# WATERBORNE
SALMONELLA OUTBREAK IN ALAMOSA, COLORADO MARCH AND APRIL 2008

OUTBREAK IDENTIFICAT ION, RESPONSE, AND INVEST IGATION

Safe Drinking Water Program
Water Quality Control Division

Prepared by:
Ron Falco, P.E.

Sharon Israel Williams, P.E.

November 2009Salmonella Outbreak in Alamosa, Colorado, March and April 2008

1 

## Waterborne Salmonella Outbreak in Alamosa, Colorado

March and April 2008:

Outbreak identification, response and investigation

CONTENTS

ACKNOWLEDGEMENTS

................................ ................................ ................................ ......... 3

EXECUTIVE SUMMARY

................................ ................................ ................................ .......... 4

PART I: BACKGROUND

................................ ................................ ................................ ........... 6

I NTRODUCTION

................................ ................................ ................................ ............................. 6
A BOUT A LAMOSA
, C OLORADO

................................ ................................ ................................ .... 7
A BOUT S

ALMONELLA

................................ ................................ ................................ .................... 9

PART II: CRISIS AND RESPONSE

................................ ................................ ........................ 11

I DEN TIFYING A W ATERBORNE O UTBREAK

................................ ................................ ................. 11
D ISINFECTING AND F LUSHING THE C ITY ’ S W ATER S YSTEM

................................ ...................... 17
P RELIMINARY F IELD I NVESTIGATION

................................ ................................ ......................... 26
B ACK TO THE N EW N ORMAL

................................ ................................ ................................ ...... 28

PART III: POST

- CRISIS

................................ ................................ ................................ .......... 32

A FTER THE E MERGENCY : A PRIL

- O CTOBER 2008

................................ ................................ ....... 32
C ONDUCTING THE I NVESTIGATION

................................ ................................ ............................. 34

PART IV: INVESTIGATION AN D OBSERVATIONS

................................ ......................... 51

C LOSING THE I NVESTIGATION

................................ ................................ ................................ .... 51
L ESSONS L EARNED

................................ ................................ ................................ ..................... 53
C ONCLUSION

................................ ................................ ................................ .............................. 63Salmonella Outbreak in Alamosa, Colorado, March and April 2008

2 

## FIGURES AND TABLES

Figure 1: Alamosa, Colorado

................................ ................................ ................................ .......... 7

Figure 2: City of Alamosa Public Water System, March 2008 (Courtesy of Olsson Associates)

.. 8

Figure 3: Sectors for Distribution System Disinfection and Flushing (Courtesy of Olsson Associates)

................................ ................................ ................................ ................................ .... 20

Figure 4: Epidemic Curve

................................ ................................ ................................ ............. 48

Table 1: Investigation Summary...........................................................................5 2



## APPENDICES

APPENDIX A: Event Summary Timeline

APPENDIX B: Summary of Water Quality Data Collected During the Outbreak Response

APPENDIX C: Map of City of Alamosa with 2008 Total Coliform and Salmonella Sampling Prior to System Disinfection and Flushing

APPENDIX D: A Photo Journal Summary of the Salmon ella Outbreak in Alamosa, Colorado

APPENDIX E: Literature ReviewSalmonella Outbreak in Alamosa, Colorado, March and April 2008

3 

### ACKNOWLEDGEMENTS

Without human infrastructure, physical and regulatory infrastructure cannot stand alone. The authors would like to thank everyone who gave of themselves to respond to the S almonella
outbreak in Alamosa and to contribute to this report.Salmonella Outbreak in Alamosa, Colorado, March and April 2008

4 

### EXECUTIVE SUMMARY

An outbreak of waterborne disease associated with Salmonella in drinking water struck Alamosa, Colorado during March and April 2008. The city of Alamosa’s public water system that supplies drinking water to the community became contaminated w ith Salmonella bacteria

. Alamosa’s

popu lation is about 8, 9 00 people. The outbreak resulted in 44 2 reported illnesses , 122 of which
were lab oratory

- confirmed, and one death. Epidemiological estimates suggest that up to 1

, 300 people may have been ill. Details on the epidemiological investigation are pending publication by the CDPHE Disease Control an d Environmental Epidemiology Division.

Alamosa’s dri nking water comes from deep artesian wells in an aquifer considered to be a protected groundwater source. Prior to the outbreak, the city’s drinking water was not
chlorinated for disinfection. A waive r from the statewide requirement for disinfection was granted to Alamosa in 1974. In general, the city was historically in compliance with all health

based drinking water standards, with the exception of the arsenic standard

. A statewide response to the outbreak lasting about one month involving numerous responders was coordinated using the National Incident Management System (NIMS) and Incident Command System (ICS). The Safe Drinking Water (SDW) program within the Colorado Department of Public Health a nd Environment is responsible for implementing the federal Safe Drinking Water Act in Colorado. During the outbreak, the SDW program responded as part of the ICS to protect public health and provide technical support to the city and to other emergency

res ponders.

During the outbreak residents were advised to drink bottled water, and then the entire water system was flushed and disinfected with chlorine to kill the Salmonella bacteria. A boil water order followed the bottled water order, and it remained in place until tests confirmed that the city’s water was safe to drink again. Because of the quick operational response and the changes made to the physical infrastructure of the Alamo sa public water system, the water in Alamosa has been safe to drink since April 2008 . The city has since installed advanced treatment processes and improved system operations.

The investigation involved a detailed review of the water system, historical records, and interviews with city of Alamosa personnel, local health officials and responders to the outbreak. Although there were several possible causes of the outbreak, our conclusion is that an animal
source of fecal contamination entered the Weber Reservoir, and then spread throughout the entire system. The Weber Reservoir is a ground

- level water storage reservoir near the Weber Well,
which was the primary water well in use by the city, prior to the outbreak. The Weber Reservoir
had several small cracks and holes that likely allowed the contamination to enter. These
breaches may have existed for a relatively long period of time

. The SDW program strives to prevent disease outbreaks. A team of experts is on call 24 hours a day, 7 days a week, 36 5 days per year to respond to events that may put public health at risk and help public water systems correct the problems that can lead to disease outbreaks. Typically, this team responds to about 50 acute risk events per year . It is not possible to dir ectly state that theSalmonella Outbreak in Alamosa, Colorado, March and April 2008

5 team has prevented disease outbreaks, but the actions taken by the team, including issuing bottled or boil water orders, reduce the risk of waterborne disease. However, severe personnel
limitations at the state level have resulted in an inability to address every potential area of risk associated with drinking water in Colorado. This is well

- documented, and extends to the 1970s at the SDW program’s inception.

As recently as the early 1980s, disease outbreaks associated with drinking water were relatively

common in Colorado , often occurring more than once a year. The documented disease outbreaks in the 1980s primarily occurred at systems that failed to adequately treat water from rivers or streams. As a result, the SDW pro gram focused its resources on establishing and enforcing adequate treatment requirements for these systems. Since the 1980s, improvements to physical, regulatory, and human infrastructure dramatically reduced the potential for drinking water supplies to b ecome contaminated and cause disease.

Although the SDW program’s resources have increased in recent years, the increases have generally been tied to implementing new regulations, and the emphasis on treatment during inspections remained. Unfortunately, the city had not addressed integrity issues at the Weber
Reservoir and those issues were not detected during inspections of the Alamosa water system conducted by the SDW program during the decade prior to the outbreak, including an inspection
in August 2007

. The SDW program has developed and is implementing several strategies to further reduce the likelihood of waterborne disease outbreaks in Colorado. These strategies include:

 Prioritize responding to deficiencies at water systems that do not disinfe ct;

 Review disinfection waivers and withdraw them whe n needed to protect public health;

 Enhance oversight of sampling, water storage and distribution piping during inspections;

 Update and modify regulations related to disinfection waivers and groundwater d isinfection;

 Ensure compliance with requirement for water systems to maintain residual chlorine levels in water distribution systems;

 Revise regulations associated with controlling hazardous cross connections at water systems;

 Ensure that deficiencies ide ntified during inspections are corrected in a timely fashion;

 Launch training initiatives to help public drinking water systems to optimize water storage tank and distribution system operating and maintenance practices ; and,

 Develop strategies to enhanc e response capabilities to drinking water emergencies

.

This report provides a comprehensive documentation of the events in Alamosa associated with the disease outbreak including the response, cause, and lesson s learned. It is hope d that an improved understanding of this event will help all those involved in the serious business of providing safe drinking water to prevent waterborne disease outbreaks.Salmonella Outbreak in Alamosa, Colorado, March and April 2008

6 

### PART I: BACKGROUND

INTRODUCTION

In March 2008, the c ity of Alamosa, Colorado expe rienced a disease outbreak associated with drinking water. Salmonella bacteria contaminated the city’s public drinking water supply, leading to 442 reported cases of illness in the community, 122 of which were lab oratory confirmed, and one death. Epidemi ological estimates suggest that up to 1

, 300 people may have
been ill.

Salmonella outbreaks associated with drinking water are rare . S ince the 19 7 0s

, the annual number of disease outbreaks associated with drinking water has declined significantly

. In re cent decades, layers of public health protections have been designed and implemented specifically to prevent disease outbreaks. Th ese include federal and state regulations, monitoring requirements, standards for new physical infrastructure, technological ly advanced treatment processes, professional certification of water treatment operators, and improvements in source water protection. Even with these improvements, there are documented outbreaks associated with drinking water each year in the United Stat es.

In the 21 st century physical, regulatory, and human infrastructure exists from water source to tap to ensure the safest possible water reaches consumers. In March 2008, that infrastructure failed to prevent the waterborne disease outbreak in Alamosa

. However, o nce the outbreak in Alamosa was confirmed, the drinking water community across Colorado, in partnership with emergency responders and public health professionals, rallied together to respond quickly and return the city and community to normal.

This report has been prepared by the Safe Drinking Water (SDW) Program within the Water Quality Control Division of the Colorado Department of Public Health and Environment (CDPHE). The purpose of this report is to:

1. Do cument the identification of a waterborne outbreak of Salmonella associated with drinking water in Alamosa, Colorado in March and April 2008.
2. Describe the response to the outbreak to eliminate Salmonella bacteria from the city’s drinking water.
3. Report the follow

- up activities conducted by the city and state regulatory agency, including cause investigation.
4. Offer lessons learned and describe modifications to SDW program activities
undertaken after the outbreak.Salmonella Outbreak in Alamosa, Colorado, March and April 2008

7 ABOUT ALAMOSA, COLOR ADO

The c ity of Alamos a is located in south central Colorado, with nearby 14,000 foot mountain peaks in the scenic San Luis Valley. The city is the county seat and the commercial center of the valley and its community public water system serves 8, 9 00 people directly and over a thousand more through consecutive connections. The drive from Colorado’s capital city of Denver to the

c ity of Alamosa is close to 250 miles south and west. Figure 1 shows a map of Colorado.

FIGURE 1 : ALAMOSA, COLORADO

At the time of the outbreak, the physical infrastructure comprising Alamosa’s community public water system consisted of seven deep artesian wells, two elevated storage tanks, one ground

level storage reservoir, and approximately 50 miles of distribution line . Figure 1 shows a map of the city and major water system components. In February 2008, the month prior to the outbreak, only three of the city’s seven wells were serving the distribution system. Water from the wells was not chlorinated prior to distrib ution; the city had operated under a waiver from disinfection from the State of Colorado since 1974. Waivers of disinfection requirements are granted on a

case

- by

- case basis and are permanent unless the SDW program discovers cause to withdraw the
waiver.Salmonella Outbreak in Alamosa, Colorado, March and April 2008

8 FIGURE 2 : CITY OF ALAMOSA PUBLIC WATER SYSTEM, MARCH 2008 ( COURTESY OF OLSSON ASSOCIATES)

In the spring of 2008, the SDW program team was aware that, d ue to naturally occurring arsenic in the well sources, the city had frequent ly been in violation of the arsenic maximum
contaminant level (MCL) . A centralized treatment facility, consisting of flocculation, microfiltration and disinfection, had been in the planning stages for several years prior to theSalmonella Outbreak in Alamosa, Colorado, March and April 2008

9 outbreak. It went online i n a full service capacity in October 2008, and since that time the city has continually met the arsenic standard for compliance with state and federal drinking water regulations.

In addition to arsenic

- related violations, the city had a history of occasion al “ total coliform positive ” results but no other unusual patterns of non

- compliance with drinking water regulations
related to health effects. There also were no unaddressed significant deficiencies noted during routine sanitary surveys conducted by CDPH E ; however, this outbreak investigation did identify a pattern of violations of total coliform sampling procedures that had previously been undetected during routine compliance oversight activities

. At the time of the Salmonella outbreak in Alamosa, the s ystem had been recently evaluated by engineers from the private sector and the SDW program , and was understood to be maintaining compliance with regulations at a level

c onsistent with protection from acute risk to public health.

ABOUT SALMONELLA

SALMONELLA IN DRINKING WATER SO URCES

There are many different varieties, or serotypes, of Salmonella bacteria, and they are often spread through human or animal feces. Although rare in drinking water, Salmonella bacteria are found in every region of the U nited States and throughout the world. Millions , or even billions, of germs can be released in the feces of an infected human or animal. Salmonella may be found
in water sources such as wells that have been contaminated with the feces of infected humans or animals. Waste can enter the water in various ways, including sewage overflows, polluted storm water runoff, and agricultural runoff. Bacteria may also enter the potable water distribution system through deficiencies in water lines and tanks, or by cr oss

- contamination with non

- potable

water sources.

Disinfection with chlorine is a highly effective means of killing Salmonella bacteria. Properly treating drinking water with chlorine, and maintaining residual chlorine in the distribution system, is an im portant barrier against contamination.

Because Salmonella in drinking water is relatively rare, n ational and state regulations do not require monitoring for Salmonella in public water systems. Instead, monitoring for total coliform bacteria is required as an indicator of overall bacteriological quality. Monitoring for
chlorine levels also is required in Colorado for water systems that disinfect their water sources.

There have been rare documented outbreaks of disease associated with Salmonella in drinking
water in recent U.S. history. The two larges t outbreaks occurred in Riverside, CA in 1965, and Gideon, MO in 1993.

ABOUT SALMONELLOSIS

Salmonellosis is an inf

ection caused by Salmonella bacteria . Infection generally occurs after ingestin g food or drink contaminated with feces

, by person

- to

- person transmission, or by contactSalmonella Outbreak in Alamosa, Colorado, March and April 2008

10 with animals. Estimates of the number of Salmonella bacteria in an infective dose for a small
child found in the literature could be as low as 10 to 100 organisms , with adult s likely requiring a higher dose. The outbreak in Alamosa was attributed to a strain called Salmonella Typhimurium
that contaminated the drinking water supply.

The most common symptoms of salmonellosis include diarrhea, fever, and abdominal cramps. Symptoms typically develop 12 to 72 hours after exposure and usually last 4 to 7 days. Most people recover without treatment. Some peo ple may have severe diarrhea and may need to be hospitalized. In these people, the bacteria may spread from the intestines to the blood, and then to other parts of the body. Death is rare but can occur. The elderly, persons under 5 years of

age , and tho se with weakened immune systems are more likely to have a severe illness.

Laboratory tests can determine if Salmonella is the cause of illness. Salmonella is generally diagnosed by stool culture. Once the bacteria have been identified, further testin g can determine
the specific type and the right antibiotics for treatment

. Most people d o not seek care for their symptoms . Typically, an estimated 38 actual cases occur for each one reported.Salmonella Outbreak in Alamosa, Colorado, March and April 2008

11 PART II: CRISIS AND RESPONSE

IDENTIFYING A WATERB ORNE OUTBREAK

There are two surveillance systems that exist to identify a potential drinking water related disease outbreak. One is the routine surveillance of drinking water quality conducted by a public water system. In the case of Alamosa, the city operate s the public water system and has the responsibility to monitor drinking water quality at least as frequently as required by state and federal regulations. The other system is the routine surveillance of certain diseases reported by
laboratories and medic al providers to a network of local, regional and state health departments. The Alamosa outbreak was identified initially by the latter of these two systems. Before water quality testing indicated risk of an outbreak, cases of disease already were being r eported through the epidemiologists.

On Wednesday, March 12, 2008, three cases were reported by medical providers to the regional epidemiologist from the Alamosa County Nursing Service, and this information was reported to CDPHE epidemiologist on Marc h 14, 2008. On Monday, March 17, 2008, the epidemiologists working on the outbreak contacted the SDW program team to discuss the outbreak and the possibility that the outbreak was related to Alamosa’s public drinking water supply.

Details on the epidemiol ogical investigation that confirmed drinking water as the source are pending publication by the CDPHE Disease Control and Environmental Epidemiology Division, Alamosa County Nursing Service, and the federal Center for Disease Control and Prevention ( CDC ) M orbidity and Mortality Weekly Report waterborne surveillance publications

.

Once an outbreak of Salmonella was identified, an emergency situation was declared in
Alamosa. Several emergency response teams across the state deployed crews to Alamosa. Throughout this report, events are reported with the date that they occurred. Not all of this narrative is sequential in time, so a timeline of events i s included in Appendix A for reference.

