City of Pulaski Wastewater Treatment Plant - Executive Summary
Executive Summary |
The City of Pulaski operates and maintains a Wastewater Treatment Plant capable of treating an
average of 4 million gallons per day (MGD). The Wastewater Plant currently treats an average of
3.5 MGD and uses chlorine gas as a disinfectant in the treatment process. The City uses
approximately 60 pounds per day of chlorine. The Wastewater Treatment Plant utilizes ton chlorine
cylinders manifolded in pairs with a backup pair to provide the supply chlorine. Additionally, the
Plants stores up to two reserve non-connected cylinders to replace chlorine cylinders in service as
they are depleted. Typically no more than 12,000 pounds of chlorine will be on the site at any time.
The City of Pulaski Wastewater Treatment Plant has developed this Risk Management Program in
an attempt to identify all possible chemical emergencies which may occur and the best way to
prevent the accidental release of chlorine to the atmosphe
re from the plant's chlorination facilities.
The City Personnel responsible for the daily maintenance and operation of the chlorination
equipment conduct their work with the upmost professionalism and have a deep respect of the
dangers involved with chlorine. The City places chlorine safety ahead of all other matters.
In addition to the Risk Management Plan, the City of Pulaski is subject to OSHA Process Safety
Management (PSM) regulations. The City is working with Tennessee OSHA to develop and
implement an approved PSM plan for chlorine. This has been coordinated with the Giles County
Local Emergency Planning Committee and the City of Pulaski Safety Board to assure that all entities
are aware of the possible dangers involved in a chlorine leak from the Wastewater Treatment Plant.
The City has developed a written operations manual, emergency response plan and emergency action
plan as a part of the OSHA PSM plan. As a part of the written operations manual, City personnel
conduct their work with the chlorine equipment at a safe pace and double check all
connections when changing tanks or adjusting the system. Additional safety measures are installed
in the form of ventilators and chlorine leak detectors which assist in the notification and protection
of emergency personnel in the event of a leak. Since the Wastewater Treatment Plant is only
manned 8 hours a day, the City of Pulaski has incorporated an autodialer into the chlorine alarm
system to notify personnel of leaks which occur after hours.
The emergency response plan outlines the proper procedures to follow in the event of a chlorine leak
detection. Upon detection of the leak, the plant supervisor will notify the emergency service
coordinator as defined in the City of Pulaski's Emergency Operations Plan to coordinate assistance
with outside emergency units. The cause of the leak will then be determined so that appropriate
actions may be taken to insure public safety. The City of Pulaski Fi
re Department will act as
standby rescue personnel for the plant operators while an attempt to stop the chlorine leak is made.
The fire department personnel will be familiarized with the chlorine system so as to assure that, if
necessary, they may be able to isolate the leak and stop it. The Emergency Service Coordinator will
work with the Pulaski Police Department and other personnel to alert nearby residents to remove to
safety if the need arises. Local radio stations may also be utilized to notify the public of the
emergency condition and what to do. To date, the City of Pulaski has had no major accidental
releases of chlorine which required action involving off-site receptors. There have been no
accidental releases of chlorine in the last five years.
The Worst Case Scenario for the Risk Management Plan was evaluated as a rupture of a full ton
chlorine cylinder and release of its contents to the atmosphere. The most probable alternative release
scenario has been determined to
be a cracked and leaking supply line. The EPA supplied
RMPCOMP program was used to evaluate the area of effect for these releases. Using this program,
it has been determined that both scenarios will have some offsite impact. The worst case scenario
has an area of effect of 0.9 miles in radius and the alternate scenario has an area of effect of 0.1 miles
in radius. The worst case scenario could possibly affect approximately 3,700 people and public
receptors involved include schools, hospitals, major commercial areas, churches and residences
depending on the wind direction. The alternate scenario could possibly affect 200 people with public
receptors involving residences and churches. The mitigation devices utilized in the alternative
scenario include enclosure of the chlorine facilities and chlorine detection devices which will
minimize the amount of the chlorine lost prior to detection and repair.
The City of Pulaski is still reviewing its PSM plan to define required modificati
ons and additions
to improve safety. A training session will be conducted at the end of the PSM review to inform plant
personnel of the proper methods for reporting accidents and proper operational methods to minimize
the chance of accidental release of chlorine. Additionally the City is reviewing addition of a
windsock to determine the wind direction in case of an emergency.
Prevention Program Summary
The Wastewater Treatment Plant utilizes ton chlorine cylinders manifolded
in pairs with a backup pair to provide the supply chlorine. Additionally,
the Plants stores up to two reserve non-connected cylinders to replace
chlorine cylinders in service as they are depleted. Typically no more than
12,000 pounds of chlorine are on the site at any time.
The City Personnel responsible for the daily maintenance and operation of
the chlorination equipment conduct their work with the upmost professionalism
and have a deep respec
t of the dangers involved with chlorine. The City
places chlorine safety ahead of all other matters. The City has developed
a written operations manual, emergency response plan and emergency action
plan and conducted a Process Hazard Analysis as a part of the OSHA Process
Safety Management plan (PSM).
The Process Hazard Analysis determined that the major hazards identified were
a toxic release of chlorine either from a cylinder rupture or pipe leak and
failure of equipment to control the chlorine flow or detect a chlorine leak.
The major natural hazard would occur from touchdown of a tornado on the plant
facilities. These hazards are mitigated through process controls in the
form of vents, relief valves, check valves, manual shutoffs, excess flow
devices, interlocks and alarm systems along with passive enclosure of the
facilities, regular maintenance of the equipment and proper training of the
personnel using the equipment.
The City has developed a written operations manual to ass
ist personnel in
learning the proper procedures involved in unloading, moving, connecting
and testing the chlorine cylinders used at the plant. City personnel always
conduct their work with the chlorine equipment at a safe pace and double
check all connections when changing tanks or adjusting the system. The
plant chief operator conducts competency test through physical observation
of the work being conducted.
Plant personnel regularly check the chlorine system for defects and perform
preventative maintenance. The major area requiring maintenance in the
chlorine system is the pigtail pipe connecting the chlorine cylinder to the
manifold. This pipe is inspected each time a new cylinder is connected and
replaced if defects are found. Also, these pipes are replaced every six
months even if no defects are seen on the pipe as preventative maintenance.
In the event that a tornado has been sited in the immediate vicinity of the
Wastewater Plant, the plant operator will at a minimum atte
mpt to valve off
all chlorine cylinders on-site before seeking shelter. If the tornado touches
down on the plant premises, the operator will perform a thorough inspection
of the chlorine system to determine damage and possible dangers before
attempting to place the system back online. If the chlorine storage facility
has been destroyed by the tornado, the plant operator will determine if any
of the chlorine cylinders have been damaged enough to leak and verify that
none were blown offsite by the tornado. Any leaks will be brought under
control and the damaged tank removed. If a tank is unaccounted for, the
operator will activate the emergency response system and alert emergency
personnel to being locating the cylinder and determine its condition.
The City of Pulaski feels that these safe guards adequately protect the
safety of the plant personnel and the general public from the dangers of
a chlorine leak from the wastewater plant facility.