Increase JVM heap size for Scala?

I have a Scala data processing tool which is failing with a java.lang.OutOfMemoryError exception. The tool needs to make a couple passes over a large data file (the one I'm working on is over 700MB), so it would be convenient if the entire thing could be stored in memory. I run the tool from the command line or from a Bash script using the "scala" runner. How do I increase the JVM heap size for th