The footing design is as shown, 5.5′ deep and 2×2′. It was hard to dig the hole that deep without making the hole wider, so it was made 2′ 6″ (30″) wide.
A post hole digger was used to loosten the soil and when the hole got too deep a bucket was used to hoist the soil to the top of the hole to dump in a pile.
the rebar was made per the drawing and inserted in the hole with the help of a “come along” hoist. The bottom most rebar was supported by concrete blocks made for that purpose.
Below is the specification for the baseplate design and welding requirements. Below that is the Bill of Material (BOM) for the Steel Tubes and their specifications.
The structural design primarly depends on the environment that the tower is exposed to, wind, seizmic, and soil conditions
The spec coversheet specifies that the wind velocity could be as much as 110mph!