SAFE DRINKING WATER PROGRAM ACUTE TEAM D EPLOYMENT

Once the ou tbreak was suspected to be linked to the drinking water supply by epidemiological evidence, the SDW program assembled an Acute Team and began to plan a response. The Acute
Team is a formal cross

- program working group within the SDW program that routinely responds to situations experienced by Colorado’s public water systems that represent potential acute public health risks . On average, the team responds once a week to issues like upset treatment
conditions , line breaks, and total coliform and positive E. coli positive results. The team offers regulatory and operational advice and coordinates with other agencies as needed to support public water systems experiencing difficulties . One of the team’s first responses was to direct
that water samples be collec ted across the city on Monday, March 17, 2008, and sent to the lab for total coliform analysis.Salmonella Outbreak in Alamosa, Colorado, March and April 2008

12 It is noteworthy to point out that the SDW program’s response at this point in the outbreak was part of a much larger emergency response effort that is not do cumented in detail in this report.
T he SDW program’s team focus ed on the public water system from a technical and engineering perspective. However, t he overall response effort included other teams from CDPHE, Alamosa County, Colorado’s Division of Emerge ncy Management, Colorado National Guard, and many others. All were working within the National Incident Management System (NIMS) utilizing the Incident Command System (ICS) framework to address many other local, state, and national
coordination efforts. The ICS framework included a centrally managed Joint Information Center (JIC), Public Information Officer (PIO), and Emergency Operations Center (EOC), all elements of a managed disaster response under Federal Emergency Management Agency (FEMA) guidelines. The SDW program team worked within the ICS to manage certain activities related
to inter

- agency coordination, bulk water delivery, and public notification of advisories and updates. Details on the overall emergency response have been reported by the CDP HE Emergency Preparedness and Response Division and are not included in this document.

BOTTLED WATER ORDER ISSUED

On March 18, 2008, t he SDW program team discussed issuing an order based solely on epidemiological evidence, but no water quality sampling res ults were available to confirm that drinking water was the source of the outbreak, and there were still some uncertainties in the epidemiological data. On Wednesday, March 19, 2008, the epidemiological data more clearly suggested that drinking water was the source of the outbreak, and the analytical results from 10 drinking water samples collected on Monday showed that one s ample was positive for total
coliform bacteria , and two sampl es were noted as turbid , or cloudy, by the laboratory

. People were getting sick from salmonellosis across the city, and drinking water was officially the suspected source. To protect the public from being exposed to Salmonella in their drinking water, th e SDW program team and Colorado’s Chief Medical Office r deci ded to issue an order to Alamosa req uiring them to advis e the public not to consume water straight from the tap. F ive days later, on March 24, 2008, the CDC laboratory results confirmed the prese nce of Salmonella in the public water system.

Three key considerations played into the decision to issue a bottled water order , and to choose that type of order instead of a boil water order . It was clear to the CDPHE team that it was not
safe to consume drinking water from the city’s public water system because of epidemiological
evidence of Salmonella contamination and sample results from March 17. The team considered that Alamosa had a long history of naturally occurring arsenic levels above state and federal standards. Anticipating the potential need to disinfect the city’s water system with chlorine, and to flush water from the system at high velocity, there was significant concern that arsenic could
be elevated during those processes to levels high enough to cause acute risk to public health. A
second consideration was that the source of contamination was unknown , so it was uncertain if other contaminants could have been in the drinking water. Additionally, boiling water would
concentrate arsenic a nd potentially other contaminants in the water to an unknown extent.

A boil water order would not have protected the public from potentially high arsenic levels. On the other hand, issuing a bottled water order without proper preparation to ensure suffici entSalmonella Outbreak in Alamosa, Colorado, March and April 2008

13 supplies of bottled water, or bulk supply of similar quality, could create other undesirable outcomes for the city

, including insufficient supplies in the area stores and impacts on the city’s
businesses. Although a bottled water order would create hardships and concerns about water availability, the department team determined that such an order was the best course of action as it would be most protective of public health.

Orders of this nature are commonly employed in Colorado to requir e public notification of a potential acute risk to health and to order water systems to advise the ir customers to either drink bottled water (“bottled water advisory”) or to boil water from the tap before drinking (“boil water advisory”). However, a bottl ed water order for such a large system in response to an actual disease outbreak was unprecedented in Colorado and presented a major public health challenge along with severe community disruption and economic impacts.

With a bottled water order in place, t he SDW program team next devised a plan for further response, including collecting and evaluating additional water quality data and requesting mutual aid from other public water systems and partners. The team also determined that the entire
distribution s ystem in Alamosa, including 50 miles of distribution line and 3 tanks, likely needed
to be disinfected and flushed.

INITIAL DATA COLLECT ION

On March 19, 2008, the day of the bottled water order , hard facts on up

- to

- the

- minute water quality in the city’s distribution system were scarce. Simple field test kits for chlorine, which may be a quick and meaningful tool for determining area s of poor water quality, could not be applied in a system with no chlorine disinfection. That meant samples needed to be c ollected, transported, and then analyzed in a laboratory setting.

As a result, the SDW program team set out a plan to collect samples and transmit them to the lab as expeditiously as possible. This was no small task due to limited access to comprehensiv e laboratory facilities

, as well as very limited service for speedy or overnight delivery or courier services to other laboratories outside the San Luis Valley. Fortunately, a certified lab in
Alamosa was available to analyz e many of the samples collected ; others required transportation
to the Denver area or out of state. Logistics associated with collecting the samples and transmitting them within required hold times for samples was labor intensive and required significant coordination throughout the out break response

. As discussed above, on March 19, 2008, analytical results from water samples taken earlier in the week were beginning to become available, and one of the results indicated the presence of
total coliform bacteria

. A summary of th e data c ollected during the outbreak is included in Appendix B and a map of selected results is includ ed in Appendix C. The team procured sample equipment specifically for Salmonella from the CDC lab in Atlanta, GA and from the state lab located in Denver. On March 20, 2008, members of the SDW program team were onsite in Alamosa collecting samples to verify the presence of Salmonella in the drinking water. Results reported on March 24, 2008 confirmed the presence of Salmonella throughout the city’s waterSalmonella Outbreak in Alamosa, Colorado, March and April 2008

14 system and confirmed the absence of Salmonella in the East Alamosa water system which was completely separated from Alamosa’s water system at the time of the outbreak

. 1

In addition to water samples, the team also collected samples of animal fecal material on the ground in several locations around the northern part of the city on March 21, 2008. This included the area of the Weber reservoir and parks and open space nearby. Of the s amples, five were most likely from geese, and five were likely from deer. The samples were analyzed in the laboratory and were found to be negative for Salmonella

. The SDW program team did not perform a detailed evaluation of the city’s water system physical infrastructure at the time the initial water and fecal samples were collected ; however

, the Colorado Water/Wastewater Agency Response Network (CoWARN) crews deployed on March 20, 2008 provided support for investigating and responding to deficienci es in the city’s water system.

COWARN AND LOCAL PAR TNERS

CoWARN was called to respond to the Salmonella outbreak in Alamosa on March 19, 2008.
CoWARN was launched in September 2007 and members include public and private water and wastewater utilities, as well as industry support organizations and government partners. The purpose of the CoWARN network is to support water and wastewater utilities’ ability to respond to and recover from emergencies. In an emergency, CoWARN can provide immediate assistance

t o member utilities. The network established for mutual aid was critical to Alamosa's ability, and the SDW program team’s ability, to effectively respond to the situation in Alamosa.

The CoWARN website (www.cowarn.org) provides a forum for establishing a nd maintaining emergency contacts and communicating specialized needs and resources, in real time, in response to emergencies at water and wastewater systems. At 1 p.m. on March 19, 2008, the SDW program team issued a standby notice to all CoWARN members by email and on the CoWARN website. CoWARN members were requested to be on standby for a potential event at a water system in southern Colorado.

Later that day, at 4:30 p.m. on March 19, 2008, CDPHE announced a need for equipment to respond in Alamosa, including a need for tanker trucks, portable water containers and disinfection equipment. Within hours of notifying the CoWARN network of a need for resources, member utilities were starting their response to meet Alamosa’s needs. Within two hours, Denv er Water, Aurora Water, and Fort Collins Utilities had lined up crews, equipment,
water containers and a tanker truck to send to Alamosa.

P articipation in CoWARN is voluntary and there is no obligation to either provide assistance or
receive assistance. I n 2007, when the leadership team of CoWARN was building the framework

1 As a point of clarification, East Alamosa Water District was a separate water system at the time of the outbreak in March and April 2008. It was not connected to the city of Alamosa’s wat er system. That has since changed and at the time of this writing, the city of Alamosa now serves water to East Alamosa.Salmonella Outbreak in Alamosa, Colorado, March and April 2008

15 for the mutual aid network, they established an agreement and protocols for matching resources and needs among water and wastewater utilities statewide, in advance of a real emergency. In the case of Alamosa, without outside assistance, the emergency response would certainly have been delayed and may have taken much longer to complete. One reason for this was that many utilities may have responded more slowly as legal, liability, and re imbursement issues were worked out. With CoWARN’s mutual aid agreement, those issues were addressed in advance.

On March 21, 2008, Alamosa signed the mutual aid agreement, establishing a formal and legal working relationship between the city and other mutual aid partners. Having signed Mutual Aid Agreements in place was critical for quick response and mutual aid be tween Alamosa and other
utilities. CoWARN’s important emergency response role in Alamosa cannot be overstated, and in this report CoWARN is highlighted throughout the discussion of the response following the
bottled water order

. Having the right specializ ed water treatment equipment available was critical to a quick response. Just as important was having access to a network of specialized and certified water treatment operations professionals who were skilled at installing and operating the equipment.
On their own, few water systems have the technical expertise, personnel, equipment and supplies to develop a plan and deploy the resources necessary for disinfection and flushing on the scale of an entire city, and in a short period of time. Because Colorad o has established CoWARN, a mutual aid network for water and wastewater utilities statewide, Alamosa had nearly immediate access to supplies and human resources to assist with the response. With CoWARN, experienced crews from across the state were working with the city within 24 hours. Within 48 hours, equipment, crews, and supplies began arriving onsite to start work.

ALTERNATE WATER SUPP LIES

Throughout the response to the outbreak , the SDW program team fielded multiple requests for
assistance from bus inesses seeking approval or technical assistance to conne ct to an alternate water supply

, and responding to such requests created a significant resource demand. Such
b usinesses included supermarkets and resta urants that depended on a safe source of drinki ng water to prepare and sell food to the community. Without the ability to rely on water provided by the city, businesses sought state approval for alternative sources of water , primarily in the form of bulk delivery of safe water from a reliable source t o onsite tanks and pump systems. Each request was, in essence, a request to form a public water system on an emergency basis. In response to these requests, the SDW team’s engineers and scientists worked as quickly as possible to approve designs and esta blish proper procedures that would ensure the safety of the public and also support businesses staying open to serve the community to the greatest possible

extent.

DECISION TO DISINFEC T AND FLUSH

By Thursday, March 20, 2008, the SDW program team susp ected that Salmonella had contaminated the entire water system in Alamosa. Lab results confirming that was the case were not available until Monday, March 24, 2008, but the team did not delay taking action.Salmonella Outbreak in Alamosa, Colorado, March and April 2008

16 On that Thursday, Denver Water crews from CoWA RN met with the SDW program team at the CDPHE office in Denver, and with Alamosa personnel on the phone, to develop a strategy to disinfect and flush Alamosa’s entire water distribution system with chlorine, including the storage tanks and nearly 50 miles of distribution lines . At the time, it was recognized that this
would be a significant effort and an unprecedented task. Initially the team estimated that the effort may take three to four weeks , or longer, to complete. Of particular concern was the age of
some of the distribution lines in the city and the condition and operability of the valves in the system.

In spite of the challenges ahead, known and unknown, the team decided that any plan to
eliminate Salmonella from the city’s public water system must include a process to systematically and thoroughly disinfect each tank and every foot of distribution line. Various
technical o ptions, and their feasibility and impact on the public als o were considered.

The city provided an electronic version of a map via email illustrating all distribution lines, tanks, water sources, streets and other landmarks. Fortunately, CDPHE had in

- house computing resources to be able to print it out on large scale plotters in Denver for the team to use for planning. Information from the detailed map was critical at the time to understanding the scope and scale of the disinfection and flushing process that was required. The team reviewed the map
and consulte d the American Water Works Association (AWWA) standards for guidance on recommended techniques for disinfection of water mains and water storage facilities

. AWWA
standards C651

- 05 and C652

- 02 were used by the team for planning the disinfection process

. B oth standards reference coliform bacteria as an indicator of bacteriological quality. During the response in Alamosa, it was assumed that a process effective to disinfect water for total coliform would also be effective for disinfecting water for Salmonel la . Follow

- up testing after disinfection of Alamosa’s system confirmed that the process was effective and tests for total
coliform and Salmonella were negative.

In addition to reviewing technical standards, the team also read reports on similar outbreaks of
Salmonella associated with drinking water. The two immediately identified were those in Gideon, Missouri (1993) and in Riverside, California (1965). In the case of Gideon, the outbreak
lasted several weeks , sickening about 650 people

, and result ed in seven deaths. That outbreak was eventually attributed to contamination from a storage tank ; however

, the cause was not identified initially and the Gideon water system was not systematically disinfected and flushed at
the time. The Riverside outbreak sic kened an estimated 1 8 ,000 people and resulted in three deaths. No specific source of contamination was identified. In both cases, the water system was supplied with unchlorinated groundwater. To prevent recurrences of Salmonella and prolonging
the outbr eak, the team confirmed that a complete disinfection of Alamosa’s entire distribution system was the appropriate and conservative operational outbreak response approach

.

AWWA standard C652

- 02 describes three methods for water line disinfection using chlor ine. In Alamosa, the team decided to implement a modified version of the continuous feed method. Under this method, the chlorine dose is 25 milligrams per liter ( mg/L ) for a hold time of 24 hours. At the end of the 24 hour period, the chlorine residual should be no less than 10 mg/L. This approach was intentionally conservative. At the time, the contamination source wasSalmonella Outbreak in Alamosa, Colorado, March and April 2008

17 unknown, and the chlorine demand in the distribution system was unknown, so the team prepared to closely monitor chlorine residual as part of the disinfection and flushing procedures. During the flushing process, water velocity was controlled to reduce the likelihood that the distribution system would be damaged, and minimize disturbance to any biofilms, scale or sediment that may contain high levels of secondary parameters of concern , such as arsenic, lead, and copper.

For water storage facility disinfection, the AWWA standard describes three methods using chlorine. Two of these methods describe filling and holding the tank for a period of 24 hours
with a defined amount of chlorine. Considering the configuration of Alamosa’s distribution system, the team decided to follow a procedure to fill and hold Alamosa’s three storage tanks at a minimum of 25 mg/L of chlorine for 24 hours. This dosage of chlorine exceeded the requirements of t he standard. As in the distribution system line disinfection, the chlorine demand was unknown, so this was a conservative decision. The water held in the tanks was used again to flush the distribution lines with a high level of chlorine. The team monito red the chlorine residual closely throughout the disinfection and flushing process.

A dose of 25 mg/L is on the order of 25 times a typical concentration of chlorine in drinking water, and more than 5 times the concentration recommended for a swimming pool . The federal and state standard for maximum residual chlorine level in drinking water is 4 mg/L. Because the chlorine dose used in Alamosa was so much higher than the maximum drinking water standard, it was critical to communicate to the public when wat er at their tap was not safe for use. The Emergency Operations Center (EOC) in Alamosa (part of the ICS system in place) led this aspect of emergency response.

To simplify communication with the public the EOC developed message s with a traffic signal
th eme. When water was unsafe for use

, the public was notified that the condition was “red

. ” Flyers printed on red paper were distributed door to door by teams of volunteers notifying the public not to use the water. When chlorine levels were lowered to s afer levels for limited use, but the water was not yet safe for drinking, the public was notified that the condition was “yellow

. ” When the water at the tap was finally deemed safe to drink, the condition went to “green

. ” Throughout the process, the pub lic was notified through a coordinated effort by the EOC. The SDW program team assisted this process by recommending and reviewing language to use in the notices distributed to the public.

DISINFECTING AND FLU SHING THE CITY’S WAT ER SYSTEM

On the evening o f March 20, 2008, following the planning meeting held at CDPHE, a team led by Denver Water and coordinated with other CoWARN members began arriving in Alamosa to begin preparing the system for disinfection and flushing. They brought equipment and supplies with them. By the next day, Denver Water crews were in place and working side by side with

c ity and CDPHE personnel. Additional supplies and equipment arrived from Denver Water, Aurora Water, and South Adams County Water and Sanitation District. Meanwh ile, a Fort Collins Utilities tanker truck was taken out of storage, disinfected, tested, and on the road by theSalmonella Outbreak in Alamosa, Colorado, March and April 2008

18 weekend of March 22

- 23, 2008. All of the responding utilities were members of the CoWARN
mutual aid network.

Previously operating under a disinfection waiver, there was no chlorine present in the distribution system, nor was there chlorination equipment installed at the city’s wells at the time of the outbreak. In order to set up a continuous feed of chlorine to the distribution system, the city needed to first set up chlorination equipment. Because a new water treatment plant was under construction, city personnel were able to quickly obtain chemical feed equipment from the new plant site and set up a continuou s sodium hypochlorite feed at the Weber wellhead. CoWARN partners also offered additional supplies, including emergency chlorine feed equipment and chemicals.

STARTING AT THE WEBE R RESERVOIR

The crew of operators from the city along with CoWARN and CDPHE responders started disinfecting the city’s distribution system on Friday, March 21, 2008. The first step was to drain, disinfect, and remove sediment from the city’s Weber reservoir. The Weber well feeds into this ground

- level reservoir, the n a booster p ump system pumps water into the city’s distribution lines.

When the crew entered the reservoir

, they identified some holes in the corners of the reservoir through which daylight could be seen. The holes were patched that weekend . No other holes

were ap parent in the roof ; however

, cracks were visible on the roof and sides of the tank. The crew did not observe any sign of infiltration through the walls or floor once the reservoir was completely drained. Further, the field crew also looked for any eviden ce of birds in the tank

, includ ing droppings or nests

, and none were found.

