LTC 082-2011 Wastewater Force Main Break " F D `
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OFFICE OF THE CITY MANAGER
N O. LTC °082 -20� LETTER, TO COMMISSION
TO: Mayor Matti H. Bower and Members of the City Commission
FROM: Jor M. Gonzalez City Manager
DATE April 8, .2011
SUBJECT: Wastewater Force IiAain Break— Harding Avenue and 71 Street .
On April 6;,2011 fat approximately 10:30 AM Public Works Operations Division received notification
of flooding and pavement displacement at the intersection of Harding,Avenue and 71 Street.;The
responding Utility crew confirmed that a major transmission force main that carries wastewater from
the North Beach area and three - communities north of the City and one - community west of the City
had ruptured'u`nderground. immediately, City crews began the process of isolating the break and f
securing the intersection to prevent further discharge of untreated wastewater to the City's storm
water collection system, and to protect public safety, welfare and private property.
The break occurred on a seventy -four' (74) year old section of cast iron pipe used to transfer'
wastewater from these northern communities to the County's treatment - facility on Virginia Key. The
}.Y . communities affected included Bal Harbour, Surfside, .Bay Harbor Islands and North Bay Village, as
well as portions of Worth Beach north of 72 Street.
The magnitude of the break was significant, causing- extensive damage to the intersection. Traffic
had - to be re- routed P
through implementation of a certified Maintenance of Traffic Plan (MOT) and
with the assistance of the Police. Department. All regulatory agencies were notified of the pipe f .
failure in oa timely manner, and the Public Works Department established a command and control'
emergency response team and a-single point of contact for regulatory issues and for coordination
with the contributing municipalities so that the integrity of information provided_ regulators could be
insured, - and communication. between the City and the four (4) contributing municipalities would be
clear and - concise. An estimated 1.60,000 gallons of untreated .wastewater was discharged into
Biscayne Bay before tributary flows in this complex collection system could be isolated and shut r .
down.
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The Public Works Department contracted with D Mancini and Sons, incorporated (DMSI), a licensed
underground utility contractor currently employed by the City for other public works projects, under
-an emergency declaration to expedite mobilization repair efforts. The intersection affected by
the - force main break also 'contained water, storm water, electrical, telephone and gas utilities.
Fortunately; none of the other utility lines were compromised by the break. To insure public
- health
and safety, the Public Works Department initiated extensive area wide water sampling program to
confirm the safety of the potable water system and rule out possibility of cross contamination. At
no time during the emergency was the water supply system of the city compromised, and
utility services (telephone, gas and electric) remained .unaffected.
`Public .Works and 'DMSI crews worked throughout - the night to _repair the break, which was
complicated by the age of the pipe and conflicts with aFlorida Department of Transportation (FDOT)
storm - drain line. The location of the break was - directly above a crossing with a 24 inch diameter
storm drain line. 'The design of the force main had been altered during: construction (in 1937) due.to
this conflict. Working conditions were difficult because of the number and location of other;utilities
relative to the break and due to operational needs of the contributing communities. In ,order
insure - that residents. of all communities did not, lose sewer service, the City coordinated with the
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April 8, 2011
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County and several private hauling firms to. mobilize, a fleet of eleven (11) trucks which were
used to pump down pump station wet ' wells at wastewater pump stations in the satellite
communities.. Wastewater was hauled locations that allowed discharge into working portions of
the collection system for conveyance to the County Treatment Facility on Virginia Key. The pipe
repair had to be. performed in a wet (un- dewatered) trench, as -tidal ground water levels could not be
completely controlled , -and pumped wastewater from some of the satellite communities continued to
inundate the break site. Temporary repairs to the pipe were completed by 4:.00 PM on April 7,2011,
however during the process of .bringing the collection system back on line, a 36 inch diameter
isolation valve was found to be broken in a closed position, and a second break occurred on a 20'
inch diameter force main in the '72 "a Street Parking Lot. Both the damaged valve - and the second
main break were part of the same 74 year old underground infrastructure system.
