UPPER EAST SIDE – There’s a new problem slowing down progress on the Second Avenue subway: water. MTA construction crews are encountering “gushing” underground streams, which is delaying digging, according to MTA Capital Construction President Dr. Michael Horodniceanu. Crews dig an average of 34 feet of rock per day, sometimes hitting a high of 60 feet per day. “If we were in the business of mining for water, we’d be much better,” said Horodniceanu.