2020-08-10_HYDROLOGY - M1977348

• Permit No: M1977348
• IBM Index Class Name: HYDROLOGY
• Doc Date: 8/10/2020
• Doc Name: Water Monitoring - Groundwater
• From: Golder Associates
• To: DRMS
• Annual Report Year: 2020
• Report Quarter_Month: 1
• Email Name: AME
• Media Type: D
• Archive: No

V
GOLDER
August 5, 2020 Reference No. 20144265-2-L-0
Ms.Amy Eschberger RECEIVED
t Colorado Division of Reclamation Mining and Safety AUG Department of Natural Resources 10 _67a
' 1313 Sherman Street, Room 215 UWASION OF RECLAMATION
Denver, Colorado 80203 RAINJNG.cY SAFE
FIRST SEMI-ANNUAL 2020 GROUNDWATER SAMPLING EVENT 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 first semi-annual 2020 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-5 (MW-20)and a field blank (MW-15)were collected. The
locations of monitoring wells MWA 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.
■ The required analyses were performed.
' ■ The analyses were conducted within their respective United States Environmental Protection Agency
(USE PA)-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: iron, selenium, uranium, sulfate, and gross alpha
' ■ MW-2: barium, boron, iron, manganese, and chloride
Golder Associates Inc.
7245 W Alaska Drive,Suite 200,Lakewood,Colorado,USA 80226 T [phone] F [phone]
' Golder and the G logo are trademarks of Golder Associates Corporation golder.com