mercer island e. coli event bob james, odw december 2014

Mercer Island E. coli Event

Bob James, ODWDecember 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 BacteriaTotal coliform bacteria are common in theenvironment (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 canenter the system, pathogens could get in too. It is important to find and resolve the source of the contamination.

E. coli BacteriaE. coli is a subgroup of the total coliform group. Most E. coli bacteria are harmless and exist in theintestines of people and warm-blooded animals. However, some strains can cause illness. Thepresence of E. coli in a drinking water sample usually indicates recent fecal contamination. Thatmeans 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 Maino Significant Amount of Unlined Cast Irono 86 PRV Vaults and stand alone Air-Vacuum

Assemblies

Mercer Island Supply Facilities

SPU Supply Lines

Pumped Zone (492)

Reservoir Zone (398)

Pump Station

4 MG Reservoir

4 MG Reservoir

By-pass Valve

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 TimelineWednesday - 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

Collection Date: 9/24/2014Results Reported: 9/26/2014

Total Coliform Absent

Total Coliform Presentand E. coli Present

Mercer Island Coliform Results

Mercer Island TimelineFriday - 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



Total Coliform Present and E. coli Present


4

Mercer Island TimelineSaturday - 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 Interviewo Pressure Eventso New Constructiono HPC Results and Chlorine Residual Measurementso Flushingo Operational Changes

• Reservoir Inspectionso Ventso Overflows o Drainlines



Total Coliform Presentand E. coli ???


4

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



Total Coliform Present and E. coli Absent


4


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


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


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



Total Coliform Present and E. coli Present



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


Sunday - October 5th • Mercer Island child reported ill. Tests indicate sickness due to E. coli

Mercer Island TimelineWednesday - 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 flushedo Underground vaults inspectedo Increased chlorine residuals in the distribution

systemo 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 decision-makers

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?

mercer island e. coli event bob james, odw december 2014

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