2020-03-19_HYDROLOGY - M1977348

• Permit No: M1977348
• IBM Index Class Name: HYDROLOGY
• Doc Date: 3/19/2020
• Doc Name: Water Monitoring - Groundwater
• From: Golder
• To: DRMS
• Email Name: AME
• Media Type: D
• Archive: No

14 GOLDER
I
March 17, 2020 Project No. 19121576
' Ms. Amy Eschberger
Colorado Division of Reclamation Mining and Safety
Department of Natural Resources
1313 Sherman Street, Room 215
Denver, Colorado 80203
' SECOND SEMI-ANNUAL EVENT 2019 GROUNDWATER SAMPLING AT THE BOETTCHER QUARRY
Dear Ms. Eschberger:
On behalf of Holcim (US) Inc., Golder Associates Inc. (Golder) is pleased to submit analytical laboratory results
' for the second semi-annual 2019 groundwater sampling event at the Boettcher Limestone Quarry near La Porte,
Colorado. Attached are Tables 1 through 7, summarizing the results, and a copy of the laboratory report
(Attachment 1). Field sheets for the purging and sampling are presented in Attachment 2. In addition to sampling
' wells MW-1 through MW-7, a field duplicate at MW-6 (MW-20)and a field blank (MW-15)were collected. The
locations of monitoring wells MW-1 through MW-7 are presented in Figure 1.
' In December 2016, the Colorado Division of Reclamation Mining and Safety approved a revision to change the
required groundwater monitoring frequency from quarterly to semi-annually (Revision TR07) based on evidence
that the groundwater wells were not fully recharging between sampling events. Figure 2 presents a graph of the
' monitoring well water elevations measured during each sampling event from 2013 to present.
Upon receipt of the laboratory reports, Golder reviewed the results, and a general analytical data evaluation was
performed. Results of this evaluation included the following:
' • The samples were received by the laboratory at the appropriate temperature.
I .'
The required analyses were performed.
■ The analyses were conducted within their respective EPA-recommended hold times, apart from pH.
Measurements for pH should be conducted within 15 minutes of sample collection; thus, the laboratory pH
measurement will always be out of hold time.
Based on the above review, the laboratory results are considered valid for the sampling event. Reported
concentrations are consistent with previous events, and the analytes that exceeded the Interim Narrative
Standard for this sampling event are listed by sampling location below:
■ MW-1: Selenium, Uranium, Sulfate, and Gross Alpha
■ MW-2: Barium, Boron, Iron, Manganese, and ChlorideII
Golder Associates Inc.
7245 W Alaska Drive,Suite 200,Lakewood,Colorado,USA 80226 T:[phone] F:[phone]
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