Colton Water Reclamation Facility - Executive Summary |
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The City of Colton Water Reclamation Facility (WRF) is located at 1201 South Rancho Ave. in Colton CA. The facility contact is William F. Roth, Wastewater Utilities Manager. The WRF is a wastewater treatment plant that performs preliminary, primary and secondary treatment. Preliminary treatment consists of grit chambers to remove heavy debris and bar screens to remove sticks, rags and other large debris. Primary treatment uses settling to remove floatable and settleable solids. Secondary treatment follows primary treatment and uses biological processes to remove approximately 90 percent of the oxygen demanding substances and suspended solids that remain after primary treatment. The rated capacity of the WRF is 6.4 million gallons per day (mgd). A 2 mgd expansion is underway. The facility treats domestic, commercial and industrial wastes generated within the cities of Grand Terrace and Colton and some unincorporated areas of San Bernardino County. The treatment steps consist of screeni ng and grit removal, followed by primary clarification, biological oxidization and secondary clarification. Sludge treatment consists of dissolved air floatation, primary and secondary anaerobic digestion, aerobic digestion and dewatering. The sludge is disposed of by direct land application. Currently, the WRF discharges up to 5.3 mgd of secondary treated municipal wastewater to the Rapid Infiltration-Extraction (RIX) Facility where it is further treated by filtration and ultraviolet disinfection. The WRF uses chlorine for disinfection to control filamentous bacteria in the activated sludge process and to control algae growth in the WRF wash water system. There have been no significant releases of chlorine in the lifetime of the plant and no reportable chlorine injuries to workers in over five years. The maximum amount of chlorine on-site at any time is four one-ton containers. The chlorine in the containers is liquefied and under pressure. The maximum amount of chlorine on-line at any time is one-ton. Up to three additional one-ton containers are kept in storage in a horizontal position. The WRF is regulated by the OSHA Process Safety Management program for worker safety and by the California Accidental Release (CalARP)/EPA Risk Management Program (RMP) for off-site impacts. In preparation for the CalARP/RMP, the WRF conducted a hazard analysis of all chlorine systems and updated all elements of the PSM program The EPA Off Site Analysis (OCA) Guidance Document was used to define the worst case. The worst case assumed that all the chlorine in a one-ton container would be released outside as a gas in ten minutes at low wind speed and very stable atmospheric conditions. The EPA RMPComp model was used to estimate the distance to the chlorine endpoint. The endpoint distance is the distance required for the chlorine concentration to dilute down to a level that would not have serious impact on an average person if exposed to the concentration for up to an hour. The en dpoint distance for one-ton of chlorine was estimated to be three miles away from the plant in any direction. Rupture of a tank is highly unlikely. The tanks are of approximately one-half inch thick steel construction and weight about 1600 pounds when empty. They are not easily ruptured. Colton has established procedures for safe unloading of containers, for transferring containers within the chlorine storage building by an overhead crane and for safe connection and disconnection of containers to prevent chlorine releases. When in position, the containers are prevented from rolling by trunions and are tied down with chains. The storage room is equipped with a chlorine leak detector that produces an audio alarm, flashes a beacon and automatically dials up a beeper system if a leak is detected. The alternative release scenario, assumed that the flexible tubing, which connects the container with the chlorine piping, ruptured and released gas inside the chlorine storage room for 30 minut es before it could be shut down. As previously, the EPA RMPComp model was used to estimate the distance to the chlorine endpoint. The endpoint distance for the ruptured tubing was estimated to be one-tenth of a mile away from the plant in any direction. The WRF has established an Emergency Response Program for the facility which relies on the Colton Fire Department to respond to all releases except minor leaks that can be controlled by the WRF staff. Colton has established procedures to make all on-site workers and contractors aware of the potential dangers and how to respond in case of an emergency. The WRF intends to conduct an Emergency Response drill at least once per year. Public notification in case of a release with potential off-site impact will be handled by the Colton Fire Department and the Colton Police. Based on the hazard review conducted for the WRF, the WRF will be upgrading the chlorine detection system. A major portion of the current chlorine system is designed to s hut down automatically if there is a break in the low pressure side of the piping. The high pressure side is not protected from a rupture. Colton will be upgrading the chlorine system to automatically shut down the high and low pressure sides of the system in case of a chlorine leak. Both upgrades will be in place by June of 2000. |