In a manhole when matching an 8-inch sewer line inlet with a larger line outlet, say 18-inch, do you match the pipe crowns or match the inverts (maybe with a 1/10' drop) or what?
I'm about to place concrete for helicopter parking pads. All was well until the client pointed out that the existing concrete directly under the copters was scaling off due to the petroleum by products (hydraulic oil, fuels, lubricants...) leaking from the copters. He wants to make sure this...