Cleaning the Weber reservoir and completing repairs continued until Saturday morning, March 22, 2008

. Prior to refilling the reservoir, a chlorination system was set up at the W eber w ell, which is the only water source for the reservoir. The system was designed to inject chlorine into the flow stream at 25 mg/L. Once that was complete, the walls were sprayed with a separately made, high

- chlorine level (50 mg/L) solution and the reservoir was refilled.

Field crews completed the process of filling the reservoir with the 25 mg/L chlorine levels by approximately 5 p.m. local time on Saturday, March 22, 2008. This water remained in the reservoir until approximately 8 a.m. on Monda y, March 24, 2008. Water from the reservoir was periodically sampled for chlorine testing and the chlorine residual remained in the range of 24 to 25mg/L throughout the process. This approach met or exceeded the team’s original disinfection plan in accor dance with the AWWA standard.

On Monday, March 24, 2008, CoWARN posted a need for 10 additional water distribution system operators to assist crews in Alamosa to disinfect and flush the water distribution system. Distribution system operators from Aurora Water were deployed later in the afternoon in response to the request. Dozens of other CoWARN members also began offering experienced personnel, equipment, chemicals, and other resources. At this point in time, the field crews were preparing to begin dis infecting the city’s two elevated towers and then systematically flushingSalmonella Outbreak in Alamosa, Colorado, March and April 2008

19 the city’s 50 miles of distribution line. Appendix A contains a timeline of events around this period.

FLUSHING 50 MILES OF DISTRIBUTION LINE

The process of disinfecting the city’ s system started with introducing high levels of chlorine, on the order of 25 mg/L

, into the distribution system and directing that superchlorinated water to the elevated storage tanks. On Monday, March 24, 2008, the crew began by holding the Craft Tower for 24 hours with a high dose of chlorine, and then the water was flushed from north to south in sectors through the city. The entire city is designed as one pressure zone, so the field crews divided the city into three sectors for operational management of field crews and notification of the public. Figure 2 illustrates these sectors. Flushing progressed through the city from Sector 1, then Sector 2, then Sector 3.

Throughout the week, additional distribution system operators arrived on site from CoWA RN partners and from the State of Nebraska to relieve crews and assist with flushing and sampling operations.

Meanwhile, other CoWARN members coordinated communications from the CDPHE Emergency Operations Center. They were in constant communication with c ity and SDW program team personnel onsite, and they maintained the CoWARN website continuously, including updating needs for specialized equipment and personnel and offers of support. This network of communication was also critical to ensuring the public was notified when chlorine was introduced to the system at levels that were considered unsafe for contact (condition “red”) or for only limited use (condition “yellow”).Salmonella Outbreak in Alamosa, Colorado, March and April 2008

20 FIGURE 3 : SECTORS FOR DISTRIBU TION SYSTEM DISINFEC TION AND FLUSHING (COURTESY O F OLSSON ASSOCIATES)Salmonella Outbreak in Alamosa, Colorado, March and April 2008

21 The high levels of chlorine were a risk not only to the public, but also to the workings of the city’s wastewater treatment facility. Wastewater treatment facilities rely in part on biological activity for treatm ent and a high dose of chlorine would have likely damaged the plant processes.

As phases of flushing continued, additional technical resources, including certified wastewater operator professionals, equipment and supplies, were needed to support staff at the c ity’s wastewater treatment facility. Timely action was needed to ensure that Alamosa's wastewater treatment facility did not experience an upset from the high levels of chlorine in the water . This
was critical to prevent ing potentially serious envi ronmental contamination. Another call for
resources went out to the CoWARN network.

On Thursday, March 27, 2008, Metro Wastewater Reclamation District experts met at the CDPHE office in Denver, with Alamosa, CDPHE, Aurora Water/Reuse, and Pinery Water a nd Wastewater District personnel on the phone, to develop a strategy to address Alamosa’s needs. Later that day, Metro Wastewater crews were deployed to Alamosa with equipment and provided support for the c ity’s wastewater collection and treatment system.

Wastewater treatment professionals from the city and CoWARN partners monitored the sewage inflow for chlorine levels and were prepared to either divert the flow to sludge holding ponds or add sodium bisulfite, if necessary. Both flow diversion and dechl orination techniques were employed during the flushing to ensure that chlorine levels entering the wastewater treatment facility were not elevated. City staff and responders also closely monitored the operation and performance of the wastewater treatment facility. These efforts were successful in avoiding an upset at the wastewater treatment facility. Such an upset would have been a risk to fish and bird habitat in the Rio Grande river, and could have potentially damaged habitat that is a national
wildli fe refuge

. Disinfecting and flushing the city’s distribution system, including three tanks and 50 miles of pipeline took a total of 13 days, from commencing the disinfection of the Weber Reservoir on Friday, March 21, 2008, through Wednesday, April 2, 2008 . This was significantly less than the original estimated time of three to four weeks. Throughout the process, field teams collected water samples citywide to analyze for chlorine levels, bacteria, and other secondary parameters
of concern. These effort s are detailed in the next section. Results from samples collected throughout the city confirming the system was free from bacteria were reported by the lab on Thursday, April 3, 2008. On that date, the SDW program team rescinded the bottled water order and replaced it with a boil water order

.

DATA COLLECTION

– BEFORE LIFTING THE O RDERS

Teams of water professionals conducted extensive water quality sampling throughout the response to the outbreak. The results of this sampling are discussed here in a prim arily qualitative manner. In addition to water quality sampling, two samples also were collected from sediment removed from the Weber reservoir. A summary of water quality data collected is included in this report in Appendix B.Salmonella Outbreak in Alamosa, Colorado, March and April 2008

22 There were several purp oses to the water quality monitoring that was conducted during the outbreak response: to identify the presence of bacteria, including Salmonella ; to track chlorine residuals in the progress of disinfecti ng and flushing the system; and to ensure that secondary water quality problems did not emerge. During the outbreak, the emphasis of the sampling was on the quality of the water provided at the tap. Accordingly, sampling was conducted in order to gain a com prehensive understanding of water quality at customers ’ taps throughout the distribution system. Absent in these sample results are those representative of water directly from the city’s groundwater sources at the wellheads. For purposes of the outbreak investigation, those samples may have proven whether the source of the Salmonella was from the groundwater wells. However, at the time of the outbreak, the cause investigation was secondary to the emergency. Further, the SDW program team determined that the wells were screened hundreds of feet below the surface in a confined artesian aquifer, which was considered at the time a highly unlikely source for Salmonella bacteria. It would have been beneficial to have collected water samples from the wellheads at the time of the outbreak and in hindsight this is a
lesson learned.

BACTERIA

Once the SDW program team was alerted of a potential outbreak on Monday, March 17, 2008, and the public drinking water supply was suspected as the source, the team moved quickly with only limited available staff and equipment. Samples were collected by the city and local health department on March 17, 2008 . L ater in the week two of the SDW program team’s engineers
traveled to Alamosa to collect samples for Salmonella thr oughout the water system. It’s noteworthy to recall that at this time the city’s water supply was not being disinfected.

Nearly all samples throughout the system prior to disinfecting and flushing the system were confirmed to be total coliform negative wi th notable exceptions on March 17, 2008 and March 21, 2008. All samples were negative for E. coli , a type of bacteria commonly used to test for the presence of wastewater.

O n March 17, 2008, one of ten samples collected by the city was total coliform p ositive near the Craft Tower. Of the other nine samples negative for total coliform, there were two other unusual samples that were noted as “turbid” by the laboratory, indicating that the water was cloud y, and not normal, and that pathogens may be presen t.

On the same day, March 17, 2008, four total coliform samples were collected by the county health department, although the results of these were not reported until much later. One of the four was positive for total coliform and the others were negati ve.

Five samples were collected by Denver Water crews on March 21, 2008, and three were total coliform positive: the Weber tank effluent, the Craft Tower effluent, and a sink at the wastewater treatment plant at the far southeast part of town. The posit ive sample s from the Weber Reservoir effluent and Craft Tower effluent are particularly important to gain insight as to where the contamination originated.Salmonella Outbreak in Alamosa, Colorado, March and April 2008

23 The Weber Reservoir is not connected to the distribution system and receives water only from
the W eber w ell, which did not indicate contamination. Th e positive sample from the Weber
Reservoir effluent is a strong indication that the Weber Reservoir was the location where the contamination originated. Further, contaminated water pumped to the distribu tion system from the Weber reservoir probably entered the Craft Tower and caused it to test positive for coliform
bacteria as well. Water from the Craft Tower could not have flowed back into the Weber Reservoir because of the system design, therefore it w as deemed unlikely that the Craft Tower was the original point of contamination.

Samples that were total coliform negative were collected from the Weber well and Cole Park
well

, and near the city’s public works offices. It is particularly noteworthy that the Weber and
Cole Park wells w ere negative because they supplied all the water to the system in early March 2008, while the Weber Reservoir effluent sample was positive for total co liform

. Disinfection and flushing of the system was a sustained effort from Friday, March 21, 2008 through April 2, 2008. As the disinfection and flushing was conducted by field crews, the SDW team continued to sample for total coliform bacteria througho ut the distribution system. As an additional quality check after a sector of the city was disinfected and flushed, the water was
tested for total coliform bacteria and Salmonella . With one exception, these samples resulted in confirmation that the proces s was effective and there was an absence of bacterial contamination
in the water.

The single case of a positive Salmonella sample collected after disinfection and flushing occurred in a sample collected on March 30, 2008 in the business center of the cit y with the
oldest water lines. This sample was positive for Salmonella using a polymerase chain reaction,

or PCR

, analysis, but culture

- negative

. In th e area where the positive sample was collected , the field crews had decided to lower flushing velociti es due to concerns about line and valve integrity. After the single positive Salmonella result was reported by the lab, the field crews returned to that area of town and repeated the disinfection and flushing process. Follow

- up samples all were negative for total coliform and Salmonella , leading to the team’s decision on April 3, 2008 to modify the bottled water order to a boil water order.

Before the boil water order was lifted, the SDW team collected samples across the city. The results of this water q uality sampling proved that water throughout the system was free of
coliform bacteria and Salmonella

, and supported the decision to finally lift the boil water order on April 11, 2008.

CHLORINE RESIDUALS

At the time of the disease outbreak, the city was o perating under a disinfection waiver from the state. The city was not disinfecting the source water and there was no chlorine residual in the distribution system. In the immediate response to the outbreak, chlorination equipment was installed at the city ’s wells so that the entire system could be dosed with a high level of chlorine
and then flushed to eradicate Salmonella from the system.Salmonella Outbreak in Alamosa, Colorado, March and April 2008

24 After the immediate response, the SDW program team required continuous chlorine disinfection of the system from the wells to the extremities. The city has continuously chlorinated its water supply since late

- March 2008

. From the time of the initial response to the outbreak through present day , chlorine residual monitoring has been conducted throughout the city. There were three primary reasons these samples were collected and analyzed. In the initial response, the samples were collected to ensure that a high enough dose of chlorine was consistently applied to sufficiently disinfect the
tanks and distribution lines and ext erminate Salmonella bacteria. Field teams collected samples throughout this process to ensure that target chlorine levels were achieved.

A second reason the samples were collected was to characterize and track the chlorine demand in the system. Because the system had not been continuously and routinely disinfected and flushed prior to the outbreak, it was unknown if the field team would be able to maintain a stable chlorine residual. A stable residual would illustrate that a large and unpredictable chl orine demand did not exist somewhere in the distribution system . High and/or unpredictable demand for chlorine may indicat e ongoing contamination. Stable chlorine residuals would also indicate that the condition of the physical infrastructure itself had a generally stable chlorine demand. Throughout the disinfection and flushing process, the data indicated a negligible chlorine demand, less than 1 mg/L

, during the initial phases of disinfection and flushing and a typical demand less than 0.5 mg/L after m aintaining a residual of 1

- 2 mg/L during routine operations. This addressed the team’s concerns about the potential for ongoing contamination and the stability of the chlorine demand in the city’s distribution system.

The third reason chlorine residuals w ere collected was to ensure that the city maintained sufficient continuous disinfection throughout the distribution system. The city has been successful at maintaining the appropriate level of residual disinfection since the time of the
outbreak to the pr esent.

SECONDARY PARAMETERS OF CONCERN

When the SDW program team made the decision to disinfect and flush the storage tanks and the entire distribution system, there were several immediate concerns about how that process would impact the physical infrastru cture as well as water quality in the system. Accordingly, the water quality sampling conducted around this time was designed to address not only immediate acute bacteriological contamination, but also potential acute and chronic health risk levels of ars enic, lead, copper, and disinfection byproducts. This potential increase in acute or chronic health risks
was considered in the context of consum ing tap water outright and also boiling it before drinking

- thereby potentially concentrating contaminants to some extent, depending on the length of time
the water was boiled.

Samples collected by field crews were generally from residential taps in the city throughout the flushing period. The results of this sampling showed that while arsenic levels increased somewhat, from about 26 micrograms per liter to about 32 micrograms per liter , the increase was
not significant enough to create a concern for the public. R esults of the sampling indicated that none of the secondary parameters

, except arsenic

, exceeded th e relative MCLs or action levelsSalmonella Outbreak in Alamosa, Colorado, March and April 2008

25 set by federal and state regulation. Thus, t he SDW team determined that there was no acute risk associated with levels of secondary parameters.

Due to the nature of the sampling, in theory it is possible that there were brief transient peaks in secondary parameters that were not measured in the field ; however

, there are no data from this period indicat ing that this happened. At the time of the outbreak, the SDW program team had
some awareness of this as an issue ; however

, the SDW team was not able to quantify the impact in the timeframe of an emergency response. Consulting with internal and external technical experts, the team came to a general agreement that high doses of chlorine would potentially release inorganic heavy metal contaminants from distribution system scales and biofilm and it would be important to be cautious about monitoring the distribution system for parameters secondary to the Salmonella contamination.

Based on the results of sampling for secondary parameters, the team determined that the risk to the public from associated chronic or acute health risk was low. This information played into the team’s decision on April 3, 2008, to modify the bottled water order to a boil water order, and again for the decision on April 11, 2008 to finally lift the boil water order and return the community to condition “green”: safe to drink the tap water once again.

STORAGE TANK SEDIMEN T
All three of the city’s water storage tanks contained some amount of sediment at t he bottom a t the time of the outbreak. It’s likely that the sediment was sand from the aquifer formation that was pumped through the well casings and into the city’s water distribution system. Two samples
of sediment were collected from the Weber storage reservoir and analyzed for the presence of
Salmonella bacteria. In accordance with recommendations from the Centers for Disease Control and Prevention, the samples should have been refrigerated immediately and analyzed within 24
hours. This did not occu r with either sample. Further, there are no official chain

- of

- custody records for either sample. A description of the two samples is included here for completeness

. T he sample results for both were negative, but because of sampling methodology, the resu lts are inconclusive.

The first sample was collected d uring the effort to disinfect Weber reservoir on March 21, 2008

. On that date, a Denver Water employee collected a small (approx. 6 oz) jar of sediment from a
bucket of material that was shoveled fro m the east side of the Weber Reservoir, at the access door. The bucket was filled prior to using wash

- down water or disinfecting the tank. The level of water in the tank at the time the sample was collected was approximately six inches.

At the time the sample was collected the team was focused on pressing emergency response priorities and there were no plans in place to have it analyzed for Salmonella or any other parameter for investigative purposes. The sample was not refrigerated and no special hand ling procedures were used. The sample was transferred to a CDPHE employee who transported it to CDPHE offices in Denver on Monday, March 24, 2008. It remained unrefrigerated until April 2, 2008 when the sample was transported to the state lab where it wa s later analyzed for Salmonella and the results were PCR and culture negative.Salmonella Outbreak in Alamosa, Colorado, March and April 2008

26 A second sample of sediment from the Weber Reservoir was collected later, on March 26, 2008, by the Pueblo County Health Department. The sample was collected from the pile of sediment removed from the reservoir and placed outside during the clean

- out. The sample was taken from about 6 to 8 inches from the top of the pile where it was still moist. The sample, which may have represented sludge from the bottom of the tank was co llected and placed in a plastic bag

some time before noon. Reports indicated that sediment was piled on two to three sides of the reservoir and that the sample was described as tarry and black sludge, not sand. The sample did not appear to be soil, but w as discolored sediment. The sample was delivered to the laboratory in Denver on March 27, 2008. The sample results were reported about a week later and were PCR and culture negative for Salmonella

.

PRELIMINARY FIELD IN VESTIGATION

In March and April 2008, the SDW team’s physical and human resources were dedicated primarily to emergency response activities: coordinating and staffing disinfection and flushing of the system ; collecting and transporting field samples ; assisting with bottled water supply
mobili zation efforts ; sampling bulk water from tanker trucks mobilized to Alamosa ; assisting businesses that could develop their own water supplies; and working around the clock to bring the water system back to a safe operating condition. An added complexity t o managing the activities during the initial days of the outbreak was that the emergency response escalated immediately prior to and during the Easter holiday weekend. At all times, protecting public
heal t h was the top priority. Thus, t he preliminary field investigation into the cause , though important, was a secondary or perhaps even tertiary priority at th at time.

Meanwhile, the SDW program team also had the responsibility of maintaining continuous communication with other responders in the ICS eme rgency response system, including serving as a technical expert resource on all drinking water matters. At the time, the team worked with others internal to the department (emergency response staff, epidemiologists, consumer protection specialists, and th e executive director’s office) as well as external interests (e.g. city leadership and public works operational staff, the incident command’s emergency operations center, the National Guard, media representatives, the Governor’s office, EPA , CDC). Much of these communications were successfully coordinated through department emergency response staff, however many of the messages and operational decisions required input and review by the SDW program team’s handful of technical experts who were also managing and coordinating operational and field activities and communications in Alamosa.

