White Oak Bayou Joint Powers Board WWTP - Executive Summary
WHITE OAK BAYOU JOINT POWERS BOARD |
WASTEWATER TREATMENT PLANT
SOURCE AND PROCESS DESCRIPTION: White Oak Bayou Joint Powers Board owns a Wastewater Treatment Plant (WWTP) located at 15201 Philippine Street. The design capacity for the WWTP is 3,200,000 gallons per day (gpd) average daily flow, and 12,800,000 gpd peak hydraulic flow. The influent that comes into the WWTP is subject to several treatment processes before it is discharged into White Oak Bayou. One of the last treatment processes is disinfecting the effluent just before it is discharged. Chlorine is used to disinfect the effluent. Because chlorine is used, the WWTP is responsible for submitting a Risk Management Plan (RMP) to the Environmental Protection Agency (EPA). EPA published 40 CFR 68 on June 20, 1996.
In this rule, there are 77 regulated toxic chemicals and 63 regulated flammables. All of these flammables and toxics have a certain threshold quantity. Chlorine, for instance, has a threshold quantity of 2,500 lbs. The WWTP has a maximum of 4,000 lbs. of chlorine on site under certain conditions. Chlorine is the only regulated toxic chemical at the WWTP with a higher amount than the threshold quantity than is allowed. The plant also keeps Sulfur Dioxide on site, but is under the threshold quantity.
SUMMARY OF MAJOR HAZARDS: Occupational Safety and Health Administration (OSHA) does not consider chlorine to be carcinogenic. Depending on how much chlorine is inhaled, effects could range from as little as a slight irritation to the eyes, skin, or lungs to possibly inhaling a large enough dose to prove fatal. If a vapor cloud is suspected, it is recommended that you immediately go indoors (do not try to outrun the cloud as you may be running directly in to it), turn off the air
conditioning system, and stuff wet towels in all cracks such as under doors and around windows. Wait for an all-clear before returning outside or call the Jersey Village Fire Department.
CONSEQUENCES OF FAILURE TO CONTROL THE HAZARDS: It is necessary to perform a worst case and alternative case scenario for a chlorine accident in order to submit a Risk Management Plan. For the worst case scenario, it is assumed that a one (1) ton cylinder has a leak such that its duration lasts for ten (10) minutes. A one (1) ton cylinder (2,000 lbs.) will have a release rate of 200 lbs. per minute for ten (10) minutes. This is actually a bit excessive since the rapid decrease in pressure in the vessel will tend to make any hole freeze over. EPA provides equations and tables specifically for the RMP to calculate the toxic endpoint of chlorine.
The toxic endpoint is simply the distance at which a human is not at risk from possible inhalation of the chemical. The toxic endpoint for chlorine
for a worst case scenario is 1.3 miles. As mentioned, an alternative case scenario is also required. This scenario assumes that a one (1) ton cylinder has been punctured and consequently has a =" hole in it. Once again, EPA provided tables and equations for this scenario. The toxic endpoint for chlorine for this scenario is 0.3 miles.
EXPLANATION OF HOW RELEASES ARE PREVENTED: Proper equipment and equipment handling are the most important items in preventing releases. This facility utilizes a state-of-the-art vacuum system which minimizes the possibilities of a major gas release. A leak in a vacuum line will stop the gas feed system so that the gas does not leak more than what is contained in the line. As a result of the vacuum system, the likelihood of a major leak is reduced to the point that it will only occur as a result of cylinder rupture or valve failure. A valve failure will result in a release, but most likely will seal itself temporarily due to the freezing gas
temperature caused by the rapid pressure loss in the cylinder.
Each of the operators who handle the chlorine feed equipment are trained in its proper use. This prevents many possible releases.
Another part of the release prevention is the siting of the equipment. When the present system was installed, it was relocated to the south side of the treatment plant so that the south facing walls of the concrete plant would act as a barrier in the case of a leak and would also help disperse the gas if it was a large enough leak to have gas reach the walls.
Releases are also prevented by good preventive maintenance (PM) practices. The White Oak Bayou Joint Powers Board (the "JPB") authorized quarterly PM for all of the gas feed equipment. The equipment manufacturers operating and maintenance manuals recommended semiannual PM. The JPB authorized quarterly PM as an extra precaution.
In addition to well maintained and selectively located equipment, the facility includes a comprehen
sive chlorine detection and alarm system. The system consists of low and high gas concentration detectors. The low concentration detector notifies the operator by an automatic alarm telephone dialer, who responds in the case of a minor gas leak. The high concentration detector sounds an audible alarm and the automatic alarm telephone dialer will call the fire department in addition to the operator.
During the period that the present equipment and PM programs have existed, there have been no major incidents. All systems have worked as designed and reviewed.
STEPS TAKEN TO ADDRESS HAZARDS: Recommendations are generated for improving operation and reducing risk on an ongoing basis. The contractor that performs the quarterly preventive maintenance is continually asked for recommendations to improve the safety of the installation. All employees are encouraged to attend training which includes safety reviews and newest trends in equipment operation. The facility engineer is call
ed in as needed to review the safety of the feed system along with the manufacturers representatives. The Jersey Village Fire Department has expressed its intent to become qualified to use a "Ton Cylinder Repair Kit" so that it will be better able to respond in cases of a cylinder problem. The chemical supplier also has an ongoing program of inspecting its cylinders for problems before they occur. Each cylinder is inspected prior to being refilled with gas.
RESPONSE ACTION IN THE EVENT OF A RELEASE: The Emergency Response Program is divided into two (2) types of incidents. The first is a low concentration leak of about 5.0 ppm of gas. Upon detection of this concentration of gas, the automatic alarm dialer is activated and calls a series of numbers to obtain a response by the operator. A representative of the operator responds and addresses the incident for a low concentration leak. Should the leak progressively get worse, the operator will call for assistance as warranted.
Otherwise the cylinder is turned off and the trained feed system technician is called in to make any necessary repairs.
A high concentration leak is one greater than 10.0 ppm at the gas detector. Upon detection of a high concentration leak, the audible alarm is activated and the automatic alarm dialer is activated and calls the numbers for the operator and the Jersey Village Fire Department. The fire department will immediately respond with trained personnel to assess the situation, turn the cylinder off if possible, or take other necessary actions including evacuating the area if necessary. The operator will also respond and assist the fire department as possible. The chemical supplier will be contacted for a response if the leak is from a cylinder.
For more information about responsive actions in the case of a major gas leak, visit the Fairbanks Branch, Harris County Library to view a copy of an emergency response plan. An emergency response plan has been developed especia
lly for this facility for the Risk Management Plan and has valuable information on what actions to take and important phone numbers.