Games : Why would I be getting TPS lag spikes every 30 seconds on a single player local client world?

I am using the AtLauncher with a modded Thaumcraft based world and keep getting a lag spike every 30 seconds that basically stops the world and it rushes to catch up. Turing on the Lagometer it shows it as TICK lag which I don't get since I am playing local on my machine not on a server.

Does anyone know a setting that might cause this?