Seeking comments for using develop, establish in the paragraph

I would like to seek someone’s comments on the following sentences.

a. which is the best of the following sentences?

b. May someone advise me of a good sentence to suit the paragraph if all sentences are not good?

1. In my engineering experience, I ensured building service systems of buildings under my management complying with all statutory requirements and laws.

Additionally, by developing my contract specification, contractors had conformed to the obligations of environmental code.

1. In my engineering experience, I ensured building service systems of buildings under my management complying with all statutory requirements and laws.

Additionally, by establishing my contract specifications, contractors had conformed to the obligations of environmental code.

1. In my engineering experience, I ensured building service systems of buildings under my management complying with all statutory requirements and laws.

Additionally, being established by my contract specification, contractors had conformed to the obligations of environmental code.