Town Creek Wastewater Treatment Plant - Executive Summary |
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Chemical safety is a very important issue to both management and employees of the City of Palestine. Generally, this is achieved through adequate training of employees, maintenance of facilities and process equipment, and provision of suitable safety equipment. City administration continually seeks to improve the safety measures that protect its employees and citizens alike. Town Creek Wastewater Treatment Plant treats all of the wastewater produced by the City of Palestine. The process is extended aeration consisting of an oxidation ditch followed by three (3) clarifiers, and two (2) chlorine contact chambers. The sludge is wasted to an aerobic digester and dewatered by centrifuge. The dewatered sludge is hauled to a local compost facility. Chlorine is the only regulated chemical used in quantities great enough to cause the plant to be subject to 40 CFR Part 68. Approximately eight thousand (8000) pounds of chlorine are generally stored at the plant. Two containers are conne cted to the chlorine feeding equipment at a time. OFFSITE CONSEQUENCE ANALYSES All of the offsite consequence analyses were conducted according to the methodologies and reference tables presented in EPA's Risk Management Program Guidance for Wastewater Treatment Plants (October, 1998). Population density information was taken from 1990 census data obtained through the Bureau of the Census website. Worst Case Scenario: The vessels used to store chlorine at the plant are one ton containers. Therefore, the worst case scenario involves the release of two thousand (2000) pounds of chlorine in ten minutes. The resulting release rate would be two hundred (200) pounds per minute. Because the plant is located in a forested area, the terrain is considered to be urban. The resulting distance to the toxic endpoint would be one and three tenths (1.3) miles. The area of concern covers approximately five and three tenths (5.3) square miles. The population density for approximately one an d two tenths (1.2) square miles of the area averages nine hundred (900) persons per square mile. The remaining four and one tenth (4.1) square miles contain approximately three hundred and ninety (390) persons per square mile. The total number of people estimated to be affected by a worst case release is twenty-seven hundred (2700). Public receptors within the area include residences, and a school. Alternative Scenario: The situation chosen as an alternative scenario is a release caused by a faulty gas valve. This is believed to be one of the most likely events to be encountered at this facility. Using the data in the guidance, the distance to the toxic endpoint would be two tenths (0.2) mile. The area of concern covers approximately thirteen hundredths (0.13) square mile. The population density for approximately eight hundredths (0.08) square mile of the area averages nine hundred (900) persons per square mile. The remaining five hundredths (0.05) square miles contain ap proximately three hundred and ninety (390) persons per square mile. The total number of people estimated to be affected by an alternative case release is ninety-two (92). The only public receptors within the area are residences. PREVENTION PROGRAM The most important element of prevention is training. The topics covered in the City's chemical safety training program include information on the properties of chlorine and the risks associated with its use. It will also cover safe operating practices. Equipment maintenance is another crucial aspect of preventing a chemical release. Employees will be taught the importance of keeping all chlorine process equipment in good working order, and trained in carrying out maintenance, inspections, and repairs according to the maintenance program established for the process. Another significant factor in preventing an accidental release of chlorine is the nature of the feeding apparatus. It is a vacuum system with the dripleg and regulator assembly connected directly to the container. This arrangement minimizes the possibility of an equipment failure in a part of the system in which the chlorine is under pressure. The regulator is designed to stop the flow of chlorine should a loss of vacuum occur. FIVE YEAR ACCIDENT HISTORY No releases that met the criteria for reporting have occurred within the last five years. EMERGENCY RESPONSE PROGRAM Should a release occur, the first priority will be to evacuate the site and surrounding area, as appropriate. The City Fire Department and Police Department will aid plant personnel in accomplishing this task. Any schools in the affected area will be among the first to be alerted. Door to door contacts will be made along with public announcements on local radio stations. The City has contracted with Garner Environmental Services, Inc., Ft. Worth, Texas to respond to any significant chemical release that may occur in the City. As soon as the notification and evacuation proc ess is underway, Garner Environmental will be notified to respond. PLANNED IMPROVEMENTS The most significant improvement planned in the area of chemical safety is more training for employees. A training program has been developed and a designated safety trainer to coordinate the program has been appointed. Operations and maintenance training will be also be increased. Money is being budgeted to purchase leak detection and alarm equipment. Other less expensive equipment such as labels and a windsock will be purchased shortly. |