Trihalomethane (THM) Timeline Summary
Date
May-2012
Feb-2013
May-2014
Early summer 2014
Jun-2014
Action
Charlotte Water changed THM sampling to 12 specific locations per U.S. EPA rule
change (Prior rule was based on system-wide average)
Duke Energy began applying calcium bromide to coal at Marshall Power Plant on
Lake Norman & Allen Power Plant on Lake Wylie (we learned this recently from Duke)
2nd quarter 2014 THM samples show bromide related THMs are higher than normal
– water system compliant w/ standards
Charlotte Water modified operations to more aggressively manage water age,
treatment processes to minimize THM formation
Charlotte Water started water treatment process study
Aug-2014
3rd quarter 2014 THM samples show bromide related THMs higher than normal and
the trend is upward – water system compliant w/ standards
Nov-2014
4th quarter 2014 THM samples continue to show bromide related THMs higher than
normal – water system compliant w/standards
Fall / Winter 2014
Charlotte Water informally consulted Duke Energy about the increasing bromidebased THM levels looking for guidance as to source and what we should expect going
forward
April & May 2015
Charlotte Water staff met w/ Duke staff at Franklin WTP to discuss bromide & THM
levels - Duke listened and we agreed to share data
Charlotte Water staff consulted with NC Department of Environment and Natural
Resources (DENR) staff several times about THM levels; Charlotte Water was taking
action to manage / optimize system
May 6, 2015
2nd quarter 2015 THM samples show bromide-related THMs are higher than normal
and the trend is higher than same quarter 2014 – water system compliant w/
standards
Feb. 3, 2015
May 19, 2015
May 20, 2015
May 19-22, 2015 (no
documentation of exact
date)
Week of May 26, 2015
Charlotte Water staff met to review and discuss THM data trends and actions
needed - system optimization and hydrant flushing are on-going
City Manager's Office briefed about THM issue
CLTWater shared bromide related THM graphic with Duke Energy to better illustrate
magnitude of impacts
Duke Energy stopped applying calcium bromide to coal at Marshall and Allen Power
Plants
Early July 2015
July 16, 2015
July 20, 2015
4 times in July
Process control THM sample (also referred to as SNC or Special Non-compliance
samples) results are higher than normal & raise concern about potential for THM
violation on 3rd quarter regulatory compliance samples
City Manager's Office briefed about THM issue
Mecklenburg County Health Director briefed about THM issue
CLTWater staff conference calls w/ Duke staff to share data
July 24, 2015
SNC sample results lower than early July samples but higher than normal
July 28, 2015
July 28, 2015
Additional SNC sample results lower than 7/24 samples but higher than normal
City Manager's Office briefed about THM issue
Aug. 2, 2015
Aug. 5, 2015
Briefing with City Manager, Mecklenburg County Health Director, others – Health
Director confirmed no health risks
CLT Water conference call w/ Duke staff to share data
Aug. 12, 2015
3rd quarter THM sample results received - system compliant with standards, 8
locations exceed state's notification level requirement
Aug. 12, 2015
Aug. 13, 2015
Aug. 13, 2015
Meeting of water utilities w/ Duke Energy - shared data & THM compliance status
Customers notified per state requirements
Voluntary notification to media