DERR-2025-009072

Mayf lower Mine Site Cteanup TimeLine
2017
Extet[ purchases Mayf lower Stitching property with known contamination from historic
mining operations, but does so as a Bona Fide Prospective Purchaser and obtains an
EnforceabLe Written Assurance from the Division of EnvironmentaI Response and
Remediation (DERR), which requires remediati0n.
2018
Mayftower project entered into the State of Utah EnvironmentatVotuntary C[eanup
Program, administered bythe DERR. Site Cha racterization begins and finat Site
Cha racte rization Report was accepted by DERR.
2019
Aprit 2019 - Remedia[ Action Ptan Approved by DERR after pubLic notice and comment
Juty 2019 - lmpLementation of RemediaI Action Ptan begins
November 2019 - Winter shutdown
2020
February 2020 - cleanup activities stopped due to COVID outbreak
March 2020 - Site C ha racterizatio n Report for Star Mine and Gtencoe Canyon area
compteted
April2020 - Limited cleanup activities resume with COVID precautions and distancing in
p[ace
September 2020 - Yet[ow Pond, Rec Sep 17, Rec 12 remediation comp[ete
November 2020 - Winter shutdown
2021
Aptia 2021 - Remediation activities resume
Summer 2021 - Remedia[ Action P[an prepared for Star Mine and G[encoe Canyon
September 2021 - Protective caps instalted in the Mayftower Mine area, hardscape and
greenspace [iner atso insta tted
October 2021 - Asphatt Paving instatted on east side, completing the hardscape cover area
November 2021 - Greenspace cover on west side comptete
December 2021 - Winter shutdown
Mayflower Mine Site Cteanup TimeLine
2022
lune 2022 - Remediation activities begin in Gtencoe Canyon and Star Mine area to ctose
out requirements imposed by the Division of Water Quatity (DWQ)
Spring 2022 -Work by Extet['s contractor RMEC to compite the thousands of pages of
sampting results and data points as part 0f the completion of the VCP
June 2022 - submission of First Draft of Remediat Action Report to DERR for Mayftower
a rea
2023
October 2023 - completion of the Star Mine Remediation in Gtencoe Canyon
July 2023 - repair remediation in McHenry Canyon due to [arge votume snow melt
June 2023 - address subsidence in Mayftower waste rock area due to stormwater
infi[tration
August - work on ptan to manage stormwater runoff and imptement water monitoring ptan
for Mayf lower mine area including water sampting measures
2024
Summer 2024 - repair waste rock asphatt cap where subsidence occurred
Summer 2024 - imptement stormwater infittration measures to prevent water from getting
into the waste rock
Fatt 2024 - evatuate history of clean water sampling f rom site
2025
Aprit 2025 - Submission of updated and f inaI RemediaI Action Report
May 2O25 - DERR approves of fina[ Remediat Action Report
Spring - Fatt 2025 - Exte[[ prepares, in ctose coordination with DERR, the closeout
documentation for VCP area, inctuding muttipte environmentaI covenants, a Site
Management P[an, and DERR finatizes the Certificate of Comptetion (COC)
October 2025 - Environmental Covenants signed and recorded
November 2025 - No further action letter detivered by DWQ for Star Mine Site
December 2025 - COC detivered and recorded by DERR, ctosing out the project.