Final answer:
The commonly accepted minimum depth for burying gas lines below a commercial parking lot is 18 inches, based on standards like the National Fuel Gas Code. Local building codes may vary and should always be checked as they take precedence over general standards.
Step-by-step explanation:
The minimum distance gas piping is allowed to be buried below a commercial parking lot can vary based on local codes and regulations. However, a commonly accepted minimum depth for burying gas lines under a parking lot or similar areas where vehicular traffic is anticipated is 18 inches. It provides protection from potential damage due to surface activities. For example, the National Fuel Gas Code published by the National Fire Protection Association (NFPA 54) often serves as a basis for local regulations and unless modified by local authorities, the 18-inch depth is a typical requirement. Yet, local building codes should always be checked as they take precedence and can have different requirements.