Coordination with department emergency response staff was generally successful ; however

, SDW team resources were continuously required as emergency response staff are not tr ained in drinking water system operations. The SDW program team would have benefitted from additional highly qualified human resources to coordinate with the department emergency response staff to ensure that outgoing messages had a high level of technica l review.

The preliminary investigation focused primarily on the city’s storage facilities and potential

cross

- connections in the distribution system. Being at ground level, the Weber reservoir was the most easily accessible to the field crews and SDW p rogram team, so it was the first to beSalmonella Outbreak in Alamosa, Colorado, March and April 2008

27 investigated. The Weber reservoir was clearly in poor condition, with cracking and noticeable
holes in the corners of the concrete structure

. Further, there was significant sediment in the bottom of the tank, 12 to 18 inches deep by some estimates, and the city public works staff had no records or memory of the last time the tank had been disinfected. The city later reported that
the reservoir was last drained and cleaned out in 1984. There were no obvious signs o f animal
habitation inside Weber Reservoir on March 21, 2008 when it was taken out of service and the field crews began repairing and disinfecting it.

On March 28, 2008, a SDW program representative observed the repaired reservoir and the surrounding are a within a security fence bordering the site. At that time, there were no readily

observable signs of animal presence inside the fence, including animal feces. There were no bird droppings around or on top of the reservoir and no nests or bird droppings inside the pump house. The door to the pump house had been left continuously open for much of the previous week. On March 28, 2008, this individual did discover a “clump” of three large feathers about 2.5 inches long with three smaller ( about one

- inch lo ng ) feathers attached to them inside the pump house

. The lab was unable to analyze the feathers for Salmonella . However

, the feathers are a sign that animals may have spent some amount of time inside the fence surrounding the
Weber Reservoir or inside t he pump house itself.

The other two storage facilities were also a focus of preliminary investigation in March and April 2008. CDPHE imposed a requirement for the city to retain a professional tank inspection firm to inspect the Ross Tower and the Craft T ower prior to lifting the boil water order. The inspectors identified some deficiencies that were repaired at the time.

The Ross Tower, a 150,000 gallon cylindrical shaped tower located near the center of the city

, is the older of the two. The inspectio n on April 2, 2008 showed that the tank had a significant amount of sediment at the bottom and the inspectors recommended that the sediment be removed from the tank. The tower also needed a new hatch and there were minor deficiencies in places at
the seam s and in the tank vent. The tank did have missing bolts, and there were signs that bird feces could have flushed into the tank during a storm event ; however

, bird feces samples collected at the tank were negative for Salmonella

. The tank also required a high pressure wash and the application of an anti

- fungal solution and a bird repellant coating. The city entered into a contract on April 7, 2008 with the tank inspection firm to correct these and other safety

- related deficiencies. It is noteworthy that the inspectors did observe some bird fecal matter on top of the tank, but they did not discover nests or other signs of ongoing habitation.

The newest of the city’s storage facilities is the Craft Tower, a 500,000 gallon spheroid shaped
tank located on the north side of the city. This tank also was inspected by a professional tank inspection firm on April 2, 2008. The Craft Tower was in better condition than the Ross Tower. The inspector noted that this tank also had a significant amount of sediment at the bottom and recommended that it be drained and flushed to remove sediment. As with the Ross Tower, inspectors did observe some bird fecal matter on top of the tank, but they did not discover nests or other signs of ongoing habitation. The inspectors r ecommended a high pressure wash and the application of an anti

- fungal solution and a bird repellant coating and minor repairs to the roof vent. The city entered into a contract to replace the vent on the Craft Tower.Salmonella Outbreak in Alamosa, Colorado, March and April 2008

28 Concurrent with the emergency respon se and the inspection and repair of the city’s three storage facilities, a team from CoWARN assisted the city with assessing the distribution system for potentially hazardous cross

- connections. The city was not in compliance with state regulations requiri ng cross

- connection control in the public water system. The assessment and subsequent site inspections in March and April 2008 identified three locations in the city where a potentially

extreme hazard cross

- connection existed. Two were mortuary facilitie s, and one was a combined meat packing and restaurant property. Reduced pressure zone devices designed to prevent cross

connections were installed by April 8, 2008 at these extreme hazard locations. Over 100 other
sites around the city were noted as taps with potential cross

- connections as well, but they were
not deemed to be a n extreme risk at the time.

None of the three potentially extreme hazard cross

- connection locations in the system appeared
to be a source of Salmonella contamination that caused th e outbreak, primarily because there was
no clear source of Salmonella at the sites. The meat

- packing facility was not a slaughterhouse; packaged meats were trucked in for processing. The mortuaries had no clearly unsafe conditions. Further, there was no evidence at the time of a previous low

- pressure event in the distribution system that may have created a backflow condition. Later analyses of system flows since the outbreak also did not clearly indicate that a backflow event had occurred around that
ti me.

BACK TO THE NEW NORM AL

On Thursday, April 3, 2008, the SDW program team modified the bottled water order to a boil water order as the Alamosa water system was preparing to return to normal. Since the start of the response two and a half weeks earlier , three tanks and 50 miles of distribution lines had been
disinfected and flushed to destroy bacteria. Water samples had been analyzed for bacteria and secondary parameters to ensure that the acute and chronic risk to the public was attenuated.
Chlorine levels were lowered into the high end of the standard range for drinking water supplies (one to two mg/L) . The city, CoWARN crews, and contractors were working to repair the city’s
infrastructure. Alamosa residents were eager to leave “red” and “yellow” behind and go to condition “green

, ” announcing that the city’s tap water was safe to drink once again.

GOING TO GREEN

The letter from CDPHE issuing the boil water order on Thur s day, April 3, 2008 contained a list of activities the city was required to comp lete prior to the order being lifted. This included a written response from the city including information on data collected, a narrative of disinfection and flushing operations and certification that certain system repairs to the water storage tanks

were completed , and high

- hazard cross connections were appropriately addressed

. CDPHE also had decided to wait to finally lift the boil water order until all water system samples collected were analyzed by the laboratories and the results proved that the wate r was safe. Meanwhile, field crews from CoWARN and CDPHE returned home after having worked 24 hours a day to bring the system back to normal. The SDW program team assembled documentation, debriefed with field staff, communicated through the ICS on progre ss, and prepared for the administrativeSalmonella Outbreak in Alamosa, Colorado, March and April 2008

29 task of finally lifting the order. These efforts continued through the weekend of April 5 and 6, 2008. The SDW program team and department leadership readied to lift the boil water order early the next week, nearl y three weeks after the original bottled water order was issued.

GIARDIA AND CRYPTOSP ORIDIUM ANALYSES

As the SDW program team was preparing to lift the order, a representative from EPA Region
VIII learned via the federal ICS communications structure that the CDC in Atlanta had discovered some evidence of Giardia and Cryptosporidium DNA in water samples collected in Alamosa on March 20, 2008, the week before the system was disinfected and flushed. During a telephone convers a tion with SDW program leadershi p , the EPA official communicate d this new
information. These pathogens, typically found in river water, leaks, or shallow wells, can also cause severe gastrointestinal illness. No one from CDPHE had previously heard this news due to
a failure to communic ate between the responding organizations. Although CDC had been aware of the results for at least a week prior, CDC staff in Atlanta apparently did not contact CDPHE directly because of the way ICS structure at the federal level dictates the pathway for s uch
communications.

On Tuesday, April 8, 2008, the news from CDC created a new crisis for the SDW program team, for several reasons. First, this immediately delayed plans to lift the boil water order, with the impacts rippling through the entire ICS networ k. Secondly, chlorine is not as effective against Giardia and Cryptosporidium cysts as it is against bacteria like coliform and Salmonella

. Chlorine can kill bacteria outright. Cysts typically need to be either filtered out of water to remove them, or a lternat iv ely given a significantly higher dose of chlorine or an alternate
disinfectant. This immediately changed the way the SDW program team saw the problem of disinfecting the city’s distribution system. Third, the sources of Giardia and Cryptosporidi um can be very different from Salmonella . Their presence would change the focus of the investigation and create a much broader set of possible causes. Also , but not least important, is that detection of Giardia and Cryptosporidium cysts in water requires complex sampling apparatus and time

- intensive and specialized analytical procedures that only are performed by a few laboratories. In order to confirm that the system was free from Giardia and Cryptosporidium contamination, additional testing would be req uired. Consequently, the SDW program team made the decision to conduct Microscopic Particulate Analysis (MPA) on water samples from the city’s distribution system with the intent to rule out the possibility of viable Giardia or Cryptosporidium pathogens in the city’s public water system.

Because field crews had returned home, taking their equipment with them, there was once again a scramble for resources. Late in the afternoon on Tuesday, April 8 , 2008, SDW program staff contacted CH Diagnostic in Berthoud , Colorado, one of the labs in Colorado that performs MPA analyses, to obtain equipment. Engineers from the CDPHE office in Pueblo prepared for another unanticipated field event. This was a significant change in momentum for all the responders involved, just as all were preparing to close out the boil water order and return the city to normal.

Part of the challenge with the rush to conduct MPA analyses was the distance between Alamosa and Berthoud, Colorado

, nearly 300 miles. In both locations there was also very limitedSalmonella Outbreak in Alamosa, Colorado, March and April 2008

30 overnight pick

- up and delivery service. T he CH Diagnostic staff packed MPA test equipment i n time for the last overnight deli very drop

- off of the day at 5 p.m. , Tuesday, April 8, 2008 for next morning delivery in Pueblo, Colorado. CH D iagnostic also made a commitment to rush analyses as fast as possible once they received samples, so they modified their operations accordingly.

In the meantime, the SDW team in Denver and Pueblo worked with Alamosa public work s staff to organize the fie ld activities that needed to happen the next day. On Wednesday April 9, 2008, the equipment from CH Diagnostic arrived in Pueblo. At that time, two of the SDW program engineers traveled from Pueblo to Alamosa with plans to conduct the MPA test procedure at locations around Alamosa’s distribution system.

The MPA test requires a certain volume of water to flow through a special 1

- micron absolute filter for a period of time. The field team quickly realized that the runtime for the tests in the
field would be the primary factor in how quickly the results would be available. With the city still under a boil water order, there was pressure for results as soon as possible. On Wednesday, the team changed course and instead of running the filtration step of the MPA procedure in the field per normal procedure, an alternate procedure was used. Th at alternate procedure

, recommended by CH Diagnostic , required field crews to collect bulk water samples in 7

- gallon
containers and then transport them to Berthoud for fi ltration in the lab.

The 300 mile distance again became a logistical issue. The bulk samples were collected throughout the day on Wednesday, April 9, 2008. In order to get them to the lab the next day there were two options: fly the samples out of Alam osa’s regional airport or drive them that night for early morning delivery on Thursday. The team chose the latter, with one crew driving them from Alamosa to Denver, then transferring them in the middle of the night to another vehicle. A
second driver wa s on standby and drove the second leg to the lab in Berthoud.

On T hursday, April 10, 2008, and Friday, April 11, 2008, CH Diagnostic in Berthoud analyzed all bulk water samples from Alamosa and found no Giardia or Cryptosporidium cysts. While a typical turnaround time for this type of analysis is two to three weeks , w ith a rush order the
results were available within two days. With evidence confirming the absence of Giardia and Cryptosporidium, the team made the decision to lift the boil water order.

On further review, the CDC later reported that samples in question showed only generally weak signals from a DNA analysis of the March 20, 2008 water samples in Alamosa. They did not clearly identify that viable Giardia or Cryptosporidium cysts wer e in fact present; the results simply suggested that some segment of DNA associated with one of those types of organisms may have existed in the sample s

. This kind of analysis was essentially experimental, and it

cannot be conclude d that the system was re cently, or ever, truly contaminated with viable
Giardia or C ryptosporidium cysts.

In addition, the epidemiological data did not suggest waterborne transmission of either Cryptosporidium or Giardia. No cases of Cryptosporidium were reported during the ou tbreak time frame. Three cases of Giardia were reported; however, it was determined that they were unlikely to be related to the city’s drinking water.Salmonella Outbreak in Alamosa, Colorado, March and April 2008

31 In summary, a lthough these results spurred a necessary and tremendous effort to assure public
health protection before the boil water order was lifted, these results are essentially inconclusive with respect to the cause investigation.

LIFTING THE ORDER

– WITH CONDITIONS

By Friday, April 11, 2008 the city had completed all the requirements outlined in the letter sent by CDPHE on April 3, 2008 issuing the boil water order. All follow

- up sampling was complete, confirming that the water was safe to drink. CDPHE rescinded the boil water order by letter on April 11, 2008. The public was notified that the condition was “green” and it was again safe to drink tap water in the city ; the mayor donned a green shirt to celebrate the occasion

. The April 11, 2008 letter lifting the boil water order included a num ber of conditions mandating the city to take additional actions to repair the city’s Ross Tower and to plan for additional repairs to both the Ross Tower and Craft Tower. Additionally, the Weber Reservoir was permanently disconnected from Alamosa’s drinki ng water system. While this letter marked the end of the boil water order, it was only one milestone in continuing efforts for the city and SDW program staff to work together to investigate the cause of the outbreak and to ensure that additional improveme nts to the city’s public water system were made.Salmonella Outbreak in Alamosa, Colorado, March and April 2008

32 

### PART III: POST

- CRISIS

AFTER THE EMERGENCY: APRIL

- OCTOBER 2008

On April 11, 2008, the public was notified that the boil water order for the c ity of Alamosa had been lifted and that it was once again safe to drink water from the tap. Thus ended the response for many of those working with the city through the outbreak. The Incident Command System teams stood down, the CoWARN responders returned to their own communities, and many of
the CDPHE staff and leaders hip were attempting to return to normal routines. For the SDW program, however, there still was an ongoing investigation into the cause, regulatory obligations to meet, and ongoing work with the city regarding repairs to the city’s physical infrastructure and start up of the new centralized water treatment plant.

This section covers activities conducted by the SDW program from the time the boil water order was lifted in April 2008 through the issuance of a formal Enforcement Order by CDPHE to the city in O ctober 2008. This includes efforts to investigate the cause of the outbreak and to finalize the terms and conditions for regulatory enforcement that would ensure drinking water provided to the public by Alamosa’s public water system would continue to be s afe.

SCOPE OF THE INVESTI GATION

In order for bacteria to enter Alamosa’s drinking water system, it would have had to come from a failure in the integrity of the city’s water sources, storage facilities, or distribution lines in such a manner and at the rig ht place and time for bacteria to enter the system. Accordingly, the investigation work that commenced in April attempted to identify all potential sources of the bacteria, and all potential integrity failures by which bacteria could enter city’s water sy stem.

One initial clue came from laboratory testing that indicated that the serotype and pulsed

- field gel electrophoresis (PFGE) pattern of Salmonella associated with the outbreak was rare. This rare pattern matched samples from the Alamosa drinking water and affected patients during the
outbreak confirm ing drinking water as the source of exposure to Salmonella . According to data from the CDC national reporting database

, PulseNet, before the outbreak this serotype and PFGE pattern had been identified 31 t imes in Colorado starting in 2000 when 12 cases were identified
around the state. One of the 12 cases was a child from Alamosa whose source of infection was
not identified. In the United States this serotype and PFGE pattern has been primarily reported
f rom patients in Colorado, Wyoming and Texas. Seven non

- human specimens were identified in a national database during the period 2005

- 2008 from Wyoming and Oregon. Four were from birds, one a mule deer, one feline, and one unknown. This information confi rms the likelihood of the particular strain of Salmonella existing in the natural environment in the western United
States. This also indicates that there was likely a single source of contamination into Alamosa’s water system, as opposed to multiple sour ces.

Based on initial response and investigation work, there was no indication that deliberate and malicious tampering with the city’s water system was the cause of the Salmonella contamination

.Salmonella Outbreak in Alamosa, Colorado, March and April 2008

33 This was reported by responders in the field and also throug h the NIMS Incident Command System teams. Absent other compelling evidence, the SDW program team proceeded with the investigation with an understanding that the contamination was not intentional

. Thus, from April through October 2008 the team formulated a draft scope of work for the disease outbreak investigation that became an attachment to the formal Enforcement Order in October 2008. The scope of work identified a listing of all potential integrity failures at the wells, storage facilities, and distribu tion lines, possible causes of such failures, and the need for a more complete literature review of other similar outbreaks worldwide. The next section of this report details the accomplishments associated with the scope of work and the conclusion of the investigation.

ENFORCEMENT ORDER ON CONSENT

On October 10, 2008, CDPHE signed an Enforcement Order on Consent (“consent agreement”)
for violations related to the Salmonella outbreak. The requirements of the consent agreement
were discussed between CDP HE and the city and were agreed upon in advance. The consent agreement clarified outstanding requirements and ongoing expectations as they related to the
Salmonella outbreak and Alamosa’s operation of its public water system. Requirements
included: conti nuous chlorination of the well sources, ongoing monitoring of water quality in the distribution system, cooperation with CDPHE on the investigation into the cause of the outbreak,
and submittal of other technical and administrative documentation.

