Laserfiche WebLink
RECEIVE <br /> D <br /> SEP 2 6 2QW <br /> G O L D E R 01M"of RECLWnoN <br /> ' WftMDWMY <br /> September 25, 2019 Project No. 19121576 <br /> ' Ms. Amy Eschberger <br /> Colorado Division of Reclamation Mining and Safety <br /> ' Department of Natural Resources <br /> 1313 Sherman Street, Room 215 <br /> Denver, Colorado 80203 <br /> ' FIRST SEMI-ANNUAL EVENT 2019 GROUNDWATER SAMPLING AT THE BOETTCHER QUARRY <br /> Dear Ms. Eschberger: <br /> ' On behalf of Holcim (US) Inc., Golder Associates Inc. is pleased to submit analytical laboratory results for the first <br /> semi-annual 2019 groundwater sampling event at the Boettcher Limestone Quarry near La Porte, Colorado. <br /> J Attached are Tables 1 through 7, summarizing the results, and a copy of the laboratory report (Attachment 1). <br /> Field sheets for the purging and sampling are presented in Attachment 2. In addition to sampling wells MW-1 <br /> through MW-7, a field duplicate at MW-1 (MW-20) and a field blank (MW-15)were collected. The locations of <br /> ' monitoring wells MW-1 through MW-7 are presented in Figure 1. <br /> In December 2016, the Colorado Division of Reclamation Mining and Safety approved a revision to change the <br /> required groundwater monitoring frequency from quarterly to semi-annually (Revision TR07) based on evidence <br /> ' that the groundwater wells were not fully recharging between sampling events. Figure 2 presents a graph of the <br /> monitoring well water elevations measured during each sampling event from 2013 to present. <br /> ' Upon receipt of the laboratory reports, Golder reviewed the results, and a general analytical data evaluation was <br /> performed. Results of this evaluation included the following: <br /> ' ■ The samples were received by the laboratory at the appropriate temperature. <br /> ■ The required analyses were performed. <br /> ' ■ The analyses were conducted within their respective EPA-recommended hold times, apart from pH. <br /> Measurements for pH should be conducted within 15 minutes of sample collection; thus, the laboratory pH <br /> measurement will always be out of hold time. Additionally, alkalinity was accidentally omitted from the initial <br /> analysis and was therefore analyzed outside hold time. The laboratory pH and alkalinity measurements were <br /> consistent with past sampling events. <br /> Based on the above review, the laboratory results are considered valid for the sampling event. The laboratory <br /> ' report in Attachment 1 contains duplicate results for some analytes because the laboratory initially utilized <br /> detection limits greater than the Interim Narrative Standard due to sample dilutions required because of sample <br /> matrix interferences. The practical quantitation limit for nickel for the sample collected from MW-1 was above the <br /> ' Interim Narrative Standard; however, the sample was not detected above the method detection limit which was <br /> Golder Associates Inc. <br /> ' 44 Union Boulevard,Suite 300 Lakewood,Colorado,USA 80228 T:+t 303 980-0540 +t 303 985-2080 <br /> c\users\cocarpenter\golder associates\p19121576.2019 boettcher quarry gw-6 deliverables\letters\1 91 21 576-001--1-1-0-first semi annual_gw_event boettcher_quary.docx <br /> Golder and the G logo are trademarks of Golder Associates Corporation golder.com <br />