Len, are you truckmount or a porty user?
I had a similar quote to this a couple of years ago and at the time i was wondering how to go about filling up water!

It wasn't practical to knock on peoples doors, The only way I thought was to hire a bowser and park it outside... but then how to i hight the water

Luckly I never had to worry about this problem as they thought my price was too high

I would work out a an hourly rate << including your expenses and then determine how long its going to take you to complete the job.
Tony