Transcript Document

Mercer Island E. coli Event
Bob James, ODW
December 2014
Today’s Talk
• Coliform Basics – the organism and the rule
requirements
• Describe Mercer Island and the coliform event
• Explain the role of the health agencies
• Capture some lessons learned
Total Coliform Bacteria
Total coliform bacteria are common in the
environment (soil or vegetation) and are generally
harmless. If a lab detects only total coliform
bacteria in drinking water, the source is probably
environmental and fecal contamination is unlikely.
However, if environmental contamination can
enter the system, pathogens could get in too. It is
important to find and resolve the source of the
contamination.
E. coli Bacteria
E. coli is a subgroup of the total coliform group.
Most E. coli bacteria are harmless and exist in the
intestines of people and warm-blooded animals.
However, some strains can cause illness. The
presence of E. coli in a drinking water sample
usually indicates recent fecal contamination. That
means there is a greater risk that pathogens are
present.
E. coli O157:H7
• A specific strain of E. coli bacteria
• Causes most disease outbreaks.
• When a drinking water sample is reported as “E.
coli present:”
o It does not mean that O157:H7 is present.
o It does indicate recent fecal contamination.
o Boiling contaminated drinking water destroys
all forms of E. coli, including O157:H7.
Coliform and Chlorine
Disinfection with chlorine should provide 3-log
inactivation of coliform bacteria in less than 2.5
minutes. The CT is 0.25 mg-min/L.
The Total Coliform Rule
Purpose:
• Determine the adequacy of water
treatment.
• Determine the integrity of the distribution
system and its impact upon water quality.
The Total Coliform Rule
• Collect routine total coliform samples from the
distribution system every month.
• Samples must be analyzed by an accredited laboratory
for the presence of total coliform.
• Positive samples must be analyzed for E. coli.
• Three repeat samples must be collected for every
positive routine total coliform sample.
• An acute MCL violation is created if two or more of the
four samples contain total coliform and at least one of the
samples contains E. coli.
• Public Notification is required in response to an acute
MCL violation within 24 hours.
Mercer Island Facts
• Population: 22,270 People
• Service Connections: 7,335 (62 Food Service
Permits)
• Source: Seattle Public Utilities (SPU)
• Storage: Two 4 MG Reservoirs
• Distribution System:
o 121 Miles of Water Main
o Significant Amount of Unlined Cast Iron
o 86 PRV Vaults and stand alone Air-Vacuum
Assemblies
Mercer Island Supply
Facilities
4 MG
Reservoir
Reservoir
Zone
(398)
4 MG
Reservoir
Pump
Station
Pumped
Zone
(492)
By-pass
Valve
SPU
Supply
Lines
Mercer Island Facts (cont.)
• Pump Stations:
o Main PS (9,000 gpm to elevation 492)
o First Hill PS (1,150 gpm to elevation 456)
• Pressure Zones:
o Reservoir Zone – 398 (31.4% of total demand)
o Pumped Zone – 492 (68.6% of total demand)
o First Hill Zone – 456 (2.2% of total demand)
o Many Smaller Zones Supplied Through PRVs
(range 215 – 285 ft. HGL)
Mercer Island Pressure Zones
Mercer Island Coliform
Monitoring Program
• Seattle Public Utilities Regional Coliform Monitoring
Program
• SPU Collects All Routine Samples (> 880/month)
• On Mercer Island SPU collects 18/Month from Five
Sample Stations
• Mercer Island Collects Repeats and Investigative
Samples
• All Samples Are Analyzed By SPU’s Laboratory
Mercer Island Coliform Monitoring Sites
Mercer Island Timeline
Wednesday - September 24th
• Seattle collected 61 samples from Seattle and its
wholesale customers
• Two of the 61 samples were collected from Mercer
Island
• Five samples contained total coliform
• One of the Mercer Island samples contained E. coli
Mercer Island Coliform Results
Collection Date: 9/24/2014
Results Reported: 9/26/2014
Total Coliform Absent
Total Coliform Present
and E. coli Present
Mercer Island Timeline
Friday - September 26th
• Seattle collects repeat samples from its distribution
system
• Soos Creek collects repeat samples from its
distribution system
• Mercer Island collects three repeat samples and six
investigative samples from its distribution system
• SPU, Public Health – Seattle & King County, and DOH
prepare a draft news release with help from Soos
Creek and Mercer Island
Mercer Island Coliform Results
4
Collection Date: 9/26/2014
Results Reported: 9/27/2014
Total Coliform Absent
Total Coliform Present
and E. coli Present
Mercer Island Timeline
Saturday - September 27th
• All repeat samples are satisfactory
• Four out of six investigative samples collected by
Mercer Island contain E. coli
• Decision is made to issue a Health Advisory at 11:00
am
• Mercer Island collects eight more investigative
samples and begins to monitor chlorine residual
throughout the system
• News Release issued at 3:45 pm followed by a press
conference at 4:30 pm
• Special Purpose Investigation conducted
DOH Special Purpose
Investigation
• Certified Operator Interview
o Pressure Events
o New Construction
o HPC Results and Chlorine Residual Measurements
o Flushing
o Operational Changes
• Reservoir Inspections
o Vents
o Overflows
o Drainlines
Mercer Island Coliform Results
Collection Date: 9/27/2014
Results Reported: 9/28/2014
4
Total Coliform Absent
Total Coliform Present
and E. coli ???
