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The operation and maintenance of the water distribution system includes upkeep of the pipes, storage tanks and pumps that convey water from the water treatment location to the customers. Activities that are part of operation and maintenance include the following:
· Cross connection control and backflow prevention
· Water pipe flushing
· Water main repair/replacement
· Storage tank maintenance
· Pump maintenance.
These activities have aspects that can potentially impact the environment and are regulated under U.S. environmental regulations as summarized below:
· ActivitIes potentially regulated under RCRA:
- Pump maintenance
- Storage tank maintainance
· Activities potentially regulated under the CAA:
- Storage tank maintenance
· Activities potentially regulated under the CWA:
- Water pipe flushing
- Water main repair/replacement
· Activities potentially regulated under EPCRA:
- Water pipe flushing
- Water main repair/replacement.
Cross Connection Control and Backflow Prevention
Cross connection control and backflow prevention are operational programs which a public water system and its customers must implement to prevent contaminants and non-potable water (e.g. wastewater, storm water, process water) from being drawn into their drinking water system. Cross connections are physical, piped connections between potable water and an unsafe, or polluted water source. Cross connections can threaten water quality and public health through the backflow of such hazardous substances as antifreeze, boiler water, and sewage. Backflow is a reverse flow of water from the customer or service connection into the water distribution system. Backflow typically occurs when distribution system pressure drops due to a water main break or due to fire fighting demands. Cross connection control programs consist of building codes and other regulations which prohibit cross connections and require backflow prevention devices on particularly high risk service connections (e.g., a wastewater treatment plant). Education, inspection and enforcement are also necessary to ensure compliance with the building codes and regulations.
Water Pipe Flushing
Water pipe flushing is performed on distribution systems to remove any accumulated sediments or other impurities which have been deposited in the pipe. Water pipe flushing also improves the flow of water through the distribution system, allowing it to work at capacity. Flushing is performed by isolating sections of the distribution system and opening flushing valves or more commonly fire hydrants to cause a large volume of flow to pass through the isolated pipeline and suspend the settled sediment. Water mains may also be mechanically cleaned through the use of swabs or pigs which are devices that are pulled through a section of line that scrape the accumulated debris off the inside of the pipe. The major environmental aspect of water pipe flushing is the discharge of flushed water, which may be high in suspended solids and other contaminants that can harm water bodies. The negative impacts of the discharge may be minimized by discharging the flush water into a sanitary sewer with adequate capacity or by discharging the flush water into a separate storm sewer system with storm water management measures such as a detention pond, where solids can settle before the water is discharged. Discharge of water from flushing may be regulated under the NPDES permit.
Water Main Repair/Replacement
Water main repair/replacement must be performed to water systems to replace or repair broken, corroded, or leaking sections of pipe. The broken pipe section is either replaced or as is often the case, a repair sleeve is placed around the outside of the broken pipe section and clamped into place. Following the repair of the pipe, the line is typically flushed and then disinfected with a chlorine solution. The chlorine solution is usually mixed on site with powdered calcium hypochlorite or sodium hypochlorite. Pipe repair and replacement has the potential to impact the environment through:
· Erosion and sedimentation which take place as a result of excavation, stockpiling, and backfilling
· Discharge of sediment laden water in the excavated area from groundwater and rainfall
· Discharge of sediment laden flush water and highly chlorinated disinfecting solution.
These impacts can be minimized through control measures. Sediment and erosion control measures that can be implemented for the excavation of the trench include stockpiling the excavated soil on the uphill side of the trench or installing silt fence on the downhill side of the excavation. The impacts associated with discharges from trench dewatering, pipe flushing and pipe disinfecting can be reduced by discharging into storm water management facilities such as detention ponds where solids can settle and chlorine compounds can dissolve. Discharge of water from these activities may be regulated by the facility's NPDES permit, while storage and use of chlorine may be regulated under EPCRA or the CAA.
Storage Tank Maintenance
This activity requires frequent inspection and may require occasional repairs. The most frequent types of repairs are repainting of the tanks and replacing screens over vents and other points of access to insects, birds and rodents. Most tanks are made of steel and therefore subject to corrosion. To prevent corrosion, the tanks are painted on a regular basis. The negative environmental aspects of painting the tanks are the generation of sandblasting residue which results from preparing the tank's surface for receiving paint. The measures which may be implemented to minimize this impact include containing the area to be sandblasted, collecting and recycling the sandblasting residue. Sandblasting activities may be regulated under the SIP developed under the CAA, while disposal of paint chips and dust, if they are determined to be hazardous, may be regulated under RCRA.
Pump Maintenance
Pump maintenance must be performed by a water system to ensure booster and other distribution system pumps stay in working order. Maintenance of the pumps involves checking the pumps regularly for excessive vibration or noise, providing grease and lubrication regularly and checking the pumps bearings and packing glands. Use and storage of the necessary petroleum-based grease and lubricants have the potential to impact the environment through spills to water or land. Disposal of these products may be regulated under the RCRA used oil regulations. Spills of oil that reach waterways are required to be reported under EPCRA or the CAA.
Safe Drinking Water Act Compliance
Local governments are responsible for complying with federal SDWA regulations, both for water treatment and the distribution system. As part of those regulations, water supply facilities are required to sample and analyze the water for specific chemicals to ensure they do not exceed the maximum contaminant levels (MCLs) for those chemicals. If, and when, MCLs are exceeded, local governments must notify the state within 48 hours. In addition, local governments are required to provide public notice of the exceedance. Finally, all local government water supply facilities must maintain records, including bacteriological and chemical analyses, actions taken to correct violations, sanitary surveys of the system, and variances or exemptions granted to the system.
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