado Department of Public Health and Environment's(CDPHE's)Suggested Sampling Protocol for Ground Water Monitoring'Wells. Prior to sample collection,the static water level and total depth were measured with an electronic water-sensing probe and results were used to calculate the wetted casing volume. The wells were purged and sampled using dedicated and disposable polyclfiylene bailers. After removal of each purge volume, field water quality parameters including pH,temperature,specific conductance were measured using a calibrated YSI Pro 1030 meter. Field parameters generally were measured in a minimum of three successive well casing volumes and until two or more field parameters stabilized(i.e., three successive reading within 10%), or the w-elI was purged dry. Samples for dissolved metals analysis were field-filtered using a peristaltic pump and high capacity 0.45-micron filters. During each monitoring event,MW-6 bailed dry before three casing volumes could be removed. During the January,April and December events,2.6,2.9 and 2.5 casing volumes were removed,respectively,before the well hailed dry. The well recharged an adequate amount after several hours to collect samples for all or most analytes.During September, GCC reported only 1.25 casing volumes could be removed and the well did not recharge sufficiently within 24 hours to collect an adequate or representative sample. Except for the September event,MAI-7 yielded ample water for sample collection. For September,GCC staff reported two casing volumes were removed before M W-7,went dry,and it did not recover an adequate amount within 24 hours to sample. Groundwater samples were immediately placed into clean,laboratory-supplied containers,labeled, togged onto a chain-of-custody form,and stored on ice for same-day hand delivery or overnight shipping delivery to Origins Laboratory, Inc.in Denver.Colorado for laboratory.analysis in accordance with TR-06(Colorado Agricultural Use Standards parameters). In addition,total dissolved solids(TDS)was analyzed when sample volume was adequate. Close Consulting Group LLC