Water Pollution Control Plant - Executive Summary
RMP Executive Summary |
The City of Dubuque Water Pollution Control Plant is a publicly owned and operated wastewater treatment facility that serves the citizens and industries of Dubuque Iowa. The plant is located in a valley near the Mississippi River. The primary activity at this site is the treatment of wastewater. The Water Pollution Control Plant (WPCP) uses chlorine in 2000-pound cylinders for the seasonal disinfection of wastewater and magnesium bisulfite solution for dechlorination prior to discharge. Magnesium bisulfite is not listed as a chemical of concern under RMP. The plant has 19 employees and is staffed 24hrs per day 365 days a year. Chlorine is used on a seasonal basis to disinfect treated wastewater. The amount of chlorine on site is between 6000 and 12000 pounds during the chlorination season and up to 2000 pounds off-season. 150 to 300 pounds per day of chlorine gas are used during routine operation.
1. Prevention and Release Policies Summary - The prevention
of a release is provided for by the following steps.
a. All aspects of handling chlorine are limited to a small number of employees trained in the handling and operation of 2000-pound chlorine cylinders and associated chlorinating equipment.
b. In addition all employees receive chlorine safety awareness training each year.
c. The changing of chlorine tanks is limited to daytime working hours Monday through Friday when management supervision is available.
d. Chlorine use is scheduled to allow for weekend and holiday chorination without the need to change or add additional tanks of chlorine. In the unlikely case that additional chlorine would be needed a supervisor and a trained employee would be called in to perform the task as needed.
e. Prior to the start of the chlorinating season the mechanical integrity of all lines and fittings is verified. Valves, yokes, pigtail lines, and controls are checked and replaced as needed.
f. Chlorine is taken from the cylinder as a gas only by
orienting the tank so that the valves are in a vertical position and then using the top valve for gas only use. Valves and pigtails are arranged so that using the top gas valve is the only possible choice without reorienting the valve position. Using gas only during normal operation limits the potential release of chlorine if there should be a valve or piping failure.
g. Leak detection is provided for in the chlorine storage area and the chlorination control room. The leak detection devices are connected into the plant wide SCADA system for monitoring purposes and a local audible alarm. SCADA will also provide an onscreen alarm and an audible alarm throughout the entire plant in addition to the local audible alarm.
h. In the event of a release employees of the WPCP have been trained in response procedures for communicating with the Dubuque Fire Department and HAZMAT team. This communication would include information relating to severity of the leak, current weather conditions, number
of employees on site, and the location of employees. WPCP employees will also notify our only neighbor of the occurrence of a release so that precautions may take place at their facility.
i. Management of the WPCP is very aware of the possible dangers associated with the use of chlorine and takes an active role in the day to day handling and use of chlorine. The record of over twenty years without an accidental release testifies to this commitment.
2. Release scenarios - the Water Pollution Control Plant (WPCP) is located in a valley close to the Mississippi River. The nearest resident is at least .4 miles away and at an elevation of approximately 80 feet above the level of the plant, any schools or hospitals are at least 120 feet above plant elevation. Do to these facts we feel confident in using the building enclosure as a mitigating factor to limit the worst case toxic endpoint distance for the release of chlorine. RMP Comp was used for the worst case, EPA lookup tables for the
alternative case. Landview III was used to determine receptors. For the worst case scenario the population densities from Landview III were used. Population densities for the alternative case was determined by local knowledge, there are no residents within the alternative case radius.
Worst Case - The worst case would be the release of 200 pounds per minute of chlorine for a duration of ten minutes giving a total release of 2000 pounds. The release would be inside a structure limiting the release rate to 110 pounds per and the toxic endpoint to 0.9 miles. RMP Comp was used to determine the toxic endpoint. The receptors identified were residents, an industrial area, a state park, a wildlife refuge and a hospital (nursing home). Landview III was used to determine population densities.
Alternative Case - The alternative case is the release of 15 pounds per minute of gaseous chlorine from a pipe leak for 60 minutes resulting in the release of 900 pounds. The scenario selected repres
ents the most likely release from a 2000-pound cylinder using gas only. This type of leak could come from a failure in the pigtail, a crimped lead washer or a leaking packing in the chlorine valve. The toxic endpoint was determined using lookup tables in the 'Risk Management Program Guidance for Wastewater Treatment Plants' by the USEPA. The toxic endpoint is 0.1 miles. The receptors are a state park and an industrial area. There are no residents within the 0.1 mile radius of the toxic endpoint.
3. Compliance - The Dubuque WPCP is in compliance with OSHA PSM and USEPA RMP
4. Accidental Releases - There have been no accidental releases of chlorine at this location for over twenty years.
5. Emergency Response - Emergency response has been coordinated with the Dubuque County LEPC, City of Dubuque Fire Department and HAZMAT team. WPCP employees have been trained in response procedures for communicating with the Dubuque Fire Department and HAZMAT team. A WPCP staff person is a me
mber of the LEPC and a resource person for the HAZMAT team.
6. Program Changes - The WPCP will continue to look for ways to limit the use of chlorine for treatment purposes. No program changes are foreseen in the near future.