The con sent agreement issued by CDPHE served several purposes. First, as the primacy agency for ensuring compliance with federal drinking water regulations and standards, CDPHE was obligated to proceed with appropriate enforcement actions toward the city. The a greement fulfilled that obligation. Secondly, the agreement outlined a course of operations and water quality monitoring to ensure that drinking water in Alamosa would continue to be as safe as possible following the outbreak. Third, the city agreed to p rovide requested information, documentation, data, and performance of work necessary to complete the outbreak investigation. Following the issuance of the Enforcement Order on Consent in October, the SDW program’s next priority was concluding the investig ation into the cause of the Salmonella outbreak. The city of Alamosa has cooperated with this investigation. As of this writing, the city’s efforts to gain full compliance with cross connection control requirements continue.Salmonella Outbreak in Alamosa, Colorado, March and April 2008

34 CONDUCTING THE INVES TIGAT ION

The documented scope of work for the disease outbreak investigation was included in the consent agreement . The SDW program team has systematically proceeded with the investigation based on this scope, expanding on certain aspects where appropriate.

WATER SYSTEM FACILIT IES AND FLOWS

In March 2008, the city had seven active wells, three water storage facilities, and 50 miles of distribution line. Figure 1 illustrates the location of these facilities as of March 2008. As part of the investigation into the cause of the Salmonella outbr eak, the SDW program team gathered and evaluated operational records, statements from the city, and available data about the water system.

WELLS

Of the city’s seven wells used as drinking water sources, only three were used to supply drinking
water from ea rly February 200 8 prior to the disease outbreak. On average during that time, the Weber well supplied 75 to 80 percent of the water for the city, with about 15 to 20 percent pumped from the Cole Park and less than 5 percent on average from the 12 th Street well.

The Weber well pumped directly into the Weber storage reservoir through a perforated header along the roof of the reservoir. The header was designed to aerate the well water and remove hydrogen sulfide gas . From the Weber reservoir, water was pumped again directly into the distribution system. The Cole Park well and 12 th Street well pumped directly into the distribution system with no storage reservoir.

According to documentation submitted to CDPHE by the city, no significant repairs or

m aintenance work was done on any of the wells connected to the city’s potable water system in the year prior to the outbreak. In 2006, there was some work on the 12 th Street and 20 th Street well pumps.

The city was able to provide l imited well construction details for the wells. Based on the information available, the well permits were issued between 1963 and 1983. Records also appear to indicate that original well construction was as early as 1936 for the Cole Park well and
1956 for the Weber well.

In general, the city’s wells have some grouting near the surface, and are cased with solid casing
to 500 to 900 feet below the surface. A fter that depth segments of perforated casing exist to depths 900 to 1

, 800 ft , depending on the well . The city’s wells a ll flow under artesian pressure and are designed and constructed to draw water from deep confined aquifers.

While it is not noted clearly on the well construction logs or related documentation, each of the wells does penetrate very shallow groundwater in a n unconfined aquifer. The Rio Grande flows along the eastern border of the city and all the wells penetrate shallow alluvium near the riverSalmonella Outbreak in Alamosa, Colorado, March and April 2008

35 banks. The Weber well and Cole Park well both are near shallow wetlands areas that are riparian
habitat. Neither well is designed or constructed to draw flow from shallow groundwater.

The city has stated that no repairs or replacement s were recently conducted on any of the well casings. The SDW program team was able to review videos captured by professional well
ins pectors for the Cole Park and Weber wells. These two wells provided most of the water supply for the city at the time of the outbreak. Two videos were reviewed for the Weber well, one from 1996 and one from 2009. A comparison of these videos illustrates that the Weber well casing has significant corrosion which appears to have worsened from 1996 to 200 9 . The Weber well has several areas of concern, especially at depths up to 300 feet ; however

, it is unclear to what extent the casing has been damaged to allow contamination to enter into the well. The Weber well also appears to have two lines penetrating the well casing at a few feet below the top of the well casing. Based on interviews with city personnel, it is believed that these are overflow
lines t hat meet in a common header controlled by a single valve , then daylight to a nearby vault

. A visual inspection of the vault in July 2009 showed that there was no flap valve or cover on the
end of the overflow line. The videos of the Weber well also illus trate an offset and clear discontinuity in the casing at about 950 feet that has been present since at least 1996. By comparison, a review of a video from 2001 illustrates that the casing of the Cole Park well appears to be in generally good condition. Other than the videos, detailed reports from the professional well inspectors are not available for either well.

In 2004, the SDW program published reports for over 1

, 700 public water systems statewide as part of a source water assessment and protectio n project. Six of the city of Alamosa’s wells were assessed at the time and the city received a report on the susceptibility of these wells to different potential sources of contamination, including underground storage tanks, septic systems, known
waste d isposal sites, and others. A rating of total susceptibility was calculated for each source
based on a computer model that considered a combination of proximity to a potential source of contamination and the magnitude of the threat of that source. Develop ment of the ratings did not
include an onsite review. Five of the six wells were determined to have low or moderate susceptibility to contamination. The Cole Park well was the only one to have a high total susceptibility rating. This was based on the pr esence of two nearby industrial facilities and six tank facilities. The wells in service at the time of the outbreak were not associated with a high risk of bacteriological contamination that would indicate a high likelihood that Salmonella
contamination occurred at the wells.

In addition to the potable public water system, the city also maintains a non

- potable water system used for irrigation. Prior to the Salmonella outbreak, the only dedicated non

- potable system was the irrigation system for half of th e city’s golf course. According to statements provided by the city, this non

- potable system is not connected with the potable system in any way. The non

potable system has its own dedicated water source.Salmonella Outbreak in Alamosa, Colorado, March and April 2008

36 TANK OPERATIONS

At the time of the outbreak, th e city was operating two elevated storage tanks, the Ross and Craft towers, and one surface level storage reservoir, the Weber reservoir. The SDW program team reviewed tank level data for February and early March 2008 for both elevated tanks to determine whether any unusual conditions appear ed to exist during that time period. Specifically, the team looked for evidence of unusual pressure drops or patterns in tank drawdown and fill cycles that were out of the ordinary.

Based on a review of the data, only minor differences in routine operations on two days during that time period were noted: February 12, 2008 and February 20, 2008. On February 12, there was an unusual drop in the level of both the Ross and Craft towers, indicating the possibility of a
chan ge in system pressure that was out of the ordinary. The data seem to indicate that both the Ross and Craft tanks had a level drop around 2 p.m. It took a pproximately one day to return to the normal diurnal pattern of tank levels. Similarly, on February 20, the Ross tower experienced a drop in tank level of several feet during an otherwise normal fill pattern for that time of day. Concurrent with the Ross tower level drop was a smaller level drop at the Craft tower that registered about the same time. Th is also possibly indicated a change in system pressure that was not in the normal pattern.

According to a statement from the city’s water superintendent, operational conditions on both dates coincided with work being performed at the new water treatment pl ant. On February 12, the city’s contractor needed water to fill and test the clearwell on the new treatment plant. According to the city’s statement, the contractor opened the valve “too fast

, ” then subsequently
continued to fill the clearwell at a slowe r rate. A bout 225,000 to 250,000 gallons w ere used to fill the clearwell. On February 20, there was another smaller draw of water to top off the
clearwell.

To better understand the nature of flows in the city’s distribution system during the weeks
lea ding up to the outbreak, the SDW program retained an engineering consulting firm to create a computer model of the city’s water system. Through that work, it was determined that it was unlikely that the increased demand placed on the system at the time th ey filled the clearwell significantly impacted the distribution system pressure. The modeling work estimated that the clearwell was filled with a volume of 225,000 gallons and the Craft and Ross towers had a combined volume of approximately 694,000 gallon s. By filling the clearwell, approximately 32 percent of the volume of the two towers was used (if they were both full at the time of use). The
withdrawal should n o t have been enough to cause adverse system pressures that would potentially draw contamina tion into the system, but it would make the wells pump more frequently to fill the towers.

Further, according to a written statement

, the city’s opinion was that all operations data w ere normal for th at time of year. They stated that there were no data sh owing any significant pressure drops, unusual pumping patterns, or any data supporting unusually long detention times in any of the storage facilities that would indicate a problem with the operation of the potable water system. The most recent leak repai r reported by the city was a tap blown off in the Price neighborhood on the east side of the river

. Leak repair did not have a significant impact onSalmonella Outbreak in Alamosa, Colorado, March and April 2008

37 pressures within that neighborhood, or anywhere else in the distribution system , and occurred at
least a m onth prior to the outbreak

. In summary, based on a review of the tank level data and correspondence from the city, tank operations in the city were generally under normal operating conditions for the time of year, with the exception of the dates th at the clearwell was being filled at the new water treatment plant. Even under those relatively unusual conditions, it was concluded that the pattern of operations in the distribution system was unrelated to the disease outbreak.

WATER QUALITY DATA B EF ORE THE OUTBREAK

As a public water system, the c ity of Alamosa is governed by the Colorado Primary Drinking Water Regulations and accordingly monitors certain water quality parameters for regulatory compliance. In addition to those required by regulatory mandate, there are other related data that have been collected over the years that characterize the quality of the city’s water.

In general, the city has historically been in compliance with all health

- based state and federal standards, with the exception of the arsenic maximum contaminant level. Due to naturally occurring arsenic in the well sources, the city was in violation of the arsenic standard. A centralized treatment facility, consisting of flocculation, microfiltration and disinfection, had
been in the planning stages for several years prior to the outbreak. It went online in a full service capacity in October 2008, and since that time the city has continually met the arsenic standard for compliance with state and federal drinking water regulatio ns.

Salmonella rare ly occurs in drinking water, and accordingly there is no infrastructure, physical, regulatory or human, established to monitor for Salmonella in drinking water on a routine basis

. Other pathogens much more common in drinking water, incl uding Giardia

, C ryptosporidium,
E.coli , are monitored directly or by surrogate to verify water is not contaminated. In general, the total coliform laboratory analysis is used as a surrogate to monitor risk to public health associated with bacteriological quality of drinking water. Total coliform results are reported as either present/positive (presence of bacteria) or absent/negative (absence of bacteria).

As part of this investigation, the SDW program team reviewed data submitted for compliance
with th e T otal C oliform R ule since 2001. Prior to this outbreak, the c ity of Alamosa ’s water system operated for several years without significant bacteriological violations, or noteworthy historical patterns of total coliform present test results. In accordance with the federal Total Coliform Rule, Colorado regulations require Alamosa to collect 10 samples per month for total coliform bacteria in the distribution system, and the samples were not supposed to be collected on just one day during the mo nth. According to state records, one sample collected in June 2002, one from August 2002, four from November 2002

, and one from July 2003 tested positive for total coliform. None of the required repeat sampling resulted in additional positive results

. N one of these instances resulted in a violation of the Total Coliform Rule, with the exception of
November 2002. In November 2002, the city was issued a non

- acute MCL violation becauseSalmonella Outbreak in Alamosa, Colorado, March and April 2008

38 fours samples were positive for bacteria. As recently as early March 2 008, city water was tested and reported absent for total coliform.

While a pattern of violations related to the presence of total coliform bacteria did not exist, a post

- outbreak review of reported data indicate s that samples were generally taken at entr y points to the distribution system at six of the city’s wells , and the Weber Reservoir effluent . Also, samples generally were all taken on the same day, with two samples collected simultaneously at
some locations. Th is sampling method is not in compliance with the Total Coliform Rule

. Only occasionally were other locations representative of water in the distribution system sampled. Of particular significance, the 10 total coliform samples collected on March 5, 2008 for regulatory complianc e immediately prior to the identification of the outbreak all were taken from the city’s wells in this manner, with the exception of one sample collected from the Weber Reservoir effluent. All of the samples from that day were negative for total coliform.

While a report prepared by SDW program staff documenting the city's August 2007 sanitary survey stated that Alamosa’s m onitoring plan was acceptable, the plan, did not specifically identify the Total Coliform R ule sampling locations . Although the city ha s since conf o rmed their sampling procedures to the requirements of the Total Coliform Rule, the historical data showing compliance are in fact inconclusive. Although not required for regulatory monitoring,
other data were reviewed by the SDW program to ch aracterize the city’s water prior to March 2008. There are a few noteworthy attributes that make the city’s water unusual. First, water
from the well s has a relatively high temperature. As the water flows from the deep wells, the average temperature is generally above 75 degrees Fahrenheit. Secondly, the wells are also high in hydrogen sulfide gas , which creates aesthetic problems related to taste and odor. Third ly

, the
wells have relatively high dissolved silica content. Silica is not typically a majo r concern related to drinking water quality ; however

, it can impact the treatability of water through certain processes. For Alamosa, the high silica levels were a driving factor behind the process selection for the new centralized water treatment plant.

As part of the investigation, the SDW program also requested and received a statement from the city describing any customer complaints received during the period January through March 2008. The city stated that virtually all of their service calls during the period came in January and were related to frozen water services lines and/or meters. The city did get more of these
service calls than normal in January because of prolonged cold weather in that month. The city reported no other apparent patterns of complaints during that time. According to the city, this was similar to what happened during a similar cold spell pattern that occurr ed in December 2006.Salmonella Outbreak in Alamosa, Colorado, March and April 2008

39 STORAGE FACILITIES

– WEBER, CRAFT, AND RO SS

As part of the investigation into the outbreak, a review of design, operation, and maintenance of the city’s three water storage facilities was conducted. The following is an overview of each of
the facilities.

WEBER RESERVOIR

The Weber Reservoir is a 320,000 gallon rectangular concrete reservoir, a portion of which is constructed below grade, with a berm constructed to near the top. Approval of the design and
construction of the reser voir was issued by CDPHE in 1979 and it was constructed in the same year. The most recent inspection of the reservoir was in 1997 by a professional inspection firm. According to the July 9, 1997 inspection report, the reservoir’s roof, exterior wall surf ace and foundation were in satisfactory condition; however the inspector noted that the exterior corners were in poor condition and the exterior walls and foundation had some cracking, spalling, and exposed aggregate. The same inspection report also indic ated that the interior condition of the tank was generally good, with minor exposed aggregate and sediment an average of one inch deep on the floor of the reservoir. The only specific recommendations made by the inspector at
the time were to clean the res ervoir and inspect it every three to five years. There is no evidence that the recommendation to routinely clean and inspect the reservoir was addressed by the city in subsequent years.

The Weber well pumps water into the reservoir through a perforate d header that begins in the

east end of the reservoir and runs to the west for over half of the roof length. The water flows out of the header and falls to the water surface below, creating some aeration to reduce levels of naturally occurring hydrogen su lfide gas . Water is pumped out of the reservoir through a pipe
about 12 inches from the bottom of the east side of the tank.

In 2006, city personnel conducted a visual inspection and the city’s engineering consultant also performed a cursory inspection. No significant structural issues were identified at the time, and the decision was made for the tank to remain in service as part of the potable system until the

start

- up of the new water treatment plant. Then, the tank would continue to serve as a non

p otable water reservoir, as it continues to do today.

The most recent sanitary surveys conducted by SDW program engineers were in 1999, 2002, and
2007. Federal regulations regarding sanitary surveys did not require that storage tanks or distributions syst ems be covered by sanitary surveys prior to December 1, 2009; however, Colorado requirements did include these elements. Prior to the Alamosa outbreak, due to its personnel limitations, the SDW program focused primarily on treatment issues during sanitary

surveys

. The Weber Reservoir was not included in the facility inventory database at the time of the Alamosa sanitary survey in 2007. The person conducting the survey did observe the Weber well, which is adjacent to the Weber Reservoir. A thorough inspe ction of the Weber Reservoir did not take place. However, the general condition of the Weber Reservoir was discussed with the system operator, as was the fact that the reservoir was slated to be taken off line when theSalmonella Outbreak in Alamosa, Colorado, March and April 2008

40 new treatment system became operatio nal in 2008. N o deficiencies associated with the Weber
Reservoir were reported in any of the surveys

. In response to a question relating to the hydraulic configuration of the tank, inlet and outlet piping, and the potential for any cross

- connection
betwe en potable and non

- potable water at this location, the city provided a written statement explaining that there is a 4

- inch drain line at the bottom of the reservoir that runs to a manhole with an air gap and which continues by gravity to the city’s storm d rainage system. The line enters the manhole and bends at a 90 degree angle vertically creating a 4

- foot air gap. The water spills from the top of the outlet to the bottom of the manhole and enters an 8

- inch gravity line connecting to the storm water coll ection system. There is a valve between the reservoir and the manhole to control the drainage from the reservoir

, which is normally in a close d position.

According to the city, in order for a cross

- connection to occur, the valve between the reservoir

an d the manhole would have to be opened and the drain line leaving the manhole would have to be blocked in some way to allow the manhole to fill with water to the top of the air gap. Should this happen, water would almost certainly spill over the top of the manhole due to pressures generated by the head in the reservoir, and the levels in the reservoir would drop to equalize the pressure. Neither of these events occurred in the past year, or previously based on existing records and experience of the city’s operations staff. In the city’s statement, it was noted that it is theoretically possible for a cross

- connection to occur, but they have no reason to believe that one did during the time period in question.

T he city also provided a written statement that there were no significant construction activities near the Weber Reservoir in March 2008. Bresnan Communications did replace one of their cables just south of the reservoir in that time period. The city inspected their work during
construction and it did not impact the reservoir or the lines leading to or from it.

Th e Weber reservoir was drained on March 21, 2008 as part of the initial response to the outbreak. There are no plans to return it to service as part of the city’s potable system. However, the city’s long

- term water system plan prior to the outbreak was to remove the reservoir from potable service when the new water treatment plant went online, and to use the reservoir to store water for irrigation. The city began using the reservoir in that c apacity beginning with the irrigation season in spring 2009.

The Weber reservoir was in poor condition and poorly maintained for a number of years. Of all the potential sources of Salmonella contamination, it seems most likely that contamination may have entered t he Weber reservoir. This could have occurred due to fecal matter that was carried through rain or snowmelt through cracks in the roof and sides of the tank. Another possibility is that small animals, such as birds or small mammals entered into t he tank through one of the larger holes.

