Thief River Falls Water Treatment Plant - Executive Summary
EXECUTIVE SUMMARY |
The Thief River Falls Water Treatment Plant Risk
Management Plan was developed to protect both the
residents of the community and Water Department personnel
through policy and procedures governing the operation of
the facility. This plan is a cooperative effort of plant
staff, administration, and City Government. It is based
on the requirements of OSHA Process Safety Management,
USEPA Risk Management, and Minnesota's Workplace Accident
and Incident Reduction (AWAIR) law requirement.
The commitment of the City of Thief River Falls City
Council is demonstrated by the Thief River Falls Employee
Safety Committee. This is an independent committee
reporting directly to the City Council. It includes
supervisory, department head, union personal and two City
Council members who take an active role in addressing
safety issues and concerns for all City employees.
RELEASE PREVENTION AND EMERGENCY RESPONSE POLICIES
The Thief River Falls Water Treat
ment Plant uses
gaseous chlorine and anhydrous ammonia for disinfection of
the drinking water supplied to the community. The
anhydrous ammonia inventory is maintained below the
minimum quantities as required by OSHA PSM and EPA RMP
requirements. Maximum quantity is 560 pounds.
The WTP Chlorine inventory control procedure calls for
the chlorine inventory to be maintained between 500 and
3000 pounds, using cylinders of one ton capacity. When
the on-line chlorine cylinder is reduced to approximately
1000 pounds, another cylinder is ordered. The replacement
cylinder is delivered before the on-line cylinder reaches
500 pounds. This procedure limits the amount of chlorine
on site to a maximum of one full cylinder and one partial
cylinder. The purpose of this policy is to maintain an
adequate inventory of chlorine for disinfection while
limiting WTP operator and public exposure to a accidental
Worst-case and alternative relea
se scenarios have been
determined after careful review of the regulation and
consideration of the storage vessel configuration. No
active mitigation measures or devices, such as scrubbers,
could be considered for analysis of worst-case releases.
For this worst-case scenario, the regulation specifies
the release conditions and meteorological conditions at
the time of the release. When these conditions were
modeled, using the USEPA Off Site Consequence Analysis,
the results were as follows:
Worst-case release scenario:
* Quantity released = 2000 pounds
* Release duration = 10 minutes
* Release rate = 200 pounds per minute
* Distance to endpoint = 2.2 miles
For the alternative release scenario, the following
results were obtained:
* Quantity release = 317 pounds
* Release duration = 60 minutes
* Release rate = 10.6 pounds per minute
* Distance to end point = leaking gas contained in
rage room. No off
RELEASE PREVENTION PROGRAM FOR COVERED CHEMICALS:
The Thief River Falls PSM/RMP and AWAIR prevention
programs include the following sections:
* Employee participation
* Process safety information
* Operating procedures
* Personnel training
* Contractor safety
* Prestartup safety review
* Preventative maintenance/mechanical integrity
* Hot work permits
* Management of change
* Incident investigation
* Compliance audits
The first line of defense against an accidental
chlorine release is the WTP Preventative Maintenance
Program. This is a mechanical integrity program requiring
annual inspection of all hazardous chemical equipment.
Certain equipment components require monthly inspections.
The schedule is based on and adjusted according to actual
inspection and test results. Components such as gas
pressure regulators, feeder master control units
, and auto
switch-over valves are tested and calibrated on a test
bench that simulates the actual operation of the systems.
New replacement components are tested in this manner
before installation or placement in inventory. The spare
parts inventory in maintained with all components
necessary to repair any equipment failure. In addition,
the chemical feed process equipment has redundancy to
provide back-up equipment operation while problem
equipment is in repair or inspection.
There have been no reportable release incidents in the
history of the Thief River Falls Water Treatment Plant.
Response to a leak is by plant personnel trained in
mitigation of chlorine leaks, using self contained
breathing apparatus, personal protection equipment, and a
chlorine Emergency Kit "B" system.
Evacuation of surrounding population, and back up
safety personnel for the plant operators, is provided by
the Thief River Falls Fire Depa
rtment and local Law
Enforcement Center officers.
A leak in the chlorine system, as signaled by either
of two chlorine detectors, triggers the start up of the
chlorine scrubber system and triggers the WTP alarm
system. This provides notification to the plant operator
to implement the Water Treatment Plant Emergency Response
The chlorine storage room is designed to contain a
chlorine leak in the room while the scrubber neutralizes
the gas or liquid release. The scrubber is designed to
neutralize 2000 pounds of chlorine as either a liquid,
gas, or both.
PLANNED CHANGES TO IMPROVE SAFETY
Employee input on improved safety and operations is
encouraged and requested as a matter of City Policy.
Training of WTP staff is conducted in-house, and at
seminars and workshops sponsored by the Minnesota Section
of the American Water Works Association, Minnesota Rural
Water Association, and the Minnesota Department of Health.
These seminars also provide a netwo
rking vehicle for the
sharing of information and innovations on the operations
and safety procedures in the water works industry.
Frequent training seminars are used as a tool to keep all
safety issues on the minds of WTP staff.
The full plan is available for review at the office of
the Thief River Falls Water Superintendent.