can I ask a quick question ..
Is this a plastic pipe .. or an iron pipe ??
If this is a metal pipe the Electric Water Pipe Thawing Machine will do what you need to do. These apply a voltage to any metal pipe and will heat the entire length of the pipe. Your local rental store will have these to rent. If the weather is very cold these may be hard to locate since all can be out on rentals. There are many different types of these machines available. A longer pipe will take longer to heat. Since these machines must be connected to both ends of the pipe you would need at least 350 ft of the welding type cable these machines use. I have seen a portable electric welder used to thaw the pipes but extreme care must be used since, if the pipe is heated to fast it can cause the pipe to actually explode due to the steam building up inside. I do not recommend a electric welder be used. Many times the actual problem is in the pipe that is not buried. These pipes can be heated with various types of heaters to thaw them. I have included several links below with other information on the topic.
THAWING THERMOPLASTIC WATER PIPES
THE ICEBREAKER 350
Preventing and Thawing Frozen Pipes
Should you require further clarification, never hesitate to ask.