Don’t forget to get your underground pipes installation verified by the surveyor as far as the grades before closing it up. Most cases these will run from manhole to manhole so if you had your manholes right it will be okay but this can really ruin your project if down the road you discover that you didn’t have enough slope etc…site drawings can change often during the course of the cjob, which can also affect the grades and elevations. It is very important to keep track of these changes and at all times you need to make sure that your sitework subcontractor is following the latest drawings. (like in any other trade, but for him not fo9llowing will be really really costly for him and your project overall)