Excavation Safety and Utility Strike Near Property Line
You are excavating for a foundation on a tight urban lot in Tempe, Arizona. The excavation is 8 ft deep and 20 ft long, running parallel to a property line. The adjacent property has a 6-ft-high masonry fence located 3 ft from the property line. The soil is sandy silt with some cobbles. The geotechnical report classifies it as Type B soil. You have a competent person on site. The excavation will be open for 3 days. On the first day, the crew encounters an unmarked 2-in. plastic gas line running perpendicular to the excavation at a depth of 4 ft. The gas line is not on the as-built drawings. The utility company is called and says they will respond within 4 hours. The crew wants to continue digging on either side of the line to stay on schedule. The project is in Maricopa County, which requires call 811 before digging and has specific rules for excavation near utilities. OSHA requires that utilities be located and protected before excavation.
1. What are the immediate safety and regulatory actions required upon discovering the unmarked gas line?
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Safety: Stop all excavation within 5 ft of the gas line. The gas line is hazardous; any damage could cause a leak, fire, or explosion. Evacuate the immediate area and notify the utility. Do not allow any equipment to operate near the line. The competent person must inspect the excavation and ensure it is safe. The crew should not attempt to move or support the line.
Regulatory: You must notify the utility (already done) and wait for their response. The call 811 center should be contacted again to report the discrepancy. OSHA requires that utilities be located by the utility owner or a qualified locator before excavation. Since the line was not marked, you must treat it as active and wait for the utility to mark and confirm. Maricopa County requires that you not proceed until the utility has located the line. Failure to comply can result in fines and criminal charges if an accident occurs.
2. How should you proceed with the excavation and protect the adjacent property?
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Excavation near gas line: After the utility marks the line, you may proceed with hand digging within 2 ft of the line to expose it. The line must be supported and protected from damage. If the line is in the way, the utility may need to relocate it, which could delay the project. You should document the condition and notify the owner for a potential change order.
Adjacent property: The excavation is 8 ft deep and 3 ft from the property line. The adjacent fence is 6 ft high and may be undermined. The soil is Type B, and the excavation must be sloped or shored. OSHA requires that excavations be protected from cave-ins. The fence may need temporary support or removal. You should notify the adjacent property owner and document the condition. Consider using a trench shield or shoring to protect the excavation and the fence. Also, check if the excavation affects the stability of any structures on the adjacent property. A pre-construction survey is advisable. If the fence is damaged, you may be liable. The competent person should inspect daily and after rain.