It is believed that the tank was relatively warm during cold winter months due to the naturally
warm water from the Weber well and vented warm air through the holes , making it an attractive
location for wildlife to gather. During January 2009 members of the SDW program team observed numerous footprints from small animals in the snow inside the fence surrounding the reservoir, confirming the presence of wildlife inside the fence. According to interviews with citySalmonella Outbreak in Alamosa, Colorado, March and April 2008

41 personnel, small mammals such as rabbits were sometimes seen in the area near the reservoir. In July 2009, another inspection of the Weber reservoir by the SDW program team showed that the
tank still had some cracks in the concrete structure and bird fec es were observed on the top of the
tank including one of the repaired corners . This all seems to indicate that wildlife was regularly present at the site of the Weber reservoir and could have been a vector for Salmonella
contamination.

CRAFT TOWER

The Craft Tower is a 500,000 gallon spheroid elevated tank. This tank was constructed in 1984. The most recent inspection prior to the outbreak was in July 1997 by a professional inspection firm. At that time the tower was in generally good condition, wit h some blistering and corrosion of surface materials. There were no comments made at the time indicating poor sanitary conditions that would impact water quality.

In response to the outbreak, the tank was inspected another time by a professional inspectio n firm on April 3, 2008. The SDW program team reviewed the reports of this inspection at the time of the outbreak and interviewed the inspection firm personnel in the spring of 2009. Based on the information gathered, the vent in the Craft Tower was in n eed of minor repair at the time of the outbreak. Fecal matter from birds was observed on the top of the tower at that time, sediment and debris were noted inside the tank. The inspectors recommended maintenance and repairs, including cleaning and recoati ng the interior and pressure washing the exterior.

Based on a review of records and discussion with city personnel, the city did not maintain a routine of flushing, disinfecting, or removing sediment from the tank as part of routine operations. In A pril 2008, the city performed some of the recommended maintenance and repairs . R ep lac ing the tank vent was added to the repair list in May 200 8, and the city indicated that this repair was completed . In June 2009 another inspection and thorough cleaning was completed by a professional tank diving services firm. Additional maintenance activities are planned for 2010.

ROSS TOWER

The Ross Tower is a 150,000 gallon cylindrical elevated tank. The date of construction of this
tank is unknown, but it was li kely built in the 1930’s or earlier, based on estimates from city personnel . No written records are available for the most recent inspection or clean

- out of the Ross Tower prior to the outbreak ; however, city personnel have stated that it was repainted
in side and out around 1985. This was likely the last time the tank was cleaned prior to the
outbreak. It was scheduled to be inspected in 1997, but this inspection did not take place reportedly because divers from the inspection firm were not able to acces s the tank while it was in service due to the configuration of the access hatches.Salmonella Outbreak in Alamosa, Colorado, March and April 2008

42 On April 2, 2008, the tank was inspected by a professional firm in response to the outbreak. The
tank also was removed from service for repairs and cleaning. During clean

- out, an estimated 145 gallons of sediment were removed from the bottom of the tower. Based on a review of records and interviews with tank inspectors, the Ross Tower was in need of minor sanitary repairs and more significant emergency safety repairs in Ap ril 2008. Minor sanitary issues included some gaps at the seams between structural panel s in the tank, and fecal matter from birds observed at the top of the tower. It is possible that fecal matter could have been flushed into the tank from
holes created by missing bolts. The inspectors recommended maintenance and repairs, and work was completed in April 2008.

Based on a review of records and discussion with city personnel, the city did not maintain a routine of flushing, disinfecting, or removing sediment from the tank as part of routine operations. After the outbreak, the city improved its maintenance and operations plan for the Ross Tower and all tanks. At this time, the Ross Tower is used exclusively for untreated water storage for the new wat er treatment plant. No treated water is stored in the Ross Tower.

As part of the investigation, in June 2008 the SDW program team obtained two 500 milliliter ( mL ) samples of sediment collected from the Ross Tower and examined it in the lab visually and

us ing a simple optical microscope. One of the 500 mL samples was visually examined. The bulk sample did not contain large specimens of material; it was primarily silty and sandy sediment. Both 500 mL samples were passed through sieves at #8, #16, and #20 mesh screens and rinsed.

A small sample from the #8 sieve was observed under an optical microscope. It contained small pebbles, estimated between 0. 1 centimeter (cm) and 1 cm in diameter . There also appeared to be a small piece of wooden material and a seed pod. A sample from the #16 sieve included smaller rock fragments and what appeared to be very small steel balls. The source of the small steel balls is unknown; it is possible that it could have been birdshot or residue from a previous sandblasting operation. There also appear ed to be small insect fragments. A sample from the #20 mesh contained smaller rock fragments and even smaller steel balls. None of the samples contained evidence of small bones, feathers, or other organic matter that would i ndicate
infestation or habitation of animals in the Ross Tower.

DISTRIBUTION SYSTEM

Alamosa’s distribution system contains over 800,000 gallons of water in about 50 miles of distribution line. According to engineering reports, the system is compos ed primarily of polyvinyl chloride ( PVC ) , concrete

- asbestos, and cast

- iron pipe. A small amount, about 1

, 800 linear feet, is high density polyethylene ( HDPE ) . The newer PVC pipe is generally less than 15 years old. The concrete

- asbestos and cast

- iron pi pe is typically older than 20 years , with some of it installed in the early part of the twentieth century

.Salmonella Outbreak in Alamosa, Colorado, March and April 2008

43 According to records and communications from city personnel, at the time of the outbreak, the city did not have an active distribution system maint enance and flushing program or a cross

connection control program. Distribution system operations were typically limited to responding
to line breaks.

As part of the investigation, the SDW program employed an engineering consulting firm to
model the flo w of water in the distribution system around the time of the outbreak. In general,
over 75 percent of the water being pumped to the system was from the Weber well through the
Weber reservoir at the time of the outbreak. Another 20 percent of the water pu mped was from
the Cole Park well , with the remainder coming from occasional pumping of the other wells

. With information available, including results from the hydraulic model of the system, it is difficult to pinpoint the defined area of influence of eac h water tower. In general, the Craft Tower typically received water from the Weber Reservoir. Subsequent hydraulic modeling of the Alamosa water system demonstrated that it is unlikely that contaminated water from the Ross Tower would have had a signific ant influence on the north part of town where the Craft Tower is
located.

Further, model results indicate the area of influence of the Cole Park well did not extend to the Weber well or Craft Tower, and was confined primarily to the downtown area. Thus, any northward flow would have been from the Ross Tower, which would not hav e had a large influence on water quality in the north part of town. Salmonella bacteria were found in the northern reaches, and in fact all over the city’s distribution system

. T his support s the conclusion that the source of bacteria was in the north par t of the city near the Weber well

.

HOW MUCH SALMONELLA ?

This investigation included a n estimation of the quantity of bacteria required to contaminate a system of water storage facilities and distribution lines the size of Alamosa’s in its entirety with

an infective dose of Salmonella for humans. Estimates of the number of Salmonella bacteria for
an infective dose to a small child found in the literature were as low as 10 to 100 organisms , with
adult s p ossibly needing a higher dose. Based on telephone sur veys, about 40 percent of infants in Alamosa were sick during the outbreak.

At the time of the outbreak it is estimated that at least 800,000 gallons of water were contained in the city’s distribution lines and at least another 800,000 gallons of water i n the city’s storage
tanks. Based on sampling results, by March 20, 2008 all 1.6 million gallons of water in the city’s system were likely contaminated. If a person consumed as little as two cups of water to receive
100 Salmonella organisms, the associat ed level of bacteria wou ld be estimated on the order of
1.3 billion organisms systemwide. Feces from a single infected bird in the acute phase of
infection may contain on the order of 10 million to 1 billion organisms per gram . Much lower shedding rates occur at other stages of infection

. C onditions for bacterial growth may have been
favorable in storage tank sediments and distribution system biofilms due in part to the lack ofSalmonella Outbreak in Alamosa, Colorado, March and April 2008

44 disinfectant

. Thus, it is possible that a relatively small amount of animal fecal matter caused the
outbreak.

OTHER EVENTS OF INTE REST

The SDW program team investigated other events of interest that may have resulted in unusual or unique environmental conditions that could provide additional clues to the source of
Salmonella

. Precipitation and snow melt

Precipitation and temperature data were reviewed for January through March 2008, the months prior to and at the beginning of the outbreak. Noteworthy events included a snowfall of 6.7 inches on February 5, 2008, about a month p rior to the outbreak, followed by a period of warming with daytime temperatures above freezing from February 12

- 17, 2008 and again from February 20, 2008 through March 2, 2008. Other than this pattern, there was no additional significant rain or snowfall (more than 1.3 inches) prior to March 6 , 2008, the date of the first suspected case of Salmonella

. The Weber reservoir was full of warm water throughout the winter and according to city staff snow rarely builds up on top of the roof. It is possible that the snowfall, followed by rapid warming created conditions of surface flow on or near the Weber tank that carried bacterial contamination from animal feces into the tank through above or near surface fractures in the concrete. Another possibility is that the snowmelt provided a mechanism for bacterial contamination from animal feces to be transmitted through the near surface soils and into the city’s very shallow groundwater table. At least part of the year it is suspected that the elevation
of the botto m of the Weber tank is below the top of the saturated groundwater table. Because the Weber tank was full at the time, and because of the relatively flat topography in the area, it is unlikely that contaminated groundwater would have entered the tank. Ano ther possibility is that contaminated groundwater entered the casing of the Weber well, which is in aging condition, and contaminated the water system as well pumps drew shallow groundwater and introduced it to the water system . Although this may have occ urred, s ampling results do not support the theory

. River Stage Data

Based on a review of U

. S

. G eological S urvey (USGS) gage data for the Rio Grande River in Alamosa for January through March 2008, there were no unusual flows in the Rio Grande River,
which flows through the city. The gage height remained at a relatively constant 3.55

- 3.56 ft for the period January 16, 2008 through March 11, 2008. This indicates no significant flooding or shift in the subsurface hydrology caused by significantly changing ri ver conditions around the
time of the outbreak.Salmonella Outbreak in Alamosa, Colorado, March and April 2008

45 Fires

There were no fires in the city around the time of the outbreak that would have either impacted water infrastructure directly or indirectly by creating unusual demands on the water system or
transient low pressure conditions from fire flow.

Low Pressure Events

Based on a review of tank level and pumping data for January through March 2008, there were no unusual low pressure events. On February 12 and 20, 2008, there were significant draws on the syste m related to construction at the new water treatment plant. These draws are evident
from the tank level records on both dates. Detailed information about these occurrences is in the previous section of this report under “Storage Facilities

. ” T hese flows probably did not create low pressure events in the system. No other information about system operations or customer complaints indicated that a low pressure event occurred at any other time around the time of the
outbreak.

Special Events

According to a written statement from the city, there were no special events in the city from January 1, 2008 through March 31, 2008 other than the normal seasonal sporting events that occur every year at that time.

Construction and/or Maintenance Activiti es

According to a written statement from the city, all construction activity involving excavation was suspended during the period January 1, 2008 through March 31, 2008 due to weather. Adams State College continued above ground construction of Plachy Hall on Stadium Drive and El Rio Avenue during this period but did not perform work on water or sewer line connections until July
2008.

Seismic Activity

In March 2009, the SDW program team requested information from USGS about any unusual seismic activity ar ound the time of the outbreak that may have impacted the subsurface hydrogeology in the region. In an email response to this request dated April 1, 2009, the USGS stated that they had searched their earthquake database and determined that there was no sei smic activity located within a 75 kilometer (km) radius around with city during the period from
October 1 , 2007 through April 1, 2008 . During the same period, there were six events on the east side of the Sangre de Cristo mountains, east of Alamosa, and w ithin a 150

- km radius. All but one of those events were located in an area of natural gas wells in western Las Animas County, Colorado, and western Colfax County, New Mexico. The email response further stated that “unless the Alamosa water supply comes f rom aquifers that include the east side of the Sangre De Cristo Range, it would seem that there was no earthquake activity during that period that could have affected the water supply.”Salmonella Outbreak in Alamosa, Colorado, March and April 2008

46 Vandalism or Tampering Events

According to a statement from the city dated January 14, 2009, there were no vandalism or tampering events related to the c ity’s water system in the year prior to the outbreak . There were moderate levels of graffiti at different locations throughout the city, but none that targeted the
water f acilities.

Staffing Changes

The city did not experience any changes in its public water system operational staff around the
time of the outbreak.

ADDITIONAL DATA COLL ECTED AFTER THE OUTB REAK

In the spring of 2009, the SDW program team conducted three roun ds of water quality sampling in the surface water environment in Alamosa and in the city’s water system. The purpose of the sampling was to characterize source water quality during the spring season and to gain a better understanding of the prevalence of Salmonella

. The sampling events were conducted in February, April, and May 2009. During each event, grab samples were collected from ambient surface water where birds and deer had been previously observed. Samples were collected during all three events from the wetlands area northeast of Craft Drive and Park Avenue. Samples were analyzed for temperature, pH and Salmonella . No samples were positive for Salmonella . Additional samples were collected from a private lake
northwest of Lakewood Drive and Ri verwood Drive in the northern area of the city during February and April 2009. These samples were also analyzed for temperature, pH, and
Salmonella . No samples from the lake were positive for Salmonella . Based on the samples
collected from the ambient e nvironment, there is evidence that Salmonella was not prevalent or widespread in the city’s natural surface water during the spring of 2009. No similar water quality data were collected during the outbreak, so this result is inconclusive as it pertains to the investigation.

Samples from the city’s Weber well and Cole Park well also were collected and analyzed for turbidity, temperature, pH, Salmonella , total coliform, heterotrophic plate count, Salmonella

, TOC, and nutrients. Microscopic particular analy ses also were performed for each well. Over the three events, there was a slight increase in turbidity at the wells, and a slight increase in TOC at the Cole Park well. There was a low level of heterotrophic bacteria in each of the wells. The
wells were negative for total coliform and negative for Salmonella

. During the spring of 2009, additional samples were collected from the Weber reservoir (untreated raw water) and from the outlet of the Craft Tower (treated water). None of the samples were positi ve for total coliform or Salmonella . This suggests that Salmonella did not exist either in the Weber reservoir or the city’s distribution system at the time of the sampling in
2009

.Salmonella Outbreak in Alamosa, Colorado, March and April 2008

47 REVIEW OF EPIDEMIOLO GICAL REPORTS

As part of preparing this investigation report, the SDW program team was in communication with county and state epidemiologists about the pattern of the outbreak and details regarding specific cases. According to the epidemiological evaluation of the outb reak, there were 442 reported cases of illness, 122 of which were lab oratory

- confirmed, and one death. Epidemiological estimates suggest that up to 1

, 300 people may have been ill.

The Alamosa County health department and the CDPHE epidemiologists are pr eparing separate reports with a detailed emphasis on surveillance, analysis, and their response to the outbreak. Details of specific cases, including case maps, are protected information for privacy reasons. However, generally speaking, there is no obser vable statistically significant pattern in the case history of this outbreak that points to a single, specific location where contamination was introduced to the water system.

Figure 3 illustrates the epidemic curve for the Salmonella outbreak in Alamosa . Based on the disease onset dates illustrated in this figure, and the number of cases reported each day, it is
estimated that Salmonella was introduced to the city’s water system sometime between March 3
and March 5, 2008 . By March 10, Salmonella was pr obably present throughout the entire distribution system. A detailed evaluation of the early confirmed cases of Salmonella with disease onset dates from March 6 through March 10 also do not reveal where the original source
of contamination occurred. This is in part because surveys of the early cases indicate that the individuals had multiple potential exposure locations around the city , including areas with high overall water usage that likely became contaminated relatively quickly . Overall, based on a

r eview of the epidemiological data and associated reports, the case history of the Salmonella outbreak in Alamosa does not form a pattern that identifies the exact location where the
contamination originated. However, the fact that people throughout the en tire system, and visitors to the area who stayed only briefly, all got sick indicates that the likely source of contamination would be a location that supplied the most water that could reach the entire system. Contamination emanating from the Weber Rese rvoir best fits that overall fact pattern.Salmonella Outbreak in Alamosa, Colorado, March and April 2008

48 LITERATURE REVIEW

As indicated earlier in this report, the SDW Program team became very interested in prior reports of similar disease outbreaks and other related literature very early during this incident. The team worked closely with CDC to assemble the most relevant material that could provide useful information. During the o utbreak and over the subsequent months, numerous literature articles were reviewed , including 15 reports/papers regarding previous Salmonella outbreaks in the U.S. and abroad, as well as several other relevant papers and communications with various experts (references 1 to 2 9 in Appendix E) . Appendix E summarize s only those references deemed most relevant to the Alamosa outbreak cause investig ation, and a brief discussion is included below

.

 Where a contamination source was identified, an animal source was often confirmed or suspected, and a wide range of animals can be carriers of Salmonella

. A report from the early 1970s showed that a large water reservoir could be contaminated with Salmonella from birds. This also wa s very possible in the Alamosa case based on the DNA analysis of the Salmonella strain. The 1999 USGS report states that bird mortality caused by Salmonella Typhimurium has in creased since 1980, and Colorado is shown to have had eight avian outbreaks from 1983

- 1997. Studies from Norway and Tasmania, Australia also show how Salmonella can find a reservoir in wildlife populations, and that FIGURE 4 : EPIDEMIC CURVE n = 436 6 cases missing
onset dateSalmonella Outbreak in Alamosa, Colorado, March and April 2008

49 unchlorinated drinking water is a key r isk factor for human illnesses. Outbreaks occur most frequently in winter and spring. Small rodents and mice are also listed as common sources of Salmonella

.

