I posted this in another location, but thought it might get better exposure here. I need to locate some large metal tanks which may be as much as seven feet underground. If anyone has a White TM 808 or other detector that would work I would like to talk to you. I would be interested in hiring your services, renting the detector or whatever other ideas you might have. The property is near Joshua Tree National Park. Thanks
up to 7 ft. underground, for a tank, is an easy feat for a 2-box unit. Especially if the location is riddled with nuisance little stuff, the 2-box will see past that, and only get the larger item you're looking for. I'll float an inquiry on the kinzli CA forum for you, and see if anyone knows of a rental or hire service for you. Will have them PM you with the info.
Another thought is to simply contact any dealer near Joshua Trees (Riverside area? etc...) and ask them if they have a contact with any customers who they know have one. Because dealers (not catalogs, but actual brick & mortar dealers) tend to know the local hobbyists in their area, who has what toy (d/t perhaps they've sold them one in the past). And they might refer you to a hobbyist in the area who has one. And that person could loan or rent his, or hire out his services, etc....
Seven feet deep seems somewhat excessive from what I have seen with underground tanks. I used to inspect them when they were installed. Depending on size, fuel tanks rarely have more than three of cover. It costs money to get them real deep. You did not say what the tanks were used for but if they were for fuel storage, there should be fill and vent pipes visible nearby or directly above the tank. If they were for some other purpose, then I don't know.