How to estimate I2C bus capacitance?
TI's application report Effect of Parasitic Capacitance in Op Amp Circuits says:


  Circuit traces on a PCB with a ground and power plane will be about 1−3 pF/in.


100 in ≈ 2.5 m



If you still have doubts about the rise times, consider using an I²C accelerator like the LTC1694, or a buffer like the TCA9803.