For a second night in a row, Public Works and DMSI crews worked through the night to rebuild the
-failed isolation valve in place, and repair the second force main break. The isolation valve was re-
opened by -4:00 AM on Friday April 8th, and permanent repairs to the 20 inch.diameter force main
were completed by 5 :00 AM Our second attempt - to -place the repaired collection system into
service was successful' and as of 10:00 AM on April 8t normal operations in all communities with
the exception of - North Bay Village were restored. North Bay Village determined. that they have a
ruptured wastewater force main at a subaqueous crossing. North Bay Village will be making repairs
to their - system over the course of the day Friday (April 8 and they anticipate a return to normal
operations shortly - thereafter.
The repairs to the ruptured-force main are temporary because special fittings are required to restore
the damaged pipe to its original design condition. These fittings are special order (no longer
manufactured). 'Therefore, the Public Works Department is in the process of evaluating cost
effective alternatives to restoration of the line, which includes the options to bypass.the damaged
section of1orce main using directional drilling, line stops and wet taps or redesigning the original
force main alignment to deflect the line under the'existing FDOT storm drain that is in the way. Final
repairs to theforce main will take three (3) to four (4).weeks to design, permit and construct. In the
interim; - traffic flow will be restored through the intersection by restoration of the pavement where
- possible, and the use of steel, plating over the repair location (to facilitate easy access when the
permanent repairs are made). The intersection east to flow of traffic was reopened on Friday,
April 8 before rush and the north — south flow of traffic is anticipated to be restored by 8 :OOPM.
The City owns and maintains an ocean outfall line at. - 74 th Street that is permitted to accept raw.
wastewater for discharge. The- outfall may only be used in the case of emergencies and prior
permission must be obtained from the Florida Department of Environmental Protection (FDEP) and
DERM on a by case basis. 'The City is required to develop_an event specific discharge plan
certified by a Florida registered professional engineer, which includes a disinfection plan to partially
= treat any wastewater prior to discharge to the ocean. The ocean outfall is a disposal method of last
resort. Had it been necessary to. discharge raw wastewater through the outfall, it likely would have
resulted in the closing of many public beaches along South. Florida coastline for days or even
weeks. The resulting impact on the aquatic environment and the economic impact of .closing
beaches make this disposal option highly undesirable. 'The spill management plan developed by the
City for this incident included a provision to execute ocean discharge of wastewater. Fortunately,
through the effective management of the situation.and use of tanker trucks to haul wastewater,
City did not need to activate the emergency discharge plan.
In summary, a catastrophic failure of the City's 36 inch diameter main occurred - on April, 6,
'2011 at the intersection of Harding Avenue and 71St Street at approximately 10:30 AM. The City
effectively and efficiently developed a spill management plan and repair plan approved - by the
regulatory authorities that, are charged with such oversight. Through the combined efforts of City
and contracted forces the damaged wastewater force main and subsequent damage to the City's
wastewater collection system was repaired and the system was placed back in service by-1.0:00-AM
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April 8, .2011
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on Friday April 8, -2011. The City complied with all rules, laws and regulations governing this type of
incident.
`The .cause of the -pipe - failure. has yet to be determined; however damaged pipe section was
recovered and will be shipped to an engineering materials laboratory for analysis. The
information gained by this analysis will be incorporated into City's Capital Improvement
governing infrastructure replacement and renewal in an attempt to predict and proactively - address
potential weaknesses in the City's wastewater.collection system. The City had already engaged our
Consulting Civil Engineers, CDM with the task of performing a condition assessment of wastewater
force mains throughout the service area. The lessons learned from this event will assist in this
endeavor which will drive recommendations on future capital improvement priorities. Another lesson
learned` involves our relationship with our satellite communities 'The present collection system
configuration does not allow Public Works Operations to monitor via remote sensors the operations
of each contributing satellite communities' wastewater flow. We will seek to have supervisory
control systems installed in satellite community lift stations that will allow us to monitor individual
.flows from our Utilities Control Room.
The City recognizes and appreciates the close cooperation we received from the four communities
served.bythis portion of our collection system. Through the collective efforts of City staff regulatory .
authorities, and the close cooperation of contributory communities, a potential major negative
environmental situation averted, and a major wastewater transmission force main "was repaired
and returned to service in a timely manner. Costs for this operation have yet to be determined, but
the Commission will be apprised as soon as all costs are compiled and confirmed.
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