City of Ukiah Water Treatment Plant - Executive Summary
1. Accidental release prevention and emergency response policies |
The City of Ukiah uses chlorine gas to disinfect the potable water it produces for the
protection of this community and to meet state health codes and EPA guidelines for the
protection of the distribution system.
Being aware of this, the city has prepared an extensive training program, in both safety
and first aid, for those employees that have to manage and handle chlorine. They also
demanded certain safety equipment to be considered and implemented in the construction
of the water treatment plant.
They have educated the police and fire departments about emergency procedures in case
of an accidental release. These procedures further protect the community which we serve
and in which we live.
2. The stationary source and regulated substances handled
The primary purpose of the City of Ukiah, Public Utilities Department's, Water
is to provide to the community an adequate, safe, and healthy supply of water. The
primary source of water to the community comes from the water treatment located
behind the men's softball fields east of highway 101. The treatment plant receives chlorine
in one ton containers that are approved for use by the Chlorine Institute. These
containers have been inspected and hydrostatically tested before shipment and visually
inspected again upon receipt at the plant. These cylinders contain liquid chlorine under
The properties of chlorine that make it an effective disinfectant against the microbes that
are present in our source water also makes it dangerous to humans in higher
concentrations. Chlorine is a greenish-yellow gas that is two an one-half times heavier
than air, has a pungent odor, and is toxic to humans above 10 ppm (parts per million). It
will increase in volume from liquid to gas app
roximately 460 times. When it combines
with moisture it creates both hydrochloric acid, HCl, and hypochlorous acid, HOCl, both
of these chemicals are corrosive and can cause severe respiratory and ocular damage.
The chlorine storage area is a secure area within the plant grounds and the total maximum
amount at the plant is 4000 pounds.
3. The worst case scenario and alternative release scenario
The worst case scenario that has been developed for the City of Ukiah water treatment
plant uses the premise that there are no safety factors involved. It is assumed that the
wind is blowing at 4.5 mph and that the temperature is 77E. The scenario further states
that all 2000 pounds of one container would convert from liquid to gas and disperse within
ten minutes from within an enclosed room. The results of this model determine that the
chlorine gas would have to travel 1.3 miles in the direction of the wind in order to be
reduced to 3 ppm. Depending on the wind direction this would affect all of Ukiah proper
going as far south as Talmage Rd. and as far north as Ackerman Cr. The cemetery to the west and to the east dispersion would be limited by the foothills. This, again depending on the
direction of the wind, would involve all of the schools, all hospitals, juvenile hall, all
commercial and industrial sites, all parks, all day care centers, and all residences down
wind from the treatment plant.
The alternative release scenario takes into account that there are safety features designed
into the plant and the fact that the most likely leak that may occur would release less than
twenty-one ponds per minute for less than fifteen minutes.
The system in use at the treatment plant is a pressure/vacuum system and the pressure
portion involves the cylinder, valve, and less than four inches from the chlorine cylinder to
a vacuum regulato
r. The vacuum side is approximately seven feet and is controlled by the
vacuum regulator. This means that if a vacuum is not being applied the vacuum regulator
is closed and there is no gas flow. If the vacuum regulator were to fail the vacuum side of
the system would then be pressurized and the flow would be equivalent to the degree of
failure. The plant has installed, two chlorine gas detectors that have battery backup.
These detectors are set to alarm at 1-3 ppm. When they alarm several items automatically
come into play. The first is the chlorine scrubber which is a chemical neutralization
process specifically for chlorine. This draws the heavy gas into a tank engineered to mix
the chlorine gas with the contents. Thus no gas will escape to the atmosphere. The
second item that happens simultaneously with the first is an audible and visual alarm
indication and the water supply to the injectors is closed. The third item is t
hat after one
minute our phone system automatically calls the City of Ukiah dispatch center and they in
turn dispatch first the fire department and then the necessary plant personnel to investigate
the cause of the alarm. The fourth item is the computer at the plant will shut down the
plant and eliminate any further draw of chlorine other than the leak.
With all of these factors involved during a minute leak, the incident and any effect will be
isolated to the enclosed space and there will be no off site impact.
At well 5 there aren=t any safety factors currently in place except for the fact it is in an enclosed room. With a twenty-one pound per minute release the duration with a 150 pound cylinder would be just over seven minutes long. With no alarms the entire contents would be lost. The release would be minimal and would cover approximately one-tenth of a mile, and would not affect any residences, recreatio
n areas, commercial or industrial sites, schools, hospitals, or day care centers.
At well 2, like well 5, there are no safety factors on site and with the same release scenario there would be approximately twenty-four people involved because of the proximity of the softball fields.
4. The general accidental release prevention program and the specific prevention steps
The City of Ukiah water treatment plant is actively involved in several regulatory
mandates when it comes to handling and using chlorine gas. These are OSHA Reg 29
CFR 1910.38, EPA CFR 40, OSHA PSM, STATE HEALTH and SAFETY CODE
2735, and the STATE EPCRA.
The OSHA Reg CFR 1910.38 Emergency Action Plan sets specific guidelines on training
in safety and maintenance prior to an emergency and if an emergency might occur.
The OSHA PSM (process safety management) covers nearly identical features.
The State Health and Safety Code 2735
covers air quality.
The State EPCRA is the Emergency Planning Community Right-to-know Act and sets
guidelines for the notification of the community in the event of a release above a pre-
The EPA CFR 40 is the Federal Clean Air Act.
The city is acutely aware of the importance of safety meetings, safety training,
maintenance training for its employees, and the community's right to know about the
situations which could cause impairment or death. As such we at the treatment plant are
even more aware because the water which we deliver to the community has to be healthy
and the products we use to achieve this can also cause illness if not handled carefully and
if the safety parameters are not kept under close scrutiny. As water treatment specialist
we receive many technical publications and journals that outline changes in procedure and
new products on the market for enhancing our water or for monito
ring the process. We
also occasionally receive product updates on the equipment already installed and material
used in our process. Safety and technology are a part of our day-to-day operation.
We also use the manufacture's Operation and Maintenance manuals as a reference as to
the regularity of maintenance of the equipment we use. This equipment is also installed
using the Chlorine Institute as an authority for material and products.
Part of our maintenance on the scrubber includes running the system weekly and checking
the pressure readings and daily checking the seal pressure and noting the liquid level in
Part of our maintenance on the chlorine system is to daily inspect the system and when
there is no demand, to check the pressure and vacuum sides for leaks.
Personal safety items that we have on hand and maintain include chemical exposure suits,
hard hats with face shields, safety showers,
self contained breathing apparatus, and a
Chlorine Institute type "B" chlorine repair kit.
Our training is usually conducted by a certified instructor.
5. The five-year accident history
Because of the knowledge, training, and responsible attitude of the employees and the
commitment of the management to be accident free when it comes to chlorine, there have
been no releases, accidental or otherwise, for greater than five years.
6. The emergency response program
See EAP.TXT attachment.
7. Planned changes to improve safety
The treatment plant personnel, after reviewing our recent process hazard analysis, have
determined that the following items should be changed:
A windsock should be installed to assist emergency personnel in determining the direction
of the most severely affected areas in case of an accidental release.
Indicator lights should be installed on the alarm panel t
o further designate which part of
the process, pressure or vacuum is in alarm.
Move a gas vent closer to within the proximity of the gas detector.
Install a tie down system for the cylinder in storage. The cylinder in use is already in the
tie down status.
Possibly install automatic louvers in the scrubber line to prevent back draft.