City council whom I emailed requesting drawings and sizes of the arc, answered that the arc is not their responsibility, only the eastern part of the drive up to the arc.
So, I got a ton of drawings from them, all about stuff I'm not interested in... well, apart from the first pilar, though that's a big one to build.
So, sent a mail to the 'Rijkswaterstaat' (governemental stuff) and they replied and informed me what they had, asked if that would help... So I replied 'Yes, please' ... now waiting for the stuff...
Still making progress... bit concerning though, that I am building it, while still unsure about correct height of it.... oh well... there's always hope!