Water main and sewer installation involves several hazards that require careful risk assessment and control measures. These hazards can be broadly categorized into excavation hazards, atmospheric hazards, confined space hazards, and material handling hazards.

Excavation Hazards:

• Cave-ins: Excavations can collapse, especially if the soil is unstable or if the excavation is not properly sloped or supported [1]. Implement shoring, sloping, or trench boxes to prevent cave-ins. Ensure a competent person inspects the excavation daily and after any changes in conditions [2].
• Underground Utilities: Striking underground utilities such as gas, electric, or communication lines can result in electrocution, explosions, or service disruptions [3]. Before excavation, determine the estimated location of utility installations [3]. Use safe and acceptable means to determine the exact location of the installations [3]. Protect, support, or remove underground installations as necessary to safeguard employees [3].
• Water Accumulation: Accumulated water in excavations can create instability and pose drowning hazards [2]. Implement water removal equipment and monitor its operation by a competent person [2]. Use diversion ditches, dikes, or other suitable means to prevent surface water from entering the excavation and to provide adequate drainage of the area adjacent to the excavation [2].
• Access and Egress: Inadequate access and egress can delay emergency escape [4]. Provide a stairway, ladder, ramp, or other safe means of egress in trench excavations that are 4 feet (1.22 m) or more in depth so as to require no more than 25 feet (7.62 m) of lateral travel for employees [4].

Atmospheric Hazards:

• Oxygen Deficiency and Hazardous Atmospheres: Excavations, especially in landfill areas or near hazardous substance storage, may contain hazardous atmospheres or be oxygen deficient [4]. Test the atmosphere in the excavation before employees enter excavations greater than 4 feet (1.22 m) in depth [4]. Provide proper respiratory protection or ventilation [2]. Emergency rescue equipment, such as breathing apparatus, a safety harness and line, or a basket stretcher, shall be readily available where hazardous atmospheric conditions exist [2].
• Flammable Gases: Sewers may contain flammable gases or vapors 6, 14. Test the atmosphere in said sewer at the place or places of entry by use of apparatus to detect the presence of any flammable gas or vapor [5]. Adequately ventilate and made safe from the hazards of fire and explosion [5].

Confined Space Hazards:

• Confined Space Entry: Sewers and manholes can be considered confined spaces, posing risks of toxic gas exposure, oxygen deficiency, and engulfment [6]. The internal atmosphere shall be tested for combustible gas and, except when continuous forced ventilation is provided, the atmosphere shall also be tested for oxygen deficiency [6].

Material Handling Hazards:

• Falling Loads: Employees can be struck by falling loads or spillage from lifting or digging equipment [4]. No employee shall be permitted underneath loads handled by lifting or digging equipment [4]. Employees shall be required to stand away from any vehicle being loaded or unloaded to avoid being struck by any spillage or falling materials [4].

Additional Considerations:

• Personal Protective Equipment (PPE): Ensure workers wear appropriate PPE, including hard hats, safety glasses, and high-visibility clothing [4].
• Traffic Control: Implement traffic control measures to protect workers from vehicular traffic [4]. Employees exposed to public vehicular traffic shall be provided with, and shall wear, warning vests or other suitable garments marked with or made of reflectorized or high-visibility material [4].
• Piping Materials and Installation: Use appropriate piping materials and installation techniques to prevent leaks and failures 3, 4, 9, 17. Install and maintain distribution lines in a safe operating condition 4, 9, 17. Protect piping against physical damage 4, 9, 17. Make allowances for piping expansion, contraction, jarring and vibration 4, 9, 17.

Monitoring and Review:

• Regularly monitor the excavation site for any changes in conditions that could affect safety.
• Review the risk assessment and control measures periodically and update them as necessary.
• Ensure all workers are trained on the identified hazards and the implemented control measures.