PRASA, North Coast Superaqueduct Project - Executive Summary |
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The North Coast Superaqueduct project is an integrated water treatment and distribution system. It consists of raw water abstraction, storage and pumping to a water treatment plant where potable water is produced. The treated water up to 75MGD will flows by gravity through a transmission pipeline of approximately 50 kms serving municipalities along the north coast of Puerto Rico and the metropolitan area of San Juan. The water treatment plant is situated in the town of Arecibo in the Miraflores ward. The project will be owned by the Puerto Rico Aqueduct and Sewer Authority (PRASA). It is being constructed and will be operated by the Thames-Dick partnership as a build, operate and takeover (BOT) scheme. Thames Water Puerto Rico, Inc. will be responsible for day to day operation. Thames Water Puerto Rico, Inc. is a wholly owned subsidiary of Thames Water PLC. Thames Water PLC is a United Kingdom based utility company. It has over 11 million customers and operates almost 100 water treatme nt plants in the UK. Its global interests extend to the operation of water and wastewater facilities serving another 11 million customers. It also owns companies which manufacture products or provide services to the water, wastewater and environmental sectors around the world. Chlorine is used at the water treatment plant for the disinfection of the treated water supply. Chlorine will be delivered to site on a purpose built road transporter ( contained in 1 ton drums). The unloading, loading and handling of drums will only be done using a purpose designed fixed crane and lifting beam. The supplier has been selected after a tendering procedure which included a review of safety management and operating systems. The chlorine installation is designed so that all chlorine storage, handling and use is carried out in a well defined single, segregated building. The building is designed to meet local building codes including earthquake protection. The unloading bay and storage area are set bac k from any site road traffic and fully enclosed by an open sided concrete structure fitted with full height steel mesh panels. The chlorine scale and chlorinator rooms are adjacent and fully enclosed concrete structures. Access to all areas is through normally locked doors and the area is also protected by a closed circuit TV security system. All access doors are fitted with strobe light and horn alarms and warning signs. The drum store has purpose built trunnion storage cradles for thirty eight drums. The area has fixed chlorine leak detectors at the perimeter of the store. The chlorine scale room has trunnions for four drums arranged as pairs either side of a change over switch. Initially only one drum will be installed on each bank pending installation of a captured key valve to control manual drum selection and a dry air pipe purge system. Each drum will be connected to the pipe system using flexible aluminum pipes (pigtails). The pipe system is designed to be compact and arranged to prevent accidental mechanical damage from drum lifting operations. It is fitted with pressure switches, bursting discs and expansion bottles to protect against overpressurization and release to the atmosphere. Each drum will be fitted with automatic drum valve shutdown devices connected to the chlorine leak detection system and remote manual emergency switches. The chlorine scale room is fitted with a floor level ventilation system which continuously purges the atmosphere within the room. In the event of a leak being detected by the permanently installed floor level chlorine sensors, this will shut and the ventilation louvers will close to contain the leak inside the room. The chlorine will be drawn from the drum as liquid and passed through one of two thermostatically controlled and protected water bath evaporators. The gas will pass through pressure regulators and vacuum regulators before passing into the chlorinator room next door. The chlorinators room is also ventilated and fi tted with a leak detection system. The operation of the chlorination system including alarms will be monitored continuously by the site wide SCADA system. This can be viewed at any of the five area control panels or the centralised site control room. In the event of an emergency there are windsocks and assembly points at strategic positions and a site wide audible alarm system. Other equipment available for use by operators and maintenance staff for routine and /or emergency use include four (will be six) Self Contained Breathing Apparatus sets with fouteen air cylinders, dedicated air compressor, five portable electronic multi gas detectors, two Chlorine Institute set B drum repair kits, mobile telephones and site radios, two oxygen resuscitation kits, class A and B chemical hazard respond suits. Sufficient equipment for emergency response will always be identified and available to allow a responseto any emergency within ten minutes. The plant will be manned continously. At night and weekends a team of three operators will be on shift. During normal working hours, up to nine operators and maintenance staff will be on site. All normal, routine operations including delivery, drum handling, connections and disconnections wil be done during normal working weekdays. All operators and select maintenance staff will receive training in all aspects of chlorine operation. This will include the following Thames Water courses of: Self Contained Breathing Apparatus, Confined Spaces, Lifting equipment and its use, Hazardous substances, Right to Know, Disinfection process safety, Gas control, safety shutdown and leakage control, Emergency Response Plans, Permits to work (Lockout - Tagout), Disinfection process theory and operation including drum changing, Process Operation Control and Standard Operating Procedures. These courses will be suppoted by The Chlorine Institude literature, videos and additional chlorine vendor training. The courses include classroom as well as extensive practical demonstrations, practise and testing. The Thames Water training has been delivered and competency assessed by experienced United Kingdom based dedicated trainers and assessors. A system of refresher training practise and assessment is also in place. The company has a comprehensive written health and safety program which includes corporate health and safety policies and identifies the organisation and management of health and safety within Thames Water Puerto Rico, Inc. This includes the appointment of a safety Inspector who will coordinate the function of health and safety and chair the company safety committee. Written procedures to cover all aspects of routine and emergency operation of the chlorine installation will be in place. Training, testing, audit and review of these will be carried out on a regular basis. An emergency response plan in compliance with OSHA and EPA guidelines has been produced and implemented. Coordination with the Civil Defense, Police Department, Fire Department, Medical and Environmental services and authorities is in process. The design and operating systems have been subject to Structure What If Technique (SWIFT) review and to American Water Works Association Emergency Response Plan checklist for chlorine installations. |