I'm sorry to have only discovered your post today!
A little to late i know!
The hard part of the job that you stated would have been nozzle selection. There are plenty of different nozzles available that would have helped you with the job. Several are self proppeled and could have simply been used to clean the 100' sections individually. No point in going into technical detail now, but if you need advice in the future feel free to contact me.
Cheers
Scott
Waterjet Industry