The scala documentation clearly states that Float is a 32-bit floating point number (corresponding SQL type is float4) and Double is a 64-bit floating point number (corresponding SQL type is float8).

http://www.scala-lang.org/api/2.10.3/index.html#scala.Float
http://www.scala-lang.org/api/2.10.4/index.html#scala.Double

Corrected Float SQL type and added support for List[Double].
Added SBT project definition.