@ossobuco,
I designed whole housing tract fine drainage many times, working closely with the site engineers (batches of plan changes, into late night changes - we worked well together on the tuning), and once in a while overriding someone re the general drainage - redid a whole tract once (a famous situation to me where my answer re the site grading worked best over the primo engr firm, acknowledged by that firm and saved a lot of money on top of that. I will say it was probably a junior person at that firm that did the first plan, and that firms we usually worked with were sharper or had someone watching the pups. I did lose a full night's sleep over it and then some).
Also worked out some highway drainage that the engineers copied. But, braggart that I am, I'm a dolt now and I don't just say listen to me. But check it out. Stare at how your streets go and think about it.