 Contamination, when the source was confirmed, was often introduced at a storage tan k. Similarl y, the C ampylobacteriosis outbreak in Greenville, Florida was suspected to be caused by bird feces contamination in a final treatment tank.

 Salmonella outbreaks typically occur when t here is n on

- existent or ineffective disinfection. This was the case in Alamosa as well.

 Sampling for total coliform bacteria is not very reliable to detect Salmonella contamination. This also was observed during the Alamosa outbreak.

 Based on the Riverside epi demiological report

, Salmonella survival studies, and other literature, a low infective dose of 10 to 100 organisms in drinking water may be sufficient

to cause illness. Also, the bacteria can survive in drinking water or biofilms for at least a week, dep ending on the level of contamination. It also is possible that Salmonella can grow to some extent in the sand in the bottom of a tank, or in biofilm that may exist in the distribution. This supports the flushing approach taken in response to the Alamosa

o utbreak.

 Animals infected with Salmonella can shed 10 million to 1 billion bacteria per gram of feces during the acute phase of infection, whereas animals recovering from infection or simply carrying the bacteria may shed 10,000 to 100,000 organisms per gr am of feces, or less.

 Most, if not all, the outbreak investigators were left with at least some unanswered questions, and in some cases the contamination source remains unknown. There are now, and likely always will be, some questions about the Alamosa ou tbreak that cannot be answered, primarily because the likely contamination date range was about March 3 to 5, 2008, whereas the waterborne nature of the outbreak was not confirmed until about two weeks later.

Overall, the literature review , in conjunction with all the information gained during the investigation, support s the likelihood that an animal source of Salmonella bacteria entered the Weber Reservoir and then contaminated the remainder of the Alamosa drinking water system. Additionally, the literat ure review supports the extensive disinfection and flushing work done in the distribution system and other measures taken to protect public health like disinfecting and sampling water hauling trucks prior to allowing them to provide drinking water to the p ublic.

REVIEW OF STATE PUBL IC WATER SYSTEM FILE

The SDW program team conducted a file review of historical records on the city’s system, including information about the city’s disinfection waiver, sanitary surveys, and other records. A
disinfection waiv er was requested by the city on September 15, 1969 and initially was not approved. Later, the waiver was approved on December 17, 1974, but with cautionary language
further advising the city to consider disinfecting the water supply “as an additional safe guard

. ”

Sanitary surveys were conducted regularly by representatives of the state health department, and based on file records inspectors did not note any significant deficiencies associated with the city’s water system operations or infrastructure.Salmonella Outbreak in Alamosa, Colorado, March and April 2008

50 Si nce 2004, the city had actively been on a path to install centralized treatment for arsenic removal. This was mandated under an Enforcement Order on Consent, originally dated February 2005. The treatment plant went online serving water to the Alamosa com munity in the fall of 2008 and arsenic levels have been in compliance since then.

As discussed previously in this report, the city did not have other known patterns of non

compliance at the time of the outbreak . In 2002 the city had six positive total coliform sample s, and in 2003 they had one positive total coliform sample. All positive results were followed by negative results in repeat sampling. One non

- acute MCL violation of the Total Coliform R ule
was issued in November 2002.

Pred icated upon the lack of significant results demonstrating noncompliance with other standards or requirements, the priority for Alamosa had centered on addressing the long

- standing issue of high arsenic levels in source water. Additionally, since the new d rinking water treatment plant being constructed would include disinfection, enhancing the existing system, prior to the
Salmonella outbreak, did not appear to be the most pressing or significant issue for the city.Salmonella Outbreak in Alamosa, Colorado, March and April 2008

51 

### PART IV: INVESTIGATI ON AND OBSERVATIONS

CLOSING THE INVESTIG ATION

M ultiple possibilities were explored as the potential source of the Alamosa outbreak

. It cannot be state d with complete certainty what happened during the first week of March 2008 to contaminate the water system. It must be remembered that the potential for a waterborne
outbreak was not even identified to the state until March 14, 2008, and that investigations into the water system did not begin until March 17, 2008. However, know n issues with the water system that could have potentially caused this outbreak have been reviewed by the investigation team, and have been addressed sufficiently to substantially reduce the risk of another outbreak associated with the drinking water system in the future in Alamosa.

While a few causes remain theoretically possible, the most likely cause was that the crack s and holes in the Weber Reservoir allowed animal waste to contaminate the water therein, which was then pumped to the rest of the distribution system. Table 1 summarizes the most significant facts that point to the Weber R eservoir as the entry point for contamination. T he Weber well and reservoir system supplied over 75 percent of the city’s water supply at the time of the outbreak. Further, Salmonella contamination was found throughout the system. Of the two primary wells in service around the time of the outbreak, only the Weber Well and Reservoir were most capable of supplying water to the entire system. This conclusion was derived from efforts to

reconstruct flows using a hydraulic model of the city's distribution system.

It also is likely that the original contamination source came from a single animal or small group
of animals that contaminated one location in the water system . This t ype of Sal monella and its DNA pattern has been found previously in Colora do, Texas, and Wyoming wildlife and
Salmonella with the same DNA pattern was found in all the water samples throughout the distribution system and in the patients. In other words, if there had been several different types of animals or multiple contamination points, it is likely that there would have been different etiologic agents (pathogens) , or at least different DNA patterns.

The entire volume of the Weber reservoir theoretically is excha nged with new water multiple times per day, due to system demand drawing from the reservoir and well pumping that replenish es the reservoir from the Weber well. I t is believed that Salmonella could have propagated at least to some extent in the sediment in the bottom of the Weber reservoir and the city’s distribution system, based on available information on water quality. It is also possible
that the source of contamination , although theoret ically small in quantity

, could have been continuous or repeated, at least for some period of time.Salmonella Outbreak in Alamosa, Colorado, March and April 2008

52 TABLE 1 : INVESTIGATION SUMM AY



### Table 1: Investigation Summary: Contamination of the Weber Reservoir

 Sanitary defects in the reservoir, including cracks and holes in the concrete structure large enough to allow entry of small animals and runoff from the roof.

 Evidence of wildlife presence near the reservoir in winter conditions, and a photograph of bird feces on a repaired corner of the tank (taken in July 2009).

 Over 75 percent of water in distribution system at the time of the outbreak came from the Weber well and passed through the Weber Reservoir.

 Salmonella contamination was found the throughout the system, and only the Weber Reservoir supplied water to the whole system.

 O n March 21, 2008, samples for the Weber well (which pumps to the Weber Reservoir) and Cole Park well were total coliform negative, whereas the sample from the Weber Reservoir was total coliform positive.

 Literature review, in conjunction with the other in formation gained during the investigation, supports the likelihood that an animal source of Salmonella bacteria entered the Weber Reservoir and then contaminated the remainder of the Alamosa drinking water system.

 Small quantities of animal feces could co ntaminate the entire distribution system at a level consistent with an infective dose.

 In the weeks prior to the outbreak, there was a relatively significant snowfall event followed by a warming period. Snowmelt could have been a vector for contaminated feces or other material into the Weber Reservoir.Salmonella Outbreak in Alamosa, Colorado, March and April 2008

53 C onsidering that the contamination was likely introduced at the Weber reservoir, i t is possible that one animal or group of like animals repeatedly contaminated the tank over a period of time
so as to introduce sufficient waste to create a continuous source of Salmonella

. An other possibility is that a single contamination event occurre d at one point in time, perhaps in the w est end of the tank where water may have been relatively stagnant. Water in a stagnant part of the
tank would not ha ve been exchanged routinely as system demand and well supplies created a regular pattern of flow in the tank. In that case, Salmonella could have grown over an extended period of time in th at area until it reached an infective dose level and caused an outbreak. Based on the information available, either possibility is plausible , and numerous other pos sibilities
exist

. The investigation yielded suggestions for future research that may be taken up by other investigators. Some ideas include studying:

 Potential sources of Salmonella for the quantity of bacteria required to contaminate a

wate r system like Alamosa’s with an infective dose of Salmonella

.

 The ability and pace of propagation of Salmonella bacteria in the water quality matrix
that existed in Alamosa at the time of the outbreak.

 The ability for Salmonella to exist and propagate in s ediment in an unchlorinated water storage tank over an extended period of time

.

 The ability for Salmonella to exist and propagate in sediment, scale, and biofilm in unchlorinated water distribution lines over an extended period of time.

LESSONS LEARNED

In the 21 st century, those members of the water profession who dedicate their careers to ensuring the provision of safe drinking water in the United States most commonly speak in terms of regulatory requirements and calculated risk

– not outbreaks, cases a nd deaths. The Alamosa
Salmonella outbreak in the spring of 2008 was the kind of event that drinking water professionals spend their days and sometimes nights working to prevent from ever happening. This happens quietly, continuously, and largely unnotic ed by the public.

A public water system is defined in the Colorado Primary Drinking Water Regulations as a water system that serves 25 or more people or 15 or more service connections more than 60 days out of the year. According to estimates from the EPA , public water systems provide drinking water to
90 percent of Americans. In Colorado alone, safe drinking water is delivered by about 2,000 public water systems governed by the Safe Drinking Water Act, serving houses, apartments, restaurants, schools, and campgrounds across the state.

Sometimes though, something goes wrong. There is a failure in the physical, regulatory, or human infrastructure and the water delivered to the tap is not safe to drink. In an effort to learn
from the outbreak in Alamo sa, this section discusses opportunities for the SDW program and public water systems to improve

, outlines changes in the SDW program strategies and practicesSalmonella Outbreak in Alamosa, Colorado, March and April 2008

54 that are designed to be preventative , and identifies areas that went well during the outbreak

res ponse and investigation

.

OPPORTUNITIES TO IMP ROVE

As discussed previously

, the city had no other known patterns of non

- compliance with drinking water regulations related to health effects, with the exception of exceeding the health

- based
standard for arsen ic. Further, the city had no unaddressed deficiencies noted during routine sanitary surveys conducted by CDPHE , although the sanitary surveys conducted prior to the
outbreak did not include a comprehensive investigation of the city’s distribution system
i nfrastructure

.

At the time of the Salmonella outbreak in Alamosa, the system had been evaluated in the previous year by engineers from the private sector and the SDW program . By all common measures, the city was maintaining compliance with regulations at a level consistent with protection from acute risk to public health. Clearly, however, there was a failure of the combined physical, regulatory, and human infrastructure that resulted in this outbreak. On reflection, the authors offer the following less ons learned from this experience.

Emphasize oversight of total coliform sampling and storage and distribution systems

The primary drinking water regulations require that public water systems regularly analyze the microbiological quality of representative and properly collected samples from the distribution system using the total coliform test. This requirement reflects the fact that this testing, properly conducted, is particularly effective at detecting ongoing, con stan t microbiological contamination
tha t may be present at each sampled location. The test is also designed to detect incidence of intermittent microbiological contamination that may be present at each sampled location.

Prior to the outbreak, t he city of Alamosa did not have a significant hi story of total coliform sampling that showed the presence of bacteria. The city has very deep wells which generally reflect good bacteriological quality. Although the SDW program team reviewed the results of the city’s total coliform sampling, it did not scrutinize the city’s total coliform sampling methods or its storage and distribution management system. Subsequently , t his investigation identified that the city of Alamosa had not historically been collecting total coliform samples that were representa tive of water quality in the distribution system, and sampl ing was not done in compliance with the T otal C oliform R ule. Because proper bacteriological sampling procedures conducted at the right locations is critical to determine compliance with the primar y drinking water regulations, the SDW program team determined that it needs to make the oversight of these procedures a priority

. To ensure the quality of tap water, r obust distribution and storage operation and maintenance programs are needed at public w ater systems

. A history of total coliform absence is not enough to ensure safe bacteriological quality, especially in an unchlorinated system . The water storage and distribution system itself must be properly operated to maintain its integrity and protec t the public’s supply of safe drinking water from contamination. As i t is possible that only a smallSalmonella Outbreak in Alamosa, Colorado, March and April 2008

55 quantity of animal feces contaminated the Alamosa system, it is particularly important for water systems to develop and implement robust plans for samplin g , and storage and distribution system operation and maintenance programs, including a cross connection control program. This includes, but is not limited to, increased monitoring and response to system

- specific triggers related to water quality, system p ressure, infrastructure condition, cross connections, repair practices, dead ends, and customer complaints.

A significant lesson learned is to emphasize oversight of these critical operations so that all
future sanitary surveys comprehensively cover t he basics, including accurate and up

- to

- date total coliform sampling plan and sample collection, distribution and storage components, and complete operations and maintenance plans. Training and technical assistance offered to public water system personnel also should put more emphasis on correct total coliform sampling and storage tank inspections and maintenance.

Inventory and track all water storage facilities

There are no federal requirements for storage facilities to be included in sanitary surveys of public water systems that use groundwater as their primary source. This is scheduled to change effective December 1, 2009, and as of that date sanitary surveys of groundwater systems will be required to cover storage facilities and numerous other aspe cts of the technical, managerial, and financial capacity of each system. It is significant, however, to note that state sanitary survey requirements at the time of the outbreak did include an obligation to inspect storage facilities, although federal requ irements did not.

With limited resources, the SDW program made an effort to prioritize tracking water storage
facilities in the SDW program database starting in about 2002. Tracking and inspecting these facilities, however, is relatively new for the SDW program in Colorado

, and the Weber R eservoir
was not in the database inventory at the time of the outbreak. Indeed, tracking these facilities is
not a difficult task on its own, but the underlying reasons they are not tracked is because of competing and higher priority tasks for both inspectors and data managers. Placing higher emphasis on tracking water storage facilities could assist in earlier identification of san itary and
maintenance issues.

Prioritize detecting and addressing deficiencies at water systems that do not disinfect

Public water systems with disinfection waivers should be looked at with a higher level of scrutiny to detect significant deficiencies . On ce deficiencies are identified, they would need to be prioritized for follow up activities

. The SDW program did prioritize Alamosa in recent years as a very high program priority to address the arsenic violations. Many resources were spent on addressing that issue program

- wide, from enforcement to engineering to financial solutions. Protection of bacteriological quality was not an identified deficiency at the time of the outbreak and did not have the same level of emphasis as the arsenic violations

.

The regulatory infrastructure is designed to have multiple barriers in place to protect public health, and Alamosa lacked certain treatment and non

- treatment barriers that exist at many other public water systems. Alamosa’s history of total coliform monitorin g revealed no noteworthySalmonella Outbreak in Alamosa, Colorado, March and April 2008

56 patterns of the presence of bacteria in the city’s system. Routine monitoring for total coliform did not predict an outbreak of Salmonella in the city’s drinking water supply . However, because

s ampling wasn’t done in compliance w ith the Total Coliform Rule (well source samples versus true distribution samples) , historical data are inconclusive

. Of all the regulated public water systems in Colorado, Alamosa had not been prioritized for
assistance or enforcement related to issues ot her than their arsenic violations. A t the time of the outbreak there was a perfect storm of multiple defects emerging that together created a riskier
situation than was thought to exist . The city’s water system was being operated under a
disinfection wai ver, with limited cross connection control, and no documented system, schedule or records, of disinfecting and flushing lines and storage facilities. Further, two of the city’s storage facilities had significant integrity problems from aging and lack of m aintenance.

Prioritize the periodic review of disinfection waivers

Federal regulations do not require public water systems using groundwater as their primary source to disinfect the water at the source or in the distribution system. Further

, many communities, especially those operating under disinfection waivers, are very resistant to chlorinating their drinking water. Communities resistant to chlorination commonly cite the cost
of treatment or the complaints regarding the taste of chlorinat ed water.

Although no federal mandate ever existed, the state health department in Colorado began requiring disinfection of public water supplies years before the federal Safe Drinking Water Act was passed in 1974. This requirement has been waived by th e state health department on a case

by

- case basis over the years.

According to historic records, Alamosa’s disinfection waiver was issued five years after the city applied in 1969

. In 1969 the state strongly recommended that Alamosa employ disinfection
treatment, but then granted the waiver in 1974 . Through the 1970s and 1980s there were numerous opportunities to re

- evaluate the waiver in the context of total coliform positive results. The state’s SDW program always has faced tough decisions on assigni ng resources to competing priorities; that has resulted in prioritizing other activities over the review of disinfection waivers in the past. Starting in 200 7 , however, the SDW program team recognized the need to revisit the
waivers. The outbreak in Alam osa confirmed waiver review as a priority.

Total Coliform bacteria monitoring is not a good indicator for Salmonella

During this disease outbreak , most samples taken in the distribution system were absent for total coliform while people drinking water fr om the city were being exposed to Salmonella and getting sick. This was also the case in the Riverside, CA and Gideon, MO Salmonella disease
outbreaks. Total coliform monitoring, by itself, is not sufficient, especially for systems that do
not disinfect. Indeed, it is not possible to sample unchlorinated drinking water frequently enough or for all the pathogens that could be present. This is a strong argument for all water systems to provide disinfection, as is the possibility that only a small quantity of animal feces may have
caused the Alamosa outbreak.Salmonella Outbreak in Alamosa, Colorado, March and April 2008

57 It has been noted in this report that Alamosa was not collecting its total coliform samples properly. In light of the above discussion, it is possible that even if the total coliform samples
collect ed on March 5, 2008 were collected properly, that they would have been negative.

Address resource needs for Safe Drinking Water program

The Safe Drinking Water Program has been, and is now, under

- resourced to provide a robust level of oversight to the approximately 2,0 0 0 public water systems in Colorado. This has been the case since the inception of the program in the early 1970s, and has been periodically
documented over that course of time.

