Midland Water Treatment Plant - Executive Summary
CITY OF MIDLAND, MICHIGAN- WATER TREATMENT PLANT |
THE FACILITY AND THE REGULATED SUBSTANCES HANDLED-
The Midland Water Treatment Plant is a municipally owned and operated treatment plant for producing a public water supply for use by the city's citizens and industry. The raw water source is from the Saginaw-Midland Municipal Water Supply Corporation, a jointly owned municipal authority with the City of Saginaw, Michigan.
The raw water is taken from Lake Huron by the authority at its Whitestone Pumping Facility, near AuGres, Michigan. The only treatment given the water at the Whitestone facility prior to pumping the water to the two cities is the addition of chlorine. The purpose of the chlorination is for disinfection of bacteria, controlling tastes and odors, and controlling fouling of the pumps and pipelines. The initial chlorination point is at the Whitestone Pumping Facility.
Upon arrival of the chlorinated raw water at the Midland Water Plant, it undergoes conventional c
hemical and physical water treatment processes to make it into a safe and desirable public water supply. Additional chlorine must be added at the Midland Water Treatment Plant to ensure the water meets drinking water quality standards as delivered to the consumers. The maximum inventory of liquid chlorine at the water plant is 8 one-ton containers.
The Midland Water Plant is located on the east side of Midland approximately 1 1/2 miles inside the city limits. Midland has a population of 38, 053. Its major industry is the Dow Chemical Company. The water plant operates continuously with total of 12 full time operator, maintenance, laboratory, clerical and supervisory staff.
FIVE-YEAR ACCIDENT HISTORY-
The Midland Water Plant has operated continuously for more than fifty years without a serious chemical release incident. The facility has had no reportable off-site toxic chemical releases in the past five years.
THE GENERAL ACCIDENTAL RELEASE PROGRAM AND CHEMICAL-SPECIFIC PRE
The Midland Water Plant has had an ongoing safety program in compliance with the Process Safety Management (PSM) regulations of OSHA. A consultant was engaged to assist the water plant's limited staff with the implementation of the RMProgram. The Risk Management Program guidance manual published by the American Water Works Association Research Foundation was used as a primary reference. Other informational materials and manuals from USEPA supplemented it. The water plant management determined that the chlorination process came under Program 3 of the regulation.
A six person RMP Team was formed to help implement the RMProgram. The Team consisted of the facility's most experienced and knowledgeable staff in the chlorination process. Included were a senior operator, a maintenance representative, the maintenance supervisor, and the operations supervisor. The other Team members were the water superintendent and the consultant.
A mission statement was developed and di
stributed at the first RMP Team meeting, along with a description of the objectives and goals of the team and an organization chart showing RMP responsibilities. The Team met at varying intervals over a three-month period between April 1999 to June 1999. Minutes were kept of the Team meetings by the water superintendent and are a part of the water plant's RMP records.
The same team was used to conduct the Process Hazard Analysis (PHA) portion of the Risk Management program.
THE ACCIDENTAL RELEASE PREVENTION AND EMERGENCY RESPONSE POLICIES-
Fourteen new RMP policies, which were recommended in the AWWA guidance manual as model policies, were adopted to implement the RMProgram.
As part of the Hazard Assessment requirement in the RMP regulation, an Off-site Consequence Analysis (OCA) was conducted using the RMP*Comp software, Version 1.06. Population estimates were made for the Worst Case and the Alternate Case using the LandView III software.
As part of the water plant's Preve
ntion Program, a new Process Hazard Analysis (PHA) was conducted in accordance with the policies, new Operating Procedures (OPs) and Maintenance Procedures (MPs) were developed and adopted, and the facility's Emergency Action Plan (EAP) was revised and updated.
A WORST CASE SCENARIO-
The RMP regulation requires the facility to investigate an assumed situation in which the entire contents of a full chlorine container are released over a ten-minute period. For the Midland Water Plant this scenario would be a one ton container releasing its contents of 2000 pounds of chlorine in ten minutes inside of the chlorine storage building. The computer analysis showed the gas would be diluted to below a level-of-concern beyond a distance of 0.9 miles from the release point. It is estimated that approximately 4,100 persons might be located within the circle of a 0.9-mile radius of the release point for the WORST CASE situation.
AN ALTERNATE CASE SCENARIO-
Since the situation described abo
ve as the Worst Case is not likely to ever happen, the regulation provides for an alternate scenario to be reported, which would be more likely to occur. The regulation requires that the alternate scenario selected must result in a chemical release extending beyond the facility property boundaries.
The alternate case selected, which was the most likely to happen and result in an off-site incident, was the rupture of the 1/4-inch ID flexible connecting tubing carrying chlorine gas between a one-ton storage cylinder and the header piping. This scenario would have a level-of-concern endpoint 0.1 miles from the release point. It is estimated that approximately 91 persons might be located within the circle of a 0.1-mile radius from the release point for the ALTERNATE CASE.
THE EMERGENCY RESPONSE PROGRAM-
The water plant facility is unable to provide adequate Emergency Response from the limited plant staff.
The City of Midland is a participant in a county wide, one-plan program fo
r dealing with hazardous materials. The first response for a chlorine release at the Midland Water Plant would be from the City of Midland Fire Department. The Midland Fire Department personnel have the training and equipment to respond and safely shut down or contain a chlorine release. The response time is less than ten minutes under most conditions. Response is initiated by a telephone call to the Central Dispatch operator (911). The water plant also has direct contact with the fire department via radio.
An on-site Emergency Action Plan (EAP) has been adopted and implemented which provides for facility staff to be sheltered in place in the main water plant building, which is a separate building from the chlorination storage building. The plan includes the necessary emergency notification and contact numbers. It also includes emergency first-aid information. The (EAP) provides that local responders will provide public notification and reporting.. A citywide siren warnin
g system can be operated by the Central Dispatch operator to aid in notification of the public in a chemical release emergency.
The Midland Fire and Police Department representatives regularly attend meetings with the Local Emergency Planning Committee to help coordinate community local response for notification and evacuation.
PLANNED CHANGES TO IMPROVE SAFETY-
1. Increased Unit Heater Maintenance-
Unit heaters can be a source of water leaks from dripping valve packing and piping connections. Such leaks add humidity and moisture and therefore have the potential of increasing corrosion in the chlorine storage building. An increase in the level of preventative maintenance on the unit heater in the chlorine storage building has been implemented.
2. Chlorine Leak Alarm Light-
A rotating beacon light is being installed outside of the entrance doors to the chlorine storage building to alert employees of a chlorine leak before entering the building.
3. Replacement of Chlorine
A regularly scheduled replacement of all chlorine process piping and valves is planned. The replacement interval will be based on the recommendations of the Chlorine Institute.
SAFETY IMPROVEMENTS PRESENTLY UNDER EVALUATION-
1. Teflon Gaskets-
The current standard lead gasket or washer used in chlorine piping connections is a frequent source of small chlorine leaks. The problem is that the lead flows under pressure and with time the connection loosens and sometimes leaks. Teflon gaskets in place of lead for container connections are currently being considered.
2. Automatic Shut-Off Valves-
Presently, in the event of a process-piping leak, valves at the chlorine storage containers must be closed manually by turning a handle located outside of the chlorine storage building. Automatic shut-off valves, which would close when a chlorine detector alarms, are being considered.
3. New Chlorine Leak Detectors-
The existing chlorine leak detectors were installed i
n 1981. They have consistently shown that they are reliable and in calibration. Due strictly to the age of the present units, the replacement of the detector units or the addition of back-up units is being considered.