Mercer Island Timeline
Sunday - September 28th
• One out of eight investigative samples contains total
coliform
• No E. coli present in the sample at the 18-hour mark
• Mercer Island collects eleven investigative samples
and continues to monitor chlorine residual and flush if
necessary
• Health Advisory remains in effect
Mercer Island Coliform Results
Collection Date: 9/28/2014
Results Reported: 9/29/2014
4
Total Coliform Absent
Total Coliform Present
and E. coli Absent
Mercer Island Timeline
Monday - September 29th
• One out of eleven investigative samples contains
total coliform
• No E. coli present in any sample
• Mercer Island collects six investigative samples and
continues to monitor chlorine residual and flush if
necessary
• Health Advisory lifted
Mercer Island Coliform Results
Collection Date: 9/29/2014
Results Reported: 9/30/2014
Total Coliform Absent
Mercer Island Timeline
Tuesday - September 30th
• Six investigative samples indicate no total coliform
bacteria in the system
• Mercer Island collects six investigative samples and
continues to monitor chlorine residual and flush if
necessary
Mercer Island Coliform Results
Collection Date: 9/30/2014
Results Reported: 10/1/2014
Total Coliform Absent
Mercer Island Timeline
Wednesday - October 1st
• Six investigative samples indicate no total coliform
bacteria in the system
• Mercer Island collects six investigative samples and
continues to monitor chlorine residual and flush if
necessary
Mercer Island Coliform Results
Collection Date: 10/1/2014
Results Reported: 10/2/2014
Total Coliform Absent
Total Coliform Present
and E. coli Present
Mercer Island Timeline
Thursday - October 2nd
• One of six investigative samples results indicate E.
coli present in the distribution system
• Health Advisory re-issued
• Initial Action Plan is developed and implementation
begins
Mercer Island Initial Action
Plan
• Increase samples to 18 per day from throughout the
island using standard collection protocols
• Dive the reservoirs
• Increase chlorine residual entering the tanks
• Inspect all construction sites
• Inspect all underground vaults
• Identify and test all high hazard backflow assemblies
that had not been tested within the last 12 months
• Monitor chlorine and flush distribution system to
displace the water
Mercer Island Timeline
Sunday - October 5th
• Mercer Island child reported ill. Tests indicate
sickness due to E. coli
Mercer Island Timeline
Wednesday - October 8th
• The results of approximately 100 water samples collected
since October 2nd indicate no total coliform bacteria in the
water system
• Action Plan implementation underway
o Primary distribution grid flushed
o Underground vaults inspected
o Increased chlorine residuals in the distribution
system
o Backflow assemblies tested
• Health Advisory lifted
DOH Role
• Regulator
• Technical specialist
• Educator
• Risk communications
• Public health partner
• We want to be in the room with the decisionmakers
Public Health – Seattle & King
County Role
• Emergency response
• Permit food service establishments
• Technical specialist
• Educator
• Should be in the room with the decision-makers
Utility Partners
• City or County General Purpose Government
• Schools & School Districts
• Medical Community
• Business Community
• Adjacent Utilities
• Volunteers
Communications
• Distribute Notice within 24 Hours
• Message coordination
• News Release, Reverse 911, door hangers, social
media, & webpage
• Scripts for news release, Reverse 911, webpage,
& telephone
• Boundaries
• Staying ahead of social media
DOH Lessons Learned and
Expectations
• A large chlorinated system – operational flexibility
• Incident Command Structure
• Response time
• Staffing requirements
• Communicating with Customers, Media & Partners
• Number and coverage of sample sites
• Best Management Practices
• The Revised Total Coliform Rule
Questions?