EPA issued a report in November 1974 after conducting a deta iled evaluation of the SDW program in Colorado. A key conclusion was that the program was severely under

- resourced. The report stated, “A false sense of security might well exist concerning the safety of water supplies in Colorado. Colorado’s water supp ly program is not meeting its responsibility of protecting the quality of water served to the State’s citizens and visitors. This situation is a direct result of the lack of resources allocated to water supply activities.” T he program staff consisted
of about 1 3 employees, but many split duties between programs , such as swim pools, septic systems, plumbing inspections, and solid waste, and did not devote all of their time to safe drinking water activities. Thus, the actual level of full time equivalents ( FTE ) devoted to safe drinking water was considerably lower.

In 1974, EPA advised the state that 23 FTE fully devoted to safe drinking water would be needed by 1977. Additional r ecords from the 1970s are scant, but it is believed that resource levels fo r the SDW program did increase slowly, until November 1977 when Colorado adopt ed regulations
and bec a me the primacy agency to implement the 1974 f ederal Safe Drinking Water Act.

Detailed records of staff levels and program evaluations from the late 1970s to mid

- 1980s are not available, but anecdotally, staff from those times report that the program did gain resources, but not in sufficient quantit y to keep up with the pace of changing drinking water regulations. In particular, the 1986 Safe Drinking Wate r Act amendments substantially enhanced the regulatory provisions to protect public health, but Colorado’s in ability to add resources to pro perly implement the program almost led to EPA’s revocation of Colorado’s Safe Drinking Water Act primacy authority. The FTE level for the SDW Program stood at about 12 FTE by 1989. In 1994 EPA began the formal process to withdraw primacy authority . At the time

, Colorado was
cited by EPA for inadequately adopting and implementing new regulations including surface

wate r treatment rules, not properly processing or reporting chemical or radiological data, and rarely taking any type of enforcement action. The program staff level was about 1 7 FTE, compared to the 3 3 FTE minimum level that EPA believed was necessary for sat isfactory program performance. Detailed records of how this situation was resolved are not available, but it appears that the SDW program was able to gain some additional funding from the legislature and utilized some federal employees on a temporary basi s. By 1995, the SDW p rogram had about 20 FTE, and EPA did not withdraw primacy.

However, this process nearly repeated itself after the pass age of the 1996 Safe Drinking Water Act amendments. Colorado did not have resources to adopt the associated new regulations in aSalmonella Outbreak in Alamosa, Colorado, March and April 2008

58 timely fashion and requested extensions from EPA for adopting the se new regulations to enhance public health protection . In Febr uary 2001

, EPA granted an extension request regarding nine significant regulations/issues. In a June 2 00 1 SDW Program audit, EPA again noted insufficient resources being devoted to enforcement. Between 2001 and 2004 the SDW Program added

some FTE

, but i t would not be until 2005 that Colorado was fully caught up with adopting the required regulations to maintain primacy authority

. W hile Colorado was able to adopt these new regulations, the gap in resources needed to implement them grew.

In 2004 EPA conduc ted another audit of the SDW program and concluded that the program was still substantially under

- resourced. In 2004 the program staff level was 37 FTE compared to the minimum 72 FTE level that EPA, and other staff resource models, believed was necessary at that
time. For later years in this decade

, the minimum staff level necessary was est i mated to in crease to 82 FTE, in large part due to an entire new suite of regulations addressing microbial contamination and disinfection byproducts. The regulations impose more complex and stringent requirements , including increasing oversight of surface water treatment plants in the wake of the
C ryptosporidium outbreak in Milwaukee that occurred in 1993.

The SDW program has been aware of these resource shortfalls and has been successful in gaining resource s , albeit not rapidly enough to fully close the gap. This situation has been publicly reported to the state legislature in the 2005 Senate Bill 276 report, and subsequent long
bill “Footnote” reports (Footnote 109 i n 2007 and Footnote 55 in 2008). With the support of stakeholders and the state legislature

, both general funding for the SDW program and fees applied to public water systems have increased in recent years. By 2008, at the time of the
Alamosa outbreak

, t he SDW program staff level stood at about 5 4 FTE, and in 2009 stands at
about 6 7 FTE, still well short of the minimum necessary. The SDW program will again be working with stakeholders to gain their support for additional funding.

What does this mean for program performance in 2009? Because of increasing resource levels
obtained in the 2000s, t he SDW program has made significant improvements. All of the federal regulations promulgated in the latter half of this decade have been ad opted on time in Colorado, and we are slated to maintain full primacy authority from EPA for the foreseeable future. Colorado is able to take timely and appropriate enforcement actions in response to the most serious drinking water violations and conducts routine compliance inspections as required by the
federal S afe D rinking W ater A ct.

The SDW Program also takes swift action when it becomes aware of potential acute health risks at public drinking water systems, responding to about 1 63 such incidents bet ween January 1, 2006 and December 31, 2008

. It is not possible to directly state that these actions have prevented disease outbreaks, but the actions, including issuing bottled or boil water orders,
reduce the risk of waterborne disease. Colorado can be proud that about 97 percent of our population served by community public water systems receives drinking water that meets all
health

- based standards , significantly exceeding EPA’s national target of 90 percent

.
However, there are still serious deficien cies in the program primarily due to a lack of resources. For example, w hile the SDW program is able to issue enforcement orders to systems withSalmonella Outbreak in Alamosa, Colorado, March and April 2008

59 violations, it is not always possible to follow

- up on those order s in a timely fashion to ensure that
the offe nding public drinking water syste m is taking adequate steps to quickly gain compliance. Additionally, as we have learned from the Alamosa outbreak, while the SDW program has been completing inspections at required frequencies, the inspections were not com prehensive enough to detect significant deficiencies in storage and distribution system infrastructure. Furthermore, once inspection findings are issued to public water systems, the SDW program struggles to
follow

- up on violations and infrastructure defic iencies discovered during inspections. Indeed, it was reported in April 2009 that about 120 community water systems in Colorado may have unresolved significant deficiencies, or may have resolved them, but the SDW program is unable to adequately track thes e efforts. More recent improved data shows that this number may be
down to 73 communities in the fall of 2009.

Another area of significant weakness is in oversight of non

- community water systems. These systems meet the definition of a public drinking w ater system, but do not serve year

- round residents; examples include rural school districts and campgrounds. There are about 1, 1 65 such systems in Colorado, but the SDW program has historically focused on community water systems, and provided only a bare minimum level of oversight to non

- community systems. A

non

- community system experienced a waterborne disease outbreak of norovirus in 2007, and the SDW pr o gram has subsequently been attempting to enhance its oversight of these systems.

The SDW program intends to continue its efforts to work with stakeholders and the legislature to gain adequate resources to conduct a more robust over sight program. The SDW program understands its strengths and weaknesses, and is working toward prioritizing activities to get the best public health protection possible with its limited staff, while still meeting basic regulatory requirements.

Try to find resources who can work on the cause investigation up front

During the crisis response, it may have been beneficial to have had additional highly specialized resources available from other agencies on an emergency basis

, including EPA, to sup port the SDW program team’s response and investigation into the cause of the outbreak, especially during the first few days of the initial response. A team with additional resources could have performed duties such as:

 Conducting a detailed survey of t he system ;

 S ampling in many more locations including all wells and storage tanks to preserve information relevant to the cause;

 Additional sampling in the environment, including ambient waters, wetlands, wildlife survey and feces sampling;

 Preparing detai led drawings ;

 Acting as journalists to track and document field activities in writing and through photography ;

 Tracking, quality checking, and assembling analytical data from field crews and labs ; and

 Serv ing as a dedicated investigation team

.Salmonella Outbreak in Alamosa, Colorado, March and April 2008

60 However, the se resources would have needed to deploy to Alamosa with about one day notice,
and work ed all through the Easter w eekend , potentially impact ing religio us observances, and for
an i ndeterminate amount of time after that . Furthermore, e ffectively managing the additional resources would have required assistance and support from city person nel and close coordination and direction from the SDW program team. This simply may not be possible during an event of Alamosa’s magnitude, even with more resources. In a ny similar event, the first priority must always be to protect public health, and help get the system back to normal. I n a situation like the one in Alamosa, a complete

, comprehensive and ideal investigation may not be feasible, and the investigation may be a secondary or tertiary priority

. Potential partners may have included the EPA, private engineering consultants or other program or department staff with a strong background in public water system design and operations. The SDW Program will be developi ng further strategies to enhance response capabilities including developing partnerships and emphasizing investigation aspects.

LESSONS FROM THINGS THAT WENT WELL

The Salmonella outbreak in Alamosa was identified very quickly

When the water system failed, the public health network of epidemiological surveillance picked up the outbreak quickly. The regional epidemiologist in Alamosa identified the outbreak and alerted the state within days of the first noted cases of Salmonella . Further, having both state public health professionals and the Safe Drinking Water program in the same department of state government facilitated quick communications once the outbreak was suspected. Figuring out the
cause of a disease outbreak is like trying to solve a mystery, and often takes a long time. However, in this case, the outbreak was confirmed to be waterborne and associated with the city’s drinking water supply within about one week of the first reported case. The emergency response to t he outbreak in Alamosa was swift , comprehensive, and effective in large part because of the speed of identifying that the source of the outbreak was the city’s drinking water.

A mutual aid network of water and wastewater utilities was critical to a fast, e ffective

emergency response

Following the terrorist attacks of September 11, 2001, the SDW program became eligible for federal grant funds specifically to improve emergency response capacity for public water systems in Colorado . These funds were used to h ire one person who facilitated the formation of
an association of water and wastewater utilities , CoWARN, agreeing to offer mutual aid during emergencies.

Due to CoWARN involvement, Alamosa was able to respond more quickly to the Salmonella
outbreak. With out CoWARN, the response time to completely disinfect and flush the city’s water system would have taken substantially longer. The need for emergency resources was posted one afternoon and immediately CoWARN teams started to scramble across the Front Rang e. The next day, a team meeting was called in the CDPHE offices in Denver. The day after that, people and equipment were in the field with equipment and resources to disinfect and flushSalmonella Outbreak in Alamosa, Colorado, March and April 2008

61 the entire water system . The timeliness was outstanding , and it bro ught experienced talent to the

response team, including distribution system and cross connection experts from larger systems. Most of the city or SDW program staff does not have the same kind of experience or training as many of the CoWARN responders to p erform the kinds of emergency operations required during
the outbreak

. Aspects of the National Incident Management System (NIMS) Incident Command System (ICS) were very helpful

The Incident Commend System was very effective in coordinating media communica tions, bulk water distribution, volunteer efforts, and communication with the public, including the CDPHE CoHelp line. The department’s Emergency Preparedness and Response Division (EPRD) was instrumental in coordinating efforts from inside and outside th e department. Internally, the Water Quality Control Division, Consumer Protection Division, Disease Control and Environmental Epidemiology , Laboratory Services Division and other divisions all worked closely with EPRD within the ICS. Specifically, the department’s Emergency Operations Center (EOC) was instrumental in providing a centralized location for staff from the involved divisions to gather and hold telephone and video conference calls with multiple agencies.

Also, the local e mergency response teams are not typically staffed with people who have expertise in water systems and their operation. It significantly enhanced the response efforts to have someone from the SDW program in the command center in Denver and would have been even more beneficial to have SDW Program staff present in the command center in Alamosa.

The local and state laboratories rapidly provided sample results

Most of the sample s collected could not be analyzed in the field for the parameters of interest, so having the right lab oratory facilities was very important to a successful response to the outbreak in Alamosa. Transportation was a complex logistical issue because of the travel time from
Alamosa to the state lab in Denver , so some samples were tested l ocally while others require d coordinated efforts for transportation to other laboratories

. The lab s w ere able to adapt their operations to meet the need for quick and accurate water quality sample results , which helped speed the response and recovery effo rts

. All the laboratories, including the federal CDC laboratories, worked extremely hard during the outbreak to quickly turnaround analytical results, including specialize d analyses like Salmonella and DNA fingerprinting.

Highly qualified technical subj ect matter experts on the SDW program team were critical to a quick, effective state response to a problem with drinking water supply.

Public water system design and operations are specialt ies in the fields of public health and environmental science and engineering. Having highly qualified and experienced human
resources on the CDPHE team proved critical to being able to quickly address the outbreak with

an appropriate technical solution. Mos t members of the SDW program team who responded were licensed professional engineers and skilled environmental protection specialists with significant experience working with the physical, regulatory and human infrastructure of publicSalmonella Outbreak in Alamosa, Colorado, March and April 2008

62 water systems, especi ally in acute situations. Without this quality of human resources on the SDW program team, the response would not have been as quick or effective.

The technical background and experience of the SDW program’s acute team was particularly
beneficial in devel oping and implementing the staged approach to implementing the bottled water order and boil water order and advising on the disinfection and flushing of Alamosa’s water system.

MODIFICATIONS TO PRO GRAM ACTIVITIES, PRI ORITIZATION, AND STR ATEGIES.

Since the outbreak in Alamosa in the spring of 2008, the Safe Drinking Water Program in Colorado has made modifications that reprioritize oversight of public drinking water systems in several ways so as to prevent a similar outbreak from occurring in the future. T his change in strategies and practices is designed to improve the ability of the program to prevent waterborne
disease outbreaks

. The SDW program has developed and is implementing several strategies to further reduce the
likelihood of waterborne disease outbreaks in Colorado. These strategies include:

 Prioritize responses to deficiencies and violations for water systems that do not disinfect ;

 Routinely r eview all disinfection waivers and withdraw waivers where appropriate to protect public health;

 Enhanc e oversight of total coliform sampling, water storage

, and distribution systems during inspections , and collect inventory information on these facilities ;

 Update and modify regulations related to disinfection waivers and groundwater disinfection in general ;

 Ensure compliance with the requirement for water systems

- to maintain residual chlorine levels in water distribution systems;

 Revise regulations associated with controlling hazardous cross connections at water systems;

 Ensure that deficiencies identifie d during inspections are corrected in a timely fashion;

 Launch training initiatives to help public drinking water systems optimize their water storage tank and distribution system operating and maintenance practices ; and,

 Develop strategies to enhance response capabilities to drinking water emergencies.Salmonella Outbreak in Alamosa, Colorado, March and April 2008

63 CONCLUSION

Thanks to a system of epidemiological surveillance and robust networks of communication, the
Salmonella outbreak in Alamosa was identified very quickly, within days of the first reported

ca se. Ultimately, the outbreak results in 442 reported cases of illness, 122 of which were
lab oratory

- confirmed, and one death. Epidemiological estimates suggest that up to 1

, 300 people may have been ill.

Once suspicion of an outbreak was reported to the Safe Drinking Water Program, the emergency response was swift, effective, and well

- coordinated with many other agencies using the National Incident Management System (NIMS) and the Incident Command System (ICS). During the
outbreak residents were advised to drink bottled water while the entire system was flushed and disinfected. Then, they were advised to boil their water until lab testing could confirm that the city’s water was safe to drink again.

At the time of the outbreak in March 2008 , the city of Alamosa was not disinfecting drinking water being provided to the public, so it was more susceptible to bacterial contamination than public water systems that chlorinate or provide other means of disinfection. Because of the quick operational response and the changes made to the physical infrastructure of the Alamosa public water system, the water in Alamosa has been safe to drink since April 2008

. In October 2008, the city began operating a new water treatment plant with advanced treatment processes
and continuous disinfection

. A comprehensive investigation into the cause of the outbreak has resulted in identification of the most likely cause: animal waste contaminating the city’s ground

- level water storage reservoir.
The concrete structure of the res ervoir was compromised at the time of the outbreak with cracks
and holes

. Records indicate that the reservoir had not been regularly maintained

, and it is likely
that the reservoir had been in poor condition for an extended period of time. Unchlorinated water in the tank was probably contaminated with animal waste that was carried into the
reservoir by small animals entering the reservoir itself or through snowmelt

. This investigation identified a number of missed opportunities to detect and address defi ciencies that increased the
risk of contamination in Alamosa’s public water system. These include non

- compliance with requirements to properly assess drinking water for total coliform bacteria and failure to prioritize
the repair of the Weber Reservoir to preserve its integrity

.

While Salmonella outbreaks associated with drinking water are ra r e, outbreaks with other pathogens associated with drinking water do occur nationally e very year . F rom 1972 through 2006, the federal Center s for Disease Control and Prevention reported a total of 628 disease outbreaks at community and non

- comm unity public drinking water systems

. In Colorado, however, disease outbreaks associated with drinking water do not happen every year, and they
have become in creasingly rare since the 1970s. Fr om 1972 through 2008, Colorado documented
64 outbreaks and almost 1 2

, 000 reported cases of illness associated with drinking water. Based on the best available data, t he number of drinking water outbreaks and illnesses b y decade are
summarized below:Salmonella Outbreak in Alamosa, Colorado, March and April 2008

64  1972

- 1979: 17 outbreaks associated with 6

, 370 cases

 1980

- 1989: 41 outbreaks associated with 3

, 810 cases

 1990

- 1999: 2 outbreaks associated with 132 cases

 2000

- 2008: 4 outbreaks associated with 1

, 410 cases

The investigation into the Alamosa outbreak of 2008 confirmed that the physical, regulatory, and human infrastructure had all failed in some way to protect the public’s safe drinking water supply. The Safe Drinking Water Program in Colorado has since made mod ifications that reprioritize oversight of water systems in several ways so as to improve public health protection
and reduce the likelihood of a similar outbreak occurring in the future.

This report has provided a comprehensive documentation of the event s in Alamosa associated with the disease outbreak including the response, cause, and lesson s learned. It is hope d that an improved understanding of this event will help all those involved in the serious business of providing safe drinking water prevent fu ture waterborne disease outbreaks.